Floodplain Development Regulations Update - What & Why

What’s Happening Now?

SDCI has completed proposed permanent Floodplain Development Regulations and published the Threshold Determination on July 8 in SDCI's Land Use and Information Bulletin under the Other Land Use Notices section (see page 12). The intent of this declaration is to satisfy the requirement of the State Environmental Policy Act (SEPA; RCW 43.21C), including the requirement to inform the public of agency decisions pursuant to SEPA. The SEPA documents including the attachments for the proposed permanent Floodplain Development Regulations and Director's Report are included on the Project Documents page.

This SEPA decision analyzes the full range of regulatory changes that were part of the interim Floodplain Development Regulations adopted on July 19, 2020, as Ordinance 126113 and the additional regulatory changes proposed for the permanent Floodplain Development Regulations. The additional changes include SDCI's proposal to increase the elevation for construction to 3-ft above base flood elevation to account for sea level rise and new sections that include standards for the storage of materials and equipment, and standards for accessory structures.

Additionally, we hosted a public meeting on April 27, 5:00 - 6:00 p.m. See the Get Involved page for a recording of this meeting. 

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 2019 new Flood Insurance Rate Maps and Flood Insurance Study and will continue to regulate flood prone areas mapped by Seattle Public Utilities. Development regulations vary depending on the specific flood zone designations, characteristics of the property, and the nature of the development including first floor elevation. Below is a list of development regulations:

  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 2019 requirements.