How Landslides Work


People and Landslides
This slope in the Cayaguas watershed in eastern Puerto Rico is an example of extreme deforestation and would be very susceptible to landslides. Robert Stallard, USGS. Public domain

Humans make landslides more likely through activities like deforestation, overgrazing, mining and road-building. Remember when we explained that vegetation acts like glue, holding the soil in place? These activities rob that glue from the land, increasing the probability of a landslide. For example, landslides are much more likely to occur in mountainous areas that have been clear-cut. We may have seen this unfold in 2014, when a landslide hit the Indian village of Malin, killing at least 151 people. Previously, thousands of trees in the neighboring hills had been chopped down to make room for new farms, construction projects and mining operations [source: Sarvade et al.].

By the way, you've probably seen signs warning of rock falls if you've ever driven through the mountains. The drop-offs with loosened soil on both sides of manmade roads require much less water to set off a landslide than natural drop-offs.

Although landslides cannot be avoided entirely, people can do several things to discourage them. Drainage pipes installed into slopes can carry away excess water, and impermeable membranes like plastic sheeting can prevent water from building up and dislodging the soil. In addition, setting up retaining walls at intervals will catch loose debris and keep it in place, while removing excess mass from the top of a slope could prevent the bottom from giving way. Reforestation is a good deterrent to landslides as well.

Perhaps the most important thing people can do to avoid the dangers of landslides is to avoid building in hazardous zones. Ideally, buildings shouldn't be placed on steep slopes or in drainage areas. But if people do build in areas like these that are susceptible to landslides, they should use protective measures. For instance, construction sites should use barriers to mitigate runoff and erosion [source: Kansas Geological Survey].

If you find yourself in an area where landslides are likely, be ready with an emergency evacuation plan. Be aware of any sudden rises or falls in water flow and listen for sounds that may signal moving debris or falling rocks. If you suspect landslide activity, you should evacuate immediately if it is safe to do so. Remember to be especially vigilant when driving, as roadside embankments are also hazardous.

Last editorial update on Jun 6, 2018 01:13:27 pm.

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