Processes of channel migration of Kundil river in Sadiya, Assam, India.

Channel migration is common in alluvial channels, but the rate of migration and processes involved are varied. The Kundil River is an important tributary of river Lohit, flowing through the alluvial plains of Sadiya in the easternmost part of Assam, India. This paper attempts to investigate the rate, extent and the processes of channel migration for the period 1945–2014. Topographical maps and satellite imageries of different years (1976 to 2014) are used for the study. ERDAS Imagine 9.1 and Arc GIS 9.3 software are used for processing these spatial data. It has been found that there are significant changes in the river course during this period. The bank line shifting of the river has been determined separately for the periods 1945–1988, 1988–2014 and 1945–2014 with fifteen cross sections at an interval of approximately 3 kms. Maximum bank line shifting is found to be 1.88 km (1945–1988). However, the migration is not unidirectional all throughout the channel. The processes involved in lateral shift of the river channel can be grouped into three categories: 1. alteration of flow direction due to cut-off, 2. widening of the channel in response to bar development, 3. progressive shifting of meander bends