Impacts of Dredging on Fluvial Geomorphology in the Jamuna River, Bangladesh

Md Mosiur Rahman,Moniruzzaman Khan Eusufzai,Md Munsur Rahman,Md Sazadul Hasan

doi:10.4236/gep.2021.96001

Md Mosiur Rahman, Moniruzzaman Khan Eusufzai + Show 2 more

Open Access

https://doi.org/10.4236/gep.2021.96001

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Abstract

Jamuna, a major braided river in Bangladesh, has an enormous hydrological impact on the surrounding areas and streams. Erosion and sedimentation in the Jamuna river cause a large flow fluctuation and floods round the year. Bangladesh Water Development Board has initiated a pilot capital dredging project in the Jamuna river in 2011-2012, aiming to guide the flow to reduce the risk of failure of the city area and right guide bundh of the Jamuna Bridge. This study explores the long-term role of dredging on river morphology us-ing erosion-sedimentation numerical modeling approaches. Primary data were employed in numerical models to estimate the erosion-sedimentation and compared outputs with the real-time cross-sectional variation at selected sections along the reach during 2012-2013. The analysis suggested that the rate of sedimentation is higher (60% to 80%), where the dredging alignment crosses through the existing sandbar/char. Moreover, a cross-section com-parison revealed that the channel near Sirajganj Hardpoint shifted towards the left (east) bank, and the channel within the study area developed very fast along the right (west) bank. However, satellite image analysis revealed that the major bankline shifting occurred from 2000 to 2010 and the channel shifting was observed from 2014 to 2018 along the reach, mostly, after the construction of some river training works. The variation of the channel per-sistence (40% - 100%) selected part of the study area in the channel inci-dence map, indicating the rapid dynamic behavior of the river morphology. This study showed a good agreement of measured data and simplified em-pirical relationships to predict the long-term morphodynamic behavior of the braided Jamuna river.

Highlights

Bangladesh, a major part of the Bengal basin which is the world’s largest delta (Fischer et al, 2017) formed by the alluvial deposits derived from the Himalayans and tectonic interactions and transported through the major rivers i.e., the Ganges, the Brahmaputra, and the Meghna (Sarker et al, 2011; Rogers & Overeem, 2017)
River dredging can influence the natural drivers of the channel morphology as well as the hydrodynamic process
The present study potentially investigated the effect of river dredging on the fluvial geomorphology of a reach near the Jamuna Bridge in the Jamuna River

Summary

Introduction

Bangladesh, a major part of the Bengal basin which is the world’s largest delta (Fischer et al, 2017) formed by the alluvial deposits derived from the Himalayans and tectonic interactions and transported through the major rivers i.e., the Ganges, the Brahmaputra, and the Meghna (Sarker et al, 2011; Rogers & Overeem, 2017). This delta has been considered as one of the most dynamic ones which attribute the highest sediment discharge and one of the three highest water discharges in the world. The overall width of the Jamuna River exhibits an increasing trend and there is a tendency of shifting westwards, especially at the upstream part of the Jamuna River (Team C-BJE, 1991; FAP 1, 1993; FAP 24, 1996)

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