MULTI-JURISDICTIONAL
HAZARD MITIGATION PLAN
2021-2026
Merced County Multi-Jurisdictional Hazard Mitigation Plan Table of Contents
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TABLE OF CONTENTS
1 Introduction ....................................................................................................................................................................... 1-1
1.1 Purpose of Plan ................................................................................................................................................ 1-1
1.2 State and Local Regulatory Framework ................................................................................................. 1-1
1.3 Background and Scope ................................................................................................................................. 1-1
1.4 Multi-Jurisdictional Planning ...................................................................................................................... 1-3
1.5 Plan Organization............................................................................................................................................ 1-3 2 Community Profile and Capability Assessment ................................................................................................... 2-1
2.1 History ................................................................................................................................................................. 2-1
2.2 Geography and Climate ................................................................................................................................ 2-3
2.3 Economy ............................................................................................................................................................. 2-3
2.4 Population .......................................................................................................................................................... 2-4
2.5 County’s Mitigation Capabilities ............................................................................................................... 2-5
2.5.1 Regulatory Mitigation Capabilities .......................................................................................... 2-6
2.5.2 Administrative and Technical Mitigation Capabilities...................................................... 2-9
2.5.3 Fiscal Mitigation Capabilities .................................................................................................. 2-11
2.5.4 Other Mitigation Programs and Partnerships .................................................................. 2-11
2.5.5 Opportunities for Enhancement ............................................................................................ 2-12 3 Planning Process .............................................................................................................................................................. 3-1
3.1 Background on Mitigation Planning in Merced County .................................................................. 3-1
3.2 What’s New in the Plan Update ................................................................................................................ 3-1
3.2.1 Plan Section Review and Analysis – 2021 Update ............................................................. 3-2
3.3 Multi-Jurisdictional Participation .............................................................................................................. 3-4
3.4 Planning Process ............................................................................................................................................. 3-5
3.4.1 Phase 1: Organize Resources ..................................................................................................... 3-6
3.4.2 Planning Step 3: Coordinate with Other Departments and Agencies .................... 3-12
3.4.3 Phase 2: Assess Risks.................................................................................................................. 3-15
3.4.4 Phase 3: Develop the Mitigation Plan ................................................................................. 3-16
3.4.5 Phase 4: Implement the Plan and Monitor Progress ..................................................... 3-16 4 Hazard Identification and Risk Assessment........................................................................................................... 4-1
4.1 Hazard Identification ..................................................................................................................................... 4-2
4.1.1 Overall Hazard Significance Summary ................................................................................... 4-3
4.1.2 Non-Profiled Hazards ................................................................................................................... 4-4
4.1.3 Disaster Declaration History ....................................................................................................... 4-5
4.1.4 Climate Change Considerations Summary ........................................................................... 4-6
4.1.5 Overview of Hazard Identification and Risk Assessment ................................................ 4-7 Asset Summary ................................................................................................................................................................. 4-8
4.1.6 Assets Exposure............................................................................................................................... 4-8
4.2 Hazard Analysis and Risk Summary ...................................................................................................... 4-21
4.2.1 Dam Incidents ............................................................................................................................... 4-21
4.2.2 Drought ........................................................................................................................................... 4-35
4.2.3 Earthquake ..................................................................................................................................... 4-47
4.2.4 Flood & Levee Failure ................................................................................................................ 4-67
4.2.5 Landslide ......................................................................................................................................... 4-87
4.2.6 Severe Weather: General .......................................................................................................... 4-93
4.2.7 Severe Weather: Extreme Temperatures: Freeze and Extreme Heat ....................... 4-94
4.2.8 Severe Weather: Dense Fog .................................................................................................. 4-101 Merced County Multi-Jurisdictional Hazard Mitigation Plan Table of Contents
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4.2.9 Severe Weather: Heavy Rain ................................................................................................. 4-106
4.2.10 Severe Weather: High Wind/Tornado ............................................................................... 4-115
4.2.11 Subsidence ................................................................................................................................... 4-127
4.2.12 Wildfire .......................................................................................................................................... 4-133
4.2.13 Hazardous Materials Incidents ............................................................................................. 4-151
4.2.14 Cyber Attack ................................................................................................................................ 4-160
4.2.15 Agricultural Pests and Disease ............................................................................................. 4-165
4.2.16 Pandemics/Epidemics .............................................................................................................. 4-171 5 Mitigation Strategy ......................................................................................................................................................... 5-1
5.1 Mitigation Goals and Objectives ............................................................................................................... 5-1
5.1.1 Continued Compliance with the National Flood Insurance Program (NFIP) .......... 5-3
5.2 Identification and Analysis of Mitigation Actions .............................................................................. 5-4
5.2.1 Prioritization Process ..................................................................................................................... 5-5
5.3 Mitigation Strategy Action Plan ................................................................................................................ 5-7
5.3.1 Progress on Previous Mitigation Actions .............................................................................. 5-7
5.3.2 Updated Action Plan ..................................................................................................................... 5-8 6 Plan Adoption, Implementation, and Maintenance ........................................................................................... 6-1
6.1 Adoption ............................................................................................................................................................. 6-1
6.2 Implementation ............................................................................................................................................... 6-1
6.2.1 Role of the Hazard Mitigation Planning Team in Implementation and Maintenance ..................................................................................................................................................... 6-2
6.3 Maintenance ..................................................................................................................................................... 6-2
6.3.1 Maintenance Schedule ................................................................................................................. 6-2
6.3.2 Maintenance and Evaluation Process ..................................................................................... 6-3
6.3.3 Incorporation into Existing Planning Mechanisms ............................................................ 6-4
6.3.4 Continued Public Involvement .................................................................................................. 6-5 7 Plan Adoption ................................................................................................................................................................... 7-1
7.1 Element E.1 Formal Adoption Documentation.................................................................................... 7-1 8 References .......................................................................................................................................................................... 8-1
LIST OF APPENDICES
Appendix A: Planning Team
Appendix B: Planning Process Documentation
Appendix C: Approval and Adoption
Appendix D: Mitigation Categories and Alternatives
Appendix E: Annual Progress Meeting Agenda and Report Template Appendix F: Outreach Strategy
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Merced County Multi-Jurisdictional Hazard Mitigation Plan Introduction
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1 INTRODUCTION
1.1 Purpose of Plan
Merced County including the participating jurisdictions of the have prepared this multi-jurisdictional hazard mitigation plan (MJHMP) to guide hazard mitigation planning to better protect the people and property of the County from the effects of hazard events. This plan demonstrates the community’s commitment to reducing risks from hazards and serves as a tool to help decision makers direct mitigation activities and resources. This plan was also developed to make Merced County and the participating jurisdictions eligible for certain federal disaster assistance, specifically, the Federal Emergency Management Agency’s (FEMA) Hazard Mitigation Assistance (HMA) grants including the Hazard Mitigation Grant Program (HMGP), Flood Mitigation Assistance (FMA) and Building resilient Infrastructure and Communities program, as well as to make the County and jurisdictions more disaster resistant. This plan demonstrates the County’s commitment to reducing risks from hazards and serves as a tool to help decision makers direct mitigation activities and resources.
1.2 State and Local Regulatory Framework
The MJHMP was prepared consistent with the Health and Safety Element of the Merced County General Plan, as the planning effort covers common overlapping natural hazard issues and mutually reinforcing policies and implementation programs. The MJHMP and Health and Safety Element are considered complimentary documents that address natural hazards, and both planning documents contain goals, policies, and project actions or implementation programs to enhance the County’s mitigation efforts related to public safety.
California Government Code Section 65302.10, also referred to as Assembly Bill (AB) 2140 encourages California counties and cities to adopt their current, FEMA-approved LHMPs into the Safety Element of their General Plan. This adoption by reference or incorporation of the MJHMP into the Safety Element of the General Plan follows plan approval and makes Merced County and each participating jurisdiction eligible to be considered for part or all of its local share costs on eligible public assistance funding to be provided by the state through the California Disaster Assistance Act (CDAA). The CDAA allows the state to pay up to 18.75 percent of the non-federal share that would otherwise fall upon the county or city to pay for public assistance projects. The legislature passed AB 2140 to provide additional funding after a disaster occurs. The local share is 25 percent of the total project cost; therefore, the legislation allows city and counties that comply to be eligible for only the remaining local share (6.25 percent).
AB 2140 is an optional state incentive to help counties and cities become more resilient to natural hazards. Compliance with AB 2140 also expires when the MJHMP expires, and the County must re-adopt the plan into the Safety Element during update cycles to ensure continued compliance and funding eligibility. Additionally, each participating jurisdiction in Merced County must adopt their annex into their own General Plan Safety Element, as the annex jurisdictions are not covered under the County’s General Plan Safety Element adoption.
1.3 Background and Scope
Each year in the United States, disasters take the lives of hundreds of people and injure thousands more.
Nationwide, taxpayers pay billions of dollars annually to help communities, organizations, businesses, and individuals recover from disasters. These monies only partially reflect the true cost of disasters, because Merced County Multi-Jurisdictional Hazard Mitigation Plan Introduction
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additional expenses to insurance companies and nongovernmental organizations are not reimbursed by tax dollars. Many disasters are predictable, and much of the damage caused by these events can be alleviated or even eliminated.
Hazard mitigation is defined by FEMA as “any sustained action taken to reduce or eliminate long-term risk to human life and property from a hazard event.” The results of a three-year, congressionally mandated independent study to assess future savings from mitigation activities provides evidence that mitigation activities are highly cost-effective. On average, each dollar spent on mitigation saves society an average of $6 in avoided future losses in addition to saving lives and preventing injuries (Natural Hazard Mitigation Saves: 2017 Interim Report).
Hazard mitigation planning is the process through which hazards that threaten communities are identified; likely impacts are determined, prioritized and implemented. This plan continues the hazard mitigation planning process for Merced County, the unincorporated county, and the participating cities of Atwater, Dos Palos, Gustine, Livingston, Los Banos, and Merced. The plan identifies natural and human caused hazards and risks within Merced County, and identifies the hazard mitigation strategy to reduce vulnerability and make the communities of Merced County more disaster resistant and sustainable.
Information in this plan can be used to help guide and coordinate mitigation activities and local land use decisions. Proactive mitigation planning will help reduce the cost of disaster response and recovery to the community and its property owners by protecting critical community facilities, reducing liability exposure, and minimizing overall community impacts and disruption. The Merced County planning area has been affected by hazards in the past and is thus committed to reducing future disaster impacts and maintaining eligibility for federal funding.
This plan underwent a comprehensive update in 2021 in fulfillment of the five-year update requirement.
Several factors underscore the need for this planning effort:
Ɣ Merced County is exposed to hazards that have caused past damage.
Ɣ Limited local resources make it difficult to be pre-emptive in reducing risk. Eligibility for federal financial assistance is paramount to promote successful hazard mitigation in the area.
Ɣ Merced County and its partners participating in this plan want to be proactive in preparing for the probable impacts of natural hazards.
This MJHMP was originally prepared in 2014, pursuant to the requirements of the Disaster Mitigation Act of 2000 (Public Law 106-390) and the implementing regulations set forth by the Interim Final Rule published in the Federal Register on February 26, 2002 (44 CFR §201.6) . Hereafter, these requirements and regulations will be referred to collectively as the Disaster Mitigation Act, or DMA. While the act emphasized the need for mitigation plans and more coordinated mitigation planning and implementation efforts, the regulations established the requirements that local hazard mitigation plans (LHMPs) must meet in order for a local jurisdiction to be eligible for certain federal disaster assistance and hazard mitigation funding under the Robert T. Stafford Disaster Relief and Emergency Act (Public Law 93-288).
Because the Merced County planning and response area is subject to many kinds of hazards, access to these programs is vital. As a result, the County and their participating jurisdictions completed a comprehensive plan update process in 2021 to bring the MJHMP into compliance with recent legislation related to climate change and to address new human health and natural hazards and emerging concerns.
Information in this plan will be used to help guide and coordinate mitigation activities and decisions for local land use policy in the future. Proactive mitigation planning will help reduce the cost of disaster response and recovery to the community and its property owners by protecting critical community facilities, reducing liability exposure, and minimizing overall community impacts and disruption. The Merced County planning area has been affected by hazards in the past and is thus committed to reducing future disaster impacts and maintaining eligibility for federal funding.
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This hazard mitigation plan identifies resources, information, and strategies for reducing risk from natural hazards. Elements and strategies in the plan were selected because they meet a program requirement and because they best meet the needs of the planning partners and their citizens. One of the benefits of multi-jurisdictional planning is the ability to pool resources and eliminate redundant activities within a planning area that has uniform risk exposure and vulnerabilities. FEMA encourages multi-jurisdictional planning under its guidance for the DMA. This plan will help guide and coordinate mitigation activities throughout the planning area. The plan was developed to meet the following objectives:
Ɣ Meet or exceed requirements of the DMA.
Ɣ Enable all planning partners to use federal grant funding to reduce risk through mitigation.
Ɣ Meet the needs of each planning partner as well as state and federal requirements.
Ɣ Create a risk assessment that focuses on Merced County hazards of concern.
Ɣ Create a single planning document that integrates all planning partners into a framework that supports partnerships within the County and puts all partners on the same planning cycle for future updates.
Ɣ Meet the planning requirements of FEMA’s Community Rating System (CRS), allowing planning partners that may choose to participate in the CRS program to enhance their CRS classifications.
Ɣ Coordinate existing plans and programs so that high-priority initiatives and projects to mitigate possible disaster impacts are funded and implemented.
1.4 Multi-Jurisdictional Planning
All citizens and businesses of Merced County are the ultimate beneficiaries of this MJHMP. The plan reduces risk for those who live in, work in, and visit the County. It also provides a viable planning framework for all foreseeable natural hazards that may impact the County. Participation in development of the plan by key stakeholders in the County helps ensure that outcomes will be mutually beneficial. The resources and background information in the plan are applicable countywide, and the plan’s goals and recommendations can lay groundwork for the development and implementation of local mitigation activities and partnerships.
The Merced County MJHMP is a multi-jurisdictional plan that geographically covers everything within Merced County’s jurisdictional boundaries (hereinafter referred to as the planning area). Unincorporated Merced County and the following jurisdictions participated in the 2021 update planning process:
Ɣ Merced County
Ɣ City of Atwater
Ɣ City of Dos Palos
Ɣ City of Gustine
Ɣ City of Livingston
Ɣ City of Los Banos
Ɣ City of Merced
The cities of Dos Palos and Gustine are new participating jurisdictions as part of the 2021 MJHMP update process, and this is their first hazard mitigation plan. The City of Merced also prepared a stand-alone LHMP in 2015 and is now participating in the MJHMP update process.
1.5 Plan Organization
Ɣ Section 1: Introduction
Ɣ Section 2: Community Profile and Capability Assessment Ɣ Section 3: Planning Process
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Ɣ Section 4: Hazard Identification and Risk Assessment (HIRA) Ɣ Section 5: Mitigation Strategy
Ɣ Section 6: Plan Adoption, Implementation and Maintenance Ɣ Appendix A: Planning Team
Ɣ Appendix B: Planning Process Documentation
Ɣ Appendix C: Approval and Adoption
Ɣ Appendix D: Mitigation Categories and Alternatives
Ɣ Appendix E: Annual Progress Meeting Agenda and Report Template Ɣ Appendix F: Outreach Strategy
Ɣ Appendix G: Annexes
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2 COMMUNITY PROFILE AND CAPABILITY ASSESSMENT
2.1 History
An expedition led by Gabriel Moraga in 1806 came upon a river he named El Rio de Nuestra Señora de la Merced (River of Our Lady of Mercy), or Merced River in which derived the name of the County. During a period between 1841 and 1844, while California was a province of independent Mexico, four Mexican land grants were made which eventually became Merced County. The County was created by the Act of April 19, 1855 and included parts of Mariposa County. Parts of the territory were also given to Fresno County in 1856. Merced County’s current boundaries and its location within the State of California is shown in Figure 2-1 below.
The early economy of the County centered on ranching and farming. Settlement in Merced County remained modest throughout much of the county's first century. Merced County is considered to be located in the world’s most productive agricultural area, which, today, is a major source of employment, along with food processing, retailing, and light manufacturing.
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Figure 2-1 County of Merced Planning Area
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2.2 Geography and Climate
Merced County encompasses approximately 2,000 square miles, ranking it the 25 th largest out of a total of 58 counties in California. It is located in the heart of the San Joaquin Valley, north of Fresno and southeast of San Jose, and spans from the coastal ranges to the foothills of Yosemite National Park. The City of Merced is the County seat and offers a small community atmosphere, residential neighborhoods characterized by wide, tree-lined streets, and homes in a wide economic range.
The County of Merced is neighbored by the counties of Tuolumne County and Mariposa County to the northeast, Madera County to the south and east, Fresno County to the southeast, San Benito County to the southwest, Santa Clara County to the west, and Stanislaus County to the northwest.
Merced County is home to two national protected areas – Merced National Wildlife Refuge and San Luis National Wildlife Refuge. The former Castle Air Force Base and the United States Penitentiary-Atwater are located in an unincorporated area near Atwater. The Board of Supervisors is the governing body for Merced County.
Elevation in Merced County, according to data gathered by the Shuttle Radar Topography Mission ranges from 6 feet above mean sea level (msl) ranking it 20 in terms of lowest elevations when compared to a total of 58 counties in California, to 1,781 feet above msl ranking it 54 in terms of highest elevation when compared to a total of 58 counties in California. The rivers in this region include the Merced and Chowchilla, which are both tributaries of the San Joaquin River. On average, there are 263 sunny days per year in Merced County. The number of days with any measurable precipitation is 49 with an average of approximately 12 inches of rain per year. The month of July is the warmest month with an average high around 96 degrees. The month of January is the coolest month with an average low of 37 degrees.
2.3 Economy
Merced County is located in the heart of California’s rapidly growing San Joaquin Valley, the richest agricultural area in the world. With that distinction also come the challenges of an economy which has historically been dependent on seasonal agriculture and low wages. Select 2019 economic characteristics estimated for Merced County by the U.S. Census Bureau American Community Survey (ACS) are shown in Table 2-1.
Table 2-1 Merced County Economic Characteristics
Merced County
Families Below Poverty Level 17.2%
Individuals Below Poverty Level 21.2%
Median Home Value $252,700
Median Household Income $53,672
Per Capita Income $23,011
Population >16 Years Old in Labor Force 59.6%
Population Employed 52.6%
Source: U.S. Census Bureau ACS 2015-2019 5-Year Data Profile Merced County provides a broad range of services to its residents, businesses, and visitors, and manages and operates its facilities to meet community needs. Agriculture is the foundation of Merced County’s economy, and the County consistently ranks as one of California’s top five producers of milk and cream, Merced County Multi-Jurisdictional Hazard Mitigation Plan Planning Process
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chickens, almonds, alfalfa, cattle and calves, silage, and tomatoes. Merced County is home to four agricultural processing facilities that are among the largest of their kind in the world: Ernest and Julio Gallo winery, Hilmar Cheese production facility, Ingomar Packing Company tomato processing plant, and Foster Farms poultry processing facility. The ACS 5-Year data profiles also provide estimates for total employment by industry sector. These employment trends are shown below in Table 2-2.
Table 2-2 Merced County Employment by Industry Sector
Industry Sector Percent of Workforce
Educational services, and health care and social assistance 21.60% Agriculture, forestry, fishing and hunting, and mining 12.90% Manufacturing 11.30%
Retail trade 11.20%
Arts, entertainment, and recreation, and accommodation and food services 7.80% Construction 7.10%
Professional, scientific, and management, and administrative and waste management services
6.20%
Transportation and warehousing, and utilities 5.90%
Other services, except public administration 4.50%
Public administration 4.50%
Wholesale trade 3.20%
Finance and insurance, and real estate and rental and leasing 2.90% Information 0.90%
Source: U.S. Census Bureau ACS 2015-2019 5-Year Data Profile
2.4 Population
The total estimated population of Merced County in 2019 was 271,382 up from 255,793 people in 2010.
This constitutes an approximately 6% increase in population since the last census. Table 2-3 and Table 2-4 show several key demographic and social characteristics of Merced County, how those characteristics have changed over the last five years, and how those characteristics compare to the rest of the state and nation. Increases in population growth also increase exposure to severe weather-related hazards, pandemic/epidemics as well as earthquakes. This increase in growth also puts more demand on water resources and can increase vulnerability to drought.
Table 2-3 Merced County Demographic an d Social Characteristics, 2015-2019 Merced County 2015 2019 % Change
Population 263,885 271,382 2.84%
Median Age 30.4 ϯϭ͘ϭ 2.30%
Total Housing Units 84,063 85,251 1.41%
Housing Occupancy Rate 92.40% 93.80% 1.52%
% of Housing Units with no Vehicles
Available 7.50% 6.90% -8.00%
Median Home Value $161,200 $252,700 56.76%
Unemployment 9.70% 7.10% -26.80%
Mean Travel Time to Work (minutes) 26.1 28.6 9.58%
Median Household Income $42,462 $53,672 26.40%
Per Capita Income $18,204 $23,011 26.41%
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Merced County 2015 2019 % Change
% of Individuals Below Poverty Level 26.10% 21.20% -18.77% # of Households 77,692 80,008 2.98%
Average Household Size 3.32 3.32 0.00%
% of Population Over 25 with High School
Diploma 67.90% 69.10% 1.77%
% of Population Over 25 with Bachelor’s
Degree or Higher 13.10% 13.80% 5.34%
% with Disability 15.70% 13.00% -17.20%
% Speak English less than "Very Well" 22.80% 22.70% -0.44% Source: U.S. Census Bureau ACS 5-Year Data Profiles, 2015-2019 Table 2-4 Demographic and Social Characteri stics Compared to the State and Nation Demographic & Social Characteristics (as of 2019) County California U.S.
Median Age 31.1 36.5 38.1
Housing Occupancy Rate 93.80% 92.00% 87.90%
% of Housing Units with no Vehicles Available 6.90% 7.10% 8.60% Median Home Value $252,700 $505,000 $217,500
Unemployment 7.10% 3.80% 3.40%
Mean Travel Time to Work (minutes) 28.6 29.8 26.9
Median Household Income $53,672 $106,916 $62,843
Per Capita Income $23,011 $36,955 $34,103
% of Individuals Below Poverty Level 21.20% 13.40% 13.40% Average Household Size 3.32 2.95 2.62
% of Population Over 25 with High School Diploma 69.10% 83.30% 88.00% % of Population Over 25 with bachelor’s degree or Higher 13.80% 33.90% 32.10% % with Disability 13.00% 10.60% 12.60%
% Speak English less than "Very Well" 22.70% 17.80% 8.40% Source: U.S. Census Bureau ACS 5-Year Data Profiles, 2015-2019 Table 2-5 breaks down the demographics of the county by sex and race.
Table 2-5 Merced County Demographics by Race and Sex
Merced County Population %
Total Population 271,382 ---
Male 136,987 50.50%
Female 134,395 49.50%
Hispanic or Latino 161,814 59.6%
White alone 75,037 27.6%
Black alone 7,812 2.9%
Asian alone 19,650 7.2%
American Indian and Alaska Native alone 931 0.3%
Native Hawaiian and Other Pacific Islander alone 607 0.2% Some other race alone 226 0.1%
Two or more races alone 5,305 2.0%
Source: U.S. Census Bureau ACS 5-Year Data Profiles, 2015-2019
2.5 County’s Mitigation Capabilities
The following section assesses the County’s and each participating jurisdictions’ existing capabilities to pursue hazard mitigation. The capability assessment analyzes Merced County’s capabilities that can be leveraged to mitigate hazards. Combining the risk assessment with the mitigation capability assessment Merced County Multi-Jurisdictional Hazard Mitigation Plan Planning Process
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results in the County’s “net vulnerability” to disasters, and more accurately focuses the goals, objectives, and proposed actions of this plan.
The Hazard Mitigation Planning Team (HMPT) used a two-step approach to conduct this assessment for the County and jurisdictions. First, an inventory of common mitigation activities was made through the use of a matrix. The purpose of this effort was to identify policies and programs that were either in place, needed improvement, or could be undertaken if deemed appropriate. Second, the HMPT conducted an inventory and review of existing policies, regulations, plans, and programs to determine if they contributed to reducing hazard-related losses or if they inadvertently contributed to increasing such losses.
This assessment is divided into four sections: regulatory mitigation capabilities; administrative and technical mitigation capabilities; fiscal mitigation capabilities; and mitigation outreach and partnerships.
Additional information on jurisdiction capabilities can also be found in the participating jurisdiction’s annexes.
2.5.1 Regulatory Mitigation Capabilities
The regulatory and planning capabilities table lists planning and land management tools typically used by local jurisdictions to implement hazard mitigation activities and indicate those that are in place in Merced County. Table 2-6 identifies the planning and land management tools typically used by local jurisdictions to implement hazard mitigation activities and indicates those that are in place in Merced County.
Table 2-6 Regulatory Mitigation Capabilities
Regulatory Tool
(ordinances, codes,
plans)
Merced
County Atwater Dos Palos Gustine Livingsto
n Los Banos Merced
General Plan Yes Yes Yes Yes Yes Yes Yes
Zoning ordinance Yes Yes Yes Yes Yes Yes Yes
Subdivision ordinance Yes Yes Yes Yes Yes Yes Yes
Growth management
ordinance Yes No Yes No
Floodplain ordinance Yes Yes No No Yes Yes Yes
Other special purpose
ordinance (storm water,
steep slope, wildfire) Yes N/A N/A No
Yes, Fire
Protection
Ordinance
Yes, Storm
Water
Pollution
Plan
N/A
Building code Yes Yes Yes Yes Yes Yes Yes
Fire department ISO
rating Yes Yes, Rating
3 Yes Yes Yes, Rating
5 Yes, Rating
3 Yes, Rating
2 Erosion or sediment
control Yes N/A No No No Yes Yes
Storm water
management program Yes Yes Yes Yes Yes Yes Yes
Site plan review
requirements Yes Yes Yes Yes Yes Yes
Capital improvements
plan Yes Yes Yes Yes Yes Yes Yes
Economic development
plan Yes Yes Yes Yes Yes Yes Yes
Local Emergency
Operations Plan Yes Yes Yes Yes Yes Yes Yes
Other special plans N/A N/A n/a No No Yes N/A
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Regulatory Tool
(ordinances, codes,
plans)
Merced
County Atwater Dos Palos Gustine Livingsto
n Los Banos Merced
Flood insurance study or
other engineering study
for streams
Yes Yes No -
NSFHA Yes Yes N/A Yes
Elevation certificates (for
floodplain development) Yes No No No No N/A Yes
Source: HMPT
Related Plans and Regulations
Merced County General Plan, 2013 - A comprehensive 2030 Merced County General Plan was adopted December 2010. This General Plan defines the County’s goals, objectives and policies that guide the physical growth, use and development of land under the jurisdictional authority of the County through the year 2030. The General Plan may address other topics that the community deems relevant to its development, such as economic development, historic preservation, and urban design. There are five principles highlighted as the core issues facing the Merced County community in the adoption of the General Plan: Agriculture, Economic Development, Environmental Quality, Public Facilities and Services, and Transportation. The County also promotes their public safety goals through the Health and Safety Element, among their ten other General Plan elements.
The purpose of the Public Health and Safety Element is to reduce or eliminate long-term risk to people and property from natural or human caused hazards. Traditionally viewed as an element that focuses on planning for catastrophes, this element is now expanded to include community health and community safety related issues that are more commonly associated with the built environment as affecting the health and safety of residents living within the County. The Element also covers goals and policies focused on geologic and seismic hazards, flood hazards, fire hazards, airport safety, hazardous materials, climate adaptation, noise, and environmental justice.
Merced County Emergency Operations Plan, 2013 - The Emergency Operations Plan addresses the planned response to emergency situations associated with natural disasters, technological incidents, human caused events and national security emergencies in or affecting Merced County. The plan establishes the emergency management organization required to mitigate any significant emergency or disaster affecting Merced County; identifies the policies, responsibilities, and procedures required to protect the health and safety of communities, public and private property, and the environmental effects of natural, human caused and technological emergencies and disasters; and establishes the operational concepts and policies for disaster response and recovery.
County of Merced Fire Management Plan –The County of Merced reorganized their Fire Department and entered into a Cooperative Fire Protection Agreement with the California Department of Forestry and Fire Protection (CAL FIRE) for the provision of fire protection services. The contract began in 1988. The CAL FIRE agreement provides daily staffing at fire stations, dispatch, management, incident command, training, investigation and fire prevention activities. Through the Cooperative Agreement CAL FIRE also manages the Office of Emergency Services for the County. The County’s Fire Management Plan is a product of the implementation of the State Fire Plan. The State Fire Plan provides an analysis procedure utilizing, in part, computer based geographical information data that is validated by experienced fire managers to assess fire fuel hazards and risks in order to design and implement mitigating activities. The Fire Management Plan provides background information, fuels and fire data, proposed projects, and individual Battalion reports outlining mitigating activities commonly carried out each year.
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Madera-Mariposa-Merced Unit (MMU) 2020 Strategic Fire Plan – The MMU Strategic Fire Plan is an annual fire plan establishing goals and priorities that align with CAL FIRE’s Strategic Plan and the California Fire Plan, while also identifying goals and priorities specific to the Unit. The California Fire Plan is the road map for reducing the risk of wildfire in California, where as the MMU Strategic Fire Plan identifies strategic goals and objectives that target the anticipation and reduction of wildfire within the boundaries of the Unit. For the challenges facing the Unit, such as extreme heat, tree mortality, and drought conditions across the three counties, the plan addresses problem areas and risk. This plan also seeks to improve operational effectiveness, budgetary and fiscal circumstances, foster a healthy ecosystem, and improve firefighter safety by identifying working projects specific to each Battalion within the MMU.
Emergency Services Ordinance, Chapter 2.72 - The purposes of this ordinance are to provide for the preparation and implementation of plans for the protection of people and property within the County in the event of an emergency; the direction of the emergency organization; and the coordination of the emergency functions of the County with the cities in the County and with all other public agencies, corporations, organizations, and affected private persons. The ordinance establishes the Merced Operational Area Council and designates the membership of the council. The council’s powers include the development of emergency and mutual aid plans and agreements and the ordinances and resolutions to implement them.
Fire Mitigation Ordinance Chapter 9.24 – The purpose of this ordinance is to impose a fee on new buildings and improvement projects because they contribute to the increase for potential fire danger in Merced County, it is in the best interest of the citizens of the County and promotes and protects the health and welfare of the residents of Merced County. It is necessary that persons who carry out such projects within the County pay a reasonable fee to mitigate such fire danger.
Floodplain Management Ordinance Chapter 18.30 - It is the purpose of the ordinance to promote the public health, safety, and general welfare, and to minimize public and private losses due to flood conditions in specific areas by legally enforceable regulations applied uniformly throughout the community to all publicly and privately owned land within flood prone, mudslide [i.e. mudflow] or flood related erosion areas. These regulations are designed to:
Ɣ Protect human life and health;
Ɣ Minimize expenditure of public money for costly flood control projects; Ɣ Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;
Ɣ Minimize prolonged business interruptions;
Ɣ Minimize damage to public facilities and utilities such as water and gas mains; electric, telephone and sewer lines; and streets and bridges located in areas of special flood hazard; Ɣ Help maintain a stable tax base by providing for the sound use and development of areas of special flood hazard so as to minimize future blighted areas caused by flood damage; Ɣ Ensure that potential buyers are notified that property is in an area of special flood hazard; and Ɣ Ensure that those who occupy the areas of special flood hazard assume responsibility for their actions.
Merced Groundwater Subbasin Groundwater Sustainability Plan – The Sustainable Groundwater Management Act (SGMA) requires the formation of local Groundwater Sustainability Agencies (GSAs) to oversee the development and implementation of Groundwater Sustainability Plans (GSPs). The goal of the GSPs is to achieve sustainable management of the State’s groundwater basins. The purpose of the Merced Groundwater Subbasin GSP is to bring the Merced Groundwater Basin (Merced Subbasin), a critically over drafted basin located within the San Joaquin Valley, into sustainable groundwater management by 2040.
This subbasin is heavily reliant on groundwater and the County water users recognize the basin has been in overdraft. This plan is the outcome of collaboration among the County of Merced and numerous water Merced County Multi-Jurisdictional Hazard Mitigation Plan Planning Process
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districts and cities within the Merced Subbasin. The 2019 GSP outlines how the GSAs will achieve sustainable groundwater management on a long-term basis by increasing recharge and reducing groundwater pumping through various implementation programs and projects.
Merced Integrated Regional Water Management Plan. The Merced Integrated Regional Water Management Plan (IRWMP) is the first IRWMP for the Merced Region. The plan was developed as a multi- stakeholder process that builds on the Region’s history of collaboration on water resource management issues. The IRWMP is a water resources planning document for the Region and serves as a blueprint for water resources management. It was developed based on Proposition 84 IRWM program guidelines and from input from a Regional Advisory Committee. Similar to the GSP, the IRWMP establishes several objectives and performance measures selected to provide long-term direction towards meeting project goals related to managing flood flows for public safety, water supply, recharge, and natural resource management; meeting water demands (agriculture, urban, and environmental needs); correcting groundwater overdraft conditions; and improving coordination of land use and water resource planning.
The IRWMP also includes objectives that address water use efficiency, water quality, natural resource management, water-related needs of disadvantaged communities, recreation opportunities, climate change adaptation and mitigation; and public outreach and enhancing communication among stakeholders in the Region.
2.5.2 Administrative and Technical Mitigation Capabilities Table 2-7 below identifies the county personnel responsible for activities related to mitigation and loss prevention in Merced County and the unincorporated areas. Many positions are full time and/or filled by the same person. A summary of technical resources follows.
Table 2-7 Merced County Administrative an d Technical Mitigation Capabilities Personnel Resources Yes/No Department/Position
Planner/engineer with knowledge of land
development/land management practices
Yes Public works/ Deputy Director Roads
Engineer/professional trained in construction
practices related to buildings and/or infrastructure
Yes Public works/ Deputy Director Roads
Planner/engineer/scientist with an understanding
of natural hazards
Yes Public works/ Deputy Director Roads
Personnel skilled in Geographic information
systems (GIS)
No
Full time building official Yes Community and Economic development Building Division
Floodplain manager Yes Community and Economic development Building Division
Emergency manager No Office of Emergency Services (OES) Grant writer Yes
Other personnel N/A
GIS Data Resources
(Hazard areas, critical facilities, land use, building
footprints, etc.)
No
Warning Systems/Services
(Reverse 9-11, cable override, outdoor warning
signals)
Yes OES
Other N/A
Source: HMPT
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Office of Emergency Services
The Merced Office OES provides preparedness before, and coordination direction during, large-scale emergencies and disasters. Merced OES coordinates with partner agencies including the six incorporated cities within the county, special districts, and key private agencies in providing planning, response, recovery, and mitigation activities as a result of disaster related incidents.
Merced County, in conjunction with the cities of Merced, Los Banos, Livingston, Gustine, Dos Palos, emergency fire, law enforcement, health, and Emergency Medical Service agencies, launched the Emergency Notification System (ENS) – a technical capability service allowing residents throughout the entire county to be alerted of an emergency or an important community alert in their area. The improved Merced County ENS will allow residents throughout the County alternate ways of being contacted during an emergency, such as cell phones, business phones, home phones, emails, text messages or hearing- impaired receiving devices. More importantly, individuals can choose how they will be notified and in what preference order. When an emergency message is issued about a potential safety hazard or concern, messages will be sent to all standard voice and text communication devices registered in the system, including home phones, cell phones, email, and more. Residents and businesses with listed telephone numbers are already included in the system. Those residents having only a cell phone or wanting to be contacted through different methods can provide the information using the registration link at www.co.merced.ca.us/alert.
Merced County Fire Department
The primary mission of the Merced County Fire Department is to provide a range of programs aimed at protecting the lives and property of the people of Merced County from the adverse effects of fires, sudden medical emergencies, exposure to hazardous materials, or other dangerous conditions. The programs maintained by the department include:
Ɣ Comprehensive fire protection planning
Ɣ Fire prevention education
Ɣ Fire law and code enforcement
Ɣ Suppression and recovery
The Merced County Fire Department provides first responder-level Emergency Medical Services (EMS), including rescue and extrication, as well as control and mitigation of hazardous materials emergency incidents. The Merced County Fire Department personnel and equipment are also available to provide mutual aid fire/rescue/EMS services to cooperating agencies and participate in the statewide fire and rescue mutual aid system.
In addition, assistance and support are also provided for other non-fire emergencies such as floods, earthquakes, and other disasters.
Extreme Heat Preparedness
The County of Merced manages extreme heat events by providing cooling zones and centers for County residents. When the heat index is expected to exceed 105 degrees, various cooling centers in the County were opened to help residents cope with the extreme temperatures. Cooling centers were open during the summer months of 2021 in six of the participating jurisdictions, and at 12 Merced County libraries. In events of extreme heat, the County OES provides public notification alerts to residents with information on the location and hours of operations of cooling centers throughout the County. Transportation to these centers is also often provided free of charge. Additional information on health and safety measures for residents is also provided. Public notifications flyers distributed during the summer of 2021 are shown below.
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Figure 2-2 Public Notification for Extreme Heat and Safety Preparedness
Source: Merced County Public Information Officer 2021
2.5.3 Fiscal Mitigation Capabilities
The following table identifies financial tools or resources that the county could potentially use to help fund mitigation activities. There are currently no specific funding sources for hazard mitigation.
Table 2-8 Merced County Financial Capabilities
Financial Resources Accessible/
Eligible to Use
Comments/Has this been used for
mitigation in the past?
Community Development Block Grants Yes No
Capital improvements project funding Yes No
Authority to levy taxes for specific
purposes
Yes Has not been used. Must be approved by
voters.
Fees for water, sewer, gas, or electric
services, new development
Yes Has not been used. Services provided through
cities or districts and levied through property
assessments
Incur debt through general obligation
bonds
Yes No
Incur debt through special tax bonds Yes Has not been used. Must be approved by two- thirds voters.
Incur debt through private activities Yes Has not been used. Do not have any in place.
Federal Grant Programs (HMGP) Yes Has not been used. Various departments in Merced County are eligible.
Source: Planning Team
2.5.4 Other Mitigation Programs and Partnerships
Table 2-9 below summarizes some of the mitigation partnerships and education or outreach capabilities available to Merced County.
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Table 2-9 Merced County Educa tion and Outreach Capabilities Education & Outreach Yes/No Comments
Local Citizen Groups That
Communicate Hazard Risks Yes See below
Firewise USA No 6 communities within the county are Firewise communities StormReady Yes UC Merced is a participant
Other
American Red Cross: The American Red Cross identified several capability enhancements through collaboration with the county, cities, and fire departments of Merced County. Programs such as outreach campaigns for preparedness education, continuing shelter inspections, and updating existing points of contact for shelter sites. These efforts will improve the American Red Cross’ ability to conduct mitigation, preparedness, and response efforts in Merced County.
2.5.5 Opportunities for Enhancement
The 2021 MJHMP update provided the County and the participating jurisdictions an opportunity to review and update the capabilities currently in place to mitigate hazards. This also provided an opportunity to identify where capabilities could be improved or enhanced. Specific opportunities could include:
Plan Updates: Merced County has identified several plans which could be updated, such as the County Emergency Operations Plan, Disabled, Access, and Functional Needs plans, and the Flood Annex to the EOP. During the update process of each of these plans there is an opportunity to reference the MJHMP and enhance the capabilities for implementation of goals and objectives of each plan. The City of Livingston has also identified potential updates to their Emergency Response and Disaster Plan. The City of Merced identified an update to the Water System Response Plan, which would meet the requirements of the America’s Water Infrastructure Act. As mentioned above, updates to related plans such as these provide an opportunity to both build resilience and enhance the cross-plan integration of the MJHMP.
Training: Provide training opportunities to help inform County staff on how best to integrate hazard information and mitigation projects into their departments. Merced County has identified a multi-year training and exercise plan which would cover all county departments. The City of Los Banos has identified an inter-departmental training effort to be undertaken. The City of Dos Palos has also identified providing opportunities for Incident Command System training for city staff.
Firewise: Firewise USA® is a voluntary program that provides a framework to help neighbors get organized, find direction, and take action to increase the ignition resistance of their homes and community. The program is co-sponsored by the USDA Forest Service, the U.S. Department of the Interior, and the National Association of State Foresters. As of June 2021, neither Merced County nor any of the incorporated jurisdictions in the county were participants in the program. In order to become a Firewise USA site, a neighborhood, community, city, or county must form a board or committee comprised of residents and stakeholders, obtain a written wildfire risk assessment, develop and maintain an action plan, and contact the applicable state liaison to the program.
Storm Ready: As of June 2021, neither Merced County nor any of the incorporated jurisdictions in the county are certified as Storm Ready communities. The UC Merced is certified Storm Ready. The National Weather Service’s Storm Ready program helps local governments handle extreme weather and improve the timeliness and effectiveness of hazardous weather-related warnings for the public. To be officially Storm Ready, a community must:
Ɣ Establish a 24-hour warning point and emergency operations center Ɣ Have more than one way to receive severe weather warnings and forecasts and to alert the public Merced County Multi-Jurisdictional Hazard Mitigation Plan Planning Process
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Ɣ Create a system that monitors weather conditions locally Ɣ Promote the importance of public readiness through community seminars, and Ɣ Develop a formal hazardous weather plan, which includes training severe weather spotters and holding emergency exercises
Community Rating System (CRS): An additional indicator of floodplain management capability is the active participation of local jurisdictions in the CRS. The CRS is an incentive-based program that encourages counties and municipalities to undertake defined flood mitigation activities that go beyond the minimum requirements of the NFIP, adding extra local measures to provide protection from flooding.
All of the 18 creditable CRS mitigation activities are assigned a range of point values. As points are accumulated and reach identified thresholds, communities can apply for an improved CRS class. Class ratings, which run from 10 to 1, are tied to flood insurance premium reductions. As class ratings improve (decrease), the percent reduction in flood insurance premiums for NFIP policy holders in that community increases. These potential discounts in flood insurance premiums through CRS are summarized in Table 2-10 below. As of 2021 neither Merced County nor any of the incorporated jurisdictions in the county participate in the CRS. Should the City of Merced and Merced County decide to join the CRS, it would be an opportunity for enhancement of existing mitigation capabilities and help make flood insurance more affordable in the future.
Table 2-10 CRS Premium Discounts
Class Discount Class Discount SFHA (Zones A, AE, A1-A30, V, V1-V30, AO, and AH): Discount varies depending on class. SHFA (Zones A99, AR/A, AR/AE.
AR/A1-A30, AR/AH, and AR/AO): 10% discount for Classes 1-6; 5% discount for Classes 7-9. Non-SFHA (Zones B, C, X, D): 10% discount for Classes 1-6; 5% discount for Classes 7-9. In determining CRS premium discount, all AR and A99 Zones are treated as non-SFHAs.
1 45% 6 20%
2 40% 7 15%
3 35% 8 10%
4 30% 9 5%
5 25% 10 --
Source: FEMA CRS Coordinators Manual
Financial Capability Improvements: There are several financial resources listed in Table 2-8 that the County could leverage in the future for funding mitigation efforts. In particular, the LHMP provides eligibility for the FEMA HMA grants. County OES staff can attend workshops and trainings regarding the grant application process and how to develop successful grant applications under the HMGP. The California Office of Emergency Services (Cal OES) periodically hosts related trainings and webinars.
Understanding the types of projects that can be funded, and the components of a successful application will enhance chances of a successful grant award.
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3 PLANNING PROCESS
Requirement §201.6(b) and §201.6(c)(1):
An open public involvement process is essential to the development of an effective plan. In order to develop a more comprehensive approach to reducing the effects of natural disasters, the planning process shall include:
(1) An opportunity for the public to comment on the plan during the drafting stage and prior to plan approval;
(2) An opportunity for neighboring communities, local and regional agencies involved in hazard mitigation activities, and agencies that have the authority to regulate development, as well as businesses, academia, and other private and nonprofit interests to be involved in the planning process; and
(3) Review and incorporation, if appropriate, of existing plans, studies, reports, and technical information.
[The plan shall document] the planning process used to develop the plan, including how it was prepared, who was involved in the process, and how the public was involved.
3.1 Background on Mitigation Planning in Merced County The primary purpose of the Merced County MJHMP update is to reduce or eliminate long-term risk to people and property from natural hazards and their effects on the Merced County planning area. Merced County recognized the need and importance of a LHMP and initiated its development in 2013 after receiving a grant from FEMA, which also served as the primary funding source for this plan.
The plan underwent a comprehensive update in 2021. The planning process followed during the update was similar to what was used in the original plan development. This planning process utilized the input from a multi-jurisdictional HMPT. A significant change from the 2014 Plan is the inclusion of all of the incorporated communities within the planning area (six), versus three in the previous update. Wood Environment & Infrastructure Solutions, Inc. (Wood) was procured to assist with the update in 2021. The process is described further in this section and documented in Appendix B.
3.2 What’s New in the Plan Update
DMA Requirement §201.6(d)(3):
A local jurisdiction must review and revise its plan to reflect changes in development, progress in local mitigation efforts, and changes in priorities, and resubmit it for approval within 5 years in order to continue to be eligible for mitigation project grant funding.
The updated MJHMP complies with FEMA guidance and California Office of Emergency Services guidelines for LHMPs. The update followed the requirements noted in the DMA of 2000 and FEMA’s 2013 Local Hazard Mitigation Planning Handbook.
This MJHMP update involved a comprehensive review and update of each section of the 2014 plan and includes an assessment of the progress in evaluating, monitoring and implementing the mitigation strategy outlined in the initial plan. The planning process provided an opportunity to review jurisdictional priorities related to hazard significance and mitigation actions, and revisions were made where applicable 2021 Merced County Hazard Mitigation Plan
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to the plan and the municipal annexes. Another major change in priority was the desire to include all incorporated jurisdictions in the County, including new annexes for the municipalities of Dos Palos, Gustine and Merced. Only the information and data still valid from the 2014 plan was carried forward as applicable into this MJHMP update.
3.2.1 Plan Section Review and Analysis – 2021 Update
During the 2021 plan update, the HMPT updated each of the sections of the previously approved plan to include new information. Wood developed a summary of each section in the plan and guided the HMPT through the elements that needed updating during the kickoff webinar in December 2020. This included analyzing each section using FEMA’s local plan update guidance (2013) to ensure that the plan met the latest requirements. In addition, the FEMA Local Mitigation Plan Review Tool that was provided with the approval of the 2014 version of this plan was referenced, in particular the 2014 FEMA comments on opportunities for improvement were considered and addressed in the 2021 update. The HMPT and Wood determined that nearly every section of the plan would need revision to align the plan with the latest FEMA planning guidance and requirements and recent California legislation. A summary of the changes in this plan update is highlighted in the table below.
Table 3-1 Merced County Hazard Miti gation Plan Update Highlights Plan Section Summary of Plan Review, Analysis, and Updates
1. Introduction Revised to reflect updated plan and 2021 planning process
2. County Profile and
Capability Assessment
Updated with recent census data and current economy description Updated land use and development trends
3. Planning Process
Describes and documents the planning process for the 2019 update, including coordination among agencies
Describes how 2014 plan was integrated with/into other planning efforts.
Removed 2014 planning process info.
Describes changes to jurisdictional participation
Describes 2021 public participation process
Describes the Hazard Mitigation Planning Committee
Describes the 10-step process followed for the update
4. Hazard Identification
and Risk Assessment
Drought is now profiled as separate hazards and are no longer part of Severe Weather Discussion on levee failure has been added to Flood
Climate change information has been added to each hazard profile Updated list of disaster declarations to include recent data.
Updated tables to include recent National Center for Environmental Information data.
Updated past occurrences for each hazard to include recent data. 2014 Plan on Vulnerability Assessment is now included with the Risk Assessment section as subsections by hazard.
Updated critical facilities identified from the 2014 plan.
Updated growth and development trends to include recent census and local data sources.
Updated historic and cultural resources using local/state/national sources.
Updated property values for vulnerability and exposure analysis, using updated building information based on assessor’s data.
Updated estimate flood losses using the latest Digital Flood Insurance Rate Map (DFIRM) and assessor’s data.
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Plan Section Summary of Plan Review, Analysis, and Updates Updated National Flood Insurance Program (NFIP) data and Repetitive Loss structure data from the previous plan.
Incorporated new hazard loss estimates since 2014, as applicable.
Used updated GIS inventory data to assess wildfire threat to the County Updated HAZUS-MH Level I earthquake vulnerability analysis data Updated information regarding specific vulnerabilities to hazards, including maps and tables of specific assets at risk, specific critical facilities at risk, and specific populations at risk.
Revisited and updated hazard significance/priority levels.
Updated maps in plan where appropriate.
5. Mitigation Strategy
Indicated what actions have been implemented that may reduce previously identified vulnerabilities.
Updated mitigation strategy based on the results of the updated risk assessment, completed mitigation actions, and implementation obstacles and opportunities since the completion of the 2014 plan.
Reviewed and updated goals and objectives based on HMPT input.
Included updated information on how actions are prioritized, or how priorities changed.
Reviewed mitigation actions from the 2014 plan and developed a status report for each; identified if actions have been completed, deleted, or deferred/carried forward.
Updated priorities on actions.
Identify examples of successful implementation to highlight positive movement on actions identified in 2014 plan.
Identified new mitigation actions proposed by the HMPT with more detail on implementation than the previous plan.
Developed a summary table of mitigation actions for all participating jurisdictions.
6. Plan Review,
Evaluation and
Implementation
Reviewed and updated procedures for monitoring, evaluating, and updating the plan.
Revised to reflect current methods.
Updated the system for monitoring progress of mitigation activities by identifying additional criteria for plan monitoring and maintenance.
Added a process for incorporation of the HMP into existing mechanisms
7. Plan Adoption Updated to reflect 2021 process.
Jurisdictional Annexes
*Developed annexes for new participating jurisdictions in 2021.
Updated previous participants’ annexes with recent census data.
Updated past event history and hazard loss estimates.
Added new maps and updated old maps as needed.
Updated mitigation actions from 2016 and added new mitigation actions.
Updated and integrated the following existing and new annexes:
A City of Atwater
B City of Dos Palos*
C City of Gustine*
D City of Livingston
E City of Los Banos
F City of Merced*
Appendices Appendix A: Planning Team
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Plan Section Summary of Plan Review, Analysis, and Updates Appendix B: Planning Process Documentation
Appendix C: Approval and Adoption
Appendix D: Mitigation Categories and Alternatives
Appendix E: Annual Progress Meeting Agenda and Report Template Appendix F: Outreach Strategy
3.3 Multi-Jurisdictional Participation
In the 2021 MJHMP update, the following jurisdictions participated in the planning process and will be adopting the updated plan following FEMA approval. All incorporated cities in the County participated in this planning process. As noted previously, the cities of Dos Palos, Gustine, and Merced are new to the multi-jurisdictional planning process.
Lead Jurisdiction:
Ɣ Merced County
Municipalities:
Ɣ City of Atwater
Ɣ City of Dos Palos
Ɣ City of Gustine
Ɣ City of Livingston
Ɣ City of Los Banos
Ɣ City of Merced
The DMA planning regulations and guidance stress that each local government seeking FEMA approval of their mitigation plan must participate in the planning effort in the following ways:
Ɣ Participate in the process as part of the HMPT
Ɣ Detail areas within the planning area where the risk differs from that facing the entire area Ɣ Identify potential mitigation actions
Ɣ Formally adopt the plan
For the Merced County planning area’s HMPT, “participation” meant the following:
Ɣ Providing facilities for meetings
Ɣ Attending and participating in the HMPT meetings
Ɣ Completing and returning Wood Plan Update Guide worksheets Ɣ Collecting and providing other requested data (as available) Ɣ Identifying mitigation actions for the plan
Ɣ Reviewing and providing comments on plan drafts and jurisdictional annexes Ɣ Informing the public, local officials, and other interested parties about the planning process and providing opportunity for them to comment on the plan
Ɣ Coordinating, and participating in the public input process Ɣ Coordinating the formal adoption of the plan by the governing boards The County and all jurisdictions with annexes to this plan and seeking FEMA approval met all of these participation requirements. In most cases one or more representatives for each jurisdiction attended the multi-jurisdictional webinars/meetings described in Table 3-3 Schedule of Planning Meetings and brought together a local planning team to help collect data, identify mitigation actions and implementation 2021 Merced County Hazard Mitigation Plan
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strategies, and review and provide data on annex drafts. In some cases, the jurisdictions had limited capacity to attend or had conflicts with HMPT meetings; in these cases, alternative forms of communication were used to provide input into the process, and some instances a representative from a different jurisdiction’s department attended the HMPT meeting on behalf of the main representative.
Appendix B provides additional information and documentation of the planning process.
3.4 Planning Process
Wood established the planning process for the Merced County MJHMP using the DMA planning requirements and FEMA’s associated guidance. The original FEMA planning guidance is structured around a four-phase process:
Ɣ Organize Resources
Ɣ Assess Risks
Ɣ Develop the Mitigation Plan
Ɣ Implement the Plan and Monitor Progress
Into this process, Wood integrated a more detailed 10-step planning process used for FEMA’s CRS and FMA programs. Thus, the modified 10-step process used for this plan meets the requirements of major grant programs including: FEMA’s HMGP, PDM program, FMA Program, and flood control projects authorized by the U.S. Army Corps of Engineers.
In 2013, FEMA released the Local Mitigation Planning Handbook that has become the official guide for local governments to develop, update and implement local mitigation plans. While the requirements under §201.6 have not changed, the Handbook provides guidance to local governments on developing or updating hazard mitigation plans to meet the requirements under the Code of Federal Regulations (CFR) Title 44 – Emergency Management and Assistance §201.6, Local Mitigation Plans for FEMA approval and eligibility to apply for FEMA HMA grant programs. It also offers practical approaches, tools, worksheets and local mitigation planning examples for how communities can engage in effective planning to reduce long-term risk from natural hazards and disasters. The Handbook complements and liberally references the Local Mitigation Plan Review Guide (October 1, 2011), which is the official guidance for federal and state officials responsible for reviewing local mitigation plans in a fair and consistent manner.
Table 3-2 shows how the modified 10-step process fits into FEMA’s four-phase process, and how these elements correspond to the tasks in the FEMA Mitigation Planning Handbook.
Table 3-2 Merced County Hazard Mitigation Planning Process FEMA’s 4-Phase DMA Process Modified 10-Step CRS Process FEMA Local Mitigation Planning Handbook Tasks
1) Organize Resources
201.6(c)(1) 1) Organize the Planning Effort 1: Determine the planning area and resources
201.6(b)(1) 2) Involve the Public 2: Build the planning team - 44 CFR 201.6 (C)(1)
201.6(b)(2) and (3) 3) Coordinate with Other
Departments and Agencies
3: Create an outreach strategy - 44 CFR
201.6(b)(1)
4: Review community capabilities - 44
CFR 201.6 (b)(2)&(3)
2) Assess Risks
201.6(c)(2)(i) 4) Identify the Hazards
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FEMA’s 4-Phase DMA Process Modified 10-Step CRS Process FEMA Local Mitigation Planning Handbook Tasks
201.6(c)(2)(ii) 5) Assess the Risks
5: Conduct a risk assessment - 44 CFR
201.6 (C)(2)(i) 44 CFR
201.6(C)(2)(ii)&(iii)
3) Develop the Mitigation Plan
201.6(c)(3)(i) 6) Set Goals 6: Develop a mitigation strategy - 44 CFR 201.6(c)(3)(i); 44 CFR 201(c)(3)(ii)
and 44 CFR 201.6(c)(3)(iii)
201.6(c)(3)(ii) 7) Review Possible Activities
201.6(c)(3)(iii) 8) Draft an Action Plan
4) Implement the Plan and Monitor Progress
201.6(c)(5) 9) Adopt the Plan 7: Review and adopt the plan 201.6(c)(4) 10) Implement, Evaluate, and
Revise the Plan
8: Keep the plan current
9: Create a safe and resilient
community - 44 CFR 201.6(c)(4)
3.4.1 Phase 1: Organize Resources
Planning Step 1: Organize the Planning Effort
The 2021 planning process and update of the LHMP had its roots in the development of a grant application. The County Office OES wrote the grant and in the process solicited commitments from local government jurisdictions that were interested in participating. With an understanding of the number of jurisdictions and their commitment to participate, the grant application was approved and awarded to the County in 2019.
Wood worked with the County to get organized for the plan update. Organizational efforts were initiated with the County and participating jurisdictions in December 2020 to inform and educate the plan participants of the purpose and need for updating the countywide hazard mitigation plan. An initial meeting between Wood and County OEM was held to discuss the organizational aspects of this plan update process. Invitations to the kickoff meeting for this plan update were extended to key County departments, the six incorporated communities, and representatives from special districts for the County and municipalities, as well as to other federal, state, and local stakeholders that might have an interest in participating in the planning process. Representatives from participating jurisdictions and HMPT members to the 2014 plan were used as a starting point for the invite list, with additional invitations extended as appropriate throughout the planning process. The list of initial invitees is included in Appendix A.
Representatives from the following County and municipal departments participated on the HMPT and the development of the plan update. A list of specific HMPT representatives is included in Appendix A. Other local, state, federal, and private stakeholders invited to participate in the HMPT are discussed under Planning Step 3.
Merced County
Ɣ Office of Emergency Management
Ɣ GIS
Ɣ Office of Education
Ɣ Division of Environmental Health
Ɣ County Counsel
Ɣ Community and Economic Development
Ɣ Fire Department
Ɣ Executive Office
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Ɣ IT Department
Ɣ Public Works Department
Ɣ Agriculture Commissioner
Ɣ Food Bank
City of Atwater
Ɣ City Manager
Ɣ Police Department
Ɣ Fire Department
City of Dos Palos
Ɣ Police Department
City of Gustine
Ɣ Police Department
City of Livingston
Ɣ Public Works
City of Los Banos
Ɣ Community and Economic Development
Ɣ Fire Department
City of Merced
Ɣ Fire Department
Planning Meetings
The planning process officially began with a kickoff meeting on December 16, 2020. The meeting covered the scope of work and an introduction to the DMA requirements. Participants were provided with a Local Hazard Mitigation Plan Update Workbook, which included worksheets to facilitate the collection of information necessary to support update of the plan. Using FEMA guidance, Wood designed these worksheets to capture information on past hazard events, identify hazards of concern to each of the participating jurisdictions, quantify values at risk to identified hazards, inventory existing capabilities, and record possible mitigation actions. A copy of Wood’s Local Hazard Mitigation Plan Update Guide for this project is included in Appendix B. The County and each jurisdiction seeking FEMA approval of their plan completed and returned the worksheets in either the Local Hazard Mitigation Plan Update Workbook or shared their most recent Local Hazard Mitigation Plan for incorporation into the plan document.
During the planning process, the HMPT communicated through face-to-face meetings, email, and telephone conversations. A majority of the meetings (3 out of the 4) were held virtually due to social distancing requirements associated with the ongoing COVID-19 pandemic. Draft documents were posted on a Google Drive and in some cases emailed so that the HMPT members could easily access and review them. The HMPT formally met four times during the planning period (December 16, 2020 – June 29, 2021). The purposes of these meetings are described in Table 3-3. The planning consultant sent meeting handouts ahead of time to the participating jurisdictions to review and provide feedback before or at the meeting. In addition to these meetings some jurisdictions held meetings with subcommittees to discuss the needed input for the plan update. In a couple cases some municipalities were not able to attend the planning workshops due to scheduling conflicts or limited staff capacity. Fire Captain and Assistant Director of County OES and the planning consultant worked with the jurisdictions individually in those cases to obtain necessary information and input into the planning process. This was done through direct 2021 Merced County Hazard Mitigation Plan
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emails from the planning consultant and follow-up phone conversations with the consultant and County OES where necessary.
Table 3-3 Summary of Planning Meetings
Meeting
Number
Meeting Topic Date Location
1 Kickoff/Planning Team Roles and Expectations December 16, 2020 Virtual/Webinar
– Microsoft
Teams
2 Hazard identification and Risk Assessment March 24, 2021 Virtual/Webinar
– Microsoft
Teams
3 Mitigation Strategy and Goals Update May 13, 2021
Virtual/Webinar
– Microsoft
Teams
4 Mitigation Strategy Refinement June 29, 2021 County EOC – Atwater
Meeting #1 – Kickoff Meeting
On December 16, 2020, the Planning Team convened virtually to discuss the process for completing the update of this plan. The kickoff meeting was well attended with 23 individuals present. The audience was a mix of county departments, local governments, special districts and stakeholders. A complete list of those in attendance at the kickoff meeting can be found in the sign-in sheets in Appendix B.
Following introductions, Wood reviewed the DMA requirements and the suggested planning process to follow to meet the requirements as well as the expected schedule of the process. The roles of the HMPT and stakeholder was discussed including the participation requirements for the different roles.
During the kickoff meeting the Planning Team validated the identified hazards within the 2014 plan with minor revisions and collaboratively prioritized the hazards for the purpose of identifying which are “of most concern” to the County. More details are included in Section 4: Risk Assessment.
The group also discussed other agencies that should be part of this planning process, as well as related planning efforts to be coordinated with and recent studies to be incorporated. Part of this discussion was also related to creating a public outreach strategy to involve the public throughout the planning process.
This outreach strategy is included in Appendix F.
The kickoff meeting ended with Wood sharing handouts to assist in the planning process. These handouts included the Local Hazard Mitigation Plan Update Workbook which outlined data collection needs for each participating jurisdiction.
Meeting #2 – Risk and Goals
On March 24, 2021, the HMPT convened virtually to discuss the results of the risk and vulnerability assessment. Forty-one (41) members of the HMPT were present for the discussion. Wood began the meeting with a presentation on the results the risk assessment for natural hazards, results for hazardous material incidents were presented at the next meeting. The group went through each hazard together and discussed the results as well as shared any local insight to inform the HIRA update. Refer to the meeting summary in Appendix B for notes related to each hazard discussed. Part of this discussion was also related to development trends.
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Following the discussion on the results of the risk assessment, Wood explained this update process provides an opportunity to review the previous plan’s goals to determine if they are still valid, comprehensive, and reflect current priorities and updated risk assessment. The group was also encouraged to share their jurisdiction’s goal statements with their local planning teams prior to the next meeting to discuss if changes are necessary.
Wood shared with group that the online public survey had been opened and already received 30 responses at that time. A link was shared with the HMPT to easily distribute by email and for posting on each of the participating jurisdiction’s websites and MJHMP webpages. The meeting ended with a review of the next steps and planning process schedule.
Meeting #3 – Mitigation Strategy and Goals Update
The HMPT convened virtually on May 13, 2021 with 28 people participating to update the plan’s mitigation strategy. The group finalized the plan’s goals and objectives (Step 6) and discussed the criteria for mitigation action selection and prioritization using a worksheet provided by Wood. The group reviewed each possible new mitigation action and additional details were provided by the Planning Team (Step 7). The meeting ended with a review of the next steps and planning process schedule. Wood provided the Planning Team with a link to an online form to submit new mitigation actions. During the Planning Team review of the full plan, each member was provided a handout on prioritizing new mitigation actions and asked to focus on prioritizing each new mitigation action for their jurisdiction.
Meeting #4 – Mitigation Strategy Refinement
On June 29, 2021, the HMPT convened in person to identify new mitigation actions to include in the updated plan. This encompassed a review of possible mitigation activities, alternatives, and related climate adaptation strategies. The group also discussed criteria for mitigation action selection and prioritization.
This was followed by a brainstorming session to elicit the development of new mitigation actions. Entities responsible for new mitigation action implementation were identified. The HMPT completed a sticky dot exercise to prioritize the new mitigation actions. Mitigation action worksheets were also re-distributed to allow additional details to be added following the workshop.
Planning Step 2: Involve the Public
Involving the public assures support from the community at large and is a required part of the planning process per the DMA 2000. Early discussions with Merced County and input received in the first HMPT meeting established the initial plan for public involvement in the plan update. Public outreach began with the creation of an online public survey that was shared with each participating jurisdiction to post on their websites and disseminate via email to local stakeholders. The public outreach activities described here were conducted with participation from and on behalf of all jurisdictions participating in this plan.
Throughout the planning process public workshops were held to inform the public of the purpose of the DMA and the hazard mitigation planning process for the Merced County planning area. At each workshop the public in attendance were provided comment cards to leave any comments related to the County’s MJHMP as well as provide their contact information if they would like to receive ongoing updates and information related to the planning process.
At the kickoff meeting, the HMPT discussed additional options for public involvement and agreed to an approach using established public information mechanisms and resources within the community.
Additional public involvement activities included press releases, website postings, flyer development and distribution, two public workshops, and the collection of public comments on the draft plan. Details on the outreach methods and approach are also summarized in the Community Outreach Strategy included in Appendix F.
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Online Public Survey
During the plan update’s initial drafting stage, an online public survey was used to gather public input to the Planning Team. The survey provided an opportunity for public input during the planning process, prior to finalization of the plan update. The survey gathered public feedback on concerns about hazards and input on mitigation strategies to reduce their impacts. The survey was released on May 3, 2021 and closed on June 2, 2021. The Planning Team provided links to the public survey by distributing it using social media, email, and posting the link on websites. A link to the survey was also posted on some of the participating jurisdictions’ websites as well as through social media posts; screenshots from both can be found in Appendix B. A total of 290 people filled out the survey online. Results showed that the public perceives the most significant hazards to be drought, extreme temperatures, pandemic/epidemic, and climate change. Figure 3-1 shows the results of question 4 of the survey which asked the public’s opinion on what mitigation actions that should have the highest priority in the updated hazard mitigation plan.
Wildfire fuels treatment projects, forest health/watershed protection, water conservation, evacuation route development and public health incident preparedness were cited as the most popular mitigation actions.
This information was shared with the HMPT during the update of the mitigation strategy to consider when evaluating hazard rankings and as a source of potential mitigation ideas. A summary of all the survey data and documentation of the public feedback can be found in Appendix B.
Figure 3-1 Results from Question 4: The fo llowing types of mitigation actions may be considered in Merced County. Please indicate the types of mitigation actions that you think should have the highest priority in the Merced County Multi- Jurisdictional Hazard Mitigation Plan.
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Online Public Workshops
Two online public workshop was held during the planning process to inform the public, receive input to integrate into the plan update, and keep the public updated on the progress being made in the planning process. Both workshops were held virtually as webinars due to social distancing requirements associated with the ongoing COVID-19 pandemic.
The first workshop took place on May 12, 2021 through Facebook Live. The workshop introduced the public to the hazard mitigation planning process for the County’s Plan Update and answered any questions and gather public input to be integrated into the plan update. In addition, it was an opportunity to help staff identify risks, hazards and vulnerabilities from the public’s perspective. At the end of the first workshop over 300 individuals participated in the virtual workshop by either logging on and briefly viewing the live workshop. Members of the public were able to submit comments verbally or via the chat function. The HMPT received four comments from the meeting that helped to inform the group on the public initial thoughts on hazard mitigation and hazards in their community. The recording of the meeting was subsequently posted on the County’s Facebook Webpage, where it has had an additional 1,985 views as of June 2, 2021, of which 1,020 views were 3-second video views of the workshop recording.
The second public workshop took place on September 22, 2021 while the draft plan was out for public review. The workshop was noticed with a press release and social media postings. The workshop was online using MS Teams and was simultaneously broadcasted as a Facebook Live event by the County. The second virtual public workshop was an opportunity to learn more about the updated draft MJHMP including the planning process, the hazards assessed, and the mitigation actions proposed in the MJHMP.
Following the public workshop was an opportunity for the public to comment on the draft MJHMP. Nine persons attended the Teams session. There were no comments received during the workshop. The recording of the meeting was subsequently posted on the County’s Facebook Webpage. The County encourages participation and feedback by attending the public workshop, visiting the County’s Project Webpage, and/or commenting on the Public Review Draft MJHMP Critical Facilities Database Website and Coordination
A unique aspect of the 2021 plan update process was the development of a web-based mapping application by the County in collaboration with Wood. This project webpage served multiple purposes: a planning process backgrounder for the HMPT and public with public survey links; a GIS/map based – interactive storyboard (i.e., Experience Builder Application) to communicate the highlights of the risk assessment, including interactive hazard maps; a web-based method for collecting, validating, updating and maintaining critical facilities for the plan; and finally a platform to make the Plan a “living document” moving forward, providing a basis for the plan maintenance and continuous updating of critical facility data. A screenshot of the project webpage is shown in Figure 3-2 below. The website and critical facilities database was completed with assistance from a professor and students at California State University, Stanislaus.
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Figure 3-2 Merced County’s MJHMP Webp age and Information Resource Portal
Source: Merced County 2021
Each participating jurisdiction’s assistance was requested to validate the critical facility GIS data that has been collected. There were two primary aspects of this: data completeness/correctness and alignment/classification with FEMA Lifelines framework. Through a password protected interface built with the ArcGIS Online Experience Builder application jurisdictions were able to browse map based critical facility data, edit descriptive attributes, and add new point data. This process further engaged participating jurisdictions who saw the value of the MJHMP and long-term use and maintenance of the critical facility data moving forward.
Public Review Period
On September 15-October 6, 2021, a public review draft of this plan was released for comment and made available for download via the County OES website. The draft plan was advertised through social media, mass emailing, and an advertisement through the media mechanisms noted previously. An electronic comment form through Microsoft Forms was provided with the draft plan. Two comments were received, one from a member of the public expressing that the plan was well done, and the other from a representative of the Lower San Joaquin Levee District, who did not have any specific things to note.
Comments received were shared with the HMPT but did not result in changes to the plan. Both comments are documented in Appendix B.
3.4.2 Planning Step 3: Coordinate with Other Departments and Agencies Early in the planning process, state and local agencies and organizations were invited to participate as stakeholders in the process through email. Stakeholders include local and regional agencies involved in hazard mitigation activities or those beyond the County and local government that have the authority to regulate development. The Merced County Cooperator’s List provided the basis for a contact list, which was maintained on a Google Drive by County OES and the planning consultant. Stakeholders could participate in various ways, either by contributing input at HMPT meetings, being aware of planning activities through an email group, providing information to support the effort, or reviewing and commenting on the draft plan. Based on their involvement in other hazard mitigation planning efforts, and status in the County, representatives from the following agencies and organizations were invited to participate as stakeholders in the process by email; an asterisk indicates they participated in HMPT
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meetings. Involvement of local academic institutions include students with California State University, Stanislaus who were tasked to assist with the web-based GIS application for critical facility mapping noted previously. The University of California, Merced was also represented at HMPT meetings. More specific on stakeholder agency representatives can be found in Appendix A and documentation in Appendix B.
Neighboring Counties
Ɣ County of Fresno
Ɣ County of Kings
Ɣ County of Madera*
Ɣ County of Mariposa*
State and Federal Agencies
Ɣ California Office of Emergency Services Region V*
Ɣ California Department of Water Resources*
Ɣ California Department of Parks and Recreation*
Ɣ National Weather Service*
Businesses, Academia, and Private and Non-Profits
Ɣ American Red Cross*
Ɣ University of California, Merced*
Ɣ California State University, Stanislaus*
Ɣ Pacific Gas & Electric (PG&E) *
Ɣ Mercy Medical Center*
Ɣ Merced Irrigation District*
Ɣ Turlock Irrigation District*
Ɣ Merced County Food Bank*
Incorporation or Existing Plans and Other Information
The coordination and synchronization with other community planning mechanisms and efforts are vital to the success of this plan. To have a thorough evaluation of hazard mitigation practices already in place, appropriate planning procedures should also involve identifying and reviewing existing plans, policies, regulations, codes, tools, and other actions are designed to reduce a community’s risk and vulnerability from natural hazards. Merced County uses a variety of mechanisms to guide growth and development.
Integrating existing planning efforts, mitigation policies, and action strategies into this plan establishes a credible, comprehensive document that weaves the common threads of a community’s values together.
The development and update of this plan involved a comprehensive review of existing plans, studies, reports, and initiatives from Merced County and each participating municipality that relate to hazards or hazard mitigation. A high level summary of the key plans, studies and reports is summarized in the table below. Information on how they informed the update are noted and incorporated where applicable.
Table 3-4 Summary of Review of Key Plans, Studies and Reports Plan, Study, Report Name How Plan informed LHMP
Merced County General Plan Provided background information on the county including some information related to jurisdictions. The elements were used to provide information on risk and
vulnerabilities to hazards and the existing policies the County has in place related to hazards and mitigation.
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Plan, Study, Report Name How Plan informed LHMP
Municipal General Plans (including Safety Elements,
Land Use Elements, and Housing Elements)
Informed the municipal annexes and in some cases the
community service district annexes on past hazard
events, mitigation policies, combining designations and existing and projected development
City of Merced 2015 Local Hazard Mitigation Plan Informed the HIRA sections, mitigation action plans and capability assessments for the City of Merced
Merced County Flood Insurance Study Reviewed for information on past floods and flood problems to inform risk assessment (Section 4)
Utilized Digital Flood Insurance Rate Maps effective
2018 State of California Multi-Hazard Mitigation Plan Reviewed information on climate change and hazard assessment data to ensure consistency with this plan
update
Reviewed list of hazards to inform risk assessment
(Section 4)
Reviewed goals for consistency
Turlock Irrigation District Local Hazard Mitigation Plan 2020
Reviewed risk assessment chapter in TLD plan to help
inform the Merced County LHMP update
NOAA National Centers for Environmental Information-
State Climate Summaries
Reviewed information on climate change to inform risk
assessment (Section 4)
California Department of Finance/U.S. Census Bureau,
American Community Survey, 2015-2019
Informed the background on the community including
demographic trends
USDA Risk Management Agency Crop Indemnity
Reports, 2007-2020
Informed the adverse weather section vulnerability
assessment on how crops have been impacted by
weather events in the past. Also informed the Drought
and Agricultural Pests and Disease sections of the HIRA California Climate Adaptation Strategy, 2018 and
California OES Contingency Plan for Excessive Heat
Emergencies (2014)
Informed the Extreme Heat profile and climate change
considerations
Other technical data, reports and studies were reviewed and considered, as appropriate, during the collection of data to support Planning Steps 4 and 5, which include the hazard identification, vulnerability assessment, and capability assessment. Information from the following agencies and groups in were reviewed in the development and update of this plan. Specific references relied on in the development of this plan are also sourced throughout the document as appropriate.
Ɣ California Department of Forestry and Fire Protection Ɣ California Department of Parks and Recreation Office of Historic Preservation Ɣ California Department of Transportation
Ɣ California Department of Public Health
Ɣ California Natural Resources Agency
Ɣ California Department of Water Resources
Ɣ California Geological Survey
Ɣ Merced County Agricultural Department
Ɣ Merced Office of Emergency Services
Ɣ California Water Foundation
Ɣ National Oceanic and Atmospheric Administration National Climatic Data Center Ɣ National Register of Historic Places
Ɣ Natural Resource Conservation Service
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Ɣ National Weather Service
Ɣ U.S. Fish and Wildlife Service
Ɣ U.S. Geological Survey
Ɣ Western Regional Climate Center
Ɣ Center for Western Weather and Water Extremes
Integration of 2014 Plan into Other Plans and Planning Mechanisms While the 2014 MJHMP including jurisdictional annexes for Atwater, Livingston, or Los Banos, or the City of Merced 2015 LHMP, were not specifically incorporated or referenced in county or municipal plans and planning mechanisms, a process to do so with the 2021-2026 plan is outlined in subsection 6.3.3.
Specifically, there is a process noted in both subsection 6.3.3 and corresponding mitigation actions in subsection 5.3 that outline how the County and municipalities can achieve Assembly Bill (AB) 2140 compliance, which recommends adoption by reference or incorporation of the LHMP into the Safety Element of the General Plan. The County was actively coordinating an amendment of the General Plan Safety Element to accommodate this during the finalization of this LHMP in late 2021.
3.4.3 Phase 2: Assess Risks
Planning Step 4: Identify the Hazards
Wood led the HMPT in an effort to review the list of hazards identified in the 2014 plan and document all the hazards that have, or could, impact the planning area, including documenting recent drought, flood, wildfire and winter storm events. Data collection worksheets were used in this effort to aid in determining hazards and vulnerabilities and where risk varies across the planning area. The profile of each of these hazards was then updated in 2019 with information from the HMPT and additional sources. Web resources, existing reports and plans, and existing GIS layers were used to compile information about past hazard events and determine the location, previous occurrences, probability of future occurrences, and magnitude/severity of each hazard. GIS were used to display, analyze, and quantify hazards and vulnerabilities where data permitted. The potential for climate change to affect the frequency and intensity of the hazards was summarized based on latest available science, where applicable. A more detailed description of the HIRA process and the results are included in Section 4: Hazard Identification and Risk Assessment.
Planning Step 5: Assess the Risks
After updating the profiles of the hazards that could affect the County, the HMPT collected information to describe the likely impacts of future hazard events on the participating jurisdictions. This step included two parts: a vulnerability assessment and a capability assessment.
Vulnerability Assessment – Participating jurisdictions updated their assets at risk to natural hazards— overall and in identified hazard areas. These assets included total number and value of structures; critical facilities and infrastructure; natural, historic, and cultural assets; and economic assets. The HMPT also analyzed development trends in hazard areas. The latest DFIRM was used to refine the estimate flood losses during the update, where available for the NFIP participating communities.
Capability Assessment – The HMPT also conducted a capability assessment update to review and document the planning area’s current capabilities to mitigate risk and vulnerability from natural hazards.
By collecting information about existing government programs, policies, regulations, ordinances, and emergency plans, the HMPT can assess those activities and measures already in place that contribute to mitigating some of the risks and vulnerabilities identified. This information for the County is included in Section 6 and in the respective jurisdictional annexes. This addressed FEMA planning task 4: Review community capabilities - 44 CFR 201.6 (b)(2) & (3).
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Results of the risk assessment was presented, and comments discussed at the second HMPT meeting in March 2021. A more detailed description of the risk assessment process and the results are included in Section 4: Hazard Identification and Risk Assessment.
3.4.4 Phase 3: Develop the Mitigation Plan
Planning Step 6: Set Goals
Wood facilitated a discussion session with the HMPT to review the 2014 plan’s goals and objectives. The HMPT discussed definitions and examples of goals, objectives, and actions and considered the goals of the state hazard mitigation plan and other relevant local plans when reviewing and revising the goals and objectives. The resulting updated goals and objectives are presented in Section 5: Mitigation Strategy.
Planning Step 7: Review Possible Activities
Wood facilitated a discussion at an HMPT meeting to review the alternatives for mitigating hazards. This included a brainstorming session with the HMPT to identify a comprehensive range of mitigation actions for each identified hazard, and a method of selecting and defending recommended mitigation actions using a series of selection criteria. More specifics on the process and the results of this collaborative process are captured in Section 5: Mitigation Strategy.
As part of the review of mitigation options long-term climate change adaptation strategies were also discussed. HMPT members were encouraged to incorporate climate change adaptation measures into the mitigation strategy of their respective jurisdictions utilizing resources and guidance available on the Cal- Adapt website.
Planning Step 8: Draft an Action Plan
Based on input from the HMPT regarding the draft risk assessment and the goals and activities identified in Planning Steps 6 and 7, Wood produced a complete first draft of the plan. This complete was shared electronically with the HMPT for review and comment. Other agencies were invited to comment on this draft as well. HMPT and agency comments were integrated into the second draft, which was advertised and distributed to collect public input and comments. Neighboring county emergency managers and interested stakeholders identified under Step 3 were also solicited to provide comments on the draft plan; no comments were received. Wood integrated comments and issues from the public, as appropriate, along with additional internal review comments and produced a final draft for the California Office of Emergency Services and FEMA Region IX to review and approve, contingent upon final adoption by the governing boards of each participating jurisdiction.
3.4.5 Phase 4: Implement the Plan and Monitor Progress Planning Step 9: Adopt the Plan
In order to secure buy-in and officially implement the plan, the plan was adopted by the governing boards of each participating jurisdiction on the dates included in the adoption resolutions in Appendix C:
Approval and Adoption. The final plan will be included in the Safety Element of the County General Plan and result in the County’s eligibility for Assembly Bill (AB) 2140. This adoption makes the jurisdiction eligible for consideration for part or all of its local costs on eligible public assistance to be provided by State share funding through the CDAA.
Planning Step 10: Implement, Evaluate, and Revise the Plan The true worth of any mitigation plan is in the effectiveness of its implementation. Up to this point in the plan update process, all of the HMPT’s efforts have been directed at researching data, coordinating input 2021 Merced County Hazard Mitigation Plan
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from participating entities, and updating and developing appropriate mitigation actions. Each recommended action includes key descriptors, such as hazard(s) addressed, lead manager and priority, to help initiate implementation. An overall implementation strategy is described in Section 6: Plan Adoption, Implementation, and Maintenance.
Finally, there are numerous organizations within the Merced County planning area whose goals and interests’ interface with hazard mitigation. Coordination with these other planning efforts, as addressed in Planning Step 3, is paramount to the ongoing success of this plan and of mitigation in Merced County and is addressed further in Section 6. A plan update and maintenance schedule and a strategy for continued public involvement are also included in Section 6.
Implementation and Maintenance Process: 2014 Plan
The 2014 LHMP included a process for implementation and maintenance which was generally followed, with some variation. Implementation of the plan including the status of mitigation actions is captured in Section 5 and the jurisdictional annexes. In general, the County and participating jurisdictions have made progress in the implementation of the plan. Successes of note are detailed in the mitigation strategy in Section 5. An updated implementation and maintenance section can be referenced in Section 6..
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2021-2026 Update Page 4-1
4 HAZARD IDENTIFICATION AND RISK ASSESSMENT
Requirement §201.6(c)(2)(i):
[The risk assessment shall include a] description of the type, location and extent of all natural hazards that can affect the jurisdiction. The plan shall include information on previous occurrences of hazard events and on the probability of future hazard events.
§201.6(c)(2)(ii):
[The risk assessment shall include a] description of the jurisdiction’s vulnerability to the hazards described in paragraph (c)(2)(i) of this section. This description shall include an overall summary of each hazard and its impact on the community. All plans approved after October 1, 2008 must also address NFIP insured structures that have been repetitively damaged by floods. The plan should describe vulnerability in terms of:
§201.6(c)(2)(ii)(A):
The types and numbers of existing and future buildings, infrastructure, and critical facilities located in the identified hazard areas;
§201.6(c)(2)(ii)(B):
An estimate of the potential dollar losses to vulnerable structures identified in ... this section and a description of the methodology used to prepare the estimate.
§201.6(c)(2)(ii)(C):
Providing a general description of land uses and development trends within the community so that mitigation options can be considered in future land use decisions.
Risk to natural hazards is a combination of hazard, vulnerability and capability. This section of the MHMP will look at both hazards and vulnerability. The risk assessment process identifies and profiles relevant hazards and assesses the exposure to lives, property and infrastructure to these hazards. The goal of the risk assessment is to estimate the potential losses in Merced County from a hazard event. This process also allows communities in Merced County to better understand their potential risk to natural hazards and provides a framework for developing and prioritizing mitigation actions to reduce the risks from future hazard events in Merced County.
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1. Describe Hazards
2. Identify Community Assets
3. Analyze Risks
4. Summarize Vulnerability
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/ŶĞƐƐĞŶĐĞ͕ƚŚĞƌŝƐŬĂƐƐĞƐƐŵĞŶƚĞǀĂůƵĂƚĞƐƉŽƚĞŶƚŝĂůůŽƐƐĨƌŽŵŚĂnjĂƌĚƐďLJĂƐƐĞƐƐŝŶŐƚŚĞǀƵůŶĞƌĂďŝůŝƚLJŽĨƚŚĞĐŽƵŶƚLJ͛Ɛ ƉŽƉƵůĂƚŝŽŶ͕ďƵŝůĚĞŶǀŝƌŽŶŵĞŶƚ͕ĐƌŝƚŝĐĂůfacilities͕ĂŶĚŽƚŚĞƌĂƐƐĞƚƐ͘ĂƚĂĐŽůůĞĐƚĞĚƚŚƌŽƵŐŚƚŚŝƐƉƌŽĐĞƐƐŚĂƐďĞĞ Ŷ ŝŶĐŽƌƉŽƌĂƚĞĚŝŶƚŽƚŚĞĨŽůůŽǁŝŶŐƐĞĐƚŝŽŶƐŽĨƚŚŝƐƐĞĐƚŝŽŶ͗ Subsection 4.1: Hazard Identification - identifies the hazards that threaten the Planning Area and describes why some hazards have been omitted from further consideration.
Subsection 4.2: Asset Summary - describes the methodology for inventorying assets as the basis for determining vulnerability of the planning area to the identified hazards.
Subsection 4.3: Hazard Analysis and Risk Assessment - discusses the threat to the Planning Area and describes previous occurrences of hazard events and the likelihood of future occurrences (2013 FEMA Local Mitigation Planning Handbook Risk Assessment Step 1). It also includes a vulnerability assessment considering assets at risk, critical facilities, and development trends (2013 FEMA Local Mitigation Planning Handbook Risk Assessment Steps 2, 3 and 4).
This risk assessment covers the entire geographical area of Merced County. Since this plan is a multi- jurisdictional plan, the HMPC was required to evaluate how the hazards and risks vary from jurisdiction to jurisdiction. While these differences are noted in this section, they are expanded upon in the annexes of the participating jurisdictions. If no additional data is provided in an annex, it should be assumed that the risk and potential impacts to the affected jurisdiction are similar to those described here for the entire Merced County planning area.
4.1 Hazard Identification
The San Joaquin Valley region and Merced County is susceptible to a number of hazards. This MHMP profiles the most significant of these hazards. In the early meetings with Merced County and the Planning Team, data was reviewed from the following sources on hazards affecting the county, those sources were:
Federal and State Disaster Declaration History, the State of California Hazard Mitigation Plan (2018), the Health Safety Element of the Merced County 2035 General Plan (2012), and interviews of staff that live and work in Merced County.
Using existing natural hazards data and input gained through planning meetings during both the 2014 HMP and 2021 update, the HMPC agreed upon a list of hazards that could affect Merced County. The following table explains the changes in the hazards profiled in 2014 and the 2021 update.
Table 4-1 Updates to Hazards Profiled, 2014 Plan and 2021 Update 2014 Hazards 2021 Hazards Comments
Earthquake Earthquake No Changes.
Floods (including dam failures) Flooding and Levee Failure Broke out dam failures as its own sections:
“dam incidents”. Added levee failure to
section due to the large number of levees
in the County.
Severe Weather (including Drought,
Extreme Heat, Freeze)
Severe Weather: Dense Fog,
Extreme Heat, Freeze, Heavy
Rain and Wind
Broke out drought into its own section.
Added dense fog, wind and heavy rain to
severe weather.
Wildfire Wildfire No Changes.
Agriculture Pest and Disease New in 2021. Added due to significant agricultural industry in the County and the
impacts to the local economy.
Cyber Attacks New in 2021. Added due to worldwide
uptick in number and extent of attacks.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-3
2014 Hazards 2021 Hazards Comments
Dam Incidents Identified in General Plan Safety Element.
Includes flooding from excess releases.
Drought Previously part of severe weather section.
Profiled separately due to the unique
nature of the hazard and different
consequences.
Hazardous Materials New in 2021. Added due to potential for fixed facility and transportation incidents.
Landslide New in 2021. Added due to presence of
landslide susceptible terrain in the
western county.
Pandemic/Epidemic New in 2021. Included due to extent of impacts associated with 2020 COVID 19
Pandemic.
Subsidence New in 2021. Included due to history of
subsidence related to groundwater
withdrawals and impacts to canal and
levee infrastructure.
The 2021 HMP update included a significant re-evaluation of the hazards with the latest, best available data. Hazards data from Merced County, California Governor’s OES, FEMA, the National Oceanic and Atmospheric Administration, and many other sources were examined to assess the significance of these hazards to the planning area. The update process included a comprehensive, parcel-level risk analysis with GIS where available data permitted. Many new maps and tables were added that capture the potential losses.
4.1.1 Overall Hazard Significance Summary
Overall hazard significance was based on a combination of Geographic Area, Probability of Future Occurrence and Potential Magnitude/Severity as defined below. The individual ratings are based on or interpolated from the analysis of the hazards in the sections that follow. During the 2021 Merced County HMP update the individual ratings and significance of the hazards was revisited and updated. Public concern was also considered via input at public webinars and an online survey.
Table 4-2 Merced County Hazard Significance
Hazard Geographic Area
Probability of
Future
Occurrence
Magnitude/Severity
(Extent)
Overall
Significance
Agriculture Pest and
Disease Extensive Likely Critical Medium
Cyber Attack Significant Likely Critical Medium
Dam Incidents Significant Occasional Catastrophic Medium Drought Extensive Likely Critical High
Earthquake Significant Unlikely Critical Medium
Flood and Levee
Failure Extensive Likely Catastrophic High
Hazardous Materials Limited Highly Likely Negligible Low Landslide Limited Occasional Limited Low
Pandemic/Epidemic Extensive Occasional Catastrophic High DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-4
Hazard Geographic Area
Probability of
Future
Occurrence
Magnitude/Severity
(Extent)
Overall
Significance
Severe Weather:
Dense Fog Extensive Highly Likely Critical High
Severe Weather:
Freeze Extensive Highly Likely Critical High
Severe Weather: Heat Extensive Highly Likely Critical High Severe Weather:
Heavy Rain Extensive Highly Likely Critical High
Severe Weather: High
Wind/Tornado Extensive Highly Likely Critical High
Subsidence Extensive Likely Negligible Low
Wildfire Significant Likely Limited Medium
Geographic Area
Limited: Less than 10% of planning area
Significant: 10-50% of planning area
Extensive: 50-100% of planning area
Probability of Future Occurrences
Highly Likely: Near 100% chance of occurrence
in next year or happens every year.
Likely: Between 10 and 100% chance of
occurrence in next year or has a recurrence
interval of 10 years or less.
Occasional: Between 1 and 10% chance of
occurrence in the next year or has a recurrence
interval of 11 to 100 years.
Unlikely: Less than 1% chance of occurrence in
next 100 years or has a recurrence interval of
greater than every 100 years.
Magnitude/Severity (Extent)
Catastrophic—More than 50 percent of property severely
damaged; shutdown of facilities for more than 30 days; and/or multiple deaths
Critical—25- 50 percent of property severely damaged; shutdown of facilities for at least two weeks; and/or injuries and/or illnesses result in permanent disability
Limited—10-25 percent of property severely damaged;
shutdown of facilities for more than a week; and/or
injuries/illnesses treatable do not result in permanent disability Negligible— Less than 10 percent of property severely damaged, shutdown of facilities and services for less than 24 hours; and/or injuries/illnesses treatable with first aid
Significance
Low: minimal potential impact
Medium: moderate potential impact
High: widespread potential impact
4.1.2 Non-Profiled Hazards
dŚĞWůĂŶŶŝŶŐdĞĂŵƌĞǀŝĞǁĞĚĚĂƚĂĂŶĚĚŝƐĐƵƐƐĞĚƐĞǀĞƌĂůŽƚŚĞƌŚĂnjĂƌĚƐ͕ǁŚŝĐŚǁĞƌĞĞůŝŵŝŶĂƚĞĚĨƌŽŵĨƵƌƚŚĞƌ ĚŝƐĐƵƐƐŝŽŶďĞĐĂƵƐĞƚŚĞLJŽĐĐƵƌƌĂƌĞůLJĂŶĚͬŽƌƚŚĞŝƌŝŵƉĂĐƚƐĂƌĞŶŽƚƐŝŐŶŝĨŝĐĂŶƚ͘dŚĞůŝƐƚďĞůŽǁĚĞƚĂŝůƐƚŚĞƐĞŚĂnjĂƌĚƐ ĂŶĚƉƌŽǀŝĚĞƐĂďƌŝĞĨĞdžƉůĂŶĂƚŝŽŶĨŽƌƚŚĞŝƌŽŵŝƐƐŝŽŶĨƌŽŵĨƵƌƚŚĞƌƉƌŽĨŝůŝŶŐ͘ Ɣ Avalanche - Snowfall is extremely rare to nonexistent across the planning area.
Ɣ Coastal Erosion/Storm - Hazard does not occur due to distance from coasts and ocean.
Ɣ Hailstorm - Severe thunderstorms during which hail normally occurs are rare.
Ɣ Hurricane - Hazard does not occur due to distance from ocean.
Ɣ Tsunami - Hazard does not occur due to distance from ocean.
Ɣ Volcano - The U.S. Geological Survey does not include Merced County in their map of areas identified as subject to hazards from potential eruptions in California.
The Planning Team acknowledges there are other human caused hazards that can affect the County. They are recognized here, with notes below how they are considered as consequences of other hazards or addressed in other planning mechanisms:
Ɣ Civil Unrest and Terrorism – More commonly addressed in the local emergency operations plans; an uptick in social equity-related incidents and far-right extremism has been noted in recent years.
Ɣ Power outages/Utility Failure – This is addressed as a consequence of other hazards such as severe weather, earthquakes, and wildfires.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-5
Ɣ Transportation Hazards – Transportation safety is typically addressed in other planning mechanisms.
Noted as a consequence of other hazards where applicable, e.g. Severe Weather: Fog, earthquakes, floods.
4.1.3 Disaster Declaration History
One method to identify hazards is to look at the events that have triggered federal and/or state disaster declaration that included Merced County. Federal and state disaster declarations may be granted when the severity and magnitude of an event surpasses the ability of the local government to respond and recover. Disaster assistance is supplemental and sequential. When the local government’s capacity has been surpassed, a state disaster declaration may be issued, allowing for the provision of state assistance.
Should the disaster be so severe that both the local and state governments’ capacities are exceeded, a federal emergency or disaster declaration may be issued allowing for the provision of federal assistance.
In other words, a presidential disaster declaration puts federal recovery programs in place to help disaster victims, business, and public agencies.
The federal government may issue a disaster declaration through FEMA, the U.S. Department of Agriculture (USDA), or the Small Business Administration. FEMA also issues emergency declarations, which are more limited in scope and without the long-term federal recovery programs of major disaster declarations (Farm Service Agency 2018). The quantity and types of damage are the determining factors.
This section focuses on state and federal disaster and emergency declarations.
The communities throughout Merced are among the many in California that are susceptible to disaster.
Details on federal and state disaster declarations were obtained by the HMPC, FEMA, and the California OES and compiled in chronological order in Table 4-3. A review of state and federal declared disasters indicates that Merced County received 18 proclamations between 1950 and March 2020. Of the 18 state declarations, seven were associated with flooding; two were for drought (not including declaration issued by the USDA); three were for freeze; and two were for the COVID-19 pandemic.
This disaster history (combined federal and state) suggests that Merced County experiences a major event worthy of a disaster declaration about every 4 years. The County has a 26 percent chance of receiving a disaster declaration in any given year. With the exception of the declarations for drought and the COVID- 19 pandemic, every declaration resulted directly or indirectly from severe weather. Further, a review of these events helps Merced County, and its jurisdictions identify risk reduction targets and ways to improve capabilities to avoid large-scale hazard events in the future.
The following table lists the declarations where Merced County was included in federal and/or state disaster declarations from 1950 to the present.
Table 4-3 Merced County Disaster Declaration History 1950-present Hazard Type Disaster Name Disaster Number
Flood 1950 Floods (Statewide) OCD50-01
Flood 1955 Floods (Statewide) DR-47
Flood 1969 Storms, Flooding DR-253
Freeze 1972 Freeze
Drought California Drought January 1976-77 3023
Severe Storms 1983 Coastal Storms, Floods, Slides, &
Tornadoes DR-677
Freeze 1990 Freeze DR-894
Flood 1995 Late Winter Storms DR-1046
Flood 1997 January Floods DR-1155
Flood 1998 El Niño Floods DR-1203
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Hazard Type Disaster Name Disaster Number
Freeze 1998 Freeze DR-1267
Hurricane Katrina Evacuation California Hurricane Katrina Evacuees September 2005 EM-3248
Flood 2006 June Storms DR-1646
Freeze 2007 Severe Freeze DR-1689
Drought Central Valley Drought 2008 GP 2008-03
Drought Drought State of Emergency Statewide 2014 B-17-2014 Flooding and Mudslides January 2017 Storms DR-4301
Pandemic California COVID-19 EM-3428
Pandemic California COVID-19 Pandemic DR-4482
Source: Merced OES, Cal OES and FEMA
Since 2012, there have been 18 disaster designations issued by the Secretary of Agriculture in Merced County, 15 of which were for drought and three were for hail, excess rain, cold temperatures, and high winds. Of the drought designations, 11 are classified as “Drought-Fast Track” Secretarial disaster designations. According to the Secretary of Agriculture, a Fast Track designation is for a severe drought and provides an automatic designation when during the growing season any portion of the county meets the severe drought intensity value for eight consecutive weeks. Refer to the drought hazard profile for more information of disaster declarations from the Secretary of Agriculture related to drought events.
Table 4-4 USDA Agricultural Declarat ions in Merced County, 2012-2020 Year Hazard Designation
Number Approval Date
2012
Drought-Fast Track S3268 7/12/2012
Hail, rain, cold temperatures S3320 8/3/2012
Drought S3379 9/5/2012
Drought S3452 12/19/2012
2013
Drought-Fast Track S3491 2/27/2013
Drought-Fast Track S3511 4/24/2013
Drought-Fast Track S3547 7/3/2013
Drought-Fast Track S3558 7/31/2013
2014 Drought-Fast Track S3626 1/15/2014
Drought S3743 9/17/2014
2015 Drought-Fast Track S3784 2/4/2015
Drought S3943 12/23/2015
2016
Drought-Fast Track S3952 2/17/2016
Severe weather including excessive
rainfall and high winds S4164 3/31/2017
2017 Drought-Fast Track S4144 2/23/2017
2019 Excessive rain and hail S4657 3/11/2020
2020 Drought-Fast Track S4697 6/16/2020
Source: USDA Secretary of Agriculture
4.1.4 Climate Change Considerations Summary
Merced County is part of the San Joaquin Valley part of California’s Central Valley. The region is known as one of the world’s most productive agricultural regions and is also vulnerable to the impacts on climate change. The following are highlights from California’s Fourth Climate Change Assessment, San Joaquin Valley Region Report (Preview), of projected impacts to the State of California and the Central Valley due to climate change:
Ɣ Acceleration of higher temperatures across California.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-7
Ɣ More intense and frequent heat waves.
Ɣ Increasing evapotranspiration.
Ɣ More intense and frequent droughts.
Ɣ More intense rainstorms.
Ɣ Higher frequency of catastrophic floods.
Ɣ More severe and frequent wildfires.
Ɣ Declining and change in timing of snowmelt.
Ɣ Increased susceptibility to rain-on-snow events from atmospheric rivers.
Ɣ Increased stream temperatures resulting in decreased water quality.
The important consideration for hazard mitigation is that climate change is exacerbating the hazards which are already identified and profiled. Additional specifics associated with the hazards are discussed in the Climate Change Considerations portion of each hazard profile.
4.1.5 Overview of Hazard Identification and Risk Assessment Subsection 4.3 contains detailed hazard profiles for the identified hazards. Each hazard profile includes the following subsections:
Ɣ Hazard/Problem Definition—This se ction gives a description of the hazard and associated issues followed by details on the hazard specific to the Merced County planning area.
Ɣ Geographic Area – This section gives a spatial description of the potential location or areas of Merced County where the hazard expected to impact.
Ɣ Extent (Magnitude/Severity)– This section gives a description of the potential strength or magnitude of the hazard as it pertains to Merced County.
Ɣ Previous Occurrences—This section contains info rmation on historical incidents, including impacts where known. Historical incident worksheets were used to capture information from participating jurisdictions on past occurrences.
Ɣ Probability of Future Occurrence—The frequency of pa st events is used in this section to gauge the likelihood of future occurrences. Where possible, frequency was calculated based on existing data. It was determined by dividing the number of events observed by the number of years on record and multiplying by 100. This gives the percent chance of an event happening in any given year (e.g., three droughts over a 30-year period equates to a 10 percent chance of a drought in any given year). The likelihood of future occurrences is categorized into one of the following classifications:
- Highly Likely — Near 100 percent chance of occurrence in next year or happens every year. - Likely — Between 10 and 100 percent chance of o ccurrence in next year or has a recurrence interval of 10 years or less.
- Occasional — Between 1 and 10 percent chance of occurrence in the next year or has a recurrence interval of 11 to 100 years.
- Unlikely — Less than 1 percent chance of occurr ence in next 100 years or has a recurrence interval of greater than every 100 years.
Ɣ Climate Change Considerations - This describes the potential for climate change to affect the frequency and intensity of the hazard in the future.
Ɣ Vulnerability - Following the hazard profiles is a vulnerability assessment for each identified hazard.
The assessment was conducted through the study of potential impacts to the following specific sectors:
- General Property
- People
- Critical Facilities and Infrastructure
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-8
- Economy
- Historic, Cultural, and Natural Resources
- Future Development
- Risk Summary - Each vulnerability assessment includes a risk summary of the key issues/problems based on threat, vulnerability and consequence to the planning area and jurisdictions from the specific hazard.
Data used to support this assessment included the following:
Ɣ County GIS data (hazards, base layers, and assessor’s data); Ɣ Statewide GIS datasets to support mitigation planning; Ɣ State of California Hazard Mitigation Plan 2018;
Ɣ Merced County Hazard Mitigation 2014;
Ɣ Jurisdictional Hazard Mitigation Plans;
Ɣ CAL FIRE datasets;
Ɣ California’s Fourth Climate Change Assessment
Ɣ Written descriptions of inventory and risks provided by the jurisdictions; Ɣ Online data sources (cited where applicable);
Ɣ Data and information from existing plans and studies; and Ɣ Input from planning team members and staff from the County and local, state, and federal agencies.
Asset Summary
4.1.6 Assets Exposure
As a starting point for analyzing the Planning Area’s vulnerability to identified hazards, the HMPC used a variety of data to define a baseline against which all disaster impacts could be compared. If a catastrophic disaster was to occur in the Planning Area, this section describes significant assets exposed or at risk in the Planning Area. Data used in this baseline assessment included:
Ɣ Total assets at risk;
Ɣ Critical facility inventory;
Ɣ Cultural, historical, and natural resources; and
Ɣ Population growth and land use/development trends.
Total Assets at Risk
Building value assessments in this plan are based on data from the Merced County’s Assessor’s Office.
This data provided the baseline for an inventory of the total exposure of developed properties within the county and helps to ensure that the updated HMP reflects changes in development. It is important to note that depending on the nature and type of hazard event or disaster, it is generally the value of the infrastructure or improvements to the parcels that are of concern or at risk. Generally, the land itself is not a total loss, but may see a reduction in value. Thus, the parcel analysis excludes land value.
Parcel Exposure and Preparations for Analysis
Merced County Assessor data was used to inventory the total number and types of parcels with improvements, defined as parcels with an improvement value greater than zero, in the County. Building content values were estimated based on the following formulas based on FEMA/Hazus methods: a) Residential properties received content values worth 50% of the improved values; b) Agricultural, Commercial, Exempt, and Mixed Use related properties received content values worth 100% of the improved values; and c) Industrial properties received content values worth 150% of the improved values.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-9
Adding up these content and original improved values yields the Total Value of Improved Parcels, which is an estimation of the total property exposure within the County. Building counts were based on an address point database to further refine the number of structures, as one parcel may have multiple buildings.
Table 4-6 summarizes the property inventory for the County and each participating jurisdiction with detail by property type. Table 4-5 shows the total property inventory from the Assessor’s Office.
Table 4-5 Total Exposure Summary by Jurisdiction
Jurisdiction Improved
Parcel Count
Building
Count Improved Value Estimated
Content Value Total Value
Atwater 7,634 9,654 $1,391,376,798 $826,122,017 $2,217,498,815 Dos Palos 1,774 2,001 $202,169,557 $111,638,513 $313,808,070 Gustine 1,874 2,109 $290,346,103 $174,766,468 $465,112,571 Livingston 3,344 4,007 $708,187,135 $500,444,666 $1,208,631,801 Los Banos 12,253 13,111 $2,492,207,313 $1,427,441,289 $3,919,648,602 Merced 22,362 31,744 $4,753,631,582 $3,092,973,003 $7,846,604,585 Unincorporated 28,343 35,327 $5,628,897,061 $4,421,594,611 $10,050,491,672 Total 77,584 97,953 $15,466,815,549 $10,554,980,566 $26,021,796,115 Source: Merced County Assessor’s Office, Wood Analysis
Table 4-6 Total Exposure by Jurisdiction and Property Type Jurisdiction
Property
Type
Improved
Parcel
Count
Building
Count Improved Value Estimated
Content Value Total Value
Atwater
Agricultural 4 4 $294,019 $294,019 $588,038
Commercial 254 941 $187,232,236 $187,232,236 $374,464,472 Exempt 77 150 $14,001,651 $14,001,651 $28,003,302
Industrial 48 48 $28,819,757 $43,229,636 $72,049,393
Mixed Use 6 6 $236,330 $236,330 $472,660
Residential 7,229 8,489 $1,159,329,319 $579,664,660 $1,738,993,979 Vacant
Land 16 16 $1,463,486 $1,463,486 $2,926,972
Total 7,634 9,654 $1,391,376,798 $826,122,017 $2,217,498,815 Dos Palos
Commercial 104 154 $16,913,918 $16,913,918 $33,827,836
Exempt 39 94 $1,962,673 $1,962,673 $3,925,346
Industrial 9 9 $1,043,139 $1,564,709 $2,607,848
Mixed Use 5 5 $104,170 $104,170 $208,340
Residential 1,611 1,733 $182,105,228 $91,052,614 $273,157,842 Vacant
Land 6 6 $40,429 $40,429 $80,858
Total 1,774 2,001 $202,169,557 $111,638,513 $313,808,070 Gustine
Agricultural 3 3 $249,806 $249,806 $499,612
Commercial 86 212 $13,841,697 $13,841,697 $27,683,394
Exempt 21 22 $1,947,230 $1,947,230 $3,894,460
Industrial 8 8 $21,456,333 $32,184,500 $53,640,833
Mixed Use 3 3 $55,055 $55,055 $110,110
Residential 1,749 1,857 $252,615,603 $126,307,802 $378,923,405 Vacant
Land 4 4 $180,379 $180,379 $360,758
Total 1,874 2,109 $290,346,103 $174,766,468 $465,112,571 DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-10
Jurisdiction
Property
Type
Improved
Parcel
Count
Building
Count Improved Value Estimated
Content Value Total Value
Livingston
Agricultural 8 9 $713,550 $713,550 $1,427,100
Commercial 82 235 $75,954,862 $75,954,862 $151,909,724
Exempt 48 114 $8,331,817 $8,331,817 $16,663,634
Industrial 19 33 $103,753,191 $155,629,787 $259,382,978 Mixed Use 3 4 $53,004 $53,004 $106,008
Residential 3,177 3,605 $519,238,129 $259,619,065 $778,857,194 Vacant
Land 7 7 $142,582 $142,582 $285,164
Total 3,344 4,007 $708,187,135 $500,444,666 $1,208,631,801 Los Banos
Agricultural 6 8 $519,029 $519,029 $1,038,058
Commercial 441 889 $287,223,390 $287,223,390 $574,446,780 Exempt 189 270 $15,571,378 $15,571,378 $31,142,756
Industrial 23 43 $29,327,893 $43,991,840 $73,319,733
Mixed Use 9 9 $175,156 $175,156 $350,312
Residential 11,554 11,861 $2,158,859,942 $1,079,429,971 $3,238,289,913 Vacant
Land 31 31 $530,525 $530,525 $1,061,050
Total 12,253 13,111 $2,492,207,313 $1,427,441,289 $3,919,648,602 Merced
Agricultural 23 26 $1,112,724 $1,112,724 $2,225,448
Commercial 911 2,819 $1,045,871,699 $1,045,871,699 $2,091,743,398 Exempt 632 1,313 $48,779,381 $48,779,381 $97,558,762
Industrial 120 220 $167,440,322 $251,160,483 $418,600,805 Mixed Use 16 17 $259,279 $259,279 $518,558
Residential 20,611 27,288 $3,488,757,480 $1,744,378,740 $5,233,136,220 Vacant
Land 49 61 $1,410,697 $1,410,697 $2,821,394
Total 22,362 31,744 $4,753,631,582 $3,092,973,003 $7,846,604,585 Unincorporated
Agricultural 9,875 13,314 $2,230,504,412 $2,230,504,412 $4,461,008,824 Commercial 689 1,703 $277,981,955 $277,981,955 $555,963,910 Exempt 427 769 $56,580,563 $56,580,563 $113,161,126
Industrial 158 250 $322,872,531 $484,308,797 $807,181,328 Mixed Use 70 81 $2,168,754 $2,168,754 $4,337,508
Residential 17,020 19,083 $2,737,477,431 $1,368,738,716 $4,106,216,147 Vacant
Land 104 127 $1,311,415 $1,311,415 $2,622,830
Total 28,343 35,327 $5,628,897,061 $4,421,594,611 $10,050,491,672 Grand Total 77,584 97,953 $15,466,815,549 $10,554,980,566 $26,021,796,115 Source: Merced County Assessor’s Office, Wood Analysis
Critical Facility/Lifeline Inventory
A significant aspect of the 2021 HIRA update was the update of critical facilities and an alignment/classification with the FEMA Lifelines framework. The critical facilities/lifelines GIS database was based on a combination of county-provided data, Homeland Infrastructure Foundation Level Data (HIFLD), and local input. Jurisdictions were able to browse map based critical facility data, edit descriptive attributes, and add new point data through a password protected interface built with the ArcGIS Online Experience Builder application setup by the County GIS coordinator. The results are summarized here and provided the basis for GIS based vulnerability analyses, where data permitted.
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For the purposes of this plan, a critical facility is defined as one that is essential in providing utility or direction either during the response to an emergency or during the recovery operation. FEMA sorts critical facilities into seven lifeline categories as shown in Figure 4-1.
Figure 4-1 Lifeline Categories
These lifeline categories standardize the classification of critical facilities and infrastructure that provide indispensable service, operation, or function to a community. A lifeline is defined as providing indispensable service that enables the continuous operation of critical business and government functions, and is critical to human health and safety, or economic security. These categorizations are particularly useful as they:
Ɣ Enable effort consolidations between government and other organizations (e.g., infrastructure owners and operators).
Ɣ Enable integration of preparedness efforts among plans, easier identification of unmet critical facility needs.
Ɣ Refine sources and products to enhance awareness, capability gaps, and progress towards stabilization.
Ɣ Enhance communication amongst critical entities, while enabling complex interdependencies between government assets.
Ɣ Highlight lifeline related priority areas regarding general operations as well as response efforts.
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Table 4-7 shows a summary of the critical facilities analysis. Figure 4-2 illustrates the location of critical facilities in Merced County.
Table 4-7 Summary of Critical Faciliti es by Jurisdiction and Lifeline Jurisdiction
Communications
Energy
Food, Water, Shelter
Hazardous Material
Health and Medical
Safety and Security
Transportation
Total
Atwater 7 5 3 1 1 34 11 62
Dos Palos 1 - - - - 7 - 8
Gustine 6 - 2 1 - 8 3 20
Livingston 6 1 3 3 - 14 5 32
Los Banos 15 2 20 6 3 53 6 105
Merced 36 3 52 17 22 87 53 270
Unincorporated 113 216 31 24 1 164 467 1,016
Total 184 227 111 52 27 367 545 1,513
Source: HIFLD, Merced County, City of Atwater, City of Dos Palos, City of Gustine, City of Livingston, City of Los Banos, City of Merced
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Figure 4-2 Merced County Critical Facilities
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Other critical facilities unique to the county are the California Aqueduct, the Castle Air Museum, and the Federal Bureau of Prisons located in Atwater. These facilities are better addressed in the emergency operations plans for the county, the two municipalities, and federal emergency plans.
The California Aqueduct, part of the California State Water Project, runs through the western part of Merced County. The State Water Project is a water storage and delivery system of reservoirs, aqueducts, power plants, and pumping plants. Its main purpose is to store water and distribute it to 29 urban and agricultural water suppliers in Northern California, the San Francisco Bay Area, the San Joaquin Valley, the Central Coast, and Southern California. Seventy percent of the contracted water supply goes to urban users and 30 percent goes to agricultural users. The State Water Project makes deliveries to two-thirds of California's population. Earthquakes, landslides, flooding, or other hazard events that disrupt the aqueduct’s ability to deliver water could have serious impacts to agriculture in the county and water users in many areas of California.
The Castle Air Museum is one of Merced County’s treasures drawing visitors from across the country.
Located on the site of the former Castle Air Force Base (known as Merced Army Airfield during WWII), the museum has a collection of 53 World War II, Korean War, and Vietnam Era aircraft. The indoor museum contains many additional Air Force and Army Air Corps artifacts and a B-52 simulator.
The Federal Bureau of Prisons in Atwater is one of the larger employers in the city with over 100 employees and approximately 1,600 prisoners. Although this plan recognizes the critical assets of this facility and its role in the county’s economy, as federally owned property, the prison develops its separate emergency management plans.
Cultural, Historical and Natural Resources
Assessing Merced County’s vulnerability to disaster also involves inventorying the natural, historical, and cultural assets of the area. This step is important for the following reasons:
Ɣ The community may decide that these types of resources warrant a greater degree of protection due to their unique and irreplaceable nature and contribution to the overall economy.
Ɣ In the event of a disaster, an accurate inventory of natural, historical and cultural resources allows for more prudent care in the disaster’s immediate aftermath when the potential for additional impacts is higher.
Ɣ The rules for reconstruction, restoration, rehabilitation, and/or replacement are often different for these types of designated resources.
Ɣ Natural resources can have beneficial functions that reduce the impacts of natural hazards, for example, wetlands and riparian habitat which help absorb and attenuate floodwaters and thus support overall mitigation objectives.
Historic and Cultural Resources
Historical resources are buildings, structures, objects, places, and areas that are eligible for listing in the National Register of Historic Places (NRHP), the California Register of Historic Resources, or the County’s List of Historic Resources, have an association with important persons, events in history, or cultural heritage, or have distinctive design or construction method.
For purpose of federal actions, a qualified historic resource is defined as a property listed in or formally determined eligible for listing in the NRHP before a disaster occurs. The NRHP is part of a national program to coordinate and support public and private efforts to identify, evaluate, and protect historic and archeological resources. Properties listed include districts, sites, buildings, structures, and objects that are significant in American history, architecture, archeology, engineering, and culture. The National Register is administered by the U.S. Department of the Interior National Park Service. Local and state DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-15
agencies may consider a broader definition of qualified historic properties in the review, evaluation, and treatment of properties damaged during a disaster.
The State of California Office of Historic Preservation can provide technical rehabilitation and preservation services for historic properties affected by a natural disaster. Depending on the hazard, protection could range from emergency preparedness, developing a fire safe zone around sites susceptible to wildfires, or seismically strengthening or structurally reinforcing structures.
State and local registers of historic resources provide designated Historical Landmarks, Points of Historical Interest, and Historic Buildings. These resources include, but are not limited to:
Ɣ The California Register of Historical Resources
Ɣ The California Historical Landmarks
Ɣ The California Inventory of Historical Resources
Ɣ The California Points of Historical Interest
,ŝƐƚŽƌŝĐĂůZĞƐŽƵƌĐĞƐĚĞƐŝŐŶĂƚĞĚŽŶĂĨĞĚĞƌĂů͕ƐƚĂƚĞŽƌůŽĐĂůůĞǀĞůĂƌĞůŝƐƚĞĚŝŶTable 4-8͘ Table 4-8 Merced County Historical Resources
Property Name Register Jurisdiction Date Listed
Bank of Italy National Merced 10/12/2004
Bank of Los Banos
Building National Los Banos 8/24/1979
Bloss Mansion National Atwater 9/3/1981
Buhach Grammar School National Merced 4/7/1983
Canal Farm Inn State Landmark Los Banos 1/27/1956
Church of St. Joseph National Los Banos 7/8/2004
Cook, Maj. George
Beecher, House National Merced 9/15/1983
G.B. Neighbors Home Point of Interest Snelling 6/2/1967 George S. Bloss Mansion Point of Interest Atwater 3/15/1974 Gwin Post Office, Paddy
Bennett Place Point of Interest Le Grand 1/19/1972
Kaehler-Rector House National Merced 1/4/192
Lake Yosemite Water
Tower Point of Interest Merced 1/19/1972
Leggett House National Merced 10/25/1979
Leggett, Thomas H. House National Merced 7/8/1982
Los Banos State Landmark Los Banos 3/1/1956
Los Banos Creek Point of Interest Los Banos 6/2/1967
Merced County
Courthouse Point of Interest/National Merced 6/2/1967/
10/29/1975
Merced County High
School National Merced 5/31/1984
Merced County Justice
Courthouse Building Point of Interest Gustine 8/25/1995 Merced Masonic
Temple/Welch & Griffith State Merced 11/3/2000
Merced Theatre National Merced 5/1/2009
Pacheco Pass State Landmark Los Banos 5/29/1969
San Luis Gonzaga
Archeological District National Los Banos 5/7/1973
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2021-2026 Update Page 4-16
Property Name Register Jurisdiction Date Listed
Snelling Community
Recreational Hall Point of Interest Snelling 6/2/1967
Snelling Courthouse State Landmark Snelling 11/15/1948
Temporary Detention
Camps for Japanese
Americans-Merced
Assembly Center
State Landmark Merced 5/13/1980
Tioga Hotel National Merced 10/3/1980
U.S. Post Office National Merced 2/10/1983
Source: California Office of Historic Preservation
Other historic sites of local importance also exist. These include several cemeteries and churches located in the larger cities and other rural areas in the county. The five additional sites designated as California Historical Landmarks include the Canal Farm Inn, Los Banos Park, Merced Assembly Center at Merced County Fairgrounds, Pacheco Pass at Romero Outlook, and Snelling Courthouse. Other notable sites include Applegate Park; one of Merced’s central parks located along the Bear Creek Bikeway. The park is an excellent destination on bike or foot. It offers 32 acres of recreation with a zoo, outdoor theater, picnic tables, barbeque grills, volleyball nets, tennis/basketball courts, a skate park, rental facilities, a large playground, a rose garden and fountain, and the Kiwanas-sponsored Kiddieland amusement park.
Applegate Park is located along Bear Creek and the Bear Creek bikeway, between M and R Streets. The southern edge of the park follows 25th Street, P Street, and 26th Street.
Lists of designated historical resources change periodically, and they may not include those currently in the nomination process and not yet listed. Additionally, as defined by the National Environmental Policy Act (NEPA), any property over 50 years of age is considered a historic resource and is potentially eligible for the National Register. Thus, in the event that the property is to be altered, or has been altered, as the result of a major federal action, the property must be evaluated under the guidelines set forth by NEPA.
Structural mitigation projects are considered alterations for the purpose of this regulation.
Cultural resources defined in California Environmental Quality Act Section 15064.5 as include prehistoric and historic archeological resources; historic-period resources (buildings, structures, area, place, or objects). Archeological resources reflect past human activity extending from Native American prehistoric cultures throughout the early 20th century. The artifacts left by previous occupants may be encountered in small to large residential sites, or special use areas.
Many cultural and historical resources in the County are vulnerable to several hazards due to location and the nature of their construction. Some of these risks include earthquakes, wildfires, coastal storms, or adverse weather.
Natural Resources
Natural resources are important to include in benefit/cost analyses for future projects and may be used to leverage additional funding for mitigation projects that also contribute to community goals for protecting sensitive natural resources. Inventory and awareness of natural resource assets is vital to meeting conservation objectives. For example, protecting wetland areas provides sensitive habitat protection as well as floodwater conveyance and storage, which further enhances public safety.
The Merced National Wildlife Refuge which encompasses 10,258 acres of wetlands, native grasslands, vernal pools, and riparian areas. It was established in 1951 under the Lea Act to attract wintering waterfowl away from adjacent farmland where foraging ducks and geese were causing extensive damage DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-17
to crops. Much of the Refuge is located in flood hazard areas and benefits the surrounding area by absorbing floodwaters and recharging aquifers.
To further understand natural resources that may be particularly vulnerable to a hazard event, as well as those that need consideration when implementing mitigation activities, it is important to identify at risk species (endangered and threatened species) in the Planning Area. The US Fish and Wildlife Service (USFW) maintains a list of federally listed threatened and endangered species for the country, which can be queried at the state or even county levels. The California Department of Fish and Wildlife also maintains species lists and accounts for threatened and endangered species. State and federal laws protect the habitat of these species through the environmental review process. Species of special concern may additionally include species that meets the State definition of threatened or endangered but has not been formally listed, experiences seriously population declines, or habitat decline, or has naturally small populations exhibiting high susceptibility to population decline (USFW 2019).
Table 4-9 summarizes Merced County’s special status animal species as indicated in the Fish and Wildlife Service database, within the Environmental Conservation Online System.
Table 4-9 Threatened and Endangered Species in Merced County Group Common Name Scientific Name Status
Amphibians California tiger Salamander Ambystoma californiense Threatened California red-legged frog Rana draytonii Threatened
Birds California condor Gymnogyps californianus Endangered Crustaceans
Conservancy fairy shrimp Branchinecta conservatio Endangered Vernal pool fairy shrimp Branchinecta lynchi Threatened Vernal pool tadpole shrimp Lepidurus packardi Endangered Fishes Delta smelt Hypomesus transpacificus Threatened
Flowering Plants
Greene's tuctoria Tuctoria greenei Endangered
Keck's Checker-mallow Sidalcea keckii Endangered
Colusa grass Neostapfia colusana Threatened
Hartweg's golden sunburst Pseudobahia bahiifolia Endangered Fleshy owl's-clover Castilleja campestris ssp.
succulenta Threatened
Hoover's spurge Chamaesyce hooveri Threatened
Hairy Orcutt grass Orcuttia pilosa Endangered
San Joaquin Orcutt grass Orcuttia inaequalis Threatened Insects
Monarch Butterfly Danaus plexippus Candidate
Valley elderberry longhorn
beetle Desmocerus californicus dimorphus Threatened
Mammals
Giant kangaroo rat Dipodomys ingens Endangered
San Joaquin kit fox Vulpes macrotis mutica Endangered
Fresno kangaroo rat Dipodomys nitratoides exilis Endangered Reptiles Blunt-nosed leopard lizard Gambelia silus Endangered Giant garter snake Thamnophis gigas Threatened
Source: USFW – Environmental Conservation Online System Growth and Development Trends
Population and Projected Growth
Merced County is the fastest growing county in the state, and the region as a whole is projected to grow significantly through 2060 (CA 4th CC Assessment). According to the Department of Finance (DOF) the 2020 population of Merced County as a whole was 283,521. DOF projects the total population will DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-18
increase by 86% to 329,635 by 2030. While total households in the County is also projected to increase from 89,454 in 2020 to 97,063, people per households is project to slightly decrease from 3.43 to 3.31 person per household.
All of the incorporated communities expect Dos Palos (slight decrease -0.1) experienced an increase or no change in population between 2019 and 2020. The City of Merced is listed by the California DOF as one of the top ten cities under 300,000 with the largest numeric change (+2,209) in population between 2019 and 2020 (88,120).
Increases in population growth also increase exposure to severe weather-related hazards, pandemic/epidemics as well as earthquakes. This increase in growth also puts more demand on water resources and can increase vulnerability to drought.
Social Vulnerability
Social vulnerability considerations were included in the update of this plan in 2021 to identify areas across the County that might be more vulnerable to hazard impacts based on a number of factors. A social vulnerability index (SoVI) was developed by the Center for Disease Control’s (CDC) Agency for Toxic Substances and Disease Registry and their Geospatial Research, Analysis & Services Program teams, as a way to portray communities’ capacities to prepare for and respond to natural and manmade disasters. The SoVI does so by providing insight into particularly vulnerable populations to in turn assist emergency response planners and even public health officials identify communities more likely to require additional support before, during, and after a hazardous event. The CDC’s SoVI create county- and state level maps to show relative vulnerability and hence provide key socially and spatially relevant information on communities’ populations, and these maps compare the SoVI based on Census Tracts. The overall social vulnerability based on the SoVI data is shown for Merced County by Census Tracts in Figure 4-5 below, based on statewide ranking. This overall index combines four main themes of vulnerability, namely:
socioeconomic status; household composition and disability; minority status and language; and housing and transportation, which in turn are comprised of subcategories for a total of 15 variables accounting for various vulnerability factors. For additional information on the CDC’s SoVI, refer to their documentation and materials online at https://svi.cdc.gov/.
Based on this data, the areas with the highest level of social vulnerability in the County are in the western and southeastern portion of the County, as well as some of the incorporated jurisdictions including Merced and Los Banos.
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2021-2026 Update Page 4-19
Figure 4-3 Overall Social Vulnera bility in Merced County based on the SoVI, by Census Tracts
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2021-2026 Update Page 4-20
Development Trends
As noted, the County has experienced population growth in the last decade and since the last plan update. There has been an increase in housing unit development, primarily in the cities of Merced, Gustine, Livingston and the unincorporated county. This new development built to modern codes should be less vulnerable to severe weather and earthquakes. Development in flood hazard areas should be mitigated to withstand the 1% annual chance flood; however, development in the 0.2% flood hazard zone is not regulated at this time. Although most development in the City of Merced and around the UC Merced campus has occurred in downtown Merced and in areas outside the floodplain.
Refer to Table 4-10 for comparison of housing units from the 2010 census to the ACS 5-Year estimates for 2015-2019 in the incorporated and unincorporated areas of Merced County. This comparison provides additional information on changes in development trends since the 2015 MJHMP was approved, for both the municipalities and the Census Designated Places (CDP) in the unincorporated areas.
Table 4-10 Housing Unit Development, 2010-2019
Jurisdiction 2010 2019 % Change
Merced County 83,698 85,251 2%
City of Atwater 9,771 9,577 -2%
Ballico CDP 132 182 38%
Bear Creek CDP 90 61 -32%
Cressey CDP 123 113 -8%
Delhi CDP 2,854 3,030 6%
City of Dos Palos 1,700 1,545 -9%
Dos Palos Y CDP 123 94 -24%
El Nido CDP 105 97 -8%
Franklin CDP 1,907 1,976 4%
City of Gustine 2,087 2,249 8%
Hilmar-Irwin CDP 1,841 2,001 9%
Le Grand CDP 503 554 10%
City of Livingston 3,320 3,699 11%
City of Los Banos 11,375 11,293 -1%
McSwain CDP 1,409 1,590 13%
City of Merced 27,446 26,873 -2%
Planada CDP 1,207 1,338 11%
Santa Nella CDP 493 614 25%
Snelling CDP 112 69 -38%
South Dos Palos CDP 488 629 29%
Stevinson CDP 101 154 52%
Tuttle CDP 39 48 23%
University of California Merced CDP 0 0 0%
Volta CDP 106 69 -35%
Winton CDP 3,056 3,305 8%
Source: California Dept. of Finance
The areas located in the Sphere of Influence (SOI) for each incorporated jurisdiction are areas each City plans to grow into and potentially slated for future development. Understanding the potential hazard exposure in each area can help to mitigate the impacts of events before development occurs in those areas. During this plan update process parcel analysis was conducted using the SOI areas for each incorporated jurisdiction and overlaid with available hazard risk layers to determine where future development may be at risk of natural hazard events. The results of the analysis have been integrated into DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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the applicable hazard sections: dam, flood, wildfire and landslide. Table 4-10 is the summary of the SOI total exposure by jurisdiction.
Table 4-11 Total Exposure Summary by J urisdiction Sphere of Influence Areas Jurisdiction Improved
Parcel Count
Building
Count Improved Value Estimated
Content Value Total Value
Atwater 675 837 $150,375,296 $124,680,732 $275,056,028
Dos Palos 545 688 $53,185,264 $32,248,327 $85,433,591
Gustine 97 126 $17,005,380 $15,800,283 $32,805,663
Livingston 60 85 $13,899,670 $12,073,468 $25,973,138
Los Banos 194 253 $28,473,256 $23,323,506 $51,796,762
Merced 2,528 2,896 $554,502,737 $328,069,420 $882,572,157 Total 4,099 4,885 $817,441,603 $536,195,735 $1,353,637,338
Ɣ City of Dos Palos - Received approval for a grant that will fund the construction of a new Water Treatment facility. Once the new facility is completed and operational, development can begin on new residential and commercial projects.
Ɣ City of Merced - City Council voted in February of 2021 to move forward the annexation of UC Merced. This would allow for additional annexations to potentially occur and would include up to 7,800 acres of land. Currently, much of this land is rolling grass land or grazing land. Much of this property will likely be developed into commercial, retail and high-density housing to support the demands of UC Merced.
Ɣ Merced County – The HMPT noted the growth and development trends associated with UC Merced, high-speed rail and related transit-oriented growth and growth at Castle Air Force Base associated with autonomous vehicle testing.
4.2 Hazard Analysis and Risk Summary
Requirement §201.6(c)(2)(i):
[The risk assessment shall include a] description of the type, location and extent of all natural hazards that can affect the jurisdiction. The plan shall include information on previous occurrences of hazard events and on the probability
of future hazard events.
4.2.1 Dam Incidents
Hazard/Problem Description
Dams are manmade structures built for a variety of uses, including flood protection, power generation, agriculture, water supply, and recreation. When dams are constructed for flood protection, they usually are engineered to withstand a flood with a computed risk of occurrence. For example, a dam may be designed to contain a flood at a location on a stream that has a certain probability of occurring in any one year. If prolonged periods of rainfall and flooding occur that exceed the design requirements, that structure may be overtopped and fail. Overtopping is the primary cause of earthen dam failure in the United States. Dam failures can also result from any one or a combination of the following causes:
Ɣ Earthquake
Ɣ Inadequate spillway capacity resulting in excess overtopping flows Ɣ Internal erosion caused by embankment or foundation leakage or piping or rodent activity Ɣ Improper design
Ɣ Improper maintenance
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-22
Ɣ Negligent operation
Ɣ Failure of upstream dams on the same waterway
Water released by a failed dam generates tremendous energy and can cause a flood that is catastrophic to life and property. A catastrophic dam failure could challenge local response capabilities and require evacuations to save lives. Impacts to life safety will depend on the warning time and the resources available to notify and evacuate the public. Major loss of life could result as well as potentially catastrophic effects to roads, bridges, and homes. Associated water quality and health concerns could also be issues. Factors that influence the potential severity of a full or partial dam failure are the amount of water impounded; the density, type, and value of development and infrastructure located downstream; and the speed of failure.
Controlled release or spillway flooding: Spillways are designed to relieve pressure on dams and prevent dam failures. Flooding downstream often results when spillways flow, though the potential for flooding as a result of discharge from dam outlet structures can also result from excessive rain events. However, controlled releases of water from dams is a measure that can prevent or minimize spillway flooding or structure failure, by regulating capacity in a managed way. Even controlled releases can lead to unwanted or unpredicted flooding, depending on environmental and weather conditions, or even human error.
In general, there are three types of dams: concrete arch or hydraulic fill, earth-rockfill, and concrete gravity. Each type of dam has different failure characteristics. A concrete arch or hydraulic fill dam can fail almost instantaneously: the flood wave builds up rapidly to a peak then gradually declines. An earth- rockfill dam fails gradually due to erosion of the breach: the downstream flood wave will build gradually to a peak and then decline until the reservoir is empty. And a concrete gravity dam can fail instantaneously or gradually with a corresponding buildup and decline of the flood wave.
Geographic Area
According to the California Department of Water Resources’ Jurisdictional Dams and the National Inventory of Dams (NID) databases there are 44 dams of concern to Merced County; ten of which are in the County and 34 upstream of the County. Table 4-11 lists the high and significant hazard dams within and upstream of Merced County.
Figure 4-4 shows where the high and significant hazard dams are located, and the potential inundation areas based on the best available data at the time of this plan update. It is important to note that the inundation areas shown do not represent all dams that pose a risk; some of this information is not available in GIS or allowed for release in a public document. Virtually no urban area in the County is free from flooding in the event of dam failure. Potential impacts are greatest for Merced, Livingston and the central areas of the unincorporated Merced County.
Table 4-12 Dams of Concern Within and Upstream of Merced County County Dam Name River Downstrea
m City
Normal
Storage
Capacity
(Acre Feet)
Emergency
Action
Plan
(EAP)?
NID
Hazard
Rating
CA DSOD
Hazard
Rating*
Merced
Lake Yosemite Merced 10,323 No High Extremely High
Castle Canal Creek 7,510 No High Extremely High
Merced Falls Merced Snelling 603 Yes High Low
Burns Burns Creek Planada 6,800 Yes High -
Los Banos Creek
Detention
Los Banos
Creek
Los Banos 34,500 Yes High -
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-23
County Dam Name River Downstrea
m City
Normal
Storage
Capacity
(Acre Feet)
Emergency
Action
Plan
(EAP)?
NID
Hazard
Rating
CA DSOD
Hazard
Rating*
O’Neill Forebay San Luis
Creek
Volta 56,430 Yes High -
B.F. Sisk Dike San Luis
Creek
- Yes High -
B.F. Sisk San Luis
Creek
2,094,900 Yes High -
Mustang Creek Mustang
Creek
700 No Significant Significant
Kelsey S. Fork Dry 1,000 No Significant Significant
Fresno
Alluvial Drain
Detention Big Dry Creek 833 No High
Big Dry Creek Big Dry Creek
& Dog Creek 30,200 No High
Fancher Creek
Fancher
Creek and
Hog Creek
9,600 No High
Fancher Creek
Detention
Fancher
Creek 1,891 No High
Friant Dike 3 520,500 Yes High
Friant Millerton
Road
Embankment A
San Joaquin
River Fresno 520,500 Yes High
Griffen Reservoir Holland
Creek 900 Yes High
Little Panoche
Detention
Little
Panoche
Creek
Oro Loma
5,580
Yes High
Pine Flat Dam Kings Sanger 1,000,000 Yes High
Redbank Redbank
Creek 1,100 No High
Redbank Creek
Detention Basin
Redbank
Creek
940
No High
Madera
Buchanan Dam Chowchilla
River Chowchilla 105,000 Yes High
Friant San Joaquin
River Fresno 520,500 Yes High
Hidden Dam Fresno River Madera 90,000 Yes High
Madera Lake Fresno River 2,300 No High
Berenda Slough Berenda
Slough
2,450 No Significant
Black Hawk Coarse Gold
Cr
740 No Significant
Mendota
Diversion
San Joaquin
River
3,000 No Significant
Oakhurst
Wastewater
Treatment
Tr Fresno
River
110 No Significant
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-24
County Dam Name River Downstrea
m City
Normal
Storage
Capacity
(Acre Feet)
Emergency
Action
Plan
(EAP)?
NID
Hazard
Rating
CA DSOD
Hazard
Rating*
Spring Longhollow
Creek
152 Yes Significant
Upper Wilcox
Unnamed
Tributary to
Picayunne
Creek
200 No Significant
Mariposa
Bear Dam Bear Creek Planada 7,700 Yes High
Exchequer Dike Merced River Snelling 1,024,600 Yes High Exchequer Main Merced River Snelling 1,024,600 Yes High Mariposa Dam Mariposa
Creek Le Grand 15,000 Yes High
Mcswain Merced River Snelling 8,255 Yes High
Owens Dam Owens Creek Planada 3,600 Yes High
Stockton Creek Stockton
Creek 368 No High
Stanislaus Turlock Lake Tuolumne
River 63,406 Yes High
Tuolumne
Don Pedro Dike
B
Tuolumne
River La Grange 2,030,000 Yes High
Don Pedro Main Tuolumne
River La Grange 2,030,000 Yes High
Gasburg Creek
Dike
Tuolumne
River La Grange 1 Yes High
Don Pedro Dike
A
Tuolumne
River La Grange 2,030,000 Yes Significant
Don Pedro Dike
C
Tuolumne
River La Grange 2,030,000 Yes Significant
Source: California Department of Water Resources Division of Safety of Dams (DSOD) and the NID * DSOD added a fourth category (“Extremely High”) to the NID categories for downstream hazard potential. Extremely High is defined as expected to cause considerable loss of human life or would result in an inundation area with a population of 1,000 or more.
Analysis using inundation data and mapping associated with the O’Neil Forebay, Los Banos, and San Luis dams was not possible for the plan due to information being considered sensitive and restricted, per communication with OES and the dam owners. The following is a summary of the downstream communities that would be affected by each dam in a dam failure or incident based on information in dam emergency action plans, including depth of inundation and time to inundation.
Ɣ O’Neil Forebay Dam
- Santa Nella: 4-10 feet within 5 hours of failure
- Ingoma: 0-2 feet within 10 hours
- Volta: 2-4 feet within 5 hours
Ɣ Los Banos Dam
- Los Banos: 5-6 feet within 2.5 hours
- Volta: 5-6 feet within 2.5 hours
- Trent: 5-6 feet within 2.5 hours
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-25
Ɣ San Luis Dam
- Santa Nella: 10-20 ft within 2 hours
- Volta: 10-20 ft in less than 10 hours
- Ingomar: 10-20 ft in less than 10 hours
- Trent: 2-4 ft in 5 hours
- Gustine: 2-10 ft in less than 10 hours
- Stevenson: 2-10 in 15 hours
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-26
Figure 4-4 Dams of Concern to Merced County and Best Available Inundation Mapping
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2021-2026 Update Page 4-27
Extent (Magnitude/Severity)
Standard practice among federal and state dam safety offices is to classify a dam according to the potential impact a dam failure (breach) or mis-operation (unscheduled release) would have on downstream areas. The hazard potential classification system categorizes dams based on the probable loss of human life and the impacts on economic, environmental and lifeline facilities. The US Army Corp of Engineers uses three categories to classify dams’ potential hazard to life and property:
Ɣ High hazard indicates that a failure would most probably result in the loss of life; Ɣ Significant hazard indicates that a failure could result in appreciable property damage; Ɣ Low hazard indicates that failure would result in only minimal property damage and loss of life is unlikely.
Ɣ Undetermined hazard dams have not been rated or their hazard rating is not known In addition to these, high, significant, and low hazard classifications the California Division of Dam Safety (DSOD) adds the fourth category of “Extremely High”. The DSOD defines this fourth category as “expected to cause considerable loss of human life or would result in an inundation area with a population of 1,000 or more” (DSOD 2020). As shown in Table 4-11 two dams in Merced County, Lake Yosemite and Castle dams are classified as “Extremely High”.
In 2017 the State of California established the Spillway Re-evaluation Program after the Orville Dam incident, to assess spillways to confirm they meet minimum safety standards. The Don Pedro dam located in Tuolumne County was listed as being part of this program and poses a risk to central portions of Merced County.
Since the County has several high and significant hazard dams, there is potential for loss of life and property damage. The inundation areas for each of the dams are generally downstream and include large rural and urban areas on the valley floor below the dams. Adjacent jurisdictions could also be affected by a dam failure in Merced County. The extent of impacts depends on the nature of failure and location of the dam. The largest populations potentially at risk would be in Merced, Livingston, and Atwater. The central portions of the unincorporated areas county would also be impacted were a dam to fail and flood downstream.
Past Occurrences
There is no history of dam failure affecting the county, but according to the HMPT there have been recurring issues with flooding due to high flows released below dams in the area.
Probability of Future Occurrences
Occasional—The County remains at risk to dam fa ilures from numerous dams under a variety of ownership and control and of varying ages and conditions. However, based on historical experience dam failure is unlikely in the area. Nevertheless, given the number of dams of concern in the County the potential exists for future dam failures in Merced County, but the likelihood of this is low. Uncontrolled or controlled release flooding as well as spillway flooding below dams due to excessive rain or runoff are more likely to occur than failures.
Climate Change Considerations
The potential for climate change to affect the likelihood of dam failure is not fully understood at this point in time. With a potential for more extreme precipitation events a result of climate change, this could result in large inflows to reservoirs. However, this could be offset by generally lower reservoir levels if storage DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-28
water resources become more limited or stretched in the future due to climate change, drought and/or population growth.
Vulnerability Assessment
A dam incident can range from a small, uncontrolled release to a catastrophic failure. Vulnerability to dam failures is confined to the areas and populations subject to inundation downstream of the facility.
Secondary losses would include loss of the multi-use functions of the dam itself and associated revenues that accompany those functions.
General Property
In general, communities located below a high or significant hazard dam and along a waterway are potentially exposed to the impacts of a dam failure. Inundation maps that identify anticipated flooded areas (which may not coincide with known floodplains) are typically produced for all high hazard dams and included in the Emergency Action Plan (EAP) required for each dam. A GIS layer that contained inundation maps for four of the 34 high hazard dams that affect the County was analyzed to quantify risk across the planning area. Table 4-13 through Table 4-16 summarize the estimated building exposure (more details on the parcel analysis methodology under the Asset Summary section). Table 4-12 summarizes the results of the GIS analysis, and includes a population estimate based on the number of residential parcels exposed, multiplied by an average household size estimate from the census. Exposure estimates from failure of other high hazard dams were not possible due to data restrictions and/or limitations.
Table 4-13 Summary of Dam Inundation by Dam and Jurisdiction Dam Jurisdiction Improved
Parcel Count
Building
Count Population
Don Pedro Dam
Livingston 1 1 -
Unincorporated 3,888 4,909 8,353
Total 3,889 4,910 8,353
McSwain Dam
Livingston 1 1 -
Unincorporated 160 180 309
Total 161 181 309
New Exchequer Dam
Atwater 37 37 -
Livingston 3,340 4,001 14,216
Unincorporated 8,869 11,138 19,505
Total 12,246 15,176 33,721
Yosemite Dam
Atwater 21 23 67
Merced 4,768 6,080 18,784
Unincorporated 1,024 1,359 3,214
Total 5,813 7,462 22,065
Grand Total 22,109 27,729 64,447
Source: California DSOS, NID, Merced County Assessor’s Office Table 4-14 Don Pedro Dam Inundation
Jurisdiction Property Type Improved
Parcel Count Building Count
Livingston Agricultural 1 1
Total 1 1
Unincorporated Agricultural 1,352 1,968
Commercial 97 333
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-29
Jurisdiction Property Type Improved
Parcel Count Building Count
Exempt 40 56
Industrial 15 19
Mixed Use 2 2
Residential 2,365 2,514
Vacant Land 17 17
Total 3,888 4,909
Grand Total 3,889 4,910
Source: California DSOS, NID, Merced County Assessor’s Office Table 4-15 McSwain Dam Inundation
Jurisdiction Property Type Improved
Parcel Count Building Count
Livingston Agricultural 1 1
Total 1 1
Unincorporated
Agricultural 48 59
Commercial 13 18
Exempt 7 8
Industrial 1 1
Residential 90 93
Vacant Land 1 1
Total 160 180
Grand Total 161 181
Source: California DSOS, NID, Merced County Assessor’s Office Table 4-16 New Exchequer Dam Inundation
Jurisdiction Property Type Improved
Parcel Count
Building Count
Atwater Residential 37 37
Total 37 37
Livingston
Agricultural 8 9
Commercial 79 231
Exempt 48 113
Industrial 19 33
Mixed Use 3 4
Residential 3,176 3,604
Vacant Land 7 7
Total 3,340 4,001
Unincorporated
Agricultural 3,183 4,415
Commercial 223 603
Exempt 101 144
Industrial 41 64
Mixed Use 12 15
Residential 5,273 5,860
Vacant Land 36 37
Total 8,869 11,138
Grand Total 12,246 15,176
Source: California DSOS, NID, Merced County Assessor’s Office DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-30
Table 4-17 Lake Yosemite Dam Inundation
Jurisdiction Property Type Improved
Parcel Count
Building Count
Atwater
Commercial 1 2
Residential 20 21
Total 21 23
Merced
Agricultural 5 5
Commercial 24 30
Exempt 110 134
Industrial 22 38
Mixed Use 1 1
Residential 4,603 5,869
Vacant Land 3 3
Total 4,768 6,080
Unincorporated
Agricultural 36 46
Commercial 34 305
Exempt 10 12
Industrial 18 22
Mixed Use 3 3
Residential 917 965
Vacant Land 6 6
Total 1,024 1,359
Grand Total 5,813 7,462
Source: California DSOS, NID, Merced County Assessor’s Office People
Persons located underneath or downstream of a dam are at risk of a dam failure, though the level of risk can be tempered by topography (specifically where populations are located within the inundation path of a dam), amount of water in the reservoir and time of day of the breach. Injuries and fatalities can occur from debris, bodily injury and drowning. Once a dam has breached, standing water presents all the same hazards to people as floodwater from other sources. People in the inundation area may need to be evacuated, cared for, and possibly permanently relocated. Impacts could include thousands of evacuations and likely hundreds of casualties, depending on the dam involved. Specific population impacts are noted in Table 4-12 , and total people at risk were calculated by multiplying the average number of persons per household in Merced County (3.32) and each applicable incorporated jurisdiction (Atwater 3.18, Livingston
3.94, and Merced 3.20) times the number of residential parcels where dam inundation occurs. Based on the best available data accessible to the planning team at this time of this analysis, an incident at the New Exchequer Dam would potentially put the most people at risk (33,721), followed by Lake Yosemite dam (22,064) and Don Pedro dam (8,353). The unincorporated areas of Merced County have the most people (31,381) potentially exposed to a dam inundation event followed by City of Merced with potentially 18,784 exposed to the Lake Yosemite dam inundation. Population impacts from other high hazard dams were not possible due to data restrictions and/or limitations.
Critical Facilities
A total dam failure can cause catastrophic impacts to areas downstream of the water body, including critical infrastructure. Any critical asset located under the dam in an inundation area would be susceptible to the impacts of a dam failure. Of particular risk would be roads and bridges that could be vulnerable to washouts, further complicating response and recovery by cutting off impacted areas. Based on the critical facility inventory considered in the updating of this plan and intersected with the dam inundation extents DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-31
available, 272 critical facilities were found to be at risk. Unincorporated County has the greatest number of facilities at risk followed by City of Merced and City of Livingston. These at risk facilities are listed in the tables below by jurisdiction and critical facility classification as based on the FEMA Lifeline categories.
Table 4-18 Dam Inundation Effects on Critical Fa cilities – Estimates by Jurisdiction and FEMA Lifeline
Jurisdiction
Communications
Energy
Food, Water, Shelter
Hazardous Material
Health and Medical
Safety and Security
Transportation
Total
Atwater - - - - - - 1 1
Dos Palos - - - - - - - 0
Gustine - - - - - - - 0
Livingston 6 1 3 3 - 13 5 31
Los Banos - - - - - - - 0
Merced 4 2 6 3 3 4 13 35
Unincorporated 21 8 16 8 - 64 88 205
Total 31 11 25 14 3 81 107 272
Source: HFILD, Merced County, Cities of Atwater, Dos Palos, Gustine, Livingston, Los Banos, Merced As noted under the Geographic Area section, inundation data is not available for the O’Neil Forebay, Los Banos or San Luis Dams due to being restricted and sensitive information. The following is a summary of the potential impacts on critical facilities from a dam failure or inundation event.
Ɣ O’Neil Forebay Dam
- Potential Impacts to Transportation infrastructure:
o Interstate 5
o Highway 33
o Highway 140
- Potential Impacts to Water Systems infrastructure:
o Delta Mendota
o The California Aqueduct
Ɣ Los Banos Dam
- Potential impacts to Transportation infrastructure:
o Interstate 5
o Highway 152
o Highway 165
- Potential impacts to Water Systems infrastructure:
o Delta Mendota
o The California Aqueduct
Ɣ San Luis Dam
- Potential impacts to Transportation infrastructure:
o Interstate 5
o Highway 152
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-32
o Interstate 165
o Highway 33
o Highway 140
- Potential impacts to Water Systems infrastructure:
o Delta Mendota
o The California Aqueduct
- Potential impacts to Power/Energy infrastructure:
o PG&E substations
o Solar fields
Economy
Extensive and long-lasting economic impacts could result from a major dam failure including the long- term loss of water in a reservoir after a failure event. Based on the analysis there is 6,504 buildings, at a minimum, that are designated as agricultural properties potentially exposed to dam inundation event. A major dam incident and loss of water from the associated reservoir could include direct business and specifically impacts to the agricultural industry, resulting in damages and indirect disruption of the local economy.
Historic, Cultural and Natural Resources
Dam failure effects on the environment would be similar to those caused by flooding from other causes.
Water could erode stream channels and topsoil and cover the environment with debris. For the most part the environment is resilient and would be able to rebound from whatever damages occurred, though this process could take years. However, historic and cultural resources could be affected just as housing or critical infrastructures would, were a dam to fail and cause downstream inundation that could further erode surfaces or cause scouring of structural foundations.
Future Development
GIS was used to analyze parcels exposed to dam inundation areas that are located within each city’s SOI.
The results shown in Table 4-18 show that there is a total of 6,917 buildings and 18,247 currently exposed to dam inundation within the SOI areas.
Table 4-19 Total Dam Inundation Summary by Dam within Sphere of Influence Areas Dam Inundation Sphere of
Influence
Improved
Parcel Count
Building
Count Population
Don Pedro Dam
Delhi 55 55 183
Hilmar 1,450 1,778 4,731
Livingston 1 3 0
Total 1,506 1,836 4,914
McSwain Dam
Cressey 1 1 3
Livingston 1 1 0
Snelling 104 111 286
Total 106 113 289
New Exchequer Dam
Atwater 10 12 7
Ballico 59 65 166
Cressey 78 92 262
Delhi 1,021 1,319 3,788
Hilmar 1,450 1,778 4,731
Livingston 59 83 149
Snelling 145 170 412
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-33
Dam Inundation Sphere of
Influence
Improved
Parcel Count
Building
Count Population
Stevinson 53 65 149
Winton 98 113 375
Total 2,973 3,697 10,040
Yosemite Dam
Atwater 42 44 120
Franklin 774 1,080 2,520
Merced 128 147 365
Total 944 1,271 3,005
Grand Total 5,529 6,917 18,247
Source: California DSOS, NID, Merced County Assessor’s Office The areas located in the SOI for each incorporated jurisdiction are areas each City plans to grow into and potentially slated for future development. In addition to the SOI areas there are also 71 vacant parcels countywide that are within dam inundation areas. These areas should take into consideration potential impacts from dam failure risk upstream and should attempt to overlay the existing dam inundation maps with proposed future development. In the case of a dam failure, inundation would likely follow some existing FEMA mapped floodplains, which contains development restrictions for areas in the 1% annual chance floodplain, but it could exceed those floodplains and affect areas that are not regulated for flood hazards. Also, of note is that development below a low or undetermined hazard dam could increase its hazard rating, though there is only one low hazard and one undetermined hazard dam in the County (while the majority are high or significant hazard dams). Finally, added development could compromise dams and reservoir resources if populations depend on them for critical needs such as potable water during or after a dam failure event.
Risk Summary
Ɣ There are 44 dams of concern for Merced County. 10 are within the county (8 High Hazard Potential and two Significant) and 34 dams are upstream of the county (26 High Hazard and eight Significant).
Ɣ Of the eight high hazard potential rated dams in the County, 2 (Castle and Yosemite dams) are rated as “Extremely High” by the State of California DSOD.
Ɣ Countywide there are a minimum of 27,729 parcels at risk based on limited available inundation mapping, with greatest number of buildings exposed in unincorporated areas (17,586) followed by the City of Merced (6,080), City of Livingston (4,003) and City of Atwater (60).
Ɣ Residential property types make up the most buildings (18,963) at risk of flooding from dam failures, agricultural (6,504), and commercial (1,522).
Ɣ Based on limited available mapping, the New Exchequer Dam puts the most parcels at risk of dam inundation (33,721) countywide (most in Unincorporated and Livingston), followed by the Yosemite dam (22,065).
Ɣ An estimated 64,447 people countywide might be displaced from their homes based the location of their residences along the inundation areas; actual amounts would vary.
Ɣ A total of 272 critical facilities are within dam inundation areas. The greatest number in unincorporated Merced County (205) and Transportation lifeline is most at risk countywide.
Ɣ Related Hazards: drought, flooding, earthquake/liquefaction, landslide, and severe weather.
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Table 4-20 Hazard Risk Summary by Jurisdiction - Dam Incidents Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Significant Occasional Catastrophic Medium City of Atwater Extensive Occasional Limited Medium
City of Dos Palos Limited Occasional Limited Medium
City of Gustine Extensive Occasional Limited Low
City of Livingston Limited Occasional Limited Medium
City of Los Banos Extensive Occasional Catastrophic Medium City of Merced Extensive Occasional Catastrophic High
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4.2.2 Drought
Hazard/Problem Description
Drought is a gradual phenomenon. Normally, one dry year does not constitute a drought in California, but rather serves as a reminder of the need to plan for droughts. California's extensive system of water supply infrastructure (reservoirs, groundwater basins, and interregional conveyance facilities) generally mitigates the effects of short-term dry periods for most water users.
Drought can have secondary impacts. For example, drought is a major determinant of wildfire hazard, in that it creates greater propensity for fire starts and larger, more prolonged conflagrations fueled by excessively dry vegetation, along with reduced water supply for firefighting purposes. Drought is also an economic hazard. Significant economic impacts on California’s agriculture industry can occur as a result of short- and long-term drought conditions; these include hardships to farmers, farm workers, packers, and shippers of agricultural products. In some cases, droughts can also cause significant increases in food prices to the consumer due to shortages.
Drought is a complex issue involving many factors—it occurs when a normal amount of moisture is not available to satisfy an area’s usual water-consuming activities. Drought can often be defined regionally based on its effects:
Ɣ Meteorological drought is defined by a period of substantially diminished precipitation duration and/or intensity. The commonly used definition of meteorological drought is an interval of time, generally on the order of months or years, during which the actual moisture supply at a given place consistently falls below the climatically appropriate moisture supply.
Ɣ Agricultural drought occurs when there is inadequate soil moisture to meet the needs of a particular crop at a particular time. Agricultural drought usually occurs after or during meteorological drought, but before hydrological drought and can affect livestock and other dry-land agricultural operations.
Ɣ Hydrological drought refers to deficiencies in surface and subsurface water supplies. It is measured as stream flow, snowpack, and as lake, reservoir, and groundwater levels. There is usually a delay between lack of rain or snow and less measurable water in streams, lakes, and reservoirs. Therefore, hydrological measurements tend to lag other drought indicators.
Ɣ Socioeconomic drought occurs when physical water shortages start to affect the health, well-being, and quality of life of the people, or when the drought starts to affect the supply and demand of an economic product.
The California Department of Water Resources (DWR) says the following about drought:
“One dry year does not normally constitute a drought in California. California’s extensive system of water supply infrastructure—its reservoirs, groundwater ba sins, and interregional conveyance facilities— mitigates the effect of short-term dry periods for most water users. Defining when a drought begins is a function of drought impacts to water users. Hydrologic conditions constituting a drought for water users in one location may not constitute a drought for water users elsewhere, or for water users having a different water supply. Individual water suppliers may use criteria such as rainfall/runoff, amount of water in storage, or expected supply from a water wholesaler to define their water supply conditions.” The drought issue in California is further compounded by water rights. Water is a commodity possessed under a variety of legal doctrines. The prioritization of water rights between farming and federally protected fish habitats in California is part of this issue.
Drought impacts are wide-reaching and may be economic, environmental, and/or societal. The most significant impacts associated with drought in the planning area are those related to water intensive activities such as agriculture, wildfire protection, municipal usage, commerce, tourism, recreation, and DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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wildlife preservation. Also, during a drought, allocations go down, which results in reduced water availability. Voluntary water conservation measures are typically implemented during extended droughts.
A reduction of electric power generation and water quality deterioration are also potential problems that can occur as a result of drought conditions. The reduced demand for electrical power generation is commonly linked to higher electricity costs due to the loss of hydropower supplies. Water quality deterioration is due to lower levels of precipitation and limited water storage supply. Drought conditions can also cause soil to compact and not absorb water well, potentially making an area more susceptible to flooding.
Geographic Area
Drought is a regional hazard, and at its worst can affect the entire state of California with varying levels of dryness and drought activity (as will be covered in more detail under the sections to follow). It is safe to assume that unless the drought event is at its very beginning or very end, if any area of the Merced County is affected by any level of drought, the other areas of the county are experiencing varying effects as well.
Sustainable Groundwater Management Act (SGMA) of 2014
In January 2014, Governor Brown declared an emergency proclamation due to multiple years of drought.
The proclamation called on citizens to reduce water use by 20 percent; with a subsequent executive order in April 2015 that directed urban water agencies to reduce water use by 25 percent (Ken Topping, 2016).
In September 2014, the Governor signed a three-bill package (California Senate Bills 1168 and 1319, and Assembly Bill 1739), known as the SGMA. The SGMA provides for the establishment of local GSAs to manage groundwater sustainability within the groundwater subbasins defined by the California DWR.
Within Merced County there are portions of four groundwater subbasins, Merced, Turlock, Delta Mendota, and Chowchilla, that are required under SGMA to conduct sustainable groundwater planning and management. Each of the four subbasins are required to develop and implement a GSP by 2020 or 2022.
As of April 2021, all four subbasins have formed 14 GSAs as shown in Table 4-20.
Table 4-21 Groundwater Sustaina bility Agencies in Merced County Subbasin Groundwater Sustainability Agency (GSA)
Merced
Merced-Irrigation-Urban GSA
Merced Subbasin GSA
Turner Island Water District GSA #1
Turlock West Turlock GSA
East Turlock GSA
Delta Mendota
City of Dos Palos GSA
City of Gustine GSA
City of Los Banos GSA
Central Delta Mendota GSA
Turner Island Delta Mendota GSA
Northwestern Delta Mendota GSA
Grassland Water District GSA
San Joaquin River Exchange Contractors GSA
Chowchilla Chowchilla Water District GSA
County of Merced Chowchilla GSA
Source: Merced County Water Resources https://www.co.merced.ca.us/3140/Sustainable-Groundwater---SGMA DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Extent (Magnitude/Severity)
The magnitude of a drought’s impact is directly related to the severity and length. The severity of a drought depends on water availability and moisture deficiency, the time period, and the size and location of the affected area. The longer the drought persists and the larger the area impacted, the more severe the potential impacts. Droughts can be a short-term event over several months or a long-term event that lasts for years or even decades. In Merced County, the onset of drought is often signaled by a lack of significant winter precipitation and snowfall (moisture deficiency) in the Sierra Nevada Mountains.
Droughts typically do not result in direct impacts on people or property, but they can have significant impacts on agriculture, which can indirectly impact people and property. Hot and dry conditions that persist into spring, summer, and fall can aggravate drought conditions, making the effects of drought more pronounced as water demands increase during the growing season and summer months. Impacts increase with the length of a drought, as carry over supplies in reservoirs are depleted and water levels in groundwater basins decline (California DWR 2012).
The U.S. Drought Monitor is an accepted and widely used site for obtaining and summarizing drought information, as it integrates data from several other sources including the Palmer Drought Index, Soil Moisture Models, U.S. Geological Survey Weekly Stream Flows, Standardized Precipitation Index, and the Satellite Vegetation Health Index. It includes drought intensity categories for measuring dry conditions across counties, states, and regions of the U.S., so that drought can be quantified. These categories range from “abnormally dry” to “exceptional drought.” The following figures provide “snapshots in time” of the drought conditions in California as of August 2015 (during the period of the last multi-year drought in Merced County and the state, from 2012- 2017) and March 30, 2021. The snapshots selected are instrumental in depicting both the historic and potential change in drought’s geographic range and severity in the County (circled in blue).
Note: The Drought Monitor maps integrate data from several sources including the Palmer Drought Index, Soil Moisture Models, U.S. Geological Survey Weekly Stream flows, Standardized Precipitation Index, and Satellite Vegetation Health Index. The drought status in California is noted on the following graphic from the National Drought Mitigation Center.
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Figure 4-5 U.S. Drought Monitor for California: August 4, 2015
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Figure 4-6 U.S. Drought Monitor for California: March 30, 2021 Past Occurrences
Historically, California has experienced severe drought conditions. The state’s available record for determining hydrologic risks is short, only going back about 100 years. Recent droughts affecting Merced County are summarized below using data from Cal OES and from the County Agricultural Commissioner’s Office.
Ɣ 1928-1937—This drought affected the entire state and is the longest, most severe drought on record with a recurrence interval of greater than 100 years.
Ɣ 1947-1950—Drought affected the entire state but was mo st extreme in Southern California. The drought in winter of 1950 affected the area from the Kern River basin north to the American River basin. The drought caused two deaths and $33 million in damages.
Ɣ 1976-1977—The drought of 1976-1977 was most severe in the northern three-quarters of California, but the impact was experienced statewide because of the dependence of Southern California on water transfers from the north. The water year 1977 was the driest year of record at almost all gauging stations in the affected area in California, and the water year 1976 was among the five driest in the central and northern Sierra Nevada. The two-year deficiency in runoff accumulated during the drought is unequalled at gauging stations in the affected area; and this deficiency has a recurrence interval that exceeds 80 years. Crop damages statewide were $2.67 billion.
Ɣ 1987-1992—California experienced a serious drought due to low precipitation and runoff levels.
During this multi-year, multi-county drought, the runoff from the San Joaquin Valley was 47 percent of average. In 1991, the U.S. Department of Agriculture Economic Research Report Agricultural Outlook reported that the Merced River flow would be inadequate to provide sufficient water for
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agricultural uses for the fifth consecutive year. A U.S. Department of Agriculture (USDA) drought disaster declaration was declared.
Ɣ 2004-2005—On January 15, 2005, the USDA designated 53 of California’s 58 counties as natural disaster areas due to damages and losses caused by extreme drought.
Ɣ 2008-2009—On June 12, 2008, the Governor proclaimed Me rced County as a state disaster area due to the Central Valley Drought.
Ɣ 2012 – 2017—In September 2012, the USDA designated Merced County a contiguous disaster area due to drought that occurred since January 1, 2012. In January 2014, the Governor proclaimed a State of Emergency and directed state officials to take all necessary actions to prepare for these drought conditions: to assist farmers and communities that are economically impacted by dry conditions and to ensure the state can respond if Californians face drinking water shortages. The Governor also directed state agencies to use less water and hire more firefighters and initiated an expansive water conservation public awareness campaign. Drought produced severe impacts to water wells throughout the planning area, with a high number of wells running dry. Land subsidence due to increased groundwater pumping also occurred in areas of the San Joaquin Valley. Crop damage was widespread as well. Water allotments were drastically reduced in many towns and water agencies, with extremely high costs for procuring water. In addition, job loss occurred with many families requiring food supply assistance, and water supply assistance provided to homeowners with dry wells.
According to a report released by UC Davis Center for Watershed Sciences, the 2014 California drought cost the state's agriculture industry about $1 billion in lost revenue, with a total statewide economic cost of the drought calculated to be $2.2 billion. The 2014 drought, the report says, is responsible for the greatest water loss ever seen in California agriculture - about one-third less than normal. The report calls the groundwater situation in California "a slow-moving train wreck." (NCICS 2019). According to the 2018 State of California Hazard Mitigation Plan, by the time the drought was declared officially in 2017, the state been declared a federal disaster area and had expended $6.6 billion in drought response and mitigation programs.
As shown in Table 4-4, of the 18 total Secretary of Agricultural Disaster Designations for Merced County in the past 8 years, 15 were specific to drought. In addition to the USDA designations there have also been two federal disaster declarations due to drought in the county (Refer to Table 4-3).
The National Drought Mitigation Center developed the Drought Impact Reporter in response to the need for a national drought impact database for the United States. Information comes from a variety of sources:
online, drought-related news stories and scientific publications, members of the public who visit the website and submit a drought-related impact for their region, members of the media, and members of relevant government agencies. The database is being populated beginning with the most recent impacts and working backward in time. The Drought Impact Reporter contains information on 195 impacts from droughts that affected Merced County between 2000 and 2020. Most of the impacts (113) were classified as “water supply and quality” and “relief, response and restrictions” (101). Other impacts included “agriculture” (79), “society and public health” (72), “plants and wildlife” (23), “fire” (16), “business and industry” (13), “tourism and recreation” (7) and “energy” (6). These categories are described as follows:
Ɣ Water Supply and Quality (113) —Drought effects associated with water supply and water quality include dry wells, voluntary and mandatory water restrictions, changes in water rates, increasing of water restrictions, increases in requests for new well permits, changes in water use due to water restrictions, greater water demand, decreases in water allocation or allotments, installation or alteration of water pumps or water intakes, changes to allowable water contaminants, water line damage or repairs due to drought stress, drinking water turbidity, change in water color or odor, declaration of drought watches or warnings, and mitigation activities.
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Ɣ Relief, Response, and Restrictions (101) —This category refers to drought effects associated with disaster declarations, aid programs, requests for disaster declaration or aid, water restrictions, or fire restrictions. Examples include disaster declarations, aid programs, USDA Secretarial disaster declarations, Small Business Association disaster declarations, government relief and response programs, state level water shortage or water emergency declarations, county-level declarations, a declared “State of Emergency,” requests for declarations or aid, nonprofit organization based relief, water restrictions, fire restrictions, National Weather Service (NWS) Red Flag Warnings, and declaration of drought watches or warnings.
Ɣ Agriculture (79) —Drought effects associated with agriculture, farming, aquaculture, horticulture, forestry, or ranching. Examples of drought-induced agricultural impacts include damage to crop quality; income loss for farmers due to reduced crop yields; reduced productivity of cropland; insect infestation; plant disease; increased irrigation costs; cost of new or supplemental water resource development (wells, dams, pipelines) for agriculture; reduced productivity of rangeland; forced reduction of foundation stock; closure/limitation of public lands to grazing; high cost or unavailability of water for livestock, Christmas tree farms, forestry, raising domesticated horses, bees, fish, shellfish, or horticulture.
Ɣ Society and Public Health (72) —Drought effects associated with human, public and social health include: health-related problems related to reduced water quantity or quality, such as increased concentration of contaminants; loss of human life (e.g., from heat stress, suicide); increased respiratory ailments; increased disease caused by wildlife concentrations; increased human disease caused by changes in insect carrier populations; population migration (rural to urban areas, migrants into the United States); loss of aesthetic values; change in daily activities (non-recreational, like putting a bucket in the shower to catch water); elevated stress levels; meetings to discuss drought; communities creating drought plans; lawmakers altering penalties for violation of water restrictions; demand for higher water rates; cultural/historical discoveries from low water levels; cancellation of fundraising events; cancellation/alteration of festivals or holiday traditions; stockpiling water; public service announcements and drought information websites; protests; and conflicts within the community due to competition for water.
Ɣ Plants and Wildlife (23)—Drought effects associated with unmanaged plants and wildlife, both aquatic and terrestrial, include: loss of biodiversity of plants or wildlife; loss of trees from rural or urban landscapes, shelterbelts, or wooded conservation areas; reduction and degradation of fish and wildlife habitat; lack of feed and drinking water; greater mortality due to increased contact with agricultural producers (as predators seek food from farms and producers are less tolerant of the intrusion); disease; increased vulnerability to predation (from species concentrated near water); migration and concentration (loss of wildlife in some areas and too much wildlife in others); increased stress on endangered species; salinity levels affecting wildlife; wildlife encroaching into urban areas; and loss of wetlands.
Ɣ Fire (16)—Drought often contributes to forest, range, rural, or urban fires, fire danger, and burning restrictions. Specific impacts include enacting or increasing burning restrictions, fireworks bans, increased fire risk, occurrence of fire (number of acres burned, number of wildfires compared to average, people displaced, etc.), state of emergency during periods of high fire danger, closure of roads or land due to fire occurrence or risk, and expenses to state and county governments of paying firefighters overtime and paying equipment (helicopter) costs.
Ɣ Business and Industry (13) —This category tracks drought’s e ffects on non-agriculture and non- tourism businesses, such as lawn care, recreational vehicles, or gear dealers, and plant nurseries.
Typical impacts include reduction or loss of demand for goods or services, reduction in employment, variation in number of calls for service, late opening or early closure for the season, bankruptcy, permanent store closure, and other economic impacts.
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Ɣ Tourism and Recreation (7) —Drought effects associated with recreational activities and tourism include closure of state hiking trails and hunting areas due to fire danger; water access or navigation problems for recreation; bans on recreational activities; reduced license, permit, or ticket sales (e.g., hunting, fishing, ski lifts, etc.); losses related to curtailed activities (e.g., bird watching, hunting and fishing, boating, etc.); reduced park visitation; and cancellation or postponement of sporting events.
Ɣ Energy (6)—This category concerns dr ought's effects on power production, rates and revenue.
Examples include production changes for both hydropower and non-hydropower providers, changes in electricity rates, revenue shortfalls and/or windfall profits, and purchase of electricity when hydropower generation is down.
Probability of Future Occurrences
Likely – Historical drought data for the County planning area and the San Joaquin Valley region indicate there have been five significant multi-year droughts in the last 91 years. This equates to a multi-year drought every 18 years on average, or a 5 percent chance of a drought in any given year. Based on this data, droughts will likely affect the planning area. Given the historical occurrence of severe drought impacts throughout Merced County and across the state, the HMPC understands that drought will continue to pose a high degree of risk to the entire planning area, potentially impacting crops, livestock, water resources, the natural environment at large, buildings and infrastructure (from cascading or compound hazards), and local economies.
In addition, although drought affects the entire planning equally, the potential impacts may be variable and specific to each jurisdiction, depending on contextual factors such as the degree of assets and activities historically impacted by drought within each jurisdiction, such as the agricultural and parks and tourism industries.
Climate Change Considerations
Water resources in California area already experiencing stresses related to population growth, increased water demand, poor water quality, groundwater overdraft, and aging infrastructure. Scientific studies prepared for various California climate assessments and adaptations strategies also already show that drought conditions in California are likely to become more frequent and persistent over the next century due to climate change. Temperatures are warming, heat waves are more frequent, and precipitation has become increasingly variable (California Natural Resources Agency 2018a). According to California’s Climate Adaptation Strategy, also referred to as “Safeguarding California Plan: 2018 Update”, climate change is likely to significantly diminish California’s future water supply. As a result, the state must change its water management, as climate change will create greater competition for limited water supplies (California Natural Resources Agency 2018b). The recent drought conditions over the past decade underscore the need to examine water supply and distribution management, conservation, and use policies. California and the San Joaquin Valley region have experienced a succession of dry spells and with warmer temperatures and periodic droughts that frequently contribute to water shortages in the region.
Climate change projections of extreme prolonged droughts will exacerbate the San Joaquin Valley’s existing water supply challenges. In an average year, approximately 40 percent of the state’s total water supply comes from groundwater, and during a dry year this increases to more than half of the state’s water supply, with groundwater acting as a critical buffer against the impacts of drought and climate change (California Natural Resources Agency 2018).
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Table 4-22 Summary of Climate Chan ge Impacts on Water Resources Resource Type of
Impact Description
Soil Moisture Direct Prolonged dry seasons can lead to decreases in soil moisture; drier vegetation
Vegetation Indirect Longer and more intense fire season with increased extent of area burned
Stream Conditions Direct Increases in water temperature; potential effects on fish
Snowpack Indirect Increases in temperature will lead to decreases in snowpack
Runoff Direct
Warmer temperatures are likely to lead to a shift in
peak runoff from spring to winter and a likely
decrease in summer baseflow
Hydropower Indirect
Decreased summer flows resulting from earlier
snowmelt and a shift in peak runoff could affect
hydropower generation during summer months
Precipitation Direct
Warmer winter temperatures will result in a greater
percentage of precipitation falling as rain rather than as snow
Groundwater Indirect
Reduction in snowpack and extended periods of
drought are likely to increase dependency on
groundwater
Source: http://frap.fire.ca.gov/data/assessment2010/pdfs/3.1water.pdf p. 140 Vulnerability Assessment
All of Merced County is vulnerable to drought. Drought is one of the few hazards with the potential to impact all the citizens of the county through water restrictions, economic losses, and increased energy costs. The urbanized areas of the county and the agriculture industry are most likely to experience hardships associated with reduced water supply.
Impacts include water restrictions associated with domestic supplies, agricultural and livestock losses and economic impacts, hydroelectric power reductions, and increased costs for water. Secondary effects include susceptibility to wildfires and increased groundwater pumping that can contribute to land subsidence problems and degraded water quality.
General Property
Based on the USDA’s Risk Management Agency (RMA) Crop Indemnity Reports, which were collected for the years 2007-2020, crop losses due to drought were only reported between 2007 and 2014 across the county. Table 4-22 summarizes the agricultural losses experienced across the county communities. A total of $885,477 was indemnified for 14,660 acres of insured crops.
Table 4-23 Crops Loss Due to Drought, Risk Management Agency Crop Indemnity Reports, 2007-2020
Year Crop
Net
Determined
Acres
Indemnity
Amount
2007
Wheat 301.9 $16,130
Oats 228.3 $1,241
Barley 1,345.9 $32,857
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Year Crop
Net
Determined
Acres
Indemnity
Amount
Total 1,876 $50,228
2008
Wheat 683.2 $75,727
Oats 1,376.3 $34,192
Barley 960.9 $45,245
Total 3,020 $155,164
2009
Wheat 2,179.4 $280,639
Oats 882.7 $32,334
Barley 1,534.2 $74,455
Total 4,596 $387,428
2010 Wheat 860.2 $5,599
Total 860.2 $5,559
2011 Wheat 170 $22,806
Total 170 $22,806
2012
Wheat 1,910.3 $167,880
Oats 1,482 $56,827
Total 3,392 $224,707
2013
Wheat 243.9 $8,907
Oats 35 $633
Total 279 $9,540
2014
Wheat 313.9 $26,623
Oats 151.4 $3,382
Total 465 $30,005
Grand Total 14,660 $885,477
Source: USDA RMA Crop Indemnity Reports, 2007-2020
People
According to this California DOF the 2020 County population was 283,521 people. The County’s population is projected to continue to increase by 1 percent to 1.48 percent annually until 2060 (CBPR 2016). This projected population growth would add additional strain to the surface water supplies and already depleted groundwater supplies but through the County Groundwater ordinance which prohibits the unstainable extraction or conveyance may help with reducing the impacts on drought on the regional groundwater supply.
The historical and potential impacts of drought on populations include agricultural sector job loss, secondary economic losses to local businesses and public recreational resources, increased cost to local and state government for large-scale water acquisition and delivery, and water rationing and water wells running dry for individuals and families. As drought is often accompanied by prolonged periods of extreme heat, negative health impacts such as dehydration can also occur, where children and elderly are most susceptible. Air quality often declines in times of drought which can affect those with respiratory ailments.
Critical Facilities
Drought impacts to critical facilities include water shortfalls for facility operations and critical functions, and potential structural destabilization and damage resulting from land subsidence. Refer to the section on Subsidence for more information.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Economy
Drought impacts to the local or regional economy can be difficult to quantify but can be extensive and long-lasting depending on the circumstances during, and after a severe drought event. If water resources are limited, effects would be more severe for industries that rely on large amounts of water and any prolonged drought would intensify these impacts. Sectors critical to the economy such as commerce, distribution, agriculture, tourism, related environmental resources, municipal and industrial water supply, key city assets, energy generation, and even socioeconomic aspects can be affected due to lack of, or even reduced quality of water resources.
Agriculture in the San Joaquin Valley relies on artificial irrigation using mostly imported water and/or groundwater. Local droughts are expected and accommodated for; however, a prolonged statewide drought could exceed local capabilities to handle reductions of imported surface water supplies and potentially lead to reductions in distribution from local water storage districts.
The costs of drought are difficult to quantify because the impacts affect so many different sectors including wildlife and natural resources, business and industry, tourism and recreation, agriculture, and individual households. Agriculture often suffers the most financial losses from drought and is the major component of the Merced County economy. For example, according to the California Integrated Climate Adaptation and Resiliency Program’s 2020 Report and 2020 Recommendations, the 2014-2017 multi-year drought was estimated to cost over $6.6 billion once it was over and the loss of 5,000 jobs in 2016 (OPR 2020).
Historic, Cultural and Natural Resources
The Merced National Wildlife Refuge encompasses over 10,000 acres of wetlands, native grasslands, vernal pools and riparian areas and is home to various bird species and other wildlife including the largest wintering population of lesser Sandhill cranes and Ross’ geese, and both species are vulnerable to drought. The impacts of drought on vegetation and wildlife can include death from dehydration and spread of invasive species or disease because of stressed conditions, loss of biodiversity, loss of trees in rural and urban landscapes, loss of wetlands, and degradation of habitat.
In general, environmental impacts from drought are more likely at the interface of the human and natural world. The loss of crops or livestock due to drought can have far reaching economic effects on communities, wind and water erosion can alter the visual landscape, and dust can damage property.
Water-based recreational resources are also heavily affected by drought conditions. Indirect impacts from drought arise from increased wildfire risk and greater occurrence of fire.
Future Development
With the County’s population projected to continue to grow while climate change projections are showing an increased duration an intensity of drought events for the San Joaquin Valley, it will be important for each new development application to be reviewed with existing and future water supplies in mind.
Because future development encompasses all forms of property, buildings, infrastructure, critical facilities and all related populations and their functions, drought impacts to future development align with the historical and potential impacts to populations, property, natural environment, and critical facilities discussed (above).
Risk Summary
Ɣ Due to the widespread impacts in San Joaquin Valley, it can have, drought is considered a High significance hazard.
Ɣ There have been five multi-year droughts in the past 91 years. Most recent drought lasted from 2012 to 2017 and resulted in a declared State of Emergency.
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Ɣ 15 USDA Disaster Designations due to drought have been made in the last 8 years.
Ɣ 195 reports of impacts related to drought were made within Merced County between, 2000 and 2020.
Ɣ Between 2007-2014 a total of $885,477 crop indemnity claims was paid due to crop losses for a total of 14,660 acres due to drought impacts.
Ɣ Climate change projections show that extreme prolonged drought is likely to continue and will exacerbate existing water supply challenges.
Ɣ Related Hazards: Extreme Heat, Wildfire, Subsidence, Agricultural Pest Infestation and Disease Table 4-24 Hazard Risk Summary – Drought
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Likely Critical High
City of Atwater Extensive Likely Limited Medium
City of Dos Palos Extensive Likely Limited Medium
City of Gustine Extensive Likely Limited Medium
City of Livingston Extensive Likely Limited Medium
City of Los Banos Extensive Likely Limited Medium
City of Merced Extensive Likely Negligible Low
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4.2.3 Earthquake
Hazard/Problem Definition
An earthquake is caused by a sudden slip on a fault. Stresses in the earth’s outer layer push the sides of the fault together. Stress builds up and the rocks slip suddenly, releasing energy in waves that travel through the earth’s crust and cause the shaking that is felt during an earthquake. The amount of energy released during an earthquake is usually expressed as a magnitude and is measured directly from the earthquake as recorded on seismographs. The magnitude of earthquakes is usually measured using the Richter scale; a logarithmic scale calculated from the amplitude of the largest seismic wave recorded for the earthquake.
Another measure of earthquake severity is intensity. Intensity is an expression of the amount of shaking at any given location on the ground surface. Seismic shaking is typically the greatest cause of damage to structures during earthquakes. Seismologists have developed the Mercalli scale to quantify the shaking intensity of an earthquake’s effects, which is measured by how an earthquake is felt by humans and the damage to buildings.
Earthquakes can cause structural damage, injury, and loss of life, as well as damage to infrastructure networks such as water, power, gas, communication, and transportation lines. Other damage-causing effects of earthquakes are surface rupture, fissuring, settlement, and permanent horizontal and vertical shifting of the ground. Secondary impacts can include landslides, seiches, liquefaction, and dam failure.
Liquefaction occurs when ground shaking causes the mechanical properties of some fine grained, saturated soils to liquefy and act as a fluid (liquefaction). It is the result of a sudden loss of soil strength due to a rapid increase in soil pore water pressures caused by ground shaking, in areas of shallow groundwater (within 10’ of surface or less). Liquefaction that produces surface effects generally occurs in the upper 40 to 50 feet of the soil column, although the phenomenon can occur deeper than 100 feet.
The duration of ground shaking is also an important factor in causing liquefaction to occur. The larger the earthquake magnitude, and the longer the duration of strong ground shaking, the greater the potential there is for liquefaction to occur.
In populated areas, the greatest potential for loss of life and property damage can come as a result of ground shaking from a nearby earthquake. The degree of damage depends on many interrelated factors.
Among these are the moment magnitude, focal depth, distance from the causative fault, duration of shaking, type of surface deposits or bedrock, presence of high ground water, topography, and finally, the design, type, and quality of building construction.
Geographic Area
The nearest faults of major significance are the San Andreas to the west of Merced County, a distance of approximately 15 miles from the county line; the Hayward and Calaveras faults to the northwest; the White Wolf, Garlock, and Sierra Nevada faults to the south; and the Bear Mountain Fault Zone about 5 miles east of and parallel to the eastern border of Merced County. These faults have been and will continue to be the principal source of seismic activity affecting the County of Merced.
The only fault known inside the County is the "Ortigalita", also known as the "Telsa-Ortigalita Fault", located in the western quarter of the County, dissecting the Coast Range in a northwesterly direction. This fault has not been active in historic times, however, there is no guarantee that it will never become active again.
There have been no records of major seismic activity originating in the county, with most epicenters in the county being below a magnitude 4.0. However, the county has been shaken by earthquakes originating elsewhere. There is documented evidence of six earthquakes that shook the area, those of 1872, 1906, DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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1952, 1966, 1984, and 1989. Major damage occurred in Los Banos in 1906, with minor damage recorded throughout the county from other occurrences.
The San Andreas Fault occurs where the North American and Pacific plates come together and grind in a side-by-side motion relative to each other. Another large known fault, the White Wolf fault, is located to the south near Arvin and Bakersfield in Kern County and produced a severe M 7.7 earthquake in 1952.
Figure 4-7 below shows the known faults and potential for ground shaking resulting from earthquakes in and near Merced County, based on USGS probabilistic ground shaking with a 2% in 50-year occurrence (AKA 2500-year probabilistic ground shaking).
Figure 4-7 Merced County Earthquake Ground Shaking Potential and Nearby Faults
Earthquakes can occur at any time of the day or night and any time of the year. Earthquakes are particularly dangerous due to their rapid onset, generally without warning. Aftershocks can occur for days, weeks, and even months following a major earthquake. This additional damage to structures already weakened by the main earthquake increases the danger to rescue and recovery personnel.
Extent (Magnitude/Severity)
For extent, the severity of an earthquake, or the amount of energy released during an earthquake is usually expressed in terms of intensity or magnitude as described further below.
Intensity: Intensity represents the observed effects of ground shaking at any specified location and earthquake shaking decreases with distance from the earthquake epicenter. Intensity is an expression of the amount of shaking at any given location on the ground surface based on felt or observed effects.
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Seismic shaking is typically the greatest cause of losses to structures during earthquakes. Intensity is measured with the Modified Mercalli Intensity (MMI) scale. The intensity of ground shaking at a particular site or structure is a function of many factors including: 1) earthquake magnitude, 2) distance from the epicenter, 3) duration of strong ground motion, 4) local geologic conditions (soil type and topography), and 5) the fundamental period of the structure. A brief description of those factors is presented below.
The Modified Mercalli Intensity scale is summarized in Table 4-24, along with the effects associated with the MMI scale. Damage typically occurs in MMI of scale VII or above.
Earthquake Magnitude: Magnitude represents the amount of seismic energy released at the hypocenter of an earthquake. It is based on the amplitude of the earthquake waves recorded. Seismologists have developed several magnitude scales; one of the first was the Richter Scale, developed in 1932 by the late Dr. Charles F. Richter of the California Institute of Technology. The Richter scale is numeric and has a logarithmic relationship between scale factors, so that a difference of one scale number represents a tenfold increase in measured amplitude, which in turn corresponds to an approximate 31x energy release difference when compared to the next whole number value. The Moment Magnitude scale (M w, or M), which is a measurement of energy released by the movement of a fault and is the modern method used by seismologists to measure earthquakes. Overall, as the amount of energy released by an earthquake increases, the potential for ground shaking impacts also increases.
Distance from Epicenter: Earthquake energy generally dissipates (or attenuates) with distance from a fault. Over long distances, this loss of energy can be significant, resulting in a significant decrease in ground shaking with increased distance from the epicenter.
Duration of Strong Shaking: The duration of the strong ground shaking constitutes a major role in determining the amount of structural damage and the potential for ground failure that can result from an earthquake. Larger magnitude earthquakes have longer durations than smaller earthquakes.
Local Geologic Conditions: The geologic and soil conditions at a particular site have the potential to substantially increase the effects of ground shaking. The thickness, density, and consistency of the soil, as well as shallow ground water levels, have the potential to amplify the effects of ground shaking depending on the characteristics of the earthquake. In general, the presence of unconsolidated soils above the bedrock surface can amplify the ground shaking caused by an earthquake.
Fundamental Periods: Every structure has its own fundamental period or natural vibration. If the vibration of ground shaking coincides with the natural vibration period of a structure, damage to the structure can be greatly increased. The extent of damage suffered during an earthquake can also depend on non-geologic factors. The type of building and its structural integrity will influence the severity of the damage suffered. Generally, small, well-constructed, one- and two-story wood and steel frame buildings have performed well in earthquakes because of their light weight and flexibility. Reinforced concrete structures will also usually perform well. Buildings constructed from non-flexible materials, such as unreinforced brick and concrete, hollow concrete block, clay tile, or adobe, are more vulnerable to earthquake damage.
Effects of Ground Shaking: The primary effect of ground shaking is the damage or destruction of buildings, infrastructure, and possible injury or loss of life. Building damage can range from minor cracking of plaster to total collapse. Disruption of infrastructure facilities can include damage to utilities, pipelines, roads, and bridges. Ruptured gas and water lines can result in fire and produce scour/inundation damage, respectively, to structures, as can fire from other causes, such as electrical damages. Secondary effects can include geologic impacts such as co-seismic fault movement along nearby faults, seismically induced slope instability, liquefaction, lateral spreading, and other forms of ground failure and seismic response. These secondary effects were demonstrated in Oceano by the San Simeon 2003 earthquake.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-25 Earthquake Magnitude and Intensit y Measurements and Intensity Characteristics Magnitude Mercalli
Intensity Effects Frequency
Less than 2.0 I Microearthquakes, not felt or rarely felt; recorded by seismographs. Continual
2.0-2.9 I to II Felt slightly by some people; damages to buildings. Over 1M per year
3.0-3.9 II to IV Often felt by people; rarely causes damage; shaking of indoor objects noticeable.
Over 100,000
per year
4.0-4.9 IV to VI Noticeable shaking of indoor objects and rattling noises; felt by most people in the affected area; slightly felt outside; generally, no to minimal damage.
10K to 15K
per year
5.0-5.9 VI to VIII Can cause damage of varying severity to poorly constructed buildings; at most, none to slight damage to all other buildings. Felt by everyone. 1K to 1,500
per year
6.0-6.9 VII to X Damage to a moderate number of well-built structures in populated areas; earthquake-resistant structures survive with slight to moderate damage; poorly designed structures receive moderate to severe damage; felt in wider areas; up to hundreds of miles/kilometers from the epicenter; strong to violent shaking in epicentral area. 100 to 150
per year
7.0-7.9 VIII< Causes damage to most buildings, some to partially or completely collapse or receive severe damage; well-designed structures are likely to receive damage; felt across great distances with major damage mostly limited to 250 km from epicenter.
10 to 20 per
year
8.0-8.9 VIII< Major damage to buildings, structures likely to be destroyed; will cause moderate to heavy damage to sturdy or earthquake-resistant buildings; damaging in large areas; felt in extremely large regions.
One per year
9.0 and
Greater
VIII< At or near total destruction - severe damage or collapse to all buildings; heavy damage and shaking extends to distant locations; permanent changes in ground topography.
One per 10-
50 years
Source: USGS
Past Occurrences
There have not been any damaging earthquakes greater than M 6.0 recorded in Merced County in over 200 years and the County has not been included in any federal disaster declarations involving earthquakes, though several have been very close. The most recent large earthquake near Merced County was 16 miles east north-east of King City at a magnitude of 5.3 on October 20, 2012. Several aftershocks followed the main earthquake, including a 3.1 aftershock. This quake was preceded by two earthquakes located approximately 100 miles from Merced County, the 1982 New Idria earthquake (M 5.4) and the 1983 Coalinga (M 6.5). There was a low level of ground shaking reported.
Major earthquakes have occurred near Merced County and resulted in ground shaking felt in the county.
The Fort Tejon earthquake in 1857 of M 7.9 was one of the greatest earthquakes ever recorded in the United States and the largest in California. It left an extensive surface rupture scar over 215 miles in length along the San Andreas Fault. The epicenter is now thought to have been located near Cholame, approximately 134 miles southwest of the City of Merced. During the Fort Tejon earthquake, strong shaking lasted from one to three minutes. As a result of the shaking, the flow of the Kern River was turned upstream, and water ran four feet deep over its banks. The waters of Tulare Lake were thrown upon its shores, stranding fish miles from the original lakebed. Property loss was heavy at Fort Tejon, one of the only settlements at the time, an Army post in south-central Kern County about four miles from the San DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-51
Andreas Fault. In 1857, two buildings were declared unsafe, three others were damaged extensively but were habitable, and still others sustained moderate damage. One person was killed in the collapse of an adobe house at Gorman.
Figure 4-8 below displays the common areas damaged by earthquakes based on historic evidence dating back to the year 1800. The occurrences are color-coded by damaging shaking intensity across the state of California, and Merced County is enclosed within a black circle. The figure shows that, per the MMI scale noting occurrences equal to or greater than an Intensity of VII, the county has experienced 1 to 3 earthquake events of this kind, mostly affecting the far western and southwestern portions of the County.
Figure 4-8 Areas Damaged by Ea rthquakes from 1800 to 2017
Source: California State Hazard Mitigation Plan, 2018; California Geologic Survey
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2021-2026 Update Page 4-52
Probability of Future Occurrences
It is estimated that major earthquakes (ranging from a magnitude of 7 to 7.9) occur in California one out of every 10 years. However, strong earthquakes (from magnitudes 6 to 6.9) strike the state about once every two to three years. A strong earthquake can cause major damage depending on the epicenter’s location with regards to populated areas, and can lead to billions of dollars in disasters, deaths, injuries, and disruptions in services and communities’ way of life. Moderate earthquakes (around magnitudes of
5.5) can occur three to four times a year in the state.
Along the San Andreas Fault, segments exist where no large earthquakes have occurred for long intervals of time. These areas accumulate potential energy and provide clues as to where the next earthquake may occur and when. Scientists term these segments “seismic gaps” and, in general, have been successful in forecasting the time when some of the seismic gaps will produce large earthquakes. Geologic studies show that over the past 1,400 to 1,500 years, large earthquakes have occurred at about 150-year intervals on the southern San Andreas Fault. As the last large earthquake on the southern San Andreas was the Fort Tejon earthquake in 1857, that section of the fault is considered a likely location for an earthquake within the next few decades (USGS 1997).
Based on the earthquake shaking potential mapped for Merced County, the proximity to the San Andreas Fault with a history of shaking, but no surface rupture, the probability of damaging seismic ground shaking in Merced County is occasional. The shaking levels expected with a 2% in 50 years probability are depicted in Figure 4-7.
Climate Change Considerations
Climate change is not expected to directly affect earthquake frequency or intensity.
Vulnerability Assessment
Earthquake loss estimation for the 2021 HMP update utilized FEMA’s Hazus-MH 4.2 natural hazard loss estimation software. Hazus is a GIS based, standardized, nationally applicable multi-hazard loss estimation methodology and software. Local, state and federal government officials use Hazus for preparedness, emergency response, and mitigation planning. A level 1 Hazus analysis was performed which estimates damage based on an inventory database compiled at a national level aggregated to Census Tracts. As with any model there are uncertainties, and the results should be considered approximate for planning purposes.
To evaluate potential losses associated with earthquake activity in the planning area, a Hazus 2,500-year probabilistic scenario was run for Merced County. The 2,500-year scenario represents the level of shaking considers multiple faults in the region instead of a single scenario. The methodology utilizes probabilistic seismic hazard contour maps developed by the U.S. Geological Survey (USGS) for the 2018 update of the National Seismic Hazard Maps that are included with HAZUS-MH. The USGS maps provide estimates of potential ground acceleration and spectral acceleration at periods of 0.3 second and 1.0 second, respectively. The 2,500-year return period analyzes ground shaking estimates from the various seismic sources in the area with a 2 percent probability of being exceeded in 50 years. The International Building Code uses this level of ground shaking for building design in seismic areas.
Hazus estimates the number of people displaced, the number of buildings and facilities/infrastructure damaged, the number of casualties, and the damage to transportation systems and utilities. Results produced by Hazus are reported at the census tract level. Figure 4-9 below displays the Census Tracts within the county which were analyzed in this scenario, color-coded by the amount of total losses each tract experienced. The map is followed by the Hazus results broken up in respective sections.
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2021-2026 Update Page 4-53
Figure 4-9 Hazus Earthquake Analysis for Merce d County – Total Losses by Census Tract (in Thousands of Dollars)
General Property
Unreinforced Masonry Building (URM)s: Unreinforced masonry building type structures consist of buildings made of unreinforced concrete and brick, hollow concrete blocks, clay tiles, and adobe. Buildings constructed of these materials are heavy and brittle, and typically provide little earthquake resistance. In small earthquakes, unreinforced buildings can crack, and in strong earthquakes, they have a tendency to collapse. These types of structures pose the greatest structural risk to life and safety of all general building types.
Per Hazus, there are an estimated 77,000 buildings in Merced County with a total building replacement value (excluding contents) of $24 Billion. Approximately 94% of these buildings (and 82% of the building value) are associated with residential housing. In terms of building construction types found in the region, wood frame construction makes up 87% of the building inventory. The remaining percentage is distributed between the other general building types.
The categories of damages defined by Hazus are:
Slight damage includes diagonal hairline fractures on most shear wall surfaces and hairline cracks on most infill walls.
Moderate damage includes cracks on most walls and failure of some shear walls.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Extensive damage means that most shear wall surfaces in the structure have reached or exceeded their capacity exhibited by large, through-the-wall diagonal cracks.
Complete damage means that the structure has collapsed or is in danger of collapse.
The building losses are broken into two categories: direct building losses and business interruption losses.
The direct building losses are the estimated costs to repair or replace the damage caused to the building and its contents. The business interruption losses are the losses associated with inability to operate a business because of the damage sustained during the earthquake. Business interruption losses also include the temporary living expenses for those people displaced from their homes because of the earthquake.
The total building-related losses were $2.4 billion. By far, the largest loss was sustained by the residential occupancies which made up over 61% of the total loss. Figure 4-10 and Figure 4-11 below provide a summary of the losses associated with the building damage.
Figure 4-10 Earthquake Losses by Loss Type and Occupancy Type (in Millions of Dollars)
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Figure 4-11 Hazus 2,500 Year Probabilistic Earthquake Scenario Structure Damage by Occupancy Type
Source: Hazus-MH 4.2
Hazus estimates that about 17,106 buildings will be at least moderately damaged. This is over 22% of the total building stock in the county. There are an estimated 1,386 buildings that will be damaged beyond repair. Table 4-25 summarizes the expected damage by property occupancy type in more detail, whereas Table 4-26 contains the results of the expected building damage by building material type.
Table 4-26 Expected Building Damage by Occupancy Class
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-27 Expected Building Damage by Building Material (All Design Levels)
Source: Hazus-MH 4.2
Hazus also estimates the amount of debris that will be generated by the earthquake event analyzed. The model subdivides the debris into two general categories: a) Brick/Wood, and b) Reinforced Concrete/Steel. This distinction is made because of the different types of material handling equipment required to handle the debris.
The model estimates that a total of 442,000 tons of debris will be generated. Of that total amount, Brick/Wood comprises 38% of the debris, while the remainder would be Reinforced Concrete/Steel. If the debris tonnage was converted to estimates of truckloads required to remove it, debris generated would convert to about 17,680 truckloads, with each truckload carrying 25 tons. Figure 4-12 summarizes the debris generation estimate and material type for this earthquake event.
Figure 4-12 Debris Generation in Millio ns of Tons and by Material Type
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-57
People
Shelter Requirement: Hazus estimates the number of households that are expected to be displaced from their homes due to the earthquake and the number of displaced people that will require accommodations in temporary public shelters. The model estimates 918 households to be displaced due to the earthquake.
Of these, approximately 882 people (out of a total population of 255,793) will seek temporary shelter in public shelters.
Casualties: Ground movement during an earthquake is seldom the direct cause of death or injury. Most earthquake-related injuries result from collapsing walls, flying glass, and falling objects as a result of the ground shaking, or people trying to move more than a few feet during the shaking. Hazus estimates the number of people that will be injured and killed by the earthquake. The casualties are broken down into four severity levels that describe the extent of the injuries. The levels are described as follows:
Severity Level 1: Injuries will require medical attention, but hospitalization is not needed.
Severity Level 2: Injuries will require hospitalization but are not considered life-threatening.
Severity Level 3: Injuries will require hospitalization and can become life-threatening if not promptly treated.
Severity Level 4: Victims are killed by the earthquake.
The casualty estimates are provided for three times of day: 2:00 AM, 2:00 PM and 5:00 PM. These times represent the periods of the day that different sectors of the community are at their peak occupancy loads. The 2:00 AM estimate considers that the residential occupancy load is at its maximum. The 2:00 PM estimate considers that the educational, commercial and industrial sector loads are at their maximum, and has the highest numbers of casualties estimated. The 5:00 PM represents peak commute time. These estimates of casualties are broken down in Table 4-27.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-58
Table 4-28 Hazus Earthquake Casual ty Estimates from Merced County
Source: Hazus-MH 4.2
Social Vulnerability
Populations most vulnerable to earthquake and liquefaction activity would be those that rely on specific services or electrical power, which may not be available during or after a quake, or those which are homeless, would have a difficult time evacuating due to age or disability, cannot communicate easily due to speaking English less than well, for example.
Critical Facilities and Infrastructure
Critical Facility Inventory: Hazus breaks critical facilities into two groups: essential facilities and high potential loss facilities. Essential facilities include hospitals, medical clinics, schools, fire stations, police
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-59
stations and emergency operations facilities. High potential loss facilities include dams, levees, military installations, nuclear power plants and hazardous material sites.
Essential Facility Damage: There are four (4) hospitals in the region with a total bed capacity of 246 beds. There are 145 schools, 31 fire stations, 14 police stations and one (1) emergency operation facility.
The inventory also includes 23 hazardous material sites.
On the day of the earthquake, the model estimates that only 125 hospital beds (51%) are available for use by patients already in the hospital and those injured by the earthquake. After one week, 75% of the beds will be back in service. By 30 days, 94% will be operational. The essential facility inventory and expected damages from the earthquake event are provided in Table 4-28.
Transportation Systems Inventory: Within Hazus, the lifeline inventory is divided between transportation and utility lifeline systems. There are seven (7) transportation systems that include highways, railways, light rail, bus, ports, ferry and airports. There are six (6) utility systems that include potable water, wastewater, natural gas, crude & refined oil, electric power and communications. The transportation systems inventory and expected damages from the earthquake, in terms of number of structures and locations affected, are provided in Table 4-29, while losses in millions of dollars are summarized in Table 4-30. The total value of the lifeline inventory is over $9.4 billion. This inventory includes over 274 miles of highways, 532 bridges, and 11,935 miles of pipes.
Utility Lifeline Systems Inventory: The replacement value of the transportation and utility lifeline systems is estimated to be $4.48 billion and $4.97 billion, respectively. The expected utility system facility damages in terms of total structures or systems affected, along with the inventory of this dataset, are summarized in Table 4-31. Economic losses in millions of dollars are found in Table 4-32. Site specific expected utility system pipeline damages (including their inventory) are included in Table 4-33, while the potable water and electric power system performance limitations, damages, and inventory will be in Table 4-34.
Table 4-29 Essential Facility Inventory and Expected Damage
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-60
Table 4-30 Transportation Systems Inventory and Expected Damage by Number of Locations
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-61
Table 4-31 Transportation System Econ omic Losses in Millions of Dollars
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-62
Table 4-32 Expected Utility System Facility Inventory and Damages
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-63
Table 4-33 Utility System Economic Losses in Millions of Dollars
Source: Hazus-MH 4.2
Table 4-34 Expected Utility System Pipeline Damage (Site Specific)
Source: Hazus-MH 4.2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-64
Table 4-35 Expected Potable Water and Electric Power System Performance
Source: Hazus-MH 4.2
Beyond the modeling estimates of Hazus-MH, there are several other critical facilities which are unique to Merced County and are crucial to the function of the wider region and the state of California. The California Aqueduct, part of the California State Water Project, runs through the western part of Merced County. The State Water Project is a water storage and delivery system of reservoirs, aqueducts, power plants, and pumping plants. Its main purpose is to store water and distribute it to 29 urban and agricultural water suppliers in Northern California, the San Francisco Bay Area, the San Joaquin Valley, the Central Coast, and Southern California. The State Water Project makes deliveries to two-thirds of California's population. An earthquake event, or landslides triggered by one, which damage the aqueduct could disrupt the aqueduct’s ability to deliver water, which would have serious impacts to agriculture in the county and water users in many areas of California. Similarly, Interstate 5 runs through the western portion of the county and serves as a major shipping and transportation corridor for all of California and the west coast of the United States. Any damage or impacts to Interstate 5 in Merced County from an earthquake would result in disruptions to the entire state.
Economy
Hazus estimates the long-term economic impacts to the region. The model quantifies this information in terms of income and employment changes within the region. The total economic loss estimated for the earthquake is $4.6 Billion, which includes building and lifeline related losses based on the region's available inventory. An estimated 14% of losses computed by Hazus were related to the business interruption of the region.
Since the building losses are broken into two categories (of direct building losses compared to business interruption losses), building-related losses, which summarize estimated costs to fix or replace structures and damages to properties and their contents, are discussed in more detail in Table 4-26 of this section.
However, business interruption losses are summarized herein. They included the temporary living expenses for people displaced from their homes because of the earthquake event. These business-related economic losses are included in Table 4-35 below.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-36 Building-Related Economic Loss Estimates in Millions of Dollars
Source: Hazus-MH 4.2
Historic, Cultural, and Natural Resources
Earthquake effects on the environment, natural resources, and historic and cultural assets could be very destructive depending on the type of seismic activity experienced and secondary/cascading effects from an event (e.g. wildfire). The biggest impact would likely be on older properties such as wooden or masonry buildings, though reinforced masonry structures would be much more resilient during earthquakes.
Future Development
Future development in the county is not anticipated to significantly affect vulnerability to earthquakes when designed according to modern building codes. However future development will result in a slight increase in exposure of the population, building stock, and related infrastructure to earthquakes.
Risk Summary
Ɣ Merced County is located in a geologically complex and seismically active region, albeit less so than other areas of California. There are numerous active and potentially active faults in close proximity to the County. The County does not have a history of significant damaging earthquakes.
Ɣ The overall significance of earthquakes is Medium but ranked High for communities on the western side of the county including Dos Palos and Gustine and in the more densely populated cities such as Merced.
Ɣ A moderate earthquake occurring in or near Merced County could result in deaths, casualties, property damage, agricultural and environmental damage, and disruption of normal government and community services and activities.
Ɣ The location of the epicenter as well as the time of day and season of the year would have a profound effect on the number of deaths and casualties, as well as property damage.
Ɣ The hazard of earthquakes varies from place to place, dependent upon the regional and local geology.
Ɣ Effects on people: Hazus probabilistic scenario modeling of worst case ground shaking results in estimates of 488-1,132 people needing hospitalization and between 10-65 deaths depending on the time of day the earthquake hits.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-66
Ɣ Effects on property: Hazus probabilistic scenario modeling indicates about 17,106 buildings will be at least moderately damaged, with approximately $2.4 billion in losses.
Ɣ Effects on economy: The total economic loss estimated for a large earthquake is $4.6 billion, which includes building and lifeline related losses based on the region's available inventory. An estimated 14% of losses computed by Hazus were related to the business interruption of the region.
Ɣ Effects on critical facilities and infrastructure: Essential facility damage (police, fire, school, medical) is predicted to be low; only 246 hospital beds (51%) would be available during the earthquake. Utility lifeline systems impacts would be significant particularly to bridges; moderate damage can be expected to water, wastewater, power and communications facilities; loss of water and power would be significant in the days and weeks following the earthquake.
Ɣ Cascading and Secondary Effects: Earthquakes can cause many cascading effects such as fires, flooding, hazardous materials spills, utility disruptions, landslides, and transportation emergencies.
Ground shaking may cause tsunamis or seiche, the rhythmic sloshing of water in lakes or bays.
Table 4-37 Hazard Risk Summary - Earthquake
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Significant Unlikely Critical Medium
City of Atwater Extensive Occasional Critical Medium
City of Dos Palos Extensive Occasional Critical Medium
City of Gustine Significant Likely Critical Medium
City of Livingston Limited Occasional Limited Medium
City of Los Banos Limited Likely Limited Medium
City of Merced Extensive Occasional Critical Medium
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-67
4.2.4 Flood & Levee Failure
Hazard Description
Floods are among the most frequent and costly natural disasters in terms of human hardship and economic loss. Floods can cause substantial damage to structures, bridges and roadways, landscapes, and utilities as well as life safety issues. Certain health hazards are also common to flood events. Standing water and wet materials in structures can become breeding grounds for microorganisms such as bacteria, mold, and viruses. This can cause disease, trigger allergic reactions, and damage materials long after the flood. When floodwaters contain sewage or decaying animal carcasses, infectious disease becomes a concern. Direct impacts, such as drowning, can be limited with adequate warning and public education about what to do during floods. Where flooding occurs in populated areas, warning and evacuation will be of critical importance to reduce life and safety impacts.
Floodplains are defined as the areas immediately adjacent to a channel from a river, stream, or other waterway. Floodplains are illustrated on inundation maps, which show areas of potential flooding and water depths. In its common usage and based on FEMA guidelines, the floodplain most often refers to the area that is inundated by the 100-year flood, or the flood that has a one percent chance occurrence in any given year of being equaled or exceeded. The 100-year flood is the national minimum standard to which communities regulate their floodplains through the FEMA NFIP. The 500-year flood is the flood that has a
0.2 percent chance of being equaled or exceeded in any given year. A 500-year flood event would be slightly deeper and cover a greater area than a 100-year flood event. The potential for flooding can change and increase through various land use changes and changes to land surface, which then may result in a change to the floodplain. A change in environment can create localized flooding problems inside and outside of natural floodplains by altering or confining natural drainage channels. These changes are most often created by human activity.
A levee is a raised area that runs along the banks of a river or canal. Levees reinforce the banks and help prevent flooding. By confining the flow, levees can also increase the speed of the water. Levees can be natural or manmade. A natural levee is formed when sediment settles on the riverbank, raising the level of the land around the river. To construct a manmade levee, workers pile dirt or concrete along the riverbanks, creating an embankment. This embankment is flat at the top, and slopes at an angle down to the water. For added strength, sandbags are sometimes placed over dirt embankments.
Levees provide strong flood protection, but they are not failsafe. Levees are designed to protect against a specific flood level and could be overtopped during severe flood events. Levees reduce, not eliminate, the risk to individuals and structure behind them. A levee system failure or overtopping can create severe flooding and high-water velocities. It’s important to remember that no levee provides protection from events for which it was not designed, and proper operation and maintenance are necessary to reduce the probability of failure.
Riverine flooding - Riverine flooding, defined as the condition when a watercourse (e.g. river or channel) exceeds its “bank-full” capacity, generally occurs as a result of prolonged rainfall, or rainfall that is combined with already saturated soils from previous rain events. This type of flood occurs in river systems whose tributaries may drain large geographic areas and include one or more independent river basins.
The onset and duration of riverine floods may vary from a few hours to many days. Factors that directly affect the amount of flood runoff include precipitation amount, intensity and distribution, the amount of soil moisture, seasonal variation in vegetation, snow depth, and water-resistance of the surface due to urbanization. Intense storms can overwhelm the local waterways as well as the integrity of any flood control structures. The warning time associated with slow rise floods assists in life and property protection DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-68
Localized flooding - Localized flooding problems are often caused by flash flooding, severe weather, or an unusual amount of rainfall. Flooding from these intense weather events usually occurs in areas experiencing an increase in runoff from impervious surfaces associated with development and urbanization as well as inadequate storm drainage systems.
Levee Failure – Flooding from the failure of levees throughout the county or upstream is also of concern.
A catastrophic flood control structural failure could easily overwhelm local response capabilities to save lives and require mass evacuations. Impacts to life safety will depend on the warning time and the resources available to notify and evacuate the public. Loss of life could result, and there could be associated health concerns as well as negative effects to local buildings and infrastructure.
The potential for flooding can change and increase through various land use changes and changes to land surface, which result in changes to the floodplain. Environmental changes can create localized flooding problems in and outside of natural floodplains by altering or confining natural drainage channels. These changes are most often created by human activity.
Encroachment into areas subject to inundation by floodwaters having rapid flows aggravates the risk of flood damage and heightens potential flood hazards by further increasing velocities. To reduce the risk of property damage in areas where the stream flows are high, the community may wish to restrict development in areas outside the floodway. FEMA defines a regulatory floodway as the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. The floodway is illustrated in Figure 4-13 below. The area between the floodway and 1-percent-annual-chance floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the water surface elevation of the base flood more than 1 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in schematic in the following.
Figure 4-13 Floodway Schematic
Source: Guidance for Flood Risk Analysis and Mapping – FEMA, 2019
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-69
Geographic Area
The Merced River, in the central part of California, is a 145-mile (233 km)-long tributary of the San Joaquin River flowing from the Sierra Nevada into the Central Valley. It is most well-known for its swift and steep course through the southern part of Yosemite National Park, and the world-famous Yosemite Valley. The river's character changes dramatically once it reaches the foothills and the lowlands, becoming a slow- moving waterway meandering through irrigated fields. Large-scale irrigated agriculture was introduced to the Central Valley in the late 19th century, and led to the construction of numerous state, federal and privately owned dams.
The San Joaquin River swings northwest, passing through many different channels, some natural and some manmade. Northeast of Dos Palos, it is joined by the Fresno and Chowchilla Rivers. Fifty miles downstream, the Merced River (highlighted below in Figure 4-14) empties into the San Joaquin. Canal and flood control development in the late 1800’s and early 1900’s redirected water flow and managed waterways through a series of canals, water storage and agricultural levies. This led to the conversion on thousands of acres of lake basin land into farmable ground.
Figure 4-14 Merced River
Source: Merced County website
The Tenaya, Yosemite, Bridalveil, and Pigeon Creeks join the Merced River before it breaches the glacial moraine at the valley's end. From there the river picks up Cascade Creek and turns south near El Portal, flowing through Merced River Canyon. State Route 140 follows the river out of the west entrance to the national park, a few miles before the South Fork Merced River, the largest tributary, joins from the left. The river arcs northwest to receive the North Fork, and a few miles after it enters Lake McClure, formed by New Exchequer Dam. Below New Exchequer, the river flows west through a heavily irrigated region of the Central Valley, passing through McSwain and Crocker-Huffman Dams and the cities of Hopeton, Delhi and Livingston. It joins the San Joaquin River at Hills Ferry, a few miles south of Turlock. There are also many lakes in the watershed of the Merced River, including Merced Lake, Tenaya Lake, the Chain Lakes, May Lake, Lake McClure, and Lake McSwain. The Merced River is the third largest tributary of the San Joaquin River.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-70
The primary cause of local flooding is due to the drainage patterns that flow towards the San Joaquin River Basin and Merced County. The numerous tributaries of the San Joaquin – the Fresno, Chowchilla, Merced, Tuolumne, Mariposa Creek, Calaveras, Mokelumne, and others flowed freely across alluvial flood plains to join the river. All of the major tributaries of the river originate in the Sierra Nevada. Most of the streams that start in the Coast Range are intermittent and contribute little to the flow of the San Joaquin.
During the winter, spring, and early summer, storms and snowmelt swell the river. In 1914 – before the development of major dams and irrigation diversions – the California Department of Engineering estimated the river's flow in full flood at 325,000 cubic feet per second (cfs). In late summer and autumn, there is little water left over to replenish stream flow.
The floodplain of the Merced River is well defined from the eastern county boundary to approximately 10 miles above the mouth of the river. Downstream of this point, the floodplain is undifferentiated from the valley floor and major floods can spread out over large areas. Floodplain storage reduces peak flows in the downstream direction. With the diminishing channel capacity of the Merced River, flood hazards increase. During the 1950 flood event, approximately 19,600 acres of land along the Merced River were inundated, including the towns of Snelling and Merced Falls.
The Merced River's primary human use is irrigation. The Merced Irrigation District (MID) operates most of the irrigation infrastructure, which supplies water to 154,394 acres (624.81 km 2) of farmland. The Irrigation
District and watershed are shown in Figure 4-15. As a whole, the system includes about 4,000 sets of control gates and 793 miles (1,276 km) of canals. Irrigation has taken most of the water out of the lower river, which now rarely reaches the sea. Water that does return to the river does so in for form of irrigation return flows, which carry pesticides, fertilizer and other pollutants. The MID is federally required to allow at least 15,000-acre feet (19,000,000 m3) of water annually to flow continually down the river, not including flooding. The water has allowed the San Joaquin River below the Merced River confluence to contain water, while above the confluence all its water is usually diverted for irrigation.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-71
Figure 4-15 Merced Irrigation District Watershed System Source: MID
The physical risks associated with potential flooding and the regulatory requirements for floodplain management are important considerations when decisions are being made regarding future land use throughout the County. Those same risks guide the local and community-level emergency response needs. Economic growth and prosperity in Merced County are dependent upon federal, state, and local agency involvement on regional and local flood management systems. Flood protection regulations within California have been increased over the past few years through legislation. This legislation included the requirement for the California DWR and Central Valley Flood Protection Board to prepare and adopt a Central Valley Flood Protection Plan (CVFPP) by 2012. The legislation also established certain flood protection requirements for local land use decision making based on the CVFPP. The law sets a higher standard for flood protection for the entire San Joaquin Valley. The standard was set for an urban level flood protection necessary to withstand a 1 in 200 chance of a flood event occurring in any given year (200-year flood) for areas developed or planned to have a population of at least 10,000. It also requires impacted counties to collaborate with cities to develop flood emergency response plans. Figure 4-16 shows the extent of this 200-year flood event based on the Best Available Maps (BAM) developed by California DWR.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-72
Figure 4-16 Merced County 200-year Floodplain
Source: USACE, Wood Planning Team
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In 2009, FEMA completed their DFIRM conversion and updated a number of flood zone areas using 2005 levee certification criteria. In 2007, the California DWR completed their Awareness Floodplain Mapping of Merced County to identify all pertinent flood hazard areas that are not mapped under FEMA’s program, which provides an additional resource for identifying special flood hazard areas within the County.
Extent (Magnitude/Severity)
The FEMA and the Federal Insurance Administration have assessed flood hazards for major streams in Merced County. A large portion of Merced County continues to be subject to inundation during flood events, as approximately 380,010 acres have been determined to be in the FEMA floodplain. The extent of the floodplain is shown in Figure 4-17. Both a 100-year and 500-year flood event scenario are critical events in Merced County as the flooding would cover at least 35 to 50 percent of the County. More detailed maps are in the jurisdictional annexes.
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2021-2026 Update Page 4-74
Figure 4-17 Merced County 100-year and 500-year Floodplain
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The largest flood of record on the Merced River was 46,200 cubic feet per second (cfs) and occurred on December 4, 1950, downstream of Old Exchequer Dam (built in Mariposa County in 1926). The New Exchequer Dam, which has more flood storage capacity, was built in 1967. Based on USGS stream data, the largest discharges along the Merced River since the construction of New Exchequer Dam occurred in 1983 followed by 1997.
During the major flood events in 1969, 1997, 1998, and 2006, Bear Creek overflowed at the southwest end of the City of Merced in the vicinity of Thornton Avenue and State Highway 140. Stream gauge data is not available to quantify the magnitude of these events. Historical records also indicate that Bear Creek overflowed its banks upstream from the G Street Bridge. This overflow was worsened by debris restricting flow under the bridge. The largest flood on the San Joaquin River since the completion of Friant Dam in 1943 occurred in 1997. Along the San Joaquin River during the past century, the five largest flood events include, in order of magnitude, those from 1997, 1938, 1983, 1969, and 2006 based on USGS data. The historical San Joaquin River floodplain widens from approximately 3 to 4 miles in the reach south of Merced County to approximately 19 miles in central Merced County. This large expansion of the floodplain is accompanied by a decrease in channel slope. The floodplain then narrows to approximately 2 miles downstream of the Merced River in the northern part of the county.
Previous Occurrences
Between 1992 and 2002, every county in California was declared a federal disaster area at least once for a flooding event. California has a chronic and destructive flood history. Of the 336 federally declared disasters in California between 1950 and 2020, 37 were flood related. This makes flooding second only to fire in the number of federal disaster declarations in the state. Historically, floods have been the most frequent cause of disaster in Merced County.
Significant flooding occurs in Merced County approximately every five years. Merced County has had two flood events that were federally declared disasters, once in 1969 and again in 2017. FEMA’s Flood Insurance Study also listed flooding events in 1937-38, 1950, 1955, 1969, 1983, 1997, 1998, and 2006.
Additionally, NOAA’s National Centers for Environmental Information (NCEI) database lists 54 flood or flash flood events which have occurred in the county between 1950 and 2020.
Table 4-37 below highlights several notable flood events in the county that resulted in significant damages or involved federal disaster declarations.
Table 4-38 Major Floods in Merced County
Date of Event Incident Description
January-February
1969
A series of storms delivered 12-50 inches of rainfall over an 8-day period throughout Central and Southern California. This affected the San Joaquin Valley and resulted in the first federal disaster for flood in Merced County.
March 25, 1998 A series of thunderstorms brought locally heavy rain to the City of Merced area, resulting in rainfall totals for 24 hours ending by the morning of the 25th from 3.5" to 5.9" in the Merced City area. One gauge in the north part of town showed 6.8" in the 48-hour period from the evening of the 23rd to the evening of the 25th. Over 1000 people were evacuated from Merced City and nearby County areas. Over 65 homes and 19 apartments were flooded in and around Merced City as the result of torrential/record-setting rainfall in the previous 18 hours. According to the NCEI database, $9.6 million in property damage and $1.5 million in crop damages occurred during this event.
October 24, 1998 The cool season's first significant rain pushed through Central California. Merced received
0.75” of rain in embedded frontal thundershowers and locally heavy rain in about 2 hours.
Some local street flooding was reported just south of Hilmar and within Delhi. In Merced a DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Date of Event Incident Description
tree was toppled by the storm. Several traffic accidents occurred on rain-slickened roads.
According to NCEI, this event also resulted in $120,000 in property damage and six injuries.
January 10, 2005
Heavy rain resulted in water overflowing from Bear Creek in the Merced area from heavy rainfall damaged a handful of homes on the 11th, and $200,000 in property damages.
March 22, 2005 Over 4 inches of rain fell in a 24-hour period in the Mariposa County area of Central California, upstream of Merced County. Numerous small creeks flooded in Mariposa, Merced, and Madera Counties. Flooding caused damage to structures within the town of Mariposa and several bridges and roads in and around Hornitos, Merced Falls, and Catheys Valley in Merced and Mariposa Counties. $250,000 in property damage was recorded.
April 4, 2006 Due to continued heavy rain and subsequent high stream flows, a break in Black Rascal Creek flooded homes in north Merced. And Bear Creek raised over its banks in West Merced flooding a residential section in that vicinity. Overall, there were approximately 300 homes flooded around Merced with over 500 people evacuated during the event. $9.72 million in property damage.
March 27, 2011 During the frequently stormy period that began on the 18th and ended on the 28th, as much as 7 inches of rain fell in the San Joaquin Valley and up to 10 inches of rain drenched the adjacent foothills while the higher elevations of the Sierra (above 7000 feet) received snow accumulations of up to 15 feet. Excessive runoff combined with an increase in reservoir releases at the major dams caused higher than normal flows along rivers and streams through the end of the month. The Merced River at Stevinson peaked a half of a foot below flood stage at 4:30 pm on the 21st but otherwise remained well above monitor stage during the last two weeks of the month. Water levels along the San Joaquin River approached levels that had not been observed since January 1997. In Merced County, several water swollen creeks briefly flowed out of their banks on the morning of the 20th and caused minor flooding. The event caused $500,000 in property damage.
November 30, 2012 California highway patrol reported a multi-vehicle accident in heavy rain on Highway 99 at west side boulevard. Involved three cars and a big rig. Number of injuries unknown at this time. $120,000 in damages were also recorded.
February 1-23,
2017
On March 19, 2017, Governor Edmund G. Brown Jr. requested a major disaster declaration due to severe winter storms, flooding, and mudslides during the period of February 1-23, 2017. The Governor requested a declaration for public assistance for 42 counties and Hazard Mitigation statewide. Merced County was included in the declaration.
Source: NCEI Storm Events Database, FEMA
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Figure 4-18 Image of Past Flooding in Merced County
Source: Fox 26 News, Images of February 2017 flooding
Probability of Future Occurrences
Due to the history of past flooding events and the natural drainage pattern of the planning area, flooding in Merced County is likely to continue to occur. The potential for failure of one of the many levees throughout the county could create more risk for flooding. The 100-year flood is the flood that has a one percent chance in any given year of being equaled or exceeded. Based on past events, flooding events less severe than a 100-year flood and those outside of the 100-year floodplain occur frequently during periods of heavy rains. According to the NCEI Storm Events Database, there have been 54 flood events recorded for Merced County between 1990 and 2020. Utilizing the methodology explained in subsection
4.1.1, this means there is a 180% chance of a flood event occurring in a given year. Significant flooding occurs in Merced County approximately every five years.
Climate Change Considerations
California’s Fourth Climate Assessment found that costs associated with direct climate change impacts by 2050 will be dominated by human mortality, coastal damage, and the potential for droughts and mega- floods (California Natural Resources Agency 2018). Scientific studies outlined in the same assessment also indicated shifts in California’s precipitation regime, which show more dry days, more dry years, a longer dry season, and increases in occasional heavy precipitation events and floods. Studies also project greater storm intensity with climate change, resulting in more direct runoff and flooding (California Natural Resources Agency 2018). As a result, high frequency flood events in conjunction with heavy precipitation events and extreme storm events will increase with climate change. Certain climate studies noted in the Fourth Climate Assessment also forecast that during periods with heavy rain and frequent storm events there is an increase in flood events, as well as landslide and debris flow (California Natural Resources Agency 2018). For example, during the 2016-2017 winter, the storms resulted in many secondary hazards, including numerous landslides and in some watersheds an increased sediment load. Also, with wildfires already being a problem in California, increasing periods of drought and lack of precipitation are expected
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to exacerbate conditions for fires to occur, and in turn worsen the potential for runoff and flooding associated with burned areas.
The Fourth Climate Assessment also includes nine reports for the nine regions in California. According to the preview for the San Joaquin Valley Region Summary Report, which has not yet been published at the time of this plan update, the frequency of catastrophic floods will increase in the coming years. This in turn will lead to increased stresses to agriculture, natural ecosystems, water resources, land use and community development, transportation, energy, public health, and climate justice.
Vulnerability Assessment
While there are some benefits associated with flooding, such as the replenishment of sediments and nutrients to agricultural lands, it is considered a hazard to development in floodplains. Floods can cause many cascading effects. Fire can break out as a result of dysfunctional electrical equipment. Hazardous materials can also get into floodways, causing health concerns and polluted water supplies. In many instances during a flood, the drinking water supply will be contaminated. During the 2021 update the following vulnerability analysis using GIS was performed to quantify flood risk.
General Property
Historically, Merced County has been at risk to flooding primarily during the winter and spring months when river systems in the county swell with heavier rainfall and runoff from winter snowmelt. Normally, storm floodwaters are kept within defined limits by a variety of storm drainage and flood control measures. But occasionally, extended heavy rains result in floodwaters that exceed normal high-water boundaries and cause damage. Flooding has occurred in the past within the 100-year floodplain and in other localized areas.
A flood vulnerability assessment was performed for Merced County using the following GIS methodology.
The County’s parcel layer and associated assessor’s building improvement valuation data were provided by the County and were used as the basis for the inventory. Merced County’s effective DFIRM was used as the hazard layer. A DFIRM is FEMA’s flood risk data that depicts the 1% annual chance (100-year) and the
0.2% annual chance (500-year) flood events; this data is incorporated into the National Flood Hazard Layer (NFHL). Merced County’s effective FEMA DFIRM, dated December 2, 2009, was determined to be the best available floodplain data. Figure 4-17 summarizes the flood zones included on these maps.
GIS was used to intersect the parcel boundaries with a master address point layer to obtain the number of buildings per parcel. Only parcels with improvement values greater than zero were used in the analysis, this method assumes that improved parcels have a structure of some type. The DFIRM flood zones were overlaid in GIS on the address points to identify structures that would likely be inundated during a 1% annual chance and 0.2% annual chance flood event. This overlay can be seen graphically in the regional maps in Figure 4-17, and in more detail in the jurisdictional annexes.
Building improvement values and counts for those points were then extracted from the parcel/assessor’s data and summed for the unincorporated county and jurisdictions. Results of the overlay analysis area shown in Table 4-38 for the 1% annual chance flood and Table 4-39 for 0.2% annual chance flood. The jurisdictional annexes provide more detailed information based on property type. Property type refers to the land use of the parcel and includes agricultural, commercial, exempt, industrial, mixed use, residential, and vacant. A loss estimate analysis was also performed based on depth damage functions developed by the Army Corp of Engineers and FEMA. The loss curves depict the expected flood losses associated with the depth of flooding at a structure. Contents values were estimated as a percentage of building value based on their occupancy type, using FEMA/HAZUS estimated content replacement values. This includes 100% of the structure value for agricultural, commercial, exempt, and open space structures, 50% for DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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multi-residential and residential structures and 150% for industrial structures. Building and contents values were totaled to obtain total exposure.
There are different depth damage curves for structure and content losses. For the purposes of this planning level analysis, an average flood depth of 2 feet is assumed. A depth damage ratio of 25% was used for structural loss, based on the FEMA damage curves, assuming a 2-foot-deep flood. A loss ratio was also calculated to express the estimated losses in relation to the total value of all property in the jurisdiction, including property values not exposed to the floodplain boundaries. The results are shown in the loss estimate columns in Table 4-38 for the 1% annual chance flood.
The result is an inventory of the number and types of improved parcels subject to flooding. Results are presented by unincorporated county and incorporated jurisdictions. Detailed tables show counts of parcels by jurisdictions and land use type (agricultural, commercial, exempt, industrial, multi-residential, open space and residential) within each flood zone. It is important to note that there could be more than one structure or building on an improved parcel (i.e., a condo complex occupies one parcel but might have several structures). This flood loss analysis does not account for business disruption, emergency services, environmental damages, or displacement costs, thus actual losses could exceed the estimate shown. Conversely, this analysis does not differentiate parcels that may have been developed since when the county and cities adopted floodplain regulations, which would be mitigated to the 1% annual chance flood if developed in accordance with local floodplain regulations.
Table 4-39 1% Annual Chance Floodplain Exposure and Loss by Jurisdiction Jurisdiction Property
Type
Improved
Parcel
Count
Building
Count
Improved
Value
Estimated
Content Value
Total Value Estimated Loss
Atwater Commercial 4 8 $446,109 $446,109 $892,218 $223,055 Exempt 7 7 $0 $0 $0 $0
Industrial 1 1 $16,651 $24,977 $41,628 $10,407
Residential 342 344 $87,919,330 $43,959,665 $131,878,995 $32,969,749 Total 354 360 $88,382,090 $44,430,751 $132,812,841 $33,203,210 Livingston Agricultural 1 1 $7,441 $7,441 $14,882 $3,721 Total 1 1 $7,441 $7,441 $14,882 $3,721
Merced Agricultural 17 19 $704,235 $704,235 $1,408,470 $352,118 Commercial 527 1,873 $339,551,353 $339,551,353 $679,102,706 $169,775,677 Exempt 433 960 $9,185,588 $9,185,588 $18,371,176 $4,592,794 Industrial 118 218 $167,406,079 $251,109,119 $418,515,198 $104,628,799 Mixed Use 9 9 $185,869 $185,869 $371,738 $92,935
Residential 9,161 12,140 $1,218,507,813 $609,253,907 $1,827,761,720 $456,940,430 Vacant
Land
30 38 $1,030,699 $1,030,699 $2,061,398 $515,350
Total 10,295 15,257 $1,736,571,636 $1,211,020,769 $2,947,592,405 $736,898,101 Unincorporated Agricultural 2,240 2,920 $571,674,871 $571,674,871 $1,143,349,742 $285,837,436 Commercial 182 516 $45,633,503 $45,633,503 $91,267,006 $22,816,752 Exempt 84 115 $9,565,302 $9,565,302 $19,130,604 $4,782,651 Industrial 57 82 $63,423,427 $95,135,141 $158,558,568 $39,639,642 Mixed Use 15 17 $233,502 $233,502 $467,004 $116,751
Residential 2,697 2,967 $319,577,554 $159,788,777 $479,366,331 $119,841,583 DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Jurisdiction Property
Type
Improved
Parcel
Count
Building
Count
Improved
Value
Estimated
Content Value
Total Value Estimated Loss
Vacant
Land
25 26 $131,577 $131,577 $263,154 $65,789
Total 5,300 6,643 $1,010,239,736 $882,162,673 $1,892,402,409 $473,100,602 Grand
Total
15,950 22,261 $2,835,200,903 $2,137,621,633 $4,972,822,536 $1,243,205,634 Source: Merced County Assessor’s Office; NFHL Effective date 12/02/2008, FEMA; GIS analysis Large areas of Merced County are at risk of being inundated by a 100-year flood event. The City of Merced, City of Atwater, and unincorporated areas of the County are predominantly inundated by the 100-year floodplain and have the greatest percentages of total loss from a 100-year flood event. While other jurisdictions are far less at risk during in a 100-year flood event, several jurisdictions including Dos Palos and Gustine are at a greater risk of inundation in the event of a 200-year flood.
Based on this analysis, the Merced County planning area has 15,950 parcels and 22,261 buildings valued over $2.8 billion in the 100-year floodplain. An additional 2,904 parcels and 3,866 buildings valued at roughly $596 million fall within the 500-year floodplain. As a result, total structural exposure is approximately $4.4 billion. When factoring the content values within these areas in addition to the structures the total combined value of exposure is $6.1 billion. Development in the 500-year floodplain is typically not regulated, thus a large flood event could be extremely damaging in the County and Merced.
This information is summarized in Table 4-39 below.
Table 4-40 0.2% Annual Chance Floodplain Exposure and Loss by Jurisdiction Jurisdiction Property
Type
Improved
Parcel
Count
Building
Count
Improved
Value
Estimated
Content
Value
Total Value Estimated
Loss
Merced Commercial 30 31 $62,378,180 $62,378,180 $124,756,360 $31,189,090 Exempt 33 69 $0 $0 $0 $0
Mixed Use 2 3 $41,361 $41,361 $82,722 $20,681
Residential 1,594 2,412 $337,480,454 $337,480,454 $674,960,908 $168,740,227 Total 1,659 2,515 $399,899,995 $399,899,995 $799,799,990 $199,949,998 Unincorporated Agricultural 204 262 $39,295,471 $39,295,471 $78,590,942 $19,647,736 Commercial 6 14 $9,074,287 $9,074,287 $18,148,574 $4,537,144 Exempt 6 6 $3,145,199 $3,145,199 $6,290,398 $1,572,600
Mixed Use 4 4 $148,839 $148,839 $297,678 $74,420
Residential 1,022 1,062 $144,732,798 $144,732,798 $289,465,596 $72,366,399 Vacant
Land
3 3 $6,699 $6,699 $13,398 $3,350
Total 1,245 1,351 $196,403,293 $196,403,293 $392,806,586 $98,201,647 Grand
Total
2,904 3,866 $596,303,288 $596,303,288 $1,192,606,576 $298,151,644 Source: Merced County Assessor’s Office; NFHL Effective date 12/02/2008, FEMA; GIS analysis Another method of assessing flood vulnerability is through the utilization of the California DWR BAM which display a 200-year floodplain. The BAM does not replace existing FEMA regulatory floodplains, but rather identifies potential flood risks that may warrant further studies or analysis. Analyzing this floodplain data in the same way as described above revealed an estimated additional 2,159 buildings exposed to flood hazard throughout the unincorporated portions of Merced County.
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Insurance Coverage, Claims Paid, and Repetitive Losses
Unincorporated Merced County joined the NFIP in 1979. All of the jurisdictions in the county, with the exception of Gustine, are NFIP participants. The County currently does not participate in the optional CRS, nor do any of the jurisdictions.
In the unincorporated county, there are 1,558 policies in force, of which there are 1,285 single family units, 4 2-4 family, three all other residential, and 266 nonresidential. The number of policies in force by jurisdiction and flood zone are shown in Table 4-40 below. The City of Gustine is not included as it is not a NFIP participant.
Table 4-41 Merced County Community Informati on System Policies in Force by Flood Zone and Jurisdiction
Flood Zone Merced
County
City of
Merced
City of
Los
Banos
City of
Livingston
City of Dos
Palos
City of
Atwater
A01-30 & AE
Zones
33 275 0 0 0 0
A Zones 411 51 0 0 0 0
AO Zones 240 573 0 0 0 0
AH Zones 80 114 0 0 0 0
AR Zones 0 0 0 0 0 0
A99 Zones 0 0 0 0 0 0
V01-30 & VE
Zones
0 0 0 0 0 0
V Zones 0 0 0 0 0 0
D Zones 0 0 0 0 0 0
B, C & X Zone
Standard 51 59 0 3 0 1
Preferred 62 119 16 1 3 13
Total 877 1,191 16 4 3 14
Source: FEMA NFIP Community Information System
NFIP data indicates that there are 4,987 insurance policies in Merced County representing $1,084,286,000 of insurance coverage in force. Since 1979 there have been 281 paid losses, totaling $ 4,484,055. Most of the losses have been in the City of Merced and the unincorporated county. Table 4-41 provides more details on flood insurance policies for each individual jurisdiction.
FEMA insures properties against flooding losses through the NFIP. As part of the process to reduce or eliminate repetitive flooding to structures across the United States, FEMA has developed an official Repetitive Loss Strategy. The purpose behind the national strategy is to identify, catalog, and propose mitigation measure to reduce flood losses to the relatively few numbers of structures that absorb the majority of the premium dollars from the national flood insurance fund.
A repetitive loss property is defined by FEMA as “a property for which two or more NFIP losses of at least $1,000 each have been paid within any 10-year period since 1978”. A repetitive loss property may or may not be currently insured by the NFIP. There are 13 repetitive loss buildings in the unincorporated county, 3 of which are insured and a total of $367,067 was paid out. There are no Severe Repetitive Loss properties, as defined by FEMA, anywhere in the County.
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Table 4-42 Merced County Flood Insurance Policy Information Jurisdiction Policies Insurance in Force No. of Paid Losses Total Losses Paid Atwater 14 $4,018,000 1 $1,740
Dos Palos 3 $553,000 0 $0
Gustine N/A N/A N/A N/A
Livingston 4 $665,000 0 $0
Los Banos 16 $5,180,000 0 $0
Merced 3,401 $772,521,900 151 $2,230,265
Unincorporated 1,558 $301,348,300 129 $2,252,050
Total 4,996 $1,084,286,000 281 $4,484,055
Source: FEMA NFIP Community Information System
People
The total number of residential properties in each floodplain was multiplied by the average household size of 3.32 persons for the County (ACS 2019 estimates) to estimate resident population within mapped flood hazard areas. Based on this analysis, which accounts for residents only and not workers, there are 49,878 residents living in the 100-year flood zone throughout the County. Of all study areas, the City of Merced has the most residents living in the 1% annual chance flood area, followed by the unincorporated county. Table 4-42 below details population estimates by jurisdiction, followed by similar tables for the 500-year floodplain.
Table 4-43 Population Living in the 1% Annual Chance Flood Hazard Zone Jurisdiction Population
Atwater 1,094
Merced 38,877
Unincorporated County 9,907
Total 49,878
Source: Wood GIS analysis on Merced County Assessor’s Office data and FEMA NFHL, ACS Census Estimates The same analysis was conducted for the 500-year floodplain, indicating that there are 11,267 residents living in the 500-year flood zone throughout Merced County. The majority of people living in this floodplain are residents of the City of Merced, with almost 8,000 people in the 500-year floodplain. This population distribution is shown in the table below.
Table 4-44 Population Living in the 0.2% Annual Chance Flood Hazard Zone Jurisdiction Population
Merced 7,728
Unincorporated County 3,539
Total 11,267
Source: Wood GIS analysis on Merced County Assessor’s Office data and FEMA NFHL, ACS Census Estimates Critical Facilities and Infrastructure
Key support facilities and structures most necessary to withstand the impacts of, and respond to, natural disasters are referred to as critical facilities. Examples of these critical facility types include utilities, transportation infrastructure, and emergency response and services facilities, given failures of components along major lifelines or even closures or inaccessibility to key emergency facilities could limit if not DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-83
completely cut off transmission of commodities, essential services, and other potentially catastrophic repercussions. Floods and levee failure have the ability to disrupt, damage, or destroy these critical facilities, which in turn can impede the ability of Merced County to respond to and recover from a major flood event.
A GIS analysis of exposed critical facilities was conducted, similar to the parcel analysis, using HIFLD. The results of critical facilities throughout the county which are exposed to the various flood hazards are shown in Table 4-444 and Table 4-45 below, and organized by the jurisdiction they are located in and the FEMA Lifeline category into which they are classified.
Table 4-45 Critical Facilities Within the 1% An nual Chance Flood Hazard by FEMA Lifeline and Jurisdiction
Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Atwater 2 2 1 - - 1 4 10
Dos Palos - - - - - - - 0
Gustine - - - - - - - 0
Livingston - - - - - - - 0
Los Banos - - - - - - - 0
Merced 26 3 30 15 6 51 25 156
Unincorporated 13 5 13 11 - 34 180 256
Total 41 10 44 26 6 86 209 422
Source: HIFLD, FEMA NFHL
Table 4-46 Critical Facilities Within the 0.2% An nual Chance Flood Hazard by FEMA Lifeline and Jurisdiction
Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Atwater - - - - - - - 0
Dos Palos - - - - - - - 0
Gustine - - - - - - - 0
Livingston - - - - - - - 0
Los Banos - - - - - - - 0
Merced - - 2 - 2 5 - 9
Unincorporated 1 - - - - 5 1 7
Total 1 0 2 0 2 10 1 16
Source: HIFLD, FEMA NFHL
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2021-2026 Update Page 4-84
Economy
Flooding can have a major economic impact on the economy. Based on the flood loss analysis, there are 2,397 commercial structures worth an estimated $771 million in total value directly at risk to flooding in the 1% annual chance zone. Based on the loss analysis this could result in approximately $193 million in direct losses. This does not account for other indirect losses such as business interruption, lost wages and other downtime costs.
Effects on the agriculture economy can be devastating, and a large amount of area at risk to flooding in the County is agricultural. Flooding can damage crops and livestock. In addition to the obvious impacts on crops and animals, flooding can have deleterious effects on soil and the ability to reinvigorate the agricultural activities impacted once the flood waters recede. Damage to water resources such as underground irrigation systems, water storage reservoirs, springs and other natural water bodies could have a serious effect upon agriculture operations.
Historic, Cultural, and Natural Resources
There are 15 properties throughout the County on the NRHP. Most of these places are located in the City of Merced, which has the highest risk and exposure to flood hazards.
Natural areas within the floodplain often benefit from periodic flooding as a naturally recurring phenomenon. These natural areas often reduce flood impacts by allowing absorption and infiltration of floodwaters. Natural resources are generally resistant to flooding except where natural landscapes and soil compositions have been altered for human development or after periods of previous disasters such as drought and fire. Wetlands, for example, exist because of natural flooding incidents. A large percentage of flood prone area in the County are wetlands that are part of the San Luis and Merced National Wildlife Refuges. These areas provide natural and beneficial functions to hold and absorb floodwaters. Areas recently suffering from wildfire damage may erode because of flooding, which can temporarily alter an ecological system.
Future Development
Flooding and floodplain management are significant issues for Merced County. The potential or likelihood of a flood event in the county increases with the annual onset of heavy rains in winter and spring months.
Much of the historical growth in the problem areas connected with flooding and stormwater runoff include erosion, sedimentation, degradation of water quality, losses of environmental resources, and certain health hazards. For NFIP participating communities, floodplain management practices implemented through local floodplain management ordinances should mitigate the flood risk to new development in the 100-year floodplains. As noted previously, a large amount of development has occurred in the 500-year floodplain and these areas are not regulated or require flood mitigation.
The development trend in the Merced County planning area is steady growth. Much of this growth is occurring in the urban areas, which can increase stormwater runoff. The 2020 Caltrans Economic Forecast at the county-level for all 58 counties in California for 2018-2050, projects that Merced County’s population will continue to increase by 1.3 percent through 2025. Such growth may consume previously undeveloped acres, and the increase in impervious surfaces could affect existing drainage and flood control facilities.
Changes in municipal boundaries such as annexations into the SOI may change the flood risk profile for certain communities. A GIS analysis of 1% annual chance flood exposure within SOI boundaries is summarized in the tables below.
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2021-2026 Update Page 4-85
Table 4-47 Sphere of Influence Risk to FEMA 1% Annual Chance Flood Hazard Sphere of
Influence
Improved
Parcel
Count
Building
Count
Improved
Value
Estimated
Content
Value
Total Value Estimated
Loss
Population Loss
Ratio
Atwater 72 80 $9,559,223 $6,160,259 $15,719,482 $3,929,871 169 1.4% Livingston 1 1 $103,862 $103,862 $207,724 $51,931 0 0.2% Merced 908 1,121 $154,013,086 $111,545,194 $265,558,280 $66,389,570 2,673 7.5% Total 981 1,202 $163,676,171 $117,809,315 $281,485,486 $70,371,372 2,842
Table 4-48 Sphere of Influence Risk to FEMA 0.2% Annual Chance Flood Hazard Sphere
of
Influence
Improved
Parcel
Count
Building
Count
Improved
Value
Estimated
Content
Value
Total Value Estimated
Loss
Population Loss
Ratio
Atwater 1 1 $81,844 $40,922 $122,766 $30,692 3 0.01%
Merced 80 86 $29,663,971 $17,321,531 $46,985,502 $11,746,375 249 1.3% Total 81 87 $29,745,815 $17,362,453 $47,108,268 $11,777,067 252
Risk Summary
The overall significance of the flood hazard is High. The 100-year floodplain in Merced County is vast, and many thousands of residents and millions in property value are within the floodplain.
Ɣ Countywide there are 22,261 structures at risk worth $4.9 billion, with a loss estimate of $1.2 billion.
Ɣ The City of Merced accounts for 59% of the total losses in the 100-year floodplain. 48% of the City of Merced’s buildings are in the floodplain.
Ɣ Commercial structures account for 15.5% of total losses in the 100-year floodplain, with a loss estimate of $193M
Ɣ Countywide approximately 49,878 persons live in the 100-year floodplain, of which the vast majority (38,877) are in the City of Merced.
Ɣ There are 11,267 persons within the 500-year floodplain and a flood of this magnitude would have severe consequences.
Ɣ Levees and flood control dam infrastructure provide some protection, but also pose potential levee and dam failure risks.
Ɣ A total of 438 critical facilities are found in 1% annual chance (422 facilities) and 0.2% annual chance (16 facilities) flood zones in the county. Most of them are in the City of Merced or in the unincorporated areas of the county.
Ɣ Related hazards: Severe weather: Heavy Rain, Wildfire, Landslide and Debris Flow.
Table 4-49 Hazard Risk Summary – Flood & Levee Failure
Jurisdiction Geographic
Extent
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Likely Catastrophic High
City of Atwater Extensive Likely Critical Medium
City of Dos Palos Limited Occasional Limited Low
City of Gustine Significant Occasional Critical Medium
City of Livingston Limited Occasional Negligible Medium DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-86
Jurisdiction Geographic
Extent
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
City of Los Banos Limited Likely Limited Medium
City of Merced Significant Likely Limited Medium
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2021-2026 Update Page 4-87
4.2.5 Landslide
Hazard Problem/Description
A landslide is a geologic hazard where the force of gravity combines with other factors to cause earth material to move or slide down an incline. Some landslides move slowly and cause damage gradually, whereas others move so rapidly that they can destroy property and take lives suddenly and unexpectedly.
Slopes with the greatest potential for sliding are between 34 degrees and 37 degrees. Although steep slopes are commonly present where landslides occur, it is not necessary for the slopes to be long.
Debris flows are a mixture of rock fragments, soil, vegetation, water and, in some cases, entrained air that flows downhill as a fluid. Debris flows can range in consistency from that of freshly mixed concrete to running water. Debris flows can be further classified as mudflows and earth flows depending on the ratio of water to soil and rock debris.
Landslide and debris flow problems can be caused by land mismanagement, particularly in mountain, canyon, and coastal regions. In areas burned by forest and brush fires, a lower threshold of precipitation may initiate landslides and debris flows. As human populations expand over more of the land surface, these processes become an increasing concern.
There are predictable relationships between local geology and landslides, rockslides, and debris flows. The downslope movement of earth material, either as a landslide, debris flow, mudslide, or rockslide, is part of the continuous, natural process of erosion. This process, however, can be influenced by a variety of causes that change the stability of the slope. Slope instability may result from natural processes, such as the erosion of the toe of a slope by a stream, or by ground shaking caused by an earthquake. Slopes can also be modified artificially by grading, or by the addition of water or structures to a slope. Development that occurs on a slope can substantially increase the frequency and extent of potential slope stability hazards.
Knowledge of these relationships can improve planning and reduce vulnerability. Slope stability is dependent on many factors and their interrelationships, including rock type, moisture content, slope steepness, and natural or manmade undercutting.
Geographic Area
In Merced County the landscape is largely characterized by the San Joaquin Valley, which is relatively flat and takes up the majority of the central portion of the county. To the eastern edge of the county, lying within the foothills of the Sierra Nevada range, and the western edge, within the Coast Range, there are several geologic formations commonly associated with slope stability problems. Figure 4-19 below provides a summary of landslide hazard potential. As shown in the map, the areas of the county with the greatest potential susceptibility to landslide hazards are in the far southwest of the county, on the western side of Interstate 5. This area is all unincorporated area in the county and is largely rural in character, indicating a lower potential risk to property and infrastructure relative to other counties in California.
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2021-2026 Update Page 4-88
Figure 4-19 Merced County Deep-Seated Landslide Susceptibility
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2021-2026 Update Page 4-89
Extent (Magnitude/Severity)
The extent of landslides and debris flow events within the county range from negligible to significant.
Landslides and rockslides can result in the destruction of infrastructure such as water and sewer lines, electrical and telecommunications utilities and drainage where they are present. There is potentially risk to Interstate 5, near the county border with Fresno County. There is limited potential for complete destruction of buildings and death and injury from landslides and debris flow.
Previous Occurrences
There have not been any disaster declarations associated with landslides in Merced County. According to records from the California Department of Conservation’s Geological Survey, there have been no recent records of landslides in Merced County and no active mapping efforts within the county. Several adjacent counties, such as Madera, Mariposa, and Santa Clara, have recent or active landslides which have been recorded. This historic record would indicate that landslides occasionally occur in Merced County, but largely affect undeveloped areas.
Probability of Future Occurrences
Based on historical data which suggests limited risk of landslides, but given the presence of landslide susceptible geology and steep slopes within the planning area, it is safe to assume that landslides may occur in the future, with damaging landslides occurring much less frequently. Landslides are usually a cascading effect of severe weather or a period of extended wet weather that saturates local soils. The probability for more severe and damaging landslides increases during El Niño years or severe winter storms. The potential for debris flows dramatically increases following a wildfire.
Climate Change Considerations
Landslides can result from intense rainfall and runoff events. Projected climate change-associated variance in rainfall events may result in more high-intensity events, which may increase landslide frequency. In addition, the increased potential of wildfire occurrence also escalates the risk of landslide and debris flows in the period following a fire, when slopes lack vegetation to stabilize soils and burned soil surfaces create more rainfall runoff. As climate change affects the length of the wildfire season, it is possible that a higher frequency of large fires may occur into late fall, when conditions remain dry, and then be followed immediately by intense rains early in the winter, as occurred with the Thomas Fire in December 2017 and subsequent Montecito and Carpinteria debris flows in January 2018 in Santa Barbara County (CA SHMP 2018).
Vulnerability Assessment
General Property
Landslides directly damage engineered structures in two general ways: 1) disruption of structural foundations caused by differential movement and deformation of the ground upon which the structure sits, and 2) physical impact of debris moving downslope against structures located in the travel path.
During the 2021 update of this plan, a GIS analysis of exposure to landslide hazard areas was performed.
GIS analysis indicates approximately $317 million of property improvements exposed, which takes into account improved values of properties. Table 4-49 summarizes landslide exposure by jurisdiction. GIS was used to intersect the parcel boundaries with a master address point layer to obtain the number of buildings per parcel. Only parcels with improvement values greater than zero were used in the analysis, this method assumes that improved parcels have a structure of some type.
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2021-2026 Update Page 4-90
Based on this analysis there is a total of 482 improved parcels and 547 buildings potentially within landslide hazard areas. The majority of this exposure is in the western unincorporated county. There is a high level of uncertainty as to the actual risk to these exposed parcels, thus a more specific loss estimation is not provided. A more detailed, site specific analysis would be needed to assess actual risk within the identified parcels.
Table 4-50 Merced County Improved Properties at Risk to Landslide Jurisdiction Improved
Parcel
Count
Total
Building
Count
Improved
Value
Estimated
Content Value
Total Value Population
Atwater 11 11 $3,479,587 $2,831,312 $6,310,899 32
Livingston 1 1 $2,714,360 $1,357,180 $4,071,540 4
Merced 27 42 $4,762,383 $2,381,192 $7,143,575 112
Unincorporated 443 493 $156,446,776 $142,936,749 $299,383,525 322 Total 482 547 $167,403,106 $149,506,432 $316,909,538 470 Source: Dept. of Conservation, California Geological Survey, Merced County Assessor, Wood GIS Analysis Figure 4-20 below further breaks down the numbers of exposed buildings by landslide class, as shown previously in Figure 4-19; the higher the class the greater the susceptibility.
Figure 4-20 Total Building Counts by Landslide Class
People
People could be susceptible if they are caught in a landslide or debris flow, potentially leading to injury or death. There is also a danger to drivers operating vehicles, as rocks and debris can strike vehicles passing through the hazard area or cause dangerous shifts in roadways. The parcel analysis described previously estimated the number of people potentially residing in landslide susceptible areas (470), but it is not likely that landslides will occur without warning and direct impacts to people are suspected to be minimal. 0 100 200 300 400 500 600
Class 3 Building Count
Class 5 Building Count
Class 6 Building Count
Class 7 Building Count
Class 8 Building Count
Class 9 Building Count
Class 10 Building Count
Total Building Count
TTota ll Buildin gg Count ss byy Landslid ee Class
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2021-2026 Update Page 4-91
Critical Facilities and Infrastructure
In addition to buildings, utilities and transportation structures are vulnerable to the impact and ground deformation caused by slope failures. They present a particular vulnerability because of their geographic extent and susceptibility to physical distress. Lifelines are generally linear structures that, because of their geographic extent, have a greater chance of being affected by ground failure due to greater hazard exposure.
Extension, bending, and compression caused by ground deformation can break lifelines. Failure of any component along the lifeline can result in failure to deliver service over a large region. Once broken, transmission of the commodity through the lifeline ceases, which can have catastrophic repercussions down the line: loss of power to critical facilities such as hospitals, impaired disposal of sewage, contamination of water supplies, disruption of all forms of transportation, release of flammable fuels, and so on. Therefore, the overall impact of lifeline failures, including secondary failure of systems that depend on lifelines, can be much greater than the impact of individual building failures.
Table 4-50 below summarizes the results of the critical facilities analysis, highlighting the exposure of critical facilities throughout the county to landslide hazards. All of the exposed critical facilities are located in unincorporated areas of the county, largely to the west of Interstate 5.
Table 4-51 Critical Facilities Within the Class 9 Landslide Hazard by FEMA Lifeline Jurisdiction Landslide
Class
Communi-
cations Energy
Food,
Water,
Shelter
Hazardous
Material
Health
and
Medical
Safety
and
Security
Transportation Total
Uninc.
9 2 26 - - - - - 28
8 1 48 - - - - - 49
7 - 4 - - - - 46 50
6 1 - - - - - - 1
5 4 80 - - - - 3 87
3 1 - - - - - - 1
Total 9 158 0 0 0 0 49 216
Source: California Geological Survey, HIFLD, Wood GIS Analysis Economy
Economic impacts typically center around transportation routes temporarily closed by debris flow or landslide activity. These roads may be used to transport goods across the county or provide access by visitors and tourists. Depending on the amount of damage, the road may simply need to be cleaned off, or may require some level of reconstruction.
Historic, Cultural, and Natural Resources
As primarily a natural process, landslides and debris flows can have varying impacts to the natural environment; debris flows have the potential to permanently alter the natural landscape.
Future Development
The severity of landslide problems is directly related to the extent of human activity in hazard areas.
Human activities such as property development and road construction can also exacerbate the occurrence of landslides. Future development should take place carefully to prevent landslide damage to property or people. Adverse effects can be mitigated by early recognition and avoiding incompatible land uses in DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-92
these areas or by corrective engineering. Improving mapping and information on landslide hazards and incorporating this information into the development review process could prevent siting of structures and infrastructure in identified hazard areas. The 2030 General Plan has provisions to address this goal, by prohibiting habitable structures atop unconsolidated landslide debris, discouraging grading and construction on slopes greater than 30%, and enforcing grading standards of the International Building Code.
Risk Summary
The overall significance of landslides in Merced County is low.
Ɣ The geologic formations commonly associated with slope stability problems in Merced County, are largely concentrated in the far western and eastern edges of the county, which are also the least populated.
Ɣ Effects on people: People are most commonly at risk if they are caught in a landslide or debris flow, including when driving through a hazard area.
Ɣ Effects on property: Property loss is rare, but GIS analysis shows there is some property which could be exposed to landslides.
Ɣ Effects on economy: Landslides in adjacent counties can disrupt major transportation corridors, possibly affecting the local tourist economy and shipment of goods.
Ɣ Effects on critical facilities and infrastructure: Landslides and debris flows can result in the destruction of infrastructure such as water and sewer lines, electrical and telecommunications utilities and drainage. Disrupted transportation routes occur occasionally, usually during heavy rainstorms, and cause considerable inconvenience.
Ɣ Related Hazards: Earthquake, Adverse Weather, Wildfire.
Table 4-52 Hazard Risk Summary - Landslides
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Limited Occasional Limited Low
City of Atwater N/A
City of Dos Palos N/A
City of Gustine N/A
City of Livingston N/A
City of Los Banos N/A
City of Merced N/A
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-93
4.2.6 Severe Weather: General
The climate in the Central Valley is defined generally by hot, dry summers and foggy, rainy winters. Severe weather is generally any destructive weather event, but usually occurs in Merced County as localized thunderstorms that bring heavy rain and strong winds that occur most often during the winter and spring months. The agricultural industry is among the most vulnerable asset to severe weather. Agricultural losses resulting from natural hazards can have dramatic impacts on the economic health of Merced County.
For this plan, adverse weather is broken down as follows:
Ɣ Freeze
Ɣ Extreme Heat
Ɣ Dense Fog
Ɣ Heavy Rain
Ɣ High Wind/Tornado
The National Oceanic and Atmospheric Administration’s NCEI has been tracking adverse weather since 1950. Their Storm Events Database contains data on the following: all weather events from 1993 to 2017 (except from 6/1993-7/1993); and additional data from the Storm Prediction Center, which includes tornadoes (1950-1992), thunderstorm winds (1955-1992), and hail (1955-1992). This database contains 254 storm events that occurred in Merced County between January 1, 1950, and December 2020. The table below summarizes these events.
Table 4-53 NCEI Hazard Event Re ports for Merced County, 1950-2020 Hazard # of Events Property Loss ($) Crop Loss ($) Deaths Injuries Dense Fog* 102 $1,160,00 $0 3 7
Frost/Freeze* 31 $0 $0 0 0
Heavy Rain 23 $2,007,500 $15,660,000 0 0
Strong Wind* 20 $90,800 $513,000 0 0
Funnel Cloud 18 $0 $0 0 0
Tornado 14 $410,000 $50,000 0 1
Heat* 13 $0 $0 0 0
High Wind* 12 $995,000 $2,110,000 0 4
Hail 9 $30,000 $1,233,000 0 4
Lightning 8 $1,000,000 $0 0 1
Thunderstorm Wind 4 $430,000 $3,100,000 0 0
Total 254 $4,963,300 $22,666,000 3 17
Source: NCEI Storm Events Database, www.ncdc.noaa.gov/stormevents/ *Hazards with wide extents reflect larger zones that extend beyond Merced County.
The NCEI table above summarizes adverse weather events that have occurred in Merced County from 1950 to 2020. Only a few of the events actually resulted in state and federal disaster declarations. It is interesting to note that different data sources capture different events during the same time period, and often different information specific to the same events. While the HMPC recognizes these inconsistencies, this data provides value in depicting the County’s “big picture” hazard environment.
Due to size of the County and changes in elevation and climate, weather conditions can vary greatly across the County. The profiles that follow provide information, where possible, from two weather stations in different parts of the County: Merced Municipal Airport Weather Station in the northeastern part of the county (1889-2016) and the Los Banos City weather station in the southwestern part of the county (1906- 2016). The temperature data from these two weather stations are displayed in subsection 4.3.7 below.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-94
4.2.7 Severe Weather: Extreme Temperatures: Freeze and Extreme Heat Hazard/ Problem Description
Extreme temperature events, both cold and hot, can have severe impacts on human health and mortality, natural ecosystems, and agriculture and other economic sectors.
Freeze
Extreme cold often accompanies a winter storm or is left in its wake. Prolonged exposure to cold can cause frostbite or hypothermia and can be life-threatening. Infants and the elderly are most susceptible.
Pipes may freeze and burst in homes or buildings that are poorly insulated or without heat. Freezing temperatures can cause significant damage to the agricultural industry.
Extreme Heat
Extreme heat events can have severe impacts on human health and mortality, natural ecosystems, the agriculture sector and other economic sectors. According to information provided by FEMA, extreme heat is defined as temperatures that hover 10 degrees or more above the average high temperature for the region and last for several weeks. Heat kills by taxing the human body beyond its abilities, usually from heat stroke. In a normal year, about 175 Americans succumb to the demands of summer heat. According to the NWS, among natural hazards, only the cold of winter—not lightning, hurricanes, tornadoes, floods, or earthquakes—takes a greater toll. As a compar ison, in the 40-year period from 1936 through 1975, nearly 20,000 people were killed in the United States by the effects of heat and solar radiation. In the heat wave of 1980, more than 1,250 people died. The 2018 California State Hazard Mitigation Plan (SHMP) notes the 2006 heat wave led to 650 deaths in a 13-day period (Cal OES 2018) and in the past 15 years heat waves have claimed more lives in California than all other declared disaster events combined (California Climate Adaptation Strategy 2018).
Heat disorders generally have to do with a reduction or collapse of the body’s ability to shed heat by circulatory changes and sweating or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body’s inner core begins to rise, and heat related illness may develop. The elderly, small children, individuals who work outside, patients with chronic medical conditions, those on prescription medication therapy, and people with weight and alcohol problems are particularly susceptible to heat reactions, especially during heat waves in areas where moderate climate usually prevails.
Geographic Area
Freeze
The entire county is susceptible to extreme temperatures. Unseasonable cold temperatures can have large impacts on crops in Merced County. The growing season is approximately 257 days per year, and the frost-free period usually extends from mid-February to mid-November. The mean frost-free period in the western part of the county is 225-250 days.
Extreme Heat
The climate in Merced County is hot and arid, and the entire county is susceptible to extreme heat. The agriculturally dominated central region of the county is likely to experience the greatest impacts from large or unseasonable temperature variations. The more urbanized areas of the County may experience the Urban Heat Island Effect due to the amount of impervious surfaces in those areas that absorb and keep heat longer. The HMPC noted the cities of Merced and Dos Palos have experienced annual summer heat waves that have taken place in the past five years and have led to opening of cooling centers.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Extent (Magnitude/Severity)
Freeze
In 2001, the NWS implemented an updated Wind Chill Temperature index. This index was developed to describe the relative discomfort/danger resulting from the combination of wind and temperature. Wind chill is based on the rate of heat loss from exposed skin caused by wind and cold. As the wind increases, it draws heat from the body, driving down skin temperature and eventually the internal body temperature.
Overall, freeze impacts would likely be limited in the planning area, with the greatest impact being on the agricultural industry.
Figure 4-21 National Weather Service Wind Chill Chart
Source: NWS
Extreme Heat
Figure 4-22 illustrates the relationship of temperature and humidity to heat disorders. The heat index describes how hot the heat-humidity combination makes the air feel. As relative humidity increases, the air seems warmer than it actually is because the body is less able to cool itself via evaporation of perspiration. As the heat index rises, so do health risks. Specifically:
Ɣ When the heat index is 90°F, heat exhaustion is possible with prolonged exposure and/or physical activity.
Ɣ When it is 90° to 105°F, heat exhaustion is probable with the possibility of sunstroke or heat cramps with prolonged exposure and/or physical activity.
Ɣ When it is 105° to 129°F, sunstroke, heat cramps or heat exhaustion is likely, and heatstroke is possible with prolonged exposure and/or physical activity.
Ɣ When it is 130°F and higher, heatstroke and sunstroke are extremely likely with continued exposure.
Physical activity and prolonged exposure to the heat increase the risks.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Figure 4-22 National Weather Service Heat Index Chart
Source: Source: NWS Note: Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15°F. Also, strong winds, particularly with very hot, dry air, can be extremely hazardous.
The NWS has a system in place to initiate alert procedures (advisories, watches, and warnings) when high temperatures are expected to have a significant impact on public safety. The expected severity of the heat determines which type of alert is issued. The “California OES Contingency Plan for Excessive Heat Emergencies” (2014) indicates that through the use of historical weather and mortality data, the NWS and the California Department of Public Health have identified five major types of climate regions within California to account for climate differences among regions in order to recognize what constitutes an excessive heat event in each of the regions. When temperatures spike for two or more consecutive days without an adequate drop in nighttime temperature to cool the outdoor and indoor environments, there is a significant increase in the risk to vulnerable populations.
Overall, extreme heat impacts would likely be limited in the planning area, with the central portions of the County being most affected. Extreme heat will have an impact on vulnerable populations as well as impact the agricultural industry if the event occurs during certain times of the year.
Past Occurrences
A search of records from 1950 to 2020 in the NCEI Storm Events Database showed that between 2000 and 2016 there were 31 frost and freeze events and 13 heat events in Merced County. No records for either hazards were found between 1950 and 2000 or after 2016 in the NCEI database. Since 1972 there have been 4 federally declared disaster in the County for freeze events (refer to Table 4-3). In 2007, 2009 and 2011 and 2012 the USDA designated Merced County as a disaster area due to freeze and extreme cold.
During these events, California's San Joaquin Valley farming communities were hit with freezing temperatures that severely affected the region's crops and resulted in presidential disaster declarations (2007). The declarations made federal funds available to supplement unemployment compensation for farm laborers and other farm industry workers put out of work as a direct result of lost seasonal crops.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Probability of Future Occurrences
Highly Likely - Temperatures at or above 95°F are common most summer days throughout Merced County, and it is highly likely that extreme heat will continue to occur on an annual basis in the future.
In the past, severe freezes have occurred every few years. Based on the NCEI data, 31 frost and freeze events incidents over a 16-year period equates to a major event every 2 years and a 52 percent chance of a major freeze event in any given year.
Climate Change Considerations
Although heat waves will likely become more frequent, there is also the potential for continued cold outbreaks in winter, even in an overall warmer climate. This could have direct impacts on human health in terms of heat related illness. With the general trend of increased warming of average temperatures, extreme high temperatures will likely increase as well. Cascading impacts include increased stress on water quantity and quality, degraded air quality, and increased potential for more severe or catastrophic natural events such as heavy rain, droughts, and wildfire. Another cascading impact includes increased duration and intensity of wildfires with warmer temperatures. According to the 2013 document, “Preparing California for the Extreme Heat”, Cal-Adapt projects that throughout California urban and rural population centers will experience an average of 40 to 53 extreme heat days by 2050 and an average of 40 days by 2099; compared to a historical average of 4 per year (Cal-Adapt 2013).
Extreme heat has also been shown to accelerate wear and tear on the natural gas system and electrical infrastructure (California Natural Resources Agency 2018a). Projected increases in summer demand associated with rising temperatures may increase risks to energy infrastructure and may exceed the capacity of existing substations and distribution line infrastructure and systems.
Vulnerability Assessment
General Property
The risks of extreme temperatures are often profiled as part of larger hazards, such as severe winter storms or drought. However, as temperature variances may occur outside of larger hazards or outside of the expected seasons but still incur large costs, it is important to examine them as stand-alone hazards.
Extreme cold may also lead to higher electricity and natural gas demands to maintain appropriate indoor heating levels combined with damages caused to the delivery infrastructure such as frozen lines and pipes. Cold temperatures may also impact transportation infrastructure and road conditions through increased wear and stresses on asphalt roads and bridges. Exposed populations may be at risk while waiting for public transportation, particularly when combined with wind chill, and some vehicles may not start, which impacts the commute of the workforce and, in worst case scenarios, the movement of emergency services personnel.
Recent research indicates that the impact of extreme heat, particularly on vulnerable (?) populations, has been historically under-represented. The risks of extreme heat are often profiled as part of larger hazards, such drought or wildfire. However, as temperature variances may occur outside of larger hazards or outside of the expected seasons but still incur large costs, it is important to examine them as stand-alone hazards. Extreme heat may overload demands for electricity to run air conditioners in homes and businesses during prolonged periods of exposure and presents health concerns to individuals that work outside in extreme temperatures. While extreme heat rarely damages buildings, like cold temperatures it can cause infrastructure damage to roads.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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People
Traditionally, the very young and very old are considered at higher risk to the effects of extreme temperatures, but any populations working or recreating outdoors during periods of extreme cold or heat are exposed, including otherwise young and healthy adults and homeless populations. While everyone is vulnerable to extreme temperature incidents, some populations are more vulnerable than others. Extreme heat poses the greatest danger for Merced’s thousands of outdoor laborers who support the County’s agriculture economy who are exposed to extreme temperatures and at higher risk of heat related illnesses than other populations of the county.
The elderly, children, people in poor physical health, and the homeless are also vulnerable to exposure.
Arguably, the young-and-otherwise-healthy demographic may also experience a higher vulnerability of exposure, due to the increased likelihood that they will be out in temperatures of extreme heat and cold, whether due to commuting for work or school, conducting property maintenance such as lawn care, or for recreational reasons.
Critical Facilities
Water infrastructure is at risk from freezing, including line breaks and frozen valve gates affecting the distribution system. The county and municipal governments wrap pipes before freezing temperature events to help prevent damage.
Extreme heat can affect road infrastructure, damaging and buckling road surfaces. Other direct impacts to critical infrastructure includes power line sagging and power surges. Critical infrastructure such as water pumping stations that rely on public utility systems that could be overloaded may result in impacts during extreme heat events. Peak demand exceeding the local utility’s capacity for supply can lead to blackout or brownout conditions, or Public Safety Power Shutoffs (PSPS). The loss of utilities or power outages during extreme heat events could also result in adverse secondary impacts to sensitive populations. Electrical power outages may impact response capabilities or care capabilities for hospitals and clinics.
Economy
Prolonged freezing temperatures can damage or destroy crops, affecting the economy and agricultural jobs in Merced County. According to the USDA RMA Indemnity Report, since 2007 there have been 22,308 acres lost to freeze/frost resulting in $12,933,721 indemnity payments due to insured crop loss.
Annualized crop loss is estimated to be $170,181 due to freeze events.
Extreme heat impacts on the economy may be more indirect compared to other hazards. Merced County has a large agriculture economy. As noted previously outdoor laborers who are exposed to extreme heat and at a high risk of heat related illnesses, and a long-term heat event could cause work interruptions.
Crops are also impacted by heat events and could have an impact on the overall economy in the county.
According to the USDA RMA Indemnity Report, since 2007 there have been 20,207 acres lost to heat resulting in $17,612,071 indemnity payment due to insured crop loss. There is an estimated $187,362 of annualized crop loss due to heat.
Historic, Cultural and Natural Resources
Extreme heat may cause temporary drought-like conditions. For example, several weeks of extreme heat increases evapotranspiration and reduces moisture content in vegetation, leading to higher wildfire vulnerability for that time period even if the rest of the season is relatively moist. Extreme cold can cause vegetation to freeze and cause high stress leading to decline and even disappearance of vegetation on or within landscapes.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Future Development
Since structures are not usually directly impacted by severe temperature fluctuations, continued development is less impacted by this hazard than others in the plan. However, pre-emptive measures such as construction of green buildings that require less energy to heat and cool, use of good insulation on pipes and electric wirings, and smart construction of walkways, parking structures, and pedestrian zones that minimize exposure to severe temperatures may help increase the overall durability of the buildings and the community to temperature variations. Continued development also implies continued population growth, which raises the number of individuals potentially exposed to variations in temperature. Public education efforts should continue to help the population understand the risks and vulnerabilities of outdoor activities, property maintenance, and regular exposures during periods of extreme heat.
Risk Summary
Ɣ Average annual maximum temperature is 76°F and the average annual minimum temperatures is 47°F /48°F.
Ɣ On average there is between 97 and 98 days per year above 90°F and about 30 days per year where the minimum temperatures is below freezing (32°F).
Ɣ Highest recorded temperatures for the northwestern portion of County is 114°F on July 24, 1902.
While the lowest recorded temperature was 13°F on January 13, 2007.
Ɣ High recorded temperatures for the southwestern portion of County is 116°F on July 25, 1931. The lowest recorded temperatures is 14°F on January 11, 1949.
Ɣ Extreme temperatures can have considerable impacts on human health, the natural environment and the economy.
Ɣ The County’s agriculture economy is at risk of extreme temperatures from outdoor laborers being vulnerable to heat illnesses as well as crop losses due to heat and freeze and frost.
Ɣ Since 2007 there has been 42,515 acres of crop lost to extreme temperatures and a combined $30,545,793 indemnity payments made for insured crop loss to due freeze/frost and heat events.
Ɣ The very young, the very old, people with poor physical health and the homeless are more susceptible to the impacts of extreme temperatures.
Ɣ Climate change is projected to increase temperatures in the Central Valley region of the State.
Ɣ Related hazards: Drought, Land Subsidence, Wildfire, Agriculture/Pest Infestation/Plant Disease Table 4-54 Hazard Risk Summary – Extreme Temperatures (Freeze) Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Highly Likely Critical High
City of Atwater Limited Likely Limited Low
City of Dos Palos Significant Likely Limited Medium
City of Gustine Limited Occasional Negligible Medium
City of Livingston Limited Occasional Negligible Medium City of Los Banos Limited Occasional Negligible Medium
City of Merced Significant Likely Limited Low
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Table 4-55 Hazard Risk Summary – Extreme Temperatures (Extreme Heat) Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Highly Likely Critical High
City of Atwater Extensive Likely Limited High
City of Dos Palos Extensive Likely Negligible Low
City of Gustine Extensive Likely Limited High
City of Livingston Extensive Likely Limited High
City of Los Banos Significant Highly Likely Negligible Medium City of Merced Extensive Highly Likely Limited Medium
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4.2.8 Severe Weather: Dense Fog
Hazard/Problem Description
Fog results from air being cooled to the point where it can no longer hold all of the water vapor it contains. For example, rain can cool and moisten the air near the surface until fog forms. A cloud-free, humid air mass at night can lead to fog formation, where land and water surfaces that have warmed up during the summer are still evaporating water into the atmosphere. This is called radiation fog. A warm moist air mass blowing over a cold surface also can cause fog to form, which is called advection fog.
The interior California valleys have a unique fog problem called the tule fogs. The tule fog is a radiation fog, which condenses when there is a high relative humidity, typically after a heavy rain, calm winds, and rapid cooling during the night. The longer nights during the winter months create this rapid ground cooling and results in a pronounced temperature inversion at a low altitude, creating a thick ground fog.
Above the cold, foggy layer, the air is typically warm and dry. Once the fog has formed, turbulent air is necessary to break through the inversion. Daytime heating can also work to evaporate the fog in some areas. The tule fogs get their name from the tule reeds, which grew around the swamps and deltas of the great Tulare Lake that once covered the southern end of the San Joaquin Valley.
The tule fog season in Merced County is typically in the late fall and winter (November through March) but can occur as late as May. Fog typically forms rapidly in the early morning hours. Tule fogs can last for days, sometimes weeks. Fog can have devastating effects on transportation corridors in the County.
Nighttime driving in the fog is dangerous and multi-car pileups have resulted from drivers using excessive speed for the conditions and visibility. Tule fog has also been found to be connected to air pollution and exacerbates the naturally occurring fog. A study published in the Journal of Geophysical Research in 2019 found that air pollution is a key contributor to the seasonal fog, and due to the passage of the Clean Air Act in 1970, it has declined about 75 percent since 1980 (Gray 2019).
Figure 4-23 Tule Fog over Central Valley
Source: NASA, Jeff Schmaltz, January 5, 2005
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Geographic Area
The San Joaquin Valley is hemmed in on three sides by mountain ranges, with resulting inversion layers trapping cooler air on the valley floor. This predisposes the area to severe episodes of fog in winter months, when barometric pressures are high, humidity is increased, and ambient temperatures are low. All areas of the county are vulnerable to dense fog events.
Extent (Magnitude/Severity)
Tule fog forms on clear nights when the ground is moist, and the wind is near calm and can be widespread throughout the San Joaquin Valley. On nights like this, the ground cools rapidly. In turn, the moist air above it cools and causes water vapor to condense. Once it has formed, the air must be heated enough to either evaporate the fog or lift it above the surface so that visibilities improve. Common areas for tule fog to form include foothills and valleys. Visibility in tule fog is usually less than an eighth of a mile (about 600 ft or 200 m) but can be much lower. Visibility can vary rapidly; in only a few feet, visibility can go from 10 feet (3.0 m) to near zero.
Fog contributes to transportation accidents and is a significant life safety hazard. These accidents can cause multiple injuries and deaths and could have serious implications for human health and the environment if a hazardous or nuclear waste shipment were involved. Other disruptions from fog include delayed emergency response vehicles and school closures.
In 2018 the NWS in Hanford, California developed the Experimental Fog Severity Index in conjunction with the NWS issues fog advisories to help give motorists advance warning of fog events. A dense fog advisory is issued when widespread dense fog develops, and visibilities drop to one-quarter of a mile or less. The Fog Severity Index has five levels with level 5 being the most severe. Figure 4-24 describes each level of the Index.
Figure 4-24 National Weather Servi ce Experimental Fog Severity Index
Source: NWS
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Past Occurrences
The NCEI records 102 dense fog events in the Central San Joaquin Valley that impacted Merced County between 2000 and 2020 (refer to Table 4-52 above). The following are descriptions of three events of record in the NCEI Storm Events Database:
Ɣ November 14 - 20 2002 - Following the very substantial rain for the 3-day period from the 7th through the 9th of the month, high pressure aloft built and resided over Interior Central California.
This weather regime, quite conducive to dense morning fog formation, established itself between the 10th and 13th, and maintained itself through the end of the month. The fog was especially widespread from the 14th through the morning of the 21st. Numerous vehicle accidents occurred due to the extremely poor visibilities on Central and Southern San Joaquin Valley roadways. On the 20th along a 3-mile stretch of Highway 99 just north of the Merced-Madera County Line, 50 trucks and cars were involved in multi-vehicle pileups.
Ɣ December 1-5, 2002 - With the large rainfall amounts on the San Joaquin Valley floor by November 9th, haze and fog prevailed subsequently for a 30+-day period while the adjacent foothills, mountains, and Kern Desert dried again in rainless conditions. Widespread dense fog from mid to late-November ceased by the morning of the 1st of December on the Valley floor. But patchy dense fog and haze prevailed from the 1st of the month through the 9th before the major precipitation in December began on the 13th. The morning of the 5th had some very dense, but again patchy fog. A 9-vehicle pile-up occurred near Los Banos in Merced County (CAZ89) on Highway 152 around 8:35 AM PST that killed one and injured three others.
Ɣ January 10, 2019 - Visibility below a quarter mile was reported in Fresno, Madera, Merced and Atwater. Several school districts either had delayed openings or delayed morning bus service. A head on crash in dense fog near Atwater at 6:12 PST caused one fatality and three injuries.
Probability of Future Occurrences
Likely --Based on the NCEI data, 102 dense fog incidents over a 20-year period equates to a major fog event every 5.1 years and a 20 percent chance of a major fog event in any given year. It is likely that minor fog events will continue to occur annually in the Merced County planning area.
Climate Change Considerations
California’s winter tule fog has declined dramatically over the past three decades, raising a red flag for the state’s multibillion-dollar agricultural industry, according to researchers at UC Berkeley. Crops such as almonds, pistachios, cherries, apricots and peaches go through a necessary winter dormant period brought on and maintained by colder temperatures. Tule fog that descends upon the state’s Central Valley between late fall and early spring, helps contribute to this winter chill. “The trees need this dormant time to rest so that they can later develop buds, flowers and fruit during the growing season,” said biometeorologist and study lead author Dennis Baldocchi. “An insufficient rest period impairs the ability of farmers to achieve high quality fruit yields.” The findings have implications for the entire country since many of these California crops account for 95 percent of U.S. production, the authors noted. The researchers paired NASA and National Oceanic and Atmospheric Administration satellite records with data from a network of University of California weather stations, covering 32 consecutive winters. There was a great deal of variability from year to year, but on average, the researchers found a 46 percent drop in the number of fog days between the first of November and the end of February. Climate forecasts suggest that the accumulation of winter chill will continue to decrease in the Central Valley. Tule fog was also less prevalent in recent years in part due to the multi-year drought.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Vulnerability Assessment
General Property
Based on historic information, the primary effect of fog has not resulted in significant damages to property, or the losses are typically covered by insurance.
People
Reduced visibility is the greatest risk to people when heavy fog is prevalent. Particularly when fog is dense, it can be hazardous to drivers, mariners and aviators and contributes to numerous accidents each year. To reduce injury and harm, people should avoid driving when dense fog is prevalent, if possible. If driving is pertinent, emergency services advise driving with lights on low beam, watching for California Highway Patrol (CHP) pace vehicles to guide through fog, avoiding stopping on highways, and avoiding crossing traffic lanes.
Critical Facilities
Fog can have devastating effects on transportation corridors in the County. Multi-car pileups have resulted from drivers using excessive speed for the conditions and visibility.
These accidents can cause multiple injuries and deaths and could have serious implications for human health and the environment if a hazardous or nuclear waste shipment were involved. Other disruptions from fog include delayed emergency response vehicles and school closures.
Economy
Economic impacts due to dense fog are generally related to road closures leading to a decrease in travel to businesses. Other economic impacts relate to property damages to vehicles from accidents. As shown in Table 4-52 above there is a recorded $1,060,000 of property damages as a result of dense fog all of which are from traffic accidents in the Central Valley region and the records mention Merced County.
Based on that amount the Merced County region has an estimated average loss expectancy of $10,495 and annualized loss of $1,070,495 due to dense fog events.
Historic, Cultural and Natural Resources
As referred to in the Climate Change Considerations section, California’s winter tule fog has declined dramatically over the past three decades, raising a red flag for the state’s multibillion-dollar agricultural industry. Crops such as almonds, pistachios, cherries, apricots and peaches go through a necessary winter dormant period brought on and maintained by colder temperatures and tule fog that descends upon the state’s Central Valley between late fall and early spring, helps contribute to this winter chill.
Future Development
Population and commercial growth in the County and outside the County will increase the potential for complications with traffic accidents and commerce interruptions associated with dense fog.
Risk Summary
Ɣ Tule Fog season begins in late fall and lasts from winter (November – March).
Ɣ Between 2000 and 2020 there were 102 dense fog events that impacted Merced County and have resulted in $1,060,000 in property damages, largely due to traffic accidents.
Ɣ Fog can have devastating effects on transportation corridors. On November 4, 2002, a 50-vehicle collision occurred on Highway 99 near Merced.
Ɣ Major fog events in the County are estimated to occur every 5.1 years or a 20% chance in any given year.
Ɣ Related Hazards: Hazardous Materials Incidents
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-56 Hazard Risk Summary – Dense Fog
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Highly Likely Critical High
City of Atwater Extensive Highly Likely Critical High
City of Dos Palos Extensive Highly Likely Critical High City of Gustine Extensive Highly Likely Critical High City of Livingston Extensive Highly Likely Limited Medium City of Los Banos Extensive Highly Likely Limited Medium City of Merced Extensive Highly Likely Limited Medium DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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4.2.9 Severe Weather: Heavy Rain
Hazard/ Problem Description
Most of the adverse weather experienced in Merced takes place in the winter months as heavy rain and thunderstorm events sometimes accompanied by high winds, dense fog events. Dense fog is profiled under 4.2.8 and high winds and tornado events are profiled in 4.3.10.
Merced’s weather is influenced by the Pacific Ocean and routine climate patterns such as El Niño. El Niño is the warm phase of the El Niño-Southern Oscillation, a pattern found in the tropical Pacific when there are fluctuations in temperatures between the ocean and atmosphere. During El Niño, the surface winds across the entire tropical Pacific are weaker than normal and the ocean surface is at above-average temperatures in the central and eastern tropical Pacific Ocean (L’Heureux 2014). El Niño typically develops over North America during the winter season causing the severe winter storms the County often experiences. This climate pattern occurs every few years and brings with it above-average rain and snow across the southern region of United States, especially in California.
Atmospheric rivers, another climate pattern that leads to adverse weather in the County, are responsible for up to 50 percent of California’s precipitation annually and 65 percent seasonally (Arcuni 2019). An atmospheric river (AR) is a long, narrow region of the atmosphere, like a river in the sky, that transports most of the water vapor outside of the tropics. ARs can be 300 miles wide, a mile deep and more than 1,000 miles long and carry an amount of water vapor roughly the same as the average flow of water at the mouth of Mississippi River (NOAA, 2015). Warm water storms over the Pacific Ocean lead to evaporation and create a high concentration of moisture in the air. While prevailing winds create the distinctive river shape, which is often compared “to a fire hose pointed at California” (Arcuni 2019). When an atmospheric river reaches land, it releases the water vapor in the form of rain or snow. Atmospheric rivers play an important role in the global water cycle and are closely tied to both water supply and flooding risk.
Research suggests that atmospheric rivers contributed to the collapse of both Oroville Dam spillways in February 2017 (NASA Global Hydrology Resource Center), as well as the winter flooding in 1861-1862, which completely inundated Sacramento and is considered the worst flood event in California’s history (Ingram 2013). When an atmospheric river forms in the tropical regions of the Pacific near Hawaii it is known as a “Pineapple Express”. This type of atmospheric river can produce as much as five inches in one day (NOAA, 2018). In 2018 two Pineapple Express ARs hit California causing significant heavy precipitation events throughout state.
Geographic Area
Thunderstorms are generally expansive in size. The entire county is susceptible to any of the effects of a severe thunderstorm, including heavy rain.
Extent (Magnitude/Severity)
The heavy precipitation events that Merced County and all of California experiences is often the result of an atmospheric river. Atmospheric rivers are categorized by a unit of measurement known as the Integrated Water Vapor Transport (IVT), which takes into account the amount of water vapor in the system and the wind that moves it around. For a storm to be classified as an atmospheric river it has to reach an IVT threshold of 250 units; 1,000 IVT or more is considered to be “extreme” (Arcuni 2019). In 2019 a system for categorizing the strength and impacts of atmospheric rivers was developed by the Center for Western Weather and Water Extremes (CW3E), out of the Scripps Institution of Oceanography at UC San Diego. The newly developed scale ranks ARs into five categorizes from weak to exceptional.
Unlike the Fujita Scale for tornadoes that focuses on potential damages, the AR scale accounts for both storms that may be hazardous and storms that can provide benefits to the local water supply. A category DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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one AR is considered to be primarily beneficial, generally lasting only 24 hours and produces modest rainfall. While a category five AR is considered “exceptional” and primarily hazardous, lasting for several days and associated with heavy rainfall and runoff that may cause significant damages. Table 4-56 below describes the scale further. The CW3E developed the scale as a tool for officials with an operational need to assess flooding potential in their jurisdictions before the storms makes landfall.
Table 4-57 Atmospheric River Categories
Category Potential Impacts
AR Cat 1: Weak Primarily beneficial. For example, a Feb. 2, 2017 AR hit California, lasted 24 hours at the coast, and produced modest rainfall.
AR Cat 2: Moderate Mostly beneficial, but also somewhat hazardous. An atmospheric river on Nov. 19-20, 2016 hit Northern California, lasted 42 hours at the coast, and produced several inches of rain that helped replenish low reservoirs after a drought.
AR Cat 3: Strong Balance of beneficial and hazardous. An atmospheric river on Oct. 14-15, 2016 lasted 36 hours at the coast, produced 5-10 inches of rain that helped refill reservoirs after a drought, but also caused some rivers to rise to just below flood stage.
AR Cat 4: Extreme Mostly hazardous, but also beneficial. For example, an atmospheric river on Jan. 8-9, 2017 that persisted for 36 hours produced up to 14 inches of rain in the Sierra Nevada and caused at least a dozen rivers to reach flood stage.
AR Cat 5: Exceptional Primarily hazardous. For example, a Dec. 29, 1996 to Jan. 2, 1997 atmospheric river lasted over 100 hours at the Central California coast. The associated heavy precipitation and runoff caused more than $1 billion in damages.
Source: Center for Western Weather and Water Extremes, Scripps Institution of Oceanography at UC San Diego. Scale was developed by F. Martin Ralph Director of CW3E in collaboration with Jonathan Rutz of NWS In both February 2018 and 2019 the West Coast experienced six atmospheric rivers. But as the following figure from the Center for Western Weather and Water Extremes shows, California experienced vastly different precipitation totals due to the location of where the atmospheric river made landfall as well as each atmospheric river’s IVT. Using the AR scale developed by CW3E, the ARs in February 2019 were all considered to be moderate to extreme and concentrated more on California, resulting in heavy precipitation.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Figure 4-25 Atmospheric River Strength and Land Distribution, February 2018 vs. February 2019 Source: Center for Western Weather and Water Extremes, Scripps Institution of Oceanography at UC San Diego
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Past Occurrences
Heavy rains and adverse storms occur in the Merced County primarily during the late fall and winter but have a chance of occurring in every month of the year. According to information obtained from the Western Regional Climate Center (WRCC) the majority of precipitation is produced by storms during January and other winter months. Precipitation during the summer months is in the form of rain showers and is rare.
The NCEI records show heavy rainstorms can cause both widespread flooding which can lead to extensive localized drainage issues. In addition to the flooding that often occurs during these storms, strong winds, when combined with saturated ground conditions, can down very mature trees. Refer to the Flood section for more information related to flooding events in the county. There have been two USDA disaster designations (2016, 2019) for excessive rainfall in Merced County (refer to Table 4-4).
Information from the three representative weather stations introduced in subsection 4.3.6 Severe Weather: General are summarized below and in Figure 4-26 and Figure 4-27.
Northeastern Merced County - Merced Municipal Airport Weather Station (1899-2016) Information from the closest weather station with the most comprehensive data to represent the northeastern county area, the Merced Municipal Airport Weather Station, is summarized below in Figure 4-26 and Figure 4-27. Average annual precipitation recorded at this weather station is 12.27 inches per year. The highest recorded annual precipitation was 21.66 inches in 1998; the highest recorded precipitation for a 24-hour period is 2.20 inches on January 30, 1911. The lowest recorded annual precipitation was 5.50 inches in 1947.
Figure 4-26 Merced Municipal Airport Weather Station Monthly Average Total Precipitation (Period of Record 1899-2016)
Source: WRCC, www.wrcc.dri.edu/
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Figure 4-27 Merced Municipal Airport Weather Station Daily Precipitation Average and Extreme (Period of Record 1899-2016)
Source: WRCC, www.wrcc.dri.edu/
Southwestern Merced County - Los Banos City Weather Station (1906-2016) Information from the closest weather station with the most comprehensive data to represent the southwestern county area the Los Banos Weather Station, is summarized below in Figure 4-28 and Figure 4-29. Average annual precipitation recorded at this weather station is 9.19 inches per year. The highest recorded annual precipitation was 21.08 inches in 1998; the highest recorded precipitation for a 24-hour period is 2.40 inches on January 18, 1914. The lowest recorded annual precipitation was 4.61 inches in 1947.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Figure 4-28 Los Banos Weather Station Monthly Av erage Total Precipitation (Period of Record 1906-2016)
Source: WRCC, www.wrcc.dri.edu/
Figure 4-29 Los Banos Weather Station Daily Precipitation Average and Extreme (Period of Record 1906-2016)
Source: WRCC, www.wrcc.dri.edu/
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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The NCEI Storm Events Database records 23 heavy rain events in Merced County between 1998 and 2018.
Note no heavy rain events are recorded in the database after 2018. No casualties are recorded for any of the events. As noted above there is a connection between heavy rain events and flooding and is it assumed that the property damages listed in the NCEI database are the results of flooding caused by heavy rain events.
The following table show the records collected from the NCEI Strom Events Database for heavy rain.
Table 4-58 Heavy Rain Events in Merced County, 1998-2018 Location Date Property Damages ($) Crop Damages ($)
Merced 2/1/1998 $2,000,000 $1,400,000
Merced 5/1/1998 $0 $10,200,000
Merced 5/15/2000 $0 $100,000
Merced ARPT 12/13/2002 $0 $0
Merced 4/21/2003 $7,500 $0
Countywide 5/1/2003 $0 $2,000,000
Countywide 12/7/2004 $0 $0
Countywide 12/27/2004 $0 $0
Countywide 1/1/2005 $0 $0
Countywide 1/7/2005 $0 $0
Countywide 1/24/2005 $0 $0
Merced 2/15/2005 $0 $0
Merced ARPT 3/22/2005 $0 $0
Dos Palos/Atwater 9/20/2005 $0 $0
Countywide 1/1/2006 $0 $0
Countywide 3/2/2006 $0 $0
Livingston 3/28/2006 $0 $0
Countywide 4/2/2006 $0 $1,960,000
Merced 2/23/2010 $0 $0
Gustine 12/11/2014 $0 $0
Atwater Muni ARPT 4/27/2016 $0 $0
Santa Nella, Los Banos,
Brito 5/5/2016 $0 $0
Cregan 4/16/2018 $0 $0
Total $2,007,500 $15,660,000
Source: NCEI
Probability of Future Occurrences
Highly Likely – Based on the NCEI data, 23 heavy rain incidents over a 20-year period equates to a major event every 1.2 years and an 87 percent chance of a major heavy rain event in any given year.
Climate Change Considerations
As average temperatures increase over time, this generally will result in higher extreme temperatures and more warming in the atmosphere can trigger climate changes, which could result in more frequent extreme weather events. Pacific Northwest National Laboratory researchers have also found that atmospheric rivers will reach the West Coast more frequently (Gao 2015). Currently, the west receives rain or snow from these atmospheric rivers between 25 and 40 days each year. By the end of this century, days on which the atmospheric rivers reach the coast could increase by a third, or between 35 and 55 days a year.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Vulnerability Assessment
General Property
The Merced County planning area experiences a rainy season in the winter months through early spring.
These winter storms can include significant precipitation. The primary effect of these storms has not resulted in significant injury or damages to people and property, or the losses are typically covered by insurance. It is the secondary hazards caused by weather, such as floods, that have had the greatest impact on the County. Damage and disaster declarations related to adverse weather have occurred and will continue to occur in the future. Heavy rain and thunderstorms are the most frequent type of severe weather occurrences in the County. Utility outages, downing of trees, debris blocking streets and damage to property can be a direct result of these storm events. Given the nature of these types of storms, the entire County is potentially at risk.
People
Exposure is the greatest danger to people from heavy rain events. People can be caught in rising waters and need to be rescued.
Critical Facilities
Because of the unpredictability of heavy rain events, most critical facilities and infrastructure that is above ground is equally exposed to the storm’s impacts. Due to the random nature of this hazards, a more specific risk assessment was not conducted for this plan.
Economy
Economic impact of a heavy rain event is typically short-term. Generally, long-term economic impacts center more around hazards that cascade from a heavy rain even such as flooding.
In general, all severe weather poses a risk to agriculture economy in the county. Table 4-58 below describes the crops losses related to heavy rain events and associated indemnity amounts or loss payments from the USDA, RMA in the past 13 years. Merced County experiences an estimated $249,076 annualized loss due to crop damages from heavy rain events.
Table 4-59 Crops Loss Due to Heavy Rain, Risk Management Agency Crop Indemnity Reports, 2007-2020
Year Net
Determined
Acres
Indemnity
Amount
2007 354.18 $189,228
2009 1,639.58 $1,464,029
2010 4,173.48 $2,055,617
2011 584 $280,280
2012 1,475.48 $359,758
2013 354.6 $106,905
2014 3,545 $1,916,895
2015 3,303.7 $2,974,961
2016 1,742.3 $2,473,741
2017 4,920.1 $3,936,051
2018 766.47 $682,953
2019 6,741.8 $4,983,748
2020 781.8 $743,567
Total 30,382.49 $22,167,733
Source: USDA RMA
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Historic, Cultural and Natural Resources
As a natural process, the impacts of most heavy rain events by themselves are part of the overall natural cycle and do not cause long-term consequential damage.
Future Development
New critical facilities, such as communication towers should be built to withstand heavy rain damage.
Future development projects should consider adverse weather hazards at the planning, engineering and architectural design stage with the goal of reducing vulnerability. Stormwater master planning and site review should account for buildings to withstand heavy rain events considered for all new development.
Thus, development trends in the County are not expected to increase overall vulnerability to the hazard but all development will be affected by adverse weather and storm events and population growth will increase potential exposure.
Risk Summary
Ɣ During the 20-year period of 1998-2018 there were 23 heavy rain events in Merced County.
Ɣ Average annual precipitation ranges from 9.19 inches the southern portion of the County to 12.27 inches the northern portion.
Ɣ The County experiences an estimated $249,076 annualized crop loss due to heavy rain events.
Ɣ Related Hazards: Flooding, Landslide
Table 4-60 Hazard Risk Summary – Heavy Rain
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Highly Likely Critical High
City of Atwater Extensive Highly Likely Critical High
City of Dos Palos Extensive Highly Likely Critical High City of Gustine Extensive Highly Likely Critical High
City of Livingston Extensive Highly Likely Critical High City of Los Banos Extensive Highly Likely Limited Medium City of Merced Extensive Highly Likely Limited Medium DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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4.2.10Severe Weather: High Wind/Tornado
Hazard/ Problem Description
High winds, often accompanying severe thunderstorms, can cause significant property and crop damage, threaten public safety, and have adverse economic impacts from business closures and power loss.
Windstorms in Merced County are typically straight-line winds. Straight-line winds are generally any thunderstorm wind that is not associated with rotation (i.e., is not a tornado). It is these winds, which can exceed 100 mph that represent the most common type of severe weather and are responsible for most wind damage related to thunderstorms. These winds can overturn mobile homes, tear roofs off houses, topple trees, snap power lines, shatter windows, and sandblast paint from cars. Other associated hazards include utility outages, arcing power lines, debris blocking streets, dust storms, and an occasional structure fire.
Tornadoes are another severe weather hazard that can affect the Merced County planning area.
Tornadoes form when cool, dry air sits on top of warm, moist air. Tornadoes are rotating columns of air marked by a funnel-shaped downward extension of a cumulonimbus cloud whirling at destructive speeds of up to 300 mph, usually accompanying a thunderstorm. Tornadoes are the most powerful storms that exist. They can have the same pressure differential that fuels 300-mile-wide hurricanes across a path only 300-yards wide or less.
Geographic Area
Wind and tornadoes have the potential to happen anywhere in the County. The resulting damage from wind and tornado events may be most severe in the downtown areas of incorporate communities where there are more large trees, infrastructure, and higher density development.
The National Renewable Energy Laboratory (NREL) collects data on wind resources in the United States to help determine the location of new wind energy sites. Figure 4-30 from the NREL Wind Prospector webviewer shows the average annual wind speed in Merced County at the height of 100 meters. The eastern and central portions of the County have average wind speeds between 4.50 meters/second and
5.50 meters/second. The wind speeds in the western portion of the County vary greater than the eastern portions. Average wind speeds in western Merced County range from less than 4.00 meters/second to
7.00 meter/second in northwest.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Figure 4-30 Merced County Average Annual Wind Speed at 100 meters
Source: NREL Wind Prospector
Extent (Magnitude/Severity)
High winds and tornadoes can cause damage to property and loss of life. While most tornado damage is caused by violent winds, most injuries and deaths result from flying debris. Property damage can include damage to buildings, fallen trees and power lines, broken gas lines, broken sewer and water mains, and the outbreak of fires. Agricultural crops and industries may also be damaged or destroyed. Access roads and streets may be blocked by debris, delaying necessary emergency response.
In 2007, the NWS began rating tornadoes using the Enhanced Fujita Scale (EF-scale). The EF-scale is a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of eight levels of damage to the 28 indicators listed in Table 4-60.
These estimates vary with height and exposure. Standard measurements are taken by weather stations in open exposures.
Table 4-60 describes the EF-scale ratings versus the previous Fujita Scale used prior to 2007 (NOAA 2007).
Table 4-61 The Fujita Scale and Enhanced Fujita Scale
Fujita Scale Derived Operational EF-Scale
F Number
Fastest ¼
mile (mph)
3-second
gust (mph) EF Number
3-second
gust (mph) EF Number
3-second gusts
(mph)
0 40-72 45-78 0 65-85 0 65-85
1 73-112 79-117 1 86-109 1 86-110
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Fujita Scale Derived Operational EF-Scale
F Number
Fastest ¼
mile (mph)
3-second
gust (mph) EF Number
3-second
gust (mph) EF Number
3-second gusts
(mph)
2 113-157 118-161 2 110-137 2 111-135
3 158-207 162-209 3 138-167 3 136-165
4 208-260 210-261 4 168-199 4 166-200
5 261-318 262-317 5 200-234 5 Over 200
Source: NWS. Notes: EF - Enhanced Fujita F – Fujita mph - Miles per Hour Figure 4-31 illustrates the potential impact and damage from a tornado.
Figure 4-31 Potential Impact and Damage from a Tornado
Source: NOAA NWS, Storm Prediction Center
The damaging effects of wind speed are measured using the Beaufort Wind Scale as shown in Table 4-61 below. This scale only reflects land-based effects and does not take into consideration the effects of wind over water.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-62 Beaufort Wind Scale
Wind Speed
(mph) Description – Visible Condition
0 Calm; smoke rises vertically
1-4 Light air; direction of wind shown by smoke but not by wind vanes 4-7 Light breeze; wind felt on face; leaves rustle; ordinary wind vane moved by wind 8-12 Gentle breeze; leaves and small twigs in constant motion; wind extends light flag 13-18 Moderate breeze; raises dust and loose paper; small branches are moved 19-24 Fresh breeze; small trees in leaf begin to sway; crested wavelets form on inland water 25-31 Strong breeze; large branches in motion; telephone wires whistle; umbrellas used with difficulty 32-38 Moderate gale whole trees in motion; inconvenience in walking against wind 39-46 Fresh gale breaks twigs off trees; generally, impedes progress 47-54 Strong gale slight structural damage occurs; chimney pots and slates removed 55-63 Whole gale trees uprooted; considerable structural damage occurs 64-72 Storm very rarely experienced; accompanied by widespread damage 73+ Hurricane devastation occurs
Source: NWS
Based on NCEI records between 1955 and 2019 there have been a combined 36 strong wind/high wind/thunderstorm winds and 32 tornado/funnel cloud events in Merced County which has resulted in a total of $1,925,800 in property damage. The most damaging event took place on January 20, 2010 and was a 59-mph wind event that resulted in $750,000 in property damages. Overall, high wind event impacts would likely be limited, with a majority of impacts being related to property damages caused my downed trees as well as power outages.
In the past 65 years all the tornado events that have taken place in Merced County have been between F0-F1 or EF0 tornadoes. However, it should be noted that, although unlikely, larger tornadoes could occur.
Should the County be hit by an EF-3 or higher tornado, it can be extrapolated that because of its relative size and the potential size and length of a tornado’s path a significant portion of the County could be impacted, resulting in property and crop damage and loss of life.
Tornado impacts to the County would likely be negligible, with less than 10 percent of the planning area affected by events in the EF0-2 range, though stronger tornadoes are possible. The impact to quality of life or critical facilities and functions in the affected area would depend on where the tornado occurred.
Injuries or deaths are possible due to wind thrown trees or property damage caused by wind events.
Overall, impacts from high wind and tornado events would likely be negligible, with less than 10 percent of property severely damaged and shutdown of facilities due to loss of power for 24 hours or less.
Past Occurrences
During the rainy season, the Merced planning area is prone to relatively strong thunderstorms, sometimes accompanied by high winds and tornadoes. While tornadoes do occur occasionally, most often they are of F0/EF0 intensity. The NCEI Storm Events Database does not record any F2, or F3 or anything events greater than EF0 events that have occurred in the planning area in the past. Table 4-62 Past High Wind and Tornado Events contains incident descriptions for significant historic events. In addition to the events listed in the NCEI database, there was a USDA disaster designation declared for Merced County in 2016 for “severe weather including excessive rainfall and high winds” (refer to Table 4-4).
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-63 Past High Wind and Tornado Events in Merced County, 1955-2019 Hazard Type Date Location Magnitude
Property
Damages
($)
Crop
Damages
($)
Deaths Injuries
Tornado 4/18/1955 Merced County Unknown $0 $0 0 0
Thunderstorm
Wind 7/6/1957 Merced County 70mph $0 $0 0 0
Tornado 4/22/1967 Merced County F1 $0 $0 0 0
Tornado 4/5/1975 Merced County F0 $25,000 $0 0 0
Tornado 3/4/1978 Merced County F1 $250,000 $0 0 1
Tornado 2/19/1986 Merced County F0 $25,000 $0 0 0
Tornado 3/26/1991 Merced County F0 $0 $0 0 0
Thunderstorm
Wind 6/15/1995 Merced/Dos Palos Unknown $50,000 $3,000,000 0 0 Thunderstorm
Wind 4/1/1996 Los Banos/Gustine 80mph $320,000 $100,000 0 0 Tornado 4/1/1996 Merced F0 $10,000 $0 0 0
Tornado 11/22/1996 Merced F1 $45,000 $0 0 0
Tornado 11/13/1997 Los Banos F0 $5,000 $0 0 0
Tornado 2/14/1998 Los Banos F0 $0 $0 0 0
Funnel Cloud 3/25/1998 Atwater/Livingston/
Merced Unknown $0 $0 0 0
Funnel Cloud 3/28/1998 Plainsburg Unknown $0 $0 0 0
Funnel Cloud 4/5/1998 Dos Palos/Los
Banos Unknown $0 $0 0 0
Funnel Cloud 1/31/1999 Merced Unknown $0 $0 0 0
High Wind 1/10/2001 Countywide Unknown $20,000 $0 0 4
High Wind 5/2/2001 Countywide 57mph $75,000 $1,960,000 0 0 High Wind 8/29/2001 Santa Nella Unknown $0 $0 0 0
High Wind 11/24/2001 Countywide Unknown $0 $0 0 0
High Wind 12/2/2001 Countywide Unknown $0 $0 0 0
High Wind 3/13/2002 Countywide Unknown $0 $0 0 0
High Wind 6/8/2002 Countywide Unknown $0 $0 0 0
High Wind 6/9/2002 Countrywide Unknown $0 $0 0 0
High Wind 8/3/2002 Los Banos Muni
ARPT Unknown $0 $0 0 0
Strong Wind 12/14/2002 Countywide 49mph $0 $0 0 0
Strong Wind 12/16/2002 Countywide 36mph $5,000 $0 0 0
Tornado 12/16/2002 Merced ARPT F1 $400,00 $0 0 0
Strong Wind 12/19/2002 Countywide 46mph $5,000 $0 0 0
Strong Wind 12/28/2002 Countywide 34mph $4,000 $0 0 0
Funnel Cloud 5/3/2003 Atwater/Merced/
Livingston Unknown $0 $0 0 0
Strong Wind 2/25/2004 Countywide Unknown $0 $0 0 0
Funnel Cloud 10/17/2004 Countywide 40mph $0 $0 0 0
Strong Wind 10/19/2004 Countywide 41 $1,000 $0 0 0
Strong Wind 1/7/2005 Countywide 36 mph $10,000 $0 0 0
High Wind 1/7/2005 Countywide 57.4 mph $150,000 $150,000 0 0 Funnel Cloud 3/20/2005 Los Banos Unknown $0 $0 0 0
Strong Wind 3/22/2005 Countywide 40 mph $5,000 $0 0 0
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-120
Hazard Type Date Location Magnitude
Property
Damages
($)
Crop
Damages
($)
Deaths Injuries
Tornado 4/8/2005 Ballico F0 $25,000 $50,000 0 0
Funnel Cloud 4/8/2005 Gustine Unknown $0 $0 0 0
Funnel Cloud 1/18/2006 Gustine/El Nido Unknown $0 $0 0 0 Funnel Cloud 3/28/2006 Merced Unknown $0 $0 0 0
Tornado 3/28/2006 Atwater/Merced/
Merced ARPT F0 $25,000 $0 0 0
Funnel Cloud 4/14/2006 Atwater Unknown $0 $0 0 0
Strong Wind 9/8/2006 Countywide 40 mph $1,000 $0 0 0
Thunderstorm
Wind 10/29/2007 Cregan 55 mph $60,000 $0 0 0
Strong Wind 2/23/2008 Countywide 39 mph $0 $12,000 0 0 Strong Wind 5/31/2008 Countywide 30 mph $500 $0 0 0
Strong Wind 6/10/2008 Countywide 39 mph $200 $1,000 0 0 Strong Wind 6/26/2008 Countywide 33 mph $1,000 $0 0 0
Funnel Cloud 1/25/2009 Stevinson Unknown $0 $0 0 0
Tornado 2/9/2009 Merced ARPT EF0 $0 $0 0 0
High Wind 1/20/2010 Countywide 59 mph $750,000 $0 0 0
Strong Wind 3/6/2012 Countywide 36 mph $35,000 $0 0 0
Funnel Cloud 4/12/2012 Atwater Unknown $0 $0 0 0
Funnel Cloud 3/2/2014 Dos Palos Unknown $0 $0 0 0
Strong Wind 12/11/2014 Countywide 48 mph $0 $500,000 0 0 Strong Wind 3/5/2016 Countywide 35mph $100 $0 0 0
Strong Wind 2/1/2017 Countywide 30 mph $1,000 $0 0 0
Funnel Cloud 3/21/2017 Castle AFB Unknown $0 $0 0 0
High Wind 12/16/2017 Countywide 51 mph $0 $0 0 0
Strong Wind 1/6/2019 Countywide 43 mph $16,000 $0 0 0
Strong Wind 1/17/2019 Countywide 30 mph $1,000 $0 0 0
Funnel Cloud 3/27/2019 Livingston Unknown $0 $0 0 0
Strong Wind 4/9/2019 Countywide 39 mph $5,000 $0 0 0
Funnel Cloud 5/21/2019 Los Banos Unknown $0 $0 0 0
Funnel Cloud 11/28/2019 El Nido Unknown $0 $0 0 0
Total $1,925,800 $5,773,000 0 5
Source: NCEI Storm Events Database, Notes: mph – Miles per Hour, ARPT – Airport, AFB – Airforce Base Figure 4-32 and Figure 4-33 show the location of the past wind and tornado events in Merced County based on data from NOAA’s NWS Storm Prediction Center.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-121
Figure 4-32 Merced County Wind Events (1950 -2019)
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-122
Figure 4-33 Tornado Events in Merced County, 1950 -2019
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-123
Probability of Future Occurrences
Highly Likely – Sixty-eight high wind and tornado events have occurred in Merced County over 64 years of record keeping, which equates to one high wind or tornado event every 1.1 years, on average, and a 94 percent chance of a high wind or tornado event occurring in any given year. Historical wind activity within the planning area indicates that the area will likely continue to experience high wind during thunderstorm events with a potential of the formation of funnel clouds and low intensity tornadoes during adverse weather conditions. The actual risk to the County is dependent on the nature and location of any given thunderstorm or tornado event.
Climate Change Considerations
There presently is not enough data or research to quantify the magnitude of change that climate change may have related to tornado frequency and intensity. NASA’s Earth Observatory has conducted studies that aim to understand the interaction between climate change and tornadoes. Based on these studies meteorologists are unsure why some thunderstorms generate tornadoes and others don’t, beyond knowing that they require a certain type of wind shear. Tornadoes spawn from approximately one percent of thunderstorms, usually supercell thunderstorms that are in a wind shear environment that promotes rotation. Some studies show a potential for a decrease in wind shear in mid-latitude areas. Because of uncertainty with the influence of climate change on tornadoes, future updates to the mitigation plan should include the latest research on how the tornado hazard frequency and severity could change. The level of significance of this hazard should be revisited over time.
As for wind, studies referenced in California’s Fourth Climate Assessment indicated that extreme fire weather, particularly in the form of hot and dry winds, can strongly influence shrub-land fire regimes.
Strong winds have also been now associated with severe forest fires in California meaning climate change impacts on wind patterns may also affect forest health and wildfire susceptibility. Lastly, other ongoing research compiled in the recent climate assessment has resulted in different conclusions on the effect of climate change on wind regimes, particularly extreme wind events, such as the Santa Ana and Diablo winds that created some of the most devastating wildfires (California Natural Resources Agency 2018a). At this time, these changing factors are not well understood and are still being incorporated into state and regional research and risk analysis.
Vulnerability Assessment
General Property
General damages are both direct (what the wind event physically destroys) and indirect, which focuses on additional costs, damages and losses attributed to secondary hazards spawned by the event, or due to the damages caused by the wind event. Depending on the magnitude of the wind events as well as the size of the tornado and its path, a tornado is capable of damaging and eventually destroying almost anything.
Construction practices and building codes can help maximize the resistance of the structures to damage.
Secondary impacts of damage caused by wind events often result from damage to infrastructure. Downed power and communications transmission lines, coupled with disruptions to transportation infrastructure, create difficulties in reporting and responding to emergencies. These indirect impacts of a wind event put tremendous strain on a community. In the immediate aftermath, the focus is on emergency services.
Downed trees caused by a wind event are a common occurrence in the County. Falling trees can cause significant damage to property and put people at risk. Due to multiple years of drought in the County, many trees in the area have been impacted making them more susceptible to blow-down during wind events.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-124
People
Community members are the most vulnerable to high wind and tornado events. The availability of sheltered locations such as basements, buildings constructed using tornado-resistant materials and methods, and public storm shelters, all reduce the exposure of the population. However, there are also segments of the population that are especially exposed to the indirect impacts of high winds and tornadoes, particularly the loss of electrical power. According to the data obtained from emPower.com, a website maintained by the U.S. Department of Health and Human Services, 4%, or 1,412 of the 36,689 of the Medicare beneficiaries in the County rely on medical equipment that is dependent on electricity in order to live independently. These populations include the elderly or disabled, especially those with medical needs and treatments dependent on electricity. Nursing homes, community-based residential facilities, special needs housing facilities, and isolated communities are also vulnerable because of life support needs if electrical outages are prolonged, since backup power generally operates only minimal functions for a short period of time.
Following the unprecedented 2018 wildfire season in California, PG&E announced it will be conducting PSPS when there are high winds and dry conditions and generally a heightened fire risk forecasted. The outages could last several days, and PG&E has suggested customers be prepared for outages that could last longer than 48 hours. A majority of Merced County could be affected by the power outages.
Critical Facilities
Both winds and tornadoes may impact exposed critical infrastructure such as power lines; depending on the impact and the function, this could cause a short-term economic disruption. The most common problems associated with tornadoes and high winds are loss of utilities. Downed power lines can cause power outages, leaving large parts of the county isolated, and without electricity, water, and communication. Damage may also limit timely emergency response and the number of evacuation routes.
Downed electrical lines following a storm can also increase the potential for lethal electrical shock.
Damaging winds can also cause wildfires; refer to the Wildfire section for more information on the County’s vulnerability to wildfires.
In an effort to mitigate the impacts of PSPS, the State of California has allocated PSPS Resiliency funds for counties, cities, tribes and state agencies to “procure fixed, long-term emergency electrical generation equipment, develop continuity plans, risk assessments for critical infrastructure, post event reports, and public education material or supplies to prepare of electric disruption” (Cal OES 2021). In fiscal year 2019- 20 Merced County was allocated $422,987 from the PSPS Resiliency Allocation to counties, to purchase and install generators at County fire stations, backup generators and lighting infrastructure for the Merced County Operations Areas and purchase a battery-powered backup Public Safety Answering Point for all dispatch centers within the Merced County Operational Area.
Economy
Winds typically don’t have long-term impacts on the economy, although wind does have an impact on the agriculture economy in the county. As shown in Table 4-63, wind events have been a leading cause of crop loss in the past three years (2007 – 2019), resulting in over $2 million in loss payments from the USDA and more than 3,000 acres lost to high wind events. Merced County experiences an estimated $187,255 annualized loss due to crop damages from excessive wind events.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-125
Table 4-64 Crops Loss Due to High Wind, Risk Management Agency Crop Indemnity Reports, 2007-2019
Year Net
Determined
Acres
Indemnity
Amount
2007 372.4 $97,945
2008 327.02 $130,399
2012 32.4 $2,159
2013 1,624.8 $1,267,860
2014 176 $171,649
2015 301.9 $75,625
2016 7.4 $11,792
2017 398.68 $303,600
2019 298 $186,034
Total 3,539 $2,247,063
Source: USDA RMA
Historic, Cultural and Natural Resources
High winds and tornadoes can cause massive damage to the natural environment, uprooting trees and other debris. This is part of a natural process, however, and the environment will return to its original state in time.
Future Development
As the County continues increase in population, the number of people and housing developments exposed to the hazard increases. Adherence to current building codes, coupled with proper education on building techniques and the use of sturdy building materials, attached foundations, and other structural techniques may minimize the property vulnerabilities. Public shelters at parks and open spaces may help reduce the impacts of tornadoes and high wind events on the recreational populations exposed to storms.
Risk Summary
Ɣ Between 1955 and 2019 there were a combined 68 high wind (36) and tornado (32) events in the County.
Ɣ Wind and tornado events have resulted in $1,925,800 in property damages. The most damaging event took placed on January 20, 2010 with 59 mph wind causing $750,000 in property damages.
Ɣ Excessive wind has caused 3,539 acres to be lost and $2,247,063 crop loss payment made by the USDA to farmers in the County.
Ɣ PSPS pose a risk to individuals in the County who depend on electricity to live independently. Four percent of Medicare Beneficiaries in the County are electricity dependent.
Ɣ Related Hazards: Extreme heat, Heavy Rain, Agriculture/Pest and Crop Disease, Wildfire
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-126
Table 4-65 Hazard Risk Summary – High Wind/Tornado
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Highly Likely Critical High
City of Atwater Extensive Highly Likely Critical High
City of Dos Palos Extensive Highly Likely Critical High City of Gustine Extensive Highly Likely Limited Medium City of Livingston Extensive Highly Likely Limited Medium City of Los Banos Extensive Highly Likely Limited Medium City of Merced Extensive Highly Likely Limited Medium
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-127
4.2.11Subsidence
Hazard/Problem Description
Land subsidence is defined as the vertical sinking of the land over natural or manmade underground voids. Subsidence is common in several areas of California, usually as a result of groundwater pumping, peat loss, or oil and gas extraction. Fluctuations in the level of underground water caused by pumping or by injecting fluids into the earth can initiate sinking to fill the empty space previously occupied by water or soluble minerals. Weight, including surface developments such as roads, reservoirs, and buildings, and manmade vibrations from such activities as blasting and heavy truck or train traffic can accelerate the natural processes of subsidence, or induce subsidence over manmade voids.
The 2018 California SHMP profiles subsidence as a secondary impact of drought. Through reduced availability of surface water, groundwater pumping in order to meet water needs. According to a study published by Yale Environmental Review, approximately 1 million people in the San Joaquin Valley rely on groundwater pumping for drinking water, and thousands of farmers rely on groundwater to irrigate crops.
While groundwater pumping occurs in both drought and non-drought years to support urban, rural, and agricultural water needs, the 2018 California State HMP notes that it is greatly increased during dry years.
Land subsidence due to groundwater pumping can permanently damage or collapse underground aquifers, increase flood risk in low-lying areas, and pose hazards to buildings, infrastructure, and water storage facilities.
Subsidence can result in serious, localized structural damage to buildings, roads, irrigation ditches, canals, streams, underground utilities, and pipelines. It can disrupt and alter the flow of surface or underground water. The consequences of improper use of land subject to ground subsidence can be excessive economic losses, including the high costs of repair and maintenance for buildings, irrigation works, highways, utilities, and other structures. This results in direct economic losses to citizens as well as indirect economic losses through increased taxes and decreased property values.
Geographic Area
Figure 4-34 below shows areas statewide that have a recent history of subsidence or are known to be at an increased risk of subsidence. Most studies and concern about land subsidence in California have focused on the Santa Clara Valley, San Joaquin Valley, Sacramento Valley, Antelope Valley, Coachella Valley, and Mojave River Basin Areas.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-128
Figure 4-34 Historic Land Subsidence in California
Source: California DWR, November 2014 Public Update for Drought Response The Merced Subbasin GSA has a focused map of subsidence in the vicinity of Merced County, shown in Figure 4-35 below. This agency was created for the purpose of forming a joint powers agency that will be the GSA for a portion of the Merced Groundwater Subbasin. The Merced Subbasin GSA developed and adopted the Merced Groundwater Sustainability Plan in December 2019. The implementation of plan will address the SGMA requirements and achieve the sustainability goals outlined in SGMA, in addition to positive impacts to future subsidence in the County.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-129
Figure 4-35 Merced County Area Subsidence
Source: Merced County
Extent (Magnitude/Severity)
A lack of data makes it difficult to predict the magnitude of future land subsidence incidents in Merced County. As shown in Figure 4-35 above, most of the documented land subsidence in the county has been of 0.5 feet or less per year. Much of this subsidence is continuous and occurs gradually over a vast area of the county. However, that can still be enough to cause structural issues. Sudden and localized subsidence events, such as sinkholes, can cause damage to building foundations, roadways, and utilities. Such events have been documented in nearby Fresno and Madera counties, where sinkholes or sudden subsidence has damaged and closed roads. Ongoing displacements of as much as 12” per year have been documented in other parts of the state. As areas of the county continue to gradually sink, the impacts on infrastructure may become more apparent.
Previous Occurrences
While actual effects of subsidence are visible throughout the County, research on the hazard produced thus far has not produced records of any specific events. Some areas of the County have subsided 10-15 feet over the past 50 years according to the HMPT.
Probability of Future Occurrences
Land subsidence has been a recurring issue in Merced County for decades and can be expected to continue in the future. The frequency of future land subsidence incidents in the county will largely be dependent on the mitigation actions and pumping regulations initiated by the state, the county, and local regulations. Based on past trends of gradual subsidence throughout the entire San Joaquin Valley and the
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-130
continued dependence on groundwater pumping, it can be assumed that subsidence will continue in the future, with increased rates of subsidence coinciding with drought years.
Climate Change Considerations
The most likely impact that climate change will have on land subsidence risk is the potential for extended and severe drought, which could likely result in more groundwater pumping and human-induced subsidence. During periods of drought, water levels may be drawn too low, which results in an irreversible compaction of aquifers. The water cannot recharge the layers, causing permanent subsidence and diminishment of groundwater storage capacity.
Vulnerability Assessment
General Property
The lack of detailed data on land subsidence in Merced County makes it difficult to quantify past or potential future losses. Most subsidence instances result in relatively minor damage and settling of buildings. But in some cases, subsidence can result in serious structural damage to buildings, roads, irrigation ditches, underground utilities, and pipelines, potentially resulting in the complete loss of the structure. Subsidence can also disrupt and alter the flow of surface or underground water, as well as reducing the future capacity of aquifers.
People
This hazard typically results in property damage, not risk to human life. In the event of a sudden sinkhole, it would be possible for people to sustain injuries if they were walking or driving and were caught in the sinkhole.
Critical Facilities and Infrastructure
Linear infrastructure (roads, buried pipelines) tends to have the most risk to land subsidence. Statewide, subsidence has caused damage to dams and levees, canals, roads and bridges, water and sewer lines, pipelines, well casings, and aircraft runways, in addition to a variety of buildings and other structures.
Highways 59 and 152 traverse areas of historic subsidence in the County. The threat to the California Aqueduct has been identified as a significant concern for the state. Evidence of the gradual impacts of subsidence on infrastructure in the San Joaquin Valley can be seen in Figure 4-36 below. This image was taken from the California Water Foundations Summary Report on Land Subsidence from Groundwater Use in California. The bridge shown is over the Outside Canal north of Mendota, California. While it is partially submerged in this image, the bridge used to have canal inspections by the Central California Irrigation District staff conducted from a boat passing under the bridge.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-131
Figure 4-36 Evidence of Gradual Land Subsidence, Partially Submerged Russell Avenue Bridge, Mendota, CA
Economy
Damage resulting from land subsidence can cause direct economic losses in the form of needed structural repairs to affected buildings and facilities. It can also result in indirect losses, such as from increased taxes and decreased property values. Subsidence may impact tourism and shipping industries if transportation routes are affected.
Historic, Cultural, and Natural Resources
Historic and cultural facilities are just as susceptible to subsidence related damage as other structures.
However, there is not sufficient data to identify specific historical or cultural facilities at increased risk from this hazard.
Groundwater pumping can cause significant impacts to underground water resources, and the resulting subsidence events may further disrupt and alter the flow of surface or underground water, in a cyclical pattern of environmental degradation. Furthermore, soil compaction resulting from subsidence can permanently reduce aquifer capacity, impacting water supplies long into the future.
Future Development
The areas of the county which have experience the greatest historic rates of subsidence are largely in the middle of the county, which is occupied by the Merced National Wildlife Refuge, San Luis National Wildlife Refuge, and Great Valley Grasslands State Park. As such, future development of these areas will be significantly restricted, and growth will be limited. While vulnerability to this hazard is not anticipated to increase with new development, increased water pumping resulting from the demand of new development has the potential to increase the frequency and severity of subsidence. This could be
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-132
especially important in Los Banos, given that area has higher subsidence potential. Increased efforts to monitor and manage groundwater pumping, increased accuracy of mapping, and emphasis on appropriate grading and ground compaction during development will help alleviate vulnerability for future development in unknown areas of risk.
Risk Summary
While a significant portion of Merced County is at risk from ongoing land subsidence, the gradual nature of this hazard makes the overall significance of this hazard low.
Ɣ The gradual nature of land subsidence incidents limits their overall impact, in terms of property damage, at the county level.
Ɣ The entire San Joaquin Valley is vulnerable to land subsidence, and Merced County is vulnerable due to its dependence on agriculture and groundwater pumping.
Ɣ There is a shortage of data on specific occurrence of this hazard in Merced County. Most studies on land subsidence in California have focused on the Santa Clara Valley, San Joaquin Valley, Sacramento Valley, Antelope Valley, Coachella Valley, and Mojave River Basin Areas, however there is not extensive information on individual subsidence events.
Ɣ Increased drought conditions resulting from climate change has the potential to result in more groundwater pumping, which could lead to more human-induced subsidence; groundwater sustainability planning and management could help offset future subsidence.
Ɣ Land subsidence can alter the flow of surface or underground water, an impact that may not be noticed until long after the fact.
Ɣ Related Hazards: Drought
Table 4-66 Hazard Risk Summary – Subsidence
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Likely Negligible Low
City of Atwater Limited Occasional Negligible Low
City of Dos Palos Limited Occasional Negligible Low
City of Gustine Limited Unlikely Negligible Low
City of Livingston Limited Occasional Negligible Low
City of Los Banos Limited Likely Negligible Low
City of Merced Limited Occasional Negligible Low
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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4.2.12Wildfire
Hazard/Problem Description
A wildfire is an uncontrolled fire spreading through vegetative fuels, posing danger and destruction to property and watersheds. While wildfires are often the direct result of lightning strikes, they can be caused by downed powerlines or mechanical equipment or are the result of human activities like landscape debris burns, carelessness, or arson. Wildfires often start in undeveloped areas and public land areas, such as state and federal lands, but can spread to urban areas where structures and other human development are more concentrated. The predominant dangers from wildfires are:
Ɣ Injury or loss of life to people in the affected area; and Ɣ The destruction of vegetation, property, wildlife.
Communities throughout California are increasingly concerned about wildfire safety as increased development in the foothills and mountain areas and subsequent fire control practices have affected the natural cycle of the ecosystem. Wildfire risk is predominantly associated with wildland-urban interface areas, a general term that applies to development adjacent to landscapes that support wildfire. However, significant wildfires can also occur in heavily populated areas.
Merced County is exposed to a variety of wildfire hazard conditions that varies based on fuels, topography, weather, and human behavior. CAL FIRE, as required by government code 51181, has undertaken a statewide program to map areas of potential wildfire severity, and to describe the potential for wildfires to occur in a given area; the resulting Fire Hazard Severity Zones are shown in Figure 4-37 below.
It should be noted that fires are also an important natural component of Merced County’s ecosystem.
Wildlands need to burn periodically to naturally maintain viable environments. Fuel maintenance (controlled burns, mowing, cattle grazing, and other means) is a necessary replacement to uncontrolled wildland fires because of threats to human habitation. Development patterns in rural lands can reduce the ability to manage fuel and defend “values at risk”.
Generally, there are three major factors that sustain wildfires and predict a given area’s potential to burn.
These factors are fuel, topography, and weather.
Ɣ Fuel—Fuel is the material that feeds a fire and is a key factor in wildfire behavior. Fuel is generally classified by type and by volume. Fuel sources are diverse and include everything from dead tree leaves, twigs, and branches to dead standing trees, live trees, brush, and cured grasses. Also, to be considered as a fuel source are manmade structures, such as homes and other associated combustibles. The type of prevalent fuel directly influences the behavior of wildfire. Fuel is the only factor that can be modified by humans. The main fuel types in Merced County are crops and grasses, while there are also brush and pine fuels present in some areas in the southwest of the county.
Ɣ Topography—An area’s terrain and slopes affect its susceptibility to wildfire spread. Both fire intensity and rate of spread increase as slope increases due to the tendency of heat from a fire to rise via convection. The arrangement and types of vegetation throughout a hillside can also contribute to increased fire activity on slopes.
Ɣ Weather—Weather components such as temperature, relative humidity, wind, and lightning also affect the potential for wildfire. High temperatures and low relative humidity dry out fuels that feed wildfires, creating a situation where fuel will more readily ignite and burn more intensely. Thus, during periods of drought, the threat of wildfire increases. Wind is the most influential weather factor of the three and its influence can increase rates of spread regardless of temperature and relative humidity.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Geographic Area
Both urban and wildland fires conditions exist in Merced County which increases the chances for damage to property, loss of life and/or injury. In the wildland-urban interface, where development has expanded into rural, higher risk areas, fires can result in major losses of property and structures. In most of Merced County, the California Department of Forestry and Fire Protection (CAL FIRE) ranks fuel loading as low.
Fuels are mainly crops and grasses. In the southwest corner, there are some brush, pine, and grass fuels, which are ranked as moderate fuel hazards, primarily in the area west of Interstate 5.
Generally, fire season in Merced County extends from early spring to late fall. Onset can happen suddenly due to lightning or human caused factors and wildfires can last from a few hours to a few months, but the likely hood of a large and damaging fire lasting for months in Merced County is not likely. Secondary effects from wildfire include increased erosion, destabilized slopes, degraded air and water quality, and economic impacts from burned landscapes. Urban fires primarily involve the uncontrolled burning of residential, commercial and/or industrial structures generally caused by human activities.
The California Department of Forestry and Fire Protection’s Fire and Resource Assessment Program (FRAP) assesses the amount and extent of California’s forests and rangelands, analyzes their conditions and identifies alternative management and policy guidelines.
CAL FIRE identifies areas that are at high risk of damage from wildfire based primarily on three factors:
Ɣ Ranking Fuel Hazards = ranking vegetation types by their potential fire behavior during a wildfire.
Ɣ Assessing the Probability of Fire = the annual likelihood that a large damaging wildfire would occur in a particular vegetation type.
Ɣ Defining Areas of Suitable Housing Density that Would Create Wildland-Urban Interface Fire Protection Strategy Situations = areas of intermingled wildland fuels and urban environments that are in the vicinity of fire threats.
Population density and the presence of structures are not currently used to determine the fire hazard severity for a particular region, although they do have a significant impact on fire behavior.
Based on the above criteria, CAL FIRE maps Fire Hazard Severity Zones for each county as “Very High,” “High,” or “Moderate”. As shown below in Figure 4-37, there are no areas in Merced County classified as Very High and the areas ranked High are primarily located west of Interstate 5. These areas exhibit the combination of vegetative fuel and topography that contribute to an increased fire hazard potential. The fact that an area is in a Moderate Hazard designation does not mean it cannot experience a damaging fire. It only means that the probability is reduced, generally because the number of days a year that the area has “fire weather” is less.
The Fire Hazard Severity Zones (FHSZ) spatial dataset was explicitly developed for adopting new ignition- resistant building code standards and adopted by the California Building Commission in 2007. It is constructed to describe the nature and probability of fire exposure to structures, including those lands that are highly urbanized, but in close proximity to open wildlands. It is broken into Federal Responsibility Areas, State Responsibility Areas, and Local Responsibility Areas shown below. DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-135
Figure 4-37 Merced County Federal, Stat e, and Local Responsibility Severity Zones
CAL FIRE has also designated the following Merced County communities as being at increased risk from wildfires (https://osfm.fire.ca.gov/divisions/wildfire-planning-engineering/fire-plan/communities-at risk/):
Ɣ Dos Palos
Ɣ Gustine
Ɣ Los Banos
Ɣ South Dos Palos
Some unincorporated communities located within the county are not confronted with a high wildfire risk, due primarily to the dominant type of vegetation in those areas. The low-growing native grasses and shrubs found in these communities present a minimal vegetative fuel source and a corresponding low wildfire risk. In addition, the topography of those areas is mainly level and well developed in both residential and agricultural land uses.
Extent (Magnitude/Severity)
Vegetation (or fuel) plays a major role in fire behavior and shaping fire hazard potential. Vegetation distribution throughout the county varies by location and topography, with dramatic differences observed between the western, central, and eastern portions of the county. For instance, fire behavior in brush fuel
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-136
types produces higher flame lengths than that in grassland, although spread rates are typically slower. Fire behavior in forests is variable, depending on surface fuel conditions and the presence of ladder fuels.
Fuel loading in developed areas susceptible to wildfire becomes even more complex. The introduction of some ornamental plantings as landscaping and groundcover can dramatically increase the fire loading of a neighborhood. Gazebos, fencing, patios, decks and even the structures themselves add even more fuel.
Once structures become involved in fire, the problem compounds as embers cast out thousands of feet onto combustible roofs well removed from the wildland area.
Steep terrain also plays a key role in the rate at which wildfires spread, as fires will normally burn much faster uphill. Generally, when the gradient of a slope doubles, the rate of spread of a fire will also double.
Steep topography also channels air flow, thereby creating erratic wind patterns. Fire suppression in steep areas is also complicated by limited accessibility, and the effectiveness of firefighters and equipment are hampered by lack of access roads.
Another factor that can increase the severity of wildfires in the county is areas with high percentages of dead trees, as discussed in subsection 4.3.15 Agricultural Pests and Disease.
The Fire Rating System defined in Table 4-66 describes the characteristics and potential intensity of fires, including the effect on the ability to manage and suppress fires. Fire conditions up through Class 5 are possible in Merced County, primarily in the unincorporated areas in the far east and west of the county.
Table 4-67 Fire Danger Rating System
Rating Basic Description Detailed Description
CLASS 1: Low Danger (L)
COLOR CODE: Green
fires not easily
started
Fuels do not ignite readily from small firebrands. Fires in open or cured grassland may burn freely a few hours after rain, but wood fires spread slowly by creeping or
smoldering and burn in irregular fingers. There is little danger of spotting.
CLASS 2: Moderate Danger
(M) COLOR CODE: Blue
fires start easily and
spread at a
moderate rate
Fires can start from most accidental causes. Fires in open cured grassland will burn briskly and spread rapidly on windy days. Woods fires spread slowly to moderately fast.
The average fire is of moderate intensity, although heavy concentrations of fuel – especially draped fuel -- may burn hot. Short-distance spotting may occur but is not
persistent. Fires are not likely to become serious and
control is relatively easy.
CLASS 3: High Danger (H)
COLOR CODE: Yellow
fires start easily and
spread at a rapid
rate
All fine dead fuels ignite readily, and fires start easily from most causes. Unattended brush and campfires are likely to escape. Fires spread rapidly, and short-distance spotting is common. High-intensity burning may develop on slopes
or in concentrations of fine fuel. Fires may become serious and their control difficult, unless they are hit hard and fast while small.
CLASS 4: Very High Danger
(VH) COLOR CODE: Orange
fires start very easily
and spread at a very
fast rate
Fires start easily from all causes and immediately after ignition, spread rapidly and increase quickly in intensity.
Spot fires are a constant danger. Fires burning in light fuels may quickly develop high-intensity characteristics - such as long-distance spotting - and fire whirlwinds, when they burn into heavier fuels. Direct attack at the head of such fires is rarely possible after they have been burning more than a few minutes.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Rating Basic Description Detailed Description
CLASS 5: Extreme (E) COLOR
CODE: Red
fire situation is
explosive and can
result in extensive
property damage
Fires under extreme conditions start quickly, spread
furiously and burn intensely. All fires are potentially serious. Development into high-intensity burning will
usually be faster and occur from smaller fires than in the Very High Danger class (4). Direct attack is rarely possible and may be dangerous, except immediately after ignition.
Fires that develop headway in heavy slash or in conifer stands may be unmanageable while the extreme burning
condition lasts. Under these conditions, the only effective and safe control action is on the flanks, until the weather changes or the fuel supply lessens.
Source: http://www.wfas.net
Major wildland fires can completely destroy ground cover. If heavy rains follow a major fire, flash floods, heavy erosion, land subsidence and mudflows can occur. After a wildland fire passes through an area, the land is laid bare of its protective vegetation cover and is susceptible to excessive runoff and erosion from winter storms. The intense heat from the fire can also cause a chemical reaction in the soil that makes it less porous, and the fire can destroy the root systems of shrubs and grasses that aid in stabilizing slope material. These cascading effects can have ruinous impacts on people, structures, infrastructure, and agriculture.
Fire threat provides a measure of fuel conditions and fire potential in the ecosystem, representing the relative likelihood of “damaging” or difficult to control wildfire occurring for a given area. Fire Threat is not a risk assessment by itself but can be used to assess the potential for impacts on various assets and values susceptible to fire. Impacts are more likely to occur and/or be of increased severity for the higher threat classes. Fire threat is a combination of two factors: 1) fire probability, or the likelihood of a given area burning, and 2) potential fire behavior (hazard). These two factors are combined to create five threat classes ranging from low to extreme. Figure 4-38 below shows the wildfire threat areas throughout Merced County.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-138
Figure 4-38 Merced County Wildfire Threat Areas
Previous Occurrences
There have not been any state or federal disaster declarations in Merced County related to wildfire in the past. The Planning Team noted that although there are many fire starts, the fuels are “flashy” and fires are usually quickly put out. Despite this, there have been 101 wildfires recorded in the county from 1950-2018 totaling 110,893 acres burned. This is an average of over 1,500 acres burned every year. In 2020, a portion of the SCU Lightning Complex Fire, which is the 3rd largest fire by acres burned in state history, extended into Merced County, burning approximately 3,800 acres in the planning area. As stated above, most fires are relatively small compared to the state as a whole, the highest number of acres burned in the county was 19,131 during the 1996 Mercy fire. The county’s fire history from 1911-2020 is illustrated in Figure 4-39.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-139
Figure 4-39 Merced County Fire History, 1911-2020
Probability of Future Occurrences
Fire starts are highly likely during each fire season; though, they rarely result in large-scale wildfires in Merced County. Information obtained from the CAL FIRE Redbook lists multiple fires, the largest in the most recent past consumed approximately 3,800 acres. Based on climate and weather in Merced County and the fuels, topography, and a past fire history which indicates an average of 1.5 wildfires per year, it is likely that fires will continue to occur in the future. Figure 4-40 below shows the annual probability for wildfire in Merced County from 2026-2040, based on CAL FIRE GIS mapping.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-140
Figure 4-40 Merced County Annual Probability of Fire, 2026-2050
Climate Change Considerations
According to the 2018 California SHMP, climate change has the potential to impact the frequency, size, and severity of the wildfire hazard statewide. Increasing temperatures may intensify wildfire threat and susceptibility to more frequent wildfires in the county.
Exactly how climate change will affect total precipitation is not clear, but models suggest that there is a tendency for wetter conditions in the northern part of the state and drier conditions in the south (California Natural Resources Agency 2018a). Forests are also sensitive to variable precipitation events, as the 2012-2017 drought contributed to widespread tree mortality as warmer temperatures stressed trees and made them more susceptible to pests and pathogens (California Natural Resources Agency 2018).
Studies noted in California’s Fourth Assessment report note climate change impacts on wind patterns may strongly affect forests, potentially serving as a trigger mechanism for conversion of forest to other types of vegetation (California Natural Resources Agency 2018).
Current scientific models expect all of California will be affected by increased numbers of forest fires with added intensity due to longer warmer seasons, reduced distribution of biodiversity, lack of moisture, changes in ecosystems, drought impacts (e.g. pest diseases and continued spread of invasive species), and other impacts in coming years. The extending of the wildfire season into winter months, coinciding with seasonal high wind patterns, has contributed to severe fires in recent years. Southern California
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-141
experienced 29 wildfires in December of 2017 alone, and the deadliest and most destructive fire in California history, the Camp Fire, happened in November of 2018.
Vulnerability Assessment
Merced County vulnerability to wildfires varies, with some areas of the planning area being at greater risk than others as described further in this section. Generally, this hazard is a medium concern. High fuel loads in some areas of the planning area along with geographical and topographical features create the potential for both natural and human caused fires that can result in loss of life and property. These factors, combined with natural weather conditions common to the area, including periods of drought, low relative humidity, and periodic winds, can result in frequent and sometimes catastrophic fires. Even the relatively flat central parts of the county are not immune to fire; hot and sometimes windy weather combined with dry vegetation and a denser population can result in an increase in the number of ignitions.
Figure 4-41 through Figure 4-44 below are the result of a nationwide risk study from the United States Forest Service. These figures provide a perspective of wildfire risk and vulnerability compared to other CA counties. Populated areas in Merced County have, on average, greater risk to homes than 14% of counties in California. Populated areas in Merced County have, on average, greater wildfire likelihood than 18% of counties in California.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-142
Figure 4-41 Merced County Wildfire Likelihood
Source: USFS
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-143
Figure 4-42 Merced County Wildfire Likeli hood Compared to California Counties
Source: USFS
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-144
Figure 4-43 Merced County Wildfire Risk to Homes
Source: USFS
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-145
Figure 4-44 Merced County Wildfire Risk to Homes Compared to California Counties
Source: USFS
General Property
The potential impacts of wildfire on property include crop loss, injury and death of livestock and pets, and damage to infrastructure, homes and other buildings located throughout the wildfire risk area.
GIS was used to intersect the parcel boundaries with a master address point layer to obtain the number of buildings per parcel. Only parcels with improvement values greater than zero were used in the analysis, this method assumes that improved parcels have a structure of some type. This data was then overlaid on the Fire Threat Layer. For the purposes of this analysis, the wildfire hazard zone that intersected the address point was assigned as the hazard zone for the entire parcel. It was assumed that every parcel with an improved value greater than zero was developed in some way, thus only improved parcels and their values were analyzed.
An analysis of the value of those parcels – the improvement value plus estimated value of building contents – quantifies the potential losses from wildfires by severity zones. The results show that $3.7 billion worth of property and approximately 8,500 structures are exposed to fire risk countywide. The
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-146
majority of these buildings are in moderate to low hazard areas. The unincorporated areas and the City of Los Banos make up the majority of this risk. Residential properties constitute more than half of both the number of parcels and the projected losses. The total values shown in these tables include both structure value and contents and can be used as an estimate of potential losses since wildfires typically result in a total loss.
Table 4-68 Wildfire Hazard Exposure –Property Summary by Jurisdiction and Fire Threat Zone Jurisdiction Building
Count
Very
High
Building
Count
High
Building
Count
Moderate
Building
Count
Low
Total
Building
Count
Improved
Value
Estimated
Content Value
Total Value
Atwater 0 1 276 303 580 $158,646,509 $82,890,947 $241,537,456 Gustine 0 0 57 97 154 $26,104,098 $13,904,591 $40,008,689 Livingston 0 0 59 171 230 $91,308,401 $67,612,796 $158,921,197 Los Banos 0 2 198 976 1,176 $328,297,798 $178,953,729 $507,251,527 Merced 0 1 257 364 622 $156,504,212 $99,657,587 $256,161,799 Unincorporated 108 462 1,605 3,659 5,834 $1,373,680,176 $1,148,731,537 $2,522,411,713 Total 108 466 2,452 5,570 8,596 $2,134,541,194 $1,591,751,186 $3,726,292,380 Source: CAL FIRE, Merced County Assessor, Wood GIS analysis Figure 4-45 Unincorporated Area Buildings in Fire Threat Classes Source: CAL FIRE, Merced County Assessor, Wood GIS analysis People
Wildland fires result in a high risk for personal injury, loss of life to inhabitants of the fire area and firefighters, and losses of structures and personal property. Wildfires in or near the WUI frequently require emergency evacuation and sheltering, often for many days. As is shown in Table 4-68 below, approximately 17,364 people in Merced County reside in FHSZ. This figure was derived by taking the total number of residential structures identified in the FHSZs and multiplying them by the average household size in the county based off of 2019 U.S. Census Bureau estimates. 2%
8%
27%
63%
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2021-2026 Update Page 4-147
Table 4-69 Population at Risk to Fire Threat
Jurisdiction Population
Atwater 1,787
Gustine 399
Livingston 756
Los Banos 4,115
Merced 1,837
Unincorporated 8,469
Total 17,364
Source: Merced County, HIFLD, CAL FIRE, FRAP, U.S. Census Bureau, Wood GIS Analysis Other indirect impacts from wildfires on people are related to dense smoke from fires within the region.
Wildfires in the past three years have decreased the air quality throughout Merced County. Dense smoke poses a risk to both people with compromised health as well as those considered healthy. A study from the University of California San Diego found that wildfire smoke is more harmful to respiratory health in humans than pollution from cars (NPR 2021). Studies have also shown an increase in ambulance calls, hospital visits and an increase of people experiencing respiratory or cardiac emergencies (NPR 2020).
Critical Facilities and Infrastructure
Critical facilities are those community components that are most needed to withstand the impacts of disaster, as previously described in the Assets section. Wildfire impacts to critical facilities can include structural damage or destruction, risk to persons located within facilities, disruption of transportation, shipping, and evacuation operations, and interruption of facility operations and critical functions.
Critical facilities and infrastructure also create an increased risk for the occurrence of wildfires. Overhead electric transmission lines have been known to spark wildfires. According to data from the California Public Utilities Commission, the state’s three largest utility companies collectively reported 2,009 ignitions statewide between 2014-2017, including at least 50 in Merced County. Most of these instances were small, less than one acre in size, however these fires can grow rapidly under the right fire conditions. One such example is California’s deadliest wildfire, the 2018 Camp Fire in Northern California. Identifying critical facilities and infrastructure and mitigating their potential risks is important both for maintaining the county’s resilience and for reducing the potential impacts of wildfire. The locations of critical facilities identified by HIFLD throughout the county are summarized by their exposure the various wildfire threat levels in Table 4-69 through Table 4-72 below.
Table 4-70 Critical Facilities Within the Low Wild fire Threat by Jurisdiction and FEMA Lifeline Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Atwater 1 2 1 - - 1 1 6
Dos Palos - - - - - - - 0
Gustine - - - - - 1 1 2
Livingston 2 - - - - - - 2
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-148
Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Los Banos - - 1 - - 2 - 3
Merced - - 1 2 - 1 4 8
Unincorporated 20 18 2 3 - 17 156 216
Total 23 20 5 5 0 22 162 237
Source: Merced County, HIFLD, CAL FIRE, FRAP, Wood GIS Analysis Table 4-71 Critical Facilities Within the Modera te Wildfire Threat by Jurisdiction and FEMA Lifeline
Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Atwater - - - - - - 2 2
Dos Palos - - - - - - - 0
Gustine - - - - - 1 - 1
Livingston - - - - - - - 0
Los Banos - - - - - - - 0
Merced - - 1 - - 1 1 3
Unincorporated 10 10 - - - - 26 46
Total 10 10 1 0 0 2 29 52
Source: Merced County, HIFLD, CAL FIRE, FRAP, Wood GIS Analysis Table 4-72 Critical Facilities Within the High Wildfire Threat by Jurisdiction and FEMA Lifeline Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Atwater - - - - - - - 0
Dos Palos - - - - - - - 0
Gustine - - - - - - - 0
Livingston - - - - - - - 0
Los Banos - - - - - - - 0
Merced - - - - - - - 0
Unincorporated 17 26 1 - - 1 24 69
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-149
Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Total 17 26 1 0 0 1 24 69
Source: Merced County, HIFLD, CAL FIRE, FRAP, Wood GIS Analysis Table 4-73 Merced County Critical Facilitie s Within the Very High Wildfire Threat by Jurisdiction and FEMA Lifeline
Jurisdiction
Communications
Energy
Food, Water,
Shelter
Hazardous
Material
Health and
Medical
Safety and
Security
Transportation
Total
Atwater - - - - - - - 0
Dos Palos - - - - - - - 0
Gustine - - - - - - - 0
Livingston - - - - - - - 0
Los Banos - - - - - - - 0
Merced - - - - - - - 0
Unincorporated 5 115 - - - - 4 124
Total 5 115 0 0 0 0 4 124
Source: Merced County, HIFLD, CAL FIRE, FRAP, Wood GIS Analysis According to the analysis conducted, there are over 200 critical facilities exposed to at least a moderate wildfire threat area. The highest rates of exposure to wildfire threat areas are facilities in the Energy and Transportation Lifeline categories, both of which are crucial for response and evacuations in the event of a significant fire.
Economy
The economic impacts of wildfire include loss of property, direct agricultural sector job loss, secondary economic losses to businesses in or near wildland resources like parks and national forests, and loss of public access to recreational resources. Fire suppression may also require increased cost to local and state government for water acquisition and delivery, especially during periods of drought when water resources are scarce.
Effects on agriculture can be significant, which makes up a large portion of Merced County’s economy. In addition to the obvious impacts on crops and animals, wildland fire can have damaging effects on soil and water that will impact agriculture for an extended period of time.
Historic, Cultural, and Natural Resources
The County has 15 sites listed on the NRHP, and 28 listed on the California Register of Historical Resources. Since these structures are sensitive in nature and may not have been built according to the latest building codes due to their age, it is expected that they might be at risk of wildfires (e.g. because of their potential inability to withstand significant heat). Most of these structures are located in the Cities of DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-150
Merced and Los Banos, which are at lower risk to wildfire than unincorporated areas of the county.
However, parks and open spaces, particularly in the foothills in the eastern edge of the county, could also be at risk of a wildfire. This area is the region’s gateway to Yosemite National Park, which is a significant historic, cultural, and natural resource for the entire state of California.
Future Development
Any population increases in the Planning Area will continue to make wildfire vulnerability a growing issue, especially as future development expands into higher fire risk areas. These risks can however be managed with strong land use regulations and building code requirements, and with policies established in the Health and Safety Element of the 2030 General Plan. For example, policies requiring fire-resistant vegetation, clustered development, and vegetation clear zones in areas with high and extreme fire hazard.
Risk Summary
The overall significance of wildfire in Merced County is Medium. These events are recurring in nature and can cause significant damage, loss of life, and disruption to critical infrastructure.
Ɣ The county experiences an average of one wildfire every 1.5 years and an average of 1,500 acres burned per year. As impacts of climate change such as increased temperatures and prolonged drought conditions continue in coming years, this frequency and intensity may increase.
Ɣ Powerlines and vehicle or equipment use present a significant source of ignitions.
Ɣ Effects on people: Past wildfires in the county have not resulted in a large number of fatalities; however, significant evacuations and sheltering have been required in past events.
Ɣ Effects on property: Wildfires can destroy homes, businesses, and critical infrastructure. $3.7 billion worth of property in the County is located in a Fire Threat Zone.
Ɣ Effects on critical facilities and infrastructure: Wildfires can disrupt access to, or even destroy critical facilities and infrastructure.
Ɣ Effects on economy: Wildfires impacts can include loss of property, direct agricultural sector job loss, secondary economic losses to businesses, and loss of public access to recreational resources.
Ɣ Effects on Historic, Cultural, and Natural Resources: Wildfire can significantly impact water and air quality, even at great distances from the area burning. Damage to agriculture, natural resource areas, and habitats are very likely during a wildfire.
Ɣ Related Hazards: Drought, Agricultural Pest Infestation and Plant Disease, Landslide and Debris Flow.
Table 4-74 Hazard Summary - Wildfire
Jurisdiction Geographic
Extent
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Significant Likely Limited Medium
City of Atwater Significant Highly Likely Negligible Medium City of Dos Palos Limited Highly Likely Negligible Medium City of Gustine Limited Occasional Critical Low
City of Livingston Limited Occasional Negligible Low
City of Los Banos Significant Highly Likely Negligible Medium City of Merced Limited Highly Likely Negligible Medium
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-151
4.2.13Hazardous Materials Incidents
Hazard/Problem Definition
Generally, a hazardous material is a substance or combination of substances which, because of quantity, concentration, or physical, chemical, or infectious characteristics, may either cause or significantly contribute to, an increase in mortality or an increase in serious, irreversible, or incapacitating reversible, illness. Hazardous materials may also pose a substantial present or potential hazard to human health or environment when improperly treated, stored, transported, disposed of, or otherwise managed.
Hazardous material incidents can occur while a hazardous substance is stored at a fixed facility, or while the substance is being transported along a road corridor or railroad line or via an enclosed pipeline or other linear infrastructure.
The U.S. Department of Transportation (DOT), U.S. Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration all have responsibilities relating to the transportation, storage, and use of hazardous materials and waste. The Right to Know Network (RTK NET), maintained by the EPA’s National Response Center, is a primary source of information on the use and storage of hazardous materials, as well as data regarding spills and releases. The California Environmental Protection Agency and Department of Toxic Substances Control are authorized by the U.S. EPA to enforce and implement federal hazardous materials laws and regulations within the state. At the local level, Merced County’s Department of Public Health, Division of Environmental Health is the approved CUPA responsible for administration of permitting, inspections, and enforcement for hazardous waste and hazardous materials programs. The CUPA administers the Hazardous Material Business Plan (HMBPs), California Accidental Release Prevention (Cal-ARP) program, and the Aboveground Storage Act, as well as permitting and inspection activities for hazardous waste generators, and onsite hazardous waste treatment facilities, and underground storage tanks.
Hazardous materials can be divided into the following classes:
Ɣ Explosives
Ɣ Compressed gases: flammable, non-flammable compressed, poisonous Ɣ Flammable liquids: flammable (flashpoint below 141 degrees Fahrenheit), combustible (flashpoint from 141 - 200 degrees)
Ɣ Flammable solids: spontaneously combustible, dangerous when wet Ɣ Oxidizers and organic peroxides
Ɣ Toxic materials: poisonous material, infectious agents Ɣ Radioactive material
Ɣ Corrosive material: destruction of human skin, corrodes steel It is also common to see hazardous materials releases as escalating incidents resulting from other hazards such as floods, wildfires, and earthquakes. The release of hazardous materials can greatly complicate or even eclipse the response to the natural hazards disaster that caused the spill.
The Safety Element of the Merced County General Plan contains goals, policies, and implementation measures pertaining to hazardous materials, including radioactive materials and pesticides. Merced County also has an Emergency Operations Plan which contains provisions to address hazardous materials incidents, such as establishing a Hazardous Materials Unit Leader within the Operations Section and to establish response operations in the event of an incident involving hazardous materials (Merced County Emergency Operations Plan 2017).
Geographic Area
Hazmat incidents can occur at a fixed facility or during transportation.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Fixed Facilities
Hazardous materials facilities are identified and mapped by the counties they are located in, along with the types of materials stored there; facilities generally are located in and around developed areas. The Merced County Office of Emergency Services administers the Emergency Planning and Community Right- to-Know program for the planning area. Under Chapter 6.95 of the California Health and Safety Code and the Federal Resource Conservation and Recovery Act, any business storing quantities of hazardous materials greater than 55 gallons of liquid, 500 pounds of solid or 200 cubic feet of some compressed gases must file a HMBP annually that establishes incident prevention measures, hazardous material handling protocols and emergency response and evacuation procedures.
The EPA requires facilities containing certain extremely hazardous substances to generate Risk Management Plans (RMPs) and resubmit these plans every five years. According to the RTK NET, as of April 2021 there are 16 RMP facilities located in the County, as shown below in Figure 4-46.
The California Accidental Release Prevention Program (CalARP) is a statewide initiative to reduce the likelihood and severity of consequences of extremely hazardous materials releases. CalARP requires certain facilities (referred to as "stationary sources") which handle specified chemicals (termed "regulated substances") to take specified actions to proactively prevent and prepare for chemical accidents. Because the CalARP program is implemented at the local government level by the CUPAs, they can work directly with regulated facilities.
Figure 4-46 RMP Identified Hazardous Materials Facilities in Merced County
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-153
Transportation
In transit, hazardous materials generally follow major transportation routes, including road, rail and pipelines, creating a risk area immediately adjacent to these routes. The county’s transportation network, primarily Interstate 5, and State Highways 33, 59, 99, 140, 152, and 165, all have the potential for hazardous material incidents. Railroad lines and airports may also transport hazardous materials. The Hazardous Materials and Waste section of the Merced County General Plan Health and Safety Element establishes policies requiring that the transportation of all hazardous materials through the county be coordinated with the CHP (Merced County General Plan, 2013).
Hazardous materials releases can also result from natural disasters, such as floods or earthquakes that may cause containment systems to fail or affect transportation infrastructure. In summary, hazardous material incidents have the potential to occur in business and industrial areas (where fixed facilities are located) and along transportation corridors. Hazardous material incidents can also occur in agricultural areas; these types of facilities typically use pesticides, fertilizers, and other agricultural chemicals that are harmful to people and the environment. For example, agricultural pesticides and fertilizers are often transported daily around the planning area. Illegal drug operations and dumping sites have also been known to pose a hazardous materials threat.
Lastly, information provided by the National Pipeline Mapping System (NPMS) indicate several pipelines conveying gas or hazardous liquids cross the planning area, these are shown in Figure 4-47 and primarily travel north-south in the vicinity of Interstate 5 and Highway 99. Pipelines ruptures can result in major spills, or even explosions like the ones in San Bruno in 2010, and Fresno in 2015.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-154
Figure 4-47 National Pipeline Mapping System, Merced County Pipelines
Extent (Magnitude/Severity)
Hazardous materials come in the form of explosives, flammable and combustible substances, poisons and radioactive materials. Hazards can occur during production, manufacturing, storage, transportation, use, or disposal. Impacts from hazardous materials releases can include:
Ɣ Fatalities
Ɣ Injury
Ɣ Evacuations
Ɣ Property damage
Ɣ Animal fatalities (livestock, fish & wildlife)
Ɣ Air pollution
Ɣ Surface or ground water pollution/contamination
Ɣ Interruption of commerce and transportation
Numerous factors influence the impacts of a hazardous materials release, including the type and quantity of material, location of release, method of release, weather conditions, and time of day. This makes it
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-155
difficult to predict precise impacts. The impact to life and property from any given release depends primarily on:
Ɣ The type and quantity of material released.
Ɣ The human act(s) or unintended event(s) necessary to cause the hazard to occur.
Ɣ The length of time the hazard is present in the area.
Ɣ The tendency of a hazard, or that of its effects, to either expand, contract, or remain confined in time, magnitude, and space.
Ɣ Characteristics of the location and its physical environment that can either magnify or reduce the effects of a hazard.
CalFire notes several additional factors that can contribute to the impact of hazardous materials releases from a fixed facility or transportation incident:
Ɣ Solid, liquid, and/or gaseous hazardous materials can be released from fixed or mobile containers either accidentally or on purpose.
Ɣ The resulting release can last for hours or for days.
Ɣ The substances released may be corrosive or otherwise damaging over time, and they may cause an explosion and/or fire.
Ɣ Contamination may be carried out of the incident area by people, vehicles, water, and/or wind.
Ɣ Weather conditions will directly affect how the hazard develops.
Ɣ The micrometeorological effects of buildings and terrain can alter travel and duration of agents.
Ɣ Shielding in the form of sheltering in place can protect people and property from harmful effects.
Ɣ Noncompliance with fire and building codes as well as failure to maintain existing fire protection and containment features can substantially increase the damage from a hazardous materials release.
The release or spill of hazardous materials can also require different emergency responses depending on the amount, type, and location of the spill incident.
As noted above, the County contains a number of facilities that store and use significant quantities of hazardous materials. Additionally, a variety of hazardous materials are transported through the County by highway, rail, and pipelines, all of which are potentially vulnerable to accidental spills. Consequences can vary depending on whether the spill affects a populated area versus an unpopulated but environmentally sensitive area.
Potential losses can vary greatly for hazardous material incidents. For even a small incident, there are cleanup and disposal costs. In a larger scale incident, cleanup can be extensive and protracted. There can also be deaths or injuries requiring doctor’s visits and hospitalization, disabling chronic injuries, soil and water contamination can occur, necessitating costly remediation. Evacuations can disrupt home and business activities. Large-scale incidents can easily reach $1 million or more in direct damages, with clean- ups that can last for years.
Previous Occurrences
Merced County experiences multiple hazardous materials incidents every year. The vast majority of these incidents are minor with very localized impacts.
Table 4-74 breaks down 973 hazardous materials incidents reported to the California OES Warning Center from 2006 through 2021 based on location; this works out to an average of approximately 65 incidents per year. Even this total likely excludes a large number of unreported minor spills. 380 of these incidents occurred in transit, 381 occurred at a fixed location, and the remaining 211 had no location specified.
These hazardous material spills consisted of varying quantities of chemicals, petroleum, gasoline, sewage, and other materials. While the number of incidents can vary considerably from year to year, the average DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-156
number of hazardous materials spills or accidents in the County has trended upwards over the past 15 years. This is in line with the statewide trend, which has seen hazardous materials incidents increase by 30 percent during the same time period.
These incidents include both transportation and fixed facility incidents. This list in no way captures all hazardous material spills within the County, only those that were significant enough to be reported to Cal OES. The data indicates that hazardous materials incidents can occur across the county with a greater frequency in the more developed areas.
Table 4-75 Hazardous Materials Incidents in Merced County by Location, 2006-2021 Location Incidents Location Incidents
Merced 281 Delhi 15
Unknown 183 Winton 14
Atwater 81 EL Nido 11
Santa Nella 70 Le Grand 11
Unincorporated 67 Dos Palos 10
Los Banos 62 Planada 10
Livingston 55 Stevinson 9
Hilmar 36 Snelling 5
Gustine 29 Cressey 4
Ballico 17 Tuttle 1
Source: CalOES Spill Release Reporting
The vast majority of these hazardous materials incidents have only minimal life safety impacts. One event in July 2019 resulted in one death and nine hospitalizations after a chemical spill in Los Banos.
Another database maintained by the U.S. Coast Guard reports 205 incidents recorded in Merced County, with 13 of them resulting in confirmed injuries from 1998 to 2013, with 32 individuals injured. There have also been 7 confirmed fatalities in the county from 2000 to 2019. Some incidents may also result in temporary evacuations, closures of transportation routes, or damage to facilities. This translates to roughly 6% of incidents resulting in injuries and 3% resulting in a fatality.
The Toxic Release Inventory (TRI) is a resource for learning about toxic chemical releases and pollution prevention activities by industrial and federal facilities. Section 313 of the Emergency Planning and Community Right-to-Know Act created the TRI program. According to the TRI database, there were 13 facilities within the County in 2019 that have collectively produced or managed approximately 9.6 million pounds of waste (US EPA 2021). These facilities dispose, treat, recover, and recycle various types of waste and chemicals and ultimately “release” the waste or chemicals into the air or water, or some form of land disposal.
Probability of Future Occurrences
Highly Likely - As discussed above, the County experiences an average of 65 hazardous materials incidents per year, with various degrees of impact; there is effectively a 100 percent chance that the County will see a hazardous materials incident in any given year. However, hazardous materials incidents that cause deaths, injuries, or evacuations are far rarer, occurring in between 3 and 6% of occurrences on average. These can occur at any time and with little predictability given the presence of major transportation routes in throughout the County.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-157
Climate Change Considerations
There are no known effects of climate change on human caused hazards, such as hazardous material incidents. However, it is possible that an increase in other hazards, such as severe storms and fire events may increase the likelihood of an accidental hazardous materials release.
Vulnerability Assessment
General Property
The impact of a fixed hazardous facility, such as a chemical processing facility is typically localized to the property where the incident occurs. The impact of a small spill (i.e. liquid spill) may also be limited to the extent of the spill and remediated if needed. A blanket answer for potential impacts is hard to quantify, as different chemicals may present different impacts and issues. Property within a half mile in either direction of designated hazardous materials routes are at increased risk of impacts. While cleanup costs from major spills can be significant, they do not typically cause significant long-term impacts to property.
People
Hazardous materials incidents can cause injuries, hospitalizations, and even fatalities to people nearby.
People living near hazardous facilities and along transportation routes may be at a higher risk of exposure, particularly those living or working downstream and downwind from such facilities. For example, a toxic spill or a release of an airborne chemical near a populated area can lead to significant evacuations and have a high potential for loss of life.
In addition to the immediate health impacts of releases, a handful of studies have found long-term health impacts such as increased incidence of certain cancers and birth defects among people living near certain chemical facilities. However there has not been sufficient research done on the subject to allow detailed analysis.
Social Vulnerability
While hazardous material incidents could take place anywhere across the County and may be unpredictable, those living near HazMat facilities or along transportation routes that additionally happen to be socially vulnerable communities would be of highest concern. Based on a combination of the SoVI data presented and discussed in subsection 4.2.1 and the presence of major transportation routes and EPA or CalARP regulated facilities the most vulnerable populations include Merced, Atwater, and Livingston. In addition, agricultural farm workers are most vulnerable to pesticide exposure and other hazardous material incidents associated with the agricultural operation.
Critical Facilities and Infrastructure
Impacts of hazardous material incidents on critical facilities are most often limited to the area or facility where they occurred, such as at a transit station, airport, fire station, hospital, or railroad. However, they can cause long-term traffic delays and road closures resulting in major delays in the movement of goods and services. These incidents would be more severe if they result in traffic delays on road closures on any of the designated truck routes or hazardous materials routes in the County. These impacts can spread beyond the planning area to affect neighboring counties, or vice-versa. While cleanup costs from major spills can be significant, they do not typically cause significant long-term impacts to critical facilities.
Economy
The primary economic impact of hazardous material incidents result in lost business, delayed deliveries, property damage, and potential contamination. Large and publicized hazardous material-related events can deter tourists and recreationists too. If incidents occur along major transportation corridors, they can DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
2021-2026 Update Page 4-158
temporarily close routes and result in traffic delays. Economic effects from major transportation corridor closures can be significant.
Historic, Cultural, and Natural Resources
Hazardous material incidents may affect a small area at a regulated facility or cover a large area outside such a facility. Widespread effects occur when hazards contaminate the groundwater and eventually the municipal water supply, or they migrate to a major waterway or aquifer. Impacts on wildlife and natural resources can also be significant. These types of widespread events may be more likely to occur during a transportation incident, such as a pipeline spill, and can have far reaching and devastating impacts on the natural environment and habitats if they occurred near one of the several wildlife refuges in Merced County.
Future Development
The amount of hazardous materials that are stored, used, and transported across the County are inferred to continue to increase over the next five years based on regional growth trends. As discussed previously, the number of hazardous materials incidents in the County has generally been increasing year to year for the last 15 years and is likely to continue to increase. Future development is also expected to increase the number of people potentially exposed to the impacts of hazardous materials incidents.
Risk Summary
The overall significance of hazardous materials incidents in Merced County is Medium. These incidents occur frequently with little to no warning, both at fixed sites and along transportation routes throughout the County. The possibility of a major spill impacting a major populated area exists; historically the impacts of these incidents on the County as a whole have been fairly limited.
Ɣ Over the past 15 years, the County experienced an average of 65 hazardous materials incidents per year. This number has generally been trending higher in recent years. Incidents that caused death or injuries were far rarer.
Ɣ Of the 972 hazardous material incidents over the past 15 years, 39 percent were transportation related, 39 percent occurred at fixed facilities; the remaining 22 percent have an unreported location.
Ɣ Several pipelines conveying gas or hazardous liquids cross the County, as shown in the NPMS.
Ɣ Hazardous materials releases can complicate response to and recovery from natural disasters such as floods and earthquakes.
Ɣ Hazardous Materials incidents can cause injuries and fatalities, as well as long-term health problems like increased cancer risks.
Ɣ Impacted properties can require cleanup, but the effects are usually localized to the site of the release.
Ɣ Extended road closures can result in economic losses and impact tourism.
Ɣ Impacted facilities and infrastructure can require cleanup, but the effects are usually localized to the site of the release.
Ɣ Related Hazards include Earthquake, Flood, Fire.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-76 Hazard Summary – Hazardous Materials Incidents Jurisdiction Geographic
Extent
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Limited Highly Likely Negligible Low
City of Atwater Limited Occasional Negligible Medium
City of Dos Palos Limited Occasional Negligible Medium
City of Gustine Significant Unlikely Critical Low
City of Livingston Limited Occasional Negligible Medium City of Los Banos Significant Likely Critical Medium
City of Merced Limited Likely Negligible Medium
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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4.2.14Cyber Attack
Hazard Problem/Definition
The 2018 California SHMP defines cyber attacks as “attempts by cyber criminals to attack a government, organization, or private party by damaging or disrupting a computer or computer network, or by or stealing data from a computer or computer network for malicious use.” Cyber-attacks use malicious code to alter computer operations or data. The vulnerability of computer systems to attacks is a growing concern as people and institutions become more dependent upon networked technologies. The Federal Bureau of Investigation reports that, “cyber intrusions are becoming more commonplace, more dangerous, and more sophisticated,” with implications for private- and public-sector networks. Cyber threats can take many forms, including:
Phishing attacks: Phishing attacks are fraudulent communications that appear to come from legitimate sources. Phishing attacks typically come through email but may come through text messages as well.
Phishing may also be considered a type of social engineering meant to exploit employees into paying fake invoices, providing passwords, or sending sensitive information.
Malware attacks: Malware is malicious code that may infect a computer system. Malware typically gains a foothold when a user visits an unsafe site, downloads untrusted software, or may be downloaded in conjunction with a phishing attack. Malware can remain undetected for years and spread across an entire network.
Ransomware: Ransomware typically blocks access to a jurisdiction’s/agency’s/ business’ data by encrypting it. Perpetrators will ask for a ransom to provide the security key and decrypt the data, although many ransomware victims never get their data back even after paying the ransom.
Distributed Denial of Service (DDoS) attack: Perhaps the most common type of cyber attack, a DDoS attack seeks to overwhelm a network and causes it to either be inaccessible or shut down. A DDoS typically uses other infected systems and internet connected devices to “request” information from a specific network or server that is not configured or powerful enough to handle the traffic.
Data breach: Hackers gaining access to large amounts of personal, sensitive, or confidential information has become increasingly common in recent years. In addition to networked systems, data breaches can occur due to the mishandling of external drives.
Critical Infrastructure/SCADA System attack: There have been recent critical infrastructure Supervisory Control and Data Acquisition (SCADA) system attacks aimed at taking down lifelines such as power plants and wastewater facilities. These attacks typically combine a form of phishing, malware, or other social engineering mechanisms to gain access to the system.
The 2018 California SHMP states: “Nationally, cybersecurity incidents such as financial fraud and government database breaches have increased from 5,503 in 2006 to 67,168 in 2014.” This is more than a 1200% increase in occurrence over just an 8-year period. As this trend continues and society and government functions become ever more technologically dependent, this hazard is of increasing concern.
In one recent attempt to combat this threat, the State of California adopted Senate Bill 327 in September of 2018. This bill seeks to improve information privacy, specifically pertaining to connected devices.
Existing laws in California require businesses to take all reasonable steps to dispose of customer records within their custody containing personal information and also require businesses that own, license, or maintain personal information about a California resident to implement and maintain reasonable security procedures. SB 327, which went into effect January 1, 2020 further requires the manufacturer of connected devices to equip the device with a reasonable security feature to protect user information (Senate Bill 327).
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Geographic Area
Cyber attacks can and have occurred in every location regardless of geography, demographics, and security posture. Incidents may involve a single location or multiple geographic areas. A disruption can have far reaching effects beyond the location of the targeted system; disruptions that occur far outside the state can still impact people, businesses, and institutions within the county. All of Merced County is potentially susceptible to cyber attacks, making the geographic extent significant.
Extent (Magnitude/Severity)
There is no universally accepted scale to explain the severity of cyber attacks. The strength of a DDoS attack is often explained in terms of a data transmission rate. One of the largest DDoS disruptions ever, the October 21, 2016 Dyn attack, peaked at 1.2 terabytes per second and impacted some of the internet’s most popular sites that included Amazon, Netflix, PayPal, Twitter, and several news organizations.
Data breaches are often described in terms of the number of records or identities exposed. The Privacy Rights Clearinghouse, a nonprofit organization based in San Diego, maintains a database of data breaches in the United States. The largest data breach ever reported occurred in August 2013, when hackers gained access to all three billion Yahoo accounts. This incident is associated with California in the Privacy Rights Clearinghouse database as the company is headquartered in Sunnyvale, California. As the location of the headquarters of many large tech businesses and server farms, California as a state is potentially a greater target for cyber attacks. There have been many other instances in the state where millions of records have been breached.
Ransomware attacks are typically described in terms of the amount of ransom requested, or by the amount of time and money spent to recover from the attack. One report from cybersecurity firm Emsisoft estimates the average successful ransomware attack costs $81 million and can take organizations 287 days to recover. Overall, the potential magnitude of a cyber attack can be seen as limited due to the lack of deaths and injuries, but the economic costs can be significant.
Previous Occurrences
The cybersecurity firm Symantec reports there were a total of 1,209 data breaches worldwide in 2016.
While the number of breaches has remained relatively steady, the average number of identities stolen has increased to almost one million per incident. The report also found that one in every 131 emails contained malware, and the company’s software blocked an average of 229,000 web attacks every day.
California is by far the state with the highest number of data breaches. The Privacy Rights Clearinghouse database lists 1,338 data breaches against systems located in California, totaling over 5.7 billion impacted records; however, it is difficult to know how many of those affected Merced County residents. Attacks happening outside of the state can also impact local businesses, personal identifiable information, and credit card information.
A 2017 study found ransomware payments over a two-year period totaled more than $16 million. Even if a victim is perfectly prepared with full offline data backups, recovery from a sophisticated ransomware attack typically costs far more than the demanded ransom. However, according to a 2016 study by Kaspersky Lab, roughly one in five ransomware victims who pay their attackers never recover their data.
Recent years have seen an increase in ransomware attacks, particularly against local government systems.
The City of Atlanta was hit by a major ransomware attack in 2018, recovery from which wound up costing a reported $2.6 million, significantly more than the $52,000 ransom demand. A similar attack against the City of Baltimore in 2019 affected the city government’s email, voicemail, property tax portal, water bill, and parking ticket payment systems, and delayed more than 1,000 pending home sales. In March 2019, DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Orange County, North Carolina was attacked with a ransomware virus, causing slowdowns and service problems at key public offices such as the Register of Deeds, the Sheriff’s Office, and county libraries. The attack impacted a variety of county services, including disrupting the county’s capability to process real estate closings, issue marriage licenses, process fees or permits, process housing vouchers, and verify tax bills. Each of these past events are examples of the range of risks posed to county and municipal governments by various cyber attacks.
Reports of successful attacks against SCADA systems are less common. In February 2021, a hacker gained system access to a water treatment plant in Oldsmar, Florida and increased the levels of sodium hydroxide to dangerous levels; however, this change was immediately detected by plant staff and corrected.
A large, sophisticated malware attack, known as Olympic Destroyer, was launched against the 2018 Winter Olympics in PyeongChang, South Korea. The attack initially took down servers, email, Wi-Fi, and ticketing systems, which could have severely disrupted the games. Fortunately, the organizing committee had a robust cybersecurity group that was able to quickly restore most functions.
Probability of Future Occurrences
Small-scale cyber attacks such as DDoS attacks occur daily, but most have negligible impacts at the local or regional level. Data breaches are also extremely common, but again most have only minor impacts on government services.
Perhaps of greatest concern to Merced County are ransomware attacks, which are becoming increasingly common. It is difficult to predict the odds of Merced County being hit with a successful ransomware attack in any given year, but it is safe to say it is likely to be attacked in the coming years.
The possibility of a larger disruption affecting systems within the County is a constant threat, but it is difficult to quantify the exact probability due to such highly variable factors as the type of attack and intent of the attacker. Major attacks specifically targeting systems or infrastructure in the County cannot be ruled out.
Climate Change Considerations
There are no known effects of climate induced impacts on cyber attacks.
Vulnerability Assessment
The impact of a cyber attack can vary depending on the type of attack and the intent of the malicious actor. Though a cyber disruption can have limited impacts within a system’s own operations, it may cause cascading impacts.
General Property
The vast majority of cyber attacks affect only data and computer systems and have minimal impact on general property.
People
Injuries or fatalities from cyber attacks would generally only be possible from a major cyber terrorist attack against critical infrastructure, such as potable water treatment and delivery systems. If such an event would occur it could indirectly impact the customers served by water utility. More likely impacts to the public are financial losses and an inability to access systems such as public websites and permitting sites. Indirect impacts could include interruptions to traffic control systems or other infrastructure DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Data breaches and subsequent identify thefts can have huge impacts on the public. The Internet Crime Complaint Center (IC3) estimates that identity theft alone resulted in $2.7 billion in losses to businesses and $149 million in losses to individuals.
According to the Cyber & Infrastructure Security Agency (CISA), cyber risks to 9-1-1 systems can have “severe impacts, including loss of life or property; job disruption for affected network users; and financial costs for the misuse of data and subsequent resolution.” CISA also compiled a recent list of attacks on 9- 1-1 systems including a DDoS in Arizona, unauthorized access with stolen credentials in Canada, a network outage in New York, and a ransomware attack in Baltimore.
Critical Facilities and Infrastructure
While the vast majority of cyber attacks affect only data and computer systems, sophisticated attacks against utilities and infrastructure sites have occurred. Such attacks typically target the SCADA systems of critical infrastructure, which can potentially result in system failures on a scale equal with natural disasters.
Facilities and infrastructure, such as the electrical grid, could become unusable as a result of a cyber attack. A cyber attack took down the power grid in Ukraine in 2015, leaving over 230,000 people without power. Agencies that rely on electronic backup of critical files are also vulnerable.
The delivery of services can be impacted since governments rely to a great extent upon electronic delivery of services. Most agencies rely on server backups, electronic backups, and remote options for Continuity of Operations or the Continuity of Government. Many departments in the participating jurisdictions have the option to move to a paper method including permitting, DMV services, payments to and from the county, and payroll. However, access to documents on the network, OneDrive access, and other operations that require collaboration across the County will be significantly impacted.
Loss of government servers due to a cyber attack could affect the ability of responders to do their jobs.
Cyber attacks can interfere with emergency response communications, access to mobile data terminals, and access to critical preplans and response documents.
The delivery of services can be impacted since governments rely, to a great extent, upon electronic delivery of services. An attack could raise questions regarding the security of using electronic systems for government services.
Economy
Economic impacts from a cyber attack can be debilitating. The cyber attack in 2018 that took down the City of Atlanta cost at least $2.5 million in contractor costs and an estimated $9.5 million additional funds to bring everything back online. The attack in Atlanta took “more than a third of the 424 software programs offline” and recovery lasted more than 6 months. A 2018 cyber attack on the Colorado Department of Transportation cost an estimated $1.5 million. None of these statistics take into account the economic losses to businesses and ongoing IT configuration to mitigate from a future cyber attack.
Historic, Cultural, and Natural Resources
The vast majority of cyber incidents have little-to-no impact on historic, cultural or natural resources. A major cyber terrorism attack could potentially impact the environment by triggering a release of a hazardous materials, or by causing an accident involving hazardous materials by disrupting traffic control devices.
Future Development
Changes in development have no impact to the threat, vulnerability, and consequences of a cyber attack.
Cyber attacks can and have targeted small and large jurisdictions, multi-billion-dollar companies, small DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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mom-and-pop shops, and individual citizens. The decentralized nature of the internet and data centers means that the cyber threat is shared by all, regardless of new construction and changes in development.
Risk Summary
The overall significance of cyber attacks in Merced County is Medium. These incidents occur frequently, with California being the state with by far the most reported incidents. The possibility of an attack of any scale impacting the County is almost certain.
Ɣ There have been 1,338 data breaches statewide over a 14-year period, averaging approximately 96 incidents per year.
Ɣ Nationwide the increase in cyber attacks has been dramatic year over year. As this trend continues it is safe to assume there is a threat to Merced County.
Ɣ Injuries and fatalities to people are unlikely, unless in a widescale attack that affected infrastructure and resulted in indirect impacts on communities. People may also be impacted financially.
Ɣ The vast majority of attacks do not affect property.
Ɣ Economic impacts from a cyber attack can be debilitating, sometimes costing local governments millions of dollars.
Ɣ The vast majority of attacks target only computer systems, however sophisticated attacks against utilities and infrastructure, such as electrical grids, have occurred.
Table 4-77 Hazard Summary – Cyber Attack
Jurisdiction Geographic
Extent
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Significant Likely Critical Medium
City of Atwater Limited Occasional Negligible Medium
City of Dos Palos Limited Occasional Negligible Medium
City of Gustine Limited Unlikely Limited Low
City of Livingston Limited Occasional Negligible Medium City of Los Banos Significant Likely Negligible Medium
City of Merced Limited Occasional Negligible Low
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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4.2.15 Agricultural Pests and Disease
Hazard/ Problem Description
Located in the Central San Joaquin Valley, Merced County’s farming and agricultural industry is ranked as the top agriculture-producing county in California and the country. Agriculture is the dominant land use in Merced County, accounting for more than 90% of all land. According to the Merced County Department of Agriculture, agriculture grossed more than 3 billion dollars in 2019. Top commodities since 2018 included milk, almonds, and cattle (see table below).
Table 4-78 Top 15 Commodities in Merced County in 2018
Rank Change since 2017 Crop 2019 Value Top 15 Share
1 -- Milk $905,116,000 31.3%
2 -- Almonds $421,254,000 14.6%
3 Increase Cattle and Calves $297,451,000 10.3%
4 Decrease Chickens $294,633,000 10.2%
5 -- Sweet Potatoes $234,946,000 8.1%
6 -- Tomatoes $126,790,000 4.4%
7 -- Silage – Corn $108,077,000 3.7%
8 Increase All Nursery Products $84,515,000 2.9%
9 Decrease Hay – Alfalfa $69,943,000 2.4%
10 Decrease Eggs, Chicken $64,668,000 2.2%
11 Increase Misc. Vegetables $60,709,000 2.1%
12 -- Grapes – Wine $56,748,000 2.0%
13 Decrease Cotton – Pima $45,799,000 1.6%
14 -- Turkeys $43,490,000 1.5%
15 Increase Pollination $41,284,000 1.4%
Top 15 Total $2,890,875,000
Source: 2019 Report on Agriculture
Agricultural pests and pathogens (insects, fungi, bacteria, viruses and invasive plants) cause injury or severe destruction to crops or livestock. From exotic fruit flies to noxious weeds, California’s agriculture can be impacted by a wide variety of invasive pests and pathogens. These pests pose significant threats to the state’s agricultural crops, farm workers, economy, food supply and native habitat. They can also result in increases in food prices for consumers. The number of invasive pests and pathogens newly detected in California and the rest of the United States has increased at alarming rates in recent years, and that trend is projected to continue into the future. Insect pests and diseases, such as bark beetles and Sudden Oak Death in trees can also destroy forests and oak woodland habitat located along the eastern and western perimeters of Merced County, which can in turn increase the fuel load and lead to greater fire risk.
Agricultural disasters could also occur due to severe weather events, such as extreme heat, freeze cycles, and heavy rainfall and these hazards are covered under subsections 4.3.6 through 4.3.10. Drought events are covered under subsection 4.3.2.
The California Food and Agricultural Code mandates pest prevention programs to prevent the introduction and spread of pests in California. These include the Pest Exclusion Program, Pest Detection Program, Pierce’s Disease Control Program, and Federal Phytosanitary Certificate Program. Target pests are listed in Table 4-70, but also include dairy, livestock, and poultry pests and diseases, such as Mycobacterium bovis and pathogenic avian influenzas. Animal agriculture, such as dairy farms also result in copious amounts of manure, which contain zoonotic pathogens, which are viruses, bacteria, and parasites of animal origin that cause disease in humans.
DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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Table 4-79 Target Pests in Merced County
Target Pest Insect Hosts Traps Placed
Asian Citrus Psyllid Citrus 620
European Pine Shoot Moth Pine Trees 3
Glassy-Winged Sharpshooter Nurseries/Urban
Areas
392
Light Brown Apple Moth Ornamental 288
Melon Fruit Fly Vegetable
Gardens
95 Oriental Fruit Fly Fruit Trees 320
European Corn Borer Corn 5
Gypsy Moth Shade Trees 107
Japanese Beetle Turf, Rose 100
Mediterranean Fruit Fly Fruit Trees 320
Mexican Fruit Fly Fruit Trees 169
Sweet Potato Weevil Sweet Potatoes 120
Source: 2019 Report on Agriculture
Geographic Area
According to the 2017 Census for Agriculture, Merced County contains almost 1 million agricultural acres.
Cropland accounts for 58% of agricultural land, while pastureland accounts for 38%. There are approximately 2,337 farms (as of 2017) in the County.
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Figure 4-48 Merced County Important Farmland
Extent (Magnitude/Severity)
Different pests can impact different crops in different ways; while there is no scale to define the extent of an infestation, a pest could have a major economic impact on the value of infested crops.
Another large factor that may influence crop yield is the spread of invasive plants, which may compete with crops for resources and in some cases also introduce pests. According to California Invasive Plant Council (Cal-IPC), invasive plants cost California $82 million every year in control, monitoring and outreach; estimated actual impacts can reach into the billions. Based on the USDA’s RMA Crop Indemnity Reports, between 2007 and 2019 (no losses were reported in 2020), there were 734.6 acres lost due to plant disease and insects and $256,962 indemnity payments made.
Past Occurrences
Based on information from the USDA, Merced County received several USDA disaster declarations since 1950 (see Table 4-3 above). All the declarations were associated with flood, drought or severe weather events, and most recently, the COVID-19 pandemic. None were related to agricultural disease.
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Probability of Future Occurrences
While probability of future occurrence is usually calculated based on past experience, different pests have different recidivism rates across the County. Based on past occurrences, pests and invasive species will continue to present a constant threat to the County and its jurisdictions.
Climate Change Considerations
California’s Fourth Climate Change Assessment (2018) notes that “climate change impacts terrestrial ecosystems and wildlife in multiple ways, including invasion by exotic species, prevalence of wildlife disease, and loss of native habitats.” Changing climate conditions can impact viable living areas of species and cause migration; shift the spread of pests and disease northward by changing habitat temperatures and making previously undesirable habitats welcoming for new species and lengthen habitable seasons (CNRA 2018a). Longer growing seasons may also allow agricultural pests to persist longer, which can increase the severity of infestations on agricultural operations. Further, weather events have become more numerous and more severe. Changes in weather patterns can also have dramatic impacts on the ecosystem, including agriculture systems, and more severe impacts can be expected into the future.
Vulnerability Assessment
General Property
Agricultural losses occur on an annual basis and are usually associated with severe weather events, including heavy rains, floods, hail, freeze, and drought. The State of California Multi-Hazard Mitigation Plan attributes most of the agricultural disasters statewide to drought, freeze, and insect infestations.
Other agricultural hazards include fires, crop and livestock disease, noxious weeds, and contamination of animal food and water supplies.
Infestation of agriculture pests could impact crop yields, potential destroying whole fields. Between 2015 and 2018, the RMA paid no indemnities due to damage from insects but paid $22,900 in indemnities due to damage from crop disease.
People
A widespread infestation of livestock and crops could severely impact the economic base of the County and its communities employed by the agriculture industry. According to the USDA 2017 Census of Agriculture, Merced County has 2,337 farms, which is a -6% change from the previous census in 2012.
While agricultural production in the County can enhance the economy and improve human health and ensure stable food prices in California and the U.S., certain habitats established for irrigation and agricultural output can also threaten human health by increasing the risk of vector-borne diseases (e.g. mosquitos, etc.). Rural communities, residing closest to these agricultural operations may also be most vulnerable to these diseases, as livestock pathogens are capable of infecting host species, which may include wildlife and human.
Jobs could be negatively impacted during an agriculture emergency; jobs tangentially tied to the agriculture industry could also be affected. According to “The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment”, rising temperatures and drought conditions due to climate change could also lead to increases in the occurrence and transport of pathogens in agricultural environments, which will increase the risk of food contamination and direct human exposure to pathogens and toxins (SGCRP 2016). In turn, this will increase health risks and require greater vigilance in food safety practices and regulation.
Disease can also exacerbate the impacts from other natural hazards. An example of this is adverse weather. Dead branches can be broken by high winds, and there are reports of these branches falling and causing harm to people.
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Social Vulnerability
Based on the SoVI data presented and discussed in subsection 4.2.1, the areas with the highest level of social vulnerability in the County are in the western and southeastern portion of the County, as well as some of the incorporated jurisdictions including Merced and Los Banos. These communities as well as those working in the agricultural sector would likely be impacted by the effects of agricultural hazards.
Critical Facilities
Critical facilities assessed in this plan would not be directly impacted by agricultural pests or diseases; however, the food and agriculture industry is considered critical infrastructure in Merced County and California. Impacts to this infrastructure, such as farms, diary operations, and processing facilities would have debilitating effects of food security, the economy, and public health and safety. Merced County farms and ranches, and the associated food processing facilities would be directly impacted economically by long-term disruptions in the food supply associated with crop losses due to agricultural pests and disease.
Economy
According to the University of California’s Center for Invasive Species Research, it has been estimated in California alone that invasive pests cost the state at least $3 billion per year. Nationally, it is estimated that invasive species cost the U.S. $138 billion per year. Economic impacts include both prevention, response and recovery costs. Given the contribution of agriculture to the local economy pest impacts could be significant. The value of agricultural commodities noted at the beginning of this hazard profile is $2,890,875,000. Based on that a hypothetical loss of 5% to due to agricultural pest or disease would equate to approximately $144M.
Historic, Cultural and Natural Resources
Invasive species typically harm native species through predation, habitat degradation and competition for shared resources; they can outcompete native species out of natural habitats and are a leading cause of population decline and extinction in animals.
Tree mortality raises the wildfire threat in healthy forests, increasing the vulnerability, strength, speed and destruction of fires in the area.
Future Development
Most likely, good development practices in the future would not have an impact on Merced County’s vulnerability to agricultural pests, plant diseases, marine invasive species or tree mortality.
Risk Summary
Ɣ Merced County’s farming and agricultural industry is ranked as the top agriculture-producing county in California and the country.
Ɣ Agriculture is the dominant land use in Merced County, accounting for more than 90% of all land, or almost 1 million acres.
Ɣ Invasive plants cost California $82 million every year in control, monitoring and outreach.
Ɣ Based on USDA disaster declarations since 1950, none were related to agricultural pests or disease.
Ɣ Changes in weather patterns can have dramatic impacts on the ecosystem, including agriculture systems, and more severe impacts associated with agricultural pests and disease can be expected into the future.
Ɣ Changing climate conditions can shift the spread of pests and disease northward by changing habitat temperatures and making previously undesirable habitats welcoming for new species through longer growing seasons. This may increase the severity of pest infestations on agricultural operations.
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Ɣ Related hazards: Drought
Table 4-80 Risk Summary – Agricultural Pests, and Disease Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Likely Critical Medium
City of Atwater Extensive Likely Critical Medium
City of Dos Palos Extensive Likely Critical Medium
City of Gustine Extensive Likely Critical Medium
City of Livingston Extensive Likely Critical Medium
City of Los Banos Extensive Likely Critical Medium
City of Merced Extensive Likely Critical Medium
Merced County Multi-Jurisdictional Hazard Mitigation Plan Hazard Identification and Risk Assessment
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4.2.16Pandemics/Epidemics
Hazard/Problem Description
A pandemic can be defined as a disease that attacks a large population across great geographic distances.
Pandemics are larger than epidemics in terms of geographic area and number of people affected.
Epidemics tend to occur seasonally and affect much smaller areas. Pandemics, on the other hand, are most often caused by new subtypes of viruses or bacteria for which humans have little or no natural resistance. Consequently, pandemics typically result in more deaths, social disruption, and economic loss than epidemics.
There are three conditions that trigger a pandemic declaration:
1. A new virus subtype must emerge that has not previously circulated in humans (and therefore there is no pre-existing immunity),
2. This new subtype must be able to cause disease in humans, and
3. The virus must be easily transmissible from human-to-human.
Since March 2020, Merced County, the nation, and the world are dealing with the COVID-19 pandemic (caused by the SARS-CoV-2 virus), confirming that pandemic is a key public health hazard in the planning area. This hazard risk assessment includes an analysis of pandemic risk across Merced County and an analysis of the impacts of the hazards profiled in this plan on public health.
Unlike seasonal flu, a pandemic has much greater potential for loss of life and significant social disruption due to higher rates of transmission and more severe health impacts. The SARS-CoV-2 virus has a much higher rate of transmission than the seasonal flu, primarily by airborne transmission of droplets/bodily fluid. Common symptoms include fever, cough, fatigue, shortness of breath or breathing difficulties, and loss of smell and taste. While most people have mild symptoms, some people develop acute respiratory distress syndrome with roughly one in five requiring hospitalization in the United States and a fatality rate between 1 to 2 percent. Because the virus can be transmitted by people who are asymptomatic, and due to the presence of several variants of SARS-CoV-2, containing the spread has been a significant challenge across the globe.
Geographic Area
Pandemics occur not only on a county or state level, but on a national and global scale. It is likely that most communities in Merced County would be affected, either directly or by secondary impacts. Some indirect consequences may be the diversion of resources that may be otherwise available.
Merced County has reported 31,009 cases and 448 deaths from COVID-19 as of April 11, 2021. According to the Merced County Public Health COVID-19 dashboard, the City of Merced has the highest number of cases (approximately 11,100 as of April 12, 2021, and the City of LeGrand Planada and City of Hilmar have the lowest number of cases in the 700-800 range) as of April 9, 2021. This is likely because cities like Merced have higher populations and municipal areas relative to other cities within the county, and COVID-19 is transmitted primarily from human-to-human contact.
Another example of a human health hazard that is endemic to Merced County is Valley Fever, or “cocci” which is a known, but poorly understood secondary effect of drought conditions, and possibly a combination of wind and drought events followed by a rainy season. Valley Fever is an infection caused by a fungus (Coccidioides immitis) that lives in soil and dirt and in areas with low rainfall, high summer temperatures, and moderate winter temperatures. Valley Fever is primarily a disease of the lungs that is common in the southwestern United States and northwestern Mexico. Valley Fever derives its name from DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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its discovery in the San Joaquin Valley of California. While the extent of Valley Fever varies from southwestern United States, northern Mexico, and some parts of Central and South America, the known endemic area in California include portions of the Sacramento Valley, all of the San Joaquin Valley, and desert regions and southern portions of California. Individuals are likely to be affected by Valley Fever if they live in an area where the cocci fungus is prevalent.
Extent (Magnitude/Severity)
The magnitude of a public health emergency will range significantly depending on the transmissivity and mortality rate of the virus. For example, pandemic influenza is easily transmitted from person-to-person, however advances in medical technologies have greatly reduced the number of deaths caused by influenza over time.
Today, a much larger percentage of the world’s population is clustered in cities, making them ideal breeding grounds for epidemics. Additionally, the explosive growth in air travel means the virus could spread around the globe within hours. Under such conditions, there may be very warning little time for counties, states, and countries to prepare. Most experts believe we will have just one to six months between the time that a dangerous new influenza strain is identified and the time that outbreaks begin to occur in the United States. Outbreaks are expected to occur simultaneously throughout much of the nation, preventing shifts in human and material resources that normally occur with other natural disasters.
These and many other aspects make pandemics unlike any other public health emergency or community disaster. Pandemics typically last for several months to 1-2 years and have even longer lasting effects on the economy and communities.
As described by the World Health Organization (WHO), the Pandemic Intervals Framework is a six-phased approach to defining the progression of a pandemic. This framework is used to guide pandemic planning and provides recommendations for risk assessment, decision making, and action. These intervals provide a common method to describe pandemic activity which can inform public health actions. The duration of each pandemic interval might vary depending on the characteristics of the virus and the public health response.
The six-phase approach was designed for the easy incorporation of recommendations into existing national and local preparedness and response plans. Phases 1 through 3 correlate with preparedness in the pre-pandemic interval, including capacity development and response planning activities, while Phases 4 through 6 signal the need for response and mitigation efforts during the pandemic interval. Phase 6 was reached in the County during the 2020 COVID outbreak.
Pre-Pandemic Interval
Phase 1 is the natural state in which influenza viruses circulate continuously among animals but do not affect humans.
Phase 2 involves cases of animal influenza that have circulated among domesticated or wild animals and have caused specific cases of infection among humans.
Phase 3 represents the mutation of the animal influenza virus in humans so that it can be transmitted to other humans under certain circumstances (usually very close contact between individuals). At this point, small clusters of infection have occurred.
Pandemic Interval
Phase 4 involves community-wide outbreaks as the virus continues to mutate and become more easily transmitted between people (for example, transmission through the air).
Phase 5 represents human-to-human transmission of the virus in at least two countries.
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Phase 6 is the pandemic phase, characterized by community-level influenza outbreaks.
Past Occurrences
Ɣ Since the early 1900s, five lethal pandemics have swept the globe:
Ɣ 1918-1919 Spanish Flu: The Spanish Flu was the most severe pandemic in recent history. The number of deaths was estimated to be 50-100 million worldwide and 675,000 in the United States. Its primary victims were mostly young, healthy adults. At one point, more than 10 percent of the American workforce was bedridden.
Ɣ 1957-1958 Asian Flu: The 1957 Asian Flu pandemic killed 1 to 2 million people worldwide, including about 70,000 people in the United States, mostly the elderly and chronically ill. Fortunately, the virus was quickly identified, and vaccine production began in May 1957.
Ɣ 1968-1969 H3N2 Hong Kong Flu: The 1968 Hong Kong Flu pandemic killed 34,000 Americans.
Again, the elderly were more severely affected. This pandemic peaked during school holidays in December, limiting student-related infections, which may have kept the number of infections down.
Also, people infected by the Asian Flu ten years earlier may have gained some resistance to the new virus.
Ɣ 2009-2010 H1N1 Swine Flu: This influenza pandemic emerged from Mexico in early 2009 and was declared a public health emergency in the U.S. on April 26. By June, approximately 18,000 cases had been reported in the U.S. and the virus had spread to 74 countries. Most cases were fairly mild, with symptoms similar to the seasonal flu, but there were cases of severe disease requiring hospitalization and a number of deaths. The CDC estimates that 43-89 million people were infected worldwide, with an estimated 8,870 to 18,300 H1N1 related deaths, including 12,469 deaths in the United States.
Ɣ 2020-Ongoing COVID-19: The COVID-19 or novel coronavirus outbreak began in December 2019 and was declared a pandemic in March of 2020. As of April 11, 2021, over 136 million cases and approximately 2.9 million deaths have been reported globally, according to the WHO. Within the U.S. as of April 11, 2021, over 30 million cases and over 555,000 deaths have been reported. Merced County has reported 31,009 cases so far resulting in 448 deaths. COVID-19 vaccines are currently being administered and thus far almost 15% of Merced County adults (18 years or older) have been fully vaccinated. It will take several months for the entire population to receive a vaccine and achieve herd immunity; additionally, due to the uncertainty in the transmission of several variants of the SARS-CoV-2ǀŝƌƵƐ͕ƚŚĞƉĂŶĚĞŵŝĐŝƐĞdžƉĞĐƚĞĚƚŽĐŽŶƚŝŶƵĞƚŚƌŽƵŐŚϮϬϮϭ͘ Probability of Future Occurrences
Even before the COVID-19 pandemic began, most public health experts considered another major pandemic to be inevitable. However, there is no definite way to predict when the next pandemic might occur. Some indicators will be present, but not every new virus turns into a pandemic. Based on the five pandemics that have affected the United States in roughly the last 100 years, a pandemic occurs on average roughly every 20 years.
Climate Change Considerations
Additional research is needed to determine the effects of climate change on the frequency and duration of epidemics and pandemics. Climate change may influence vector-borne disease transmission, although the direction of the effects (increased or decreased incidence) will be location- and disease-specific. The intensity and extent of certain diseases is projected to increase. According to the WHO, there has been research development into the linkages between climate and infectious disease transmission that examine the associations between climate variability and infectious disease occurrence, early indicators of emerging infectious disease impacts of climate change and using predictive models to estimate the future burden of infectious disease under different climate change scenarios (WHO 2003). In summary, future DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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risks associated with climate change are difficult to predict, but changes in infectious disease transmission patterns are likely consequences of climate change. Climate change can impact when and where pathogens appear, particularly related to temperature and rainfall patterns.
Ongoing efforts to reduce greenhouse gas emissions, building climate resiliency, and creating robust public health campaigns to prevent or prepare for possible increased vector-borne diseases may help to reduce the impacts of climate change on pandemics.
Vulnerability Assessment
Preparing for, responding to, and recovering from a pandemic requires a strategy that includes a holistic suite of public health activities designed to lessen the impact on morbidity and mortality. These activities include education, vaccination, prophylaxis, isolation/quarantine, a robust contact tracing program, and the closure of public facilities. In addition, clear, concise communication with the public and with other agencies remains a critical component, as does the ability of the involved agencies to achieve collaboration and coordination. By their very nature, most pandemics, once started, will not be stopped until they have run their course. This course can be shortened and weakened by a number of factors, with vaccination being the most effective method for protecting the population. Pandemic plans describe strategies of preparedness, response, and recovery to attempt to decrease illnesses and deaths during the pandemic period to manageable levels (i.e., that do not overwhelm the critical infrastructures of the State), and to promote community resiliency and rapid recovery.
General Property
For the most part, property itself is not generally impacted by a human disease epidemic or pandemic.
However, as concerns about contamination increase, property may be quarantined or destroyed as a precaution against spreading illness. Additionally, traditional sheltering facilities including homeless shelters or temporary facilities set up to support displaced persons due to an evacuation or other reason due to a simultaneous disaster occurring cannot be done in a congregate setting. This requires additional planning considerations or use of facilities that allow for non-congregate shelter settings, which may require an approval of a request to FEMA for non-congregate sheltering, and may have an increased cost (such as the use of individual hotel rooms) as opposed to traditional congregate sheltering facilities.
People
Pandemics have the ability to affect large segments of the population for long periods of time. The number of hospitalizations and deaths will depend on the virulence of the virus. Risk groups cannot be predicted with certainty; the elderly, people with underlying medical conditions, and young children are usually at higher risk due to their higher exposure rates from schools, but as discussed above this is not always true for all infectious agents. People without health coverage or access to good medical care are also likely to be more adversely affected. Mental health of the public could also be impacted depending on the length of the event and public health guidance on prevention.
As previously described in the Past Events section above, the COVID-19 pandemic has resulted in over 555,000 deaths in the U.S. alone (448 in Merced County). In addition to the direct impacts, the pandemic has completely disrupted life for many people. Most large gatherings have had to be cancelled, and many schools have closed. Sheltering in place and social distancing have been highly encouraged and, in some places, mandated, leaving some individuals isolated for months.
Social Vulnerability
Preparing for, responding to, and recovering from a pandemic requires a strategy that includes a holistic suite of public health activities designed to lessen the impact on morbidity and mortality. These activities include education, vaccination, prophylaxis, isolation/quarantine, a robust contact tracing program, and DĞƌĐĞĚŽƵŶƚLJDƵůƚŝͲ:ƵƌŝƐĚŝĐƚŝŽŶĂů,ĂnjĂƌĚDŝƚŝŐĂƚŝŽŶWůĂŶ ,ĂnjĂƌĚ/ĚĞŶƚŝĨŝĐĂƚŝŽŶĂŶĚZŝƐŬƐƐĞƐƐŵĞŶƚ
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the closure of public facilities. In addition, clear, concise communication with the public and with other agencies remains a critical component, as does the ability of the involved agencies to achieve collaboration and coordination. By their very nature, most pandemics, once started, will not be stopped until they have run their course. This course can be shortened and weakened by a number of factors, with vaccination being the most effective method for protecting the population. Pandemic plans describe strategies of preparedness, response, and recovery to attempt to decrease illnesses and deaths during the pandemic period to manageable levels (i.e., that do not overwhelm the critical infrastructures of the State), and to promote community resiliency and rapid recovery.
Critical Facilities
In the event of a pandemic, especially one with high transmission rates and mortality rates such as COVID- 19, community lifelines, such as healthcare facilities, like hospitals will be heavily affected and may be overwhelmed due to limited number of beds, doctor and medical staff, laboratory testing capacity, and possible personal protective equipment (PPE) shortages. Indirect impacts can also result in these facilities being temporarily offline due to testing or other precautionary monitoring and downed systems. Further, outbreaks in small cities and counties may cause medical facilities to reach capacity very quickly. Other critical facilities and infrastructure are not directly affected by a pandemic but may have difficulty maintaining operations and maintenance activities due to a significantly decreased workforce. Schools may also be forced to close.
Economy
Pandemics can have extensive economic impacts, as evidenced by the COVID-19 pandemic and associated restrictions on social gatherings. Social distancing requirements have affected nearly every segment of the local and national economy, most notably the restaurant and hospitality industries.
Additionally, tourism may be impacted in affected areas. As a result, the unemployment rate can increase, which also occurred in 2020 due to the COVID-19 pandemic. Other economic impacts including varying disruptions in the food supply chains and other essential medical services.
Historic, Cultural and Natural Resources
Impacts to these resources are typically minimal. However, reduced tourism during outbreaks could lead to additional economic impacts.
Future Development
Population growth and development contribute to pandemic exposure. Future development in and around Merced County has the potential to change how infectious diseases spread through the community and impact human health in both the short and long-term. New development may increase the number of people and facilities exposed to public health hazards and greater population concentrations (often found in special needs facilities, businesses, and school campuses) put more people at risk. During a disease outbreak those in the immediate isolation area would have little to no warning, whereas, the population further away in the dispersion path may have some time to prepare and mitigate against disease depending on the hazard, its transmission, and public notification.
Risk Summary
Ɣ Pandemics affecting the U.S. occur roughly once every 20 years but cannot be reliably predicted.
Ɣ Effects on people will vary, but a significant portion of the population could become ill, and may need to be hospitalized
Ɣ Effects on property are typically minimal, although quarantines could result in short-term closures.
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Ɣ Community lifelines, such as healthcare facilities, like hospitals will be impacted and may be overwhelmed and have difficulty maintaining operations due to bed availability, medical staffing shortages, and lack of PPE and other supplies.
Ɣ Lost productivity due to illness and potential business closures could potentially have severe economic impacts, such as increased unemployment rates in the County. Social distancing requirements and fear of public gatherings could also significantly reduce in person commerce.
Ɣ The hazard is considered high significance across all participating jurisdictions.
Ɣ Ongoing mitigation activities should focus on disease prevention, especially during flu season. This includes, but is not limited to, pre-season community outreach campaigns to educate the public about risks and available support; establishing convenient vaccination centers; reaching out to vulnerable populations and care givers; and issuing advisories and warnings.
Table 4-81 Hazard Risk Summary – Pandemics/Epidemics
Jurisdiction Geographic Area
Probability of
Future
Occurrence
Magnitude/
Severity
Overall
Significance
Merced County Extensive Occasional Catastrophic High
City of Atwater Extensive Occasional Catastrophic High
City of Dos Palos Extensive Occasional Critical Medium
City of Gustine Extensive Occasional Catastrophic High
City of Livingston Extensive Occasional Catastrophic High City of Los Banos Extensive Occasional Catastrophic High City of Merced Extensive Occasional Critical Medium
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5 MITIGATION STRATEGY
Requirement §201.6(c)(3):
[The plan shall include the following:] A mitigation strategy that provides the jurisdiction’s blueprint for reducing the potential losses identified in the risk assessment, based on existing authorities, policies, programs, and resources, and its ability to expand on and improve these existing tools.
This section describes the mitigation strategy process and mitigation action plan for the Merced County MJHMP. It describes how the County and participating jurisdictions met the requirements for the following from the 10-step planning process:
Ɣ Planning Step 6: Set Goals
Ɣ Planning Step 7: Review Possible Activities
Ɣ Planning Step 8: Draft an Action Plan
The mitigation strategy reflects the results of the collaborative work of the HMPT. Subsection 5.3 Mitigation Action Plan is based on the updated planning process, risk assessment, capability assessment, goal setting, and the identification of mitigation actions. Taking all of these into consideration, the HMPT developed the following overall mitigation strategy:
Ɣ Communicate the hazard information collected and analyzed through this planning process as well as HMPT success stories so that the community better understands what can happen where and what they themselves can do to be better prepared.
Ɣ Implement the action plan recommendations of this plan.
Ɣ Use existing rules, regulations, policies, and procedures already in existence. Given the flood hazard in the planning area, an emphasis should be placed on continued compliance with the NFIP.
Ɣ Monitor multi-objective management opportunities so that funding opportunities may be shared and packaged, and broader constituent support may be garnered.
5.1 Mitigation Goals and Objectives
§201.6(c)(3)(i)
[The hazard mitigation strategy shall include a] description of mitigation goals to reduce or avoid long- term vulnerabilities to the identified hazards.
Up to this point in the planning process, the HMPT has organized resources, assessed hazards and risks, and documented mitigation capabilities. The resulting goals, objectives, and mitigation actions were developed based on these tasks. The HMPT held a series of meetings and exercises designed to achieve a collaborative, updated mitigation strategy as described further throughout this section.
Over a series of meetings during the 2021 update process the HMPT reviewed the results of the hazard identification, vulnerability assessment, and capability assessment update. This analysis of the risk assessment identified areas where improvements could be made and provided the framework for the HMPT to update planning goals and objectives and the ultimate mitigation strategy for the Merced County planning area.
Goals were defined for the purpose of this mitigation plan as broad-based public policy statements that:
Ɣ Represent basic desires of the community;
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Ɣ Encompass all aspects of community, public and private; Ɣ Are nonspecific, in that they refer to the quality (not the quantity) of the outcome; Ɣ Are future-oriented, in that they are achievable in the future; and Ɣ Are time-independent, in that they are not scheduled events.
Goals are stated without regard to implementation. Implementation cost, schedule, and means are not considered. Goals are defined before considering how to accomplish them so that they are not dependent on the means of achievement. Goal statements form the basis for objectives and actions that will be used as means to achieve the goals. Objectives define strategies to attain the goals and are more specific and measurable.
During the 2021 plan update process, HMPT members review the existing goals and objectives as well the goals and objectives from 2018 State of California Hazard Mitigation Plan and from the 2014 City of Merced LHMP. Through a brainstorming process at their third meeting, the HMPT identified a variety of possible goals and then came to a consensus on seven main sets of goals and objectives. Goals 4, 5 and 6 are new to 2021 plan update; other revisions included removing the word “natural” from the goals to be more inclusive to all hazards. Following the development of goals, the HMPT also identified specific objectives to achieve each goal. Goals and objectives are listed below, but are not prioritized:
Ɣ Goal 1: Reduce the potential for loss of life and injury from hazards - Assist vulnerable populations from the impacts of severe weather by organizing a mechanism for outreach.
- Educate property owners by increasing wildfire awareness and measures for reducing risks - Identify opportunities to reduce losses associated with High Hazard potential dams Ɣ Goal 2: Minimize or reduce damage to property.
- Minimize growth and development in hazard areas
- Adopt and enforce building codes
- Educate property owners by increasing wildfire awareness and measures for reducing risks - Identify opportunities to reduce losses associated with High Hazard potential dams Ɣ Goal 3: Build resiliency and redundancy to maintain essential services, lifelines, facilities, and infrastructure.
- Ensure protection and enhancement of key emergency access routes - Protect critical facilities and infrastructure to minimize loss of critical services - Seek funding sources and partners for future mitigation activities - Improve organizational capabilities to address health and safety issues in mitigation and response
Ɣ Goal 4: Minimize impacts of hazards to agriculture and the economies of communities. - Encourage water conservation measures among urban, rural, and agricultural users - Increase water storage to mitigate flooding and drought - Strengthen disaster resistance and resiliency of major employers - Develop plans for post-disaster recovery
Ɣ Goal 5: Protect and leverage natural and beneficial mitigation functions of the environment. - Encourage the use of drought tolerant or xeriscaping practices into landscape ordinances - Incorporat e defensible space in landscaping of new and existing development Ɣ Goal 6: Promote hazard mitigation as an integrated policy.
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- Promote hazard mitigation as integrated policy among communities in the county and with the region and state
- Incorporate flood mitigation into local planning by adoption of post-disaster recovery ordinance based on a plan to regulate repair activity
- Continue to improve enforcement of existing standards and regulations Ɣ Goal 7: Increase public awareness of hazards.
- Promote education and awareness about natural hazards risk, mitigation, and preparedness to citizens, public agencies, elected officials, nonprofit organizations, and businesses - Develop water saving education program
- Increase communication regarding hazard mitigation among communities in the county
5.1.1 Continued Compliance with the National Flood Insurance Program (NFIP) The NFIP makes federally backed flood insurance available to homeowners, renters, and business owners in participating communities. For most participating communities, FEMA has prepared a detailed Flood Insurance Study. The study presents water surface elevations for floods of various magnitudes, including the 1% annual chance flood (or 100-year flood) and the 0.2% annual chance flood (or 500-year flood).
Base flood elevations and the boundaries of the 100- and 500-year floodplains are shown on Flood Insurance Rate Maps (FIRM), which are the principal tools for identifying the extent and location of the riverine flood hazard. FIRMs are the most detailed and consistent data source available, and for many communities they represent the minimum area of oversight under their floodplain management program.
Participants in the NFIP must, at a minimum, regulate development in floodplain areas in accordance with NFIP criteria. Before issuing a permit to build in a floodplain, participating jurisdictions must ensure that three criteria are met:
Ɣ New buildings and those undergoing substantial improvements must, at a minimum, be elevated to protect against damage by the 100-year flood.
Ɣ New floodplain development must not aggravate existing flood problems or increase damage to other properties.
Ɣ New floodplain development must exercise a reasonable and prudent effort to reduce its adverse impacts on threatened salmonid species.
Merced County, Atwater, Dos Palos, Livingston, Los Banos and Merced participate in the NFIP. Structures permitted or built in the county before 1979 when the County, Atwater and Merced joined the NFIP (1978 for Dos Palos and Livingston and 1998 for Los Banos) are called “pre-FIRM” structures, and structures built afterwards are called “post-FIRM.” Post-FIRM structures built in compliance with the floodplain regulations are mitigated to withstand floods up through the 100-year event. The insurance rate is different for the two types of structures, as pre-FIRM structures are at higher risk of flooding. The effective date for the current countywide FIRM is December 2, 2008. The County and participating jurisdictions are currently in good standing with the provisions of the NFIP. Compliance is monitored by FEMA regional staff. Maintaining compliance with the NFIP is an important component of flood mitigation and risk reduction.
The City of Gustine is not a participant in the NFIP and has been sanctioned since December 2, 2009. This means that residents are not able to obtain flood insurance from the NFIP. The City has minimal flood risk and the effective FEMA flood hazard mapping does not show any Special Flood Hazard Area (SFHA) or 1% annual chance flooding within city limits. This has been the reason for not joining the NFIP, but as part of this plan update the City will revisit the cost and benefit of joining, including working with CA DWR and FEMA to understand the implications of the sanction designation. Refer to the mitigation strategy in Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
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Section 5 for more information on specific mitigation actions related to addressing the sanction designation.
Given the flood hazard and risk in the planning area and recognizing the importance of the NFIP in mitigating flood losses, an emphasis is placed on continued compliance with the NFIP by Merced County and all NFIP participating jurisdictions including Atwater, Dos Palos, Livingston, Los Banos and Merced. As NFIP participants, these communities have and will continue to make every effort to remain in good standing with NFIP. This includes continuing to comply with the NFIP’s requirements for adopting official FEMA floodplain maps and maintaining, enforcing, and updating local floodplain regulations.
5.2 Identification and Analysis of Mitigation Actions
§201.6(c)(3)(ii):
[The hazard mitigation strategy shall include a] section that identifies and analyzes a comprehensive range of specific mitigation actions and projects being considered to reduce the effects of each hazard, with particular emphasis on new and existing buildings and infrastructure. All plans approved by FEMA after October 1, 2008, must also address the jurisdiction’s participation in the NFIP, and continued compliance with NFIP requirements, as appropriate.
In order to identify and select mitigation measures to support the mitigation goals, each hazard identified in Section 4: Hazard Identification and Risk Assessment was evaluated. The HMPT analyzed a comprehensive set of viable mitigation alternatives for both new and existing buildings and infrastructure that would support identified goals and objectives. Each HMPT member was provided with the following list of categories of mitigation measures, which originate from the NFIP CRS:
Ɣ Prevention: Administrative or regulatory actions or processes that influence the way land and buildings are developed and built.
Ɣ Property protection: Actions that involve the modification of existing buildings or structures to protect them from a hazard or remove them from the hazard area.
Ɣ Structural: Actions that involve the construction of structures to reduce the impact of a hazard.
Ɣ Natural resource protection: Actions that, in addition to minimizing hazard losses, also preserve or restore the functions of natural systems.
Ɣ Emergency services: Actions that protect people and property during and immediately after a disaster or hazard event.
Ɣ Public information/education and awareness: Actions to inform and educate citizens, elected officials, and property owners about the hazards and potential ways to mitigate them.
At the mitigation strategy meeting the HMPT was also provided with a matrix showing examples of potential mitigation action alternatives for each of the above categories, for each of the identified hazards.
The HMPT was also provided a handout that explains the categories and provided further examples.
Another reference document titled “Mitigation Ideas” developed by FEMA in 2013 and FEMA’s 2020 “Mitigation Action Portfolio” were distributed to the HMPT via an online link. These document lists the common alternatives for mitigation by hazard and actions funded by FEMA. The HMPT was also instructed to consider both future and existing buildings in considering possible mitigation actions. This reference provides four categories of mitigation actions that were discussed at the HMPT meeting in addition to the NFIP/CRS categories. These include:
Ɣ Plans and Regulations
Ɣ Structure and Infrastructure Projects
Ɣ Education and Awareness
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Ɣ Natural systems protection
Other alternatives discussed in the webinar include the four ‘A’s’ of mitigation:
Ɣ Alter the physical nature of the hazard
- Such as wildfire defensible space and fuels treatments, snow fences etc.
Ɣ Avert the hazard away from people, buildings, and infrastructure - Can include engineered solutions, drainage, and channel improvements, floodproofing, fuel breaks
Ɣ Adapt to the hazard
- Through land use planning, building codes and design standards, warning systems etc.
Ɣ Avoid the hazard
- Natural systems protection, open space, acquisition, or relocation of properties out of hazardous areas
As part of the review of mitigation options long-term climate change adaptation strategies were also discussed. HMPT members were encouraged to incorporate climate change adaptation measures into the mitigation strategy of their respective jurisdictions utilizing resources and guidance available on the Cal- Adapt website.
To facilitate the brainstorming process, the HMPT referred to a matrix of typical mitigation alternatives organized by CRS category for the hazards identified in the plan, in addition to a handout that explains the categories and provided examples. These materials are included in Appendix B. HMPT members were encouraged to develop mitigation alternatives that would protect future, as well as existing, development from hazards per the DMA 2000 regulations. A facilitated discussion then took place to examine the existing actions in the 2014 plan and analyze the other possible mitigation alternatives. With an understanding of the alternatives, a brainstorming session was conducted to generate a list of preferred mitigation actions. The result was new and updated project ideas with the intent of meeting the identified goals and mitigating identified hazards.
These new and updated project actions were expanded on during a fourth HMPT meeting scheduled to focus on the refinement and prioritization of new mitigation activities. During the fourth HMPT meeting, Wood facilitated a discussion on the draft MJHMP and any remaining information or mitigation gaps that needed to be addressed. During the fourth HMPT meeting the group also discussed opportunities for plan integration and reviewed the plan implementation and maintenance procedures.
5.2.1 Prioritization Process
Once the mitigation actions were identified, the HMPT was provided with several decision making tools, including FEMA’s recommended prioritization criteria, STAPLEE, to assist in deciding why one recommended action might be more important, more effective, or more likely to be implemented than another. STAPLEE stands for the following:
Ɣ Social: Does the measure treat people fairly? (e.g., different groups, different generations) Does it consider social equity, disadvantaged communities, or vulnerable populations? Ɣ Technical: Will it work? (Is the action technically feasible? Does it solve the problem?) Ɣ Administrative: Is there capacity to implement and manage the project? (adequate staffing, funding, and other capabilities to implement the project?)
Ɣ Political: Who are the stakeholders? Did they get to participate? Will there be adequate political and public support for the project?
Ɣ Legal: Does the jurisdiction have the legal authority to implement the action? Is it legal? Are there liability implications?
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-6
Ɣ Economic: Is the action cost-beneficial? Is there funding available? Will the action contribute to the local economy?
Ɣ Environmental: Does the action comply with environmental regulations? Will there be negative environmental consequences from the action?
In accordance with the Disaster Mitigation Act requirements, an emphasis was placed on the importance of a benefit-cost analysis in determining action priority. Other criteria used to assist in evaluating the benefit-cost of a mitigation action included:
Ɣ Does the action address hazards or areas with the highest risk? Ɣ Does the action protect lives?
Ɣ Does the action protect infrastructure, community assets or critical facilities? Ɣ Does the action meet multiple objectives (Multiple Objective Management)? Ɣ What will the action cost?
Ɣ What is the timing of available funding?
The mitigation categories, multi-hazard actions, and criteria are included in Appendix D: Mitigation Categories and Alternatives.
At the mitigation strategy webinar, the HMPT reviewed and discussed the STAPLEE considerations to determine which of the identified actions were most likely to be implemented and effective. Prioritization of previous mitigation actions identified in the 2014 HMP that were carried forward in the updated plan were revisited during the fourth HMPT meeting. New actions identified in 2021 also were prioritized based on the group discussion. With the STAPLEE criteria in mind, HMPT participants were given a set of three green sticky dot stickers. The team was asked to use the dots to prioritize projects with the above criteria in mind, essentially voting on the projects. The projects with the most dots became the higher priority projects. This process provided both consensus and priority for the recommendations.
The process of identification and analysis of mitigation alternatives allowed the HMPT to come to consensus and to collectively prioritize recommended mitigation actions. During the voting process, emphasis was placed on the importance of a benefit-cost review in determining project priority; however, this was not a quantitative analysis. Benefit-cost was considered in greater detail in the development of the Mitigation Action Plan. For example, parameters were established for assigning subjective ratings (high, medium, low) to the benefits and costs of each mitigation action. Specifically, each action developed for this plan contains a description of the problem and proposed project, the entity with primary responsibility for implementation, any other alternatives considered, a cost estimate, expected project benefits, potential funding sources, and a schedule for implementation. Development of these project details for each action led to the determination of an overall high, medium, or low priority for each action.
Recognizing the limitations in prioritizing actions from multiple departments and the regulatory requirement to prioritize by benefit-cost to ensure cost-effectiveness, the HMPT decided to pursue mitigation action strategy development and implementation according to the nature and extent of damages, the level of protection and benefits each action provides, political support, project cost, available funding, and jurisdiction and department priority. This process guided the development of a prioritized action plan for Merced County and the participating jurisdictions.
Cost-effectiveness will be considered in greater detail through a formal benefit-cost analysis when seeking FEMA mitigation grant eligibility and funding (e.g. HMGP, PDM grant programs) for eligible actions associated with this plan.
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-7
5.3 Mitigation Strategy Action Plan
§201.6(c)(3)(iii)
[The hazard mitigation strategy shall include an] action plan, describing how the action identified in paragraph (c)(3)(ii) of this section will be prioritized, implemented, and administered by the local jurisdiction. Prioritization shall include a special emphasis on the extent to which benefits are maximized according to a cost benefit review of the proposed projects and their associated costs. §201.6(c)(3)(iv)
For multi-jurisdictional plans, there must be identifiable action items specific to the jurisdiction requesting FEMA approval or credit of the plan.
This action plan was developed to present the recommendations developed by the HMPT for how the Merced County planning area can reduce the vulnerability of people, property, infrastructure, and natural and cultural resources to future disaster losses. Over time the implementation of these projects will be tracked as a measure of demonstrated progress on meeting the plan’s goals.
5.3.1 Progress on Previous Mitigation Actions
A review of 2014 mitigation actions progress reports indicates that Merced County and the participating jurisdictions have been successful in implementing actions identified in the 2014 LHMP Mitigation Strategy, thus, working diligently towards meeting the 2014 plan goals. The 2014 mitigation strategy contained 36 separate mitigation actions. As of September 2021, two of these actions have been completed, three deleted and 39 actions are continuing. The table below summarizes progress implementing mitigation actions by jurisdiction. The total continuing actions column summarizes the actions from 2014 that are either still in progress, have annual implementation, or are continuing but not completed. The new actions in 2021 summarizes the number of actions that were identified during the 2021 plan update process.
Table 5-1 Mitigation Action Progress Summary by Jurisdiction Jurisdiction Completed Deleted Continue
In Progress
Continue
Not
Started
Total
Continuing
Actions
New
Actions
in 2021
Grand
Total
Actions
Atwater 0 2 2 4 6 4 10
Dos Palos NA NA NA NA NA 2 2
Gustine NA NA NA NA NA 4 4
Livingston 0 0 2 6 8 1 9
Los Banos 0 1 7 0 7 8 15
Merced 0 0 2 8 10 1 11
Unincorporated 2 0 7 1 8 12 20
Grand Total 2 3 20 19 39 31 70
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-8
Table 5-2 indicates the details for each of the 2014 mitigation action items that have been completed or deleted.
Table 5-2 Completed and Dele ted Mitigation Actions
ID Corresponding
Hazard(s) Mitigation Action Lead
Agency Goals Priority Action Status Notes
Merced County
10 Drought Promote Water Conservation
Program
OES / CEO's
Office 1,2,3 High
Completed. This
program is in place and
implemented regularly
due to continuing
challenges with
drought.
11 Wildfire Implement and Monitor Weed
Abatement Program County Fire 1,2,3 High Completed.
City of Atwater
7 Flood
Flood Insurance Promotion, CRS
Program
Implementation/Participation
Planning
Department 1,2,3 High
Deleted. The City does
not have enough flood
insurance policies to
justify joining CRS.
9 Drought Promote Water Conservation
Program
Public
Works 1,2,3 High
Deleted. This program is
in place and
implemented regularly
due to continuing
challenges with
drought.
City of Los Banos
7 Flooding
Flood Insurance Promotion, CRS
Program Implementation/
Participation.
Planning
Department 1,2,3 High
Deleted. The City does
not have enough flood
insurance policies to
justify joining CRS.
5.3.2 Updated Action Plan
The results of the project identification and prioritization exercise from meetings 3 and 4 is summarized in Table 5-3. These projects detail specific actions for reducing future hazard-related losses within Merced County. The projects are organized by jurisdictions and include notes about the department and partners necessary to implement the project. Table 5-3 provides more details on the mitigation actions, including the mitigation action description estimated cost, potential funding sources, timeline, indication of the goal(s) that the projects primarily align with and are marked with their relative level of priority high, medium, and low. The following table also provides status/implementation notes that describe progress made on the actions so far, using the following categories, and, where applicable, notes if there were changes in the priority level from the previous plan:
Ɣ Continue - In Progress: work has begun on the project and is ongoing.
Ɣ Continue - Not completed: little or no work has been done on the project to date and the HMPT agreed to carry over the action into the updated plan.
Ɣ New in 2021: The action is new to this plan update; little to no work has been completed.
Many of these mitigation actions are intended to reduce impacts to existing development. Those that protect future development from hazards, as required per the DMA 2000 regulations, are indicated by an asterisk ‘*’ in the action identification number. These actions include those that promote wise Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-9
development and hazard avoidance, such as building code, mapping, and zoning improvements, and continued enforcement of floodplain development regulations.
Table 5-4 provides a summary of the individual mitigation actions by jurisdiction specific to the municipalities that participated in the 2021 plan update. The timeline for implementation for each hazard mitigation action is organized into the following timeframes: ongoing, annual implementation, 1-2 years (short-term), 2-3 years (medium-term), or 3-5 years (long-term). Together with the County actions the tables provide an overview of all the mitigation actions proposed. More details can be found in the respective jurisdictional annexes.
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-10
Table 5-3 Merced County Mitigation Actions
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
1 1,7
NA
Multi-
Hazard:
Dam
Incident,
Earthquake
Flooding
Severe
Weather
Wildfire
Countywide Public Education
Program – A natural hazards
education and awareness program in
Merced County would be a valuable
tool for sharing information with
residents. Implementation ideas
include sharing information online
and conducting workshops. The
county will partner with special
districts, the cities and other entities
to provide awareness and education
on hazards and steps to mitigate.
OES / CEO's
Office
$100,000
Federal
Grants
High Ongoing
Continue In Progress. The 2014
HMP included four of the six
incorporated cities. The 2021
plan included all 6-cities. This
program will expand as a joint
effort between all 6-cities.
2* 1,2,4,6
NA
Multi-
Hazard:
Earthquake,
Flooding,
Severe
Weather,
Wildfire
Integrate Local Hazard Mitigation
Plan into Safety Element of General
Plan. Recognizing the potential
duplication of effort over evaluation
of the same issues, efforts to update
the Health and Safety Element will be
conducted in coordination with the
multi-hazard mitigation plan and to
also ensure AB 2140 Compliance.
Integration and coordination of both
plans provides General Plan policy
direction for development activity.
Potential loss reductions in the
$1000s as any new development
within the county will be considered
Community
Developme
nt Agency
$5,000
General
Fund
Medium
Next
General
Plan
review
cycle
Continue In Progress. The
updated 2021 plan will be
incorporated by reference into
the Safety Element as part of
the MJHMP adoption process.
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-11
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
within the context of the county’s
Health and Safety Element.
3 1,7
NA Earthquake
Non-structural Earthquake Mitigation
Outreach. Existing structures can be
retrofitted to better withstand
damage from seismic events.
Outreach will include educating home
and business owners about structural
and non-structural retrofit techniques
and how to seismically strengthen
their homes and businesses. Specific
techniques include secure furnishings,
storage cabinets and utilities to
prevent injuries and damages, such as
anchoring, installing lathes, using
flexible connections on gas and water
lines, and bracing propane tanks and
water heaters.
Environmen
tal Health
$100,000
Federal
Grants
Medium Ongoing
Continue In Progress. An
earthquake safety flyer was
created and posted on Public
Health social media and the
Division of Environmental
Health's website.
4 1,2
NA Earthquake
Countywide Inventory of Historic
Unreinforced Masonry Buildings –
Use GIS a to map and track URMs
Countywide. An accurate inventory of
URM Buildings with appropriate
tracking will lessen time during the
recovery after an EQ.
Building
Department
$100,000
Federal
Grants
Medium 1-2 years
Continue – In Progress. Not
Completed. The County
Building Department has not
tracked or kept records of URM
Buildings in the unincorporated
portion of Merced County.
5 1,2,6
Food,
Water,
Shelter
Earthquake
Periodically review building codes for
updates and enhancements and
ensure necessary capabilities for
enforcement.
Building
Department
Staff time
Dept.
Budget
Medium
Annual
impleme
ntation
Continue – Not Started. The
enforcement of building codes
is standard regulatory practice.
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-12
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
6 1,2,4
Safety
and
Security
Flood
Develop a Hazard Specific Flood
Annex for all jurisdictions with focus
on flood hazard areas as described in
the Risk Assessment. The annex will
address the associated risks of
flooding, current and past mitigation
efforts specific to the streams and
localized flood areas in the county.
OES, Public
Works
$90,000
State and
Federal
Grants
High 1-2 years
Continue In Progress. The
County EOP captures the county
in its entirety. County OES is
working to include all six cities.
7 1,2,7
Safety
and
Security
Flood
Flood Insurance Promotion Program
Implementation/Participation. County
staff will promote benefits of flood
insurance
OES,
Planning
Department
Staff Time
Dept.
Budget
High
Annual
Impleme
ntation
Continue In Progress.
8 1,2,3
Safety
and
Security
Flood
Identify and evaluate effectiveness of
alternative detention basin flood
control projects that will reduce flood
flows in Black Rascal Creek at the
diversion.
Public
Works
$500,000-
4M.
State and
Federal
Grants
High 1-2 years
Continue In Progress. The
County has identified a
preferred alternative as of 2021
but construction has not yet
begun.
9 1,7
NA
Severe
Weather:
Wind,
Extreme
Temps.,
Tornadoes,
Dense Fog
Winter Weather Preparedness
Campaign. This project would add to
and enhance the existing, campaigns
that share information on Severe
Weather Hazards: Fog, Freeze,
Location of Warming Centers, Heat
Related Illness, All Hazards
Preparedness information, etc.; The
county will work with special districts,
the cities and other entities.
OES/CEO’s
Office
$100,000
Federal
Grants
High
Annual
Impleme
ntation
Continue In Progress. This
program is expanded each year
utilizing various outreach
strategies.
10 3
Commun
ications
Cyber
Attack
Cyber Security. Establish a risk
management program to identify the
risks, understand their likelihood and
OES,
Jurisdiction
s
$500,000-
$2,500,000
Grants,
Medium 2-3 years New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-13
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
impact. Once identified place security
controls that mitigate the risks to a
level considered acceptable. The risk
management program will also
include ongoing evaluation and
assessment of cyber security risks and
controls throughout the life cycle of
the software. Ideas for
implementation: Define the system.
Identify cyber assets and their
classification. Identify the electronic
security perimeter protecting these
assets. Conduct vulnerability
assessment: Identify threats. Identify
vulnerabilities. Identify security risks
along with their impact and
likelihood. Assess the effectiveness of
existing security controls in mitigating
the risks. Recommend new security
controls or changes to existing
security controls to mitigate the
severity of the risks to a level
acceptable to the organization.
Continuously monitor the
effectiveness of security controls.
Periodically repeat this process to
account for system changes and
changes in the threat landscape.
General
Fund
11 4
NA Drought Drought Plan. Develop drought plans
that outline proactive strategies that OES $500,000-
$10,000,00 High 3-5 years New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-14
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
can be implemented before, during,
and after drought to increase societal
and environmental resiliency and
enhance drought response and
recovery capabilities Investigate
drought monitoring, risk, and
management options. Include water
conservation projects that seek to
reduce the nonessential use of water
to conserve county water supplies.
Conservation projects include
establishing mandatory water
restrictions within Merced County to
discourage waste and incorporate
treatment of recycled water for
potable consumption.
0 Grants,
General
Fund
12 4
Food,
Water,
Shelter
Drought,
Flood
Groundwater Recharge and
Stormwater Detention Pilot Project. A
pilot project is being conducted by
Eastside Water District on Merced
County property in 2021 that
included installation of three dry wells
at the Mustang Creek Flood
Detention Basin for groundwater
recharge. This project will also assist
in mitigating flooding from
stormwater scenarios. When dry wells
are installed, they will prevent erosion
and localized flooding while also
OES,
County
Water
Resources,
Eastside
Water
District
$500,000-
$3,000,000
Grants,
General
Fund
High 2-3 years New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-15
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
allowing collection and control of
stormwater runoff.
13 1,3,6
NA
Multi-
Hazard:
Dam
Incidents,
Earthquake,
HazMat,
Flooding,
Landslide,
Severe
Weather
Wildfire
Public Safety GIS Management. Build
and enhance GIS work done in 2021
Hazard Mitigation Plan Update to
help make the HMP a living
document and an ongoing resource
for understanding risk in Merced
County.
County GIS
Division,
Cities, Cal
OES
$50,000 -
$75,000
Federal,
state and
local
grants,
FEMA
Grants, Cal
OES Funds
High 2-3 years New in 2021
14 NA Wildfire
Encourage and continue to establish
countywide evacuation zones,
sections and routes.
OES
$50,000 -
$75,000
Federal,
state and
local
grants,
FEMA
Grants, Cal
OES Funds
High 2-3 years New in 2021
15 NA Pandemic/
Epidemic
Conduct an After Action Review for
COVID-19 response to identify
lessons learned and ways to mitigate
impacts of future pandemics.
Public
Health, OES
20,000 -
$40,000
Federal,
state and
local
grants,
FEMA
Medium 1-2 years
New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-16
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
Grants, Cal
OES Funds
16 NA Pandemic/
Epidemic
Develop a plan for a Countywide
Medical Reserve Corps to provide
surge capacity to mitigate impacts of
pandemic/epidemics
Public
Health, OES
Staff Time
Dept.
Budget
Medium 2-3 years
New in 2021
17 NA
Agricultural
Pest &
Disease
Provide public outreach through a
variety of media for awareness and
mitigation of various agricultural
pests and disease.
Agricultural
Commissio
ner, CDFA
Staff Time
Dept.
Budget
Low 2-3 years
New in 2021
18 Food,
Water,
Shelter
Agricultural
Pest &
Disease
Enhance the County’s capabilities
associated with the Pest Detection
Program, Pest Exclusion Program, and
Pest Eradication Program to mitigate
agricultural pests and disease.
Delimitation plan activated through
AG Commissioner and CDFA jointly.
Agricultural
Commissio
ner, CDFA
Staff Time
Dept.
Budget
Low 2-3 years
New in 2021
19 HazMat Hazardous
Materials
Identify and increase water
management practices that reduce
pesticide movement offsite to
mitigate hazardous materials impacts
Environmen
tal Health
Staff Time
Dept.
Budget
Low 2-3 years
New in 2021
20 NA Hazardous
Materials
Create a hazardous materials safety
flyer to post on public health social
media and the division of
environmental health's website.
Provide free classes to Merced
County businesses about proper
storage/handling of hazardous
materials and hazardous waste.
Environmen
tal Health
Staff Time
Dept.
Budget
Low 1-2 years
New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-17
ID
Goal(s)
&
Lifelines
Hazard(s)
Mitigated
Description/Background/
Benefits
Lead
Agency
and
Partners
Cost
Estimate
&
Potential
Funding
Priority Timeline Status/Implementation Notes
21 HazMat Hazardous
Materials
Develop countywide commodity flow
study to further understand the
quantity and types of hazardous
materials being transported through
the county to provide the basis for
additional mitigation actions.
Environmen
tal Health
$50,000 -
$175,000
Federal,
state and
local
grants,
FEMA
Grants, Cal
OES Funds
High 2-3 years
New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-18
Table 5-4 Jurisdictional Mitigation Action Summary
ID Hazard(s)
Mitigated Project Title Lead Agency
and Partners Priority Action Status
City of Atwater
1 Multi-
Hazard:
Earthquake
Flooding
Severe
Weather
Wildfire
Participate in
Countywide Public
Education
Program.
OES High Continue Not Started
2*
Multi-
Hazard:
Earthquake
Flooding
Severe
Weather
Wildfire
Integrate Local
Hazard Mitigation
Plan into Safety
Element of
General Plan.
Community
Development
Agency
Medium Continue In Progress
3 Earthquake
Non-structural
Earthquake
Mitigation
Outreach
Public Works Medium Continue Not Started
4 Earthquake
Participate in
Countywide
Inventory for
Unreinforced
Masonry Buildings
-
Public Works Medium Continue Not Started
5*
Multi-
Hazard:
Earthquake
Flooding
Landslide
Severe
Weather
Wildfire
Periodically review
building codes for
updates and
enhancements
Building
Department Medium Continue Not Started
6 Drought
Promote Water
Conservation
Program
Public Works High Continue In Progress
7 Earthquake
Severe
Weather:
General
Dam
Incidents
Emergency power
system to protect
the City of
Atwater 911
Communications
Center and Police
Department
Police
Department High New in 2021
8 Earthquake
Seismic Upgrade
and Remodel of
the Atwater Police
Department
Headquarters
Police
Department High New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-19
ID Hazard(s)
Mitigated Project Title Lead Agency
and Partners Priority Action Status
9 Earthquake
Review hazards
and awareness of
earthquakes in a
public platform
and educate the
public on helpful
procedures in the
aftermath
Police
Department High New in 2021
10 Agricultural
Pest &
Disease
Public education
of current
seasonal threat
Community
Development
Agency
Low New in 2021
City of Dos Palos
1 Multi-
Hazard
Radio upgrade for
police department
Police
Department Medium New in 2021
2 Drought
Construction of
new water
treatment plant
with resiliency
upgrades
Dept. of
Utilities High New in 2021
City of Gustine
1 Flooding
Develop and
enhance storm
water drainage
improvements to
reduce frequent
flooding.
Public Works High New in 2021
2 Earthquake
Perform building-
specific seismic
vulnerability
assessment of
City-owned
critical facilities
constructed prior
to 1980
Public Works Medium New in 2021
3 Drought Develop drought
plan Public Works High New in 2021
4* Flooding
Explore
cost/benefit of
joining the NFIP
Public Works,
Development
Services
Low New in 2021
City of Livingston
1 Multi-
Hazard:
Dam
Incident,
Earthquake
Flooding
Severe
Weather
Wildfire
Participation in
Countywide Public
Education
Program.
OES High Continue Not Started
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-20
ID Hazard(s)
Mitigated Project Title Lead Agency
and Partners Priority Action Status
2 Multi-
Hazard:
Earthquake
Flooding
Severe
Weather
Wildfire
Integrate Local
Hazard Mitigation
Plan into Safety
Element of
General Plan.
Community
Development
Agency
Medium Continue Not Started
3 Earthquake
Non-structural
Earthquake
Mitigation
Outreach
Public Works Medium Continue Not Started
4 Earthquake
Participate in
Countywide
Inventory for
Unreinforced
Masonry Buildings
-
Public Works Medium Continue Not Started
5 Multi-
Hazard:
Earthquake
Flooding
Landslide
Severe
Weather
Wildfire
Periodically review
buildings for
update and
enhancements
Building
Department Medium Continue Not Started
6 Flooding Flood Insurance
Promotion
Planning
Department High Continue Not Started
7 Severe
Weather
Severe Weather
Preparedness
Campaign
Livingston
Fire
Department
High Continue – in progress
8 Drought
Promote Water
Conservation
Program
Public Works High Continue In Progress
9 Flood Upgrade storm lift
station/SCADA Public Works High New in 2021
City of Los Banos
1 Multi-
Hazard:
Earthquake
Flooding
Severe
Weather
Wildfire
Participate in
Countywide Public
Education
Program.
OES / CEO's
Office High Continue – In Progress
2 Multi-
Hazard:
Earthquake
Flooding
Severe
Weather
Wildfire
Integrate Local
Hazard Mitigation
Plan into Safety
Element of
General Plan.
Community
Development
Agency
Medium Continue – In Progress
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-21
ID Hazard(s)
Mitigated Project Title Lead Agency
and Partners Priority Action Status
3 Earthquake
Non-structural
Earthquake
Mitigation
Outreach
Public Works Medium Continue – In Progress
4 Earthquake
Participate in
Countywide
Inventory for
Unreinforced
Masonry Buildings
Public Works Medium Continue – In Progress
5 Multi-
Hazard:
Earthquake
Flooding
Severe
Weather
Wildfire
Periodically review
building codes for
updates and
enhancements
and ensure
necessary
capabilities for
enforcement.
Building
Department Medium Continue – In Progress
6 Severe
Weather
Participate in
Severe Weather
Preparedness
Campaign.
Los Banos
Fire
Department
High Continue – In Progress
7 Drought
Promote Water
Conservation
Program
Public Works High Continue – In Progress
8 Wildfire
Implement and
Monitor Weed
Abatement
Program
Los Banos
Fire
Department
High New in 2021
9 Flooding,
Earthquake,
Wildfire
Prepare
Emergency Plan
for Critical
Infrastructure
Public Works High New in 2021
10 Earthquake
Perform Building-
Specific Seismic
Vulnerability
Assessment of
City-Owned
Critical Facilities
Building
Department High New in 2021
11 Flood
Continue to
Update Storm
Water System
Master Plan
Public Works Medium New in 2021
12 Flood,
Earthquake,
Wildfire
Prepare a Shelter
and Emergency
Provision Plan
Fire
Department Medium New in 2021
13 Severe
Weather
Prepare Weather
Preparedness
Program (Extreme
Heat and Cold)
Fire
Department Medium New in 2021
14 Drought Promote Water
Conservation Public Works High New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-22
ID Hazard(s)
Mitigated Project Title Lead Agency
and Partners Priority Action Status
Program with
continued
updates to Urban
Water
Management Plan
15 Earthquake
Flood,
Wildfire
Rental Home
Inspections
Fire
Department/
Community
Economic
Development
High New in 2021
City of Merced
1 Flooding,
Earthquake,
Wildfire
Prepare an Energy
Assurance Plan Public Works High Continue Not Started
2 Flooding
Develop and
enhance storm
water drainage
improvements to
reduce frequent
flooding
Development
Services High Continue In Progress
3 Dam
Incidents,
Flooding,
Earthquake,
Wildfire
Create a Disaster
Preparedness
Program
Fire
Department High Continue Not Started
4 Flooding
Support Merced
County efforts to
construct the
Haystack
Alternative of
Black Rascal Creek
Development
Services Medium Continue Not Started
5 Flooding
Update the City’s
Storm water
Drainage Master
Plan
Development
Services Medium Continue In Progress
6 Dam
Incidents,
Flooding,
Earthquake,
Wildfire
Prepare a Shelter
and Emergency
Provision Plan
Fire
Department Medium Continue Not Started
7 Wildfire
Prepare a Natural
Area Fire
Prevention Plan
Fire
Department Low Continue Not Started
8 Earthquake
Perform building-
specific, structural
seismic
vulnerability
assessment of
City-owned
critical facilities
Public Works Low Continue Not Started
Merced County Multi-Jurisdictional Hazard Mitigation Plan Mitigation Strategy
2021-2026 Update Page 5-23
ID Hazard(s)
Mitigated Project Title Lead Agency
and Partners Priority Action Status
9 Earthquake
Create a program
to retrofit or
upgrade
unreinforced
masonry buildings
in Downtown
Merced, or other
buildings in the
Plan area.
Development
Services Low Continue Not Started
10 Earthquake
and Flood
Update Fire
Station 52 seismic
and flood
resiliency
Fire
Department Low Continue Not Started
11 Extreme
Heat
Identify and open
additional cooling
zones and centers
within the City of
Merced to provide
additional
capacity of
vulnerable
populations
Police
Department Medium New in 2021
12 Wildfire
Enhance the weed
abatement
program to
mitigate wildfire
risk. Use GIS to
identify properties
where mitigation
is needed. Provide
notice to owners,
and force clean
lots and pursue
cost recovery
expenses.
Fire
Department –
Fire
Prevention
High New in 2021
Merced County Multi-Jurisdictional Hazard Mitigation Plan Plan Adoption, Implementation, and Maintenance
2021-2026 Update Page 6-1
6 PLAN ADOPTION, IMPLEMENTATION, AND MAINTENANCE
6.1 Adoption
The purpose of formally adopting this plan is to secure buy-in from Merced County and the participating jurisdictions, raise awareness of the plan, and formalize the plan’s implementation. The adoption of this plan completes Planning Step 9 of the 10-step planning process: Adopt the Plan. The governing board for each participating jurisdiction has adopted this Local Hazard Mitigation Plan by passing a resolution.
Implementation and maintenance of the plan is critical to the overall success of hazard mitigation planning. This is Planning Step 10 of the 10-step planning process. This section provides an overview of the overall strategy for plan implementation and maintenance, and outlines the method and schedule for monitoring, updating, and evaluating the plan. The section also discusses incorporating the plan into existing planning mechanisms and how to address continued public involvement.
6.2 Implementation
Once adopted, the plan faces the truest test of its worth: implementation. While this plan contains many worthwhile actions, the participating jurisdictions will need to decide which action(s) to undertake first.
Two factors will help with making that decision: the priority assigned the actions in the planning process and funding availability. Low or no-cost actions most easily demonstrate progress toward successful plan implementation.
Implementation will be accomplished by adhering to the schedules identified for each action (see Section 5 for county mitigation actions and the annexes for local mitigation actions), and through constant, pervasive, and energetic efforts to network and highlight the multi-objective, win-win benefits of each project to the Merced County community and its stakeholders. These efforts include the routine actions of monitoring agendas, attending meetings, and promoting a safe, sustainable community. The three main components of implementation are:
Ɣ Implement the action plan recommendations of this plan; Ɣ Utilize existing rules, regulations, policies and procedures already in existence; and Ɣ Communicate the hazard information collected and analyzed through this planning process so that the community better understands what can happen where, and what they can do themselves to be better prepared. Also, publicize the “success stories” that are achieved through the HMPT’s ongoing efforts.
During implementation of these efforts, it is important to maintain a constant monitoring of funding opportunities that can be leveraged to implement some of the more costly recommended actions. This will include creating and maintaining a bank of ideas on how to meet local match or participation requirements, should grants be pursued. When funding becomes available, the participating jurisdiction’s will be in a position to capitalize on the opportunity. Funding opportunities to be monitored include DMA Requirements §201.6(c)(3):
[The local hazard mitigation plan shall include] documentation that the plan has been formally approved by the governing body of the jurisdiction requesting approval of the plan (e.g., City Council, county commissioner, Tribal Council).
Merced County Multi-Jurisdictional Hazard Mitigation Plan Plan Adoption, Implementation, and Maintenance
2021-2026 Update Page 6-2
special pre- and post-disaster funds, special district budgeted funds, state and federal earmarked funds, and other grant programs, including those that can serve or support multi-objective applications.
6.2.1 Role of the Hazard Mitigation Planning Team in Implementation and Maintenance With adoption of this plan, the participating jurisdictions will be tasked with plan implementation and maintenance. The participating jurisdictions, led by the Merced County OES agree to:
Ɣ Act as a forum for hazard mitigation issues;
Ɣ Disseminate hazard mitigation ideas and activities to all participants; Ɣ Pursue the implementation of high-priority, low/no-cost recommended actions; Ɣ Keep the concept of mitigation in the forefront of community decision making by identifying plan recommendations when other community goals, plans, and activities overlap, influence, or directly affect increased community vulnerability to disasters;
Ɣ Maintain a vigilant monitoring of multi-objective cost-share opportunities to help the community implement the plan’s recommended actions for which no current funding exists; Ɣ Monitor and assist in implementation and update of this plan; Ɣ Report on plan progress and recommended changes to the Merced County Board of Supervisors and the governing boards of the other participating jurisdictions; and Ɣ Inform and solicit input from the public.
The primary duty of the participating jurisdictions is to see the plan successfully carried out and to report to their community governing boards and the public on the status of plan implementation and mitigation opportunities. Other duties include reviewing and promoting mitigation proposals, considering stakeholder concerns about hazard mitigation, passing concerns on to appropriate entities, and posting relevant information on the county website (and others as appropriate).
6.3 Maintenance and Monitoring
Plan maintenance implies an ongoing effort to monitor and evaluate plan implementation and to update the plan as required or as progress, roadblocks, or changing circumstances are recognized. This section describes how public participation will be integrated throughout the plan maintenance and implementation process. It also explains how the mitigation strategies outlined in this plan will be incorporated into existing planning mechanisms and programs, such as comprehensive land use planning processes, CIP project planning and building code enforcement and implementation. The plan’s format allows sections to be reviewed and updated when new data become available, resulting in a plan that will remain current and relevant.
6.3.1 Maintenance Schedule
In order to track progress and update the mitigation strategies identified in the action plan, the HMPT will revisit this plan at the following times or occurrences:
Ɣ Annually, to assess if mitigation actions/projects have been completed; Ɣ Following a significant hazard event;
Ɣ Following a disaster declaration; or
Ɣ Any other time the HMPT sees it is prudent or necessary.
DMA Requirement §201.6(c)(4)(i):
[The plan maintenance process shall include a] section describing the method and schedule of monitoring, evaluating, and updating the mitigation plan within a five-year cycle.
Merced County Multi-Jurisdictional Hazard Mitigation Plan Plan Adoption, Implementation, and Maintenance
2021-2026 Update Page 6-3
Annual Reviews: The HMPT will meet annually to assess progress on plan implementation. Merced County’s OES Department will facilitate these reviews and an associated meeting. The timing of the annual meeting is recommended for the first or second quarter of each year to identify potential mitigation grants, some of which have a submittal period in the fourth quarter. A template for the annual meeting and a summary report is provided in Appendix E. Another tool developed during the 2021 process to facilitate regular review and implementation and make the plan more of a “living document” is the LHMP website that includes a GIS/map based –interactive storyboard with highlights of the risk assessment, including interactive hazard maps and a web-based method for collecting, validating, updating and maintaining critical facilities for the plan. This website is accessible from the Merced County OES homepage.
Critical Facility Database Maintenance: Moving forward the County and its municipalities will maintain the critical facility database that was prepared during the 2021 update. The County’s GIS Manager will lead periodic reviews of the database and assess the need for updates, leveraging the LHMP website and Arc-GIS Experience Builder Application noted above.
Five-Year Update: This plan will be updated, approved, and adopted within a five-year cycle as per Requirement §201.6(c)(4)(i) of the Disaster Mitigation Act of 2000. Efforts to begin the update should begin no later than June 2025. The County will monitor planning grant opportunities from the CalOES and FEMA for funds to assist with the update. This may include submitting a Pre-Disaster Mitigation planning grant application. This grant should be submitted in 2024, as there is a three-year performance period to expend the funds, and there is no guarantee that the grant will be awarded when initially submitted. This allows time to resubmit the grant in subsequent years, if needed. Updates to this plan will follow the most current FEMA and CalOES planning guidance. The next plan update should be completed and reapproved by CalOES and FEMA Region VIII by September 2026.