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The deadliest landslides are the ones that happen fast, often with little notice. Landslides occur in all U.S. states and territories, and earthquakes, storms, volcanic eruptions, fire and human changes to land can all set them off. A landslide is a mass of rock, mud or debris moving down a slope, and a wildfire on a slope raises the chance of landslides for several years.
Image from Ready.gov's page.
Fast and slow
How to protect yourself and your property depends on the type. Land-use zoning, professional inspections and proper design can reduce many problems, but for a debris flow or other fast slide, evacuation is often the only way to protect lives. Slow slides creep in fits and starts, no more than three feet a year; they rarely kill but can damage land and property over time.
Before
- Build an emergency kit and make a household plan, pets included.
- Sign up for your community's warning system. The Emergency Alert System and NOAA Weather Radio also give alerts.
- Leave if told to evacuate or if you feel unsafe. Text SHELTER and your ZIP code to 43362 to find a shelter.
- Ask a professional about measures such as flexible pipe fittings, which resist breakage better.
- Follow a geotechnical professional's or local guidance. You cannot stop or redirect a debris flow, but sandbags, retaining walls or k-rails may protect against floodwater or mud.
- Channels or deflection walls may steer a flow around buildings, but a big flow goes where it pleases, and you may be liable if you divert one onto a neighbor's land.
- Ask your insurance agent; flood insurance from the National Flood Insurance Program may cover debris flow.
Warning signs
| Fast-moving (threat to life) | Slow-moving (threat to property) |
|---|---|
| Sign up for alerts and watch forecasts if near a wildfire burn area | Changes in drainage patterns on slopes, small slides, progressively leaning trees |
| Rushing water, mud or unusual sounds: trees cracking, boulders knocking, a faint rumble that grows | Doors or windows that stick for the first time |
| Huge boulders in the landscape can mark past debris flows | New cracks in plaster, tile, brick or foundations |
| Walls, walkways or stairs pulling away from a building | |
| Widening cracks in the ground or pavement; bulging ground at a slope's base | |
| Broken underground utilities; water breaking through the ground in new places | |
| Fences, retaining walls, poles or trees tilting |
During
- Follow local emergency managers and listen for warnings on a battery-powered radio.
- Stay alert and awake in a storm that could cause a slide. Many deaths happen during sleep.
- By the time you are sure a debris flow is coming, it is too late to get away safely. Never cross a road with water or mud flowing, or a bridge if you see a flow approaching, since it can grow too quickly to escape.
- If caught in the path, move uphill as quickly as possible, and avoid river valleys and low-lying areas.
- Near a stream, watch for a sudden rise or fall in flow, or water turning from clear to muddy.
After
- Stay away from the slide area, which may slide again, and keep listening for emergency information.
- Watch for flooding, since floods often follow because the same conditions cause both.
- Check for injured or trapped people near the slide without entering it, and direct rescuers to them.
- Report broken utility lines and damaged roads and railways so utilities are shut off quickly.
- Have trained professionals check the foundation, chimney and surrounding land.
- Replant damaged ground soon, since erosion from lost cover can cause flash floods and more slides.
- Seek a geotechnical expert's advice on evaluating and reducing risk.
Sources
- FEMA, Landslides & Debris Flow, Ready.gov; rewritten in hubnx's own words.
Licence : CC0 1.0 (domaine public) · Adapté de www.ready.gov
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