Think and answer:"The river Brahmaputra is the main cause of floods in Assam."How? Elaborate your answer with suitable examples.
Answers
At the crux is the very nature of the river Brahmaputra —dynamic and unstable. Its 580,000 sq km basin spreads over four countries: China, India, Bangladesh and Bhutan, with diverse environments.
In terms of sediment yield, two spots along the Brahmaputa’s course were at second and third places in 2008, behind the Yellow River whose annual sediment yield is 1,403 tonnes per sq km.
The Brahmaputra’s annual sediment yield was 1,128 tonnes per sq km at Bahadurabad of Bangladesh, and 804 tonnes per sq km at Pandu of Guwahati.
How do these characteristics of the river relate to flooding?
The vast amount of sediment comes from Tibet, where the river originates. “That region is cold, arid and lacks plantation. Glaciers melt, soil erodes and all of it results in a highly sedimented river.
By the time the river enters Assam — a state comprising primarily floodplains surrounded by hills on all sides — it deposits vast amounts of this silt, leading to erosion and floods.
As the river comes from a high slope to a flat plain, its velocity decreases suddenly and this results in the river unloading the sediment.
Again, because of the earthquake-prone nature of the region, the river has not been able to acquire a stable character.
Following the devastating earthquake of 1950, the level of the Brahmaputra rose by two metres in Dibrugarh area in eastern Assam.
Man made factors
Besides these natural factors are the man-made ones — habitation, deforestation, population growth in catchment areas (including in China) — which lead to higher sedimentation.
For example, the sediment deposition itself creates temporary sandbars or river islands.
It is common for people to settle in such places, which restricts the space the river has to flow. When rainfall is heavy, it combines with all these factors and leads to destructive floods. This happens very frequently.