Abstract
Abstract Brahmaputra River Basin (BRB), the largest contributor of sediment load in Ganges–Brahmaputra–Meghna delta, is highly vulnerable to future climate change. Several studies assessed the effects of climate change of BRB on river flow but an assessment on sediment load has not been conducted. Changes in sediment load in the future need to be assessed to control and manage sediment flows in large catchments properly. The present study focuses on developing a hydrological and sediment routing model of BRB using the HEC-HMS model to estimate future sediment load together with the flow for the RCP 8.5 climate scenario. Modified Universal Soil Loss Equation and Engelund Hansen method of HEC-HMS have been applied for the sediment transport of BRB. The model has been calibrated using daily runoff for the period 1983–1996 and validated for the period 1997–2010, respectively. The uncertainty in the percentage change in seasonal sediment load during the pre-monsoon season is higher than that of the monsoon season. However, the contribution of the sediment load of pre-monsoon is very much lower than the monsoon season. The percentage changes in mean annual sediment load compared to the baseline period for the 2020s, 2050s and 2080s are 34, 67 and 115%, respectively.
Highlights
Bangladesh, the lower riparian country of Ganges–Brahmaputra–Meghna (GBM) river basins, is highly vulnerable to flood, storm surge, cyclone, erosion and other natural disasters
For the period 1993–1996, the simulated sediment load from the model is about 379.1 Mt/year, which is close to the sediment load, i.e., 402 Mt/year, estimated by Delft Hydraulics (FAP )
A hydrological model which includes both surface runoff and sediment routing models has been developed for the Brahmaputra River Basin (BRB) using an open source-based model, HEC-HMS
Summary
Bangladesh, the lower riparian country of Ganges–Brahmaputra–Meghna (GBM) river basins, is highly vulnerable to flood, storm surge, cyclone, erosion and other natural disasters. Bangladesh contributes only a 7% area of 1.7 million km of GBM basins. Bangladesh encompasses a very small part of that large area, the amount of discharge and sediment flow from the upstream countries passed through Bangladesh towards the Bay of Bengal are relatively very high. The GBM river system is the third-largest freshwater outlet to the world’s oceans (Chowdhury & Ward ). The Brahmaputra River Basin (BRB) is the secondlargest basin of the GBM basins and carries the highest discharge and sediment load. Massive sediment loads yield from the Brahmaputra river every year which varies from 590 Mt/year (FAP ) to 792 Mt/year (Islam et al ) as estimated in several previous studies
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