Question

The states and areas that are vulnerable to floods by the river brahmaputra

Answer 1

The Brahmaputra river experiences severe floods between June and September every year. This causes extensive devastation in the Assam valley as well as to the adjoining nation of Bangladesh.

The fragile hills in the Brahmaputra basin are very prone to major landslides. This is further aggravated by wide-ranging deforestation, mining of dolomite, limestone and coal, rampant construction of embankments and roads and cutting of hill slopes. The top soil is loosened and washed away during the rains. The spate of dam construction (168 hydroelectric dams) in Arunachal Pradesh for generating hydropower is also leading to adverse consequences during floods.

The banks of these rivers are prone to erosion. The river and its tributaries are braided and change their course every now and then. They do so mainly because of the enormous amount of sediments they carry down the steep hill slopes, which they deposit in the riverbed downstream. The south bank of the river especially upstream of Dibrugarh, where the river enters the plains from the hills is more prone to erosion than the north bank. The channels get filled up, new courses develop in the subsequent monsoon and the earlier ones are abandoned. This area is a part of the Himalayas, which is a young mountain range that is still rising. A major part of region falls within a sensitive seismic zone. This makes the region prone to earthquakes thus aggravating the problem further. The bed of many rivers like Brahmaputra, Dibang, Subansiri etc. were raised by as much as 22 cm following the earthquake of 1950. The beds of several swamps that acted as reservoirs of excess water too got raised. This rise of the bed reduced the volume of water; the river channels, lakes and swamps could carry lesser thereby choking them and increasing the chances of floods.