Seattle DCI will post the updated advisory map for steep slope environmentally critical areas on October 24, 2016. The updated map will replace the steep slope layer shown on our GIS application.
A “steep slope” is a slope with an incline of 40 percent or more (10 feet of vertical rise over a horizontal distance of 25 feet or less) with a height of at least 10 feet. We have specific regulations for sites with steep slopes and their buffers to help prevent landslides and erosion.
Technical advancements have allowed us to update our steep slope map so that it is more accurate. We have not changed the definition of a steep slope, though some properties may have a different steep slope designation on the updated map.
The steep slope area map is an advisory map because Seattle DCI uses it for initial information prior to your permit application. This new map layer allows the property owner to be better informed before designing their project. Staff determine whether a site contains a steep slope area based on site visits to the property and topographic surveys.
For more information, please see Director’s Rule 10-2016 or contact: