LandslidesA Major Threat

What is a Landslide? A landslide is the movement of rock, debris or earth down a slope. They

result from the failure of the materials which make up the hill slope and are driven by the force of gravity. Landslides are known also as landslips, slumps or slope failure.

Landslides can be triggered by natural causes or by human activity. They range from a single boulder in a rock fall or topple to tens of millions of cubic meters of material in a debris flow.

Types of Landslides The term "landslide" describes a wide variety of processes that

result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. The materials may move by falling, toppling, sliding, spreading, or flowing.

They are:-1. Flow2. Slide3. Falls4. Topples

Flow Flows are generally a slurry mixture of water, soil,

rock and (or) debris that moves rapidly downslope. 

Slide Slides are the downslope movements of soil or rock

along a discrete or narrow failure surface

Falls and Topples Falls and topples are usually rapid, downward movement of

large pieces of rock or debris. Sometimes this is enough rock to cover a road or block a stream or river. 

The speed of the movement may range from very slow to rapid. The speed of the landslide will make an even more or less avoidable

and therefore, more or less risky. It is important to distinguish the different types of landslides to be

able to understand how to deal with each of them.

Causes of Landslides Gravity: Gravity works more effectively on steeper

slopes.

Rainfall—Prolonged or intense rainfall and rain-on-snow events can saturate soils and trigger landslides.

Earthquakes—Intense shaking during earthquakes can cause the ground to fail. 

Water-level changes—Rapid lowering of water levels can trigger landslides, especially along dams, coastlines, reservoirs, and rivers.

Human activities—Vegetation removal, mining, loading on a slope, excavation at the base of a slope, and leakage from pipes can all trigger landslides.

Geology—Easily weathered rock types and sandy or clay-rich soils are especially susceptible to landslides.

Precautions Educate yourself about your landslide risk. Seek out advisories and warnings during and after intense

rainfall events. Avoid living in locations that are hazardous. Don't assume that highways are safe. Listen for loud or unusual sounds. Keep away from landslide-prone areas.

During Landslides During a severe storm, stay alert and awake. Listen for unusual sounds that might indicate moving debris, such as

trees cracking or boulders knocking together. Listen to local news stations for warnings of heavy rainfall. Avoid river valleys and low-lying areas. Curl into a tight ball and protect your head if escape is not possible

After Landslides Stay away from the slide area. There may be danger of additional

slides. Watch for flooding, which may occur after a landslide or debris flow. Check for injured and trapped persons near the slide, without entering

the direct slide area.