Agenda Item9
1 DATE: May 5, 2025
TO: Honorable Mayor and Members of the City Council through City Manager FROM: Gina Benedetti-Petnic, PE – Assistant Director, Public Works Department Patrick Carter, Assistant to the City Manager
Paul Kaushal, PE – Director, Public Works Department
SUBJECT: Resolution Accepting Completion of the Sea Level Rise Mapping and Modeling for Climate Adaptation Project (17-MITPPS-21019)
RECOMMENDATION
It is recommended that the City Council adopt a Resolution Accepting Completion of the Sea Level Rise Mapping and Modeling for Climate Adaptation Project (17-MITPPS-21019).
BACKGROUND
Located along the Petaluma River, the city experiences the tidal flows that come from the Pacific Ocean via San Francisco Bay and San Pablo Bay. As the climate continues to change, the sea level is expected to rise. To manage our floodplain and update our land use policies responsibly, it is imperative that we understand the potential cumulative effects of storm related floods, king tides, and sea level rise.
The Sea Level Rise Mapping and Modeling for Climate Adaptation project was initiated to develop unique comprehensive mapping that includes both traditional storm flood maps with sea level rise (SLR) maps to provide a holistic understanding of flood potential now and into the future. The project generated Maps Showing Combined Flooding with SLR that might occur as a result of future sea level rise and that reflect updated knowledge about areas where the city may experience flooding.
A key outcome and primary objective of this project is its support for the City’s General Plan Update. In April 2024, the Draft Flood Resiliency Policy Framework, a key element in the General Plan, was released for public review. This framework incorporates the project’s mapping results, and outlines goals and policies to protect existing infrastructure, guide future development in and near the floodplain, and strengthen the City’s long-term resilience to climate impacts. 2 Funding for this project was primarily provided through a Community Development Block Grant– Mitigation Planning & Public Services (CDBG MIT-PPS) from the U.S. Department of Housing and Urban Development (HUD), under which the City of Petaluma is a subrecipient. The grant agreement was executed on October 3, 2022, and specifically supported the City’s first phase of the Sea Level Rise Mapping and Modeling for Climate Adaptation project.
DISCUSSION
This project was initiated in consideration of the findings from the preliminary sea level rise vulnerability assessment included in the City of Petaluma Local Hazard Mitigation Plan, November 2020 (LHMP) and the following mitigation actions identified in that plan:
•Map and assess vulnerability to sea level rise and integrate the information with the City GIS mapping capabilities to educate the community and help them gain awareness of the potential impacts and actions the City is taking to plan and adapt •Assess sea level rise modelling for use in the LHMP and how those projections can be routinely re-evaluated in subsequent climate adaptation planning efforts •Update City Implementing Zoning Ordinance (IZO) to manage development in high-risk areas
Geographic Information System (GIS) is a computer system that analyzes and displays geographically referenced information. It is an effective tool that can identify where climate- change related effects are likely to occur now and in the future. Mapping and overlaying climate information, such as projected sea level rise projections with critical facilities, parcel, infrastructure, and building footprints can help communities understand the expected extent of sea level rise, and where flooding, wildfires, and other natural hazards are more likely to occur based on climate change.
The sea level rise mapping and modeling from this project has been instrumental in informing the draft Petaluma General Plan Update policies and will be a valuable resource to provide guidance for the upcoming zoning ordinance revisions for development standards in and near the floodplain, as well as other planning studies moving forward.
This project, coordinating sea level rise projections within the context of the City's updated 2D Flood modeling (and FEMA Flood Insurance Rate Maps), will ultimately guide routine review of project applications for new development to ensure new development proposals incorporate adequate protections and adaptation measures. The meaningful use of these maps from this project can be seen in the Flood Resiliency Framework draft policies, which are intended to guide both future development and the management of existing infrastructure. 3 It should also be noted that this project is building capacity by developing knowledge of what parcels will be affected by sea level rise and what actions will be needed for climate adaptation.
The new GIS maps will be a critical tool in the upcoming Vulnerability Assessment and Flood Adaptation Master Plan, helping to identify appropriate infrastructure and nature-based adaptation projects. Identifying parcels expected to be affected by sea level rise may create new, future funding opportunities with other organizations whose mission includes assisting vulnerable communities and providing the capital or design assistance needed for adaptation.
Identifying sea level rise-affected parcels is the first step in mitigating future flood hazards.
Knowing what areas will be affected and to what degree will allow the City and affected property owners to plan and take action to protect property and infrastructure, reducing risk and increasing resilience.
4 The grant-funded portion of this project was completed in April 2025, with no outstanding issues or claims. Acceptance of the completed work is required for grant closeout under the terms of the CDBG MIT-PPS program.
PUBLIC OUTREACH
The Petaluma Sea Level Rise and Flood Mapping Community Meeting was held on Wednesday, September 27, 2023, at the Lucchesi Community Center. This meeting included a presentation of modeling and maps of projected flooding and sea level rise, followed by a question-and-answer session.
Additionally, a Flood and Sea Level Rise Mapping Update Workshop with City Council was conducted at the publicly noticed meeting of January 8, 2024 at City Hall. The workshop included an extensive presentation from staff and consultants followed by a question-and-answer session.
As part of the next phase of this project (not funded under this CDBG grant), more community meetings will be held in 2025 (and 2026 as needed) to review detailed mapping updates with several creek and river-adjacent neighborhood residents and stakeholders.
COUNCIL GOAL ALIGNMENT
The Floodplain and Sea Level Rise Modeling and Mapping Project directly supports the Petaluma City Council’s goals related to environmental stewardship, community resiliency, and climate adaptation. By proactively modeling future floodplain scenarios and sea level rise impacts, this project enhances the City’s ability to make informed decisions about land use, infrastructure investments, and emergency preparedness. This work aligns with the Council’s commitment to climate action and hazard mitigation, particularly through data-driven approaches that reduce risk to life, property, and public assets.
The project supports the Council’s priority of equity and community safety by facilitating the identification of vulnerable neighborhoods and planning for adaptive strategies that protect historically underserved or flood-prone communities as well as critical city infrastructure.
CLIMATE ACTION/SUSTAINABILITY EFFORTS
The project has laid the foundation for integrating resilience planning into development review processes, capital improvement planning, and environmental justice efforts. Ultimately, this project strengthens Petaluma’s ability to meet state and federal floodplain management standards while also advancing long-term sustainability and climate resilience objectives set forth in the City of Petaluma Blueprint for Climate Action (2024). The Blueprint for Climate Action specifically underscores the need for accurate sea level rise projections to create frameworks for natural open space management in riparian areas (OSM-4, section a).
5 ENVIRONMENTAL REVIEW
This project involved professional consulting services to model sea level rise projections with updated storm flood models and create combined maps for multiple scenarios, as well as supporting community outreach initiatives. As it included no construction or physical improvements, it does not constitute a “project” under CEQA (CEQA Guidelines §15378(b)(5)).
In addition, planning and feasibility studies for potential future actions are exempt under CEQA Guidelines §15262. Therefore, no environmental review was required.
FINANCIAL IMPACTS
The Sea Level Rise Mapping and Modeling for Climate Adaptation Project (E11502028, Phase 54115) was primarily funded through a $192,500 Community Development Block Grant–Disaster Recovery (CDBG-DR) from the U.S. Department of Housing and Urban Development, administered by the California Department of Housing and Community Development.
There is some impact to the City’s General Fund to contribute a portion of the administration costs, and sufficient funds are available to cover all project costs.
CDBG Grant Budget
PLANNING LEVEL
ESTIMATE
TOTAL
TASK DESCRIPTION
1 Modeling of impacts of Sea Level Rise $ 64,000.00 2 Mapping and assess vulnerability to Sea
Level Rise High Risk Areas $ 83,000.00 3 Integrate with City GIS mapping platform $ 18,000.00 4 Public Outreach and education, development
of action plan $ 10,000.00 5 Administration costs $ 17,500.00 Total $ 192,500.00
SLR Flood Modeling and Mapping Costs
West Consultants SLR Scope $ 95,834.10 *PSA with 2 amendments Sherwood Design Engineers $ 89,443.75 *PSA with 2 amendments Subtotal - Consultant Costs $ 185,277.85
Admin Costs $ 7,222.15
Total Project Grant Costs $ 192,500.00
*West Consultants Inc. and Sherwood Design Engineers were retained as subconsultants through the prime consultant, Raimi & Associates Inc.
6 ALTERNATIVES
The consultants have satisfactorily completed the project, and adoption of a resolution accepting completion is necessary to meet the grantor’s closeout requirements. Failure to adopt the resolution could put the City at risk of noncompliance with the grant conditions and may jeopardize full reimbursement.
ATTACHMENTS
1. Resolution