![]() 2019) and anthropogenic processes (dam constructions, river bank engineering, and land-use changes) (Surian and Rinaldi 2003 Wellmeyer et al. These fluvial dynamics are controlled by natural processes (discharge flow, sediment transport, debris flow, channel migration and floodplain erosion, and accretion) (Langat et al. ![]() ![]() Therefore, the geomorphological features are changing very rapidly in downstream Bangladesh despite its remarkably flat topography due to the complex upstream fluvial process (Takagi et al. In terms of mean annual discharge, the GBM river system is second only to the Amazon, and a major portion of this flow occurs in the summer season with immense monsoon rainfall, which causes widespread flooding in these drainage areas (Steckler et al. However, most of the rivers of Bangladesh (405 rivers including 57 transboundary rivers) are originated from the Himalayan and East Indian mountains and flow through Bangladesh into the Bay of Bengal (BWDB 2014 Dewan et al. Geographically, the major part of the GBM basin in Bangladesh is entirely lowland, which is surrounded by India on the west, the Myanmar on the east, Shillong Plateau on the north, and Bay of Bengal on the south (Steckler et al. The braided Jamuna, the meandering Ganges, the anastomosing upper Meghna, and the anabranching lower Meghna make the river planform more diverse and complicated (Sarker et al. The Meghna River (upper and lower Meghna) confluences with the Padma River at its upstream and downstream. The Ganges–Brahmaputra–Meghna (GBM) river system is the largest delta of the world, where the Brahmaputra is known as Jamuna River, and the confluence of Ganges and Jamuna River is known as Padma River (Sarker et al. ![]() This review will also develop a holistic understanding of fluvial geomorphic processes of the GBM River to the policymakers and may be helpful to improve the transboundary river basin management policies or strategies. Some future perspectives of geomorphic research in Bangladesh are then mentioned to understand better the complex geomorphological settings in the entire GBM watershed and to strengthen the existing research capacity. Although some studies on the fluvial dynamics and sediment dispersal in the upstream GBM river basin are present, the fluvial processes in the downstream domain of Bangladesh are not fully understood with a limited number of research with field-based approaches. Then, we discuss the fluvial dynamics and sediment transport of the GBM river system to address the knowledge gap in the context of deltaic plain land in Bangladesh, where upstream fluvial sedimentation processes impact the geomorphic connectivity from Himalayan to the Bay of Bengal. The review found that most of the geomorphic researches in Bangladesh are exploring landslide inventory and susceptibility mapping in hilly areas river channel or riverbank shifting, riverbank erosion and accretion in fluvial environments watershed morphometric analysis and geomorphic unit identification in plain land and coastline shifting or coastal erosion and accretion in coastal environments at a small scale. The previous studies are summarized at different geomorphic settings concerning hillslopes, fluvial plains, and coastal areas to provide clarity about the geomorphic processes linking erosion-prone upstream source areas to deposition-dominated downstream areas. The area locates in the downstream of the watershed system including Himalayan Mountains and highly connected with the upper basin morphodynamics, hydrology, and sediment flux. This article undertakes an overview of the geomorphological processes of the disaster-prone deltaic landscape of the Ganges–Brahmaputra–Meghna (GBM), particularly focusing on fluvial processes. However, our knowledge about such surface processes has relatively been limited in some areas in South Asia due likely to the lack of comprehensive studies of geomorphology and related fields. Geomorphological knowledge is critical in understanding watershed scale surface processes, including steep mountainous areas and flat lowlands, particularly if the mid- and downstream areas are densely populated and hazard assessments are highly required.
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