Displays areas with Riparian Corridors in the City of Seattle. See Ordinance Number: 122738.

A polygon feature class showing Riparian Corridors in Seattle. Used to implement and regulate the City of Seattle's Environmentally Critical Areas (ECA) policies.  

The riparian corridor includes the riparian watercourse and the riparian management area. The riparian watercourse is the watercourse of Type F, Np, and Ns waters defined in WAC 222-16-030 and 222-16-031 that have fish or wildlife habitat. The riparian management area is the area within 100 feet of the riparian watercourse measured horizontally landward from the ordinary high water mark of the watercourse as surveyed in the field, or from the top of the bank if the ordinary high water mark cannot be determined. 

For more information about the definition of riparian corridors, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas (ECA) definitions. 

Updated as needed.

Displays areas of landslide events based on a Seattle Landslide Study completed by Shannon and Wilson.

A polygon feature class showing landslide event inventory. Used to implement and regulate the City of Seattle's Environmentally Critical Areas (ECA) policies. This layer includes a more comprehensive collection of slide events maintained by Shannon and Wilson via the Seattle Landslide Study which included slide data through June 1999.

The Known Slide layer was most recently updated under SDCI Director's Rule 12-2019.

For more information about the definition of known slide areas, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas (ECA) definitions.

Updated as needed.

Displays areas with liquefaction zones.

A polygon feature class that shows liquefaction zones. Used to implement and regulate the City of Seattle's Environmentally Critical Areas (ECA) policies. This layer was created in 1995 using data obtained from the USGS. Some edits were made to the edges to better coincide with the City's two foot contour data.

Areas of the City subject to ground shaking from seismic hazards that are addressed by Title 22.

The Seattle Fault zone as delineated in Troost et al., 2005, The geologic map of Seattle, a progress report, U.S. Geological Survey, Open-file report 2005-1252 , or as the Director determines is more accurately mapped by the U.S. Geological Survey, as set out in a Director's Rule.

For more information about the definition of liquefaction zones, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas (ECA) definitions. 

Updated as needed.

FEMA flood prone areas with 100 foot buffer. Original flood prone areas where table digitized into the City of Seattle GIS CGDB control layer in the mid 90's. Layer may be used without the buffer by unselecting the flood = 1 feature type.

This layer is used by the City as an aid to evaluate construction sites for the presence of flood prone areas pertinent to Environmentally Critical Areas (ECA)  regulations.

Areas that would likely be covered with or carry water as a result of a one hundred (100) year flood event, or that would have a one percent (1%) or greater chance of being covered with or of carrying water in any given year based on current circumstances or maximum development permitted under existing zoning.

For more information about the definition of flood prone areas, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas (ECA) definitions. 

Updated as needed.

Displays areas with 40% steep slope or greater in the City of Seattle.

A polygon feature class showing areas with an incline of 40% or more (10 feet of vertical rise over a horizontal distance of 25 feet or less) with a height of at least 10 feet. 

This layer was produced using a combination of 2001 LIDAR contours (Puget Sound LIDAR Consortium) and the 1993 topographic contours from aerial photos. The Steep Slope layer was most recently updated under SDCI Director's Rule 12-2019.

 

The steep slope area map is called “advisory” because the mapping is used by the Seattle Department of Construction and Inspections for initial information and screening. Whether or not a site is eventually treated as an environmentally critical area is based on the actual topography of the ground surface.

 

For more information about the definition of steep slope erosion hazard areas, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas (ECA) definitions. 

Because of the size of this dataset, we do not recommend trying to download it. Please use as a service. If you need a particular area extracted, please use this form to make a request:

Displays areas with Wildlife Corridors in the City of Seattle. See Ordinance Number: 122738.

A polygon feature class showing Wildlife Areas in the City of Seattle. Used to implement and regulate the City of Seattle's Environmentally Critical Areas (ECA) policies.

Corridors that connect priority habitats and species areas or habitat areas for wildlife species of local importance that meet criteria established by the Washington State Department of Fish and Wildlife.

For more information about the definition of wildlife habitat, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas definitions. 

Updated as needed.

Displays historic landfill locations.

A polygon feature class showing landfill areas and former landfill sites. Used to implement and regulate the City of Seattle's Environmentally Critical Areas (ECA) policies. This layer was table digitized in 1996 using abandoned landfill information from King County Department of Public Health.  For those abandoned landfills emitting methane, a 1,000 foot buffer was created and so indicated in the attribute table.

For more information about the definition of landfill areas, see Seattle Municipal Code section 25.09.012, Environmentally Critical Areas (ECA) definitions. 

Updated as needed.