Disaster Survival

Landslide + Mudslide

Landslides and mudslides may be our most pyrotechnic disasters. The worst of them are like some big-budget action flick in which the special effects department pulls out all the stops: Whole blocks of houses slide down hills and plunge deep into the face of the earth. Water mains break, unleashing flooding. Power lines topple and crash into the floodwaters, touching off explosions and fire. Furthermore, these disasters sometimes strike with little warning, and are almost never covered by insurance. At least there are some important steps you can take to minimize your family's risk, and increase the chances that if such a blockbuster does open in your neighborhood you and yours will get out alive.

Special Equipment

  • Rain Gauge It's difficult to predict landslides with any great precision, but probably the best indicator is a large amount of rainfall that falls in a brief period of time. To keep track of the rate of precipitation in your neighborhood, you can pick up a rain gauge] for as little as $35 or $40. Look for one with an electronic monitor that records time as well. Whenever the rainfall exceeds three or four inches per day or a 1/4 inch per hour, the conditions are ripe for a landslide.

Landslide and Mudslide Insurance (Sic)

Although landslide insurance is technically available from certain select insurers, it's so expensive and difficult to collect on, it's rarely recommended. Your best bet is to buy flood insurance. And then just pray that if a slide strikes your community, it's classified as a mudslide (a sub-category of landslide with fewer rocks and uprooted trees but more mud) and that the mud contains a high enough percentage of water for the Federal Emergency Management Agency to rule that it also constitutes a "flood."

Landslide-Proofing Your House

When buying or building a house in landslide country, you really need to do your homework. Try to avoid buying or building on or at the base of a very steep slope. Hire a soils engineer to analyze the property, and thoroughly check out the neighborhood. The best communities have extensive networks of "V-ditches" and retaining walls to direct debris flows away from homes. There are also a handful of slide-proofing projects that individual homeowners can undertake. Just be sure before undertaking any of the following you consult a soils engineer first - not only for your own sake, but so you don't create more of a problem for your downhill neighbors.

Porous paving stones Ask your contractor or local building supplies store about this environmentally sensitive approach to limiting the kind of run-off that can contribute to landslides.

Deep-rooted trees and bushes The more you have on your property the better (without of course running afoul of good wildfire-proofing practices). And never remove without undertaking other measures to limit run-off.

Underground catchment pond In addition to making sure your property is properly graded so it slopes away from the house, you may want to talk to a contractor about having it drain into one of these mechanisms for collecting and gradually releasing run-off.

V-ditches and deflection walls These can be a major undertaking, running into the thousands of dollars. Walls need to be high, strong, and deeply anchored enough to withstand debris flows that could carry away your house. Still, if your house is situated on a high-risk slope, it's definitely an option worth considering.

Respect a natural drainage course If you have a stream or natural debris ditch running across your property, do NOT alter its course. You'll only increase the likelihood of it returning to its original path with a vengeance.

If a Realtor in landslide country ever tells you a house is on the "safe side" of the hill, you've got every reason to be skeptical. Especially after viewing this clip of Dr. Bob's interview with an unsuspecting victim of the 2005 Laguna Beach landslide.

Stay or Go?

Landslides often strike with a ferocity and suddenness that recalls an earthquake. Yet unlike earthquakes they usually come with at least some aboveground warning signs. In California, for example, residents have learned to go on full alert from the beginning of a El Nino cycle of particularly heavy rainfall until the end. The key is recognizing the signs and knowing when to get out of the way.

  • Whenever rainfall exceeds 3 or 4 inches per day or 1/4 inch per hour, consider evacuating.
  • But if such a deluge occurs and there's no slide right away, do NOT automatically assume you're in the clear. Sometimes, as in the case of the 2003 Laguna Beach Landslide featured in the Your Survival DVD, the actual event doesn't occur until weeks later. What happens is the precipitation gradually seeps down and loosens a lower strata of earth, and it's this lower strata that eventually breaks away, carrying everything above it with it.
  • If a night of extremely heavy rainfall is forecast, move anyone whose bedroom is located on a lower floor facing a hazardous slope into a different part of the house. In California alone, more than 100 people have died in landslides over the past 25 years, the majority of them trapped in lower-floor bedrooms.
  • Another common predictor of landslides is wildfires, or more precisely the debris left behind by wildfires which combines with heavy rains to trigger massive flows of ash, mud, and charred brush and trees. If there's recently been a wildfire up slope from you and heavy rains are predicted, get out now while you can.
  • Some of the other visual cues that a landslide or mudslide could be imminent include: leaning trees, fences, or poles; doors or windows sticking or jamming; cracks in plaster, tile, brick, paved areas, or foundations.
  • If you're ever asleep and you hear loud POPPING and CRACKING sounds, don't just pass it off on overly rambunctious raccoons. The popping could be from water pipes bursting in your walls and the cracking from your wood beams and supports being ripped apart by a slide.
  • Once a slide is underway, have everyone put his or shoes on and get out of the house and clear of the slide as quickly as possible. If you can, drive to safety, but be on alert for collapsing sections of roadway. And be especially mindful of falling power lines.