Impact of Extreme Rainfall and Land Use Land Cover Change on Flood Hazards in Sylhet District of Bangladesh

Flooding is one of the most common natural disasters throughout the world, leading to the loss of lives and properties. Bangladesh is one of the highly vulnerable countries to climate change-induced flood hazards, due to its location in the Ganges-Brahmaputra-Meghna (GBM) deltaic floodplains with high population exposure. The agro-economically important, haor-dominated Sylhet district in the north-eastern region of Bangladesh has faced devastating floods in recent decades. However, assessing the combined impact of climate change-induced extreme rainfall and anthropogenic forcings-induced land use land cover (LULC) change on the flood-susceptible Sylhet district remains unknown. In this study, the generalized extreme value distribution in rainfall data was adopted to assess the contribution of extreme rainwater to flood hazards. It shows that most of the flood events were enhanced by the excessive rainwater from the upstream. The occurrence of extreme rainfall in the hilly areas of Meghalaya and its rapid runoff over a short period is the main reason for the devastating flood hazards in Sylhet district. The impact of LULC change was assessed using Landsat ETM+ satellite image analysis by adopting remote sensing and Geographic Information System (GIS)-based analytical techniques. The evaluation of the LULC change shows a rapid increase in built-up area during the study period of 2010–2022. The remarkable increase was observed in unplanned development of settlement areas, road networks, and construction of infrastructure, most of which have replaced water bodies. The unplanned increase of built-up area and a significant decrease of water bodies highly affect the proper drainage of the rainwater, which enhances the flood hazards. The people’s perception analysis shows that the increase of human economic activities and the adoption of unplanned development projects are the main reasons for rainfall-induced flood hazards. A significant number of people perceive that the monitoring of extreme rainfall, better management of development projects, and proper drainage are important measures to reduce the combined impact of extreme rainfall and LULC change on increasing flood hazards in the Sylhet district of Bangladesh.