Washington is one of the most landslide-prone states in the country, with hundreds to thousands of events each year. A landslide is a rock, earth, or other materials moving down a slope. Landslides occur when the strength of the material on a slope becomes less than the force of gravity acting on the material. They can be caused by rain, earthquakes, volcanoes, or changes to the land.
Landslides are dangerous and unpredictable. Some landslides may provide clues that they are about to happen; others may happen suddenly without any warning signs. Landslides can travel 55-100 miles per hour.
Locations that experienced landslides in the past are more likely to have future landslides. Know what areas near your home or work are at risk. Know which areas are safe and how to reach them in an emergency. If possible, avoid living in locations that are hazardous such as areas above or below steep slopes.
Learn the warning signs of an impending landslide:
- Cracks growing in the ground; downslope movement of rock, soil, or vegetation.
- Sudden changes in creek water levels, sometimes with increased sediment, especially during or right after large storms.
- Sounds of cracking wood, knocking boulders, groaning of the ground, or other unusual sounds.
Learn the warning signs of a potential landslide:
- Hillsides that have been saturated from extreme rainfall events.
- Sagging utility lines; leaning telephone poles, deformed fences, or the tilting of trees on a hillside.
- Sticking windows or doors; new and or growing cracks in walls, ceilings, or foundations.
- Broken or leaking utilities, such as water, septic, or sewer lines.
- Watch for collapsed pavement, mud, fallen rock, or other debris on roadways.
Have a go-kit ready in case you must leave immediately. Keep copies of important documents in a safe place. Consider planting ground cover or building walls to direct mudflows around buildings. Talk to your insurance agent to see if your policy covers damage from landslides.
Be Safe DURING
If you notice these signs or observe a landslide in the process, leave the area immediately if it is safe to do so! Landslides are dangerous, unpredictable, and can occur rapidly. A landslide can easily destroy or bury a car or house. Report the problem immediately to local officials.
If you are under a landslide warning:
- Evacuate an area immediately after authorities tell you to. Signs of a landslide may not be visible, but the danger still exists.
- Watch for flooding. Floods sometimes follow landslides because they may be started by the same event.
- Listen to Emergency Alert Systems for current emergency information and instructions.
Be Safe AFTER
Listen to authorities to find out if it is safe to return. Stay away from downed power lines and report them immediately. Check the building foundation, chimney, and surrounding land for damage. Damage to these may help you assess the safety of the area. Seek advice from a geotechnical expert for evaluating landslide hazards or designing corrective techniques to reduce landslide risks.