Tuesday, August 4, 2009

An article from 1998 meant for a photograph of 2009

Landslides are a part of the Himalaya environment because the slopes are weak and are made up of friable rocks. If the slopes were thickly forested, a major landslide would occur once in 20 to 30 years. With deforestation becoming the order of the day, minor landslides are occurring with ever increasing frequency. In 1984, a study conducted in the Himalaya revealed that more landslides took place in the deforested area than in the forested areas. The study found that 148 landslides took place on slopes where the tree cover was less than 40 per cent and 118 landslides took place where the tree cover was more than 60 per cent. Seismic movements are constantly taking place in the region. On an average about 200 earth-quakes of smaller magnitude occur every year in the hills of UP.

Going by the geological clock, the Himalaya is a "young" mountain range, and is prone to natural disasters. Experts also say that they are one of the most erosion prone ranges. Intense rainstorms and earthquakes make these mountains prone to frequent landslides. But it is intense rainfall that usually triggers landslides.
Prolonged downpour often reactivates old landslides. "The natural absence of vegetation in the higher reaches of the catchment areas also contributes to frequent landslides," says an expert. Apart from bringing down large quantities of sediments, landslides become a major cause for devastating floods because they block the narrow gorges. They are normally marked by a sudden change in the gradient of a tributary stream, constriction at the point of confluence and weak geological conditions in the catchment of the tributary. The formation of landslide dams is a common sight in the Himalaya.

Large scale deforestation and faulty farming practices have also led to soil erosion, according to local people. Says V Sharma, department of geology, Delhi University; "It is not for the first time that these landslides arc occurring. This time it has attracted attention due to the large scale of deaths and destruction". "Human activities need to be controlled since the region is prone to earthquakes. The government must plan development activities to check landslides," he adds. Ironically, the debris generated is thrown down the slopes, which in turn devours vegetation and even fields. Experts say that about 40,000 to 80,000 cubic metre of debris have to be removed to construct a road I km long. Moreover, 550 cubic metre of debris have to be removed every year to maintain the road.

The increase in human activities along the slopes has changed the existing land use pattern. Experts say that the change in the cultivation patterns is another factor for landslides. A large number of people have shifted to terrace farming. Terrace farming requires vast tracts of denuded land - and also lot of water. The crop pattern has also changed. Villagers now fall prey to the less soil-binding crops such as rice instead of millets, more suited to this area. Local crops like millets and maize have taken a back seat while commercial crops and water intensive crops like paddy are grown.This makes the hills unstable. Earlier, forests would have protected the strength of the soil, but due to excessive deforestation, the protective cover has been drastically reduced. This has resulted in the creation of large number of rivulets in the hilly region.

Source - Down to Earth (14Sep1998)

Photo credit : Suman Tamang (Darjeeling)

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