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Two mini vans - one red and one white - are caught in a landslide and have fallen off the road

Landslides & Debris Flow

Landslides occur in all U.S. states and territories and can be caused by many factors including earthquakes, storms, volcanic eruptions, fire and human modification of land. The most deadly landslides are the ones that occur quickly, often with little notice.

In a landslide, masses of rock, earth or debris move down a slope. Debris and mud flows are rivers of rock, earth and other debris saturated with water. They develop during intense rainfall, runoff, or rapid snowmelt, changing the earth into a flowing river of mud or “slurry.” They can flow rapidly, striking with little or no warning at avalanche speeds (faster than a person can run). They also can travel many miles from their source, growing in size as they pick up trees, boulders, cars and other materials. Debris flows don’t always stay in stream channels and they can flow sideways as well as downhill.

When a wildfire burns a slope, it increases the chance of debris flows for several years. Although some landslides require lengthy rain and saturated slopes, a debris flow can start on a dry slope after only a few minutes of intense rain. “Intense” rain means a burst of rain at a fast rate, about half an inch in an hour. With debris flows, the rate matters more than total rainfall.

How to protect yourself or your property depends on the type of landslide. Land-use zoning, professional inspections, and proper design can reduce many landslide problems but evacuation is often the only way to protect lives from a debris flow or other fast-moving landslide. Never ignore an evacuation order.

Before a Landslide

The following are things you can do to protect yourself, your family and your property from the effects of a landslide or debris flow:

  • To begin preparing, you should build an emergency kit and make a family communications plan.
  • Make a plan for your household, including your pets, so that you and your family know what to do, where to go, and what you will need to protect yourselves from landslides during the COVID-19 pandemic.
  • Connect with your local emergency services, heed evacuation warnings.
    • Sign up for your community’s warning system. The Emergency Alert System (EAS) and National Oceanic and Atmospheric Administration (NOAA) Weather Radio also provide emergency alerts.
    • Sign up for email updates and follow the latest guidelines about coronavirus from the Centers for Disease Control and Prevention (CDC) and your local authorities to prevent the spread of COVID-19.
  • Leave if you have been told to evacuate or you feel it is unsafe to remain in your home. Text SHELTER + your ZIP code to 43362 (4FEMA) to find the nearest shelter in your area (example: shelter 12345).
  • Prepare for landslides by following proper land-use procedures - avoid building near steep slopes, close to mountain edges, near drainage ways or along natural erosion valleys.
  • Become familiar with the land around you. Learn whether landslides have occurred in your area by contacting local officials. However, don’t assume that what happened last time will happen next time. Debris flows can start in places they’ve never been and return to slopes where they’ve already been.
  • Get an assessment of your property by a qualified geotechnical professional.
  • Consult a professional for advice on appropriate preventative measures for your home or business, such as flexible pipe fittings, which can better resist breakage.
  • Protect your property based on of recommendations from the ‘qualified geotechnical professional’ and/or local city/county guidance on protection from debris flow and flooding.  You can't stop or change the path of a debris flow. However, you may be able to protect your property from floodwaters or mud by use of sandbags, retaining walls or k-rails (Jersey barriers).
  • In mud and debris flow areas, consider building channels or deflection walls to try to direct the flow around buildings. Be aware, however, that when a flow is big enough, it goes where it pleases. Also, if you divert a flow and it flows on a neighbor's property, you may be liable for damages.
  • 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).
  • Gather supplies in case you have to leave immediately or if services are cut off. Keep in mind each person’s specific needs, including medication. Do not forget the needs of pets.
    • Include non-perishable foods, cleaning supplies, and water for several days, in case you have to leave immediately or if services are cut off in your area. If you are able to, set aside items like soap, hand sanitizer that contains at least 60 percent alcohol, disinfecting wipes, and general household cleaning supplies that you can use to disinfect surfaces you touch regularly. After a landslide, you may not have access to these supplies for days or even weeks.
    • Being prepared allows you to avoid unnecessary excursions and allows you to address minor medical issues at home, alleviating the burden on urgent care centers and hospitals.
    • Remember that not everyone can afford to respond by stocking up on necessities. For those who can afford it, making essential purchases and slowly building up supplies in advance will allow for longer time periods between shopping trips. This helps to protect those who are unable to procure essentials in advance of the pandemic and must shop more frequently. In addition, consider avoiding WIC-labeled products so that those who rely on these products can access them.

Recognize Warning Signs

Watch for debris flows and other fast moving landslides that pose threats to life:

  • If you are near a wildfire burn area, sign up for emergency alerts and pay attention to weather forecasts for the burn area. The weather in the burn area could be very different from where you are.
  • Listen and watch for rushing water, mud, unusual sounds.
  • Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.
  • A faint rumbling sound that increases in volume is noticeable as the landslide nears.
  • Fences, retaining walls, utility poles, k-rails, boulders, or trees move.
  • Huge boulders in the landscape can be signs of past debris flows.

Watch for slow-moving landslides that pose threats to property:

  • 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.
  • New cracks appear in plaster, tile, brick, or foundations.
  • 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.
  • The ground slopes downward in one direction and may begin shifting in that direction under your feet.

During a Landslide

  • Listen to local news stations on a battery-powered radio for warnings.
  • Heed all warnings and evacuation notices.
    • Always follow the instructions from local emergency managers. They provide the latest recommendations based on the threat in your community.
    • Make plans to shelter with friends or family in advance so that you can evacuate to their safe location. If you are unable to do so, check with local authorities to determine which public shelters are open. Review your previous evacuation plan and consider alternative options to maintain social and physical distancing to prevent the spread of COVID-19.
    • If you are sheltering with people who are not part of your household, be sure to wear a mask and maintain a distance of at least six feet between yourself and others. Masks should not be worn by children under two years old, people who have trouble breathing, and people who cannot remove them on their own.
    • If you are told by local authorities to evacuate to a public shelter, try to bring items that can help protect yourself and your family from COVID-19, such as hand sanitizer that contains at least 60 percent alcohol, general household cleaning supplies, and two masks per person.
  • During a storm that could cause a landslide, stay alert and awake. Many deaths from landslides occur while people are sleeping.
  • Be aware that by the time you are sure a debris flow is coming, that will be too late to get away safely. Never cross a road with water or mud flowing. Never cross a bridge if you see a flow approaching. It can grow faster and larger too quickly for you to escape.
  • If you do get stuck in the path of a landslide move uphill as quickly as possible.
  • Avoid river valleys and low-lying areas during times of danger.
  • If you are near a stream or channel, be alert for any sudden increase or decrease in water flow or water that changes from clear to muddy. These can be signs that a landslide is coming.

After a Landslide

  • Stay away from the slide area. There may be danger of additional slides.
  • Listen to local radio or television stations for the latest emergency information.
  • Watch for flooding. Floods sometimes follow landslides and debris flows because they may both be started by the same conditions.
  • Check for injured and trapped persons near the slide, without entering the direct slide area. Direct rescuers to their locations.
  • Report broken utility lines and damaged roadways and railways to appropriate authorities. Reporting potential hazards will get the utilities turned off as quickly as possible, preventing further hazard and injury.
  • Allow trained professionals to check the building foundation, chimney, and surrounding land for damage.
  • Replant damaged ground as soon as possible since erosion caused by loss of ground cover can lead to flash flooding and additional landslides in the near future.
  • Seek advice from a geotechnical expert for evaluating landslide hazards or designing corrective techniques to reduce landslide risk. A professional will be able to advise you of the best ways to prevent or reduce landslide risk, without creating further hazard.
  • Continue taking steps to protect yourself from COVID-19 and other infectious diseases, such as washing your hands often and cleaning commonly touched surfaces with disinfecting products.
  • Engage virtually with your community through video and phone calls. Know that it’s normal to feel anxious or stressed. Take care of your body and talk to someone if you are feeling upset. Many people may already feel fear and anxiety about the coronavirus 2019 (COVID-19). Follow CDC guidance for managing stress during a traumatic event and managing stress during COVID-19.

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Last Updated: 02/19/2021