Assessing flooding extent and potential exposure to river pollution from urbanizing peripheral rivers within Greater Dhaka watershed

Abstract

Greater Dhaka area is home to large industrial clusters that are driving economic growth and the poverty reduction efforts of Bangladesh. These clusters are located around peripheral rivers- Turag, Buriganga, Dhaleswari, Balu, Shitalakhya, Bangshi, and Tongi-Khal, which are important for water transport, environment, and eco-systems where flooding of floodplains in monsoon is an integral part. The economic growth with minimal environmental regulations had led to severe degradation of the rivers and floodplains environment affecting livelihood, health and well-being of the people. Monsoon time exposure to polluted water is yet to be studied and addressed scientifically. This study looked into the water quality and flooding situation of Greater Dhaka for two successive monsoons through extensive river sampling coupled with estimation of flooded area and exposed population through use of remote sensing tools. Sentinel 1’s Synthetic Aperture Radar (SAR) images are used for flood mapping considering cost-effectiveness and its advantages for data scarce regions. The estimated exposed population to flooding was over 668 thousand in 2019 and over one million in 2020 where the water quality ranged from highly polluted to moderately polluted. These point to a need for taking monsoon time exposure seriously in policy making process and design appropriate interventions.