This small landslide blocked a main road (Pacific Way) west of the Cowlitz County town of Kelso last January. Even small landslides like this one can block roads and damage houses. Photo: DNR
Washington is landslide territory. Every winter, landslides across Western Washington block roads, damage homes and infrastructure. They can even cause injuries and fatalities. DNR geologists collect data about these landslides, documenting the location, damage and site conditions including landslide process, slope gradient, land use, specific time of occurrence, and other critical data. These data, along with other studies, are compiled into our GIS statewide landslide database (accessible on our Interactive Map), which has over 45,000 recorded landslides. That database makes up about 2 percent to 3 percent of the landmass of Washington State.
Data from the landslide database are used in a variety of ways:
- Land management decisions
- Land use decisions
- Real estate purchases
- Timber harvests
- Siting and construction of homes, other structures, roads and other infrastructure.
Landslide data are also used to create landslide hazard and susceptibility maps. These maps show areas with various levels of instability (usually from low to high instability) and help to simplify the assessment of a location’s hazard. Landslide data can also be used in landslide forecasting. DNR is working with the University of Washington and the National Weather Service to develop a statewide landslide forecasting system, similar to the system created by the USGS for the Seattle Area.
Data are critical to understanding landslides in Washington State. A landslide changes quickly after it happens: earth is washed away, settles, or is removed when it blocks a roadway. For the highest level of accuracy, data need to be collected as soon as possible after the event.
Here is how you can help. No matter where you are, if you see a landslide, please report it. Follow the DNR’s How to Report a Landslide, fill out the form and send it in. Don’t assume we know about a landslide; we’d rather get duplicate reports than get none at all. [Lots more landslide photos--'debris avalanches' is what geologists call them--on DNR's Flickr page.]
Tags: DNR, geology, landslide, Washington
