Introduction of Landslide Activities in Washington
We are currently in the middle of a statewide landslide hazard zonation mapping project, wherein all state and privately owned timber lands are inventoried (mapped) for landslides and areas of landslide hazard, using an established mapping protocol and resolution. These maps are made available to the public for free via web download. The data is compiled into two GIS databases (landslide inventory and landslide hazard zones) that are also made freely available to the public via web download. In order to create a landslide data repository for the state, these data were compiled with landslide inventories and landform maps that were created by other sources, in some cases for other purposes. It is not known if the local government entities that issue development permits are using these data, but have been encouraged to do so, as many of them have critical areas ordinances requiring geotechnical input for developing on unstable or potentially unstable ground.
The state has requirements to avoid harvesting timber on unstable slopes if doing so would increase the likelihood of failure and delivery of debris to public resources or would threaten public safety. As such, these maps are used by land managers, regulators, and the geotechnical community in developing acceptable harvest plans. The utility of this mapping project was identified during a set of negotiations that led to new unstable slopes rules.
There is a new project starting in the Division of Geology and Earth Resources to map landslides along the Puget Sound coastal bluffs as well as provide hazard maps. This information will be primarily used by county planners for critical areas ordinance and growth management. We are also starting a new project mapping landslides along tsunami evacuation routes to determine what hazard they present to the evacuation areas and to determine whether the evacuation route needs to be changed.
Inventory Status for Washington
Washington has an inventory for both landslides and landforms. We keep these data in a GIS-based database (ArcGIS-SDE-Oracle). The Division of Geology and Earth Resources has a prototype database for tracking losses and other information. Our databases are stored in an ArcGIS format and are accessible via web download and ArcIMS. The Washington State Department of Transportation maintains a separate database for landslides occurring along transportation infrastructure.
Washington State Department of Natural Resources
1111 Washington St SE
PO BOX 47012
Olympia, WA 98504-7012
Individuals responsible for landslide hazards and contact information:
Isabelle Sarikhan - Division of Geology and Earth Resources (for landslides on non-forest lands)
Other state agencies who collect landslide information:
Washington State Department of Transportation
Washington State Department of Ecology