Assessing the impacts of land use-land cover changes on direct surface runoff: a remote sensing approach in Khulna City

The increased risks of storm flood occurrence in large cities are the resultants of land use changes due to rapid urbanization. This study examines the influence of land-use changes in Khulna City Corporation (KCC) area on surface runoff over a period of 14 years, from 2005 to 2020. Land use-land cover maps for 2005, 2010, 2015, and 2020 were created employing Support Vector Machine (SVM) based supervised image classification using time-series satellite data, and the surface runoff was determined using SCS-CN model. The major land-use change drivers of surface runoff were determined through a correlation analysis. Surface runoff was observed to follow a similar trend in impervious urban areas, which rose by 5.44% from 2005 to 2020 (17.00 mm average runoff depth increment) and the opposite trend was found in vegetation land cover, which declined by 13.34% in areal extent throughout the study period. In comparison with other types of land use, surface runoff changes were most significantly associated with the changes in urban impervious areas and vegetation LULC class. In fast-growing cities across the world, and especially in developing nations, the results of this study may serve as a guide for urban storm flood management and urban planning efforts.