Hurricanes, floods, tornadoes, fires — these are all well known and understood perils, and you likely have a pretty good idea of what’s covered by your insurance (especially if you live in a flood zone). But what about some lesser understood perils: landslides, mudslides and mudflow. These perils cause an estimated 25-50 deaths and $1 billion dollars in property damage each year in the United States.[1]
So what are these three perils? What are the differences, what should you do if you're in a risk-prone area and which are potentially covered by your home insurance?
What are landslides, mudslides and mudflow?
Landslides are not just a popular Fleetwood Mac song and mudslides are not just a tasty cocktail. These perils can be incredibly dangerous and destructive and can occur in every U.S. state. These are natural hazards that involve the downward movement of rock, soil, debris or other unstable geologic material, often triggered by gravity. They can cause significant destruction to property, landscapes, and even human life, especially in areas prone to heavy rainfall, seismic activity or human disturbance.
- Landslides are the general term for a variety of processes that cause the downhill movement of masses of rock, earth, or debris. They generally strike in locations with steep slopes and can be the result of human activities (engineering, irrigation, agriculture), wildfires and seismic activity.
- Mudslides, also known as debris flows, are a moving mass of loose mud, sand, soil, rock and water that travel down a slope. Differentiating from a landslide, a mudslide must have loose enough material to be capable of moving and more than half of the solids in the mass must be larger than sand grains.
- Mudflows are often used interchangeably with mudslides, and they are essentially mudslides’ sandier and more watery counterparts. A mudflow behaves more like a liquid. They typically occur after intense rainfall or snowmelt saturates the ground, making it unstable.
Where do landslides, mudflows and mudslides occur?
Landslides and mudflows can happen worldwide, but certain regions are more prone due to their geographical, environmental, or weather conditions. Common areas include:
- Mountainous regions: Areas with steep terrain are naturally susceptible to landslides, especially after rainfall or during seismic events. The Appalachian Mountains, Rocky Mountains, Pacific Coast Range and parts of Alaska and Hawaii are particularly prone to landslides, but they occur in all U.S. states.[2]
- Coastal cliffs: Landslides often occur along coastlines with steep cliffs where waves and wind erode the rock base. For example, the California coastline is frequently affected by landslides during and after rainy seasons.
- Volcanic areas: Mudflows, known as lahars, are a common occurrence in volcanic regions. When volcanic eruptions melt snow or heavy rainfall loosens volcanic ash deposits, mudflows can sweep down volcanic slopes at high speeds, causing catastrophic damage. The Pacific "Ring of Fire" is an example of an area where this occurs.
- Areas with loose or eroded soil: Agricultural regions with poorly managed lands, deforested areas (such as through farming or wildfires) or places that have undergone significant urban development can also be vulnerable to landslides, mudflows and mudslides.
- Earthquake-prone zones: Landslides can occur following an earthquake when the shaking causes already loose or saturated soil to give way.
What should you do if you’re affected by a landslide, mudflow or mudslide?
If you're living in or near a region prone to landslides or other debris movement, it’s crucial to be prepared and take action quickly if a disaster strikes. Here’s what to do before, during and after such an event:
Before the landslide:
- Stay informed: Know whether your area is prone to landslides, mudslides or mudflows. Sign up for local weather alerts, and be aware of changing conditions such as heavy rain, snowmelt or seismic activity.
- Prepare your property: Make sure your drainage systems are clear, particularly if you live near slopes. Consider retaining walls and other structural defenses if your property is at risk.
- Have an emergency plan: Establish evacuation routes and a communication plan with your family. Prepare an emergency kit with supplies like water, food, flashlights and first aid materials.
During the landslide:
- Evacuate immediately: If a landslide warning is issued or you notice signs of instability (cracking or bulging ground, trees tilting, sounds of rumbling), leave your home immediately and move to higher ground.
- Avoid river valleys or slopes: Mudflows often follow natural drainage paths like rivers or creeks, so avoid low-lying areas that might channel debris flows.
- Do not drive through floodwaters or debris: Roads may be washed away, and even shallow water can sweep vehicles off-road. If you are in a car, get out and move to higher ground on foot.
After the landslide:
- Stay away from the affected area: Mudflows and landslides may still be active, or secondary slides could occur. Avoid going back to the site until authorities declare it safe.
- Check for structural damage: If your home was in the affected area, look for damage to foundations, roads and utilities. Avoid entering buildings that are visibly unstable.
- Report hazards: Contact local authorities about downed power lines, broken gas lines or other hazards. Be careful about contaminated water sources.
Wrapping up
Landslides and mudflows are destructive and unpredictable natural hazards. While certain areas are more prone to these events, anyone living near mountains, cliffs or loose soil may be at risk.
Understanding the signs of potential landslides, preparing accordingly, and knowing how to respond in an emergency can be lifesaving. Ensuring the right insurance coverage is also vital to protect your property from potentially devastating financial losses. Be proactive, stay informed, and have a plan in place to reduce the impact of these natural disasters on your life and property.
FAQs about landslides, mudslides and mudflows
Here are some common questions you may have about these perils.