Urban Drainage Study for Gopalganj Pourashava Considering Future Climate Change Impacts

This study focuses on an investigation, through hydraulic modelling, of the urban drainage systems in designing suitable drainage infrastructures for Gopalganj Pourashava by considering the possible impact of climate change on drainage. The daily rainfall data of Madaripur station from the Bangladesh Meteorological Department (BMD) for the base period of 1987–2016 has been analysed to prepare the IDF (Intensity–Duration–Frequency) curves for different return periods by fitting Extreme Value Type-1 (Gumbel) Distribution. Projected rainfall data has been obtained from 11 Regional Climate Models simulated considering high-end scenarios (RCP8.5) over the CORDEX South Asia domain for the near future (2017–2046). Design hyetographs were developed for 10 years 2-hour storm, which was later applied to generate runoff using the SWMM model. Water levels obtained from the frequency analysis at Atharobanki and the peak flow of Old Madhumati at Haridaspur for a 20-year return period are then used as boundary conditions for the model. Afterwards, natural canals which overtopped during the simulation have been identified. Finally, five alternative design conditions based on node flooding have been proposed to improve the urban drainage system. A comparison between the present and future drainage scenarios under different climate conditions has also been represented.