An assessment on the nature of channel migration of River Diana of the sub-Himalayan West Bengal using field and GIS techniques

Abstract

Lateral movement of river channel within its valley with time is a universal phenomenon. Various processes of fluvio-geomorphological environment such as rapid valley fill deposition due to very low channel gradient and resultant migration of active channel, bank failure and bankline migration, frequent occurrence of floods, capturing of lower courses of the tributaries by the trunk streams, and abandonment of tracks and avulsion are the most prominent factors behind channel dynamics in the sub-Himalayan part of West Bengal. Additionally, human interventions in the form of engineering constructions (bridges, flood embankments, etc.), tea plantation, mining and quarrying, and agricultural encroachment have emerged as another dominant issue which is pulverizing the ways of natural channel adjustment as well as also the channel behaviors. Both these processes are carrying significant messages of immense vulnerability for the study area known for its geomorphological instabilities. The dynamics of channel adjustment in terms of lateral migration can be lucidly illustrated through the application of modern tools of geoinformatics, i.e., the techniques of remote sensing and geographic information system (GIS) which is widely capable of detecting as well as representing the changes that took place over space and time. A meticulous endeavor has been made to assess the channel dynamics of the Diana River of this concerned region for an 85-year spanning period to unveil the nature of channel migration in terms of changes in historical bankline and centerline positions and alterations in meander geometries through numeric and graphical methods coupled with field observations to define the overall zone of channel migration for three subsequent reaches of the Diana River.