Assessment of Future Flow of Hatirjheel- Begunbari Drainage System due to Climate Change

Sadia Afrin, Md. Maksimul Islam and Md. Mujibur Rahman

Dhaka, the capital of Bangladesh, has experienced water logging for last couple of years as the storm water drainage systems are often unable to manage peak runoff volume. Moreover, precipitation intensity and pattern are expected to be altered due to climate change and such changes are likely to lead to severe flooding in urban areas of Bangladesh. This study aims to assess the effect of climate change on flow of Hatirjheel- Begunbari Khal storm water drainage system as it is considered one of the major drainage channels of Dhaka city. As Hatirjheel works as a large storm water detention area and also a regulatory system, different scenerios are considered while assessing the future flow. The rational fromula was used to assess the flow instead of hydrologic model due to lack of observed flow data for calibration and validation. The study involves DEM based catchment delineation using GIS. The DEM was reconditioned prior to catchment delineation to create a channelization effect intended to mimic the existing storm sewer network of the city. A future land use scenario is considered based on the analysis of land use maps of three different time interval for determining future runoff coefficient. The peak rainfall intensity is obtained from the IDF curve of Dhaka city developed considering the future precipitation data of a climate model. Although Hatirjheel is found to be an effective retention and regulatory system to minimize the flow, result of this study shows an alarming increase in flow in future which might cause severe flooding in the surrounding area.