REMOTE SENSING BASED STUDY OF RIVER AVULSION OF BRAHMAPUTRA NEAR DIBRUGARH

Abstract

The Brahmaputra River is known for tremendous morphological changes over the years. The huge sediment load of the Brahmaputra River is mainly responsible for its changing morphology. In the past various studies have been conducted to understand the morphological changes like meandering, braiding etc. of the Brahmaputra River. But no or little attention has been given to the avulsion phenomenon. Therefore, in the present study avulsion of the Lohit and Dibang Rivers, tributaries of the Brahmaputra River, has been emphasized. The multi-temporal satellite data for the years 1990, 1997, 2000 and 2002 of IRS 1A, LISS I and ' IRS IC/ID, LISS III has been used for the observation of morphological changes. The avulsion of these rivers had taken place on upstream of Dibru-Saikhowa Reserve Forest, near Dholla Township in Tinsukia district of Assam. It has been observed from the study that during the 7 years (1995 to 2002) almost entire discharge of Lohit and Dibang River has transferred to the Dibru River through Dangori River, a tributary of the Dibru River. From the results it is indicated that the width of avulsed channel increased upto 2 to 3 times in a period of 5 years. The Dibru-Saikhowa Reserve Forest has lost its appreciable area in a period of only 5 years doe to the erosion along the banks, at the mouth and confluence of the avulsed channel with the main Brahmaputra River. Various river training measures have been taken by Govt. of Assam to tackle this serious problem of avulsion. After observing the scenario after the implementation of the river training works it has been found that RCC porcupines have been proved very effective in diverting the flow of Dibang and Lohit River to their original courses