Geomorphic change in the Ganges–Brahmaputra–Meghna delta

Abstract

Over 70% of large deltas are under threat from rising sea levels, subsidence and anthropogenic interferences, including the Ganges-Brahmaputra-Meghna (GBM) delta, the Earth's largest delta system. The dynamic geomorphology of this delta is often overlooked in assessments of its vulnerability; consequently, development plans and previous management investments have been undermined by unanticipated geomorphic responses. In this Review, we describe GBM delta dynamics, examining these changes through the Drivers-Pressures-States-Impacts-Responses framework. Since the early Holocene, the GBM delta has evolved in response to a combination of tectonics, geology, changing river discharge and sea level rise, but the dynamics observed today are driven by a complex interplay of anthropogenic interferences and natural background processes. Contemporary geomorphic changes such as shoreline change, channel migration, sedimentation and subsidence can increase flooding and erosion, impacting biodiversity and local livelihoods.Continued human disturbances to the GBM delta, such as curtailing sediment supplies, modifying channels and changing land use, could have a more direct influence on the future geomorphic balance than anthropogenic climate change. In order to contribute to long-term delta sustainability, adaptation responses must therefore be informed by an understanding of geomorphic dynamics, requiring increased research on future delta dynamics at centennial timescales.

Storm surge hazard over Bengal delta: a probabilistic–deterministic modelling approach

“…The diverse range of extreme water level should also nourish future research directions to better understand the dynamics of extreme water level over the continuum of the Bengal delta. Evidently, continued future research is necessary under the threat of climate change with unavoidable sea level rise (Oppenheimer et al, 2019;IPCC, 2022), land subsidence and morphological changes (Paszkowski et al, 2021), and potential increase in the frequency of devastating cyclones under future climate (Emanuel, 2021). We acknowledge the potential compounding effect of rainfall during the storm on inland flooding which is not considered in our analysis.…”

Development of Storm Surge Inundation Model and Database for Enhanced Climate Services in Bangladesh

“…Coastal polders are one of the major infrastructures in Bangladesh for protecting the communities from storm surge and coastal flooding. While construction of these polders in 1960s initially resulted in increased agricultural productivity, they later posed several environmental and social concerns related to prolonged waterlogging, reduced sedimentation in the low floodplain, and increased riverbed siltation in the poldered areas (Rezaie et al, 2013(Rezaie et al, , 2019Paszkowski et al, 2021). The polder design considers a conventional return period approach which does not address the risk and costing associated with storm surge, which can alter the required polder heights at places (Zaman and Mondal, 2020).…”

Supplementary material to "Sediment transport in Indian rivers high enough to impact satellite gravimetry"

“…The Meghna River is often considered in combination with the Ganges and Brahmaputra rivers. These three rivers confluence in Bangladesh (Figure 1) to form the Ganges-Brahmaputhra-Meghna Delta, the Earth's largest and most populous delta system (Paszkowski et al, 2021). However, in contrast to the Ganges and Brahmaputra rivers, which are rich in sediment, the Meghna river originates in the Indian Naga Hills at less than 2, 000 m elevation and carries comparatively little sediment of (6 − 12) • 10 9 kg yr −1 (Rahman et al, 2018).…”