Landslides are one of the disasters that make the least amount of headlines, yet are surprisingly common and highly destructive.
I’m sure most of the world found out about the Montecito mudslide that occurred in the northwest of Los Angeles in 2018. But did you hear about all the other 100+ landslides in 2019 that made it a record-breaking year in terms of fatalities?
If you didn’t, I urge you to read through this page and check if your city and home are located in high-risk areas. Unfortunately, many people don’t know they are until the moment a slide happens.
Perhaps I sound a little dramatic? Maybe! But if most people understood their risk, you'd probably understand why.
Why is a landslide dangerous?
Landslides can travel long distances at fast speeds and sweep or bury anything along their path, including infrastructure, people, and even entire cities. They’re difficult to predict because they behave like something that breaks under pressure. In a moment’s notice, the layer of clay or dirt right beneath the surface of the Earth may give way to the pressure that is accumulating above it. From then on, you’re at nature’s mercy.
Luckily, Australian researchers have developed a technology that uses mathematics and Artificial Intelligence to predict landslides weeks in advance. The terrain, the environment, and the evidence of previous landslides offer great insight into the hazards of a region and the probability of a landslide occurring in the future. The problem with this new technology is that it will take a very long time to implement it world-wide.
So, for the time being, your time would be better spent prioritizing your safety and your home’s stability, rather than the arrival of an early-detection device warning you of a possible threat.
In this guide, you will learn how to prepare your family and your property for this type of disaster.
[This is a long article about landslide preparedness, so the links in the Table of Contents may help you to navigate through the page. If you don't have much time and want to dive right into the meat of this article, please click here.]
Interesting facts about landslides
- Landslides can occur in all 50 US States.
- On average, landslides cause 25 to 50 fatalities and $1-2 billion in damage every year in the US alone. The worldwide death toll surpasses the thousands.
- The average landslide travels at 10 mph but some can travel up to 35 mph or more.
- The biggest landslide in the world happened during the eruption of Mount St. Helens in Washington State, CA on May 18, 1980. This landslide traveled down the Toutle River at speeds of 70 to 150 mph for approximately 14 miles, destroying infrastructure, injuring thousands, and killing some along the way.
- The deadliest landslide occurred in Haiyuan Flows, China on December 16, 1920. This landslide occurred after an earthquake of an 8.5 magnitude struck the region. The death toll exceeded 100,000 people. It buried an entire village and killed half of the population of Haiyuan County.
Landslide terms you should know
Landslide - This is the general term for the slipping of rock, dirt, mud, or snow from a cliff or mountain. There are many causes for landslides so we’ve discussed them below.
Mudslide - As the name suggests, a mud slide is when a large amount of mud dirt has slipped down a slope.
Mudflow (or) Debris Flow - This term describes a more “flowy” version of a mudslide. A mudflow is a lot more liquid-based than a mudslide. It travels extremely fast making them especially dangerous. Imagine an avalanche made of mud- that’s a mudflow.
Rockfall - A rockfall refers to the abrupt collapse of a rock near a steep mountainside or cliff.
Rockslide - Now imagine an avalanche made of rock- that’s a rockslide. Rockslides occur when there’s rock failure near a slope or cliff.
Avalanche - An avalanche is a landslide composed of snow, ice, and rocks.
Lahar Flow - Lahar is the same as a mudslide except that contains volcanic materials. Lahar flows from the crevices and steep terrains of volcanos.
More information on types of landslides can be found here.
Live map of potential landslides
NASA has a map called the Precipitation and Applications Viewer. It shows you the accumulation of rainfall in any given region. Select your area from the dropdown menu and click on “load data.” Then, it will show you a variety of colors that can be understood by the legend. If you don’t see it, click on “show legend” below the map. This map is updated often by satellite. It provides you with a rough idea of how much rainfall is expected, and if there’s a chance of landslides or not.
You should not use this map as your only way of determining your risk, however. Instead, listen to the NOAA Weather Radio for up-to-date information.
The USGS released a map called the US Landslide Inventory. This is an interactive map that highlights areas that may be at risk of future landslides. It categorizes the probably of such an event in different colors, and lets you search for specific locations with their address and coordinates feature.
What to expect during a landslide
What causes a landslide?
Landslides can be caused by a combination of different factors.
In its simplest terms, a landslide occurs when the lower layer of soil loses its ability to withstand the pressure of anything lying above it. You can expect it to give way with force, and depending on the soil, the Earth might only slip a short distance or it can travel up to a few miles. Some cases are more tragic than others due to the moisture level and other conditions of the soil, but in any case, you should always be prepared for the worst-case scenario.
Most landslides are triggered by either natural or manmade disasters.
Several manmade disasters can cause a landslide, such as:
- Dynamite used in mining
- Technology that releases strong vibrations into the earth
- Underground pipes that are leaking
- Roads that have poor drainage
- The removal of rock in unstable areas
Geological processes and natural disasters that trigger landslides include the following:
- Erosion: As the Earth gets worn down from the weather and environment, the rocks, dirt, and all other particles break apart and deteriorate, eventually causing landslides.
- Too much moisture: If the lower levels of the soil contain too much water or are too porous, they might become too weak to sustain the heavier soil above it and eventually collapse.
- Heavy rain: Landslides are common after episodes of heavy rainfall because the ground becomes saturated with water and naturally it loses its ability to hold itself together. Tropical storms, hurricanes, monsoons, and other water-related storms can greatly improve the chances of a landslide.
- Earthquakes: Landslides triggered by earthquakes are caused by liquefaction.
- Wildfires: Landslides that occur in post-fire regions can be fast-moving, making them extremely dangerous and destructive. One perfect example is the 2018 Montecito Landslide that occurred after just weeks one of California’s worst wildfires burned through many parts of Ventura County. You can capture a few glimpses of this tragic event right here.
When is landslide season?
There’s no such thing as a landslide season because they can occur at any time. The most common time of the year, however, is during episodes of heavy rainfall and winter. Depending on where you live, your risk could be higher in the summer especially during monsoon, tropical storms, and hurricane season and/or during the winter season.
Where do landslides occur?
Landslides can occur throughout the United States in mountainous, hilly and coastal regions as well as near river valleys. The regions that are more susceptible are the ones that receive large amounts of water (rain/ snow) and have harsher climates.
The states most prone to landslides are California, Oregon, Washington, Alaska, and Hawaii, as well as the regions near the Mississippi River, the Appalachian Mountains, the Rocky Mountains, the Cascades volcanic region, and the Pacific Coastal Ranges.
Can landslides be predicted?
Landslide-prone locations can somewhat be predicted but the timing of them cannot. One of the main ways that they can be forecasted, is by looking at the regions where they already occurred in the past. Areas that have already experienced slips will likely experience them again in a future time.
Researchers study preexisting landslides to examine the factors that made them collapse. Some of the factors include (but are not limited to) the following:
- The steepness of a mountain, hill or cliff
- Existing drainage channels
- Erosion which is especially common near riverbanks and cliff-sides
- Seasons of excess amounts of rain
- Water-saturated places that are not used to being wet
- Mountainous regions that experience freezing temperatures
- Manmade projects such as building roads along steep terrains, rock extraction, and mining for example
It’s important to keep in mind that our landscapes are constantly evolving, so landslides can essentially occur anywhere if the environment allows for it.
How do you know if a landslide is coming?
Although their timing is highly unpredictable, there are a few ways you can look out for an approaching landslide. If a landslide is happening and flowing in your direction, you may hear the movement of rocks, cracking trees, and debris colliding against each other. The noise will increase and become louder the closer it gets to you.
You should be extra cautious in high-risk areas. Remember which locations are prone to slips and note any significant weather, such as abundant rain or snowfall in an area that is very hilly.
What type of damage can a landslide cause?
Landslides are known for causing extensive destruction. Some are more devastating than others, of course, but they typically cause major damage to infrastructure. As rocks, mud, or debris flow downhill, they have the potential to bury anything along their path including homes, vehicles, bridges, roads, and buildings. They can cause major damage to a city’s water systems, sewage systems, power lines, nearby lakes, rivers, and wildlife.
Landslides change the topography and ecosystem of a region and in some cases, they can cause flash floods or tsunamis.
Can a landslide kill you?
Yes, they can. Unfortunately many people have lost their lives to landslides or related disasters. The year 2019 was a record-breaking year in terms of fatalities. Approximately 100 fatal landslides were recorded, which accounted for the lives of 358 people.
How to mitigate landslides
- Learn about local hazards and determine you level of risk. Go to this website and see what the USGS has to say about the risk in your particular region. You can search for your home address or general city.
- If you’re considering to move or buy a new house, look into your landslide risk first! Any high-risk areas should be avoided. The best way to prevent a landslide from affecting you, is by living and working in a low-risk zone. Search for your future home on the USGS Landslide Inventory website.
- Obtain an analysis of your property as well as an environmental assessment of the surrounding land. These assessments should provide precise information about which hazards are present in your area. From there you can take proactive action and determine which appropriate measures you should take to protect yourself and your home.
- Implement correction methods and/ or preventative techniques to protect your home. For example, you could build a study retaining wall to stabilize the slope as well as some diversion methods so that the debris doesn’t flow right onto your property. Be cautious when building the wall. Make sure that it does not cause the runoff to go into a neighbor’s home or property. If damages are attributed to your wall or diversion methods, you may be held responsible. If you have an unstable slope or hill on your property, you could try a few things: add vegetation to it, cover it with jute netting or temporarily place a plastic sheeting material over it with some sand bags to hold it down. If you add vegetation or plants to the slope in your property, get a ground cover that doesn’t require too much water. Constantly watering that slope can make it vulnerable to slides because it’s more water-saturated than other areas. It would help to talk to a geotechnical engineer for their advice on what would work best for your property considering the risks you may be facing.
- Note any changes to the nearby topography and make necessary adjustments to your property. Every year, the ground changes because of the weather and erosion. Some storms and natural disasters can be very damaging to the land but may not appear to be hazardous until some time later. To prevent unprecedented landslides, make sure you observe carefully how your property is affected by storms. Can you detect any areas where your home may be susceptible to future damage? Have cracks formed along the side of your foundation or driveway? After a rain storm, does the water tend to collect in one specific area or does it run off into a channel? Find any vulnerabilities and correct them before a larger storm takes you by surprise. You should talk to your neighbors about this also. If they’re also seeing cracks or land changes, that could mean something!
- Thinking about insurance? Unfortunately, landslides are not covered by homeowners insurance and in many cases, they’re not covered by flood insurance either. Since policies vary, I recommend you call your insurance company directly and ask them about any options they may have with respect to insuring you from damage caused by landslides. You may want to check out FEMA’s National Flood Insurance Program because they may cover it.
- Make a family disaster plan. Determine some ways to evacuate your home - plan more than one way out just in case - and make sure each person understands the basic principles of getting themselves to safety. Practice some drills or simulations at home to get the ideas ingrained. That way, if a landslide occurs near you, you will take affirmative action rather than behaving out of reaction.
- Develop a family reunification plan. Reunification plans are crucial because your family members might not be together during an event like this. Consider that you or your spouse may be at work, and your children may be at school or spending the night at a friend’s house. How will you get in touch with each other after the landslide has occurred? Remember that power lines and phone lines might be down, so your mobile device might not be reliable. Look here for some ideas on how to communicate without a phone or internet!
Landslide safety tips
Although unpredictable like most other disasters, landslides are a unique type of disaster because they can be triggered by so many different factors, as we discussed above. Landslides occur with little to no warning, so don’t expect the local officials to issue an evacuation notice in advance.
My main safety tip is to become aware and stay alert of any possible risks. I urge you to take extra precautions before, during, and after large rainstorms or snowstorms especially if you live in a high-risk zone and/or your region has been affected by a wildfire within the last 3 years.
With that said, let’s discuss some of the important safety measures you should take before, during, and after a landslide.
- Observe the topography around you. If you notice some obvious changes in the landscape, such as progressively tilting trees on the hillside or small rockslides occurring down slopes, you should be extra cautious and consider the idea of a possible landslide in the near future. Some other warning signs can be spotted, such as cracks in the floor, concrete or foundation, the soil becoming separated from the foundation of a building or home, a section of the property tilting downward (such as the deck but not the rest of the house).
- Stay updated with the news and their evaluation of any possible risks. The local news and radio are typically the first to alert the crowd of disasters. If your region experienced a wildfire and the weatherman says that rain is expected for the next few days, that should be a warning for you. Determine whether or not it’s safe to stay home.
- If you have a lot of pets or farm animals, consider evacuating them early if you feel that your region is under any danger.
- Keep in mind that many landslides occur during the night, so you should determine the severity of the current and forecasted weather conditions. If you feel that they may threaten to cause a landslide, go with your gut feeling and evacuate.
- Alert your neighbors to get to safety, if you’re able to.
- Leave your belongings behind, but try to evacuate with your pets.
- If a landslide is literally approaching you, RUN! Seriously, your life could depend on it. Run in a lateral (or horizontal) direction away (opposite) from the flow of the debris. If you’re running in the same direction, it will for sure catch up to you. Landslides can flow at extremely fast speeds. Try to get to higher ground or a stable area as soon as possible.
- If evacuation becomes impossible, try run to a higher room of the home that has windows and curl up into fetal position to protect vital organs. Make sure you cover your head and neck to prevent injury. Do not escape to a basement or attic.
- Consider that there’s a possibility that more landslides may follow so don’t approach the affected region immediately.
- Listen for people who may be screaming for help. They may be trapped in their homes, vehicles, or just under the mud. Try not to get into the direct path of where the mudflow occurred. If you’re able to help, do so! If not, report your observations to local authorities and rescue teams as soon as possible.
- Stay updated with the current news. Flash floods and more landslides are likely, so don’t assume that you’re safe after the episode has passed.
- Do not get near any flooded areas. Do not walk, drive, or swim across them because moving water can sweep you away. Plus the water may be contaminated.
- Do not touch or get near downed power lines- they may still be charged.
- Check your home for any damages, especially the underground pipes and foundation.
Landslide emergency kit must-haves
Stocking up on food. water, and other preparedness items is necessary for any disaster but when thinking about landslides, I think it’s especially beneficial for those who live in landslide-prone regions with limited options for obtaining supplies. Let me explain.
I live in a small resort town where there are only three access roads to come and go. If any of those roads experience a landslide (and each of them have, by the way!) then that road gets cut off until the repairs are made. There have been times where two of the roads were blocked by debris flow, and on occasion, entire sections of the roads were washed away. More often than not, roads are closed for weeks if not months. This makes it very difficult for grocery and supply trucks to make their deliveries to our town.
Can you relate to my situation? If so, make sure to have plenty of supplies to sustain you and your family for a minimum of 14 days. Some of the supplies I recommend are the following:
- Water and a method of purification: Water is essential for your survival. Make sure to store enough clean water that can sustain you for the first 3 days and longer, if possible. Consider getting purification tablets or another method of purification. Since landslides can cause damage to water and sewage pipes, you should expect your drinking water source to be contaminated. Do not drink from the tap unless local authorities say it’s safe to do so.
- Long-term food storage: Food is also essential for your survival, but calories alone is not what you need- you must eat nutritious calories. You should store healthy food because it will provide you with the nutrients you need to have energy and perform well after the disaster.
- A method of cooking: A stove and fuel kit like this one is ideal because it can be used indoors and outdoors since it does not release toxic fumes.
- Plasticware: Including plates, cups, utensils, and several black trash bags for easy disposal.
- An evacuation or bug out kit: Include all the essentials that you need to survive for at least 3 days. You can look over this comprehensive list to find some ideas!
- A whistle: You will need it in case you’re trapped and/or need to signal for help.
- A radio: Preferably a NOAA Weather Radio. You can also download the NOAA Weather App on your phone!
- A toilet and sanitation kit: Since the power lines and plumbing system may be disrupted, you should consider an alternative to flushing your toilet. This toilet kit is amazing because it contains your #1 and #2 in a bucket with a sanitary solution to optimize your hygiene and prevent the spread of disease.
- A complete first aid kit: Since medical assistance may not be able to get to everyone immediately, make sure you have the basic supplies to take care of at least minor wounds. Remember that disruption to the city’s infrastructure is possible, so consider getting extra prescription medication in the event that pharmacies don’t get their regular deliveries of meds.
- Important documents: Keeping a digital copy of each of your documents on the Cloud is highly recommended because you don’t have the guarantee that you’ll be able to recover them from your home or take them with you in a moment’s notice.
I hope I didn’t I bury you in too much information. If you feel overwhelmed, however, I made a handy checklist that you can print and keep with your emergency kit. This checklist highlights important safety tips to remember before, during, and after landslides, as well as the top items you should keep in your preparedness bag.
- All emergencies cause a disruption in our communication methods, either because of broken or saturated telephone lines. Make sure you're aware of other uncommon communications that could help you get in touch with your loved ones after a disaster.
- Recovering from a disaster takes some time, but it can take much longer than expected if you don't have proof of your most important documents. Do you know which ones those are? Find out here!
Raise awareness on landslide preparedness!
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Spread the word about the importance of becoming prepared for landslides.
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What was the biggest landslide in the world? — USGS
What should I know about wildfires and debris flow? — USGS
Deadliest Landslides in Recorded History — World Atlas
Five Years Later - The OSO (SR 530) Landslide in Washington — USGS
11 Facts about Landslides — DoSomething
Mount St. Helens Eruption: Facts & Information — Live Science
Mt. St. Helens’ Victims Remembered — LA Times
What States Are Prone to Landslides — NBC News
Landslides - Where, When, and Why do They Occur? — Geology Cafe
Rising number of fatal landslides makes 2019 the worst year on record — The Watchers
New Software Can Predict Landslides Weeks Before They Happen — Smithsonian Magazine