Effect of longitudinal disconnection on in-stream bar dynamics: A study at selected road–Stream crossings of ajay river

Abstract

Over the 1970–2010 periods, the effect of longitudinal disconnection was prominent around the road–stream crossings on the Ajay River of West Bengal. The crossings endorse significant changes on in-stream fluvial processes, for example, in-stream bar dynamics, thalweg wandering, and channel avulsion. The imbalanced condition of sediment delivery has induced a change of 87 and 61 % of the braiding index in the upstream and downstream reaches of a bridge-crossing at sample site I, respectively. The temporal aggradation of the river channel has been significantly illustrated from bar stability analysed using the Normalized Difference Vegetation Index (NDVI), flow height observation, and field verification. Unequal distribution of channel sinuosity, migration rate, and avulsion make a threat to the bridge stability associated with severe bank erosion.