Steep slope areas generally include slopes located outside of Downtown and Highrise zones with an incline of 40% or more.Steep slopes are specifically defined in the ECA regulations in section 25.09.020. A.3.b.(5).
Steep slopes pose an environmental risk from erosion which can inundate downhill creeks, reducing water quality, scouring the channel, and removing habitat, in addition to posing hazards to life and property that are regulated separately through land-slide prone regulations.
Development in steep slope areas is prohibited, except in limited circumstances, to ensure the long term stability of these areas and minimize damage from erosion. Steep slopes are also subject to tree and vegetation requirements to reduce erosion and stabilize slopes. Permit applications in or near steep slope areas frequently require additional geotechnical information to address these conditions and may be conditioned to ensure site stability and erosion control.
- 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 329, ECA Administrative Conditional Use Permit—Application Instructions and Submittal Requirements
- CAM 330, ECA—Yard & Setback, Steep Slope and Wetland Buffer Variances
- CAM 331, Environmentally Critical Areas: Trees and Vegetation
- CAM 331A, Environmentally Critical Areas: Vegetation Restoration
- CAM 331B, Hazard Trees
For additional information on landslide hazards, go to DPD Emergency Management Landslide page.