Floodplain Development Regulations Update - What & Why

Floodplain Development Regulations

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.

  1. The elevation that the first floor of a new structure must be built at to keep the first story above anticipated flood levels
  2. Structures must be engineered to withstand wind from anticipated storms
  3. 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.

Construction and Inspections

Kye Lee, Interim Director
Address: 700 5th Ave, Suite 2000, Seattle, WA, 98104
Mailing Address: P.O. Box 34019, Seattle, WA, 98124-4019
Phone: (206) 684-8600
Phone Alt: Violation Complaint Line: (206) 615-0808
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SDCI issues land use, construction, and trade permits, conducts construction and housing-related inspections, ensures compliance with our codes, and regulates rental rules. SDCI is committed to an antiracist workplace and to addressing racism through our work in the community.