DNR FIELD NOTES
January 12, 2010
Landslides in Washington State: Not just a ‘California thing’
By Dave Norman
Washington State Geologist
Washington State Department of Natural Resources
The landslide that rumbled over Highway 410 near Naches last October—and still blocks it—is a stark reminder that Washington State is landslide country. That slide in Yakima County was one of the largest ever recorded in our state, but it is not the only time the earth has slid in Washington. In fact, it happens many times every year.
Landslides can threaten lives, property, transportation, utilities and everyone’s peace of mind. The Washington State Department of Natural Resources (DNR) keeps a database of landslides large and small. We do this to help private citizens, businesses and local governments make important decisions, such as where—or where not—to build that house, school, business, power line or roadway.
So far, we’ve mapped more than 45,000 landslides and risk areas. This database is online there you’ll find the Washington Interactive Geologic Map site (http://wigm.dnr.wa.gov/) which shows mapped landslides. A good database helps everyone to better understand the risks. DNR’s database still only scratches the surface of the potential number of landslides that have occurred and can happen again.
We need your help to continue building this database. Many landslides may be too small to make the evening news unless someone has built a home on it. But please report landslides to your local safety authorities and to DNR.
Timely information is critical to understanding landslides. A landslide changes quickly after it happens: earth is washed away, settles, or is removed. For the highest level of accuracy, data need to be collected as soon as possible after the event.
Winter is primetime for landslides, especially in many parts of Washington. What may appear to be minor settling could be the early signs of larger earth movement about to happen. Be vigilant for:
- Cracked drywall, sticky doors and windows
- New cracks or unusual bulges in the ground, driveways, roads or sidewalks
- Soil moving away from foundations
- Tilting foundations
- New springs or abnormal saturation of the ground
- Leaning utility poles, trees, retaining walls or fences.
People living near landslides often report hearing a faint rumbling, cracking, and other unusual sounds in the hours before the earth slides.
As the state’s geological survey, DNR has geologists who collect data about these landslides. They document the locations, damage, and site conditions. We make note of details such as the steepness of the slope, geology, the type of land use, and other critical data. We combine this information with other studies and compile it into our statewide landslide database to help citizens, businesses and government agencies make decisions about:
- Land use and management;
- Real estate purchases;
- Timber harvests; and the
- Siting and construction of homes, other structures, roads and other important infrastructure.
DNR also publishes landslide hazard and susceptibility maps that can make it easier to assess and even forecast the chances of a landslide at a location.
If you see a landslide, please report it. Go to DNR’s website and fill out the form at How to Report a Landslide. Don’t assume we know about a landslide; we’d rather get duplicate reports than none at all.
Media Contact: Bob Redling, Senior Communications Manager, 360-902-1149, firstname.lastname@example.org