Landslide prone areas are areas that are prone to landslides as identified through a variety of means, including the Seattle Landslide Study, documentation of past landslides, topological surveys, and site-specific geological reports. Landslide-prone areas are specifically defined in Seattle Municipal code section 25.09.020 A. Steep slopes are landslide prone areas located outside of Downtown and Highrise zones with an incline of forty (40) percent or more. Steep slopes are subject to additional standards to prevent harm to the environment from erosion (see above).
Development in landslide-prone areas is limited primarily to prevent construction impacts and facilitate complete site stabilization after construction.
- Seattle Municipal Code 25.09 Regulations for Environmentally Critical Areas
- CAM 103B, Environmentally Critical Area Site Plan Requirements
- CAM 324, Reducing Landslide and Stormwater Erosion Damage: What You Can Do
- CAM 327A, Environmentally Critical Areas Exemptions, Relief from Prohibition on Steep Slope Development, and Modifications to Submittal Requirements — Application Instructions and Submittal Requirements
- CAM 327B, Environmentally Critical Areas — Small Project Waivers Application Instructions and Submittal Requirements
- CAM 328, ECA Exceptions
- CAM 331, Environmentally Critical Areas: Trees and Vegetation
- CAM 331A, Environmentally Critical Areas: Vegetation Restoration
- CAM 331B, Hazard Trees
Related Director's Rules
- DR 3-2002, Requirements for Allowing Grading in Environmentally Critical Areas Between October 31st and April 1st (Dry Season Extension Letter).
- DR 3-93, General Duties and Responsibilities of Geotechnical Engineers
For additional information on landslide hazards, go to DPD Emergency Management Landslide Page.