Determine if the project is located within a floodplain
Use our internal GIS Workbench and the Federal Emergency Management Agency’s (FEMA) Map Service Center website and National Flood Hazard Layer viewer web application to determine whether the project is within a regulatory floodway or Special Flood Hazard Area (SFHA).
If the digital data is not available, or if the FEMA SFHA Zone boundary does not align with the surveyed creek/river location, contact our Headquarters Hydraulics Office for further assistance.
Maps may only show the 100-year floodplain; you may need to coordinate directly with the local government for specific information on the special flood hazard area and codes.
Determine the local agency requirements & permit needs
Check the floodplain and critical area ordinances and the website of the city or county where the work is occurring for more information on the local agency’s requirements, including when and how to get a Floodplain Development Permit.
Fish passage projects that qualify for the Fish Habitat Enhancement Program Hydraulic Project Approval may need to get a Floodplain Development Permit.
Environmental staff, work closely with the Hydraulic Engineer to determine if the proposed project may increase the water surface elevations above local agency code requirements.
Coordinate with local agencies
Coordinate with local agencies for all WSDOT projects early in preliminary design to confirm local jurisdiction floodplain management requirements determined during scoping are correct. For more guidance on reaching out to local agencies, refer to WSDOT’s Outreach to Local Governments on Flood Risk Assessment for WSDOT Fish Passage Projects (Exhibit 432-3 in Environmental Manual Chapter 432: Special Flood Hazard Area (PDF 803KB)).
Document impacts
For Design-build projects, the Design-Builder will conduct the rise analysis and will prepare and submit all required documents to the local agencies and FEMA.
Send the following documents based on the changes to water surface elevations:
- No rise (Zone AE) or no rise above one foot (Zone A) - Send a copy of the no-rise analysis to the local agency for review and approval of the no-rise certification. For Zone A, local agencies may have no rise thresholds less than one foot.
- Reduction (Zone AE or A) or change in extent (Zone A) -No additional documentation required during design. Share the analysis with the local agency.
- Rise (zone AE) or rise above one foot (Zone A) - Work with Hydraulics to submit a Conditional Letter of Map Revision (CLOMR) application to FEMA through the local agency. You must obtain the CLOMR before you apply for a Floodplain Development Permit.
Continue to work closely with the Hydraulics Engineer and local agencies as the design is finalized.
Apply for a Floodplain Permit in accordance with the local agency’s requirements.
