Coastal Salinity and Water Management Practices in the Bengal Delta: A Critical Analysis to Inform Salinisation Risk Management Strategies in Asian Deltas

Salinisation within delta environments is a dynamic process governed by the interaction between coastal, fluvial and geomorphological systems. Increasingly, these have been modified through human activity and management practices, which lead to unintended problems associated with waterlogging and salt accumulation in soils and water resources. As a result of these issues, over 100 million people in the Ganges-Brahmaputra and other Asian deltas are negatively affected by a lack of freshwater availability and decreased crop yields. Rising sea levels, climate change, and population increase are all likely to exacerbate these problems. Using an iterative approach of literature review, we analyse the evolution of water management practices and policy and how these have influenced salinity within the delta, with a conceptual framework of understanding developed to guide risk management strategies. We find that management of coastal flooding and salinisation is hampered by socio-economic conditions and the dynamic hydro-morphology of the delta, which has increasingly been altered through diversion and abstraction of upstream flow. Whilst engineering solutions protect large areas from inundation, interruption of natural flood-dynamics also increases the potential impact from storm-surge and fluvio-tidal flooding. To limit salinity, policies based on salinisation science, as well as the implementation of adequately financed, multi-layered, integrated risk management plans at the local, regional, and river basin levels, are required. The promotion of stakeholder engagement should be encouraged to ensure local co-operation and effective implementation of policies. The mitigation of the multiple and cascading hazards associated with salinisation caused by anthropogenic activity, climate change and socio-economic development is crucial for the populations of delta regions across Asia.