CHAPTER SEVEN

LANDSLIDES AND MUDSLIDES

Aerial view of the Philippines during a landslide. Credit: Pixabay.

Landslides don’t seem like they would occur often enough that you should even worry about preparation or survival. On average, between twenty-five and fifty people are reported killed by landslides in America, although the real numbers exceed that amount because many landslide and debris flow deaths are attributed to the catalyst such as earthquakes. In 1920, one hundred thousand people died in a massive landslide in China. You might remember that in 2014, forty-three people died in Oso, Washington (Mt. St. Helens) from a landslide, making it the deadliest in American history.

While the California landslides make the most headlines, landslides occur in almost every state and can cause significant damage. The states considered most vulnerable are Washington, Oregon, California, Alaska, and Hawaii. The term landslide describes downhill earth movements that can move slowly and cause damage gradually, or move rapidly, destroying property and taking lives suddenly and unexpectedly.

A landslide is a large mass of earth and rocks that suddenly slides down the side of a hill, slope, or mountain. You’ll also hear landslides referred to as debris flows, mudslides, mudflows, or debris avalanches. Landslides are dangerous because they happen in a flash, move at extremely high speeds, and they are able to travel long distances.

Landslides occur from human, structural, or geological forces but most landslides are caused by natural events, such as heavy rain, snowmelt, earthquakes, volcanic eruptions, erosion, change in ground water, and gravity. If the force down-slope exceeds the strength of the earth materials below, you get a landslide.

Human influences that cause landslides include mining, logging, irrigation, and excavation. Landslides are typically associated with periods of heavy rainfall or rapid snowmelt and tend to worsen the effects of flooding by adding debris. Areas of land that are degraded by fire are vulnerable to landslides. One important thing to know: Landslides typically happen in areas where they have happened before. So that means you need to learn about your area’s landslide risk.

Landslide problems can be caused by land mismanagement, particularly in mountain, canyon, and coastal regions. In areas burned by forest and brush fires, a lower threshold of precipitation may initiate landslides.

Impending landslide warning signs:

• Springs, seeps, or saturated ground in areas that have not typically been wet before.

Badger Gulch in Beavercreek, Idaho after wildfire and heavy rainfall. Credit: US Geological Survey, creativecommons.org licenses by 2.0, Wikimedia Commons.

• New cracks or unusual bulges in the ground, street pavements, or sidewalks.

• Soil moving away from foundations.

• Ancillary structures such as decks and patios tilting and/or moving relative to the main house.

• Tilting or cracking of concrete floors and foundations.

• Broken water lines and other underground utilities.

• Leaning telephone poles, trees, retaining walls, or fences.

• Offset fence lines.

• Sunken or down-dropped road beds.

• Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil content).

• Sudden decrease in creek water levels though rain is still falling or just recently stopped.

• Sticking doors and windows, and visible open spaces indicating jambs and frames out of plumb.

• A faint rumbling sound that increases in volume is noticeable as the landslide nears.

• Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.

Preparation

California homes after a damaging landslide. Credit: John Shea, FEMA Photo Library.

So what can you do to protect yourself and your property from a landslide?

If you haven’t built your home yet, research before you build your house. Has this area experienced landslides or debris flows in the past? Are there water drainage patterns where runoff converges and causes channels, natural indicators of landslides? Do you see erosion valleys? If you want to build near steep slopes or close to a mountain’s edge, your builder should do a ground assessment and provide necessary information about possible landslides.

If you have a house in place, assess your property’s landslide risk. There are various ways to do this—get in touch with local officials, local universities (geology), state geological surveys, natural resource departments and get a ground assessment of your property. Ask for information on landslides in your area, request specific information on areas vulnerable to landslides, and get a professional referral for a detailed site analysis of your property, and what you can do to correct the situation if possible.

Minimize home hazards:

• Plant ground cover on slopes.

• Build retaining walls.

• Build deflection walls in mudflow areas so the debris flow goes around your house (but don’t force it to a neighbor’s lawn or you’re responsible).

• Use flexible pipe fittings since they are more resistant to breakage so you avoid gas or water leaks.

• Bring in a professional to consult on preventative action.

Watch for clues: Are you on or near a steep slope? Close to the edge of a mountain? In a natural erosion zone? Do you see any patterns after rain where runoff water converges and forms heavy channels? Do you see any new changes in your landscape that are probably the result of drainage? Any land movement or small slides? Leaning trees? Are there new cracks that have appeared in the ground, your driveway, side of your foundation? Is your fence leaning more after rains? Have debris flows occurred in your area before? All of these could indicate that you are in danger of a possible landslide occurrence on your property.

Small slope landslide. Credit: Eddylandzaat, creativecommons.org licenses by-sa 3.0 nl deed.en, Wikimedia Commons.

No single indicator should alert you that landslides are possible or imminent but there are a collection of signs to watch for: Look for warping in your home or movement in the area near your home. Take note if your deck, patio, or concrete floors are tilting, pulling away from the building, or cracking. If your doors and windows are sticking, that might indicate warping. Broken water lines, roadbeds that seem to have sunken overnight, cracks in plaster or brick, outside walls that are pulling away, and widening cracks in pavement should all be causes for concerns. Do you have any underground utility lines that have broken? Any bulging ground that appears at the base of a slope? Any water breaking through the ground surface in new locations? Do you see any fences, retaining walls, utility poles, or trees tilting or moving? If you live where you could experience a landslide, keep eyes wide open and stay safe.

A devastating landslide in El Salvador. Credit: USGS.

If your area is vulnerable to landslides, talk to an insurance agent to see if your insurance covers landslide-related damage. Although landslide insurance is not usually available, some flood insurance policies cover damage from landslide flows. To begin preparing, you should build an emergency kit and make a family communications plan.

Buy a NOAA Radio and have it handy. The NOAA Weather Radio is an automated twenty-four-hour network of radio stations in the United States that broadcast advertisement-free weather information directly from a nearby National Weather Service office. If your area is receiving heavy rainfall, check the radio or television station for any landslide warnings or alerts. We recommend also downloading at least one emergency app for iPhone or Android since so many are now available for any disaster. There are several disaster alert apps so find the ones that work for you. Most include interactive maps, alerts, information, contacts and more. Facebook has a Safety Check-in feature that alerts all your friends and family who have already heard about the disaster in your area, that you are safe.

Power could be out or phone systems might be down, but you can use various apps that provide free IM and phone calling. You know how quickly apps come and go, how they are improved or even change names, so it doesn’t make sense to list them here when by the time the book comes out, the list would have changed.

Your family might be in different places when a landslide hits, so make sure everyone knows how to receive emergency alerts from local officials, by phone, television, radio, text, or phone app. More and more, emergency updates are provided by text.

Learn about local emergency response and evacuation plans. Landslide-prone areas typically have an emergency response team and evacuation plans. You might consider participating in local emergency response groups. Talk to everyone in your household about what to do if a landslide occurs. Create and practice an evacuation plan for your family and your business.

Additionally, assemble and maintain an emergency preparedness kit and create and practice an evacuation plan for your family and your business.

You will want to write down each family member’s phone number, email, all their social media names, doctors’ names and medical facilities, medicines, allergies, and school or workplace information. Take a photo with your phone just to have a backup. In the event of a landslide, you need to choose a place where the family will reunite. Pick a location in your neighborhood or at your church or a community center. If you worry about the landslide hitting your entire area, choose a meeting place somewhere central in your town. If you have pets, pick a pet-friendly area. Make sure everyone is aware of that location.

Compile contact information, landslide safety protocol, and your emergency meeting places on a single document. This is your emergency plan. Give every family member a copy and make sure they carry it with them at all times.

Your emergency kit

Each person in the house should have their own emergency kit in case you have to quickly evacuate.

• First-aid kit.

• Several-day supply of medicine.

• Flashlight and extra batteries. Hand-crank flashlight too.

• Battery-powered radio, and a hand-crank radio too.

• Three-day water supply (one gallon per person daily).

Road blocked from a rockslide. Credit: Pixabay.

• Three-day supply of easy-to-store, easy-to-prepare food that stores well such as dried or canned soups, protein bars, canned meat, beef jerky, powdered milk, canned vegetables and fruits, saltines, peanut butter, and hard candy.

• Personal hygiene items,

• Basic tool kit or at least a multi-use tool.

• Contact information of family and emergency departments.

• Ziploc bags for your mobile phones (not a bad idea to have an extra charger).

• Copies of important documents such as birth certificates, passports, insurance policies, proof of address, and the lease or deed to your home.

• Cash and change (ATMs might not be working or have cash left).

If you live in an area known for landslides, your area could be hit by a landslide and even if your house survives, you might be isolated or trapped, so it’s a good idea to have an emergency supply kit at your house with enough food and water to last three days. Landslides can interrupt services such as electricity, gas, water, phones, and sewage so plan accordingly. If your business is located in a landslide-prone area, it makes sense to prepare with the same vigor as you do with your home prep.

Cleanup in Puerto Rico after a landslide. Credit: Sgt. Alexis Vélez, Puerto Rico National Guard, Wikimedia Commons.

Survival

Conditions are prime for a landslide. Now what?

If you suspect imminent landslide danger, you’ve assessed the situation, and you are fairly sure a landslide is about to happen, contact your local fire, police, or public works department. Local officials are the best persons able to assess potential danger. Talk to your neighbors who might be in danger, too. They may not know of the potential threat and there may be some who need help evacuating. After you’ve done your due diligence, leave. Evacuate. Your best bet for your safety is to not be in the way of the landslide.

You might be at home, at work, or out of town but if you are in the middle of a severe storm and are in a landslide zone, pay attention. If an earthquake just occurred near your area and you are in the path of a possible landslide (streamside, slope, or mountain), pay attention.

After a landslide in Washington State. Credit: Savannah Brehmer, FEMA Photograph Library.

It’s raining heavily—a real gully washer—and you are concerned about a landslide. What do you do? During a severe storm, stay alert and awake. Many deaths from landslides occur while people are sleeping. Here’s your list of things to watch and listen for: turn on the NOAA radio and your local television station; unusual sounds, such as trees cracking or boulders knocking together; a low rumbling sound, which might indicate moving debris; collapsed pavement, new mud, falling rocks; roadside embankments caving in; earthquakes, which can induce or intensify the effects of landslides.

If you are with other people during the night and worrying about a possible landslide, coordinate your efforts and work together to keep each other awake. The alert parties should listen to the local news for updates on evacuation or impending landslide. If the weather is not too severe to travel, then why take the risk? You and your family should evacuate whether or not the emergency management team has ordered it.

Tragic debris flow after heavy rains and flooding in Vargas, Venezuela. Credit: John Shea, USGS. FEMA Photo Library.

Steps toward evacuation

• Listen to local and/or NOAA radio or watch local TV for warnings about intense rainfall or for information and instructions from local officials.

• Be aware that a trickle of mud or debris slowly moving or falling may precede a larger landslide.

• If you have a stream nearby, watch for any dramatic change in water level, up or down, clarity turning muddy. The landslide/mud debris could be occurring way upstream and you could see indicators well before it arrives.

• If you’ve decided it’s worth leaving your house, grab your emergency kits, and drive with a watchful eye. Watch for any tall structure that is unusually tilting or falling such as fences, trees or utility poles. As you look around, are there any big bald spots on hills or mountains around you, places where a landslide might have occurred already?

• As you drive, be alert. We’ve driven on mountain roads that became blocked by a mud/landslide or closed by collapsed pavement right before we got there. Try to avoid low-lying areas or river valleys.

• Bridges could be washed out.

• Do not cross flooding streams. Turn Around, Don’t Drown.

The Landslide is Happening

You’ve seen the landslide and mudslide videos before and know that folks will stand on the side of the flow watching it disbelievingly rush past them. Don’t do that. Move to higher ground immediately. Those folks are in danger of that ground being swept up in the forceful erosion of the slide.

Cracking trees and breaking boulders are a sign that a landslide is upon you. Run to high ground immediately.

If you get swept up in a landslide/mudslide, your potential for survival is small, some experts say less than 10 percent. Caught in the slurry of a slide makes swimming next to impossible and the quickness and force of the debris flow can knock you unconscious or injure your body. Your best bet is to either try to climb out, climb on top of something floating or something solid to grab ahold of. But it’s a small chance—so don’t get caught in a landslide!

Aftermath

The landslide has rushed past you or within a block or two of you. Perhaps you got to high ground but your house is demolished. Or maybe you avoided the catastrophe but are blocked in by debris. You might even be loading up the station wagon to leave the area. What should you do next? Avoid the area where the landslide occurred. Don’t be an onlooker unless you are part of a local emergency response team. Landslides may recur in the same location, so avoid this area and seek shelter.

After a landslide has passed, you should remain in a safe place until authorities have announced it is safe to leave. Listen to the radio for emergency updates. When you decide to go out, stay alert for flooding, debris, and damage to roads, utilities, and power lines.

Boulder sits at rest on side of the road after a dangerous slide. Credit: Barry Markowitz, FEMA Photo Library.

Avoid river valleys and other low areas. These areas are especially dangerous when landslides are imminent, so stay away.

Go to a public shelter. Your local community should have a designated public shelter. Go to the shelter if your home is unsafe or the authorities have called for an evacuation. To find the shelter closest to you, text SHELTER + your ZIP code to 43362 (4FEMA). For example, if your zip code is 56789, you would text SHELTER 56789.

Help neighbors who need special assistance. Infants, the disabled, and the elderly may experience extra difficulty in emergency situations. If it is safe to do so, help your neighbors with special needs. Remember that neighbors with large families may require additional assistance as well. If you are in a building, examine its foundation, chimney and surrounding land to determine if the structure is stable. If the area appears unsafe, leave immediately.

Small landslides occur frequently. Credit: Pixabay.

Some additional instructions:

• Stay away from the site. Flooding or additional slides may occur after a landslide or mudflow.

• Listen to the radio or TV for emergency information.

• Report broken utility lines to the appropriate authorities.

• 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, which may occur after a landslide or debris flow. Floods sometimes follow landslides and debris flows because they may both be started by the same event.

• Check for injured and trapped persons near the slide, without entering the direct slide area. Direct rescuers to their locations.

• Look for and 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.

• Check the building foundation, chimney, and surrounding land for damage. Damage to foundations, chimneys, or surrounding land may help you assess the safety of the area.

• 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 an expert for evaluating landslide hazards and designing corrective techniques to reduce future landslide risk.