Use this information to analyze how work within floodplains may impact things like flows, water storage, and biologic functions in the area to comply with federal, state, and local agency requirements.

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.

If the local agency says your work within a mapped SFHA does not need a permit, contact the ESO Permitting & Compliance Manager.

166,800 electric vehicle

registrations in Washington in 2023, up from 114,600 in 2022.

87 wetland compensation sites

actively monitored on 918 acres in 2023.

25,000 safe animal crossings

in the Snoqualmie Pass East Project area since 2014.