Todd Creek Flood Study

Flood studies affect property owners in several ways:  land value, development, and insurance.  While not quantified, two comparable properties one being in a floodplain and one not, the one property outside the floodplain will have greater value.  Regulations exist for properties in the floodplain and floodway that do not apply outside these zones. Flood regulations affect whether one can develop in the floodway and add cost for development in the floodplain.  The National Flood Insurance Program requires flood insurance for those properties that are within a floodplain and that are backed by a federally backed mortgage institution.  For these reasons alone, it is critical that FEMA’s flood maps are accurate and reliable.  Towards this end, the County pursued a local flood study to have flood maps that are as accurate and reliable as possible. Similar efforts have been done in local cities such as Petaluma and City of Santa Rosa.

Todd Creek Flood Insurance Study Timeline

• April 20, 2026, letter of final determination issued by FEMA recognizes the 90-day appeal period (October 16, 2025 to January 14, 2026) had lapsed with no public comment and that the flood maps, which became effective on the February 13, 2026, remain valid.
• February 13, 2026, FEMA accepted the County’s Letter of Map Revision, aka the County’s revised flood study, and the revised Flood Insurance Rate Maps became effective.
• October 2025, FEMA published notice of map change & commenced the 90-day appeal period on October 16, 2025.
• July 2025, county mailed out public notices for upcoming map change.
• June 2025, FEMA completed technical review process & started 90-day deadline for county to send public notices.
• June 30, 2023, the county submitted the Letter of Map Revision flood insurance study to FEMA for review.
• January 2023, Permit Sonoma hired a consulting firm, R&F Engineering, to conduct a revised flood study for the Todd Creek watershed.
• FEMA rejected the County’s 2021 appeal and proceeded with the combined flood study, which was effective from July 19, 2022 – February 12, 2026.
• In 2020 FEMA conducted a second flood study for the second half of the watershed.  Each study was conducted independently, used a different methodology, and was joined together.  The County appealed a second time but missed the appeal deadline. 
• In 2015, FEMA produced a flood insurance study for the Todd Creek watershed.  This study was incomplete and only studied half of the watershed.  The County successfully appealed the study, forcing FEMA to re-study. 

Demonstrating their commitment to shifting decision-making to local authorities, the County has pursued a request (called a Letter of Map Revision) to have the FEMA flood study and flood maps revised.  The technical support for this request is a revised flood insurance study produced and funded by the County.  The County hired an engineering consulting firm to review the FEMA 2015 and 2020 flood studies.  The engineering consulting firm found several key anomalies leading County staff to believe that a new flood study conducted on the entire watershed under one methodology will result in a more accurate flood study.  The County then funded the local flood study and went out to bid. 

FEMA approved the Letter of Map Revision on February 13, 2026, and held a 90-day appeal as required by the Code of Federal Regulation.  After the 90-day appeal period had elapsed, FEMA issued the County a final letter of determination on April 20, 2026.

Results

The 950-or-so notifications summarize the flood zone designation for each parcel.  There are a range of scenarios.   In 675 cases, there is no change to the existing flood zone designation.  The existing flood zone designation could be no flood, floodplain, or floodway, depending on FEMA’s flood study.

There are 289 parcels that are seeing a change, with over half of the parcels seeing the floodplain designation removed (n = 164), and there is no other flood zone on these parcels.  

FEMA has approved the County’s flood study and flood insurance rate maps.  No further action is  hgvp9needed by the County.

Homeowners may need to submit a FIRMette to their insurance company to have the flood insurance requirement removed.  If assistance is needed, please reach out to Permit Sonoma.

Any homeowners negatively impacted by the County’s study & added to the new flood insurance rate maps can reach out to the below contacts for assistance preparing the documents for a Letter of Map Amendment application to FEMA to remove their structure(s) from the flood hazard area if applicable.

Steve Snow, Floodplain Manager

Nathan Quarles, Deputy Director

Preliminary Federal Emergency Management Agency (FEMA) Digital Flood Insurance Rate Map (DFIRM)

Impact Summary

• • Letter of Final Determination, FEMA April 20, 2026
  • Effective LOMR with Flood Insurance Rate Maps, FEMA February 13, 2026
  • GIS-Based Study Mapping Tool:  The County has produced an Interactive Map so the public can review the changes within the Todd Creek Watershed.  The mapping tool has a slide feature to easily see the differences between the two studies.  Viewers can also type in their parcel number or address to view their parcel, or viewers can zoom in or out to review the flood maps.
  • Todd Creek LOMR Summary Report
  • Regulation References: These regulations apply FEMA approved Flood Insurance Rate Maps and Letter of Map Changes, once approved.
    • Floodway (F1):
      Land area added to the floodway is subject to the County’s prohibition on new development within designated floodways.  The County does allow repair and/or rebuilds due to natural catastrophes or other unforeseen events, such as earthquakes, fires, damage from trees, etc. within the floodway.
      
    • Floodplain (F2):
      Land area added to the floodplain is subject to the County’s floodplain regulations, namely all future development will need to be protected to minimize the impact from flooding.  These measures range from elevating the structure above the BFE and/or flood proofing the structure and utilities.