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The 4th IPCC report highlights the increased vulnerability of the coastal areas from floods due to sea-level rise (SLR). The existing coastal flood control structures in Bangladesh are not adequate to adapt these changes and new measures are urgently necessary. It is important to determine the impacts of SLR on flooding to analyse the performance of the existing structures and corresponding impact to plan for suitable adaptation and mitigation measures to reduce the impacts of floods on coastal zone. The study aims to develop a comprehensive understanding of the possible effects of SLR on floods in the coastal zone of Bangladesh. A hydrodynamic model, which is a combination of surface and river parts, was utilized for flood simulation. The tool was applied under a range of future scenarios, and results indicate both spatial variability of risk and changes in flood characteristics between now and under SLR. Estimated impact on population, infrastructure and transportation is also exposed. These types of impact estimation would be of value to flood plain management authorities to minimize the socio-economic impact.

One potential impact of a global warming and rise in sea level would be an increase in the salinity of coastal zones, which would potentially threaten drinking water and aquatic ecosystems. There is a need to be better prepared to respond and adapt to these changes. This report examines the potential impacts of accelerated sea level rise on salinity in the South West region of Bangladesh. The study aims at determining the sensitivity of river salinity to upstream discharge and downstream sea level. To do that, the minimum upstream flow will be determined to protect the salinity intrusion from sea level rise. A one dimensional river salinity transport model has been developed and coupled with an existing surface and river flow model. The model has been proved to be robust with calibration and verification against observed data. The model outputs indicate a significant change of river salinity in the coastal zone. The results also indicate that a considerable advance in seawater intrusion can be expected in the coastal aquifer if current rates of sea level rise continue. The topography of the area is flat and gently sloping towards the Bay of Bengal. The consequences of salinity intrusion in the coastal area especially in the South West region of Bangladesh would be significant on many sectors like land fertility, agriculture, availability of fresh water, existence of the Sundarban forest etc. Pond culture in the coastal area will be affected by intrusion of salt water into ponds, unless embankments are made around them. Shrimp culture in the coastal area is a lucrative business. Increase in salinity is likely to jeopardize the shrimp culture.