GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan i This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Community Coastal
Resilience Plan
Adaptive Pathways to Improve Community
Resilience
City of Trinidad
July 5, 2024
The Power of Commitment
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan ii This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Project name Trinidad Community Coastal Resilience Planning Project Document title Community Coastal Resilience Plan | Adaptive Pathways to Improve Community Resilience Project number 12578625
File name Draft Resilience Plan.docx
Status
Code
Revision Author Reviewer Approved for issue
Name Signature Name Signature Date
Draft Braden Froble Brett Vivyan
Kristen OrthGordinier
Trever
Parker, SHN
Steve Allen
Rebecca
Price Hall,
City of
Trinidad
GHD Inc.
718 Third Street
Eureka, California 95501, United States
T +1 707 443 8326 | F +1 707 444 8330 | E [email protected] | ghd.com © GHD 2024
This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorized use of this document in any form whatsoever is prohibited.
This project is funded by Proposition
68 grant funds through the Ocean
Protection Council (Grant #C0875010).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan iii This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Executive Summary
The City of Trinidad, located in coastal Northern California, embarked on a coastal resilience planning process between 2022-2024 after hearing numerous concerns from their community about coastal, marine and cultural resources, trails and coastal access, and vulnerable and failing critical infrastructure. The outcome of this effort is the Trinidad Community Coastal Resilience Plan, which describes the work conducted during that time to identify and assess coastal vulnerabilities, listen to community concerns, and develop adaptation strategies to address vulnerabilities and concerns. This work relies on a strong partnership and feedback loop with local Tribes.
The Trinidad Community Coastal Resilience Plan (Plan) looks closely at vulnerabilities from four coastal processes:
shoreline erosion, bluff erosion, coastal flooding, and fluvial flooding. These processes are coupled with OPC’s 2024 Sea Level Rise (SLR) projections. The shoreline erosion scenario represents the landward retreat of the mean high water line with SLR. The bluff erosion scenario represents the landward retreat of the existing bluff edge. To understand the effects of shoreline and bluff erosion on the Trinidad Area coastline, the Plan utilizes USGS CoSMoS shoreline and bluff erosion projections with SLR and local site-specific studies regarding bluff mapping and stability.
The coastal flooding scenarios are comprised of tidal inundation for areas within the upper range of daily tide levels, mean higher high water (MHHW) and temporary coastal flooding associated with the FEMA 100-year storm Base Flood Elevations (BFEs) that incorporate storm surge and wave action. Both types of flooding combine SLR projections to project flood footprints.
Public access and recreation activities were identified by the community as significant community resources. These resources are currently or projected to be impacted by shoreline erosion, bluff erosion, and flooding. Several trails along the bluff faces are vulnerable to shoreline and bluff erosion. The bluff near Edwards Street was identified by the public and Planning Partners as a particularly important location due to trails and beach access, cultural importance, scenic views, location of utilities, and critical vehicle access to the Trinidad Harbor. Significant bluff erosion has been documented along the bluff below the Trinidad Head access road which leads to the Trinidad Head trail and other facilities, prompting the Trinidad Rancheria to declare a state of emergency in 2023. Beaches are vulnerable to shoreline erosion, tidal inundation, and coastal flooding. For 3.3 feet of SLR, the hazard mapping suggests that 90% of the total beach area is eroded. Coastal flooding and sea level rise will also impact public parking and other public amenities, likely leading to temporary closures in the near-term during large storm events. A variety of solutions will need to be implemented to adapt these community resources including maintenance, safety enhancements, retaining structures, and in certain situations, abandonment and relocation.
Critical infrastructure evaluated in this study includes the roadways, water distribution system, stormwater system, and wastewater systems. Critical public services evaluated include privately owned utilities, drinking water, and emergency services. The primary hazard for these resources is bluff erosion. Severe erosion could cut off service or access to individual households or larger portions of the community. Scenic Drive, for example, is subject to localized mass wasting conditions and several locations are currently experiencing active earthflows that have resulted in damaged water transmission lines and settling and separation of roadway pavement. Reduction of soil saturation and structural repairs may keep critical infrastructure in operation in the near term; however, relocation of critical assets away from the bluff edge will be required for continued use in the long-term if erosion continues at historical rates. Additionally, precipitation variability impacts the source water and water quality, which is a high priority with the potential to disrupt community operations as well as the impact the community’s health and safety.
Cultural and natural resources considered in this Planning Study consist of historic properties and places, water, habitat, beaches, and recreational resources. These resources are vulnerable to bluff erosion, shoreline erosion, coastal flooding, and precipitation variability all to varying degrees. The Tsurai Village and Trinidad Head / Tsurewa are two important cultural and historic resources in the Planning Area. Access to the Trinidad Head / Tsurewa is currently at risk of bluff erosion. The Tsurai Village is heavily impacted by bluff and shoreline erosion. Protection and management of the Village is guided by the Tsurai Management Plan, which is referenced frequently in this Study.
Adaptation strategies for these resources will need to include partnerships and consultation with the Trinidad GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan iv This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Rancheria, Tsurai Management Team (State Coastal Conservancy, Tsurai Ancestral Society, Yurok Tribe, City of Trinidad), and Yurok Tribe. Ecological impacts of climate change on cultural and natural resources are not evaluated in this Study but should be considered in future studies.
The resilience strategy presented in this Plan is structured around an Adaptive Pathways Planning approach that embeds adaptation, flexibility, and robustness into long-term strategies and plans to make informed choices to assess risk, minimize losses, and maintain resources and assets valued by the community. Based on community input, maintaining the character of the area is paramount when developing adaptation projects. Adaptive Pathways have been identified for vulnerable resources in select, highly vulnerable areas, including Edwards Street, Scenic Drive, Trinidad Head / Tsurewa, trails and beach access locations, and Luffenholtz Creek. Obtaining public, regulatory, and other stakeholder support to initiate these Adaptive Pathways is critical to maintaining and enhancing community resilience.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan v This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Contents
1. Introduction 1
1.1 Study Approach 3
1.1.1 Planning Area 4
1.2 Stakeholders 5
2. Data Gathering 8
3. Setting 9
3.1 Coastal Setting 9
3.2 Coastal Water Levels 10
3.3 Wave Climate 10
3.4 Sediment Transport 12
3.5 Watershed 12
4. Climate Projections and Hazards 15
4.1 Sea Level Rise and Vertical Land Motion 15
4.2 Increasing Precipitation Variability 18
4.3 Storm Events 18
4.4 Fog 18
4.5 Temperature 19
4.6 Wildfire 20
4.7 Other 20
5. Coastal Processes and Hazards 21
5.1 Shoreline Erosion 21
5.2 Bluff Erosion 23
5.2.1 Climate Projections & Bluff Erosion 25
5.3 Coastal Flooding 29
5.4 Fluvial Flooding 32
6. Planning Area Resources 34
6.1 Public Access and Recreation Resources 34
6.2 Critical Public Infrastructure and Services 35
6.2.1 Roadways 36
6.2.2 Emergency Services 36
6.2.3 Gas, Electric and Communications (Private Utilities) 36
6.2.4 Raw Water (Drinking Water and Fire Suppression) Supply 37
6.2.5 Water Distribution System 39
6.2.6 Stormwater 41
6.2.7 Wastewater 42
6.2.8 Trinidad Harbor Properties 43
6.2.9 Public Amenities 43
6.3 Cultural, Historical, Natural, and Scenic Resources 45 GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan vi This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6.3.1 Cultural Resources 46
6.3.2 Historic Resources 48
6.3.3 Natural Resources 49
6.3.4 Scenic Resources 50
6.4 Future Resources 50
7. Vulnerability Assessment 52
7.1 Vulnerability Assessment Methods 52
7.1.1 Vulnerability Scoring 53
7.1.2 Coastal Hazard Mapping 54
7.2 Public Access and Recreation Resource Vulnerability 56
7.2.1 Trails 56
7.2.2 Beaches 56
7.2.3 Public Parking 56
7.2.4 Amenities 57
7.2.5 Public Parks 57
7.2.6 Vulnerability Summary 57
7.3 Critical Infrastructure and Services Vulnerability 59
7.3.1 Roadways 59
7.3.2 Emergency Services 62
7.3.3 Gas, Electric, and Communications 63
7.3.4 Raw Water Source (Drinking Water) 64
7.3.5 Water Distribution System 65
7.3.6 Stormwater 67
7.3.7 Wastewater 69
7.4 Cultural, Historic, Natural, and Scenic Resource Vulnerability 70
7.4.1 Freshwater Seeps and Streams 70
7.4.2 Trinidad Head / Tsurewa 70
7.4.3 Habitat 70
7.4.4 Scenic Resources 71
7.4.5 Vulnerability Summary 72
7.5 Vulnerability Summary 72
8. Resilience Strategy 74
8.1 Bluff Erosion Adaptation 74
8.1.1 Potential Projects and Vulnerabilities Addressed 74
8.1.2 Adaptation Pathways and Planning Areas for Bluff Erosion Adaptation 76
8.2 Source Water Adaptation 86
8.2.1 Potential Projects and Vulnerabilities Addressed 86
8.2.2 Adaptation Pathways for Source Water 86
9. Works Cited 91
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan vii This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Appendices
Appendix A Data Gathering & Literature Review
Appendix B Coastal Hazards & Sea Level Rise Vulnerability Figures Appendix C Conceptual Layout of Project Opportunity Areas and Example Projects GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan viii This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Table index
Table 3-1 Tidal Datums for Trinidad Harbor-Pier, CA (NOAA Sta. 9419059) 10 Table 4-1 SLR Projections for Trinidad, CA 17
Table 4-2 NOAA Atlas 14 Point Precipitation Frequency Estimates 18 Table 4-3 Cal-Adapt Change in Average Annual Temperature for City of Trinidad 19 Table 4-4 Cal-adapt Wildfire Projections for Humboldt County under the Medium Emissions Scenario 20
Table 5-1 Regional SWELs (BakerAECOM, 2014) 29
Table 5-2 Approximate Current and Future Tidal Datums 29 Table 5-3 Total Water Levels for Trinidad Beaches (BakerAECOM, 2014) 30 Table 5-4 FEMA Base Flood Elevation (BFE) with Future “Likely Range” SLR Projections 32 Table 5-5 FEMA Base Flood Elevation (BFE) with Future “Moderate Risk Aversion” SLR Projections 32
Table 5-6 FEMA Base Flood Elevation (BFE) with Future “Medium-High Risk Aversion” SLR Projections 32
Table 7-1 Potential Impact and Adaptive Capacity Scoring 52 Table 7-2 Potential Impact and Adaptive Capacity Scoring 53 Table 7-3 Vulnerability Scoring Rubric from the APG and used to Assess Resource Vulnerability 53 Table 7-4 Summary of Public Access and Recreation Resource Vulnerability 57 Table 7-5 Public Access and Recreation Resources Vulnerability Score 59 Table 7-6 Summary of Roadway Vulnerability 60
Table 7-7 Roadways Vulnerability Score 62
Table 7-8 Emergency Services Vulnerability Score 63
Table 7-9 Public Utilities Vulnerability Score 63
Table 7-10 Raw Water Supply Vulnerability Score 65
Table 7-11 Summary of Water Distribution System Vulnerability 65 Table 7-12 Water Distribution System Vulnerability Score 67 Table 7-13 Summary of Stormwater Vulnerability 67
Table 7-14 Stormwater Infrastructure Vulnerability Score 69 Table 7-15 Wastewater Vulnerability Score 69
Table 7-16 Cultural, Historical, Natural and Scenic Resource Vulnerability Score 72 Table 7-17 Vulnerability Score Summary 72
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan ix This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure index
Figure 1-1 The Planning Area is located within the traditional and ancestral lands of the Yurok Tribe and the Yurok Village of Tsurai. 2
Figure 1-2 The Project Planning Area is comprised of multiple properties, easements, and overlapping jurisdictions. Planning Partner jurisdictions and consultation areas are located throughout the Planning Area. Planning Partner properties include the City of Trinidad and Trinidad Rancheria. The Planning Area is within the ancestral lands of the Yurok Tribe and the Yurok Village of Tsurai. 5
Figure 3-1 Planning Area topography 9
Figure 3-2 WIS Station 83046 location 11
Figure 3-3 Wave rose for WIS Station 83046 (USACE, 2021) 11 Figure 3-4 Trinidad watershed boundaries (Trinidad Regional Water Management Working Group, 2008) 13
Figure 4-1 Summary of vertical land-level change in the Humboldt Bay region (Patton, et al., 2023) 16
Figure 4-2 SLR projections for Trinidad, CA adapted from the North Spit, CA (OPC, 2024) 17 Figure 4-3 Cal-adapt historical and projected annual average temperature for City of Trinidad 19 Figure 5-1 Bruun Rule illustration. R = shoreline retreat; S = sea level rise; h=closure depth; L = distance offshore (Cooper & Pilkey, 2004); (FitzGerald, Fenster, Argow, & Buynevich, 2008) 21
Figure 5-2 Planning Area beaches 22
Figure 5-3 California coastal cliff erosion viewer; data shown as red dot (Scripps Institute of Oceanography Coastal Processes Group, 2022) 24
Figure 5-4 Active earthflows along the south bluff (SHN, 2019a) 25 Figure 5-5 CoSMoS cliff retreat projections (Barnard, et al., 2022) 27 Figure 5-6 USGS CoSMoS projections and local geologic hazard mapping 28 Figure 5-7 Components of wave runup (BakerAECOM, 2014) 30 Figure 5-8 FEMA flood zones and coastal transects (effective map date 6/21/2017) 31 Figure 6-1 Public access resources 35
Figure 6-2 Water distribution system 40
Figure 6-3 Stormwater resources 42
Figure 6-4 Public amenities 44
Figure 6-5 Natural and scenic resources 45
Figure 6-6 Honeyman drawing of Tsurai and Bay (Photo courtesy of Bancroft Library, included in Tsurai Management Plan, Yurok Tribe Environmental Program 2007) 47 Figure 6-7 Trinidad Head Light Station lighthouse tower 49 Figure 7-1 Public access resources exposed to bluff erosion and flooding (bluff erosion and flooding hazards represent 6.5-foot SLR scenario) 58
Figure 7-2 Roadways exposed to bluff erosion and coastal flooding 61 Figure 7-3 Water distribution system vulnerability 66
Figure 7-4 Stormwater system vulnerability to bluff erosion 68 Figure 8-1 Edwards Street Planning Area 77
Figure 8-2 Edwards Street Area Adaptation Pathways 78
Figure 8-3 Priority Soil Saturation Reduction Area (adapted from (GHD, 2013)) 79 Figure 8-4 Scenic Drive Planning Area 81
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan x This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 8-5 Scenic Drive Area Adaptation Pathways 82
Figure 8-6 Trails and Beach Access Adaptation Pathways 85 Figure 8-7 Source Water Adaptation Pathways 87
Glossary:
Adaptive Pathways Planning – An approach that embeds flexibility and robustness into long-term strategies and plans to improve resilience.
Cher-Ae Heights Indian Community of the Trinidad Rancheria (Trinidad Rancheria) – A federally recognized sovereign Tribal nation within the ancestral territory of the Yurok Tribe and a Planning Partner for the Planning Study.
Community Coastal Resilience Plan – Identifies and describes existing and future coastal hazards, evaluates the vulnerability of resources and infrastructures and identifies opportunities and projects to improve resiliency.
Adaptation strategies and policies may be incorporated into the City of Trinidad Local Coastal Program (LCP) update.
Community Engagement Plan – Outlines past and future engagement efforts for the City of Trinidad Community Coastal Resilience Planning Project. This CEP includes how the City of Trinidad worked with community stakeholders to design the project prior to developing the final project proposal and how the project planning team will engage the community in coastal resilience planning and communicate the project findings and results.
Community Stakeholders – Various organizations and individuals without affiliation with governments, resources managers, regulators or Tribes.
Elevation – All elevations are reported in the National Vertical Datum of 1988 (NAVD88).
Institutional Stakeholders – Government, Resource Managers, Regulators, and Tribes.
Planning Area – Vicinity of Trinidad State Beach, Trinidad Head / Tsurewa, the Trinidad Rancheria Harbor Properties and Pier, City of Trinidad, Tsurai Village, and Trinidad Rancheria. The Planning Area does not have a specific boundary and is expanded in some instances from the general vicinity described above to discuss climate and coastal processes and existing natural and cultural resources of the Yurok Tribe Tsurai Village that contribute to the general Planning Area, such as water supply resources and infrastructure that are located in adjacent watersheds.
Planning Partners – Played a more integral role in developing the Resilience Plan than other Institutional Stakeholders by meeting frequently with the Project Team and sharing relevant information. Planning Partners include the Cher-Ae Heights Indian Community of the Trinidad Rancheria and Tsurai Management Team (City of Trinidad, California State Coastal Conservancy, Tsurai Ancestral Society, Yurok Tribe).
Project Planning Team (Project Team) – City of Trinidad, GHD, and SHN.
Resilience – Making informed choices to assess risk, minimize losses, and maintain resources and assets valued by the community.
State Coastal Conservancy (SCC) – A state agency established to protect and improve natural lands and waterways, to help people get to and enjoy the outdoors, and to sustain local economies along California’s coast. The SCC is a non-regulatory agency that supports projects to protect coastal resources and increase opportunities for the public to enjoy the coast. The SCC holds conservation easements within the Planning Area and is a Planning Partner.
Stakeholders – Groups and individuals who may be positively or negatively affected by coastal and climate processes, along with adaptation strategies or projects in the Planning Area. For the purposes of this GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan xi This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Planning Study, this stakeholder group would represent the General Public (Public) in the greater Trinidad/Tsurai Village community. The Public consists of two sub-groups: Community Stakeholders and Institutional Stakeholders.
Trinidad Community Coastal Resilience Planning Project (Planning Study) – Funded by the Grant Program Funded under Chapter 10 of the California Drought, Water Parks, Climate, Coastal Protection and Outdoor Access for All Act of 2018 (Proposition 68), for the Ocean Protection Council’s Coastal Resilience Program (Agreement Number C0875010). The Planning Study proposes to develop a Community Coastal Resilience Plan (Resilience Plan) for the benefit of the coastal and marine ecosystems, those who call the Planning Area home, the coastal economy, and visitors
Tsurai Ancestral Society (TAS) – A 501(c)3 organization that is a committed steward of the Tsurai Village. They participate in local, state, and federal government processes when advocating for protection and management of the Tsurai Village. They are not affiliated with any other Tribe, Rancheria or organization. A Planning Partner for the Planning Study.
Tsurai Management Team (TMT) – Comprised of the Tsurai Ancestral Society, City of Trinidad, State Coastal Conservancy, and Yurok Tribe. They collaborate to identify problems, potential solutions, and make specific recommendations for the long-term viability of natural and cultural resources within and adjacent to the Tsurai Study Area (TSA).
Tsurai Management Plan (TMP) – A collaborative effort by representatives of the Coastal Conservancy, City of Trinidad, Tsurai Ancestral Society, and the Yurok Tribe to resolve areas of conflict over the management of the Tsurai Study Area (TSA). The Plan was prepared by the Yurok Tribe Environmental Program under a grant agreement with the Coastal Conservancy and presents the findings of research and scoping meetings with stakeholder groups, Management Team meetings, and archival and primary research on the history and current conditions of the cultural, natural, and recreational resources contained within the TSA (Yurok Tribe Environmental Program, 2007).
Tsurai Study Area (TSA) – The TSA is located within the ancestral lands of the Yurok Tribe and current City of Trinidad, in the vicinity of Old Home Beach.
Tsurewa – Yurok name for Trinidad Head, prominent rock feature in the Planning Area and is central to Yurok creation stories and oral tradition.
Vulnerability – The degree to which natural, built, and human systems are susceptible to harm.
Yurok Tribe – A federally recognized Tribe. Yurok ancestral lands include the Lower Klamath River and the California coast from Little River (south of Trinidad) running north to Damnation Creek (north of Trinidad). A Planning Partner for the Planning Study.
Yurok people – Indigenous peoples and their descendants of the Yurok ancestral lands from the Lower Klamath River and the California coast from Little River (south of Trinidad) running north to Damnation Creek (north of Klamath).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 1 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
1. Introduction
The Trinidad Community Coastal Resilience Planning Project (Planning Study) was funded by the Grant Program Funded under Chapter 10 of the California Drought, Water Parks, Climate, Coastal Protection and Outdoor Access for All Act of 2018 (Proposition 68), for the Ocean Protection Council’s Coastal Resilience Program (Agreement Number C0875010). The Planning Study proposes to develop a Community Coastal Resilience Plan (Resilience Plan) for the benefit of the coastal and marine ecosystems, those who call the Planning Area home, the coastal economy, and visitors.
The Project Planning Team respectfully recognizes that the City and Planning Area (Figure 1-1) is located within the traditional and ancestral lands of the Yurok Tribe, and specifically the Tsurai, a Yurok Tribe Coastal Village.
Collaboration and partnerships for coastal resilience provide the foundation for this planning project. The City of Trinidad (grantee), in collaboration with Planning Partners and stakeholders, will identify coastal processes that pose potential hazards to resources and plan for coastal resilience to develop conceptual designs of several implementation projects or strategies. The Planning Partners consist of the Cher-Ae Heights Indian Community of the Trinidad Rancheria, Resighini Rancheria, Tsurai Ancestral Society, Tsurai Management Team, and Yurok Tribe.
The City of Trinidad is comprised of multiple public and private parcels, including individual landowners, public agencies, and public right-of-way. The City is one of California’s smallest incorporated cities, with a population 307 (United States Census Bureau, 2023).
This Resilience Plan focuses on the development of an updated Vulnerability Assessment and adaptation strategies for existing and future coastal processes and conditions. The Vulnerability Assessment documents existing and future coastal processes and conditions to identify hazards and their potential impacts to resources. Vulnerabilities and the associated risk identified in this report are used to inform stakeholders and the development of adaptation strategies based on the resources affected and stakeholder input.
A Community Engagement Plan and Community Engagement & Partnerships Summary Report were developed under separate covers as a part of this Project. Relevant information is summarized or referenced in this Resilience Plan.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 2 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 1-1 The Planning Area is located within the traditional and ancestral lands of the Yurok Tribe and the Yurok Village of Tsurai.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 3 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
1.1 Study Approach
This Planning Study responds to public input received about coastal access, critical infrastructure, and protection of cultural and natural resources. It is intended to provide the necessary resources to continue public engagement, and ultimately identify solutions that address the multi-faceted challenges listed above and other concepts identified by the Planning Partners and other stakeholders. The Resilience Plan begins with a review and summary of previous studies, outlines methods, and then presents the Vulnerability Assessment. A vulnerability assessment is used to advance the understanding of exposure, sensitivity, and adaptive capacity resources within the Planning Area to the impacts of potential future climate change and coastal processes. The intent of the Vulnerability Assessment is to inform the timing and extent of adaptation projects and strategies that enhance coastal resiliency for the community and resources present. The following steps were taken to evaluate vulnerability:
1. Identification of climate change impacts that will pose a risk to resources, including:
a. Sea level rise (SLR)
b. Ocean acidification and upwelling
c. Increasing precipitation variability
d. Storm events
e. Coastal fog dynamics
f. Changes to temperature
g. Wildfire
h. Other potential climate change impacts
2. Identification of primary coastal processes that are the driving factors of risk (e.g., hazards) to resources, including:
a. Shoreline erosion
b. Bluff erosion
c. Coastal flooding
d. Fluvial flooding
3. Identification of resources, including:
a. Public access and recreation resources
b. Critical public service resources
c. Critical public infrastructure and distribution system resources d. Historic, cultural, and natural science resources
e. Future resources
4. Vulnerability Assessment:
a. Define resource exposure to climate change and coastal processes, b. Assess the sensitivity of the resource (i.e., evaluate the level of impact and impacts of greatest concern), c. Evaluate the adaptive capacity of the resource to accommodate climate change impacts while still being functional, and
d. Summarize the vulnerability and vulnerability score (i.e., priority) based on the factors described above.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 4 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
This Planning Study will focus on identifying coastal processes and water levels to evaluate the exposure, sensitivity, and adaptive capacity of resources; likelihood of an event along with the consequence and timing; and adaptation strategies and conceptual design of projects to reduce risk. Adaptation strategies and concept designs will focus on resources and approaches identified as priorities by stakeholders to inform adaptation strategies.
1.1.1 Planning Area
This Planning Study is focused on coastal and climate processes that affect the resources in the vicinity of Trinidad State Beach, Trinidad Head / Tsurewa, the Trinidad Rancheria Harbor Properties and Pier, City of Trinidad, Tsurai Village, and Trinidad Rancheria (herein referred to as the Planning Area). The coastline within the Planning Area is referred to as the West Bluff and South Bluffs, consistent with the Coastal Geologic Hazard Assessment undertaken by SHN (2019a), as indicated in Figure 1-2. The Planning Area does not have a specific boundary and is expanded in some instances from the general vicinity described above to discuss climate and coastal processes and existing natural and cultural resources of the Yurok Tribe Tsurai Village that contribute to the general Planning Area, such as water supply resources and infrastructure that are located in adjacent watersheds. The Planning Area is comprised of multiple, sometimes overlapping, jurisdictions, easements and ownership including but not limited to the City of Trinidad, County of Humboldt, Trinidad Rancheria, Yurok Tribe, and other public and private entities. Coordination among all relevant entities at a given location is paramount, requiring regional cross-collaboration and input. More information about the existing conditions of the Planning Area is described in Section 3 (Setting).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 5 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 1-2 The Project Planning Area is comprised of multiple properties, easements, and overlapping jurisdictions. Planning Partner jurisdictions and consultation areas are located throughout the Planning Area. Planning Partner properties include the City of Trinidad and Trinidad Rancheria. The Planning Area is within the ancestral lands of the Yurok Tribe and the Yurok Village of Tsurai.
1.2 Stakeholders
Various stakeholders (groups and individuals) may be positively or negatively affected by coastal and climate processes, along with adaptation strategies or projects in the Planning Area. For the purposes of this Planning Study, this stakeholder group would represent the General Public (Public) in the greater Trinidad/Tsurai Village community.
The Public consists of two sub-groups: Community Stakeholders and Institutional Stakeholders.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 6 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. • Community Stakeholders
– California Coastal National Monument (CCNM) Gateway Committee – Cal Poly Humboldt Marine Lab
– Fishermen
– North Coast Chapter of California Native Plant Society – Residents
– Visitors (recreational and commuters)
– Families
– Recreators
– Trinidad Bay Watershed Council
– Trinidad Chamber of Commerce
– Trinidad Civic Club
– Trinidad Coastal Land Trust
– Trinidad Museum Society
– Tsurai Ancestral Society
• Institutional Stakeholders (Government, Resource Managers, Regulators, Tribes) – Big Lagoon Rancheria
– Bureau of Land Management (BLM)
– California Coastal Commission (CCC)
– California Coastal Conservancy
– California State Parks
– California Department of Fish and Wildlife (CDFW)
– Cher-Ae Heights Indian Community of the Trinidad Rancheria – Humboldt County – Planning
– Humboldt County – Department of Health and Human Services Division of Environmental Health – North Coast Regional Water Quality Control Board
– Resighini Rancheria
– State Water Resources Control Board
– State Lands Commission
– Tsurai Management Team
– U.S. Army Corps of Engineers (USACE)
– U.S. Coast Guard
– U.S. Fish and Wildlife Service (USFWS)
– Westhaven Community Services District
– Yurok Tribe
The Planning Partners (listed in alphabetical order) consist of the Cher-Ae Heights Indian Community of the Trinidad Rancheria, Tsurai Management Team, and Yurok Tribe. These Tribes and non-profits were initially contacted by the City because they may have knowledge of cultural resources in the Planning Area. The Planning Partners played a more integral role in developing the Resilience Plan than other Institutional Stakeholders by meeting frequently with the Project Team and sharing relevant information. The City also contacted the Resighini Rancheria and Tsurai Ancestral Society. The Resighini Rancheria requested to be informed of the process; therefore, the City will share information after the Planning Study is complete. The Tsurai Ancestral Society requested involvement through the Tsurai Management Team.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 7 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The Cher-Ae Heights Indian Community of the Trinidad Rancheria (Trinidad Rancheria) is a federally recognized sovereign Tribal nation within the ancestral territory of the Yurok Tribe. The Trinidad Rancheria has ancestral ties to the Yurok, Wiyot, Tolowa, Chetco, Karuk, and Hupa peoples. The Trinidad Rancheria was established in 1906 by the enactment of the United States Congress, gained federal recognition from the United States Department of the Interior in 1917, and the Cher-Ae Heights Indian Community of the Trinidad Rancheria was established in 1961 through its Articles of Association. Trinidad Rancheria has three trust parcels in Trinidad, Westhaven, and McKinleyville, comprising 82 acres. In addition to the Rancheria property, the Trinidad Rancheria has owned and operated the Trinidad Pier and Harbor since 2000. Since then, the Trinidad Rancheria has been implementing hazardous waste clean ups and rebuilding infrastructure, including rebuilding the pier and building a new wastewater treatment plant and public restrooms. Several other projects are in progress. The Trinidad Rancheria is an environmental and cultural steward of the Trinidad Harbor and Area of Special Biological Significance (ASBS). As a federally recognized Tribe, the Trinidad Rancheria has rights and responsibilities for ensuring the protection and preservation of cultural resources.
The Tsurai Ancestral Society is made up of documented lineal descendants of the Tsurai Village. The Tsurai Village has been in existence since time immemorial. Being over 65,000 acres in size, Tsurai was the largest southernmost village of the Yurok Tribe. The village is located on the northern coast of California, in Humboldt County. The Tsurai enjoyed an elegant lifestyle until European contact by way of Spanish explorers in 1775. The Spanish erected the wooden cross on Tsurewa and proclaimed the acquisition for the King of Spain, forever naming the area Trinidad.
Since that time, there have been steady changes to Tsurai. Some pieces of this cultural landscape were forever lost, while others remain intact and resilient. Among them, the Tsurai people stand out as paragons of resilience, demonstrating the ability to evolve with changing tides by establishing the Tsurai Ancestral Society, a non-profit organization committed to safeguarding this cultural landscape.
The Tsurai Management Team, comprised of the Tsurai Ancestral Society, the City of Trinidad, the State Coastal Conservancy, and the Yurok Tribe, has collaborated to identify problems, potential solutions, and make specific recommendations to ensure long-term viability of natural and cultural resources within and adjacent to the Tsurai Study Area (TSA). The Management Team finalized and approved the Tsurai Management Plan in 2007 and continues to serve as the primary body for the purposes of implementing the Plan for the Tsurai Study Area (Yurok Tribe Environmental Program, 2007). The Tsurai Management Plan provides specific recommendations and future projects intended to help protect, preserve, and, where possible, restore the cultural, natural, and recreational resources within the TSA. These proposed projects include safer use of primary beach access, development and installation of signs throughout the TSA, protection and restoration of cultural resources, enhancement and restoration of natural resources, and transfer the TSA land to the Yurok Tribe and into trust status through the Department of Interior, Bureau of Indian Affairs. Furthermore, the Tsurai Management Plan states that the natural resources contained within the TSA are components of a larger environmental area, directly adjacent to a designated Critical Coastal Area (CCA) and Area of Special Biological Significance (ASBS) in Trinidad Bay. Just as the TSA contains irreplaceable cultural resources, the TSA borders a unique biological marine area due to its unique coastal and marine resources. Future projected climate change and SLR will continue to affect the TSA.
The Yurok Tribe is a federally recognized Tribe that received federal recognition in 1993. Yurok ancestral lands include the Lower Klamath River and the California coast from Little River (south of Trinidad) running north to Damnation Creek (north of Trinidad). The surrounding landscape, particularly Trinidad Head / Tsurewa, is central to Yurok creation stories and oral tradition. As a federally recognized Tribe, the Yurok Tribe has rights and responsibilities for ensuring the protection and preservation of Yurok cultural resources.
The following descriptions were provided by representatives from each of the Planning Partners. The Project Team would like to recognize that the descriptions used represent each Planning Partners’ characterization of their own government or entity. Specific language, characterizations and other details may be questioned or disputed by others, but have been maintained as provided, to accept Planning Partners in their own words.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 8 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
2. Data Gathering
Several regional and location-specific studies and plans have been developed to characterize a variety of current and future processes, as well as resources in the Trinidad area. Studies and plans in the Trinidad area that are directly related to the objectives of this Planning Study are summarized in Appendix A and listed here:
– Trinidad General Plan (multiple document updates).
– Engineering Geologic Assessment of the Tsurai Village with Recommendations for Future Management (LACO, 2004).
– Humboldt County General Plan Volume II Trinidad Area Plan (County of Humboldt, 2007). – Tsurai Management Plan (Yurok Tribe Environmental Program, 2007). – Preliminary Geologic Hazard Report (PWA, 2008)
– Trinidad-Westhaven Integrated Coastal Watershed Management Plan (City of Trinidad, 2008a). – Results of Factor-of-Safety Analysis and Erosion-Rate Assessment (Busch, 2009) – City of Trinidad ASBS Stormwater Improvement Project Geotechnical Analysis (GHD, 2012). – Nearshore Hydraulics, Humboldt Bay, California (FEMA, 2014). – City of Trinidad Climate Change Vulnerability Report and Adaptation Response (GHD, 2016). – Coastal Bluff Setback Analysis, 20 Scenic Drive, Trinidad California (SHN, 2016a). – Supplemental Information Relative to Coastal Bluff Setback Analysis, 20 Scenic Drive, Trinidad California (SHN, 2016b)
– Preliminary Assessment of Current Slope Stability Conditions, Trinidad Memorial Lighthouse, Edwards Street, Trinidad (SHN, 2017a).
– Landslide Mitigation Assessment, Trinidad Memorial Lighthouse and Edwards Street, Trinidad, California (SHN, 2017b).
– Humboldt County General Plan (County of Humboldt, 2017). – State of California Sea Level Rise Guidance 2018 Update (OPC, 2018) – California Coastal Commission Sea Level Rise Policy Guidance: Interpretive Guidelines for Addressing Sea Level Rise in Local Coastal Programs and Coastal Development Permits (California Coastal Commission, 2018) – California’s Fourth Climate Change Assessment (Grantham, 2018). – Humboldt County Operational Hazard Mitigation Plan, Volume 2 – Planning Partner Annexes. Trinidad Annex Local Hazard Mitigation Plan (Tetra Tech, 2020).
– Coastal Landslide Hazard Evaluation, City of Trinidad, California (SHN, 2019a). – Draft Edwards & Van Wycke Sea Level Rise and Landslide Risk (SHN, 2019b). – California Adaptation Planning Guide (Cal OES, 2020)
– Foundation Soils Investigation and Geologic Hazard Evaluation Report (Vadurro, Foundation Soils Investigation and Geologic Hazard Evaluation Report for a Proposed Residence, 150 Scenic Drive, Trinidad; APN 042-141- 003, 2021a)
– Addendum to Foundation Soils Investigation and Geologic Hazard Evaluation Report (Vadurro, 2021b) – City of Trinidad Municipal Services Review and Sphere of Influence Update (LAFCO, 2021). – Climate Change Vulnerability Assessment for the California Coastal National Monument: Trinidad and Point Arena-Stornetta Units (USGS, 2021).
– Coastal Bluff Mapping, City of Trinidad, California (SHN, 2022). – Humboldt Regional Climate Resilience Plan, Public Review Draft (Carman, et al., 2022). – State of California Sea Level Rise Guidance: 2024 Science and Policy Update – Draft Release (OPC, 2024) GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 9 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
3. Setting
3.1 Coastal Setting
The Planning Area is located at the northernmost extent of the Eureka Littoral Cell, which is bound to the north by the Trinidad Head / Tsurewa and False Cape, approximately 40 miles to the south, near Cape Mendocino (California CSMW, 2017). North of the Trinidad Head / Tsurewa, there is an apparent gap between littoral cells. The littoral cell north of the Eureka cell is the Klamath River cell, for which the southern boundary is Rocky Point, a headland located approximately 5.5 miles north of the Trinidad Head / Tsurewa (Department of Navigation and Ocean Development, 1977). The Planning Area shoreline, within the Eureka Littoral Cell, is characterized by sandy beaches backed by coastal bluffs that range in elevation from 60 to 150 feet. There are numerous large rocks and headlands that define the coastline. Pocket beaches and coves have formed between the headlands. The Trinidad Head / Tsurewa serves to shelter the southeast facing beaches (i.e., Trinidad Harbor / Trinidad Harbor-Pier, Launcher Beach, and the South Bluff) from a northerly / westerly wave approach.
The Planning Area exhibits a range of elevations with sandy beaches typically ranging from 3 to 20 feet and steep bluffs reaching 50 to 150 feet or higher (Figure 3-1). Much of the developed areas associated with the Trinidad Harbor-Pier and adjacent parking lots are located between elevation 20 to 30 feet.
Figure 3-1 Planning Area topography
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 10 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
3.2 Coastal Water Levels
The tides in and around the Planning Area are mixed semi-diurnal, with two unequal low and high tides each lunar day, an approximate 25-hour time period. The National Oceanic and Atmospheric Administration (NOAA) operates tide stations throughout coastal California. The representative gauge for which datums are provided is located at the Trinidad Harbor-Pier (Sta. 9419059). The tidal datums representative of this Trinidad Harbor-Pier station are provided below in Table 3-1.
Table 3-1 Tidal Datums for Trinidad Harbor-Pier, CA (NOAA Sta. 9419059) Datum Elevation, ft (NAVD88)
Highest Observed (01/26/1983) 10.14
Mean Higher High Water (MHHW) 6.48
Mean High Water (MHW) 5.80
Mean Tide Level (MTL) 3.38
Mean Sea Level (MSL) 3.36
Mean Low Water (MLW) 0.96
Mean Lower Low Water (MLLW) -0.25
Lowest Observed (12/30/1974) -2.92
The Trinidad Harbor-Pier station is currently inactive and the data record is limited. The nearest station for which water level data is available is the North Spit Station (Sta. 9418767), located approximately 20 miles to the south, in Humboldt Bay. The tidal datums provided by NOAA, between MLLW and MHHW, for these stations are typically within
0.1 feet of each other. When longer periods of record are required to establish datums for less frequent events, such as the 1% annual chance water level, tidal datums of the North Spit Station (Sta. 9418767) are utilized for this study.
3.3 Wave Climate
The Pacific Northwest region, including northern California, is subject to the most extreme wave climate among the continental U.S. (Costa & Glatzel, 2002). This region experiences a dominant northwest swell direction, though there are seasonal trends among both wave height and direction. During the winter, storm swells approach from the west to west-northwest, reaching maximum offshore wave heights of 32 to 40 feet. Summer conditions are characterized by wind-wave conditions from a northerly direction, with maximum offshore wave heights reaching 16 to 23 feet (California CSMW, 2017).
The USACE provides long-term wave hindcast resources along the coastline of California as a part of the Wave Information Studies (WIS) project. The station most representative of the Planning Area is located directly offshore of Little River State Beach (Figure 3-2). Shown below, Figure 3-3 displays the wave climate for this region as a wave rose, in which west to northwest swells are dominant. Additionally, Figure 3-3 displays significant wave heights reaching 4 to 8 meters (13 to 26 feet). Maximum or extreme wave heights are not represented in the wave rose, as these extremes occur for a very short period of time over the duration of the data set typically used.
The Planning Area contains opposing shoreline orientations that are separated by a natural headland, each of which are exposed to different wave directions. North of the headland, Trinidad State Beach is oriented to the northwest and exposed to the stronger winter swells, while south of the headland the shorelines are oriented towards a more southerly direction. As the dominant wave direction is northwest, this headland creates a natural embayment for the south facing beaches. The extent of wave exposure varies with distance from the headland to the south. For example, the Trinidad Harbor is a natural embayment from northwest swell directions and provides shelter for vessels and small-scale maritime activity.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 11 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 3-2 WIS Station 83046 location
Figure 3-3 Wave rose for WIS Station 83046 (USACE, 2021) GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 12 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
3.4 Sediment Transport
Sediment transport within the Eureka Littoral Cell is primarily driven by waves and currents. The majority of sediment is delivered to the littoral cell via fluvial sources, in which there are three main nearby rivers that discharge into the Pacific Ocean: Little River, Mad River, and Eel River (California CSMW, 2017). The Little River is the closest significant fluvial source to Trinidad, located approximately two miles to the south, although several smaller creeks discharge within the Planning Area. There is uncertainty surrounding the overall transport patterns within this region; however, the wave climate suggests that it is seasonally bidirectional (California CSMW, 2017). During the winter, a westerly wave direction results in a northerly transport, whereas a northerly wave direction in the summer results in southernly transport. Complexities in the offshore bathymetry may lead to more site-specific variability within the cell.
There is little information available regarding the sediment transport for the beaches located within the Planning Area.
Trinidad Head / Tsurewa is the northern boundary for the Eureka Littoral Cell, therefore, sediment input from north of the headland is unlikely. In addition, numerous other headlands in this area may serve as sediment traps, blocking the flow of transport and, in some cases, retaining a stable beach. Figures presented by CSMW (2017) and the Department of Navigation and Ocean Development (1977) suggest that the dominant transport direction directly to the south of the Trinidad Head / Tsurewa is southerly.
As mentioned above, a portion of the Planning Area, being Trinidad State Beach, is located in a gap between the Eureka and Klamath River Littoral Cells. In addition, there is little to no information available regarding sediment transport between the Trinidad Head / Tsurewa and Rocky Point to the north. Therefore, some extrapolation is needed to make assumptions, although the complex shoreline and intense wave climate pose a challenge when discerning the sediment transport patterns.
3.5 Watershed
The Planning Area focus includes several small drainage areas or watersheds near the bluffs and shoreline. Additional consideration is given to the larger watersheds when appropriate, as water quality and quantity within the Planning Area focus is influenced by adjacent watersheds (Figure 3-4).
Drinking Water
The Planning Area sources primarily surface water for potable water treatment and distribution; however, groundwater and spring well systems are also common for private systems (Trinidad Regional Water Management Working Group, 2008). There are no lakes or reservoirs in the vicinity. The primary source of surface water is Luffenholtz Creek, a system with over 16.3 miles of streams (Trinidad Regional Water Management Working Group, 2008). Water suppliers in and adjacent to the Planning Area are both municipal and private, with the municipal entities including the City of Trinidad and the Westhaven Community Services District. The City of Trinidad sources and treats 30 million gallons of water annually from Luffenholtz Creek, approximately two miles south of the Planning Area focus.
The water quality for the Planning Area is generally acceptable during the dry season; however, precipitation events during the wet season result in significant water quality treatment challenges. Precipitation events increase turbidity in the source creeks as excess sediment is washed into the system. The excess sediment coincides with increased bacterial contamination. Treatment of water during the wet season can be problematic, turbidity is a limiting factor for the Trinidad water treatment plant. Raw water with high levels of turbidity cannot be treated at the plant. Due to the Creek sensitivity to flow conditions and contaminants, the Creek has been designated as a Critical Municipal Water Supply Area in the Humboldt County General Plan.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 13 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 3-4 Trinidad watershed boundaries (Trinidad Regional Water Management Working Group, 2008) GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 14 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Stormwater
Water quality issues are not limited to potable water in the Planning Area. Contaminated runoff presents challenges for the beaches and ASBS, which is located just offshore of the Planning Area beaches. The largest pollutant inputs to the ASBS are Total Suspended Solids (TSS), Total Organic Carbon (TOC), nitrate, and oil & grease (ADH Enviornmental, 2015). Bacterial water quality-related beach closures have also occurred in the past. The stormwater system within the City of Trinidad primarily consists of roadside ditches, drain inlets, culverts, and infiltration galleries to prevent direct discharge to the ASBS. Roadside ditches, drain inlets, and culverts are the primary means of conveying stormwater in adjacent watersheds.
Groundwater
Contributions to groundwater in the Planning Area are derived from natural processes, stormwater infiltration galleries, and surface infiltration from individual septic systems. Wastewater systems in the Planning Area are on-site septic systems, as the Planning Area does not have a centralized wastewater system.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 15 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
4. Climate Projections and Hazards
4.1 Sea Level Rise and Vertical Land Motion
Sea level rise (SLR) projections are provided for 12 active tide gauges along the coast of California in the Ocean Protection Council’s (OPC’s) State of California Sea-Level Rise Guidance 2018 Update. The 2018 update to the CCC Sea Level Rise Policy Guidance refers to these as the “best available science” on SLR projections in California. These projections are recommended by the CCC for planning, permitting, and other coastal management decisions. OPC recently issued a Draft 2024 Update that was adopted in June 2024. The nearest tide gauge to the Planning Area is North Spit (NOAA Sta. 9418767), which is located approximately 20 miles to the south at the Humboldt Bay inlet.
In the context of SLR, localized subsidence would enhance rates of SLR along the coast. As mentioned above, the nearest tide station for which SLR projections are provided by the OPC is North Spit. Tectonic activity in the Humboldt Bay region is variable, meaning that vertical land movement displays trends of both uplift and subsidence. In relation to SLR, localized uplift or subsidence can potentially decrease or increase rates of sea level trends at a particular location along the coastline. The Humboldt Bay Vertical Reference System Working Group evaluates the tectonic contributions to local sea level in northern California. The vertical land motion at the Trinidad tide gauge location is reported to be -0.87 mm/year (0.0029 feet/year or 0.04 inch/year), whereas monitoring locations further inland, along Highway 101 show uplift (Cascadia GeoSciences, 2017). Relative SLR in the Humboldt region was also studied by (Patton, et al., 2023) and the results indicate similar trends (Figure 4-1).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 16 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 4-1 Summary of vertical land-level change in the Humboldt Bay region (Patton, et al., 2023) GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 17 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The Patton et al., (2023) study indicates that the North Spit location is subsiding at a higher rate than that of the Trinidad area, with -3.21 mm/year. The difference in vertical land motion between Trinidad and the North Spit is 2.34 mm/year (0.0077 feet/year).
The OPC 2024 projections for sea level rise at the North Spit were adjusted for the difference in vertical land motion and are shown in Figure 4-2 and Table 4-1. OPC 2024 identifies the Intermediate-Low scenario as the lower bound for the most likely sea level rise by 2100, the Intermediate as a reasonable upper bound for the most likely range of sea level rise by 2100, and the Intermediate-High as corresponding to other scientific estimates of plausible high-end projections. The High scenario is described as embedded with deep uncertainties and ambiguity framing the worst case beyond 2100 and estimating a likelihood is not possible (OPC, 2024).
Figure 4-2 SLR projections for Trinidad, CA adapted from the North Spit, CA (OPC, 2024) Table 4-1 SLR Projections for Trinidad, CA
Time Horizon Likely Range (feet) Less than 1% Chance (feet) IntermediateLowIntermediate Intermediate High High
2030 0.4 0.4 0.4 0.5
2050 0.8 1.0 1.2 1.4
2070 1.3 1.7 2.5 3.3
2100 2.2 3.7 5.3 7.1
This Resilience Plan evaluates the vulnerability of existing infrastructure, assets, and resources to SLR. Common SLR planning projects include projections from 2050 to 2100. SLR will be considered in conjunction with vertical land motion, extreme events, and coastal processes to identify prominent, potential hazards for stakeholders in the Planning Area.
0 2
4 6
8 10
12 14
16 2030 2040 2050 2060 2070 2080 2090 2100 2110 2120 2130 2140 2150 SLR (ft above 2020 baseline)
Planning Horizon
SLR Projections (OPC 2024, 2018). Adapted to Trinidad, CA 2018 Likely range
High
Intermediate High
Intermediate
Intermediate Low
Low
2018 Medium High Risk Aversion
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 18 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
4.2 Increasing Precipitation Variability
Precipitation records from nearby locations at the Arcata / Eureka Airport, located 5.7 miles south of the Planning Area, and Su-meg (formerly Patrick’s Point) State Park, located 5.7 miles north of the Planning Area, report approximate averages of 120 rainy days per year and 46 to 61 inches per year, respectively (City of Trinidad, 2008b).
More intense storms within a shorter time period are expected without significant changes to total annual precipitation (USGS, 2021). These changes in the intensity and time period of precipitation are expected to result in prolonged dry seasons and reduced soil moisture conditions. Annual rainfall each year is expected to move toward more extremes, with extreme wet years and extreme dry years. Stream flows are expected to decline below historical averages in the dry season and peak flows are expected to increase in the winter (USGS, 2021).
According to California’s Fourth Climate Change Assessment (FCCA), the North Coast Region receives most of its annual precipitation in the winter between November and March through the delivery of large storms known as atmospheric rivers (Grantham, 2018). These large storms deliver heavy rainfall over a narrow area and the presence or absence of these storms has major impact to water supply each year. Overall, models from the FCCA predict that the volume of annual precipitation will fall within the range of historical variation or trend slightly higher for the North Coast region by the end of the century. However, the same research indicates that variability of precipitation delivery is likely to increase. Predictions in variability include:
– A wet season that is compressed into a shorter period of time, resulting in later onset of fall rain and early onset of spring drying,
– An increase in the intensity of storms,
– A rise in the frequency of extremely dry years, resulting in extreme swings between wet and dry.
As a result of the expected change to precipitation delivery, the FCCA states that the North Coast Region may see an effective loss of 3-6 inches of annual rainfall and that climatic water deficits may increase by 16-32% by the end of the century.
4.3 Storm Events
The North Coast of California currently experiences the greatest storm intensity in the state with regards to the threeday maximum precipitation (USGS, 2021). The intensity of individual storms is expected to increase in the future (Prein, et al., 2017). Extreme rainfall events can be expected to potentially flood low-lying or poorly-drained areas in addition to eroding natural and modified drainage channels. Higher turbidity of runoff and receiving waters is associated with increased storm intensity. Current estimates for precipitation depth for a range of recurrence intervals are presented in Table 4-2.
Table 4-2 NOAA Atlas 14 Point Precipitation Frequency Estimates Duration
Average Recurrence Interval (yr) Rainfall Depth (inches) 1-yr 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr 200-yr 500-yr 1000-yr 24-hr 3.01 3.69 4.56 5.28 6.24 6.98 7.74 8.51 9.57 10.40
4.4 Fog
Changing ocean, air, and earth temperatures will likely alter the timing, frequency, and duration of coastal fog. Fog is important in many areas and, among several positive outcomes, provides natural cooling, decreased evapotranspiration, and more productive ecosystems (GHD, 2016).
The FCCA report states that coastal forests receive up to a third of their water from fog and many coastal species, such as the redwood, can take in water directly through their leaves from fog (Grantham, 2018). Fog also generates fog drips to the understory during times that would otherwise be dry, providing some water to understory vegetation.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 19 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The water and shade provided by fog reduces temperatures and evapotranspiration rates, as well as helps lower fire risk. A reduction of fog during summer months would increase evapotranspiration and reduce overall surface water resources. The FCCA states that it is difficult to predict summertime fog trends through time due to various conditions that impact fog, such as coastal upwelling, onshore breezes, and high inland temperatures. However, with climate change predictions of higher temperatures and stronger winds, it is likely that coastal fog dynamics will change even if that change is not able to be currently quantified.
4.5 Temperature
The global temperature increase that has been documented over the past century is referred to as global warming.
Global warming is largely related to greenhouse gas emissions that accumulate in the upper layers of the atmosphere.
Greenhouse gasses act as a thermal insulator, trapping energy from the sun and resulting in a net warming of the planet (NASA, 2023).
Information on temperature increases for the Planning Area was obtained from Cal-Adapt.org. Cal-Adapt provides annual average temperature projections out to a time horizon of 2099 for medium and high emission scenarios.
Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 represent the medium and high emission scenarios, respectively. The projected annual average temperature change for the Planning Area is shown below in Table 4-3 and Figure 4-3 for years 2035, 2050, 2070, and 2100. The change in temperature was derived from observed data for a time period between 1961 to 1990, for which the annual average temperature was 62 degrees Fahrenheit (F).
Table 4-3 Cal-Adapt Change in Average Annual Temperature for City of Trinidad Year 2035 2050 2070 2100
Emissions Scenario RCP
4.5 RCP
8.5 RCP
4.5 RCP
8.5 RCP
4.5 RCP
8.5 RCP
4.5 RCP
8.5 Change in Temperature from baseline
(degrees, F)
1.8 2.4 2.6 3.4 3.3 5.1 4.2 8.0
Figure 4-3 Cal-adapt historical and projected annual average temperature for City of Trinidad The projections for the medium and high emissions scenarios are relatively similar (less than 1 degree F difference) for years 2035 and 2050. The range between emissions scenarios increases after 2050, which may represent a higher degree of uncertainty. The projected temperature increase for year 2035 ranges from 1.8 to 2.4 degrees F, while the projected temperature increase for year 2100 ranges from 4.2 to 8.0 degrees F.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 20 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
4.6 Wildfire
Wildfires present a range of hazards to the community, from public health and safety to environmental degradation.
One significant health risk that can result from wildfires is reduced air quality, which can impact areas on a regional scale. The smoke and particulate matter that is released into the air can lead to increased hospitalizations, and people with chronic health conditions are most vulnerable (Grantham, 2018). Other wildfire impacts can include loss or disruption to critical facilities or services, such as potable water or electric utilities.
Wildfires projections with climate change in northern California suggest a longer fire season, increase in wildfire frequency and severity, and an expansion of the area susceptible to wildfire (Grantham, 2018). This is partially due to the rising air temperatures associated with climate change, but many other consequences of climate change may contribute to the shifting wildfire risks. Within Humboldt County, a lower snowmelt equivalent and earlier snowmelt pattern that arises with climate change will limit the availability of water, leading to more frequent conditions with higher fire risk (HCFSC, 2019).
Cal-Adapt provides wildfire projections for the mid- and end-century time horizons based on several models.
Projections are available for various locations and allow for the option of the medium (RCP 4.5) and high (RCP 8.5) emissions scenarios. The Cal-adapt wildfire projections for Humboldt County are shown below in Table 4-4. The projections indicate an increase of approximately 5,700 and 9,500 hectares burned for the mid- and end-century 30-year average, respectively. The decadal wildfire probability, which is the probability of occurrence of one or more fires in a given area (grid cell) during the decade, is also shown below in Table 4-4. The probability of occurrence is consistent for both time horizons, being a 20% probability. Wildfire probabilities were estimated by Cal-Adapt from California’s FCCA (Grantham, 2018). It is also important to note the 30-year range for both the annual hectares burned and the probability of occurrence. The range for the end-century is much greater than the mid-century for the annual hectares burned and 10% greater for the probability. This increase in range is indicative of uncertainty for projections spanning out to ~2100.
Table 4-4 Cal-adapt Wildfire Projections for Humboldt County under the Medium Emissions Scenario Time Horizon Annual Acres Burned Decadal Wildfire Probability 30-Year Average 30-Year Range 30-Year
Average
30-Year
Range
Baseline 1961-1990 12,748 1,690 - 62,523 10% 10%-20%
Mid-Century 2035-2064 18,417 3,151 - 51,381 20% 10%-20% End-Century 2070-2099 22,197 4,900 - 149,988 20% 10%-30%
4.7 Other
The climate projections discussed above are only a subset of the climatic processes that might be affected by climate change. These climate projections were chosen for discussion and analysis due to applicability and the availability of data for the Planning Area. That is, there is adequate information to assess the Planning Area and the climate projection has the potential to impact the Planning Area.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 21 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
5. Coastal Processes and Hazards
Coastal processes are key elements to consider when evaluating coastal hazards and future conditions with a changing climate. Coastal processes are natural and dynamic, which transition into hazards when presenting risk to development within the coastal zone. The following sections will provide general discussion of how SLR and other climate projections will affect coastal hazards such as shoreline erosion, bluff erosion, and coastal flooding.
5.1 Shoreline Erosion
Erosion, in the case of sandy beaches, is a dynamic process that results from a sediment deficit in combination with hydrodynamic forces acting at the shoreline. Eroded sediment is transported in the longshore or cross-shore direction as the MSL shoreline marches landward. Depending on the setting, this process may be spontaneous and event based, or chronic and continuous. Forces such as wave exposure and wave action at the shoreline are significant drivers in this process; however, physical elements such as grain size also dictate the stability of the shoreline.
Projected changes to climatic processes will all impact shoreline erosion to some degree, as these processes are ultimately linked together. The process that will most likely have the greatest impact to shoreline erosion is SLR, thus this section will be focused around SLR.
In general, increased water levels with SLR may result in increased rates of erosion for a sandy shoreline. A simple method to examine a sandy shoreline response with SLR is the Bruun Rule. Sandy shorelines are located in select, isolated areas of the Planning Area, typically between the bluffs and ocean. The Bruun Rule assumes that as the sea level rises, the profile shifts landward and upward to maintain a position relative to MSL. The sediment eroded from the dry beach is deposited offshore to the closure depth, which is the depth or offshore limit of sediment transport from the nearshore region (Figure 5-1). The landward shift is calculated with the sand/dune crest elevation, closure depth, SLR, and the total distance of the active profile. As this method is one-dimensional and requires several assumptions, including longshore uniformity, it is likely that the sandy shoreline response to SLR, where relevant, will be approximated by the Bruun Rule. As mentioned above, sediment transport and erosion are dynamic processes that are difficult to predict with precision.
Figure 5-1 Bruun Rule illustration. R = shoreline retreat; S = sea level rise; h=closure depth; L = distance offshore (Cooper & Pilkey, 2004); (FitzGerald, Fenster, Argow, & Buynevich, 2008) The total extent of shoreline erosion is limited by the characteristics of the back beach. For instance, the existence of dunes / vegetation, bluffs or cliffs, or coastal development will all affect the rates of erosion once the beach has been completely eroded or taken over by SLR. In addition, once the high-water shoreline cannot continue to migrate landward, the recreational (dry) beach may be entirely overtaken, along with intertidal habitat. This process is referred to as coastal squeeze and, as this occurs, safe coastal access and use will be limited by the tidal cycle and other oceanographic conditions. It should also be noted that coastal bluffs, dunes, and development will erode differently than a sandy beach.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 22 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The Planning Area beaches are sand dominant pocket beaches, meaning that they are situated in coves and are backed by coastal bluffs. Several large rocks are present just offshore of the beaches, which may provide some protection against wave action. One portion of the shoreline exists that is not backed by a bluff, being the southernmost area of Trinidad State Beach, west of the parking lot (Figure 5-2). At this location, vegetated dunes approximately 60 to 100 feet wide are the primary buffer between the parking lot and the beach. Erosion of dunes will be primarily dependent on factors such as the type and distribution of vegetation, elevation, sediment grain size, wind conditions, and wave attack.
Figure 5-2 Planning Area beaches
There is little data available for the Planning Area regarding historic erosion rates and the current stability of the shoreline. The Coastal Geologic Hazard Assessment (SHN, 2019a) provides additional detail relative to the bluff retreat hazard and notes the significance of aspect, geology, and beach width on Trinidad area beaches. Trinidad GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 23 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
State Beach (West Bluff) is fronted by a broad beach that is generally stable except under extreme winter conditions as sand accumulates between the natural headlands. The area along the South Bluff area occur in the wave shadow of Trinidad Head, are cut off from most littoral sediment transport, and beaches here are narrow and vulnerable to winter surf that refracts around Trinidad Head (SHN, 2019a).
Impacts to shoreline stability is expected to vary among the Trinidad beaches with SLR due to the significant variation in shoreline orientation and wave exposure north and south of the headland. Impacts at Trinidad State Beach (north of the headland) will depend on the capacity of the beach to adapt to rising sea levels. Based on the limited information available regarding sediment transport, erosion, and accretion, there is uncertainty regarding whether this increase in wave action will lead to relatively higher erosion rates in the short term. However, in the long term, it is expected that coastal access and erosion will become problematic with increased wave action as the high-water shoreline approaches the parking lot. Seasonal patterns in beach erosion and accretion occur but are not well documented.
5.2 Bluff Erosion
The majority of the shoreline in the Planning Area is backed by coastal bluffs ranging in elevation from 60 to 150 feet.
Bluff erosion is a process that is largely connected to oceanic forces (i.e., waves and tides) acting on the shoreline and is a process that may occur over geologic time. A primary driving force in coastal bluff erosion is wave action, wherein wave energy erodes the base of the bluff. Along Trinidad beaches the exposure to wave energy is relative to the coastal aspect and proximity to Trinidad Head.
The stability of the shoreline is linked to stability of the bluff, in that erosion of the shoreline will allow for increased wave attack at the bluff toe. Erosion at the bluff toe leads to destabilization of the bluff face, resulting in episodic landslide events. Other driving forces of bluff erosion to consider include earthquakes, groundwater conditions, and rainfall. For the Planning Area, bluff erosion is a factor of the exposed material in the bluff face, the height of the bluff, the availability of stable beach fronting the bluff, and the intensity of wave / tidal action on the bluff toe (SHN, 2019a).
During preparation of the Tsurai Management Plan, LACO Associates conducted an Engineering Geologic Assessment of the Tsurai Village with Recommendations for Future Management. This study identifies factors which may ultimately contribute to localized slope instability in and around Tsurai Village. These factors include diversion, concentration, and discharge of surface runoff onto the slopes above and on Tsurai Village: groundwater elevation and spring creek flow volume; disposal of landscape yard waste and girding and topping of trees on the slopes above Tsurai Village; continual destabilization of the coastal bluff toe slope from wave and tidal processes, and; strong earthquake ground shaking (LACO, 2004). These factors may include both natural and development-related components that may increase or decrease slope stability. Natural components include geology, vegetation cover and variations in annual precipitation. Development-related components include hardscapes such as rooftops, driveways, and patios that may increase runoff but reduce groundwater elevations, septic system leach field spacing and size and irrigation volume contributions to ground water levels, and landscape maintenance practices that may increase or decrease vegetated cover and affect runoff and groundwater contributions. Depending to the magnitude of contributions of each of these natural and development-related factors the bluff may increase or decrease in stability compared to a baseline condition, such as pre-development.
El Nino weather conditions during the 2017/2018 winter season (higher than normal rainfall, long periods of high surf) resulted in reactivation of a large earthflow on the bluff face along Edwards Street. The head of the earthflow reached the southern edge of Edwards Street and threatened the Trinidad Memorial Lighthouse, which was ultimately relocated. The landsliding subsided over the past several years, until recent heavy rains triggered renewed movement that was evident as active subsidence at the head of the landslide. This earthflow encompasses the entire bluff face, from the crest to the beach.
Exceptional wave action along the California coast during the winter of 2022 to 2023 eroded multiple locations along the toe of the south bluff slope, as well as approximately 30 feet of the bottom portion of the Axel Lindgren Memorial Trail located in Tsurai Study Area, making it dangerous to access Old Home Beach from the trail. For this reason, the City of Trinidad closed the Axel Lindgren Memorial Trail at the bluff top, adjacent to the former location of the Memorial GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 24 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Lighthouse. Some restoration to the eroded areas has occurred with biodegradable erosion control mats and Tsurai Ancestral Society would like to have the trail redesigned and constructed to follow the traditional alignment.
Coastal cliff retreat in California was recently explored in a statewide study by Scripps Institution of Oceanography (SIO) (Swirad & Young, 2022). This study evaluated cliff retreat rates between 2009-2011 and 2016 at transects spaced along the California coast. The nearest transect with available data is located just north of the Trinidad Head / Tsurewa (Figure 5-3), which is described with erosion rates of about 0.5 feet/year (0.14 meters/year). However, it is important to note that the coastline is highly variable in regard to shoreline and bluff stability, therefore, overall retreat rates should be expected to be highly variable. For instance, a bluff setback analysis undertaken by SHN for a private residence estimated a historical bluff retreat rate of 0.12 feet/year at the border of the Wagner and Scenic bluff segments (SHN, 2016a). Bluff erosion is site specific and is not only subject to annual erosion rates but also episodic events.
Figure 5-3 California coastal cliff erosion viewer; data shown as red dot (Scripps Institute of Oceanography Coastal Processes Group, 2022)
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 25 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The coastal bluffs and associated landslide hazards in the Planning Area have been mapped by SHN and evaluated by segments (SHN, 2019a). A primary take-away from these studies has been that the landslide hazards in the Planning Area are strongly linked to the geologic setting and the materials exposed in the bluff face. The lower part of the bluffs are expose bedrock described as a tectonic mélange, which is a chaotic mixture of rootless rock blocks within a matrix of sheared shale and serpentinite. In general, the stability of this material will vary depending on the distribution of bedrock blocks. The segment identified with the highest landslide hazard is the Edwards segment located along the South Bluff and the Tsurai Study Area, which is described in further detail below.
West Bluff
The West Bluff (north of Trinidad Head / Tsurewa) is 80 to 100 feet in elevation and is fronted by the relatively stable Trinidad State Beach. Landslide hazards in this segment are dominant in the upper portions of the slope; however, the retreat rates are relatively low compared to the other bluff sections in the City. As such, the infrastructure backing this segment was noted by SHN (2019a) to have a relatively low vulnerability to erosion under current conditions.
South Bluff
The South Bluff segments and the Tsurai Study Area are generally fronted by narrow beaches that are exposed to wave action refracting around Trinidad Head during periods of heavy winter surf. The Edwards segment, described as the most unstable bluff area under current conditions, is 60 to 150 feet in elevation and is subject to large earthflows across the entire bluff face. This landslide was active in 2017/18 and the during past winter season (2023/24). Due to the narrow beach and low littoral sediment input, the Edwards Street bluff is particularly vulnerable to bluff retreat under SLR. The Wagner segment exhibits similar geologic and topographic conditions to that of the Edwards segment; however, it is not subject to active landslides and a terrace is present, which buffers high surf conditions.
The Scenic segment is subject to localized mass wasting that is dependent on the distribution of rocky headlands and low strength mélange matrix. The active earthflows per SHN (2019a) are shown below in Figure 5-4, which highlight the vulnerability of the infrastructure backing the Edwards Bluff segment.
Figure 5-4 Active earthflows along the south bluff (SHN, 2019a)
5.2.1 Climate Projections & Bluff Erosion
The climatic processes discussed in this report that will have the greatest impact on bluff erosion include SLR and precipitation changes as related to local hydrology and geology. It is expected that future SLR will increase cliff retreat GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 26 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. rates (Dickson, Walkden, & Hall, 2007); however, limited projections / estimates are available for the Planning Area.
Surface runoff and groundwater flow can impact bluff stability, although the extent of precipitation-related impacts are also difficult to predict. The landslide potential at the previous Trinidad Memorial Lighthouse site was examined by SHN, finding that two consecutive wet seasons had exposed the upper portion of the landslide complex (SHN, 2017b).
As more intense rainfall is expected over short time periods with climate change, the groundwater flow and soil saturation through the bluff faces may be monitored to better inform the magnitude of these contributions.
Based on the relationship between wave action, shoreline erosion, and bluff hazards, the general future conditions with SLR can still be assessed. As stated above, the West Bluff segment is fronted by a wide, arguably accretionary beach that serves as a buffer for high surf. The Trinidad Head / Tsurewa blocks the southernly flow of sand, allowing sand to accumulate between Mill Creek and the headland. This accretionary process was also noted by SHN (2019a), which stated that Trinidad State Beach is generally stable except under extreme winter conditions. The South Bluff segments contain narrow beaches that are still subject to high surf, despite the sheltering from the Trinidad Head / Tsurewa. With SLR, it can be expected that waves will begin to approach and attack the bluff toe more regularly, resulting in increased retreat rates and bluff failure.
The relationship between SLR and bluff erosion is a topic that is becoming more widely studied throughout the state of California. For example, the U.S. Geological Survey (USGS) operates and publishes the Coastal Storm Modeling System (CoSMoS) for central and southern California, which examines various processes and hazards (i.e., shoreline erosion, bluff retreat, flooding) with future SLR. CoSMoS is a regional model and provides projections for cross shore transects spaced approximately 100 meters along the coastline. The northern California CoSMoS data was released in December of 2022 and provides coastal cliff retreat projections due to 21st century SLR (Barnard, et al., 2022). The hazard data available is available in 0.8 feet (25 cm) increments from 0 to 6.6 feet (200 cm) and an extreme scenario of 16.4 feet (500 cm). Since the CoSMoS results are only available in discrete increments, the data used to estimate coastal hazards may not precisely correlate with the SLR projections discussed above in Section 4.1 However, the differences between the nearest CoSMoS data increment and the SLR projections are insignificant when considering the uncertainties in predicting SLR and coastal hazards over the long term.
The CoSMoS model is intended for planning purposes, as a way to identify areas of further investigations, and results should not be interpreted for site-specific Projects. In general, numerical modeling of bluff evolution or any coastal processes is imprecise due to the complexity of mathematically describing intricate dynamics of coastal processes.
Regional scale models will typically require further parameterization and assumptions of processes for ease of computation over a large area. Thus, there will likely be differences among regional model results and site-specific hazard mapping.
The CoSMoS inputs and assumptions are important to recognize when interpreting the results. The model relies on historical retreat rates derived from USGS T-Sheets and aerial imagery, which produces an end point rate that does not necessarily account for episodic erosion. Additionally, the model simplifies geology and erodibility of bluff material at a regional scale and does not include the effects of precipitation or hydrology and associated soil saturation. In the Planning Area, geology and precipitation / localized runoff have been found to play a significant role in the evolution of the bluff face. Local observations and more site-specific studies indicate significant differences in anticipated bluff retreat from those presented by the USGS CoSMoS cliff retreat model.
The USGS CoSMoS cliff retreat projections are shown below in Figure 5-5 for 1.6 (0.5 meter), 3.3 (1 meter), and 6.6 feet (2 meters) of SLR for the purposes of discussion and a general indication of potentially vulnerable areas. Sitespecific characterization and analyses are needed in this area to more accurately estimate bluff erosion.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 27 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 5-5 CoSMoS cliff retreat projections (Barnard, et al., 2022) In comparison to the site-specific hazards and vulnerability assessment performed by SHN (2019a), the CoSMoS bluff retreat projections suggest an underrepresentation of bluff retreat along the Edwards segment and likely overestimate retreat of the western bluff. Shown below in Figure 5-6, the CoSMoS bluff edge is aligned lower along the bluff face than that of the bluff edge surveyed by SHN. In addition, the corresponding retreat rates are relatively low compared to the adjacent bluffs (Trinidad State Beach / West Bluff). This discrepancy is likely a result of the bluff edge mapping methods and wave climate model input as it relates to shoreline orientation. That is, the bluff edge along gradually sloping faces can be difficult to pinpoint from aerial imagery and topography (Hapke & Reid, 2007). A primary erosional element in the CoSMoS bluff retreat projections is wave attack along the bluff toe. The Trinidad Head / Tsurewa shelters the Edwards segment bluffs from energetic fall / winter swell approaching from the northwest and west. It is understood that runoff, groundwater, and geology are very influential for bluff movement and these elements are not included in CoSMoS.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 28 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 5-6 USGS CoSMoS projections and local geologic hazard mapping Changes to precipitation patterns may impact the future bluff retreat rates. While the bluff toe is exposed to wave attack and SLR, rainfall generally impacts the bluff face. As mentioned in Section 4.2, precipitation events may become more extreme, with intense wet years and extreme dry years. More intense rainfall events or prolonged wet seasons may impact the overall bluff retreat rates, although the total extent of precipitation-related erosion is difficult to quantify with the available data. SHN (2019a) noted that the past several winters were associated with above average rainfall and the earthflows in the Edwards segments experienced significant movement. It is recommended that public resources provided by state and federal agencies be monitored and utilized for future assessments and planning. As data improves, so will the models.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 29 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
5.3 Coastal Flooding
Ocean water levels typically vary within predictable astronomical tide ranges; however, sea level anomalies caused by El Niño Southern Oscillation or storm surge events can increase the water levels above the predicted astronomical tide. These events in combination with high astronomical tides can result in extreme water levels and increased potential for flooding of low-lying areas.
Extreme ocean water levels are provided by the Federal Emergency Management Agency (FEMA) for the Planning Area. FEMA conducts Flood Insurance Studies (FIS) that provide extreme water level estimates, termed Stillwater Elevations, or SWEL. SWEL in the open ocean is defined by FEMA as water levels attributed to astronomical influence and other sea level anomalies but do not include the dynamic effects of wave setup and runup, which occur through the surf zone and beach areas. The SWEL is comparable to the extreme water levels provided by NOAA.
FEMA conducted a FIS for Humboldt County, which provides SWEL estimates at various locations along the coast (BakerAECOM, 2014). The calculated SWEL most relevant to the Planning Area (North Spit) is estimated at 9.2 feet for a 10-year return period and 10.2 feet for a 100-year return period. These values are generally consistent with the extreme water levels provided by NOAA for Crescent City, located approximately 50 miles north, with the two locations bracketing the Planning Area. SWEL estimates for a range of return periods are provided in Table 5-1.
Table 5-1 Regional SWELs (BakerAECOM, 2014)
Location/Tide
Gauge
50% Annual
Chance
20% Annual
Chance
10% Annual
Chance
4% Annual
Chance
2% Annual
Chance
1% Annual
Chance
0.2% Annual
Chance
2-yr Return
Period
5-yr Return
Period
10-yr Return
Period
25-yr Return
Period
50-yr Return
Period
100-yr
Return
Period
500-yr
Return
Period
North Spit 8.5 8.9 9.2 9.6 9.96 10.2 11.0
In an effort to relate SWELs, return period, and projected SLR, Table 5-2 was developed. The return period of an event is an important part of establishing vulnerability and planning for adaptation and design. The table shows that with SLR, the current return period of extreme water levels will decrease and what is considered an extreme water level today will eventually become a more regular occurrence. For example, the water level of 10.5 feet is the current, approximate 100-yr water level (1% chance of occurring each year) and is the Tide of Record that would be expected to occur on average every 2 years (50% chance each year) with 2 feet of SLR. Depending on the elevation of coastal infrastructure and other results of higher, more frequent water levels, this may or may not be a hazard.
Table 5-2 Approximate Current and Future Tidal Datums
Time 6.5 ft 7.5 ft 8.5 ft 9.5 ft 10.5 ft 11.0 ft
Current MHHW 2-yr, Max Tide 25-yr 100-yr, Tide of
Record
500-yr
Future MHHW+1ft MHHW+2ft MHHW+3ft
2-yr, Max
Tide+1ft
MHHW+4ft
2-yr, Max Tide+2ft
25-yr+1ft
MHHW+5ft
2-yr, Max Tide+3ft
25-yr+2.4ft
50-yr+1ft
100-yr+0.8ft
Water levels that include wave setup and runup are defined as total water levels, or TWL. The TWL represents the “limit of swash” as waves approach the shoreline and is temporary. The components of the TWL are shown below in Figure 5-7. TWL is included in some FEMA flood zone classifications for coastal areas. For example, the Planning Area shoreline is located in Flood Zone VE, which is defined by FEMA as a coastal area subject to storm waves (i.e., wave runup) and with a 1% annual occurrence probability (100-year storm). FEMA calculated TWLs for three transects within the Planning Area, which are shown below in Table 5-3 and Figure 5-8. The 100-year storm TWL ranges from 18.1 feet at Trinidad State Beach to 24.5 feet at the southern extent of the Planning Area.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 30 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 5-7 Components of wave runup (BakerAECOM, 2014)
Table 5-3 Total Water Levels for Trinidad Beaches (BakerAECOM, 2014) Transect No. / Location 10% Annual
Chance
2% Annual
Chance
1% Annual
Chance
0.2% Annual
Chance
10-yr Return
Period
50-yr Return
Period
100-yr Return
Period
500-yr Return
Period
Transect 13 / Trinidad State Beach 15.8 17.4 18.1 19.5
Transect 14 / Launcher Beach 17.8 20.1 20.9 22.4
Transect 15 / Unnamed Beach 21.3 23.6 24.5 26.3
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 31 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 5-8 FEMA flood zones and coastal transects (effective map date 6/21/2017) The TWLs shown above are estimated by adding the SWEL and the wave runup for each transect. The differences in TWL from transect 13 to transect 15 is largely due to the existence of a beach within the cross-shore profiles used to calculate runup. For instance, the toe of the bluff for transect 13 (Trinidad State Beach) is located at an elevation of approximately 18 feet, while the bluff toe elevation for the transects south of the Trinidad Head / Tsurewa is approximately 10 feet. That is, the beach present at transect 13 serves as a buffer to incoming waves, while waves break further (landward) along the profile at transects 14 and 15.
Based on the FEMA Flood Insurance Rate Map (FIRM), a portion of the Harbor-Pier area is vulnerable to coastal flooding, due to wave runup, under a 100-year storm scenario. The flood pathway follows the lower-elevation shoreline in the vicinity of the harbor and pier. However, with SLR, it is expected that any flooding may increase in extent and generally follow the same pathway. The 100-year TWL with a range of SLR projections, for the likely, moderate risk GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 32 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. aversion, and medium-high risk aversion are shown below in Table 5-4, Table 5-5, and Table 5-6 respectively. The 100-year TWLs with SLR may range from 19.6 - 20.4 feet in 2050 to 22.2 - 25.7 feet in 2100 for Trinidad State Beach and 22.4 - 23.2 feet in 2050 to 25.0 - 28.5 feet in 2100 for Launcher Beach.
Table 5-4 FEMA Base Flood Elevation (BFE) with Future “Likely Range” SLR Projections Transect No. / Location Existing BFE 2050 2070 2100
0.0 ft SLR 1.5 ft SLR 2.4 ft SLR 4.1 ft SLR
Transect 13 / Trinidad State Beach 18.1 19.6 20.5 22.2
Transect 14 / Launcher Beach 20.9 22.4 23.3 25.0
Transect 15 / Unnamed Beach 24.5 26.0 26.9 28.6
Table 5-5 FEMA Base Flood Elevation (BFE) with Future “Moderate Risk Aversion” SLR Projections Transect No. / Location Existing BFE 2050 2070 2100
0.0 ft SLR 1.7 ft SLR 2.9 ft SLR 5.1 ft SLR
Transect 13 / Trinidad State Beach 18.1 19.8 21 23.2
Transect 14 / Launcher Beach 20.9 22.6 23.8 26
Transect 15 / Unnamed Beach 24.5 26.2 27.4 29.6
Table 5-6 FEMA Base Flood Elevation (BFE) with Future “Medium-High Risk Aversion” SLR Projections Transect No. / Location Existing BFE 2050 2070 2100
0.0 ft SLR 2.3 ft SLR 4.0 ft SLR 7.6 ft SLR
Transect 13 / Trinidad State Beach 18.1 20.4 22.1 25.7
Transect 14 / Launcher Beach 20.9 23.2 24.9 28.5
Transect 15 / Unnamed Beach 24.5 26.8 28.5 32.1
It should be noted that the existing OPC and CCC SLR guidance does not provide input on SLR projections combined with other coastal hazards such as an extreme storm or surge event. The combination of SLR and storm events should be further evaluated so that the project design assumptions are in line with the community’s risk tolerance and long-term management strategy.
5.4 Fluvial Flooding
FEMA has developed FIRMs that identify Special Flood Hazard Areas (SFHAs), which are defined as areas with a 1% or greater chance of flooding in any given year (100-year return period or less). Base flood elevations (BFEs) are shown within the SFHAs where detailed studies have been conducted. Other areas may be approximated and not identify BFEs. Non-SFHAs are areas of moderate to low flood risk. FEMA’s flood mapping and hazards analysis provide an overview of potential flood hazards for communities. The City of Trinidad does not participate in the National Flood Insurance Program (NFIP) and did not opt to participate in FEMA’s flood mapping program; therefore, detailed flood risk within the Trinidad city limits has not been established. This is reflected in the FEMA flood maps as Zone D, or areas with undetermined flood risks. This is described in further detail below.
A portion of the Mill Creek watershed, a historical impoundment no longer active, is the only mapped fluvial flood source in proximity to the Planning Area (Figure 5-8). Mill Creek meanders through the northeast and northern portions of the developed areas, discharging into the ocean near the northern extent of Trinidad State Beach. The mapped area is classified as Zone A, which is defined as an area with a 1% annual chance of flooding but does not have an estimated BFE. Although multiple creeks discharge to the ocean along the shoreline of the Planning Area, GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 33 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. much of the upslope areas have not been evaluated for flooding, classified as Zone D, which is an area with undetermined flood hazards.
Fluvial flooding may result from high river flows triggered by an extreme rainfall event. Although no BFE has been calculated by FEMA, the significant elevation difference and steep topography between ocean water levels and the present-day creek elevation / flood zone suggests that it is unlikely that SLR will have a significant influence on extreme fluvial hazards. This is because the energy differential between the fluvial BFE and the ocean water levels with the addition of SLR is still great enough that substantial changes in the floodplain would not be anticipated.
Floodplain impacts would be anticipated in situations where ocean water levels are closer to equal to or greater than the BFE, which would result in water backing up within the floodplain. Extreme rainfall events will more likely have a direct effect on flooding in higher elevation areas and contribute to erosion along the channels and at road crossings.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 34 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6. Planning Area Resources
The Planning Area contains a variety of resources. The term “resource” is broad, in that it includes both natural and anthropogenic elements that play a significant role in the community. These Planning Area and coastal resources include but are not limited to:
a. Public access and recreation resources
b. Critical public service resources
c. Critical public infrastructure and distribution system resources d. Cultural, historic, and natural, and scenic resources e. Future resources
The purpose of this section is to discuss and inventory the existing resources within the Planning Area that could potentially be impacted by climate change and the coastal hazards outlined in previous sections.
6.1 Public Access and Recreation Resources
Public access resources include recreational activities and trails, beach accessways or paths, parking lots and restrooms, or other associated amenities (Figure 6-1). There are a number of recreational activities that are of importance to the community, most of which are connected to the environment. For example, surfing, fishing, boating, and hiking are recreational activities that the community has identified as significant and should be considered resources. Recreational resources may also include more generalized areas that support various activities, such as trails and open spaces.
The Harbor Properties are owned, funded, and operated by Trinidad Rancheria. The public parking lots that provide primary coastal access are located just east of the Trinidad Head / Tsurewa and provide access to Trinidad State Beach, Harbor Properties, and Launcher Beach. The parking lot adjacent to Trinidad State Beach is an unmarked and unpaved gravel lot, while the nearby Harbor Properties/Pier parking lot is paved. The accessways from the parking lot to the beach are largely unpaved, dirt or sand paths. Additional parking is available along roadways that provide access to trail heads. The Trinidad Rancheria operates and maintains public restrooms for the community at its own expense and supports public access and the recreational resources that the Harbor offers.
There are several recreational trails within the Planning Area. Trails are often the primary way to access the beach due to steep bluffs, dense vegetation, and rocky terrain. Trails require special consideration of both their cultural and recreational values (Yurok Tribe Environmental Program, 2007). Along the South Bluff and Tsurai Study Area, there are four (hiking) trails that exit to the beaches. There are two trails that exit to Trinidad State Beach along the West Bluff. Due to the bluffs and terrain, these trails are generally steep and cut through dense vegetation. In addition, because many of the beaches are pocket beaches and separated by headlands, lateral beach access may be limited during higher tidal water levels.
The Trinidad Coastal Land Trust is an organization that manages properties and easements to provide coastal access to recreational and natural spaces. In total, the land trust manages 26 properties and easements, many of which are beaches or trails that serve as coastal access points.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 35 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 6-1 Public access resources
6.2 Critical Public Infrastructure and Services
Infrastructure and services are exposed to the impacts of climate change. Disruption or damage of infrastructure and services can pose public health, safety, and environmental issues. It is important to document and evaluate the existing assets and resources that could potentially be impacted. The critical infrastructure resources and services within the Planning Area generally consist of:
• Roadways
• Emergency services
• Raw water (drinking water and fire suppression)
• Water distribution system
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 36 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. • Stormwater system
• Wastewater
• Gas, electric and communications
• Trinidad Harbor-Pier
• Public amenities
6.2.1 Roadways
The public streets and roadways within the Planning Area are maintained by the Public Works Department. The public roadways are key gateways for access to the coastal resources within the Planning Area. In particular, the short segment of Edwards Street, between Hector Street and Van Wycke Street, is the only vehicle access between two areas. Any residents or visitors originating north or east of the intersection of Hector Street and Edwards Street must travel on this section of roadway to access the area that encompasses beach access / parking lots, harbor, pier, Van Wyck Street, Gallindo Street, Pacific Court, and Ewing Street. Damage or disruption to this roadway segment could sever vehicular ingress and egress capabilities.
The roadway that serves as the primary access route to and from the Planning Area is Highway 101 (Redwood Highway). This highway traverses the eastern portions of the Planning Area, although it is located fairly close to the coastline / bluff edge to the north and south of the Planning Area. There are a number of smaller roads that could also serve as access to the Planning Area from the north; however, due to the limited routes available, Highway 101 is of particular importance to the community members because it provides the only access to the south from the Planning Area (there is no public access to / from the east other than private logging roads). Additionally, the Planning Area could be isolated with disruption to Highway 101 access at Big Lagoon to the north and Little River to south, both lowlying areas subject to future sea level rise and fluvial flooding.
A secondary, yet popular and essential route, is Scenic Drive, which extends from the City of Trinidad to Moonstone Beach County Park to the south. The majority of this road is located fairly close to the bluff edge and provides access to several coastal viewpoints and beaches, but sections are commonly closed or limited to one-lane traffic due to erosion and hazardous conditions. In addition, Scenic Drive is the main route to the coastal Trinidad Rancheria and many residential homes. Due to the proximity to the bluff edge, the stability of the bluff is particularly important to the longevity of Scenic Drive.
6.2.2 Emergency Services
Emergency services are key components to the wellbeing of the community and should be considered as critical assets and infrastructure. These services include but are not limited to the fire department, police department, medical facilities, and tribal resources located at Trinidad Rancheria. The Planning Area is served by three fire facilities: the City of Trinidad Volunteer Fire Department, the Westhaven Volunteer Fire Department, and the California Department of Forestry and Fire Protection (CAL FIRE). Trinidad is served by the Humboldt County Sheriff’s Office. The nearest hospital to the Planning Area is the Mad River Hospital, located approximately 12 miles to the south. During recent power outages Trinidad City Hall has been used as an emergency charging location.
6.2.3 Gas, Electric and Communications (Private Utilities) PG&E provides electric services to the Planning Area, while on-site propane is provided by various providers. AT&T and Optimum provide communications services. Individual gas tanks accompany private homes or buildings and are privately owned. Detailed information regarding private utility systems is not publicly available for planning studies.
This information is generally only made available for active construction projects with ground disturbing activities.
Electric and communications facilities are assumed to primarily follow roadway and public right of way alignments.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 37 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6.2.4 Raw Water (Drinking Water and Fire Suppression) Supply A 2008 Preliminary Watershed Assessment conducted by Streamline Planning provides a detailed review of the surface water resources, land use, water quality, and climate of the Trinidad-Westhaven coastal watershed that is summarized below (Streamline Planning, 2008). This coastal watershed area extends south to (but not including) Little River and north to Mill Creek, which flows through the City of Trinidad. Watersheds to the north of the City are not included.
The Trinidad-Westhaven coastal watershed experiences a Mediterranean climate with approximately 90% of the annual precipitation occurring as rainfall between the months of October and April. Rainfall measurements collected from the California Redwood Coast-Humboldt County Airport and Sue-Meg State Park (formerly named Patrick’s Point) suggest that annual precipitation ranges from 50 to 80+ inches in the watershed. The mean annual temperature is reported as approximately 55 degrees F.
The watershed consists of nine sub watersheds. There are no lakes or reservoirs within the watershed and the primary freshwater sources are the eight streams that drain the sub watersheds. However, the only two streams large enough to supply a source of fresh water for municipal supply are Mill and Luffenholtz Creeks. Mill Creek is no longer used for municipal supply due to sedimentation issues, which are discussed in subsequent sections. The Mill Creek watershed includes approximately 856 acres of residential and timber land that drains through Mill Creek to the Pacific Ocean on the north side of Trinidad Head / Tsurewa. The Luffenholtz Creek watershed includes approximately 3,163 acres of residential and timber land, including approximately half of the Westhaven Community. Luffenholtz Creek drains into the Pacific Ocean at Luffenholtz Beach, south of Trinidad Bay.
There are three primary drinking water suppliers in the Trinidad-Westhaven coastal watershed, including the City of Trinidad, Westhaven Community Services District (WCSD), and Moonstone Heights. Together, over half of the watershed receives drinking water through these entities. The remaining residents rely on private groundwater wells or localized springs. Drinking water in the City of Trinidad is supplied by the City of Trinidad. Luffenholtz Creek is the sole source of raw water for the City of Trinidad and the City diverts approximately 30 million gallons annually to support drinking water needs. The City’s drinking water system serves approximately 310 hook-ups, including customers in the City of Trinidad, Trinidad Rancheria, and some community of Westhaven residents. WCSD’s raw water supply comes from local springs and a groundwater well and serves approximately 210 households in the community of Westhaven.
The Westhaven CSD is in the process of planning and implementing several water system improvements. Moonstone Heights utilizes local springs as raw water source for drinking water and serves approximately 15 connections.
Water Supply Diversion and Luffenholtz Creek Streamflow Luffenholtz Creek is the sole source of raw water for the City of Trinidad’s drinking water system. However, the City of Trinidad’s original water reservoir was located on Mill Creek. After severe forest fires in the 1930s-1940s subsequent sediment erosion and deposition resulted in aggradation of the reservoir in the Mill Creek reservoir in the 1950s-1960s (Madrone, 2008) The City then developed the water supply operation on Luffenholtz Creek. The City’s current diversion and water plant is located at 1313 Westhaven Dr. in Trinidad, CA, adjacent to Luffenholtz Creek (GHD, 2019). Fresh water is pumped from a wet well that is filled through an infiltration gallery that is installed approximately 10 feet below the creek bed. The City’s appropriative water rights specify the rate of diversion, the annual maximum diversion, and the required bypass flow requirements (permit 17255). The bypass flow requirement is the minimum flow rate that must be allowed to bypass the water intake.
Through the appropriative rights, the City can extract a maximum of 0.56 cubic feet per second (cfs), which is equivalent to 251 gallons per minute (gpm) (GHD, 2019b). This corresponds to a daily maximum extraction of 361,440 gallons per day. However, the water right stipulates that the City shall bypass 0.25 cfs under normal streamflow conditions (streamflow above 0.86 cfs). When the natural streamflow in Luffenholtz Creek is lower than 0.86 cfs then the City must leave at least 0.15 cfs in the creek. In addition, the City must leave 0.0054 cfs in the creek to provide for the existing water rights downstream of the City operation. Therefore, the City must bypass a total of 0.1554 cfs or approximately 70 gpm during low flows below 0.86 cfs.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 38 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Water losses, especially from large leaks or demand from firefighting flows, could cause water service interruptions due to difficulty pumping to replenish the two 150,000-gallon redwood water tanks, which hold approximately 2-3 days of water at normal demand levels.
The water supply is especially impacted during the dry season. Each year, the water system is threatened by low flows in Luffenholtz Creek. The creek flows decline in June through October until the rainy season begins. The watershed is experiencing changing precipitation patterns, with more runoff and less percolation, as well as higher average temperatures and less fog. These patterns reduce dry period flows and may also change water demand characteristics. Drought, made more frequent and severe by climate change impacts, further exacerbates the system's ability to pump from the creek to ensure adequate water to meet regular demands. In 2020 and 2021, flows dipped to curtailed extraction levels in late August. In September 2021, the City enacted the Water Shortage Contingency Plan (adopted in 2021) Stage 2 Water Shortage Warning with a mandatory water use restriction. Even when pumping restrictions are not needed to provide the minimum bypass flows, normal pumping regimes are difficult during low flows, as discussed below.
Water Quality Impacts to Supply
Water quality issues in Luffenholtz Creek are a known issue for the water supply operation. Water quality issues in Luffenholtz Creek include turbidity, tannins from decaying wood and organic matter, and some septic runoff pollution (Madrone, 2008). Currently the raw water that is extracted from Luffenholtz Creek is pumped from the wet well to a flocculator where polymer is added to aid in particulate clumping and settling to reduce turbidity (GHD, 2019). Then the water is pumped through a series of filters with additional polymer and finally through a chlorination pipe prior to entering the water distribution system.
The City measures the flow in Luffenholtz Creek with a stream gauge located directly below the City’s point of diversion. The City has used the stream gauge to conduct flow studies investigating if the legal water-right conditions, infiltration gallery intake limits, or treatment plant components are limiting factors for potable water production (GHD, 2019b). The results of these analyses suggest a primary limiting factor for potable water production is turbidity breakthrough in the treatment filters. This is especially an issue during the winter storm period when streamflow increases, raising the turbidity. The raised turbidity causes the filters to clog, resulting in the need to backflush filters. A second primary limiting factor is the fine particles in the turbid streamflow clogging the void spaces between the gravels and causing a restriction of downward flow from the streambed into the infiltration gallery, thereby causing a reduction in the water elevation in the wet well. The volume of water that can be pumped from the wet well and treated for drinking water supply is directly impacted by reduced water elevation in the wet well.
A 2011 master's Thesis, “Fine Sediment Sources in Coastal Watersheds with Uplifted Marine Terraces in Northwest Humboldt County” specifically studied the historical land uses, potential sources of sediment input and stream turbidity in Mill and Luffenholtz Creeks (Madrone, 2011). This study found that Mill Creek has steeper average slopes, greater basin relief, a higher rate of recent timber harvest, and more severe fire history, but it has lower turbidity than Luffenholtz Creek. The study suggests that this could be attributed to Luffenholtz Creek having slightly higher density of roads per square kilometer, higher total kilometers of roads, more roads made of native surfaces, and more sites of active erosion. These watershed characteristics are likely going to continue contributing sediment and organic matter to Luffenholtz Creek, thereby continuing to cause turbidity issues with water extraction at the City’s extraction well and water treatment plant.
Summary of Historical Low Flow Conditions
A Conceptual Hydrological Assessment of the Luffenholtz Creek Watershed was completed by GHD for the City of Trinidad in 2019 (GHD, 2019d). A summary of historical low flow conditions on Luffenholtz Creek from that report is summarized below.
The water supply in the watershed that feeds Luffenholtz Creek varies throughout the year based on weather patterns, extractions, soils and geologic characteristics, surface and groundwater characteristics, and other factors. As is typical in the region, winter rains increase the flow in Luffenholtz Creek as directly related to individual storm events and over time as related to seasonal accumulation of precipitation in the region.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 39 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The peak flow events and seasonal high flow patterns supply ample water for many uses in the watershed. It is the low flow summer period, however, that is of most interest from a water supply standpoint as that is when water supply could become scarce and the City could see flows drop to a level where the City’s allowable extraction could be curtailed.
The following low flow conditions have historically been reported for Luffenholtz Creek:
• A 1980 Trinidad Citizen’s Report estimated the critical low flow in the creek at 300 gpm (0.67 cfs), which is 432,030 gallons per day (gpd), based on 80 years of precipitation data in Eureka and Luffenholtz Creek low flow measurements in 1968 and 1977. The 1980 Citizen’s Report also stated the lowest recorded flow in Luffenholtz Creek in the 1977 drought was 310 gpm (0.71 cfs). The frequency or method of the collection of these flow data is not known.
• The Arcata Union newspaper ran an article about the 1977 drought in its September 8, 1977 issue. The Trinidad Public Works Director at that time, Tom Nelson, told the paper he measured the flow in Luffenholtz Creek at 284 gpm (0.632 cfs). According to the article, the City had earlier predicted that Luffenholtz Creek would stop flowing by the end of August, but that long periods of foggy weather and small amounts of rain were keeping the creek flowing. No record of the creek going dry at this time have been found. This article highlights the potential low flow conditions the City of Trinidad may confront in the future during drought conditions, which could be further exacerbated by climate change and other extractions from the watershed. • The City set up a weir in the early 1990s that was destroyed in a 1997 flood. Only one small data set from the fall of 1994 exists. The 1994 data is based on measuring the flow just below the intake of the water plant and the total flow was calculated by adding the water plant flow to the measured flow. The 1994 flow data ranged from 421 gpm to 466 gpm (0.94 cfs to 1.22 cfs).
• A new weir was constructed downstream of the water plant intake in the summer of 2001 for collecting data.
Preliminary data from September of 2001 indicated that without the water plant pumps running, the creek flow was approximately 313 gpm (0.70 cfs). This flow value is just under the City of Trinidad’s water right plus bypass requirement.
6.2.5 Water Distribution System
As described in Section 3.5, the source water for the Planning Area is the Luffenholtz Creek. The water distribution and supply system in the Planning Area is comprised of an infiltration gallery, a treatment plant, storage tanks, and a network of distribution pipes (water mains) (Figure 6-2). The system serves approximately 1000 people within the service area, with 354 service connections in and around the Planning Area (LAFCO, 2021).
The Trinidad Water Treatment Plant and infiltration gallery is located approximately two miles south of the City along Luffenholtz Creek. Treated water is stored in two nearby 150,000-gallon water tanks, which reserve between one and two days of water without the treatment plant in operation (LAFCO, 2021). In addition, approximately 180,000 gallons of water are reserved for fire operations (LAFCO, 2021). Water is then distributed to residential and commercial properties via a network of water mains. The network was experiencing losses of around 24% to 31%, which exceeds the typical system losses of 10% to 20%. This loss is likely due to aging infrastructure and associated leaks (GHD, 2019). The City of Trinidad and Westhaven Community Services District are currently designing and implementing an intertie to the systems to improve water resource resiliency in the two communities.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 40 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 6-2 Water distribution system
The maximum authorized take of water is 0.56 cfs, or 251 gpm (LAFCO, 2021). The actual extraction rate varies based on demand and the flow conditions of the Creek, for which low flow and turbid conditions both present challenges. Low flow conditions limit the available pumping capacity and prolonged low flow conditions may lead to water supply issues. High turbidity results from intense precipitation and limits the system capacity to treat water.
Changes in precipitation patterns, such as increased storm intensity and decreased annual precipitation, have the potential to complicate existing issues. Given limitations of water supply, the Humboldt Bay Municipal Water District and the Trinidad Rancheria have conducted a feasibility study to investigate the possibility of extending water service from McKinleyville north to the Rancheria.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 41 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6.2.6 Stormwater
The City storm drain infrastructure routes stormwater runoff through a series of roadside ditches, drain inlets, and culverts, as well as recently implemented infiltration galleries. This infrastructure is focused in the more densely developed area of the City. The original stormwater system was designed to capture and convey runoff to a single outfall at the Trinidad Boat Launch and thus a significant amount of runoff was directed into the ASBS. Recent improvements to the stormwater infrastructure have been completed as part of the City’s Stormwater Management Improvement Project and the outfall at the Trinidad Launcher Beach has since been decommissioned to be in compliance with the California Ocean Plan prohibition of waste discharges into ASBS / State Water Quality Protection Areas (SWQPA). Stormwater system components installed as part of the Stormwater Management Improvement Project have been designed to eliminate stormwater discharge by strategically infiltrating it at various locations that will not impact bluff stability (LAFCO, 2021).
Trinidad Rancheria owns and operates the Harbor Properties and has eliminated all but one stormwater discharge into the ASBS, which is currently scheduled to be removed in the summer of 2024. The modification will convey parking lot stormwater runoff into rain gardens and bio-swales to capture stormwater and remove pollutants. Upon completion of this project, the Trinidad Harbor will be in compliance with the California Ocean Plan prohibition of waste discharges into ASBS / SWQPA, the Trinidad Rancheria’s ASBS Compliance Plan, and the Waterfront and Marine Operations Nonpoint Source Management Plan.
In the northern portion of the City, stormwater runoff is conveyed to Mill Creek, while in the central portion of the City stormwater is conveyed to multiple infiltration galleries located at multiple locations with one located in the Trinidad State Beach Parking Lot (Figure 6-3). However, some areas, such as Wagner Street, have no curbs or drain inlets, so drainage is generally south toward the bluff areas or toward Parker Creek (LAFCO, 2021). Furthermore, surface drainage and run-off emanating from neighboring and bluff top residences is a contributing factor affecting slope stability at the Tsurai Village site (LACO and Associates, 2004). During LACO’s field investigation, several locations were identified where discharge of surface run-off is directly affecting Tsurai Village in an adverse manner. A slot drain that collects surface runoff on the paved roadway accessing the Wagner Street Trail is also likely to discharge concentrated runoff to the slopes below. Concentrated discharge, as discussed previously, increases erosion of the slope and contributes to slope instability. To avoid uncontrolled surface run-off causing erosion and contributions to slope instability the implementation of drainage collection structures, tightlines, and properly located points of discharge were recommended.
Mitigation of these problem areas will not only benefit Tsurai Village but will also benefit bluff top landowners by minimizing the potential for slope instabilities to occur ( (LACO and Associates, 2004); (Yurok Tribe Environmental Program, 2007)). As a result of the findings in LACO 2004, the City, in partnership with the Tsurai Management Team and funding from the Coastal Conservancy, installed drainage improvements below Wagner Street, adjacent to Parker Creek, at a private residence to eliminate the primary direct source of erosion identified in the Tsurai Management Plan. Additional projects are needed to reduce runoff and erosion. The existing stormwater infrastructure, within Cityowned and public right-of-way is shown below in Figure 6-3.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 42 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 6-3 Stormwater resources
Common to most urban stormwater systems, the conveyance pipes and inlets generally follow the roadways. The primary conveyance pipes are located along Edwards Street, which follow Galindo Street to Lighthouse Road and to the infiltration basin at the Trinidad State Beach Parking Lot. This pathway also includes a number of treatment chambers. This portion of the system is especially significant, as it alleviates the untreated runoff into the ASBS. In addition, this infiltration basin is situated relatively close to the shoreline, buffered by a 40- to 80-foot dune strand and at higher elevation.
6.2.7 Wastewater
Wastewater systems for residents and businesses within the Planning Area primarily consist of on-site wastewater treatment systems (OWTS). There are approximately 200 septic systems within the City and more around the GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 43 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Planning Area, many of which were installed prior to the development of permit requirements (Trinidad Regional Water Management Working Group, 2008). The OWTS are at a relatively high density I some locations. Current County Department of Environmental Health regulations require a minimum of one acre for new lots that will be served by OWTS and public water. In Trinidad, most residential lots are smaller than 0.25 acres (LAFCO, 2021). These septic systems are generally buried at a depth of 1 to 3 feet below ground surface (BGS) with leach lines between 3 and 5 feet BGS in a gravel filled trench (GHD, 2013). Although the City is managing OWTS and improving water quality, significant increases in development and density in the City is not feasible with the use of OWTS (LAFCO, 2021).
The LACO 2004 study indicates that the model used to describe the potential for slope failure was the most sensitive to increases in groundwater surface elevation (LACO, 2004). Additionally, high groundwater conditions coupled with strong earthquake ground shaking was determined to have the highest probability of producing a mass wasting landslide event. Therefore the primary concern for slope stability at Tsurai Village is higher groundwater levels. At the time of the LACO 2004 field work groundwater level indicators and understanding that the Tsurai constructed their long houses partially below ground level led to the conclusion that groundwater was elevated compared to predevelopment conditions and attributed to OWTS contributions. Tsurai descendants reported local creeks historically did not flow year round but began to do so in more recent history, indicating that contributions to groundwater levels had increased (LACO, 2004). LACO Associates recommended the City of Trinidad investigate the possibility of constructing a sanitary sewer system and a wastewater treatment plant to mitigate increases to groundwater levels due to contributions to private OWTSs and that in the meantime the City institute a program to improve the operations and maintenance of OWTSs. Based on recommendation by LACO in the TMP, the City has implemented an OWTS Management Program that requires all property owner to maintain Operating Permits for their OWTS that are conditioned on regular inspections and maintenance with triggers for requiring upgrades. The City has noted that overall water use by customers has decreased over the past 20 years. However, outside the City, due to the lack of documentation, there is uncertainty around the functionality and maintenance status of unpermitted OWTS. OWTS that are not properly designed, constructed, and/or maintained have the potential to contaminate local surface and groundwater (Trinidad Regional Water Management Working Group, 2008). Much of Trinidad and the surrounding area has ideal soils for OWTS, but there has been documented bacterial contamination in the surface water around the City (LAFCO, 2021).
The Trinidad Rancheria owns and operates a package wastewater treatment facility at the Trinidad Harbor Properties that serves the Seascape Restaurant, Seascape rental house, and public restrooms. Treatment consists of a collection system with multiple stages of filtration, de-nitrification, and ultraviolet disinfection. Effluent is disposed of using subsurface disposal fields.
6.2.8 Trinidad Harbor Properties
Two headlands provide shelter from wave action for the Harbor and Pier within Trinidad Bay. The Harbor Properties, owned and operated by Trinidad Rancheria, are an economic center that supports several cultural, commercial, and recreational services and opportunities. These services include commercial fishing operations, local fishing charters, boat launch, and coastal access. There is also a restaurant, parking, and restrooms, as mentioned above in Section
6.1. 6.2.9 Public Amenities
The Planning Area contains a variety of public amenities that establish a unique atmosphere. Several of these public amenities were specifically identified by the community as valuable coastal resources, these include:
• Public schools
– Trinidad Elementary School
• Trinidad Town Hall
• Trinidad Branch Library
• California State Polytechnic University,
Humboldt Telonicher Marine Laboratory
• Town Center/Shopping Area
• Trinidad Museum
• Trinidad Native Garden
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 44 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. • Trinidad Harbor, Pier, Boat Launch, Seascape
Restaurant (owned and operated by Trinidad
Rancheria)
• Public Restrooms
• Beach and Ocean Access
• Trinidad Coastal Land Trust
• Small/local businesses
The above list is not inclusive of all amenities in the Planning Area but reflects the results of public input during outreach events. Many of these amenities are located in the central portions of Trinidad. Public amenities are shown below in Figure 6-4.
Figure 6-4 Public amenities
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 45 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6.3 Cultural, Historical, Natural, and Scenic Resources The importance of the Planning Area’s cultural, historic, and natural resources is reflected in the City’s General Plan, which highlights the need to honor and protect cultural and historic heritage, scenic views, and environmental resources. Cultural and natural resources within the Planning Area that are considered in this Planning Study consist of historic properties and places, water, habitat, beaches, and recreational resources. These resources are summarized below and shown in Figure 6-5. Cultural and natural resources are not limited to the boundaries of the Planning Area. The resources adjacent to the Planning Area that impact the resources within the Planning Area should be considered. For instance, the water supply and quality are sensitive to pollutants, contaminants, and environmental conditions that originate upstream.
Figure 6-5 Natural and scenic resources
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 46 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6.3.1 Cultural Resources
As defined in Public Resources Code § 21074, tribal cultural resources are either of the following:
(1) Sites, features, places, cultural landscapes, sacred places, and objects with cultural value to a California Native American tribe that are either of the following:
(A) Included or determined to be eligible for inclusion in the California Register of Historical Resources. (B) Included in a local register of historical resources as defined in subdivision (k) of Section 5020.1. (2) A resource determined by the lead agency, in its discretion and supported by substantial evidence, to be significant pursuant to criteria set forth in subdivision (c) of Section 5024.1. In applying the criteria set forth in subdivision (c) of Section 5024.1 for the purposes of this paragraph, the lead agency shall consider the significance of the resource to a California Native American tribe.
The Planning Area is rich in cultural, natural, and scenic resources, as it is located on the ancestral lands of the Yurok Tribe and the Yurok Village of Tsurai. The Tsurai Village is the southernmost village in Yurok Tribe ancestral territory along the California coast. The landscape is central to Yurok creation stories and traditions and was historically connected through a network of villages, trails, and resource areas (Yurok Tribe Environmental Program, 2007).
Trinidad Head / Tsurewa
Tsurewa is a cultural resource of sacred importance to the Yurok people and specifically to lineal descendants of the Tsurai Village. Tsurai, means “mountain,” because of its association with Tsurewa (Yurok Tribe Environmental Program, 2007). The following excerpt from the Tsurai Management Plan describes the creation of Tsurewa as told by Lame Billy of We’itspus to Anthropologist Albert Kroeber of the University of California, Berkeley between 1901 and 1902 (Yurok Tribe Environmental Program, 2007):
The story begins that a young man who grew up at Tsurai had a sister who he told one morning, “I should like to see a pretty hill be” (Kroeber 1976:18). When she asked him what the purpose of this hill would be, the young man replied,
I always hear laughing when the wind blows from there. I almost hear someone laughing.
That is why I want to make a good hill here. I want to sit on it that I may look about. There may be people somewhere.
Perhaps they will see me when they come by (Kroeber 1976:18) The young Tsurai man then proceeded to go down to the beach, gather a pile of sand in his hands, make the pile round and set it down again. Thus, Tsurewa was created.
After the young man had created Tsurewa, he sat upon it and said, “I wish you would be higher,” and the sand grew higher. After some time had passed, the young man again said, “I wish you would be a little higher,” and the sand grew even higher. Satisfied, he looked around and said, “That is all,” and ran down the hill to his home (Kroeber 1976:19). When he got home he grabbed a stool and returned to the top of Tsurewa and placed it securely. “Downstream from it he set a white rock, across a black rock, above a red rock. Upstream was the side to which he looked (Kroeber 1976:19). The young man sat on his stool and began to wonder what his stool should become. He then thought, It will be best if I make a hole here with a spring in it. I shall come here sometimes if I want woodpecker crests. I think that is how I shall make my stool. On the side here next to it I shall make a small hole. I shall come there if I want persons’ money (dentalium shells). I shall come and wash my hands in that. (Kroeber 1976:19).
So the young man made two water holes up on the top of Tsurewa and sat on his stool.
This story continues as the young man of Tsurai travels within Yurok Ancestral Territory and visits many villages to instruct other Yurok on how to properly conduct ceremonies (Kroeber 1976:19-28). What is GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 47 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. important is that this story relates the creation of Tsurewa and establishes that the Village of Tsurai predates the rock Promontory known as Trinidad head in regards to Yurok oral tradition.
Tsurai Village
The Tsurai Village has been in existence since time immemorial. Tsurai was the southernmost village of the Yurok Tribe whose boundaries were north of Tsurewa (Trinidad Head) to O prmrg wror (Beach Creek), to the eastern border shared with the Chilula, to the south to Little River and to the west some five miles into the ocean including offshore rocks, the sea stacks, traditional gathering and fishing spots, traditional training grounds, and ceremonial places.
Since the arrival of Spanish explorers in 1775, there have been steady changes to Tsurai. Some pieces of this cultural landscape were forever lost, while others remain intact and resilient. Among them, the Tsurai people stand out as paragons of resilience, demonstrating the ability to evolve with changing tides by establishing the Tsurai Ancestral Society, a non-profit organization committed to safeguarding this cultural landscape.
The Tsurai Village is a sacred place, containing the village’s cemetery, religious, and ceremonial sites. The City is required to consult with the Tsurai Ancestral Society, Tsurai Management Team (TMT), and other local Tribes regarding proposed projects or planning efforts per Assembly Bill 52, Senate Bill 18, and Local Coastal Plan Policy 69.
Axel Lindgren II (1918-1999) was the founder of the Tsurai Ancestral Society and lineal descendant of the Tsurai Village. He was a traditional Yurok storyteller and wrote about his family and village. One such story was about his grandmother Eliza calming the ocean at Tsurai. The story describes Tsurai’s connection to the ocean and close proximity. Axel describes storms and winter months that were almost unbearable, some having thunder, lightning, and hurricane force winds. A wind-driven sea made gathering food in the ocean impossible and the beaches impassable for the Tsurai people. However, Axel goes on the describe how the village residents never feared those conditions because his Grandmother, Eliza Lindgren (1836-1940) who was a powerful medicine woman, would be called out to the beach to go to her medicine rock where she would then pray and calm the ocean. This would bring balance back to life in Tsurai and the environment around them. Gathering would again resume and good health and well-being would be restored to the ailing village. It is the Tsurai Ancestral Society’s hope that through careful planning and proper management, there will again be balance within the Tsurai Village and greater area. A drawing of the view from the bluffs is provided in Figure 6-6.
Figure 6-6 Honeyman drawing of Tsurai and Bay (Photo courtesy of Bancroft Library, included in Tsurai Management Plan, Yurok Tribe Environmental Program 2007) GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 48 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Axel Lindgren Memorial Trail
The Axel Lindgren Memorial Trail is a ceremonial and traditional trail to the Tsurai Village. Under the supervision of Axel Lindgren, a Tsurai lineal descendant and founder of the Tsurai Ancestral Society, the trail was built by the Yurok Tribe in 1997. Axel Lindgren II (1918-1999) spent a lifetime educating the Trinidad and global community about Tsurai and the greater Yurok culture. Because of his tireless efforts to protect and maintain the village and traditional access, the Axel Lindgren Memorial Trail was dedicated to him in 1999 after his passing. The trail extends from the bluff down to the village and continues to the beach. It is very steep, of moderate intensity, and provides views of the shoreline, coast, and surrounding vegetation. The trail requires special consideration due to its status as both the designated primary beach access trail and as the Tsurai traditional and ceremonial trail. In July 2023, the Tsurai Ancestral Society created a plan to improve the trail due to significant erosion concerns at top and bottom and neglect throughout the rest of the trail. Repeated illegal cutting and illegal camping along the trail also contribute to negative impacts to the stability of the bluff and cultural resources. The Axel Lindgren Memorial Trail has required frequent repairs to reduce hazardous conditions caused by slope instability and erosion (also see Section 5.2 Bluff Erosion).
Trinidad Rancheria
The Cher-Ae Heights Indian Community of the Trinidad Rancheria (Trinidad Rancheria) is a federally recognized tribe with ancestral ties to the Yurok, Wiyot, Tolowa, Chetco, Karuk and Hupa peoples. While they share similar cultural and historical traditions, each tribe has a distinct heritage. The Rancheria is within the aboriginal territory of the Yurok peoples and is located in an area of great cultural significance to the Trinidad Rancheria and other local tribal entities.
The core land holdings of the Rancheria is located on a coastal bluff east of U.S. Highway 101 just southeast of the town of Trinidad. This parcel accommodates Tribal Member Housing, Tribal Offices, a Tribal Library, and the Cher-Ae Heights Casino. The Trinidad Rancheria is now comprised of three separate parcels near Trinidad, Westhaven, and McKinleyville, that total 82 acres.
6.3.2 Historic Resources
Historic resources can be objects, sites, buildings, structures, or districts. Multiple state and federally recorded historic resources are located within the Planning Area.
• Trinidad Head / Tsurewa was registered as a California State Historical Landmark (#146) in 1934. • Town of Trinidad was founded April 8, 1850. During that time, it served as a vital supply link between ships and miners in the Klamath, Trinity, Salmon River, and Gold Bluff mines. In 1935 it was registered as a California State Historical Landmark (#216).
• The Tsurai Village was designated as a California State Historical Landmark (#838) in 1969. The Village was nominated to the National Register of Historic Places in 1977 but was never evaluated. • Holy Trinity Church is located on Parker and Hector Street. It was placed on the National Register of Historic Places as a Historical Landmark (N895; Ref#80004608) in 1980. • Trinidad Head Light Station on the southwestern slope of Trinidad Head / Tsurewa was placed on the National Register of Historic Places as a Historical Landmark (N1720; Ref#91001098) in 1991. The station contains a lighthouse tower, fog-signal building, and keeper’s residence. BLM currently manages the facility and continues to operate the lighthouse tower as a navigational beacon (Figure 6-7). A replica of the lighthouse (Trinidad Memorial Lighthouse) is now located near the parking lots at the foot of the Trinidad Head Trail. The replica lighthouse is not a registered historic resource; however, it does house the original Fresnel lens from the Trinidad Head lighthouse.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 49 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 6-7 Trinidad Head Light Station lighthouse tower
6.3.3 Natural Resources
There is a strong relationship between the cultural and natural resources in the Planning Area. Natural resources have played a vital role in the Yurok culture and for the Tsurai Village. Preservation of natural resources is vital to the preservation of the Yurok culture. Based on existing studies and the vegetated open space within the Planning Area, there is a high likelihood of sensitive plant and wildlife species occurring within the Planning Area. Natural resources provide important ecological and economical functions, including public access stability, aesthetic quality, sustenance, and critical habitat. The natural beauty of Trinidad attracts residents and tourists alike to visit the area.
6.3.3.1 Terrestrial Habitats
These could include Sensitive Natural Communities (SNCs), Environmentally Sensitive Habitat Areas (ESHAs), species listed as endangered or threatened under the federal or state Endangered Species Act (ESA and California ESA, respectively) or their designated critical habitat, as well as California special-status species and habitats. Recent studies have mapped SNCs, such as Berry Brambles and Red Alder, along the South Bluff area. Some of the habitat types within the Planning Area could be considered coastal scrub, coastal dune, coastal bluff, and riparian forest.
Based on recent and nearby studies, several special status plant species may also occur in this area.
Multiple bird species, such as the Marbled Murrelet, Bald Eagle, and Bank Swallow that are federally listed, state listed, or both have been detected within or within close proximity to the Planning Area. The Planning Area contains features that may support other special status taxa, including other special status bird species, bats, and other mammals and amphibians. Additionally, the Planning Area may support nesting birds protected by the Migratory Bird Treaty Act and Fish and Game Code. The Planning Area is located within the Pacific Flyway for migratory birds.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 50 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
6.3.3.2 Aquatic Habitats
The National Wetlands Inventory (NWI) and National Hydrography Dataset (NHD) were reviewed for potential ESHA and wetlands. Freshwater wetlands present in the Planning Area include several creeks and streams. Other wetlands present are areas of the sandy beaches, classified by the NWI as Estuarine and Marine. ESHA or additional wetlands may be present within the Planning Area and would require verification with a biological assessment or wetland delineation.
Various special status fish species, including but not limited to the Western Brook Lamprey and Coast Cutthroat Trout, may occur within aquatic habitat within the Planning Area. Additionally, there is designated Chinook and Coho Salmon Essential Fish Habitat within the Planning Area; the Pacific Fisheries Management Council Salmon Fishery Management Plan encompasses these species. Important harvested natural resources include shellfish, rockfish, abalone, kelp. The lamprey, mussels, and seaweed are all traditional foods of the Tsurai and pollutants impede traditional gathering.
Marine resources were not evaluated in this study; however, some are important to note due to their biological and cultural importance and / or legal designations.
• The kelp beds at Trinidad Bay were designated as an ASBS by the State Water Resources Control Board in 1974 under the provisions of the Marine Life Protection Act. The Act prohibits the pollution of protected areas, requiring strict runoff and contaminated discharge management. • The CCNM Trinidad Unit protects islets, reefs and rock outcropping providing crucial habitat for resident and migratory species of seabirds, marine mammals and invertebrates. The sea stacks and islands in Trinidad Bay and surrounding areas are protected as part of the CCNM and are traditional resources for the Yurok people.
6.3.4 Scenic Resources
The Trinidad Area Plan of the Humboldt County Local Coastal Plan defines "Highly Scenic Areas" to “generally include: (1) landscape preservation projects designated by the State Department of Parks and Recreation in the California Coastline Preservation and Recreation Plan; (2) open areas of particular value in preserving natural landforms and significant vegetation, or in providing attractive transitions between natural and urbanized areas; and (3) other scenic areas and historical districts designated by cities and counties.” The Planning Area contains a wide variety of visual and scenic resources that are valued by the community and are also a cultural resource of the Tsurai Village. These include views along the ocean and coastline, natural landforms, and the overall landscape of the surrounding areas. And may also include forested hillsides, agricultural land, or river corridors. Among the Planning Area, the most prominent visual resources include Stagecoach Drive and Scenic Drive (which have been designated Coastal Zone Scenic Views), Trinidad Head / Tsurewa, and the surrounding coastline and vista points.
6.4 Future Resources
Future resources are those that have been recognized as currently missing, needed or in-need of improvement within the community. The planning and implementation of new resources should recognize and consider the impacts of climate change. The specific future resources that were identified by the community during the first public meeting for this Planning Study, and by the Planning Partners, have been classified into recreational, accessibility, public amenities, municipal, and sustainability / future energy. The future resources include, but are not limited to:
• Recreational Trails:
– Educational trail signs
– Trail maintenance and future funding
– SLR and climate change adaptation
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 51 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. – Expanded trail network and trail connections to the south (across the Little River) • Town Accessibility:
– Improved pedestrian walkability along scenic routes
– Addition of bike parking stations
– Improved bikeways from downtown to the harbor
– Enhanced public transportation
– Improved beach access
• Public Amenities:
– Improved picnic areas
– Community garden
– Waste / garbage services (increased number of waste bins) – Increased public restrooms in public areas
– Dog waste receptacles
– Trinidad Harbor Interpretive Center
– Trinidad Memorial Lighthouse (permanent location)
– Emergency Warning systems (for Tsunamis)
– Water quality monitoring systems (for HABs)
– Environmental Interpretive Information
– Community event spaces
– Complete streets and Active Transportation infrastructure • Municipal:
– Avenues or platforms for more direct lines of communication between the local government and community (i.e., social media)
– Waste Reduction and Recycling Infrastructure
• Sustainability and Future Energy:
– Community composting facility
– Rainwater catchments
– Additional water storage facilities
– Clean/renewable energy sources
– Wastewater Treatment Plant for homes within the City limits – Habitat restoration
– Strategic plans for the reduction of energy and materials consumption – Alternative Fueling Infrastructure
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 52 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
7. Vulnerability Assessment
Each of the community resources that were identified were considered in the evaluation of vulnerability so that impacts to resources could be prioritized. It is important to note that the vulnerability scores are based on the vulnerability of the resource only within the anticipated areas of impact. Vulnerability scores should not be applied widely to a resource across the Planning Area. For example, only the roadways that are exposed to hazards are presented with vulnerability scores. Therefore, the vulnerability score only applies to those specific roadways and not to all roadways within the Planning Area.
Resource exposure and impacts largely focus on the footprint of physical processes and hazards within the Planning Area. Physical hazards and processes including flooding, shoreline erosion, and bluff erosion are shown based on areas of impact and existing resources. Table 7-1 provides and overview of the Exhibits and associated locations and hazards. Locations can be generally described as follows:
- North Planning Area: Northern Trinidad State Beach to College Cove - Central Planning Area: Southern Trinidad State Beach to Old Home Beach and City of Trinidad - Southern Planning Area: Scenic Drive and Trinidad Rancheria Table 7-1 Potential Impact and Adaptive Capacity Scoring Exhibit Hazard and Sea Level Rise Scenario
A.1 – A.3 Base Flood Elevation - 0 Ft Sea Level Rise
B.1 – B.3 Base Flood Elevation - 1.6 Ft Sea Level Rise
C.1 – C.3 Base Flood Elevation - 3.3 Ft Sea Level Rise
D.1 – D.3 Base Flood Elevation - 6.6 Ft Sea Level Rise
E.1 – E.3 Shoreline Erosion – 0 to 6.6 Ft Sea Level Rise F.1 – F.3 Bluff Erosion – 0 to 6.6 Ft Sea Level Rise
Additional consideration to larger scale processes such as fire risk, precipitation variability, temperature, and ocean acidification are considered and evaluated where appropriate when identified resources may be affected, but not shown on the Exhibits.
7.1 Vulnerability Assessment Methods
This Vulnerability Assessment leverages the guidance provided in the State of California’s Adaptation Planning Guide (APG), which was recently updated (2020) by the State of California Office of Planning and Research (Cal OES, 2020). The APG defines vulnerability as the degree to which natural, built, and human systems are susceptible to harm. Assessing vulnerability is one of the key steps in understanding existing and future hazards and their potential impacts to City assets and infrastructure. Vulnerability is comprised of three primary factors:
• Exposure is the degree to which an asset or resource is exposed to impacts (e.g., SLR) and associated hazards. Exposure was evaluated in terms of the spatial extent, duration, and frequency of the hazard. • Sensitivity is the degree an asset or resource would be impaired by the impacts of the hazard. Systems that are greatly impaired by the exposure to SLR hazards or projected changes in climate have a high sensitivity, while systems that are minimally impaired by this same exposure have a low sensitivity. • Adaptive capacity is the ability of an asset or resource to respond to hazards and climatic changes, to moderate potential damages, to take advantage of opportunities, and to cope with the consequences. In other words, adaptive capacity is the asset’s ability to adjust or recover to the hazard without substantial GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 53 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. modification. This does not mean that the system must look the same as before the impact, but it must provide comparable services and functions with minimum disruption or additional cost.
The combination of exposure and sensitivity of a resource to a particular hazard defines the potential impacts associated to that resource. For instance, a resource can have a high exposure to a hazard but may not be particularly sensitive to that hazard, suggesting minimal impacts. Likewise, a resource may have a low hazard exposure but is extremely sensitive to that hazard, which points to a higher vulnerability. The potential impacts are also related to the impact threshold, or tipping points at which the potential consequences associated with a given scenario (i.e., coastal hazard, water level, and timeframe) increase significantly. Identifying these thresholds are a key outcome of this assessment. The impact thresholds can be correlated to a possible future condition, such as an SLR projection, to estimate the probability of occurrence at a given time horizon. This provides valuable information for prioritizing adaptation strategies and understanding how these strategies may need to evolve over longer planning horizons.
When determining the climate change factors expected to impact a region, the APG suggests using the State of California’s Fourth Climate Change Assessment (FCCA) report for that specific region, in addition to other available climate resources. In this case, California’s FCCA for the North Coast Region was used to help determine the climate change factors that could impact critical City resources (Grantham, 2018).
7.1.1 Vulnerability Scoring
Resource vulnerability was quantified by utilizing the scoring system recommended within the APG. That is, the potential impact and adaptive capacity of each resource are assigned a score of low, medium, or high. The potential impact accounts for the exposure and sensitivity, as well as the potential consequences. The definition of low, medium, and high potential impacts and adaptive capacity is provided below in Table 7-2.
Table 7-2 Potential Impact and Adaptive Capacity Scoring Score Potential Impact Adaptive Capacity
Low
Low impact is when impact to the resource is
unlikely based on the projected exposure and
would result in minor consequences to public
health, safety, and / or other metrics of concern.
Low adaptive capacity is when the resource lacks
capacity to manage climate impacts and major changes
would be required.
Medium
Medium impact is when impact to the resource is
somewhat likely based on the projected exposure
and would result in some consequences to public
health, safety, and / or other metrics of concern.
Medium impact is when the resource has some capacity
to manage climate impact and some changes would be
required.
High
High impact is when impact to the resource is
highly likely based on projected exposure and
would result in substantial consequences.
High capacity is when the resource has high capacity to manage the climate impact and minimal to no changes
are required.
Once the potential impacts and adaptive capacity have been determined, a vulnerability score is then assigned on a scale of 1 to 5, with 5 being the highest vulnerability. The vulnerability score is a combination of the potential impact score and the adaptive capacity score (Table 7-3). For instance, a resource with a high potential impact and medium adaptive capacity would be assigned a vulnerability score of 4.
Table 7-3 Vulnerability Scoring Rubric from the APG and used to Assess Resource Vulnerability Adaptive Capacity
High Medium Low
Potential Impacts
High 3 4 5
Medium 2 3 4
Low 1 2 3
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 54 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Resources are also discussed qualitatively and not all resources are assigned a vulnerability score. In some instances, there is not enough information or data to confidently apply a vulnerability score. The vulnerability score is a ranking system meant to aid the development of adaptation actions and prioritize future projects. The development and selection of adaptation actions, a primary goal of this assessment, will consider several other factors, such as community significance and risk tolerance. Additionally, the vulnerability scores are based on the vulnerability of the resource only within the anticipated areas of impact. Vulnerability scores should not be applied widely to a resource across the Planning Area.
7.1.2 Coastal Hazard Mapping
The coastal hazards scenarios considered in this Vulnerability Assessment were selected based on relevance and available hazard projection data. Several climate projections and coastal hazards were investigated and spatially mapped to determine the specific vulnerability of each community resource. A total of four hazard scenarios were selected for spatial analysis, these scenarios are as follows:
• Shoreline Erosion: The shoreline erosion scenario represents the landward retreat of the MHW line shoreline with SLR, a typical proxy for shoreline delineation which separates the submerged profile from the dry beach, or available 'towel space’ that can be utilized for recreation. • Bluff Erosion: The bluff erosion scenario represents the landward retreat of the existing bluff edge. • Tidal Inundation: The tidal inundation scenario represents the upper range of daily tide levels, MHHW, with SLR. This scenario is meant to model the daily inundation, in other words the resources contained within this flood zone will be subject to daily flooding under normal high tides. • Coastal Flooding: The coastal flood scenario is representative of the 100-year storm and incorporates enhanced water levels and wave action. The 100-year storm correlates to a return period of 100 years and an annual occurrence probability of 1%. With a relatively low annual occurrence probability, this scenario presents a more intense event, though lasting only a short amount of time.
These coastal hazard scenarios were mapped based on available projection data. The USGS CoSMoS provides shoreline and bluff erosion projections with SLR for northern California and FEMA provides coastal flood zones and associated BFEs (without SLR). CoSMoS is a multi-agency effort led by the USGS to estimate coastal flooding, erosion (shoreline and bluff) hazards for a range of future SLR scenarios along the California coast. The data is available in 0.8 feet (25 cm) increments from 0 to 6.6 feet (200 cm) and an extreme scenario of 16.4 feet (500 cm).
The coastal flood scenario was generated by coupling SLR projections with the representative FEMA BFE. The tidal inundation scenario was generated by coupling the representative MHHW datum elevation and coupling SLR projections. The various tidal and flood elevations were mapped according to the best available topography data for the Planning Area.
Additional information regarding bluff stability and other related information and analyses are provided in site-specific studies that include SHN’s Coastal Setback Analysis for 20 Scenic Drive (SHN, 2016a), Preliminary Assessment of Current Slope Stability Conditions for Trinidad Memorial Lighthouse on Edwards Street (SHN, 2017a), Landslide Mitigation Assessment (SHN, 2017b), Coastal Landslide Hazard Evaluation (SHN, 2019a), and Draft Edwards & Van Wycke Sea Level Rise and Landslide Risk Assessment and Management Plan (SHN, 2019b). This additional detail has been incorporated to supplement the CoSMoS information and provide additional site-specific information where applicable. The top of bluff mapping by SHN and CoSMoS bluff edge exhibit general agreement along the West Bluff and below Van Wycke Street. However, significant differences are noted along Edwards Street and Scenic Drive, where the CoSMoS data set identifies the top of bluff along a lower elevation terrace and SHN mapped the top of bluff along a higher elevation, further inland. SHN utilized a “bluff crest” or “bluff edge”, which is defined in the Coastal Act as “the upper termination of a bluff, cliff, or seacliff” (California Code of Regulations, Title 14, Sec 13577 (h)(2)). Both data sets are presented in the figure set for this project. Future projections for bluff retreat as a result of SLR are specific to the CoSMoS data set as the detailed methods to develop these projections and apply to the SHN mapping were not a part of this project.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 55 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
After community resources were identified they were evaluated for impacts from hazards, including both the climate change impacts listed above as well as the coastal processes hazards. In some cases, there is overlap between climate change impacts and coastal process hazards. For example, SLR impacts the degree of bluff erosion, coastal flooding, and coastal inundation. Whereas wildfire, coastal fog dynamics, and increasing precipitation variability may not directly impact those coastal processes.
In addition, not every resource is impacted by the same hazards. For example, some of the roadways in the Planning Area are impacted by the coastal process hazards (bluff erosion, coastal flooding, and coastal inundation), whereas the raw water supply in Luffenholtz Creek that is used for drinking water is not directly impacted by the coastal process hazards. Instead, the raw water supply is impacted by increasing precipitation variability, rising temperatures, coastal fog dynamics, and potentially wildfire. Sections 7.2 through 7.4 discuss the results of the vulnerability analysis and present which resources are impacted by which hazards.
7.1.2.1 Data Limitations
Shoreline retreat and bluff erosion along the Planning Area were evaluated using results of CoSMoS. CoSMoS shoreline erosion projections include long-term erosion resulting from SLR and projected wave conditions based on the Coastal One-line Assimilated Simulation Tool (COAST), which includes a suite of models that consider historical erosion trends, long- shore and cross-shore sediment transport, and shoreline changes due to increased water levels.
The COAST model includes shoreline management scenarios referred to as “Hold-the-Line” and “No-Hold-the-Line.” The “No Hold-the-Line” scenario assumes no coastal armoring is in place and projects future shoreline position based on a natural response to future waves and water levels.
The CoSMoS bluff erosion regional modeling effort used a baseline cliff edge position from 2010 with transects spaced at 100-meter increments. In an effort to improve resolution of the baseline cliff edge for the Planning Area, the cliff edge was digitized between transects. The digitized cliff edge used the location and elevation of the CoSMoS baseline points and interpolated between points using a topographic dataset elevation contours and aerial imagery to represent the baseline cliff edge. The retreat rates were extracted from the results and applied to the existing shoreline and bluff edge to increase the resolution across the Planning Area. These results are intended to identify potential vulnerabilities and are for planning purposes only. Due to the regional nature of the USGS model and uncertainties surrounding climate change related impacts and associated with coastal numerical modeling, these results should not be used for project-level planning purposes. The following disclaimer is applied to all USGS data used in this evaluation and is taken from the USGS:
“Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes.
The U.S. Geological Survey provides these data “as is” for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information.
The suggestions and illustrations included in these images are intended to improve coastal-flood awareness and preparedness; however, they do not guarantee the safety of an individual or structure. The contributors and sponsors of this product do not assume liability for any injury, death, property damage, or other effects of coastal flooding.
Use of trade names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.”
Additional top of the coastal bluff mapped by SHN: although the mapping is based on thorough field review and many years of professional experience, the scale of the mapping is such that it should be used only for planning purposes.
Additional site-specific evaluation may be appropriate for more focused applications.
Coastal flood zones were derived from FEMA BFEs. Flooding zones shown are intended to identify potential vulnerabilities and are for planning purposes only and should not be used at the project scale. Detailed analysis of flooding should be completed for project-level planning purposes.
This Vulnerability Assessment leverages a variety of data sources to plan for climate change related impacts to the most feasible extent possible. Climate change science, as well as localized studies, are evolving resources and site- GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 56 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. specific project planning should utilize the best available science and data. For instance, habitat and bluff related data is subject to change on a seasonal basis and conditions may depend on varying environmental conditions. In addition, SLR science and SLR policy guidance is periodically updated to reflect the best available science. This Vulnerability Assessment reflects the most up to date SLR policy guidance; however, SLR science should be reviewed periodically to reflect the most recent policies and guidance.
7.2 Public Access and Recreation Resource Vulnerability Public access and recreation activities have been identified by the community as significant community resources. The exposure of these resources and potential climate impacts are discussed below.
7.2.1 Trails
Several trails along the bluff face were identified as vulnerable to shoreline and bluff erosion. The trails that traverse the Planning Area also serve as beach access to many of the pocket beaches lining the Trinidad area’s rocky coastline. Shoreline erosion will impact the trailheads along the beaches, although many of these trails aren’t impacted by shoreline erosion until the dry beach (MHW shoreline) has entirely eroded to the bluff toe. Bluff erosion may be more impactful to the trail alignment, as it can sever trails and further limit access to the beach. Erosion of the lower bluff areas are common during large winter storms and access along these lower elevations has been altered by steepening of the bluff toe. Movement of the entire bluff slope below sections of Edwards Street has been documented as far up the slope as the Axel Lindgren trailhead and parking area (SHN, 2017a). Also, significant bluff erosion has been documented along the bluff below the Trinidad Head access road prompting the Trinidad Rancheria to declare a state of emergency in 2023. Several other trails exist along or adjacent to eroding bluff areas. Trails were assigned a high sensitivity to bluff erosion but are considered to have a medium adaptive capacity as trail alignments may be able to be adapted to conform to eroding bluff faces and if not, alternative alignments or trails could provide similar access and experiences.
7.2.2 Beaches
The Planning Area beaches are vulnerable to shoreline erosion, tidal inundation, and coastal flooding. These beaches are important community resources, supporting a variety of recreational activities. Based on the hazard mapping, shoreline erosion will overtake 50% of the total existing beach area as sand is eroded into the submerged profile with
1.6 feet of SLR, meaning that the available ‘dry beach’ or ‘towel space’ is significantly reduced and lateral access may become increasing limited during regular high tides. For 3.3 feet of SLR, the hazard mapping suggests that 90% of the total beach area is eroded and all of the beaches (100%) within the Planning Area are eroded into the submerged profile with 6.5 feet of SLR. The tidal inundation hazard zones will yield very similar results to that of the shoreline erosion, as both scenarios are associated with the high tide line. As the daily range of water levels increase and the shoreline retreats landward, lateral access along the beaches may become increasingly limited. Beaches are considered to have a high sensitivity to shoreline erosion and flooding and a low adaptive capacity.
7.2.3 Public Parking
The public parking lots located in the Trinidad Harbor vicinity serve as a conduit for the harbor amenities, Trinidad Head / Tsurewa, recreational activities, and beach access. There are five public parking lots / areas between Trinidad State Beach and the Pier, all of which are paved except for the Trinidad State Beach parking. This area between the Trinidad Head / Tsurewa and the Pier is relatively low lying and is vulnerable to the coastal flooding scenario. Under existing conditions, the coastal flood zone stretches into the parking area from Launcher Beach to cover approximately 12% (0.2 acres) of the total parking area. With SLR, the flood zone expands to cover 30% of the total parking area for
1.6 and 3.3 feet of SLR and 34% of the total parking area for 6.5 feet of SLR. These parking lots have a medium sensitivity to flooding and a high adaptive capacity. These parking lots can accommodate temporary flooding and impacts to the community may only involve temporary closures; no long-term damage would be anticipated from a coastal flood event.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 57 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Parking along Edwards Street has shown indicators of bluff movement. In 2017, the head of an active earthflow-type landslide was observed with the highest extent occurring in the parking area, identified by open fissures in the pavement (SHN, 2017a).
7.2.4 Amenities
The Trinidad Harbor area contains a variety of amenities, businesses, and critical infrastructure that serve as valuable community resources. These resources include the Seascape Restaurant and public restrooms in the vicinity of the public parking lots, supporting comfortable access to beaches, trails, and many other recreational activities. The Trinidad Rancheria also owns and operates a boat launching facility near the Seascape Restaurant and smaller boats launch directly from Launcher Beach. Coastal flooding is the primary hazard for this area and the public restrooms were identified as vulnerable under the coastal flood scenario with 3.3 feet of SLR. However, given the flood exposure of the parking lot, it is unlikely that the access to these restrooms will be a priority during a 100-year storm (coastal flood scenario). These restrooms are considered to have a medium sensitivity to flooding and a high adaptive capacity as long-term implications to the functionality are not anticipated. The storm surge and wave runup associated with 3.3 feet of SLR does not result in significant depth at the OWTS for the restrooms.
7.2.5 Public Parks
There are two public parks relevant to the coastal hazards and climate projections examined in this Vulnerability Assessment. Atop the Trinidad State Beach bluffs, the Trinidad Park provides scenic views and access to the network of recreational trails. Located along the bluff edge between Old Home Beach and Edwards Street, the Trinidad Bay Memorial Park has been identified as vulnerable to bluff erosion. Although the CoSMoS bluff projections do not intersect the park, landslides have been documented in the vicinity, which triggered the relocation of the Trinidad Memorial Lighthouse (SHN, 2017b). Given these existing conditions, enhanced bluff retreat due to SLR would likely present additional stability issues. The Trinidad Bay Memorial Park has been assigned a high sensitivity to bluff retreat and a low adaptive capacity.
7.2.6 Vulnerability Summary
The public resources identified as vulnerable to future coastal hazards are summarized below in Table 7-4 and shown in Figure 7-1 relative to the primary hazard and SLR threshold, referring to the minimal SLR scenario that results in impacts to the resource.
Table 7-4 Summary of Public Access and Recreation Resource Vulnerability Resource Primary Hazard SLR
Threshold Vulnerability
Trails / Beach
Access
Shoreline / Bluff
Erosion 1.6 ft
– Axel Lindgren Memorial Trail
– Lighthouse Road / Trinidad Head / Tsurewa Trail
– Van Wycke Street Trail
– College Cove Trail
– Trinidad State Beach to Elkhead
– Trinidad State Beach Access
Beaches
Shoreline
Erosion /
Flooding
3.3 ft – 90% of the existing dry beach (towel space) is eroded into the submerged profile
Public Parking Coastal Flooding /
Bluff Erosion 1.6 ft – 30% of the total parking area near the Trinidad Harbor is within the coastal flood zone GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 58 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Resource Primary Hazard SLR
Threshold Vulnerability
– Edward Street parking is subject to earthflows under existing conditions and SLR will likely worsen stability
Amenities Coastal Flooding 3.3 ft – Public restrooms are exposed to the coastal flood zone Public Parks Bluff Erosion 1.6 ft – Trinidad Bay Memorial Park is subject to earthflows under existing conditions and SLR will likely worsen stability
Figure 7-1 Public access resources exposed to bluff erosion and flooding (bluff erosion and flooding hazards represent 6.5-foot SLR scenario)
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 59 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The vulnerability of public resources is summarized and assigned a vulnerability score below in Table 7-5. It should be noted that the vulnerability score only applies to the subset of resources that were identified as vulnerable and should not be applied widely across the Planning Area.
Table 7-5 Public Access and Recreation Resources Vulnerability Score Vulnerable
Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive Capacity Vulnerability
Trails / Beach
Access
Shoreline / Bluff
Erosion High Medium 3
Beaches Shoreline Erosion /
Flooding High Low 5
Public Parking Flooding / Bluff
Erosion Medium High 2
Amenities Flooding Medium High 2
Public Parks Bluff Erosion High Low 5
7.3 Critical Infrastructure and Services Vulnerability
For the purposes of this Planning Study, critical infrastructure and services include the roadways, emergency services, raw water supply, water distribution system, stormwater system, wastewater systems, and privately owned utilities.
The exposure of these resources and potential climate impacts are discussed below.
7.3.1 Roadways
Based on the results of the hazard mapping, several roadways were identified as vulnerable to coastal flooding and bluff erosion. The roadways identified as vulnerable to coastal flooding includes the parking lot and access roads in and around Trinidad Harbor (formerly known as Bay Street). This area serves as the main accessway to the Trinidad Harbor and is the only vehicular access to Launcher Beach and Harbor facilities. This 100-year flood scenario under existing conditions is constrained to the low-lying areas. As SLR increases, the flood zone extends to cover the entirety of the paved parking areas. Approximately 490 linear feet of roadway (2% of total roads) is exposed to the coastal flood zone without SLR and the linear feet of impacted roadway increases to 960 feet (3% of total roads), 1,125 feet (4% of total roads) and 1,310 feet (4.5% of total roads) for 1.6 feet, 3.3 feet, and 6.5 feet of SLR, respectively. Due to the temporary nature of the coastal flood scenario, the roadways have been assigned a low sensitivity and high adaptive capacity to coastal flooding. In other words, it is not anticipated that irregular coastal flooding would result in significant damage or disruption to the community.
As there are numerous roadways that traverse the bluff edge, several roadways are exposed to bluff erosion. The projected bluff edge with 1.6 feet of SLR is a consistent exposure threshold for these roadways. Based on the hazard mapping, bluff erosion directly impacts approximately 360 linear feet (1.2% of total), 1,350 linear feet (4.7% of total), and 1,895 linear feet (6.6% of total) of roadway for 1.6 feet, 3.3 feet, and 6.5 feet of SLR. The estimated linear feet of impacted roadway does not include indirect impacts (i.e., restricted access due to loss of road). Local geologic hazard mapping displaying active earthflows fronting Edwards Street suggests that Edwards Street and adjacent roadways may be vulnerable to bluff retreat in the near term. It is important to note that in addition the public roadways assessed, many private residences and roadways located in proximity to the bluff edge may be directly exposed to bluff erosion or may be indirectly impacted by bluff instability or access via impacted roadways. The significance and vulnerability of these roadways are summarized in Table 7-6 and shown in Figure 7-2.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 60 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Table 7-6 Summary of Roadway Vulnerability
Roadway SLR Threshold Description Vulnerability
Harbor Parking and
Access 1.6 ft
This roadway serves as a primary
access route to the Harbor area and
amenities as well as beaches.
A relatively small section of this
roadway is impacted under the 100-
year flood scenario with SLR;
however, this event is temporary and
it is not likely that flooding would
significantly impact roadway access
or result in any long-term impacts.
Trinidad
Head/Tsurewa
Access Road
Current
This access road provides the only
vehicle access to Trinidad
Head/Tsurewa and the associated
facilities.
Bluff Erosion has continued to
encroach on the access road.
Erosion of the bluff face and edge
have occurred episodically and are
expected to continue.
Edwards Street Current
This roadway serves as the only
connection between the lower
elevations in and around the Harbor
and beaches and higher elevations
and egress to other areas.
The loss of the roadway is significant
as there is no current alternative
access. The active landslide
documented in 2017 is expected to
continue encroaching toward
Edwards Street.
Van Wycke Street
(primarily between
Edwards and Galindo
Streets)
Current
This roadway serves several private
properties and is the primary and
only accessway for many of those
properties.
The loss of the roadway is potentially
significant as there does not appear
to be room for alternative access.
Additionally, the street may be
rendered unstable before the cliff
edge intersects the street.
Pacific Court and
Azalea Way 1.6 ft
Pacific Court runs parallel to Trinidad
State Beach along the top of the bluff
and serves approximately five private
residences. Access to Pacific Court is
provided via Azalea Way, which
connects to Edwards Street. The
residences on Pacific Court are
between the bluff edge and the
roadway.
Site-specific analyses are required as
the rate of retreat and other
observations by local geologists
suggests a greater degree of stability
than that assumed by the CoSMoS
model.
While the Pacific Court roadway does
not intersect the projected bluff edge
with 1.6 ft of SLR, the buffer between
potentially suggests high erosion
rates due to predominant wave
direction. With 3.3 ft of SLR the
projected erosion Pacific Court
extends landward of the roadway.
Approximately 50% of Azalea Way is
projected to be impacted with 6.5 ft of
SLR.
Ewing Street 1.6 ft
This roadway is located north of
Azalea Way, spanning parallel to
Trinidad State Beach in between the
bluff edge and the Cal Poly Humboldt
Telonicher Marine Lab.
Site-specific analyses are required as
the rate of retreat and other
observations by local geologists
suggests a greater degree of stability
than that assumed by the CoSMoS
model.
The projected CoSMoS bluff edge
encroaches the roadway with 1.6 ft of
SLR. The majority of Ewing Street
would be overtaken by the projected
bluff edge with 3.3 ft of SLR.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 61 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Roadway SLR Threshold Description Vulnerability
Scenic Drive 1.6 ft
This roadway is considered a
significant resource for the
community from an access and visual
resource perspective. It spans the
City of Trinidad to Moonstone Beach
County Park to the south and is the
main route to the coastal Trinidad
Rancheria (and many residential
homes).
Active earthflows have been noted
along Scenic Drive in several
locations under existing conditions.
The segment of roadway that spans
along the bluff edge in the
southeastern portion of the
Rancheria is exposed to the 1.6-ft
SLR bluff edge, which would limit
access to the Trinidad Rancheria.
Other sections of Scenic Drive may
be further evaluated as bluff retreat
has the potential to result in stability
issues throughout the roadway
alignment extent.
Figure 7-2 Roadways exposed to bluff erosion and coastal flooding GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 62 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The roadways have been assigned a high sensitivity and low adaptive capacity to bluff erosion. This is based on the premise that a roadway compromised by bluff erosion would be rendered unsafe or impassable and would require significant adaptation measures or intervention. Adaptation measures may include retreating and rerouting the roadway to a more landward alignment. It is also important to consider the temporal scale associated with bluff erosion. It is likely that bluff failures would be episodic and adaptation measures can be implemented prior to any potential impacts. The roadways identified as vulnerable are summarized and assigned vulnerability scores below in Table 7-7. It should be noted that the vulnerability score presented below only applies to these impacted roadways and should not be widely applied to roadways across the Planning Area.
Table 7-7 Roadways Vulnerability Score
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive
Capacity Vulnerability
– Access Road Coastal Flooding Low High 1
– Edwards Street
– Van Wycke Street
– Pacific Court/Azalea Way
– Ewing Street
– Scenic Drive
– Trinidad Head / Tsurewa Access
Bluff Erosion High Low 5
7.3.2 Emergency Services
Emergency services are considered to be critical assets and infrastructure. Exposure and potential impacts to emergency services were evaluated by assessing the direct impacts from climatic processes and coastal hazards. The evaluation for emergency services did not include indirect impacts, such as impaired access to specific locations due to the hazards. The emergency service facilities for the City of Trinidad include:
• Trinidad Volunteer Fire Department
• CAL FIRE Trinidad Fire Station
• Westhaven Volunteer Fire Department
• Tribal resources located at Trinidad Rancheria
• Trinidad City Hall (emergency charging location)
• Humboldt County Sheriff’s Office
• Mad River Community Hospital
The emergency services listed above are either located outside of the Planning Area (Humboldt County Sheriff’s Office and Mad River Community Hospital) or are located outside the areas expected to be impacted by tidal inundation, coastal flooding, or shoreline and bluff erosion. Thus, the emergency services are not directly vulnerable to tidal inundation, coastal flooding, or shoreline and bluff erosion. However, as stated above, this does not consider impacts to roadways and access of emergency services.
Roadways that are considered to be key routes for emergency services and exposed to hazards include Edwards Street and Scenic Drive. Edwards Street is the primary roadway leading into the Trinidad State Beach and Harbor area, also supporting several residential roads. Any impacts to the segment of Edwards Street fronting Old Home Beach would significantly impact access to the residential areas, Trinidad State Beach and the Harbor, and the Trinidad Head / Tsurewa via Lighthouse Road, as there are no alternative routes.
Scenic Drive is another key route that serves as the main accessway for the City of Trinidad and the Trinidad Rancheria. Currently, there are no alternate routes to the Trinidad Rancheria. A segment of Scenic Drive near the GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 63 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Rancheria was identified as vulnerable to bluff erosion and impacts at this location would directly impact emergency access to the Trinidad Rancheria and nearby residential areas. The potential implications would be added travel times for emergency response vehicles, which is a safety issue and would result in substantial disruptions to the community.
Scenic Drive and Edwards Street were assigned a high sensitivity and low adaptive capacity to bluff erosion. Based on the relationship between emergency services and vulnerable roadways along Edwards Street and Scenic Drive, emergency services are considered to have a high sensitivity and low adaptive capacity to bluff erosion.
Table 7-8 Emergency Services Vulnerability Score
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive
Capacity Vulnerability
Roadway access interruptions
via:
– Edwards Street
– Scenic Drive
Bluff Erosion High Low 5
7.3.3 Gas, Electric, and Communications
Privately owned utilities such as gas, electric, and communications could not be spatially located because the asset location information is not published by the private utility companies for public distribution. It is understood that gas utilities in the Planning Area are privately owned, and individual gas tanks accompany private homes or buildings. To provide an estimate of the potential impact to these utilities a surrogate resource had to be used. Roadways were selected as the surrogate resource for electric and communications. For this evaluation, it was assumed that electric and communication lines are located adjacent to roadways and are the same length as roadways. For gas utilities, it was assumed that a gas tank is located on each private home or building. A summary is provided here for the purpose of discussing impacts to gas, electric, and communications.
Based on the Planning Area roadway vulnerability, utilities have been identified as exposed to coastal flooding and bluff erosion. Roadways, therefore assumed electric and communications, are at risk for impacts from coastal flooding along Bay Street, Lighthouse Road, and Trinidad Wharf Road near Trinidad Harbor. These locations are at risk for the 100-year flood scenario for existing conditions. As SLR increases, the flood zone extends to cover the entirety of Bay Street and Trinidad Wharf Road. Depending on if the electric utilities are underground, at grade, or overhead, the potential implications of the coastal flood scenario may include power outages or malfunctions. Access to the electric and communications infrastructure may be temporarily impacted or limited within the flood zone.
Bluff erosion represents the primary hazard to coastal roadways and buildings and, therefore, is assumed to be the primary threat to gas, electric, and communications infrastructures. The locations identified as vulnerable to bluff erosion include Edwards Street, Van Wycke Street, Pacific Court and Azalea Way, Ewing Street, and Scenic Drive.
The gas, electric, and communication infrastructure are considered to have a high sensitivity and low adaptive capacity to bluff erosion impacts. The potential implications may include gas leaks or power outages.
Table 7-9 Public Utilities Vulnerability Score
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive Capacity Vulnerability
Electric/Communication
Utilities:
– Bay Street/Lighthouse
Road/Trinidad Wharf Road
Coastal Flooding Low High 1
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 64 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive Capacity Vulnerability
Gas/Electric/Communication
Utilities:
– Edwards Street
– Van Wycke Street
– Pacific Court and Azalea
Way
– Ewing Street
– Scenic Drive
Bluff Erosion High Low 5
7.3.4 Raw Water Source (Drinking Water)
The Luffenholtz Creek is the sole source of raw water for the City of Trinidad’s drinking water system. Critical community assets are dependent on surface water as the raw water source treated for drinking water and include:
• A lifeline utility system: Drinking water supply for City of Trinidad and portion of the community of Westhaven.
• Essential facilities in the City of Trinidad: Trinidad Elementary School, Trinidad City Hall, and Murphy’s Market. Trinidad City Hall has been used as an emergency shelter and charging station during intense storms and power outages and Murphy’s Market is the sole grocery store in Trinidad. • Essential facilities for tribal services for Trinidad Rancheria.
Water quality issues in Luffenholtz Creek are a known issue for the water supply operation, specifically turbidity, tannins from decaying wood and organic matter, and some septic runoff pollution (Madrone, 2008) The Luffenholtz Creek is also subject to seasonal flow patterns based on weather patterns, extractions, soils and geologic characteristics, surface and groundwater characteristics, and other factors. As is typical in the region, winter rains increase the flow in Luffenholtz Creek as directly related to individual storm events and over time as related to seasonal accumulation of precipitation in the region. The peak flow events and seasonal high flow patterns supply ample water for many uses in the watershed. It is the low flow summer period, however, that is of most interest from a water supply standpoint, for that is when water supply could become scarce and the City could see flows drop to a level where the City’s allowable extraction could be curtailed. Each year, the water system is threatened by low flows in Luffenholtz Creek. The historic low flow conditions are discussed in more detail in Section 6.2.3.
The creek flows decline in June through October until the rainy season begins. In 2020 and 2021, flows dipped to curtailed extraction levels in late August. In September 2021, the City enacted the Water Shortage Contingency Plan (adopted in 2021) Stage 2 Water Shortage Warning with a mandatory water use restriction. Even when pumping restrictions are not needed to provide the minimum bypass flows, normal pumping regimes are difficult during low flows.
As the water supply is already extremely sensitive to seasonal precipitation trends, changing climatic processes may pose additional challenges to maintaining a sufficient potable water supply in the Planning Area. The watershed is experiencing changing precipitation patterns, with more runoff and less percolation, as well as higher average temperatures and less fog. These patterns reduce dry period flows and may also change water demand characteristics. Drought, made more frequent and severe by climate change impacts, further exacerbates the system's ability to pump from the creek to ensure adequate water to meet regular demands. Extreme streamflow in the wet season may present water quality issues. Given the current limitations of the water treatment plant, excess turbidity coinciding with extreme streamflow could negatively affect the water extraction process at the City’s extraction well and water treatment plant. An expected decrease to the Planning Area clean water supply would have severe implications in the community. This may involve drinking water shortages or restrictions for residences and essential facilities.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 65 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The adaptive capacity of the Luffenholtz Creek (source water), water treatment plant and associated systems is considered to be low. This is based on the history of the water treatment plant and system; low streamflow conditions have already led to recent water restrictions and high streamflow is currently associated with turbidity that negatively influences water quality and extraction rates. Furthermore, the water distribution system is experiencing losses of around 24 to 31% due to aging infrastructure (GHD, 2019). With increasing streamflow variability, losses could be detrimental to an already limited water supply. Thus, adapting the water treatment and distribution infrastructure would require substantial intervention. The vulnerability of the raw water supply is found to be high and is presented in Table 7-10.
Table 7-10 Raw Water Supply Vulnerability Score
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive
Capacity Vulnerability
Disruption to drinking water
supply to the City of Trinidad
and portion of the community of
Westhaven
Increasing Precipitation
Variability High Low 5
7.3.5 Water Distribution System
The water distribution system contains a network of water mains that deliver water from the Trinidad Water Treatment Plant to commercial and private residences. The water mains that span the roads along the bluff top leading into the Harbor were identified as vulnerable to bluff erosion. The bluff hazard projections suggest that 380 linear feet (1% of total in Planning Area), 680 linear feet (1.8% of total) and 880 linear feet (2.3% of total) of water mains would intersect the bluff edge with 1.6 feet, 3.3 feet, and 6.5 feet of SLR. Although not within the projected bluff erosion zone, active movement of the slope and Scenic Drive roadway recently resulted in the damage of a water pipe connection. This damage resulted in a leak that depleted the City’s storage. Four water mains were identified as vulnerable to bluff erosion and are summarized below in Table 7-11 and shown in Figure 7-4.
Table 7-11 Summary of Water Distribution System Vulnerability Water Main SLR
Threshold
Description Vulnerability
Scenic Drive Current The water main along Scenic Drive is a portion of a loop that serves private
residences and the Trinidad Rancheria.
Site-specific mapping by SHN indicates
movement of the bluff slope has already
occurred, resulting in damaged pipes and
connectors that caused a leak and
depleted water storage.
Edwards Street Current The water main follows Edwards Street and leads into the residential areas near
Lighthouse Road, Galindo Street, and Van
Wycke Street.
Movement of the bluff slope suggests
vulnerability to bluff erosion. The loss of
this segment of water main would
potentially lead to cascading effects along
Lighthouse Road, Galindo Street, and Van
Wycke Street.
Van Wyke Street 1.6 ft The water main spanning Van Wycke Street serving several private residences
and converges with the Lighthouse Road
water main.
A large segment of the Van Wycke Street
water main could be comprised to bluff
erosion, potentially resulting in potable
water access issues for the residences
along the bluff.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 66 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Water Main SLR
Threshold
Description Vulnerability
Galindo Street 1.6 ft The water main spans Galindo Street serving private residences as well as a fire
hydrant near the Trinidad Pier.
The segment of water main that leads into
the fire hydrant could be compromised by
bluff erosion, potentially impacting the
Trinidad Harbor / restaurant / amenities
and may impact the functionality of the fire
hydrant.
Figure 7-3 Water distribution system vulnerability
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 67 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
The water distribution system is considered to have a medium sensitivity to bluff erosion as bluff failures may not completely impair the functionality of the system. As bluff retreat can be episodic, the extent of impacts may depend on the intensity of the episode and volume of earthflow. For instance, a minor landslide may have no effect on the system, though a major earthflow could completely impair the system. The sensitivity of water mains should be investigated further to better understand the vulnerability of the system. In addition, the water mains are considered to have a low adaptive capacity as significant intervention would be required to adapt the system. These resources are presented with a vulnerability score in Table 7-12 below.
Table 7-12 Water Distribution System Vulnerability Score Vulnerable Resource Primary Hazard
Vulnerability Score
Potential
Impact
Adaptive
Capacity Vulnerability
Water Mains:
– Scenic Drive
– Edwards Street
– Van Wyke Street
– Galindo Street
Bluff Erosion Medium Low 4
7.3.6 Stormwater
Common to most urban stormwater systems, conveyance pipes and inlets generally follow the roadways. The stormwater system is critical to minimizing negative impacts to the ASBS. The primary conveyance pipes are along Edwards Street, which follow Galindo Street to Lighthouse Road and to the infiltration basin located at the Trinidad State Beach Parking Lot. The stormwater system was identified as vulnerable to bluff erosion. The evaluation suggests that 225 linear feet of stormwater infrastructure would be impacted by bluff erosion with 1.6 feet of SLR. With
3.3 feet and 6.5 feet of SLR, approximately 400 and 510 linear feet of stormwater conveyance pipes would be impacted. This primarily occurs along Van Wyke Street and Galindo Street and along Lighthouse Road leading into the Trinidad State Beach Parking Lot. Based on an understanding of local hazard mapping and active improvement projects, Van Wyke Street is currently subjected to active bluff movement and is likely vulnerable in the near term. It is important to note that upstream stormwater mains ruptured by bluff erosion would likely have cascading effects on the downstream system. The vulnerable stormwater infrastructure is summarized below in Table 7-13 and shown in Figure 7-4, representing the area of potential impact and including the downstream stormwater mains, inlets, and infiltration basin.
Table 7-13 Summary of Stormwater Vulnerability
Stormwater Main SLR
Threshold
Description Vulnerability
Van Wyke Street /
Galindo Street Current
The stormwater main runs along Van Wyke
Street and along Galindo Street between
Edwards Street and Van Wyke Street.
The Van Wyke stormwater main is
currently experiencing stability issues due
to movement of the bluff slope and
functionality may be compromised.
Lighthouse Road 1.6 ft
The downstream stormwater main that
follows Lighthouse Road to the stormwater
infiltration basin at the Trinidad State
Beach Parking Lot.
Bluff erosion projections suggest that the
bluff top will encroach Lighthouse Road
and the corresponding stormwater main
with 1.6 ft of SLR. Impacts to this main may
cascade across the entire system as this is
the primary conveyance line to the
infiltration basin.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 68 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 7-4 Stormwater system vulnerability to bluff erosion The stormwater system is considered to have a medium sensitivity and a medium adaptive capacity to bluff erosion. In the event that a bluff failure or erosional event ruptures a stormwater conveyance line, it would not result in substantial disruptions to the community. However, there is potential that stormwater runoff would be prematurely rerouted into the ASBS and lead to water quality issues. The vulnerability score for the exposed stormwater assets is shown below in Table 7-14.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 69 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Table 7-14 Stormwater Infrastructure Vulnerability Score Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive Capacity Vulnerability
Stormwater Mains:
– Van Wyke Street / Galindo
Street
– Lighthouse Road
Bluff Erosion Medium Medium 3
7.3.7 Wastewater
Wastewater infrastructure in the Planning Area is all OWTS. The OWTS’ are primarily septic systems, with the exception of the package wastewater treatment facility that serves the Harbor amenities. The OWTS septic systems are generally buried at a depth of 1 to 3 feet BGS with leach lines between 3 and 5 feet BGS in a gravel filled trench.
Due to the lack of documentation, there is uncertainty around the status and location of many OWTS in the Planning Area. In late 2008, the City Council adopted an OWTS ordinance, establishing a septic system maintenance program for property owners in the City that requires periodic inspections and maintenance. Therefore, the City has at least some information on most of the systems within the City limits. In general, it can be assumed that the OWTS are located within most private properties and adjacent to residences.
As private residences and other buildings are located atop bluffs, the OWTS have been identified as vulnerable to bluff erosion. The sensitivity of OWTS is assumed to be generally high in areas that are anticipated to be impacted by coastal bluff erosion. This is because the evaluation suggests that impacts to residences where OWTS are located due to coastal bluff erosion are anticipated with the lowest threshold of SLR (1.6 feet). In addition, there is no community-wide wastewater infrastructure system to consolidate with and it is likely that if the OWTS is impacted by bluff erosion the associated residence / building is also impacted by bluff erosion.
The adaptive capacity of wastewater infrastructure is assumed to be generally low for two primary reasons. The first reason is that there is no community-wide wastewater infrastructure system to consolidate with. The second reason is that protective measures to prevent bluff erosion could be cost prohibitive. Adaptive capacity for private residences would need to be evaluated on a case-by-case basis as local site conditions can vary widely across the Planning Area.
The Harbor wastewater treatment facility, operated by the Trinidad Rancheria, is located behind the Harbor public restrooms. A leach field is situated in the green space between the Trinidad State Beach Parking Lot and the and access road. This system is not particularly vulnerable to coastal flooding as this treatment facility and leach field are not directly within the SLR flood zones, and substantially above groundwater elevations. The vulnerability score is presented below in Table 7-15.
Table 7-15 Wastewater Vulnerability Score
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive Capacity Vulnerability
Wastewater Infrastructure (OWTS) Bluff Erosion High Low 5 GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 70 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
7.4 Cultural, Historic, Natural, and Scenic Resource
Vulnerability
The Planning Area contains a wide range of historic, cultural, natural, and scenic resources. Portions of the Planning Area are recognized as part of the CCNM, a national recognition of scenic resources and diverse array of biological, cultural, and physical resources (USGS, 2021). The resources examined in this section generally comprise the CCNM components and surrounding resources of the Planning Area. There are several cultural, historic, natural, or scenic resources not listed or described in previous sections that are not exposed to the future coastal hazards examined in this Vulnerability Assessment. These resources include:
• City Cemetery (not a state or federal designated historic resource) • Holy Trinity Church
• Native plant garden (not a state or federal designated historic resource) • Trinidad Memorial Lighthouse (not a state or federal designated historic resource) • Trinidad Museum (not a state or federal designated historic resource) Cultural and natural resources considered in this Planning Study consist of historic properties and places, water, habitat, beaches, and recreational resources.
7.4.1 Freshwater Seeps and Streams
The sources of fresh water originate in the Trinidad-Westhaven coastal watershed, which has eight primary streams that drain from the headwaters to the Pacific Ocean. The watershed is discussed in more detail in Section 6.2.3. In summary, the freshwater streams could potentially be impacted by increasing precipitation variability and rising temperatures. These climate changes could impact both the volume of available water as well as the quality of the water. There are also many natural seeps and springs that are found along the bluff edges.
Freshwater seeps and streams have been assigned a high sensitivity and medium adaptive capacity to climatic processes (i.e., precipitation). During recent drought years low flows have been observed in Trinidad-Westhaven coastal watershed streams. Extended low flow conditions can impact water quality by raising the water temperature and increasing bacteria and algae growth. In addition, because there are no reservoirs in the watershed, wildlife are dependent on the freshwater streams and seeps to flow year-round.
Freshwater seeps and streams are considered to have a medium adaptive capacity as there are engineering controls and additional regulations and enforcement that could be done to help protect the water quality of the coastal streams and seeps. For instance, additional fencing could be put along trails in sensitive areas to prevent pets and people from entering waterways. Other adaptive measures may include additional enforcement for pet waste cleanup to help reduce water quality impacts and continued community engagement for water conservation efforts during low flow periods.
7.4.2 Trinidad Head / Tsurewa
The USGS CoSMoS hazard projections suggest that bluff retreat will alter the existing state of the headland, reducing the overall size of the headland, including the losses of cultural and historic resources contained within and limiting the useable recreational space. However, Trinidad Head / Tsurewa is a large rock outcropping and no significant erosion of the feature is anticipated. However, as described previously, the access road is vulnerable to bluff erosion. Tsurewa is a significant part of the cultural landscape, which is of sacred importance to the Tsurai Village. This resource has a medium sensitivity and low adaptive capacity to bluff erosion.
7.4.3 Habitat
The Trinidad area CCNM contains a diverse array of habitat that are critical to maintaining ecological balance, public access and recreation, natural viewsheds, and preservation of cultural heritage. Habitat within the Planning Area was GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 71 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. assessed for exposure, sensitivity, and adaptive capacity to coastal hazards and changing climatic process. This assessment focuses on the driving factors associated with each habitat resource; thus, sensitivity and adaptive capacity are not assigned. A site-specific analysis should be undertaken to better plan for project-level impacts. The vulnerability of habitat within the Planning Area is as follows:
• ASBS (kelp beds): The ASBS contains a giant kelp forest and comprises the Trinidad Bay and offshore area directly east of Trinidad State Beach. As this is a sensitive biological resource, the ASBS should consider impacts such as increased water levels with SLR, changing sediment deposition patterns, changing water temperatures and ocean pH, and stormwater discharge changes with future precipitation patterns. • Intertidal sand (beaches): The Planning Area beaches are highly vulnerable to shoreline retreat and coastal flooding. These processes will ‘squeeze’ intertidal sandy habitat against the back beach (i.e., bluff toe) as the daily tidal range increases with SLR. This habitat may transgress upslope but may be ultimately reduced as the shoreline reaches the bluff toe.
• Dunes: The coastal dunes backing Trinidad State Beach are projected to erode below the MHW shoreline with 6.6 feet of SLR. The dunes should be considered to have a high sensitivity to shoreline erosion, though the adaptive capacity is unknown at this time. Based on the setting and coastline orientation, it is unlikely that the dunes would rebound without intervention.
• Rocky intertidal: The Trinidad region coastline contains numerous offshore rocks that support a variety of biological functions, including seabird roosting and pinniped haul outs. Offshore rocks subject to more frequent inundation may result in the loss or isolation of habitat, which is critical to wildlife, though erosional forces can potentially create new rocky habitat. The vulnerability of rocky habitat was explored by the USGS (2021) by using rock height as a proxy for exposure and determined the average exposure rating to be 3.4 out of 5 for the Trinidad region, with a low sensitivity to SLR. Though it should be noted that the USGS Trinidad Unit Study Area extends far beyond the limits of the Planning Area for this assessment. • Coastal bluffs: Bluff retreat will alter the existing habitat along the bluff face. Spontaneous events such as landslides may initially harm habitat along the bluff; however, it is likely that this habitat would intermittently rebound in between erosional events. Although non-native and invasive vegetation may populate the newly disturbed areas. This process is site specific and may depend on factors such as geology and vegetation, thus further investigation is warranted to better understand the relationship between bluff erosion and habitat.
• Riparian: Riparian resources through the Trinidad-Westhaven coastal watershed could be impacted by increased precipitation variability and rising temperatures. Riparian plants that rely on perennial streamflow could be impacted if some of the streams become ephemeral systems. Each of the eight primary streams would need to be assessed during the dry season to better understand low flow conditions and potential year-round water sources, such as springs.
7.4.4 Scenic Resources
The CCNM and Scenic Drive, including the vast majority of the Planning Area, are considered to be visual resources.
The areas most exposed to impacts are those in the vicinity of the shoreline and bluffs, as increasing erosive action can alter the landscape. Flooding and erosional processes may alter the scenic nature of the shoreline; however, they are not expected to block views of the CCNM from the City.
Scenic Drive is a key route that provides access to the Planning Area viewshed and scenic resources. Based on the Vulnerability Analysis of Roadways in Section 7.3.1, segments of Scenic Drive were identified as vulnerable to bluff erosion, particularly near the Trinidad Rancheria. In the event that bluff erosion renders the road impassable, access to the Planning Areas scenic resources will be hindered. Thus, Scenic Drive as a scenic resource is considered to have a high sensitivity and a low adaptive capacity to bluff erosion.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 72 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
7.4.5 Vulnerability Summary
A summary of the historic, cultural, natural and scenic resources identified as vulnerable is provided below in Table 7-16. Scenic Drive, the Trinidad Head / Tsurewa, intertidal sand habitat (beaches) and dunes were considered to be the more vulnerable resources.
Table 7-16 Cultural, Historical, Natural and Scenic Resource Vulnerability Score Vulnerable Resource Primary Hazard
Vulnerability Score
Potential Impact Adaptive Capacity Vulnerability
Freshwater Seeps and Streams
Reduced Flows /
Rising
Temperatures
High Medium 4
Trinidad Head / Tsurewa Bluff Erosion Medium Low 3
ASBS
Precipitation
Changes, Bluff /
Shoreline Erosion
-
Intertidal Sand (Beaches) Shoreline Erosion /
Tidal inundation High Low 5
Dunes Shoreline Erosion High Low 5
Rocky Intertidal Tidal Inundation Low High 1
Bluffs Shoreline / Bluff
Erosion -
Riparian Precipitation -
Scenic Resources Shoreline Erosion /
Tidal Inundation -
Scenic Resources (CCNM/Scenic
Drive)
Bluff Erosion High Low 5
7.5 Vulnerability Summary
A summary of the resources identified as vulnerable to coastal hazards and climate change projections is provided below in Table 7-17. Based on this Vulnerability Assessment, bluff erosion and evolving precipitation patterns appear to be the predominant hazards for the Planning Area. Bluff erosion impacts a variety of resources and the corresponding potential impacts are generally high. Precipitation impacts the source water and water quality as a resource, which should be considered to be a high priority as it is a critical resource with the potential to disrupt community operations as well as the impact the community’s health and safety.
Table 7-17 Vulnerability Score Summary
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential
Impact
Adaptive
Capacity Vulnerability
Public
Access and
Recreation
Resources
Trails Shoreline Erosion / Bluff
Erosion High Medium 3
Beaches Shoreline Erosion / Flooding High Low 5
Parking Lots Flooding / Bluff Erosion Medium High 2
Amenities Flooding Medium High 2
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 73 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Vulnerable Resource Primary Hazard
Vulnerability Score
Potential
Impact
Adaptive
Capacity Vulnerability
Public Parks Bluff Erosion High Low 5
Critical
Infrastructure
and Services
Roadways, Emergency Services, Electric and Communications:
Bay Street/Lighthouse
Road/Trinidad Wharf Road Flooding Low High 1
Edwards Street
Bluff Erosion High Low 5
Van Wycke Street
Pacific Court/ Azalea Way
Ewing Street
Scenic Drive
Source Water:
Source Water / Water
Quantity
Increased precipitation
variability High Low 5
Water Distribution System:
Edwards Street
Bluff Erosion
Medium Low 4
Van Wycke Street
Galindo Street
Scenic Drive
Stormwater Infrastructure:
Van Wycke Street/Galindo
Street Stormwater Main
Bluff Erosion Medium Medium 3
Light House Road
Stormwater Main
Wastewater Infrastructure:
OWTS Bluff Erosion High Low 5
Cultural,
Historic,
Natural and
Scenic
Freshwater Seeps &
Streams / Water Quality
Reduced flows/rising
temperatures High Medium 4
Trinidad Head/Tsurewa Bluff Erosion High Low 5
ASBS - -
Intertidal Sand (Beaches) Shoreline erosion/Tidal
inundation High Low 5
Dunes Shoreline erosion High Low 5
Rocky Intertidal Tidal Inundation Low High 1
Bluffs Shoreline/Bluff Erosion -
Riparian Precipitation -
Scenic Resources
(CCNM/Scenic Drive)
Flooding/Shoreline/Bluff
Erosion High Low 5
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 74 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
8. Resilience Strategy
This resilience strategy is structured around an adaptive pathways planning approach that embeds adaptation, flexibility, and robustness into long-term strategies and plans to make informed choices to assess risk, minimize losses, and maintain resources and assets valued by the community. The approach explores and presents how options can be implemented, and sequences options to incrementally improve resiliency. The result is a living strategy that allows planners and decision-makers to better respond to uncertain and alternative futures.
Several locations and infrastructure within the Planning Area have demonstrated vulnerabilities that will continue to be exacerbated with climate change. The most significant vulnerabilities, for which local adaptation and resiliency projects may be implemented, are associated with bluff erosion and source water quantity and quality. Larger scale changes to address the causes of climate change are important but beyond the scope of the project. The following sections focus on strategies and available adaptation pathways to improve resiliency in the Planning Area and inform development of holistic approaches.
8.1 Bluff Erosion Adaptation
As discussed in Section 5 of this report, there are multiple mechanisms that contribute to bluff erosion. These mechanisms cause the bluff edge to migrate landward and impact critical infrastructure such as roadways, utilities, and emergency access; cultural and historical resources; trails and beach access; and private and public properties.
Bluff erosion in the Planning Area is caused by multiple mechanisms:
– Rainfall runoff over the bluff face causes mass wasting and erodes the surface (as is seen on trails and other unvegetated areas), resulting in the migration of the bluff edge landward. – Saturation of the underlying soils and increases to the groundwater elevation contribute to instability, causing slope movement known as slip outs and slides. Excessive precipitation, irrigation and water use, water main leaks, and septic leach fields all contribute to groundwater levels and slope saturation. – Wave action leads to erosion at the bluff toe causing destabilization of the bluff face, resulting in episodic landslide events and localized erosion at trail access to the beach.
8.1.1 Potential Projects and Vulnerabilities Addressed
Improve Stormwater, Drainage Infrastructure and Dewatering Capabilities Improvements to stormwater and drainage infrastructure can be used to reduce runoff to the bluff face and reduce over-saturation of underlying soils. The implementation of curbs and gutters to direct surface flow to a stormwater collection system can prevent runoff to the bluff face to reduce mass wasting. A secondary benefit of implementing this measure is that it can also help prevent impacts to water quality by reducing turbidity in downstream surface waters.
Implementing downspout connections to the stormdrain system, catch basins, underdrains, curtain drains and stormwater piping, and dewatering through a series of dewatering wells could be effective in lowering the water table in key areas. Installation of dewatering wells would likely require the identification and acquisition of larger properties or rights-of-way outside of the existing public right-of-way. Captured stormwater or extracted groundwater could then be conveyed to a lower elevation area for infiltration away from the bluffs or treated and discharged to surface waters.
Reduce Septic System Contributions to Groundwater and Soil Saturation Septic System Upgrades
Improving aging and undersized septic leach fields could reduce contamination to groundwater or surface waters in addition to distributing the degree of saturation in the bluff.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 75 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Wastewater Collection and Treatment Systems
Transitioning to a distributed or centralized wastewater collection and treatment system would reduce contributions to groundwater and slope saturation in addition to reducing the potential for contamination of ground water and seeps.
The benefits of implementation would improve bluff stability and groundwater and surface water quality.
Options for transitioning to a distributed or centralized wastewater treatment facility may be accomplished via small footprint systems, more commonly referred to in industry as a packaged plant(s), where aerobic wastewater treatment or a membrane bioreactor could be implemented. Other options could include a septic tank effluent pump system or similar to relocate the infiltration locations to an area that does not affect slope stability.
Wastewater Reuse
Recycled wastewater is a drought-proof alternative water source that can be used for non-potable applications. The benefits of this option are:
– Offset and reduce water needs for landscape irrigation – Reduce potable water demands
– Reduce the amount of saturation on the bluff with reduced overall water use and discharge to septic systems Water Use Reduction
Reducing the volume of water used will reduce contributions to groundwater. Water use reduction can be accomplished in multiple ways, including implementation of low flow water fixtures, limiting landscape watering, and behavioral changes.
Construct Structural Walls and Rock Buttressing
Techniques such as soldier pile, tieback, and mechanically stabilized earth (MSE) retaining walls can be used to mitigate larger coastal landslides. Rock buttressing or soil nails may be appropriate for slides less than 10 feet deep and of modest extent (SHN, 2019a). However, application of these techniques is challenging and needs to incorporate site-specific analyses in addition to considerations of the regulatory setting.
Install Bluff Toe Armoring
To address the erosion at the toe of slope due to wave action, common approaches include rock slope protection, gabion walls, structural walls similar to those described above, and bioengineering techniques that include a blend of rock and vegetative plantings. However, application of these techniques is challenging to mitigate wave erosion in addition to considerations of the regulatory setting, as some of these methods are not preferred by permitting agencies.
Retreat (Reduced Access and Alternative Routes)
Where space, time and access allow, a phased approach could be implemented to incrementally concentrate use away from the bluff edge. For example, an existing two-lane vehicle roadway may be altered to a single vehicle lane with pedestrian and bike access lane. Utility alignments, including water distribution, stormwater, and utility poles subject to damage, exposure and / or failure due to slope movement may be relocated to new landward alignments.
The new alignment and additional lateral alignments may be configured to maintain the existing level of service and reduce potential disruptions in the event of slope movement or failure. As the bluff edge retreats, the vehicle lane may be converted to pedestrian and bike only, then eventually pedestrian only. During implementation of this strategy alternative access routes can be established for future vehicle use. For example, in the past, Van Wyck Street connected Galindo Street and Edwards Street. As slope movement and erosion occurred, vehicle access was eventually no longer provided and a portion of the road alignment was converted to use as a pedestrian trail.
Continued slope movement and erosion has resulted in closure of the trail and stormwater utilities require relocation.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 76 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
8.1.2 Adaptation Pathways and Planning Areas for Bluff Erosion Adaptation
8.1.2.1 Edwards Street Planning Area
Edwards Street and other roadways and trails in the vicinity are currently exhibiting vulnerabilities to bluff erosion; these trends in the “Edwards Street Planning Area” are expected to continue. For the purposes of this study, the Edwards Street Planning Area follows Edwards Street and expands from Parker Street to the north, Galindo to the west, Wagner Street to the east, and into the Tsurai Study Area and Old Home Beach to the south (Figure 8-1). The segment of Edwards Street, between Hector Street and Van Wycke Street, provides the only roadway access to the neighborhoods and facilities west and south, including Ewing Street, Pacific Court, Galindo Street, lower Van Wycke Street, Trinidad State Beach, Trinidad Head / Tsurewa, and the Trinidad Harbor-Pier. The bluff face in this area is subjected to long-term erosional processes with episodic debris slide events (LACO, 2004). Movement of the bluff, resulting in vertical head and lateral scars and open fissures occurred in 2017, potentially threatening the section of Edwards Street between Trinity Street and Hector Street. The landslide type was noted to be generally moisturesensitive where movement was attributed to elevated pore water pressure conditions (SHN, 2017a). Several indictors suggested movement of the slope had been occurring over the previous years. Available geomorphic indicators observed in 2017 suggested the existing slide is large and deep-seated, likely encompassing all or most of the bluff face from the head scarp to the beach (SHN, 2017a). The landslide and lack of ability to stabilize portions of the slide resulted in the need for relocation of the Trinidad Memorial Lighthouse and removal of a small parking area along Edwards Street. A small buffer between the slide and Edwards Street exists but erosion and slope movement continue to be observed in this area, highlighting the urgency to embark on adaptation pathways.
While most of the runoff from hardscape, such as Wagner Street and Edwards Street, is routed down Edwards via curb, a small portion of the runoff discharges over the South Bluff. The Wagner Street Trail and Axel Lindgren Memorial Trail are located along the South Bluff and support pedestrian access to Old Home Beach. The Van Wycke Trail is also located along the South Bluff and supports pedestrian access State Beach and the Harbor. These trails have experienced ongoing settlement and erosion, with Van Wycke currently closed due to significant slope movement.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 77 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 8-1 Edwards Street Planning Area
Adaptation Pathway: Edwards Street Area
A wholistic approach and vision for the Edwards Street Area is needed that consist of multiple courses of action that can be embarked upon in parallel or sequenced as appropriate based on need and funding options. Close coordination will be needed among affected property owners and stakeholders, including but not limited to the City of Trinidad, Trinidad Rancheria, Tsurai Ancestral Society, Yurok Tribe, Coastal Conservancy, and private landowners.
Creating space between critical facilities and the bluff edge and implementing measures to reduce bluff retreat can be combined to increase resiliency. Implementing practices and infrastructure that reduce contributions to groundwater, relocation of existing utilities in proximity to the bluff edge, implementation of drainage infrastructure, incorporating trail improvements and new trail alignments, and targeted structural stabilization are all needed to provide longer-term GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 78 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. resiliency. Pathways are presented in Error! Reference source not found. and a conceptual layout of project opportunity areas and example projects are provided in Appendix C. Project opportunities are discussed below and are generally categorized as:
– Reduce Soil Saturation
– Reduce Rainfall Runoff
– Modify Existing Access
– Structural Stabilization
– Alternative Access Route
Figure 8-2 Edwards Street Area Adaptation Pathways
Reduce Soil Saturation of South Bluff
Hydrology Study
Groundwater flow was evaluated as a part of the Trinidad ASBS Stormwater Phase 1 Project (GHD, 2012). The groundwater gradients under properties along the South Bluff (Van Wyck Street, Edwards Street, and Wagner Street) in addition to properties along Parker, East and West Streets, and portions of Trinity Street, Ocean Avenue and View Avenue all flow toward the South Bluff (Figure 8-3). Building on previous studies and conducting a study that includes modeling and monitoring of ground water levels and identifying the locations and magnitude of contributions from variable seasonal precipitation, landscape watering, and septic systems is needed to prioritize actions to mitigate slope saturation.
Possible project leads: City of Trinidad
Other authorizations and partners: Private Property Owners, Tsurai Management Team, Trinidad Bay Watershed Council
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 79 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 8-3 Priority Soil Saturation Reduction Area (adapted from (GHD, 2013)) Wastewater Feasibility Study
The use of septic systems adds domestic water to the subsurface environment affecting groundwater elevations. The volume of contributions to the subsurface environment and associated groundwater elevations could be reduced by providing a wastewater collection, treatment, and discharge system. The discharge location could be sited in a location that does not contribute to groundwater elevations along the South Bluff. A study would be needed to identify and evaluate the feasibility of implementing a collection, treatment and discharge system in the context of available and applicable technologies and locations, in addition to required permitting, easements, and other factors. A wastewater system could include the use of package plants or more traditional technologies.
Possible project leads: City of Trinidad
Other authorizations and partners: Private property owners, Tsurai Management Team, Trinidad Rancheria Reduce Rainfall Runoff to South Bluff
Multiple locations along the South Bluff allow surface runoff to flow off the roadway and over the bluff edge. Runoff to the bluff edge can be reduced by implementing stormwater conveyance components, such as curbs and gutters to then convey runoff to an area suitable for stormwater best management practices (BMPs), such as rain gardens, bioswales, and infiltration galleries away from the bluff edge. Stormwater runoff flow paths could be controlled with new curbs and gutters, or other features. An existing stormdrain pipe below Edwards, along Van Wyck, is exposed and requires replacement and realignment. The project opportunity areas and example projects shown in Appendix C GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 80 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. include stormwater improvements along Van Wyck and Wagner Street, in addition to integrating stormwater BMPs in vegetated areas along Edwards Street. Trail improvement opportunities to reduce runoff on the Axel Lindgren Memorial Trail and Wagner Trail and other trails are presented in Section 8.1.2.4.
Possible project leads: Projects occurring within Edwards Street and the City right-of-way would be led by the City. Projects encroaching into the Tsurai Study Area could be led by the Tsurai Management Team.
Other authorizations and partners: Trinidad Coastal Land Trust Modify Existing Access
Currently, the primary roadway access to western Edwards Street and areas to the southwest, including neighborhoods, Trinidad State Beach and the Harbor-Pier, is from Trinity Street where it intersects Edwards at the bluff edge. Parker Street also provides a connection to Edwards via Hector Street. Parker Street and Hector Street do not exhibit the same roadway widths as Trinity and Edwards, though could be used to direct traffic to Edwards, bypassing the southern portion of Trinity. A portion of Edwards and Trinity could be converted to one-way lanes with enhanced pedestrian facilities, providing a retreat opportunity area along the South Bluff Pedestrian and bicycle access improvements along Edwards Street would also provide an opportunity for alternative trail alignments for the closed Van Wycke Trail. The project opportunity areas and example projects shown in Appendix C include modifications to the use, traffic flow and layout of Trinity Street, Parker Street, Hector Street and Edwards Street to maintain access while providing space between vehicle access and active landslides while enhancing pedestrian access. Trinity Street, between Edwards Street and Parker Street could be modified to provide additional pedestrian facilities and community gathering areas such as seating areas and additional green space. The area in the vicinity of the existing top of bluff could provide additional landscaping and interpretive opportunities. The City right-of-way along Hector Street could be developed for additional parking to mitigate any loss of parking.
Possible project leads: City of Trinidad
Other authorizations and partners: Civic Club, Tsurai Management Team, local businesses and private property owners.
Structural Stabilization
The intersection of Hector Street and Edwards Street is critical to maintaining access to the neighborhoods and facilities to the west. This intersection also includes the main water transmission line to these areas. Based on the mapping of active earthflows presented previously, this intersection is vulnerable to future erosion and slope movement. In an effort to minimize the extent of structural stabilization, the bluff in the vicinity of this intersection could be targeted and stabilized. The Coastal Geologic Hazard Assessment, City of Trinidad report by SHN, dated October 18, 2019 provides specific recommendations for the type and application of retaining walls in this vicinity and are shown in the project opportunity areas and example projects shown in Appendix C.
Possible project leads: City of Trinidad
Other authorizations and partners: Tsurai Management Team Alternative Access Route
Given the ongoing erosion and slope movement in addition to the potential for large, episodic events resulting in bluff retreat, alternative vehicle access routes from Trinity Street to neighborhoods and facilities to the southwest will be needed at some point in the future. Currently, there is no clear alternative route that would avoid the need to establish and / or purchase new right-of-way.
Possible project leads: City of Trinidad
Other authorizations and partners: Tsurai Management Team GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 81 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
8.1.2.2 Scenic Drive Planning Area
Scenic Drive is situated within a complex area of coastline, with rocky areas forming headlands and coves in between, where lower strength material is present (SHN, 2019a). The area is subject to localized mass wasting conditions and several locations are currently experiencing active earthflows that have resulted in damaged water transmission lines and settling and separation of roadway pavement. Within the Planning Area, active slides have been observed and mapped at McConnahas Mill Creek and multiple locations below the Trinidad Rancheria Tribal Offices. Similarly, several active slides and slip outs can be observed south of the Trinidad Rancheria along the roadway. The road is subject to temporary closures and several locations of single lane access. Such earthflows present an imminent threat to critical facilities such as water service (for both drinking water and fire suppression) and critical services such as emergency vehicle access. Scenic Drive provides the only roadway access to Trinidad Rancheria and several private properties and beaches to the south. The Scenic Drive Planning Area is depicted in Figure 8-4.
Figure 8-4 Scenic Drive Planning Area
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 82 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Adaptation Pathway: Scenic Drive Planning Area
Multiple courses of action can be embarked upon in parallel or sequenced. Implementation of drainage infrastructure that reduces ponding and groundwater levels can support a longer-term stabilization approach, such as welded wire type retaining walls that are already present along select locations Scenic Drive. Relocation of the water transmission line is recommended as breaks and leaks result in increased bluff saturation in addition to loss of water service. It may be necessary to reduce the level of service provided by the roadway and incorporate enhanced pedestrian and bicycle access, while reducing the current two traffic lanes. Additionally, measures to improve pedestrian access along Scenic Drive would reduce the reliance on pedestrian trails in unstable locations. These adaptation pathways are presented in Figure 8-5. Project opportunities are discussed below and are generally categorized as:
– Reduce Soil Saturation
– Repair
– Relocate Water Line
– Reduce Access and Alternative Access
Figure 8-5 Scenic Drive Area Adaptation Pathways
Reduce Soil Saturation
The roadway cut for Scenic Drive is often bound by higher ground and steepened slopes north and east (away from the coastline) and the bluff edge or steep slopes to the south and west (toward the ocean). Development upslope is typically sparse with large, vegetated areas. Drainage infrastructure, such as curbs, drain inlets and pipes exist in select locations to convey rainfall runoff and groundwater seeps away from the roadway. The addition of underdrains and additional areas of curbs, drain inlets and pipes would help reduce soils saturation and groundwater levels affecting bluff stability.
Possible project leads: City, County, Trinidad Rancheria Other authorizations and partners: Yurok Tribe
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 83 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Structural Repairs
Welded wire type retaining walls and rock buttresses are already present along portions of Scenic Drive. Some existing retaining walls may require replacement if continued movement occurs. Other localized failures may be stabilized with soldier pile walls, conventional retaining wall, mechanically stabilized earth walls, gabions or other methods, as determined appropriate depending on site conditions. Rock buttressing or soil nails may be appropriate for slides less than 10 feet deep and of modest extent (SHN, 2019a).
In order to be proactive and keep the road in operation, a bluff erosion monitoring program may be necessary to track and monitor changes along the bluffs. The City of Trinidad, Trinidad Rancheria, Humboldt County, and other stakeholders can assign staff to regularly monitor the area using field sketches and a survey team or image-based methods to document processes, rates, patterns and locations of erosion and movement. Stakeholders could also benefit from understanding and monitoring erosion across this area by using community science – a suite of tools and methods that rely on non-scientists and local community members to produce scientific data. Because bank and bluff erosion in general is complex and variable in time and space, community science methods could provide observation and reports for qualitative assessment of erosion. This method can provide useful results, alert stakeholders to sudden changes in the bluff and bank, but also keeps the community engaged with its surroundings (Van Caulart, 2023).
Possible project leads: City of Trinidad, Humboldt County, Trinidad Rancheria Other authorizations and partners: Yurok Tribe, Trinidad Coastal Land Trust Relocate Utilities
The City-owned water distribution line along Scenic Drive has been affected multiple times due to slope movement. It is recommended that action be taken to relocate these facilities landward and reconfigure lateral service connections to reduce future impacts. Additional valves and storage tanks could be installed to provide redundancy and management flexibility. This would improve the ability to isolate smaller sections of distribution lines, reducing the number of customers impacted at a given time.
Possible project leads: City of Trinidad, Trinidad Rancheria Other authorizations and partners: Private property owners Reduce Access and Alternative Access
Scenic Drive provides the only vehicle access to Trinidad Rancheria, several private properties, and multiple coastal access beaches and views. While Scenic Drive currently allows two-way traffic, several sections are limited to one lane. Highway 101 provides access to the City of Trinidad and much of the community of Westhaven. In anticipation of continued bluff retreat and associated diminished width of the roadway, traffic could be limited to local and emergency vehicles with one lane and enhanced pedestrian facilities to maintain access, similar to that shown in the project opportunity areas and example project shown in Appendix C along the eastern extent of Edwards. Structural improvements could maintain the current level of access from the City of Trinidad to the Trinidad Rancheria, and one lane local vehicle access from the Rancheria to Houda Point, where two lane access may be maintained.
Possible project leads: City, County, Trinidad Rancheria, North Coast Land Trust Other authorizations and Partners: Yurok Tribe
8.1.2.3 Trinidad Head / Tsurewa Planning Area
Significant erosion of the slope and migration of the bluff edge landward have recently occurred between the access road and cove beach west of the pier, near Seascape Restaurant. The erosion threatens the only vehicle access to the Trinidad Head Lighthouse and facilities located atop the feature. The section of access road from the gravel parking lot past the erosional area is located on Trinidad Rancheria property and the remaining access road is on City of Trinidad property. Facilities atop the Trinidad Head / Tsurewa are located on Federal Government property.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 84 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Adaptation Pathway: Trinidad Head / Tsurewa Planning Area Limited options exist to maintain vehicle access as there are no alternative routes available. Further, the existing access road achieves an approximate 10% grade and relocation of the roadway would require increasing the grade.
The access road alignment is further limited by the existing leach field associated with the package wastewater treatment facility serving the public restrooms. Structural repairs to stabilize the erosion and / or minor realignment of the roadway may be implanted to maintain vehicle access. A site-specific investigation is needed to evaluate structural repair options and further assess feasibility of re-aligning the vehicle access road while maintaining acceptable grades.
Possible project leads: Trinidad Rancheria
Other authorizations and partners: City of Trinidad, U.S. Coast Guard, and Bureau of Land Management
8.1.2.4 Trails and Beach Access Planning Areas
Several trails and beach access are currently affected by erosion along their alignment and / or toe of the bluff. Most notably, access to Old Home Beach and trails within Trinidad State Beach have been impacted, resulting in temporary closure of these trails and access.
Adaptation Pathway: Trails and Beach Access Planning Areas Multiple courses of action can be embarked upon in parallel or sequenced and require coordination among various property owners and stakeholders depending on the specific location. Common stakeholders and property owners include, but are not limited to City of Trinidad, Coastal Conservancy, State Parks, Trinidad Coastal Land Trust, Trinidad Rancheria, Tsurai Ancestral Society, and the Yurok Tribe. Adaptation pathways for trails and beaches are presented in Figure 8-6. Project opportunities are discussed below and are generally categorized as:
– Trail Maintenance
– Trail Enhancement
– Retaining Structures / Armored Toe
– Create or Direct to New Trail Alignment
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 85 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 8-6 Trails and Beach Access Adaptation Pathways
Trail Maintenance
Ongoing maintenance is considered to be activities that occur on a cycle of less than every five years (California State Parks, 2024). The intent of trail maintenance is to maintain a safe and sustainable condition to ensure safety, protect natural and cultural resources, preserve the investment, and provide use and convenience. Maintenance generally includes removal/trimming of vegetation, fallen trees, limbs and rock that are encroaching on the trail, minor grading or shaping the trail tread to maintain the intended drainage design, and repair of damaged of failed structures (California State Parks, 2024). The Tsurai Management Plan recommends the development of a trail maintenance program for the Tsurai Study Area and also provides relevant recommendations for other trials, consisting of the following (Tsurai Management Team, 2007):
– Conduct annual post-winter evaluation of trail conditions – Create a post-disturbance (e.g., landslide) Resilience Plan for unplanned events – Selective vegetation control to keep trails clear and accessible – Conduct a safety review of trails with recommendations for improvements – Evaluate appropriate uses of existing trails and where possible, enhance visitor use and access – Repair and replace signs, as needed
Trail Enhancement
Enhancement to existing trails includes measures to improve trail tread, drainage, safety, and access among other actions. Examples proposed in the Tsurai Management Plan include placement of filter fabric or week mat overlain with crushed base rock or wood chips and crowned to promote drainage, installation of interlocking trail steps, installation of cable steps where appropriate (Tsurai Management Team, 2007). Recommendations for trail enhancements include placing a layer of filter fabric overlain with crushed base rock or wood chips, minor grading or placement of material to achieve a slightly crowned geometry to promote drainage of surface water toward the edges of walking trails, water bars to guide drainage, installation of interlocking trail steps in steepened sections. Common GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 86 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. erosion control measures include rock-lined ditches, energy dissipation at discharge locations, and planting vegetative ground cover in erosional areas. Protective fencing, such as split rail, may assist in guiding users and preventing offtrail activities.
Retaining Structures / Armored Toe
Retaining structures are used to support and stabilize the trail bed, cut bank, or fill slope (California State Parks, 2024). The type of retaining structure may vary depending on site characteristics and aesthetics and includes nonstructural rock retaining walls, single tier log walls, single tier rock walls, multi-tier interlocking retaining structures, wooden cribbing, multi-tier rock retaining walls, wet masonry walls, soldier pile retaining walls with timber lagging, geotextile fabric retaining walls, cellular confinement retaining walls, and gabion basket retaining walls. These types of retaining structures may be installed along the bluff toe to reduce erosion.
Trail Realignment
In some locations, trail abandonment and/or realignment may be needed to avoid areas of continual slope movement and erosion. Realignment of trails and new trails are subject to site-specific considerations. New trail alignment opportunities along Edwards, to provide alternative access for the closed Van Wycke Trail, are shown in the conceptual layout of project opportunity areas and example projects provided in Appendix C.
Possible project leads: City of Trinidad, Humboldt County, California Department of Parks and Recreation, Trinidad Coastal Land Trust, Trinidad Rancheria, Tsurai Management Team Other authorizations and partners: Yurok Tribe
8.2 Source Water Adaptation
8.2.1 Potential Projects and Vulnerabilities Addressed
The City of Trinidad’s water treatment plant provides water to the residents of Trinidad as well as a portion of the community of Westhaven. This system relies solely on surface water from Luffenholtz Creek as its source for raw water. This dependence is what makes the source and the system critical to this community.
Because of the increased variability of annual precipitation and event intensity, source water quantity may eventually be unreliable and insufficient. Water quality also varies considerably, both during low flows and increased temperatures, as well as during intense rain events with increased turbidity.
8.2.2 Adaptation Pathways for Source Water
The dependence on the Luffenholtz Creek source water and the intermittent inability of the plant to treat water due to water quality issues limits its adaptive capacity. However, developing a suite of water system improvements and alternative sources provide opportunities to increase resiliency. Adaptive pathways for source water are shown in Figure 8-7 and generally categorized as follows:
– Improve Existing System and Storage
– Increase Local Supply
– Consolidate with Other Water Systems
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 87 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Figure 8-7 Source Water Adaptation Pathways
Improve Existing System and Storage
Existing efforts to enhance the resiliency of the water supply include an intertie project between the City of Trinidad and the Westhaven Community Services District, enabling the two distribution systems to share resources (surface water and ground water). Additionally, new storage tanks are being installed to replace aging redwood tanks and the City is considering adding raw water storage tanks that could be filled during the winter and used in late summer during low flow periods.
Pacific Watershed Associates provided several recommendations in the Overview of Luffenholtz Creek Water Resources and Water Availability (PWA, 2021) in addition to GHD findings in the Conceptual Hydrologic Assessment of Luffenholtz Creek Watershed (GHD, 2019d). Recommendations include:
1. Water conservation education and outreach to help reduce storage needs and improve water management by residents with water rights.
2. Repair current system of piping (leaky pipes).
3. Develop system design options for water storage, conservation, and stream flow diversions. a. Increase storage volume capabilities
b. Evaluate intake system to understand limitations and identify potential improvements and operational changes
4. Increase rainwater infiltration up watershed (outside the area of influence for bluff saturation) resulting in reduction in storage needed.
5. Reduce pumping rates and rotate pumping days to increase or maintain bypass flows.
6. Develop Watershed Protection and Security Program to complete a watershed evaluation, and water availability and use plan for Luffenholtz Creek. This plan will assemble useful land use, management, and planning information while also identifying potential contaminant sources, developing plans to improve water quality, identify water rights and diversions (legal and illegal), and producing a beneficial watershed water security planning tool.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 88 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
7. Increase the supply of water to the Trinidad Water system by the City to obtain winter storage and develop reservoirs, increase infiltration to the gravel aquifer and/or appropriative rights to springs in the Luffenholtz Creek watershed.
8. Evaluate scenarios that can lead to the Critical Dry Period complete analysis and planning for infrastructure to manage supply and demand during the Critical Dry Period, and developing policies for addressing low stream flows when they occur.
Increase Local Supply
Rainwater Collection Systems
Rainwater collection systems capture rainwater runoff from impervious areas such as roofs, patios, streets and driveways and convey it to storage tanks or cisterns. These types of systems vary in size and complexity and could range from a simple rain barrel to large filtration and storage tanks. Typically, rainwater is not considered potable without some kind of filtration and disinfection. The most common use of captured rainwater is landscape irrigation as it does not require filtration and disinfection. Some of the benefits of rainwater catchment is that Trinidad gets plenty of rain and it is a simple technique that only requires a water tank (barrel) to be connected to the roof down spouts.
Without installing large storage tanks on every property in Trinidad, the impact of rainwater catchment would be limited. With approximately 1000 residents, if every person had a 55-gallon rain barrel that would account for about one days’ worth of the City’s water.
Enhanced Groundwater Extraction and Spring Catchment
The use of a distributed network of a collection system using natural springs located in the Trinidad area is a potential water source for the City and was evaluated in GHD’s City of Trinidad Alternative Raw Water Source Evaluation (GHD, 2019b). The concept includes construction of a collection and treatment system close to multiple springs, which would then convey the drinking water via separate pipelines for distribution or conveyance of springs within the Luffenholtz creek watershed to the existing treatment system.
The primary benefit of this concept is the avoidance of higher turbidity levels associated with surface water flow, which can be found in both Mill and Luffenholtz creeks (Madrone, 2011). Collecting and treating water with lower turbidity levels would decrease the total amount of treatment necessary to meet the regulations set forth by the EPA.
Additionally, multiple conveyance systems could be strategically placed to efficiently distribute water to the community.
A feasibility study is needed to fully identify and understand the opportunities and constraints associated with this concept. Some preliminary considerations include maintenance needs and the permitting, right-of-way, easements and factors affecting access, development of spring locations, additional treatment facilities and associated conveyance system(s). The necessary preventative maintenance as well as any necessary repairs would need to be evaluated and compared to other available options. Potential spring locations should be further studied and evaluated with regards to required water quality monitoring as well as the feasibility of obtaining permits and/or easements needed to access and then develop a water collection and conveyance system.
An evaluation of total water supply would be needed. The springs in the Luffenholtz and Mill Creek watersheds supply a portion of the water flowing in Luffenholtz and Mill creeks. If the proposed distributed collection system would be gathering the same water further upstream as the current collection location, a comparison of reduced treatment costs to changes in maintenance and construction costs is recommended in addition to the hydrology of the creeks and changes to flow.
Additionally, a distributed spring collection system may be subject to similar vulnerabilities of drought and influences of other water users within the drainage, as presented in City of Trinidad Conceptual Hydrological Assessment of the Luffenholtz Creek Watershed (GHD, 2019d).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 89 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Use of Additional Creeks
There are three other creeks, Parker Creek, McConnahas Creek and Mill Creek, in the Trinidad area that could potentially serve as sources of raw water. There is very limited available flow data on these creeks and the use of these creeks as a supplemental water source would require more study and further data collection.
The City currently has a water right on Mill Creek that allows for a 40.4 gallons per minute extraction rate and maximum of 21.244 million gallons per year. The City is not currently exercising this water right. Parker Creek frequently has no measurable flow and there are no known existing water rights on this creek. McConnahas Creek has eight water rights and Mill Creek has nine water rights, including the City’s. As with Luffenholtz Creek, the water right does not mean that there is water available in these creeks.
Utilizing either McConnahas Creek or Mill Creek would require the construction of new diversions on the creeks.
Similar to extraction/diversion facilities as those of the existing facility on Luffenholtz Creek could be utilized. After extraction the raw water would either need to be pumped to the City’s Luffenholtz treatment plant or new treatment and disinfection facilities would need to be constructed. Construction of new facilities would entail acquiring land and access to the sites as well as new pipes for a conveyance of the water. Permitting requirements for the diversions would require significant effort and may be within the Coastal Zone.
Utilizing these creeks for an additional raw water source would be subject to the same vulnerabilities of drought and influences of other water users within the drainage, as presented in City of Trinidad Conceptual Hydrological Assessment of the Luffenholtz Creek Watershed (GHD, 2019d).
Recycled Wastewater / Reclaimed Water
Recycled water is highly treated sewage wastewater, industrial wastewater, and storm water runoff. The recycled water is treated to a high degree through filtering and processing to remove solids and impurities and is disinfected prior to use. Many municipalities utilize recycled or reclaimed water to augment their water supply. In some cases recycled water accounts for more than 20% of the total demand.
The treatment of the recycled water occurs at a wastewater treatment facility. The recycled water treatment facility requires a high level of treatment and filtration which typically have higher capital and operational costs.
Recycled water often has higher levels of total dissolved salts and nutrients. This limits the use of the water to landscape irrigation and some industrial uses. In some cases recycled water is used to recharge groundwater that is later pumped out for domestic use.
For the City of Trinidad, the use of recycled water has several limitations. The main factor is that the City does not currently have a centralized sewer collection and treatment system. Recycled water is not potable (not for human consumption) and would require a separate delivery system.
Desalination
Desalination is the process of removing salts and minerals from sea water to create potable drinking water. There are several methods for the process of desalination that entail a distillation or membrane filter process. All of these processes require sophisticated equipment and are very energy intensive. The process would require an ocean intake for the raw sea water and an outfall for the highly saline brine that is created as byproduct of the process. While desalination is technically possible, it is not currently a viable option for the City due to the high capital and operational costs, intake and outfall permitting, and potential environmental concerns from the brine outfall.
Consolidation
Connect to Humboldt Bay Municipal Water District (HBMWD) The concept of connecting the City of Trinidad to the HBMWD has been considered numerous times over the past 50 years. The idea would require extending the HBMWD system north and connecting it to the existing Trinidad water system (Winzler & Kelly, 2001). The HBMWD currently serves water to roughly 80,000 people from Ranney wells GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 90 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. located in the Mad River. The Mad River has a reliable source of water because it originates from Ruth Lake, which is a 48,000 acre-foot reservoir (Winzler & Kelly, 2001). In order for water from the HBMWD to reach the City of Trinidad, the McKinleyville Community Services District (MCSD) system would need to be utilized.
The MCSD water system was constructed with this possibility in mind and would be able to handle the increased water capacity. The water system starts at the Grant A. Ramey pump station and winds through McKinleyville until it terminates with a 12-inch pipe on Dows Prairie Road. Homes served by the MCSD system, east of the end of the line on Dows Prairie Road experience low water pressure. This is indicative of the need for an addition pump station if the distribution system is extended (Winzler & Kelly, 2001). The MCSD has considered extending the Dows Prairie Road main further to connect with more customers, which would require the installation of a new booster pump station and possibly a new storage reservoir. The installation of a new pump station and reservoir would provide the infrastructure necessary to reach the City of Trinidad water system.
The City of Trinidad water system starts at the City water treatment plant on Luffenholtz Creek near Westhaven Drive.
To connect the HBMWD to the City of Trinidad, one approach would be to construct a pipeline from the MCSD’s Dows Prairie main to the Trinidad Water Treatment Plant, where it would connect to the existing system. This approach would require the implementation of a new booster pump station as mentioned above, as well as the design and construction of a new pipeline.
In 2021, the City of Trinidad opted to not participate in a feasibility study for consolidation with HBMWD. The Trinidad Rancheria participated in the feasibility study and are now in the design phase of an extension from HBMWD to Trinidad Rancheria. It is not clear if the water infrastructure (i.e. new pump station or line size) would be adequate for future connection to serve the City as well.
Possible project leads: City, Trinidad Rancheria
Other authorizations and partners: HBMWD, MCSD
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 91 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
9. Works Cited
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Cooper, J., & Pilkey, O. (2004). Sea level rise and shoreline retreat: time to abandon the Bruun rule. Glob. Plant.
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County of Humboldt. (1981). Trinindad Area Plan of the Humboldt County Local Coastal Program. County of Humboldt.
County of Humboldt. (2007). Humboldt County General Plan Volume II Trinidad Area Plan. County of Humboldt.
County of Humboldt. (2017). Humboldt County General Plan. Eureka, California: County of Humboldt.
Department of Navigation and Ocean Development. (1977). Assessment and Atlas of Shoreline Erosion Along the California coast. Sacramento: Department of Navigation and Ocean Development. Retrieved from https://catalog.hathitrust.org/Record/000300648
Dickson, M., Walkden, M., & Hall, J. (2007). Systemic impacts of climate change on an eroding coastal region over the twenty-first century. Climatic change.
Environmental Research Consultants. (1978). City of Trinidad General Plan. Trinidad: City of Trinidad.
FEMA. (2014). Intermediate Data Submittal #3: Nearshore Hydraulics Humboldt County. BakerAECOM.
FitzGerald, D. M., Fenster, M. S., Argow, B. A., & Buynevich, I. V. (2008). Coastal Impacts Due to Sea Level Rise.
Annual Review of Earth and Planetary Sciences . doi:10.1146/annurev.earth.35.031306.140139 GHD. (2012). City of Trinidad ASBS Stormwater Improvment Project Geotechnical Analysis. Eureka, California: GHD.
GHD. (2013). Report for Trinidad ASBS Groundwater Model Technical Report .
GHD. (2016). City of Trinidad Climate Change Vulnerability Report and Adaptation Response. Eureka, California:
GHD.
GHD. (2019). City of Trinidad water demand and loss analysis memorandum .
GHD. (2019b). City of Trinidad Alternative Water Source Evaluation. Eureka.
GHD. (2019c). City of Trinidad Water Treatment Plant Production Rate Test and Analysis. Eureka.
GHD. (2019d). City of Trinidad Conceptual Hydrological Assessment of the Luffenholtz Creek Watershed. Eureka.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 92 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Grantham, T. (2018). North Coast Summary Report. California's Fourth Climate Change Assessment. Publication number: SUM-CCC4A-2018-001. University of California Berkeley.
Hapke, C. J., & Reid, D. (2007). National Assessment of Shoreline Change, Part 4: Historical Coastal Cliff Retreat along the California Coast. U.S. Geological Survey Open File Report 2007-113.
HCFSC. (2019). Humboldt County Community Wildfire Protection Plan.
Hernandez, P., Bracciano, D., Rupert, T., Wright, S., & Yeh, D. H. (2009, October). Rainwater Harvesting With Cisterns for Landscape Irrigation. Retrieved from TampaBayWater.org: https://www.tampabaywater.org/wpcontent/uploads/RWH_guide_10-28-09-1.pdf Hostler, J., & Sloan, K. (2011). Yurok Tribe and Climate Change: An Initial Prioritization Plan. Klamath, California:
Yurok Tribe Environmental Program.
IPCC. (2019). The Ocean and Cryosphere in a Changing Climate. Special report released by the Intergovernmental Panel on Climate Change. September 2019.
LACO. (2004). Engineering Geologic Assessment of the Tsurai Village with Recommendations for Future Management.
LAFCO. (2021). City of Trinidad Municipal Services Review and Sphere of Influence Update.
Madrone, S. S. (2008). Clean Water at Less Cost and with Sustainable Energy and Freedom Tanks. Prepared for the City of Trinidad.
Madrone, S. S. (2011). Fine sediment Sources in Coastal Watersheds with Uplifted Marin Terraces in Northwest Humboldt County, California. Arcata: Humboldt State University Department of Natural Resources Watershed Management.
Metcalf & Eddy. (2003). Wastewater Engineering Treatment and Reuse, Fourth Edition. New York, NY: McGraw-Hill Higher Education.
NASA. (2023, April 14). What is the greenhouse effect. Retrieved from Global Climate Change Vital Signs of the Planet: https://climate.nasa.gov/faq/19/what-is-the-greenhouse-effect/ NOAA CO-OPS. (n.d.). Datums for 9419059, Trinidad Harbor CA. Retrieved from NOAA Tides and Currents:
https://tidesandcurrents.noaa.gov/datums.html?id=9419059 OPC. (2018). State of California Sea Level Rise Guidance 2018 Update. Retrieved from https://www.opc.ca.gov/updating-californias-sea-level-rise-guidance/ OPC. (2024). State of California Sea Level Rise Guidance: 2024 Science and Policy Update – Draft Released for Public Comment. Sacramento, CA: California Natural Resources Agency.
Patton, J. R., Williams, T. B., Anderson, J. K., Hemphill-Haley, M., Burgette, R. J., Weldon,, R., . . . Leroy, T. H. (2023). 20th to 21st Century Relative Sea and Land Level Changes in Northern California: Tectonic Land Level Changes and their Contribution to Sea-Level Rise, Humboldt Bay Region, Northern California. Local Reports and Publications, 60. Retrieved from https://digitalcommons.humboldt.edu/hsuslri_local/60 Prein, A., Liu, C., Ikeda, K., Trier, S., Rasmussen, R., Holland, G., & Clark, M. (2017). Increased Rainfall Volume From Future Convective Storms in the US. Nature Climate Change 7:880-884.
PWA. (2008). Prliminary Geologic Hazard Report. Redding, CA: Pacific Watershed Associates.
PWA. (2021). Overview of Luffenholtz Creek Water Resources and Water Availability. McKinleyville, CA: PWA.
Scripps Institute of Oceanography Coastal Processes Group. (2022). California Coastal Cliff Erosion Viewer.
Retrieved from ArcGIS Cliff Erosion Viewer: https://siocpg.ucsd.edu/data-products/ca-cliff-viewer/ Scripps Institution of Oceanography. (2018). Climate, Drought, and Sea-level Rise Scenarios for the Fourth California Climate Assessment. California Energy Commission.
SHN. (2016a). Coastal Bluff Setback Analysis, 20 Scenic Drive, Trinidad. Eureka, CA: SHN.
SHN. (2016b). Supplemental Information Relative to Coastal Bluff Setback Analysis, 20 Scenic Drive, Trinidad California . Eureka, CA: SHN.
SHN. (2017a). Preliminary Assessment of Current Slope Stability Conditions, Trinidad Memorial Lighthouse, Edwards Street, Trinidad.
SHN. (2017a). Preliminary Assessment of Current Slope Stability Conditions, Trinidad Memorial Lighthouse, Edwards Street, Trinidad.
SHN. (2017b). Landslide Mitigation Assessment, Trinidad Memorial Lighthouse and Edwards Street, Trinidad, California.
SHN. (2019-2022). City of Trinidad General Plan. Trinidad: City of Trinidad.
SHN. (2019a). Coastal Landslide Hazard Evaluation, CIty of Trinidad, California. Eureka, California: SHN.
SHN. (2019b). Draft Edwards & Van Wyck Sea Level Rise and Landslide Risk Assessment and Management Plan.
Eureka, California: SHN.
SHN. (2022). Coastal Bluff Mapping, City of Trinidad, California. Eureka, California: SHN.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 93 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Streamline Planning. (2008). Trinidad-Westhaven Coastal Watershed Program - Preliminary Watershed Assessement.
Arcata.
Sweet , W. V., Hamlington , B. D., Kopp, R. E., Weaver, C. P., Barnard, P. L., Bekaert, D., . . . Zuzak, C. (2022).
Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along the U.S. Coastline. Silver Spring, MD: NOAA. Retrieved from https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf Sweet, W. V., Kopp, R. E., Weaver, C. P., Obeysekera, J., Horton, R. M., Robert Thieler, E., & Zervas, C. (2017).
Global and Regional Sea Level Rise Scenarios for the United States.
Swirad, Z. M., & Young, A. P. (2022). Spatial and temporal trends in California coastal cliff retreat. Geomorphology, Volume 412. doi:https://doi.org/10.1016/j.geomorph.2022.108318 Tetra Tech. (2020). Humboldt County Operational Area Hazard Mitigation Plan 2019; Volume 2 - Planning Partner Annexes. County of Humboldt.
Trinidad Rancheria. (2023, March 10). Comment received from Trinidad Rancheria during document review. Trinidad, California, USA: Trinidad Rancheria.
Trinidad Regional Water Management Working Group. (2008). Trinidad-Westhaven Integrated Coastal Watershed Management Plan.
Tsurai Management Team. (2007). Tsurai Management Plan. California State Coastal Conservancy.
Uitto, J. I., & Biswas, A. K. (2000). Water for Urban Areas. Shibuya-ku, Tokyo, Japan: United Nations University Press.
United States Census Bureau. (2023, April 21). data.census.gov. Retrieved from Census.gov:
https://data.census.gov/all?q=city+of+Trinidad+city,+California US EPA. (2012, March). Distinguishing LID from other Techniques that Address Community Growth Issues. Retrieved from Terminology of Low Impact Development: : https://www.epa.gov/sites/default/files/2015- 09/documents/bbfs2terms.pdf
USACE. (2021). WIS Data Portal. Retrieved from Wave Information Studies (WIS): https://wisportal.erdc.dren.mil/ USGS. (2021). Climate Change Vulnearability Assessment for the California Coastal National Monument: Trinidad and Point Arena-Stornetta Units. Reston, Virginia: U.S. Geological Survey.
USGS. (2021). Climate Change Vulnearability Assessment for the California Coastal National Monument: Trinidad and Point Arena-Stornetta Units. Reston, Virginia: U.S. Geological Survey.
Vadurro, G. A. (2021a). Foundation Soils Investigation and Geologic Hazard Evaluation Report for a Proposed Residence, 150 Scenic Drive, Trinidad; APN 042-141-003. Trinidad, CA: Vadurro.
Vadurro, G. A. (2021b). Addendum to Foundation Soils Investigation and Geologic Hazard Evaluation Report, Proposed Residential Development, 150 Scenic Drive, Trinidad, Humboldt County; APN 042-141-003 .
Trinidad, CA: Vadurro.
Van Caulart, J. A. (2023, 09 26). Recommendations for Bank and Bluff Erosion Monitoring Using Citizen Science in Walkerton, Ontario. Retrieved from UW Space: https://uwspace.uwaterloo.ca/handle/10012/19957 Winzler & Kelly. (2001). City of Trinidad Water Supply Feasibility Study. Trinidad, CA: City of Trinidad.
Yurok Tribe Environmental Program. (2007). Tsurai Management Plan. Tsurai Mangement Team.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 1 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Appendices
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 2 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Appendix A
Data Gathering & Literature Review
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 1 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Data Gathering and Literature Review
Studies and plans in the Trinidad area that are directly related to the objectives of this Planning Study are summarized below.
Trinidad General Plan (multiple document updates)
The General Plan was originally developed and adopted in 1978 and sets constraints and preferences and develops a program for development of public service facilities and private lands (Environmental Research Consultants, 1978). A draft comprehensive update to the 1978 General Plan took place in 2010 but was not adopted and additional updates are currently being developed (SHN, 2019-2022). The General Plan is comprised of narrative text and maps, as well as goals and policies for use in making land use decisions. The General Plan is organized into the seven elements required by State law and two optional elements related to Community Design and Historic and Cultural Preservation.
The City of Trinidad is also in the process of completing a comprehensive update of its entire Local Coastal Program (LCP). This consists of portions of the General Plan and Zoning, Grading, Building and Subdivision Ordinances. The Trinidad Rancheria has submitted an application to move the Harbor Properties from a fee status to a trust status on behalf of the Rancheria. The decision to approve the trust application is under consideration at this time. If approved, the Rancheria and City and other stakeholders will be working on a joint Local Coastal Plan.
The vision statement is what guides the interpretation of policies and is as follows:
Our community is situated in an area of unique natural beauty among redwood forests, beaches and sea stacks within the magnificent coastal expanse of the Pacific Ocean and Trinidad Bay. These natural riches, coupled with a quiet village atmosphere, engaged community, safe and family-friendly streets and trails, rich cultural and historical heritage and a sharp focus on environmental protection and sustainability makes Trinidad, California a welcoming, healthy and vibrant place to live.
Updates to the General Plan are in the process of development with ongoing meetings and consultation with Tribes, Rancherias and the Tsurai Ancestral Society as identified in Trinidad LCP Policy 69 and/or Senate Bill 18. An extensive public participation process is ongoing that includes community surveys and public comment sessions at Planning Commission and City Council meetings. Early public comments created the development of the following, current, strategic goals adopted by the City Council:
1. Retain the small-town character of Trinidad through sustainable development and the preservation of valuable cultural and historic assets.
2. Preserve, protect and enhance the natural setting and open spaces throughout the community providing recreational opportunities and clear views of coastline for all to enjoy.
3. Promote a strong sense of community identity and overall quality of life through continued community involvement in city government, Town Hall events and activities and the maintenance of community services including the community park, library, museum.
4. Provide for a variety of housing types to accommodate an economically and socially diverse population, while preserving the character of the community.
5. Develop planning and response strategies that help protect the citizens of Trinidad from natural disaster (including the effects of climate change).
6. Extend resource preservation and conservation to Trinidad’s water resources including the Bay and streams and overall watershed with a goal to eliminate water pollution and to ensure adequate community access to clean and pure drinking water.
7. Provide support for a mixed-use small business district (locally made products, bookstores, restaurants, clothing and gift shops) along with a vibrant fishing industry.
8. Maintain clean, quiet and safe streets, trails, residences, beaches and public properties and a welcoming entrance for visitors.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 2 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
9. Offer safe and accessible transportation options, adequate parking and sensible traffic rules to ensure public safety and minimize traffic congestion.
10. Embrace the environmental practices and technologies necessary to help offset the negative impact of Climate Change
11. Work toward the goal of becoming a Zero Waste, Net Carbon Neutral community.
Modifications to the strategic goals may be implemented in future revisions based on additional collaboration with Tribal Governments and surrounding communities.
Trinidad Area Plan of the Humboldt County Local Coastal Program (LCP) (County of Humboldt, 1981)(2007 update)
Coastal Act Goals and Policies
The LCP must be certified by the Coastal Commission as consistent with and adequate to carry out policies and regulations of the Coastal Act of 1976 (Coastal Act). By enacting the Coastal Act, the state legislature adopted the flowing goals:
a. Protect, maintain and, where feasible, enhance and restore the overall quality of the coastal zone environment and its natural and man-made resources.
b. Assure orderly, balanced utilization and conservation of coastal zone resource, taking into account the social and economic needs of the people of the state
c. Maximize public access to and along the coast and maximize public recreational opportunities in the Coastal Zone consistent with sound resource conservation principles and constitutionally protected rights of private property owners.
d. Assure priority for coastal-dependent development over other development on the coast. e. Encourage state and local initiatives and cooperation in preparing procedures to implement coordinated planning and development for mutually beneficial uses, including educational uses, in the Coastal Zone.
Local Coastal Program (LCP)
The LCP was first approved by the Humboldt County Board of Supervisors in 1981 and adopted in 1984, then partially certified by the State California Coastal Commission in 1982 and 1983. The most recent publication was in 2014.
The Trinidad Area Plan highlights the protection of the following uses:
Use Protection
Resource Protection
Coastal Commercial Timberland Timberland Preserve Zoning Sensitive Environments
Riparian Habitat and Coastal
Streams
Intertidal Areas
Offshore Rocks
Riparian setbacks and use restrictions
Limits to access and significant impacts to biological system Recreation
Su-meg State Park (formerly Patrick’s Point)
Trinidad State Beach
Luffenholtz County Park
Future Demand/Support Facilities
Designated Public Recreation
Designated Commercial Recreation
Transportation Corridors
Patrick’s Point Drive
Stagecoach Road
Limit encroachments, area population density, parking
provisions and Scenic Drive, Stagecoach Road and Highway 101 scenic policies
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 3 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Use Protection
Scenic Drive
Westhaven Drive
Engineering Geologic Assessment of the Tsurai Village with Recommendations for Future Management (LACO 2004)
During preparation of the Tsurai Management Plan LACO Associates conducted an Engineering Geologic Assessment of the Tsurai Village with Recommendations for Future Management. This study concludes that wave and tidal processes, earthquakes and ground shaking and increased groundwater elevations are contributing factors to bluff instability in and around the Tsurai Village. The LACO study also concludes that the diversion, concentration and improper discharge of surface runoff onto the slopes above and on Tsurai Village is also a contributing factor to bluff instability. Surface water contributions are being supplied from runoff on hardscape surfaces such as rooftops, driveways and patios. In addition, the study states that excessive landscape irrigation, densely spaced and undersized septic leach fields and the addition of new leach fields from continued development are all contributing factors.
Tsurai Management Plan (Yurok Tribe Environmental Program, 2007) The Tsurai Management Plan (TMP) identifies it’s development as a result of a three-year collaborative effort by representatives of the California State Coastal Conservancy, City of Trinidad, Tsurai Ancestral Society and the Yurok Tribe. The plan provides specific recommendations and future projects intended to help protect, preserve and where possible restore, the cultural, natural and recreational resources within the Tsurai Study Area (TSA) for the benefit of future generations. Furthermore, the natural resources contained within the TSA are components of a larger environmental area, directly adjacent to a designated Critical Coastal Area (CCA) (ASBS) Trinidad Bay. Just as the TSA contains irreplaceable cultural resources, the TSA borders a unique biological marine area, due to its unique coastal and marine resources. The Trinidad Bay is protected because of its status as an ASBS/CCA under state and federal law. The Tsurai Management Team has collaborated to identify problems, potential solutions and make specific recommendations to ensure to long-term viability of natural resources within and adjacent to the TSA.
Key findings and recommendations from the Management Team include:
– Installation of a handrail on the Axel Lindgren Memorial Trail to provide safer use of this primary beach access trail by the public;
– Development and installation of signs throughout the TSA to direct user traffic and protect environmental and cultural resources contained therein;
– Analysis and mitigation of the runoff and saturation issues that are impacting the Tsurai Village site; – Completion of a comprehensive botanical and vegetation survey of the TSA with recommendations for select vegetation removal to improve site conditions and assist in the removal of invasive species; – Development of a Vegetation Management Plan with a protocol for reviewing and making decisions on management of vegetation within the TSA; and
– Continued collaboration between the Coastal Conservancy, City, Tsurai Ancestral Society and Yurok Tribe on the future management of the TSA via the continuation of the Tsurai Management Team through implementation of the Management Plan.
Preliminary Geologic Hazard Report (PWA, 2008)
This report documents Pacific Watershed Associates’ geologic hazard assessment investigation of two properties in the vicinity of Hector Street, as required by the City of Trinidad’s 1980 General Plan, that discusses the impact development might have on the geologic stability of the project site and surrounding vicinity. The report identifies areas of prior slope instability and contributing factors, such as saturation of soils, and provides recommendations the for proposed building area, seismic design, control of rainfall runoff, native vegetation and onsite wastewater treatment system.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 4 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Trinidad-Westhaven Integrated Coastal Watershed Management Plan (City of Trinidad, 2008a)
This plan was a collaboration between the City of Trinidad, the community of Westhaven and the Trinidad Rancheria to identify water quality problems and design practical, community-oriented solutions. The plan identified nine priority watersheds that have the greatest influence on water quality in the Trinidad Head Area of Special Biological Significance (ASBS) and coastal waters. The plan addresses wastewater, stormwater runoff and sediment as highpriority issues. Adaptation or management actions identified in the plan include:
• Water quality monitoring
• Onsite Wastewater Treatment System (OWTS)
management
– Financial incentives
– Issue operating permits
– Maintenance contracts
– Septic and leach field maintenance
• Road-related sediment reduction
– BMP for road maintenance
– Road treatments on high-priority sites
• Public outreach
– Watershed education
– Road maintenance
– Erosion control
– Sediment source reduction
– Water conservation
– Newsletter for watershed residents
• Water conservation
– Financial incentives
– Water meters
– Leak identification
• Stormwater management
– Trinidad/ Mill Creek and Luffenholtz Creek
watershed drainage improvements
– Promote Low Impact Development (LID)
– Stormwater management plan
– Permeable paving project
Results of Factor-of-Safety Analysis and Erosion Rate Assessment (Busch, 2009) This report provides a discussion and results of an analysis of erosion rates of the base of the bluff and the top of the bluff near a proposed residential development on Edwards Street. The report utilizes information from PWA 2008 and is focused on the risk to the homesite. The report identifies that the most likely static failure of the bluff is the continued slumping and translational sliding of an existing failure above the beach and secondarily, a new slump or slide above the existing failure. The report identifies the potential for a “flake” failure of the outermost area of the top of bluff that would undermine Edwards Street.
City of Trinidad ASBS Stormwater Improvement Project Geotechnical Analysis (GHD, 2012) This geotechnical analysis was conducted as a part of the Trinidad Area of Special Biologic Significance (ASBS) Stormwater Improvement Project to make improvements to the municipal stormwater drainage system. The analysis was conducted to support the design and implementation of Low Impact Development Best Management Practices for stormwater, such as retention, treatment and infiltration features, throughout the City to protect the ASBS. The analysis included geophysical investigations to indicate the hydrogeologic setting and the location and extent of the marine terrace aquifer and Franciscan bedrock.
As part of the mitigations to reduce non-point source pollution, the Trinidad Rancheria stated that they will also be mitigating storm water runoff from Trinidad Harbor from the asphalt parking lot near the public restrooms and wastewater treatment plant extending towards Launcher Beach (Trinidad Rancheria, 2023).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 5 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
FEMA Coastal Flood Study for Humboldt Bay (FEMA, 2014)
The Federal Emergency Management Agency (FEMA) performed a detailed coastal engineering analysis and mapping for the Pacific coast of California. Tidal still water levels, wind waves and wave runup were analyzed to generate predictions for total water levels along the shoreline for current conditions (not reflecting sea level rise projections). Total water levels along the Trinidad Shoreline range from 18 to 25 feet (ft) NAVD88.
City of Trinidad Climate Change Vulnerability Report and Adaptation Response (GHD, 2016) This report presents some of the potential effects that could result from climate change, determines the resulting areas at risk relevant to the City and identifies preliminary adaptation strategies that could help mitigate the risk identified.
The document highlights the physical effects of global warming, sea level rise, precipitation and wildfire. Vulnerabilities and adaptation recommendations are shown below:
Global Warming Sea Level Rise Precipitation Wild Fire
Vulnerabilities – Water Supply – Public beaches
– Coastal bluff
erosion
– Harbor operations
– Land use adjacent
to bluffs
– Stormwater
infrastructure
– Water diversion and
treatment facilities
– Land use
– Power lines
– Water supply and
treatment facilities
Adaptation – Establish mapped hazard zones or overlays
– Continued climate change evaluation
– Promote Fire Safe Communities
– Evaluate current and future water demands to assess adequacy of available water storage – Establish water shortage contingency plan
– Increase water conservation
– Evaluate water treatment system performance
– Control stormwater runoff and pollution
– Establish shoreline management plans to address long-term sea-level-rise – Limit new development in hazard areas
– Develop a plan to remove or relocate structures that become threatened – Plan ahead to replace loss of access and recreation areas – Foster efforts to better understand impacts of sea level rise Coastal Bluff Setback Analysis, 20 Scenic Drive, Trinidad California (SHN, 2016a) and Supplemental Information Relative to Coastal Bluff Setback Analysis, 20 Scenic Drive, Trinidad California (SHN, 2016b)
The analysis is focused on the issues related to stability of the coastal bluff and recommended setback at 20 Scenic Drive, in the southeastern area of the City of Trinidad, for the addition of structures on the property. Setback calculations followed a procedure defined Establishing Development Setbacks from Coastal Bluffs by M.J. Johnson (2005). A suitable bluff setback was defined as that which is subject to sufficiently low slope failure hazard to allow the residential structure(s) to exist without contributing to, or being subject to, substantial geologic instability during the design life (defined as 75 years by the California Coastal Commission) of the residence. The method includes evaluation of historical bluff retreat and slope stability analyses. The stability modeling indicated a setback of 35 feet and the historical bluff retreat rate of 0.12 ft/yr at the project site. The supplemental document provides additional information and concludes that the development of the site is consistent with the relevant LCP provisions and that the subject terrace is not an unstable landform.
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 6 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Preliminary Assessment of Current Slope Stability Conditions, Trinidad Memorial Lighthouse, Edwards Street, Trinidad (SHN, 2017a)
The report presents the results of a visual assessment of slope conditions and included site reconnaissance, preliminary mapping of scarps and review of existing published and unpublished geologic and geotechnical data.
Vertical head and lateral scarps and open fissures were observed. Available geomorphic indicators suggested the slide was large and deep-seated, likely encompassing all or most of the bluff face below the head scarp along the southern edge of the parking area along Edwards Street. The source of the landslide was at least partially attributed to moisture sensitivity and the high levels of rainfall that year. Interim measures to discourage the public from using the affected areas were recommended and additional work identified.
Landslide Mitigation Assessment, Trinidad Memorial Lighthouse and Edwards Street, Trinidad, California (SHN, 2017b)
The report presents the initial phase of investigations to provide conceptual slope stabilization alternatives to protect Edwards Street and the Trinidad Memorial Lighthouse from the most threatening portion of the landslide complex described in SHN 2017a. Relocation of the lighthouse was recommended and Edwards Street was deems to be exposed to a lesser immediate risk factor. However, the head of the landslide was expected to continue to encroach toward Edwards Street. A retaining wall system was recommended to preserve the full traveled roadway width of Edwards Street. Stabilization of the entire landslide complex was not a part of the study. Portions of the landslide that are located below any proposed soil reinforcement or retaining system were noted to likely continue to move downslope after the slope repair is constructed.
Humboldt County General Plan (County of Humboldt, 2017) The Safety Element of the Humboldt County General Plan incorporates by reference a countywide multi-agency local hazard mitigation plan and flood hazard mitigation plan. The plans provide ongoing and systematic programs to reduce or eliminate long-term risks from natural hazards. Relevant natural hazards for Trinidad include intensified severe weather, wildland fire, flooding and tsunamis. Concerns relevant to sea level rise are addressed by limiting development within the tsunami run-up area. The document outlines the limitations and requirements for development on or adjacent to coastal bluffs and beaches. Development in these areas may be allowed if it can be demonstrated by a certified engineering geologist that wave action, storm swell, tsunami inundation and projected sea level rise are not a hazard to the proposed development.
California Coastal Commission Sea Level Rise Policy Guidance: Interpretive Guidelines for Addressing Sea Level rise in Local Coastal Programs and Coastal Development Permits (Coastal Commission, 2018)
This guidance document focuses on how to apply the Coastal Act to challenges due to sea level rise through the Local Coastal Program (LCP) and Coastal Development Permit (CDP) processes.
Vulnerabilities include loss of land resources, such as:
• Development and infrastructure
• Public access and recreational opportunities
• Beaches
• Wetlands
• Environmentally sensitive habitat areas (ESHA)
• Other coastal habitat
• Agricultural resource
• Water quality
• Archaeological and paleontological resource
• Scenic and visual resources
General Recommendations include:
• Relocate or remove existing development out of hazard areas • Limit the construction of new development in vulnerable areas GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 7 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Coastal Act Requirements include:
• New development be sited and designed to be safe from hazards and to not adversely impact coastal resources • Mandates to maximize public access and recreational opportunities to and along the coast • Mandates that ESHA and marine resources shall be protected against significant disruption of habitat value and shall be maintained, enhanced and restored as feasible
Trinidad Annex Local Hazard Mitigation Plan (Tetra Tech, 2020) The Local Hazard Mitigation Plan (LHMP) provides a summary of the capabilities for implementing hazard mitigation strategies and identifies opportunities to expand, initiate or integrate capabilities to further hazard mitigation goals and objectives. Recommended actions in the LHMP are summarized below:
• Support retrofitting, purchase or relocation of
structures located in hazard areas
• Integrate the hazard mitigation plan into other
plans, ordinances and programs
• Actively participate in the LHMP maintenance
protocols
• Develop and adopt a capital improvement plan
that addresses hazards and climate change
impacts
• Update Trinidad Emergency Operation Plan
• Support County-wide initiatives of the hazard
mitigation plan
• Work with the County of Humboldt on the
development of Regional Planning Documents
• Repair Van Wycke Trail storm damage and
relocate vulnerable water line and storm drain
along Van Wycke Street
• Improve resiliency of water system
• Implement priority actions in the County
Community Wildfire Plan (CWPP), including
developing collaborative partnerships,
participating in a wildfire preparedness program
and addressing water system and firefighting
water supply needs
• Attain certifications of Storm Ready and
Tsunami Ready in collaboration with interested
local support agencies
Coastal Landslide Hazard Evaluation, City of Trinidad, California (SHN, 2019a) This report was developed to inform the City of Trinidad’s Coastal Hazard Management Plan and provides an assessment of coastal landslide hazards within the City. The report characterizes landslide hazards along the coastline of Trinidad to identify the exposure of City infrastructure and private properties to these hazards and identifies alternative mitigation measures.
Landslide hazards along Trinidad’s shoreline range from low to moderate to high and recommendations are based on a range of scales from large-scale slides and shallow slide planes. Recommendations include:
Large-scale:
– avoidance
– soldier pile
– tie-back retaining wall
Modest Scale:
– welded wire type retaining wall
Small-scale:
– smaller soldier pile type walls, conventional
retaining walls
– mechanically stabilized earth walls
– gabions
Shallow slide plane:
– buttress at the slide toe
– mechanically stabilize the slide mass (i.e. soil nails) GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 8 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Draft Edwards & Van Wycke Sea Level Rise and Landslide Risk (SHN, 2019b) This assessment focuses on the segment of shoreline described in Coastal Landslide Hazard Evaluation (SHN, 2019a) and provides a discussion based on the Coastal Commission’s Sea Level Rise Policy Guidance Chapter 5 – Addressing Sea Level Rise in LCPs (Coastal Commission 2018) and the City of Trinidad Climate Change Vulnerability Report and Adaptation Response (GHD, 2016). The report focuses on identifying LCP adaptation strategies to minimize risk, based on the exposure, sensitivity, adaptive capacity, consequences and land use constraints related to City infrastructure, trails and public access, private development, environmentally sensitive habitat areas (ESHA) and the environment and cultural resources. The discussion identifies managed retreat and stabilization as the only feasible options for the Edward and Trinity Street Slide; stabilization as the preferred option for the Van Wycke Trail to preserve access; stabilization for the Edwards and upper Van Wycke Earthflow to protect access to the harbor.
Foundation Soils Investigation and Geologic Hazard Evaluation Report for a Proposed Residence, 150 Scenic Drive, Trinidad (Vadurro, 2021a) and Addendum (Vadurro, 2021b) This report presents the results of a focused investigation of foundation soils and geologic hazard evaluation for the construction of a new residence. The report provides an assessment of coastal bluff stability hazards and provides recommendations in support of design and construction of the proposed residence. The addendum provides additional information regarding future fluff retreat due to sea level rise, assessment of slope protection and other information requested by the City of Trinidad. The addendum identifies that the site is located in an area of rocky coastline and no discernable landward retreat dating back to 1958 has occurred and that the rock slope protection will likely achieve a 75-year design life.
City of Trinidad Municipal Services Review and Sphere of Influence Update (Humboldt Local Agency Formation Commission (LAFCO), 2021)
The purpose of this assessment was to update the municipal services review (MSR) and sphere of influence (SOI) for the City of Trinidad. The objective was to provide relevant information and data necessary for the Commission to make informed decisions about the SOI. This included a comprehensive review and inventory of the service area and services provided in the City of Trinidad, including water, OWTS maintenance, storm water, streets & Roadways, parks & recreation, law enforcement, fire protection and emergency planning.
Climate Change Vulnerability Assessment for the California Coastal National Monument:
Trinidad and Point Arena-Stornetta Units (USGS, 2021)
The California Coastal National Monument provides protection to islets, reefs and rock outcrossing habitats in six onshore units, one of which includes the Trinidad area. The document summarizes the outreach conducted, climate change vulnerabilities and indicator species and a quantitative sea level rise vulnerability assessment for rocky shoreline resources. The study discusses that climate change will likely affect the Trinidad area in a variety of ways, including changes in ocean conditions (temperature, pH), storm frequency and intensity and precipitation and fog patterns, with sea level rise contributing the greatest effects on low elevation offshore rocky features and more sensitive species.
Coastal Bluff Mapping, City of Trinidad, California (SHN, 2022) This report presents the current location of the top of the “coastal bluff” within the Trinidad City limits, mapped by SHN’s geologist. The purpose of the mapping was to provide the City’s planners, decision makers and the public with maps to inform coastal planning decisions and regulatory criteria that may be contingent on the proximity to the coastal bluff. The “coastal bluff” is defined in the Coastal Act as “those bluffs, the toe of which is now or was historically (generally within the last 200 years) subject to marine erosion” (California Code of Regulations, Title 14, Sec 13577 (h)(1)).
Other Studies Reviewed
– Humboldt County General Plan Volume II Trinidad Area Plan (County of Humboldt, 2007).
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 9 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. – Humboldt Regional Climate Resilience Plan Public Review Draft – California’s Fourth Climate Change Assessment (Grantham, 2018) – California Adaptation Planning Guide (Cal OES, 2020)
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 10 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Appendix B
Coastal Hazards & Sea Level Rise
Vulnerability Figures
!.G
COLLEGE COVE PARK
College
Cove
Trinidad
State Beach
to Elk Head
Central Planning Area
FIGURE A.1
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Northern Planning Area
Base Flood Elevation - 0 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_001_VA_BFE_2023_DDP
Print date: 14 Jun 2024 - 07:10
ASSETS
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 0 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad Central
Planning
Area
Southern
Planning
Area
Northern
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
MAIN ST
LANFORD RD
EWING
ST
AZALEA
WAY
STAGE
COACH RD
STATE HWY 101
PACIFIC C T
101 OFF RAMP
STATE HWY
SCENIC DR
HIGHWAY 101
UNDER PASS
VAN WYCKE ST
VIEW AVE
PATRICKS
POINT DR
GALINDO ST
VAN WYCKE ST
TRINITY ST
WEST ST PARKER ST
E DWARDS ST
EAST ST
HE
CTO
R ST
OC
EANAVE
LIGHTHOUSE RD
WAGNER ST
PARKER CREEK DR
GROTH LN
STATE HWY 101 ON RAMP
STATE HWY 101 OFF RAMP
UNDERWOOD DR
STATE PARK RD
N WESTHAVEN DR
Wagner
St Tr
Trinidad
Head Tr
Galindo
St Tr
Axel
Lindgren
Mem. Tr
Parker
Cr Tr
Trinidad
State Beach
to Elk Head
Lighthouse
Rd Tr
Public
Restrooms *
Seascape
Restaurant *
Launcher
Beach
Pier *
Trinidad
State
Beach
City of
Trinidad
Boat
Launch *
Old Home
Beach
Northern
Planning Area
Southern
Planning Area
FIGURE A.2
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Central Planning Area
Base Flood Elevation - 0 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 60 120 180 240 300
Feet
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_001_VA_BFE_2023_DDP
Print date: 14 Jun 2024 - 07:10
ASSETS
G!. Hydrants
Water mains
Existing trails
Stormwater main
Public Parking
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 0 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Southern
Planning
Area
Central
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
PA-PAH
LN
SCENIC DR
CHER-AELN
BAKER RANCH RD
LANFORD RD
STATE HWY 101
MA-WE MORE VIEW LN
Central Planning Area
FIGURE A.3
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Southern Planning Area
Base Flood Elevation - 0 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_001_VA_BFE_2023_DDP
Print date: 14 Jun 2024 - 07:10
ASSETS
G!. Hydrants
Water mains
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 0 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Central
Planning
Area
Southern
Planning Area
!.G
STATE PARK RD
COLLEGE COVE PARK
College
Cove
Trinidad
State Beach
to Elk Head
Central Planning Area
FIGURE B.1
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Northern Planning Area
Base Flood Elevation - 1.6 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_002_VA_BFE_2050_DDP
Print date: 14 Jun 2024 - 07:30
0 50 100 150 200 250
Feet
ASSETS
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 1.6 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad Central
Planning
Area
Southern
Planning
Area
Northern
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
MAIN ST
LANFORD RD
EWING
ST
AZALEA
WAY
STA
GECOACH RD
STATE HWY 101
PACIFIC C T
101 OFF RAMP
STATE HWY
SCENIC DR
HIGHWAY 101
UNDER PASS
VAN WYCKE ST
VIEW AVE
PATRICKS
POINT DR
GALINDO ST
VAN WYCKE ST
TRINITY ST
WEST ST PARKER ST
EDWARDS ST
EAST ST
HE
CTOR S
T
OC
EANAVE
LIGHTHOUSE RD
WAGNER ST
PARKER CREEK DR
GROTH LN
STATE HWY 101 ON RAMP
STATE HWY 101 OFF RAMP
UNDERWOOD DR
STATE PARK RD
N WESTHAVEN DR
Wagner
St Tr
Trinidad
Head Tr
Galindo
St Tr
Axel
Lindgren
Mem. Tr
Parker
Cr Tr
Trinidad
State Beach
to Elk Head
Lighthouse
Rd Tr
Public
Restrooms *
Seascape
Restaurant *
Launcher
Beach
Pier *
Trinidad
State
Beach
City of
Trinidad
Boat
Launch *
Old Home
Beach
Northern
Planning Area
Southern
Planning Area
FIGURE B.2
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Central Planning Area
Base Flood Elevation - 1.6 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_002_VA_BFE_2050_DDP
Print date: 14 Jun 2024 - 07:30
0 60 120 180 240 300
Feet
ASSETS
G!. Hydrants
Water mains
Existing trails
Stormwater main
Stormwater Appurtenances
Public Parking
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 1.6 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Southern
Planning
Area
Central
Planning
Area
G!.
G
G!.
G!.
G!.
G!.
G!.
G!.
PA-PAH
LN
SCENIC DR
CHER-AELN
BAKER RANCH RD
LANFORD RD
STATE HWY 101
MA-WE MORE VIEW LN
Central Planning Area
FIGURE B.3
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Southern Planning Area
Base Flood Elevation - 1.6 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_002_VA_BFE_2050_DDP
Print date: 14 Jun 2024 - 07:30
0 50 100 150 200 250
Feet
ASSETS
G!. Hydrants
Water mains
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 1.6 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Central
Planning
Area
Southern
Planning Area
!.G
STATE PARK RD
COLLEGE COVE PARK
College
Cove
Trinidad
State Beach
to Elk Head
Central Planning Area
FIGURE C.1
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Northern Planning Area
Base Flood Elevation - 3.3 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_003_VA_BFE_2070_DDP
Print date: 14 Jun 2024 - 07:31
0 50 100 150 200 250
Feet
ASSETS
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 3.3 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad Central
Planning
Area
Southern
Planning
Area
Northern
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
MAIN ST
LANFORD RD
EWING
ST
AZALEA
WAY
STAGE
COACH RD
STATE HWY 101
PACIFIC C T
101 OFF RAMP
STATE HWY
SCENIC DR
HIGHWAY 101
UNDER PASS
VAN WYCKE ST
VIEW AVE
PATRICKS
POINT DR
GALINDO ST
VAN WYCKE ST
TRINITY ST
WEST ST PARKER ST
E DWARDS ST
EAST ST
HE
CTO
R ST
OC
EANAVE
LIGHTHOUSE RD
WAGNER ST
PARKER CREEK DR
GROTH LN
STATE HWY 101 ON RAMP
STATE HWY 101 OFF RAMP
UNDERWOOD DR
STATE PARK RD
N WESTHAVEN DR
Public
Restrooms *
Seascape
Restaurant *
Launcher
Beach
Pier *
Trinidad
State
Beach
City of
Trinidad
Boat
Launch *
Old Home
Beach
Wagner
St Tr
Trinidad
Head Tr
Galindo
St Tr
Axel
Lindgren
Mem. Tr
Parker
Cr Tr
Trinidad
State Beach
to Elk Head
Lighthouse
Rd Tr
Northern
Planning Area
Southern
Planning Area
FIGURE C.2
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Central Planning Area
Base Flood Elevation - 3.3 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_003_VA_BFE_2070_DDP
Print date: 14 Jun 2024 - 07:31
0 60 120 180 240 300
Feet
ASSETS
G!. Hydrants
Water mains
Existing trails
Stormwater main
Stormwater Appurtenances
Public Parking
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 3.3 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Southern
Planning
Area
Central
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
PA-PAH
LN
SCENIC DR
CHER-AELN
BAKER RANCH RD
LANFORD RD
STATE HWY 101
MA-WE MORE VIEW LN
Central Planning Area
FIGURE C.3
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Southern Planning Area
Base Flood Elevation - 3.3 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_003_VA_BFE_2070_DDP
Print date: 14 Jun 2024 - 07:31
0 50 100 150 200 250
Feet
ASSETS
G!. Hydrants
Water mains
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 3.3 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Central
Planning
Area
Southern
Planning Area
!.G
STATE PARK RD
COLLEGE COVE PARK
College
Cove
Trinidad
State Beach
to Elk Head
Central Planning Area
FIGURE D.1
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Northern Planning Area
Base Flood Elevation - 6.6 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_004_VA_BFE_2100_DDP
Print date: 14 Jun 2024 - 07:33
ASSETS
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 6.6 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad Central
Planning
Area
Southern
Planning
Area
Northern
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
MAIN ST
LANFORD RD
EWING
ST
AZALEA
WAY
STAGE
COACH RD
STATE HWY 101
PACIFIC C T
101 OFF RAMP
STATE HWY
SCENIC DR
HIGHWAY 101
UNDER PASS
VAN WYCKE ST
VIEW AVE
PATRICKS
POINT DR
GALINDO ST
VAN WYCKE ST
TRINITY ST
WEST ST PARKER ST
E DWARDS ST
EAST ST
HE
CTO
R ST
OC
EANAVE
LIGHTHOUSE RD
WAGNER ST
PARKER CREEK DR
GROTH LN
STATE HWY 101 ON RAMP
STATE HWY 101 OFF RAMP
UNDERWOOD DR
STATE PARK RD
N WESTHAVEN DR
Wagner
St Tr
Trinidad
Head Tr
Galindo
St Tr
Axel
Lindgren
Mem. Tr
Parker
Cr Tr
Trinidad
State Beach
to Elk Head
Lighthouse
Rd Tr
Public
Restrooms *
Seascape
Restaurant *
Launcher
Beach
Pier *
Trinidad
State
Beach
City of
Trinidad
Boat
Launch *
Old Home
Beach
Northern
Planning Area
Southern
Planning Area
FIGURE D.2
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Central Planning Area
Base Flood Elevation - 6.6 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 60 120 180 240 300
Feet
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_004_VA_BFE_2100_DDP
Print date: 14 Jun 2024 - 07:33
ASSETS
G!. Hydrants
Water mains
Existing trails
Stormwater main
Stormwater Appurtenances
Public Parking
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 6.6 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Southern
Planning
Area
Central
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
PA-PAH
LN
SCENIC DR
CHER-AELN
BAKER RANCH RD
LANFORD RD
STATE HWY 101
MA-WE MORE VIEW LN
Central Planning Area
FIGURE D.3
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Southern Planning Area
Base Flood Elevation - 6.6 Ft Sea Level Rise
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
Data sources: NOAA, USGS CoSMoS, GHD; Imagery: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA World Imagery: Maxar, Microsoft. Created by: zporteous
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_004_VA_BFE_2100_DDP
Print date: 14 Jun 2024 - 07:33
ASSETS
G!. Hydrants
Water mains
Existing trails
SEA-LEVEL RISE SCENARIO
Coastal Flood Zones: 6.6 ft of Sea Level Rise
Tidal Inundation Zone
Coastal Flood Zone
Still Water Elevation
DRAFT
Data Disclaimer
Coastal flood zones were derived from the FEMA Base
Flood Elevations. Flooding zones shown are intended to
identify potential vulnerabilities and are for city planning purposes only and should not be used at the project
scale. Detailed analysis of flooding at should be
completed for project-level planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Central
Planning
Area
Southern
Planning Area
!.G
STATE PARK RD
COLLEGE COVE PARK
College
Cove
Trinidad
State Beach
to Elk Head
Central Planning Area
FIGURE E.1
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Shoreline Erosion -
Northern Planning Area
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - Data source: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA. Created by: zporteous 12578625_005_VA_SE_DDP
Print date: 14 Jun 2024 - 07:47
EXISTING AFFECTED BEACHES
Sea Level Rise Scenario
0 - 1.6 ft
1.6 - 3.3 ft
3.3 - 6.6 ft
SHORELINE RETREAT
Sea Level Rise Scenario
1.6 ft
3.3 ft
6.6 ft
Mean High Water
ASSETS
Existing trails
DRAFT
Data Disclaimer
Rates of bluff and shoreline erosion were derived from
the USGS Coastal Storm Modeling System (CoSMoS).
These results are intended to identify potential
vulnerabilities and are for city planning purposes only.
Due to the regional nature of the USGS model and
uncertainties surrounding climate change related
impacts and associated with coastal numerical
modeling, these results should not be used for projectlevel planning purposes.
Trinidad
Rancheria
City of
Trinidad Central
Planning
Area
Southern
Planning
Area
Northern
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
MAIN ST
LANFORD RD
EWING
ST
AZALEA
WAY
STAGE
COACH RD
STATE HWY 101
PACIFIC C T
101 OFF RAMP
STATE HWY
SCENIC DR
HIGHWAY 101
UNDER PASS
VAN WYCKE ST
VIEW AVE
PATRICKS
POINT DR
GALINDO ST
VAN WYCKE ST
TRINITY ST
WEST ST PARKER ST
E DWARDS ST
EAST ST
HE
CTO
R ST
OC
EANAVE
LIGHTHOUSE RD
WAGNER ST
PARKER CREEK DR
GROTH LN
STATE HWY 101 ON RAMP
STATE HWY 101 OFF RAMP
UNDERWOOD DR
STATE PARK RD
N WESTHAVEN DR
Wagner
St Tr
Trinidad
Head Tr
Galindo
St Tr
Axel
Lindgren
Mem. Tr
Parker
Cr Tr
Trinidad
State Beach
to Elk Head
Lighthouse
Rd Tr
Public
Restrooms *
Seascape
Restaurant *
Launcher
Beach
Pier *
Trinidad
State
Beach
City of
Trinidad
Boat
Launch *
Old Home
Beach
Northern
Planning Area
Southern
Planning Area
FIGURE E.2
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Shoreline Erosion -
Central Planning Area
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 60 120 180 240 300
Feet
Paper Size ANSI B
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - Data source: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA. Created by: zporteous 12578625_005_VA_SE_DDP
Print date: 14 Jun 2024 - 07:47
EXISTING AFFECTED BEACHES
Sea Level Rise Scenario
0 - 1.6 ft
1.6 - 3.3 ft
3.3 - 6.6 ft
SHORELINE RETREAT
Sea Level Rise Scenario
1.6 ft
3.3 ft
6.6 ft
Mean High Water
ASSETS
G!. Hydrants
Water mains
Existing trails
Stormwater main
Stormwater Appurtenances
Public Parking
DRAFT
Data Disclaimer
Rates of bluff and shoreline erosion were derived from
the USGS Coastal Storm Modeling System (CoSMoS).
These results are intended to identify potential
vulnerabilities and are for city planning purposes only.
Due to the regional nature of the USGS model and
uncertainties surrounding climate change related
impacts and associated with coastal numerical
modeling, these results should not be used for projectlevel planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Southern
Planning
Area
Central
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
PA-PAH
LN
SCENIC DR
CHER-AELN
BAKER RANCH RD
LANFORD RD
STATE HWY 101
MA-WE MORE VIEW LN
Central Planning Area
FIGURE E.3
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Shoreline Erosion -
Southern Planning Area
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
\\10.206.68.4\files\gis2\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - Data source: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA. Created by: zporteous 12578625_005_VA_SE_DDP
Print date: 14 Jun 2024 - 07:47
EXISTING AFFECTED BEACHES
Sea Level Rise Scenario
0 - 1.6 ft
1.6 - 3.3 ft
3.3 - 6.6 ft
SHORELINE RETREAT
Sea Level Rise Scenario
1.6 ft
3.3 ft
6.6 ft
Mean High Water
ASSETS
G!. Hydrants
Water mains
Existing trails
DRAFT
Data Disclaimer
Rates of bluff and shoreline erosion were derived from
the USGS Coastal Storm Modeling System (CoSMoS).
These results are intended to identify potential
vulnerabilities and are for city planning purposes only.
Due to the regional nature of the USGS model and
uncertainties surrounding climate change related
impacts and associated with coastal numerical
modeling, these results should not be used for projectlevel planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Central
Planning
Area
Southern
Planning Area
G
STATE
PARK RD
COLLEGE COVE PARK
College
Cove
Trinidad
State Beach
to Elk Head
Central Planning Area
FIGURE F.1
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Bluff Erosion -
Northern Planning Area
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
Q:\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_006_VA_BE_DDP Data source: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA. Created by: zporteous Print date: 26 Jun 2024 - 10:07
BLUFF EROSION
Sea Level Rise Scenario
1.6 ft
3.3 ft
6.6 ft
CoSMoS Digitally Mapped
Bluff Edge
Field Mapped Bluff Top
(SHN 2022)
ASSETS
Existing trails
DRAFT
Data Disclaimer
Rates of bluff and shoreline erosion were derived from
the USGS Coastal Storm Modeling System (CoSMoS).
These results are intended to identify potential
vulnerabilities and are for city planning purposes only.
Due to the regional nature of the USGS model and
uncertainties surrounding climate change related
impacts and associated with coastal numerical
modeling, these results should not be used for projectlevel planning purposes.
Trinidad
Rancheria
City of
Trinidad
Central
Planning Area
Southern
Planning
Area
Northern
Planning
Area
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
G!.
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
MAIN ST
LANFORD RD
EWI
NG
ST
AZALEA
WAY
STAGE
COACH RD
STATE HWY 101
PACIFIC C T
101 OFF RAMP
STATE HWY
SCENIC DR
HIGHWAY 101
UNDER PASS
VAN WYCKE ST
VIEW AVE
PATRICKS
POINT DR
GALINDO ST
VAN WYCKE ST
TRINITY ST
WEST ST
PARKER ST
EDWARDS ST
EAST ST
HE
C
T
OR ST
OC
EANAVE
LIGHTHOUSE RD
WAGNER ST
PARKER CREEK DR
GROTH LN
BAY ST
STATE HWY 101 ON RAMP
STATE HWY 101 OFF RAMP
UNDERWOOD DR
STATE PARK RD
N WESTHAVEN DR
Wagner
St Tr
Trinidad
Head Tr
Galindo St Tr
Axel
Lindgren
Mem. Tr
Parker Cr Tr
Trinidad State Beach
to Elk Head
Lighthouse Rd Tr
ROCK
TERRACE
WAGNER SEGMENT
SCENIC SEGMENT
EDWARDS SEGMENT
Public
Restrooms *
Seascape
Restaurant *
Launcher
Beach
Pier *
Trinidad
State
Beach
City of Trinidad
Boat
Launch *
Old Home
Beach
Northern
Planning Area
Southern
Planning Area
FIGURE F.2
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Bluff Erosion -
Central Planning Area
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 60 120 180 240 300
Feet
Paper Size ANSI B
Q:\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_006_VA_BE_DDP Data source: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA. Created by: zporteous Print date: 26 Jun 2024 - 10:07
BLUFF EROSION
Sea Level Rise Scenario
1.6 ft
3.3 ft
6.6 ft
CoSMoS Digitally Mapped
Bluff Edge
Active Slides
& Earthflow (SHN 2019)
Field Mapped Bluff Top
(SHN 2022)
Geologic Areas (SHN
2019)
ASSETS
G!. Hydrants
Water mains
Existing trails
Stormwater main
Stormwater Appurtenances
Public Parking
DRAFT
Data Disclaimer
Rates of bluff and shoreline erosion were derived from
the USGS Coastal Storm Modeling System (CoSMoS).
These results are intended to identify potential
vulnerabilities and are for city planning purposes only.
Due to the regional nature of the USGS model and
uncertainties surrounding climate change related
impacts and associated with coastal numerical
modeling, these results should not be used for projectlevel planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Southern
Planning
Area
Central Planning Area
G!.
G!.
G!.
G!.
G!.
G!.
PA-PAH
LN
SCENIC DR
CHER-AELN
BAKER RANCH RD
LANFORD RD
STATE HWY 101
MA-WE MORE VIEW LN
SCENIC SEGMENT
Central Planning Area
FIGURE F.3
Date 06/29/2023
Revision No. -
Project No. 12578625
Vulnerability Analysis:
Bluff Erosion -
Southern Planning Area
Trinidad Community Coastal
Resilience Planning Project
City of Trinidad
Grid: NAD 1983 StatePlane California I FIPS 0401 Feet
Map Projection: Lambert Conformal Conic
Horizontal Datum: North American 1983 o
0 50 100 150 200 250
Feet
Paper Size ANSI B
Q:\GIS\PROJECTS\12578000s\12578625\GIS\Maps\Deliverables\12578625_BFE_SEBE_VI_DDP\12578625_CAP_DDP.aprx - 12578625_006_VA_BE_DDP Data source: Google Maps Sat: © OpenStreetMap (and) contributors, CC-BY-SA. Created by: zporteous Print date: 26 Jun 2024 - 10:07
BLUFF EROSION
Sea Level Rise Scenario
1.6 ft
3.3 ft
6.6 ft
CoSMoS Digitally Mapped
Bluff Edge
Active Slides
Field Mapped Bluff Top
(SHN 2022)
ASSETS
G!. Hydrants
Water mains
Existing trails
DRAFT
Data Disclaimer
Rates of bluff and shoreline erosion were derived from
the USGS Coastal Storm Modeling System (CoSMoS).
These results are intended to identify potential
vulnerabilities and are for city planning purposes only.
Due to the regional nature of the USGS model and
uncertainties surrounding climate change related
impacts and associated with coastal numerical
modeling, these results should not be used for projectlevel planning purposes.
Trinidad
Rancheria
City of
Trinidad
Northern
Planning
Area
Central
Planning Area
Southern
Planning Area
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 11 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document.
Appendix C
Conceptual Layout of Project Opportunity
Areas and Example Projects
Trinidad, California
TRINIDAD COMMUNITY COASTAL RESILIENCE PLANNING PROJECT 718 3rd St.
Eureka, CA 95501 USA
T 1 707 443 8326
GHD Inc.
Client: CITY OF TRINIDAD
www.ghd.com
NORTH
0 150 feet
1" = 75'
CONCEPT PLAN 75 225 300
PARKING / PARKLETS / OUTDOOR SEATING
STORMWATER RAIN GARDEN
PLANTING AREAS
SCENIC OVERLOOK LANDSCAPING,
INTERPRETIVE SIGNAGE
STORMWATER IMPROVEMENTS
SOLDIER PILE RETAINING WALL
LEGEND
ONE WAY ROAD (RELOCATE UNDERGROUND UTILITIES)
TWO WAY ROAD
PEDESTRIAN TRAIL / ACCESS IMPROVEMENTS
SIDEWALK
ALTERNATIVE TRAIL ALIGNMENT
TRAIL IMPROVEMENTS
(DRAINAGE / EROSION CONTROL / VEGETATION)
EDWARDS ST.
PARKER ST.
WEST ST.
UNDERWOOD DR.
VAN WYCKE ST.
Launcher
Beach
Old Home
Beach
GALINDO ST.
EWING ST.
HECTOR ST.
TRINITY ST.OCEAN AVE.
DETAIL PLAN 1 DETAIL PLAN 2
DETAIL PLAN 3
Retaining wall with railing
Stormwater Underdrains
and Piping
Stormwater Underdrains
and Piping
Relocated utilities
as needed
Relocated utilities
as needed
SIDEWALK PLANTING
RETAINING WALL
& PLANTING
ALTERNATIVE
TRAIL / SIDEWALK
ROAD
(TWO-WAY)
ROAD
(ONE-WAY)
PEDESTRIAN
TRAIL
PEDESTRIAN
TRAIL
Pedestrian / bike trail
Pedestrian / bike trail
Parking
Wood seats
Wood seats
Street planting
Street planting
Existing vegetation
Existing vegetation
Section A
Section B
EDWARDS ST.
EDWARDS ST.
HECTOR ST.
VAN WYCKE ST.
Trinidad, California
TRINIDAD COMMUNITY COASTAL RESILIENCE PLANNING PROJECT 718 3rd St.
Eureka, CA 95501 USA
T 1 707 443 8326
GHD Inc.
Client: CITY OF TRINIDAD
www.ghd.com
Section C
Parking
Parking
Parklet
Parklet
Parking
Street planting Street planting
Street planting
Parklet / Outdoor Dining
Parklet / Outdoor Seating
SIDEWALK ROAD PARKING
(ONE-WAY)
OUTDOOR DINING
/ PARKLET
SIDEWALK
Wood seats
TRINITY ST.
EDWARDS ST.
Trinidad, California
TRINIDAD COMMUNITY COASTAL RESILIENCE PLANNING PROJECT 718 3rd St.
Eureka, CA 95501 USA
T 1 707 443 8326
GHD Inc.
Client: CITY OF TRINIDAD
www.ghd.com
CHARACTER
Coastal landscape
Rustic materials
Outdoor dining space Outdoor seating at parklets
GHD | City of Trinidad | 12578625 | Community Coastal Resilience Plan 13 This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. ghd.com The Power of Commitment