Spatiotemporal variability of channel and bar morphodynamics in the Gorai-Madhumati River, Bangladesh using remote sensi
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RESEARCH ARTICLE
Spatiotemporal variability of channel and bar morphodynamics in the Gorai-Madhumati River, Bangladesh using remote sensing and GIS techniques Md. Yousuf GAZI (✉)1, Farhad HOSSAIN1, Sumiya SADEAK1, Md. Mahin UDDIN2 1 Department of Geology, University of Dhaka, Dhaka-1000, Bangladesh 2 Department of Geography and Environment, University of Dhaka, Dhaka-1000, Bangladesh
© Higher Education Press 2020
Abstract Bangladesh is a riparian country that is crisscrossed by the many tributaries and distributaries of the mighty Ganges, Brahmaputra, and Meghna river systems. Gorai-Madhumati, a distributary of the Ganges River is an example where morphological development of the river is associated with frequent channel shifting within the catchment area. The main objective of this research is to quantify the extent of channel migration, erosion-accretion, river width, sinuosity, and charland morpho-dynamics from 1972 to 2018 using geospatial techniques combined with satellite images and hydrological data. The study also addressed the impacts of Farakka Barrage construction in India on the shifting, flow behavior, and siltation of GoraiMadhumati River. The study shows that bar surface areas have abnormally increased in both segments after 1975 due to the construction of Farakka Barrage. Water flow in the Gorai-Madhumati has dropped remarkably in the downstream and instigated huge sedimentation in this region. Analysis of the time series satellite images revealed that the morphology of the river channel experienced huge changes simultaneously with the changes in the seasonal flow and sedimentation all over the study period. Migration trend has frequently shifted and taken place in the NW and NE direction in the observed sections of the river. Throughout the study period, total amount of accretion was greater than the net percentage of erosion on both banks of the river. River discharge, bar accretion, and erosion history show that the Gorai-Madhumati River will no longer exist with the present flowing condition without attention and proper river management. Keywords channel migration, erosion-accretion, morphodynamics, geospatial techniques, Gorai-Madhumati, Bangladesh Received February 11, 2020; accepted July 15, 2020 E-mail: [email protected]
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Introduction
Bangladesh is a riparian basin that is traversed by numerous tributaries and distributaries of mighty Ganges, Brahmaputra, and Meghna river systems. River bank erosion and accretion with concurrent channel migration is a very common phenomenon and ongoing dynamic process in this country (Islam et al., 2014). River Bank shifting is often related to the event where one bank is forming and the opposite bank is eroding. Observing the spatiotemporal morphodynamics of a river is very crucial to comprehend the river behavior (Mondal et al., 2020). Bangladesh loses a plenty of fertile land and sandbanks every year due to riverbank erosion and flooding. Severe flood flows of the river water grind down the bank during the monsoon period whereas in the winter, sandbanks
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