Numerical Model for Bank Erosion in the Brahmaputra River

Abstract

A method is proposed to predict bank erosion and sand bar migration in river reaches where suspended sediment transport is dominant. The method focuses on the influence of the lateral bed slope on the erosion and deposition rate of suspended sediment, as well as on the profile of lateral bedload transport, assuming that geometric similarity holds in the bank region. In the proposed model, the erosion and deposition rate can be evaluated using either the bed shear stress at a reference location or the average bed shear stress in the bank region. In order to simulate bank erosion and associated bank shifting with a depth-integrated-base treatment, stretchable grids were added to the conventional coarse grid system near the bank. The proposed method, including the bank erosion model, is applied to the lower reach of the Brahmaputra River, which is ∼90 km long and ∼12.50 km wide. The computed results on bank shifting, sand bar migration, and sediment transport rates are compared with data obtained from field investigations and remote sensing. These results suggest that the proposed method is applicable for predicting sediment issues in river reaches dominated by suspended sediment.

How dynamic is the Brahmaputra? Understanding the process–form–vegetation interactions for hierarchies of energy dissipation

“…Such extreme non‐uniform nature of process–form interactions has enabled the river system to dissipate the fluvial energy at different scales. The previous studies on the Brahmaputra river have focused on flow–sediment variability (Fischer et al, 2017; Goswami, 1985; Karmaker & Dutta, 2015), morphological dynamics, and ecological responses through numerical modelling (Biswas et al, 2016; Karmaker & Dutta, 2016; Surabuddin Mondal et al, 2013), field investigations (Gul et al, 2018; Karmaker & Dutta, 2013), laboratory experiments (Chembolu & Dutta, 2018; Khan et al, 2021) and geo‐spatial techniques (Akhtar et al, 2011; Dubey et al, 2014; Sarma, 2005). The synthesis of these literatures has established the energy expenditure can be targeted towards a single (or multiple) fluvial processes.…”