Mapping Flood Inundation over the Nile River Basin using Hydrological Modeling and Satellite Remote Sensing: Example from the 2020 Record-Breaking Flooding in Sudan

The Nile River has recently witnessed a heavy and continuous rainfall inside Sudan leading to a devastating flood. Owing to the extremely flooding event in 2020 (the highest in 100 years), thousands of people in 17 states (out of 18 states in Sudan) were affected during the rainy season period from July to September. Such detrimental impacts were significantly pronounced in Khartoum State, Sudans capital city where the main tributaries of the Nile river; the White Nile and the Blue Nile meet. Therefore, understanding the dynamics of flooding events in Sudan and in particular Khartoum State, is crucial to mitigate damages and losses from flooding events. In our study, a rainfall runoff-inundation (RRI) model is applied to simulate the streamflow and flood inundation using remote sensing data over the Blue Nile basin. Our results show a reasonable agreement between the observed and the simulated streamflow at both daily and monthly scales, e.g., NSE= 0.73 and R2 =0.86 for daily simulations. Building upon the RRI model, we simulated the flood inundation area during the rainy season of 2020. We compared the inundation area from the RRI model to satellite-based estimates using Sentinel-1, Sentinel-2, Landsat-8 and MODIS. The RRI model and satellite-based methods produce comparable flood inundation maps over the Blue Nile, and thus provide a robust tool to guide the future flood mitigation measures in the Nile River basin.