The present study aimed to analyze spatiotemporal changes in land use and land cover (LULC) within the Mananga Watershed from 2010 to 2020, and to model and project their impacts on flooding dynamics within the watershed from 2020 to 2050. Among the 11 identified LULC classes, brushlands/shrubs have the largest coverage, followed by perennial crops, annual crops, and built-up areas. An increasing trend in built-up areas indicates more exposed bare surfaces, leading to elevated surface runoff and higher flooding potential. The study identified 36 distinct LULC change patterns, with built-up areas, brushlands/shrubs, perennial crops, and annual crops remaining largely unchanged. Notably, closed forests were entirely converted to annual cropland, built-up areas, and brushlands/shrubs, while most open forests transitioned to brushlands/shrubs. Wooded grasslands, crucial for wildlife habitats, were almost completely converted to brushlands/shrubs. The simulation of LULC impacts on the watershed's flood susceptibility from 2020 to 2050 reveals significant trends. Urbanization, reflected by a decrease in annual crop areas and an increase in built-up areas, correlates with higher runoff and reduced infiltration, thereby increasing flood risks. Additionally, reductions in open forests influence runoff dynamics. The projected increase in runoff by 2050 underscores the exacerbation of flood risks due to urbanization and decreased vegetative cover. These results emphasize the necessity for strategic land management and urban planning to mitigate future flood risks and ensure the sustainable management of the Mananga Watershed.