GUWAHATI, July 7 � Embankments are making the Assam rivers erratic. Noted geologist Prof Bhagawat Pran Duarah of Gauhati University (GU) has made this assertion. A similar assertion was made also by Chief Minister Tarun Gogoi a few days back.
Moreover, Prof Duarah said, embankments are making the rivers carry away the finer, fertile part of the soil far away and to deposit the coarse materials within their channels. �Thus, we are deprived of the loamy soil and once the embankments fail, the coarse, infertile materials enter the countrysides and make the fertile land unproductive,� he said.
Embankments were proposed as temporary structures in the 1950s with an aim at providing immediate relief from the havoc of flood.
Six decades have now elapsed since then. But, these structures are still retained due to various factors. These include � lack of proper research; failure of the authorities to focus on the need to regulate silt and water discharge characteristics of the rivers and channels; their failure also to visualize the fact that embankments are raising the riverbeds, among others.
Perhaps, the authorities in the initial days thought that embankments would increase hydraulic energy to scour the riverbed deeper and increase the river channels� capacities. However, in Assam, the slopes of the rivers, particularly those of the Brahmaputra, are very gentle. This hinders such scouring activities.
The Himalayan rivers, after rushing down through the steep slopes, enter the plains and face a sudden drop in their gradients incapacitating them in carrying away all the sediments they bring from the hills. They, therefore, deposit the same in their lower reaches. Only with sufficiently low sediment yields from the catchments, embankments can be successful.
�We need to channelise the multi-channel (braided) Brahmaputra, on activating its mid-channel and making it navigable. Navigability can make the river stick to one channel and thus stop its eroding activities. It also needs to get its lateral channels de-activated, as these channels are responsible for erosion,� said Prof Duarah.
