Question.
Why does the Kosi river bring such a huge quantity of sediments from the upper reaches?
(Chapter-3 Drainage System, Class 11 NCERT geography "India Physical Environment")
Answer.
The Kosi river brings a huge quantity of sediments from the upper reach due to the following reasons -
The sedimentary rocks of the Himalayas, the wide valley of the Kosi river in the Himalayas, and the heavy monsoon rains in the catchment area of the Kosi river are the main sources and causes of sediment in the river.
Sedimentary Rocks of Himalayas:
The entire Himalayan mountains are made up of sedimentary rocks which break easily and are loose materials. Due to this, the river receives a huge quantity of sediments.
The wide basin of the Kosi river in the Himalayan region.
The Kosi River is an antecedent river and has its source (Arun, the main tributary of the Kosi River) located north of Mount Everest. The Kosi River crosses all three ranges of the Himalayas (Greater Himalayas, Middle Himalayas, and Shivalik ranges).
There are seven major tributaries of the Kosi, which spread largely in the Himalayan region and collect sediments from the region.
Monsoon Rain:
The upper reaches of the Kosi river receive heavy rainfall during monsoon. Due to heavy rainfall in the mountainous plains of Nepal, huge quantities of sediments are generated.
Due to heavy sedimentation in the Kosi river, the channel of the river gets blocked by its own sediments, consequently, the river changes its course. For this reason, the Kosi river is called the sorrow of Bihar.
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