· Forest degradation
· Road construction
· River and stream erosion
In layman's terms, the failure of snow-covered slopes is called a snow avalanche. It takes place in areas where there is a rapid accumulation of a huge mass of snow. The snow may fail or begin to slide downhill at a very fast pace due to the increase in stress. This increase in stress can be due to many reasons - - wind drifting, heavy snowfall in a short span of time, blasting, seismic activity or even thunder.
In the high mountain peaks of the world like Everest, Lhotse, and Nuptse avalanches occur frequently and they provide a spectacle for the visitors. But these avalanches do not really affect human lives. It is the avanlaches that occur near human settlements that are feared most, especially in the barren cold desert regions.
In the cold deserts, avalanches cause widespread loss to the natural and human environment. They are also responsible for changes in land form conditions as snow slides tend to scour the mountainside, particularly when being accompanied by rock fragments.
Let us take the example of Kalpa, in the Kinnaur Himalayas of India. Kalpa, the old headquarters of Kinnaur district, was under a constant threat of avalanches in winter and this was one of the reasons for shifting the headquarters to Peo.
Villages are known to have been wiped out by avalanches. In 1838, Tunda village in Ladakh was completely destroyed by an avalanche, leaving many people dead.
Avalanches also block the flow of rivers and streams, thereby creating temporary dams. When these dams fill up, hell breaks loose in the form of flash floods that may wash away human life and property. In recent memory, avalanches wrecked havoc in the Pin Valley of Spiti, India, in 1978.
Large amounts of debris are carried by avalanches, which are left in freshly scoured gullies when the snow melts, to be washed away to rivers and stream by the snow-melt waters. Avalanches are also a constant threat to forests and pastures. They destroy valuable forest produce and lay an assortment of debris over good alpine pastures. Trees wherever they grow may be broken at about breast height due to the excessive force of the on-rushing snow. It is common to come across large tracts of avalanche-affected forests and pastures near the snowline. Young saplings are the most prone to damage by avalanche as they offer the least resistance to the mass of on-rushing snow.
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