Assessment of Bankline Shifting and Erosion-Deposition dynamics of Kangsabati River in Downstream of Mukutmanipur Dam, Rarh Bengal

Abstract

Bank erosion and channel shifting is an inherent natural process of river dynamics. This paper attempts to investigate the changes in the nature and extent of bank line shift and erosion-deposition dynamics along both the banks of Kansabati river in downstream of Mukutmanipur dam during the period 1921-2018. The shift of bank lines and amount of erosion-deposition along both the banks have been measured, analysed and mapped using Districts maps, Topographical Sheets of Survey of India and various multi-temporal Landsat imageries using various GIS techniques and tools as well as field investigation. Entire stretch of channel under investigation has been divided into 3 reaches and 25 GIS transects have been taken into consideration to assess the bank line shift. The result of the study reveals the differential shifting pattern of both left bank and right bank of Kangsabati river during the entire observation periods. The maximum shift of 519.81m (51.98m/year) along left bank at cross section-12 and 329.65m (32.97m/year) along the right bank at cross section – 18 were noted from second phase of observation 1978-1988. During the entire time frame of 1921-2018, net eroded area of 6.55 sq. km. and net accreted area of 32.16 sq. km were measured along the left and right banks respectively. As the middle and lower reach of the study area are severely prone to riverbank erosion and channel shifting during the annual peak monsoon. So, such a study is very much necessary to understand the regime of regional river dynamics.