Two‐dimensional morphological model for prediction of erosion of a reach of Brahmaputra River using MIKE 21C software with hydrodynamics and river morphology modules

Abstract

Understanding the morphological dynamics in highly braided rivers, like the Brahmaputra, is crucial for effective river management. To gain this understanding, data is essential for mathematical modeling, enabling short and medium‐term predictions of morphological changes. Our study focused on the Palasbari‐Gumi stretch of the Brahmaputra River, utilizing a two‐dimensional morphological model (MIKE‐21C). Our objectives were to predict erosion patterns, plan protective measures, and anticipate morphological changes. Author conducted multiple models runs under various hydrological scenarios. For coarse sand, the model projected an annual sediment load of 257 Mt/year in 2021, with a bankfull discharge of 314 Mt/year. Historical records noted 400 Mt/year sediment load in the Brahmaputra. Importantly, our model's predictions closely matched empirical data, especially regarding ADCP velocities, design flood levels, and annual sediment load. Peak model velocities deviated by less than 9% from ADCP measurements, predominantly within acceptable limits. Predicted flood levels for bankfull discharge conditions achieved nearly 96% accuracy at the Gumi site. This study highlights the role of predictive modeling in guiding river training measures, especially in dynamic braided river systems like the Brahmaputra, over a two‐3 year horizon.