Allogenic and autogenic impact on morphodynamics of a tropical river on the Himalayan frontal plain, India.

This work intends to understand the spatial variation of channel morphological adjustment over 30 years (1987–2017). This region lacks an understanding of local variation in structural setup and its relative impact on channel morphological development as well as the direct control of channel hydrology in shaping the channel morphology. Besides measuring the reach-specific morphodynamics, this study is also engaged in understanding the impact of the allogenic processes (tectonics and gradient) and their local variations along with the response of autogenic processes and its reflection on channel morphological adjustment. Reach-specific channel morphodynamics is measured through training the observed dataset using the autoregressive integrated moving average model where the root mean squared error found at the best-fit model scenario was considered as the measure of relative variations in the morphometric variables. Channel reaches under direct structural control are morphologically most unstable where the faultline-induced possible sedimentation controls the fluvio-geomorphic processes intensively. The nature of morphological adjustment varies on different surface gradients but local variations in structural setup determine its spatial nature. The temporal variations of channel morphological parameters are responsive to peak discharge strength coupled with controls of channel gradient. Moreover, channel morphological change to hydrological variation is more sensitive on the piedmont surface compared to low gradient plain. This research contributes towards a close understanding of reach-specific channel morphological behaviour which is important while predicting its future and implementation of any river management strategies. [ABSTRACT FROM AUTHOR]