Floodplain Development Regulations Update - What & Why
What’s Happening Now?
SDCI completed proposed permanent Floodplain Development Regulations and published the Threshold Determination on August 1, 2024 and on August 21, 2025 published an Addendum to this SEPA Threshold Determination in our Land Use and Information Bulletin under Other Land Use Notices. The intent of the Addendum is to update tables and maps to clarify the impacts of the proposal and to explain the changes to the proposed permanent Floodplain Development Regulations that are part of the final proposed Permanent Floodplain Development Regulations. The Addendum to the SEPA Threshold Determination documents including the updated proposed permanent Floodplain Development Regulations and updated Director’s Report are on the Project Documents page.
This Addendum to the SEPA Threshold Determination analyzes the changes made to the proposed permanent Floodplain Development Regulations and clarifies the tables and maps that were included in the August 1, 2024 SEPA Threshold Determination.
Project Benefits
Our floodplain development regulations protect people, property, and the environment by regulating the development that occurs in the mapped floodplain and flood prone areas. The new permanent regulations will adopt FEMA’s 2020 new Flood Insurance Rate Maps and Flood Insurance Study and will continue to regulate flood prone areas mapped by Seattle Public Utilities. Below are examples of development regulations and these regulations vary depending on the specific flood zone designations, characteristics of the property, and the nature of the development.
- The elevation that the first floor of a new structure must be built at to keep the first story above anticipated flood levels
- Structures must be engineered to withstand wind from anticipated storms
- Structures must be engineered to withstand flood waters should anticipated flood levels be exceeded
The End Result
The permanent Floodplain Development Regulations will meet FEMA's 2020 requirements.