Staying Safe in a Landslide-prone State

By Gordon Williams

The state Department of Ecology warns that “landslides are common in Washington state.”

Those who live here know how true that is. Landslides are always in the news — from the tragic Oso slide of 2014 that killed dozens, to minor slides that damage property. In a single day, recently, one landslide split Highway 302 in Mason County and another blocked Highway 18 in Auburn WA.

With landslides somewhat of a way of life in Washington, two questions arise:

First, WHY are landslides common in Washington state?

Second, WHAT can you do to keep safe in a region where the danger of landslides is real and relentless? (Landslides mostly carry debris; mudslides are 60 percent or more water.)

To answer the WHY question, just look at the geography and the climate of Washington state. Steep slopes abound in Washington — especially around Puget Sound — with top soil resting precariously on loose sand and gravel. Add in wildfires that scour the land bare, and then pour down buckets of rain that turn the ground into gumbo.

As for the WHAT can you do question, because landslides are so common in Washington you won’t have to look far to find safety advice from many sources — among them the Department of Ecology, the Washington Department of Natural Resources (DNR) and the American Red Cross. The state’s DNR, for instance, publishes a map that shows the areas within Washington that are most susceptible to landslides. You can find it, and lots more, including A Homeowner’s Guide to Landslides, at dnr.wa.gov/landslides.

Consult local planning and emergency management agencies to determine if you live in an area with a high risk of slides. If there has been one slide in the area, there will very likely be more. Make checking for possible landslide risk one of the investigative things you do before buying or building a house. Be especially wary of property at the edge of a steep slope, or near the bottom of a slope.

Follow whatever advice you get from the local planning department about mitigating the risk of a slide. Make sure that anyone doing construction work on your property is familiar with the local geology. Consider hiring an engineer with some expertise in geology to examine your property and estimate the risk.

Trees and other plantings help both stabilize the soil and sop up excess moisture, so maintain existing vegetation and add to it when you can. Allow native plants to take hold on slopes to further help anchor the soil. Grass seed is likely to be washed away quickly, and any grass that does take root could squeeze out the vegetation you want to grow on the slope. Have a pipe system that conveys run-off water from the roof and other impervious surfaces. Never place a septic system between the house and the edge of a cliff.

If you are in a landslide danger zone, know about indicators that could warn of a slide in the making. Look for things like:

water standing in areas that typically are dry.
cracks or bulges in the ground and or in roads or sidewalks.
trees, poles and fences that are leaning.
windows and doors that stick or won’t close easily

The Red Cross in its Emergency mobile app offers advice on what to do before, during and after a slide. The app is available at the Apple Store and Google Play.

You would prepare for a slide as you would for any emergency — creating a go-kit of emergency supplies, having a plan for getting the family to safety and training everyone in how to implement that plan. Stay tuned to local news stations when the risk of slides is high — during a flooding rainstorm, for instance. Stay awake until the danger is past. “Many deaths from landslides occur while people are sleeping,” says the Red Cross.

Know the sounds that could signal a slide. The Red Cross says they could include “debris moving, trees cracking or boulders knocking together.” If you are near moving water, be alert for any rise in the water flow. If water that was clear turns muddy, it could mean a slide has blocked the water upstream.

If you suspect imminent danger, says the Red Cross, “evacuate immediately, inform affected neighbors if you can, and contact your local public works, fire, or police departments.” Be cautious driving away from the slide, since sections of the road may have collapsed or been blocked by mud and debris. Finally, the Red Cross warns to stay away from the slide area until officials say it is safe to return.