Prediction of Short-Term Morphological Change in Large Braided River Using 2D Numerical Model

摘要

Prediction of annual changes in braided-river morphology is important to assess the performance of river-training works and channel navigability. A two-dimensional (2D) depth-averaged numerical model was used for a 12-km-long reach of the Brahmaputra River in India. Major issues addressed in the modeling included approximation of boundary conditions, design of a flood hydrograph, and evaluation of river morphology. Simulated flow depth and velocity were calibrated with the observed data under bankfull discharge conditions, and predicted bed levels were validated with observed bed levels during low-flow conditions. The model predictions of thalweg shifting for two consecutive flood seasons agreed well with observed changes obtained from satellite imagery. The calibrated model was subsequently used to assess morphological changes in different groyne fields. The best groyne field was determined based on overall performance in scouring, deposition, channel alignment, and dredging volume.