This past year has seen several landslides claim lives and shut down roads, in particular the horrible slide that took some 42 lives in Oso, Washington. These are extremely powerful disasters and can start rather suddenly, turning an otherwise picturesque mountainside into a rolling wall of earth and debris that can bury houses. Even if the immediate area around you is safe from the primary effects of a landslide, you may still have to deal with disruptions, road blockage, and river flooding that may result so it is in your best interest to understand where and how these can occur. Let’s find out!
Different types of slides
A landslide is the generic term for a variety of different kinds of “earth slides” that involve debris, soil, rocks and other materials being moved. There are actually a few different types of slides that differ in speed, damage, and likelihood of occurrence depending on the geographical and human factors involved. Here are a few of the most common:
- Mudflows. Also called “debris flows”, these are among the most drastic in changing the landscape. Usually caused by extreme saturation of mud and other materials in a steep slope, a mudflow can easily sweep rocks, trees and other debris in with the slurry of water and earth. This can smash through anti-landslide barriers and even carry people off since this type of slide rather closely resembles a flash flood in many circumstances. Once the slide has stopped the earth can solidify, sometimes filling in depressions with foot upon foot of new earth. Lakes and rivers can be filled in, causing flooding as the water is displaced. It can also park a small mountain of debris between trapped survivors and rescuers, making it a very good idea to have a few days worth of supplies on hand.
- Debris slides. Unlike a debris flow, a debris slides tend to be much faster and result from very steep slopes with lots of heavily soaked vegetation. These are capable of moving far, far beyond their point of origin owing to their extreme speed coming down a hill. These are very likely to kill most people that they come into contact with, simply owing to the sheer ferocity of rapidly moving chunks of rocks and trees that mix into the earth. Like mudflows, a debris slide can also destroy or block up roads, bridges and dams that get in their way, slowing rescue efforts. If large rocks and boulders are part of a debris slide, they may also be termed “rock slides”.
- Earth Flow. These typically involve finely grained sand, clay or other soils and can be either very fast moving or a slow bulging creep depending on the circumstances. In either case they are also caused by water, though in this case the saturation directly determines the speed of the flow more than the slope will. This is because the weight of the water is largely what moves the earth flow, and once it starts to dry the flow will slow to a halt. These can carry debris, but they tend to carry them on top of the flow rather than burying them as a mudflow will. Particularly rapid earthflows are deadly just as much as any other slide or flow, and they can carry large boulders or other debris right into people and buildings.
As you may have noticed, landslides are generally caused by three factors: a slope, sufficient rain or moisture, and loosened earth or other debris. Almost any mountainside has at least the potential for a landslide, though the presence of thick vegetation and the use of certain walls and other supporting structures can reduce the odds of such an event occurring. In the end, if you live in an area where a landslide is possible you will simply have to prepare for the eventuality as it is impossible to completely remove the risk.
What to do during a landslide
First off, always pay attention so that you will be able to avoid it in the first place. Rumbling noises, sudden streams of muddy water or loose, moving gravel should indicate that it is time to leave. Try to have a bugout bag ready so that your evacuation will go smoothly even if your home is destroyed or buried.
Assuming you are unable to get away beforehand, do your best to stay out of the flow. Like water the slides tend to follow the path of least resistance so roads that are in the bottoms of valleys and the like will be extremely hazardous. If you can get onto higher ground away from the flooding soil, do so, but know that trees and other debris could still be pushed with a great deal of force up an incline and could hit you.
In the end the best thing to do is to be out before a slide occurs, since it is very difficult to survive the sheer volume of falling materials involved in most landslides.
Landslides block rivers and cause flooding, destroy bridges and roads to block travel, and can break gas and electrical lines, making entire areas extremely dangerous. For those of you who live downstream from mountain rivers, flooding can be a major concern miles away from where the slide ended, so if a slide is occurring in your state you will want to watch for warnings and other vital information.
In all, the only way to be truly prepared for a landslide is to not be there once it begins. Supplies, gear and skills are useful but the sudden and powerful nature of these disasters makes any kind of survival iffy at best. Be sure you’re ready for this disaster…but know the risks involved in living near areas where landslides are possible, too.
Do you have any landslides that occur in your area? Have you prepared for them? Let us know in the comments below!