Nature's power can be destructive, especially when tons of massive rocks, mud, and debris move down a slope. Landslides in the United States cause approximately $3.5 billion (year 2001 dollars) in damage, and kill between 25 and 50 people annually, according to the U.S. Geological Survey (USGS). Worldwide, landslides cause thousands of casualties and billions in financial losses annually.
The deadliest landslide in U.S. history occurred in northwest Washington on March 22, 2014. Debris from the natural disaster covered at least 40 homes and other structures as well as a major highway. It caused 43 fatalities in the town of Steelhead Haven near Oso, Washington.
Landslides happen quickly
USGS research indicates that the average speed of the "Oso Landslide" was about 40 miles per hour, with maximum speeds likely even higher. The area overrun by the landslide was about one half square mile. The landslide moved about 18 million tons of sand, glacial sediment, and clay—enough debris to cover approximately 600 football fields 10 feet deep.
In May of 2014, a landslide killed three people in western Colorado when 50 million tons of rocks and mud shot down a mountainside near the town of Collbran. The slide shook the surrounding area, registering as a small, 2.8-magnitude earthquake, according to the USGS. The disaster left a trail of destruction more than 3 miles long and a half-mile wide, according to The Denver Post.
Landslides can occur quickly and with little notice. The best way to prepare is to stay alert about changes in and around your property that could signal that a landslide is likely to occur.
Here are 12 tips from Ready.gov to help protect you, your family, and your property from the powerful forces of a landslide or debris flow.
In this March 24, 2014 file photo, the massive mudslide that killed 43 people in the community of Oso, Wash., is shown from the air. (AP Photo/Ted S. Warren, File)
1. Avoid building near steep slopes, close to mountain edges, near drainage ways or along natural erosion valleys.
A child's bicycle is with other remains at the edge of the scene of the deadly mudslide from the barren hillside beyond Tuesday, March 25, 2014, in Oso, Wash. The 1-square-mile slide hit in a rural area about 55 miles northeast of Seattle on Saturday. (AP Photo/Elaine Thompson)
2. Learn whether debris flows have occurred in your area by contacting local officials. Slopes where debris flows have occurred in the past are likely to experience them in the future.
A home destroyed in a landslide after heavy rains. (IrinaK / Shutterstock.com)
3. Get a ground assessment of your property.
A boat, house and SUV caught in the path of a landslide. (Cindy Jenkins / Shutterstock.com)
4. Consult a professional for advice on appropriate preventative measures for your home or business, such as flexible pipe fittings, which can better resist breakage.
Workers installing a new, large block retaining wall. (Photo: TFoxFoto / Shutterstock.com)
5. Protect your property by planting ground cover on slopes and building retaining walls.
People walk along a flooded street near a landslide that caused the evacuation of several homes, Monday, Jan. 5, 2015 in Hoquiam, Wash. (AP Photo/Ted S. Warren)
6. In mudflow areas, build channels or deflection walls to direct the flow around buildings. Be aware, however, if you build walls to divert debris flow and the flow lands on a neighbor's property, you may be liable for damages.
Mario Ramirez helps to remove mud from Catherine Markgraf's house after a mudslide caused by heavy rains damaged her house in La Canada Flintridge, Calif. on Monday, Feb. 8, 2010. (AP Photo/Hector Mata)
7. If you are at risk from a landslide, talk to your insurance agent. Debris flow may be covered by flood insurance policies from the National Flood Insurance Program (NFIP).
This photo released by the West Virginia National Guard shows a landslide Thursday, March 12, 2015 near Yeager Airport in Charleston, W. Va. The landslide broke loose, taking out power lines, trees, an unoccupied home, as well as a church. It also caused a nearby creek to rise. Luckily, no injuries were reported and no flights at the airport were affected. (AP Photo/West Virginia National Guard-Lt. Col. John “Todd” Harrell.)
8. Recognize landslide warning signs
- Changes occur in your landscape such as patterns of storm-water drainage on slopes (especially the places where runoff water converges) land movement, small slides, flows, or progressively leaning trees.
- Doors or windows stick or jam for the first time.
- Outside walls, walks, or stairs begin pulling away from the building.
- Slowly developing, widening cracks appear on the ground or on paved areas such as streets or driveways.
- Underground utility lines break.
- Bulging ground appears at the base of a slope.
- Water breaks through the ground surface in new locations.
- Fences, retaining walls, utility poles, or trees tilt or move.
- A faint rumbling sound that increases in volume is noticeable as the landslide nears.
- The ground slopes downward in one direction and may begin shifting in that direction under your feet.
- Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.
- Collapsed pavement, mud, fallen rocks, and other indications of possible debris flow can be seen when driving (embankments along roadsides are particularly susceptible to landslides).
In this Aug. 5, 2014, file photo, workers inspect a large landslide that destroyed one home and caused the evacuation of dozens more in North Salt Lake, Utah. (AP Photo/Rick Bowmer, File)
9. During a severe storm, stay alert and awake. Many deaths from landslides occur while people are sleeping.
The orange X on a house, destroyed in the mud, indicates it has been searched for people on Highway 530, Sunday, March 23, 2014 the day after a giant landslide occurred near Oso, Wash. (AP Photo/The Seattle Times, Lindsey Wasson, Pool)
10. If you are near a stream or channel, be alert for any sudden increase or decrease in water flow and notice whether the water changes from clear to muddy. Such changes may mean there is debris flow activity upstream so be prepared to move quickly.
A house is seen destroyed in the mud on Highway 530 next to mile marker 37 near Oso, Wash., on Sunday, March 23, 2014. (AP Photo/The Seattle Times, Lindsey Wasson, Pool)
11. Listen for unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together.
Damaged homes sit on a hillside after a landslide in Laguna Beach, Calif., in this June 1, 2005 file photo. The Laguna Beach landslide destroyed at least 11 homes and displaced hundreds of residents. (AP Photo/Nick Ut)
12. Mudflows can move faster than you can walk or run. Move away from the path of a landslide or debris flow as quickly as possible.