Earth observation data-based assessment of the impacts of June 2024 flooding in the Sylhet division of Bangladesh

Abstract

The Sylhet division, located in the northeastern part of Bangladesh, experienced severe flooding in June 2024, forcing thousands to seek shelter. The flooding occurred in two phases: the first following Cyclone Remal, which made landfall in Bangladesh on May 26, 2024, and the second by mid-June. This study aimed to estimate the extent of inundation, the population and buildings affected, and the damage to crops caused by the flood. It utilized Sentinel-1 (A & B) microwave and Sentinel-2 (A & B) optical data, population data from WorldPoP and Bangladesh Bureau of Statistics (2023a) and building data from Open Buildings. Image processing and GIS techniques were applied to extract and analyze information obtained from the satellite data. The study reveals that approximately 66% of the Sylhet division was inundated as of June 19, 2024. The flooding affected around 6.25 million people and exposed about 607,000 buildings. Regarding agricultural impacts, about 93% of crops planted during the Boro season of 2024 had already been harvested before the flooding. However, flood damage occurred on approximately 14,700 ​ha of remaining cropland. As the flooding occurred at the onset of the monsoon season rather than during the pre-monsoon period, the extent of crop damage was relatively lower. Nevertheless, major cities like Sylhet and Sunamganj were inundated, severely affecting large populations.