Flood susceptibility modeling based on morphometric parameters in Upper Awash River basin, Ethiopia using geospatial techniques

The hydrological response, such as direct surface runoff, is linked to the characteristics of the watershed. Evaluation and knowledge of geomorphometric parameters in relation to floods and the identification of specific flood-prone sites in the basin are critical for mitigation measures. Despite advancements in geospatial tools, the utilization of geospatial data in many river basins prone to flooding and erosion is minimal. Morphometric aspects: linear, areal, and relief analysis of the Upper Awash River basin were performed in four subbasins to better understand the hydrological signatures behaviour. The topographic wetness index (TWI) and topographic position index (TPI) were also used to determine the extent of inundation. The aggregated parameters revealed that SB-1 is highly susceptible to flooding, SB-3 and SB-4 are moderately susceptible, and SB-2 is low. However, based on the geomorphologic instantaneous unit hydrograph, SB-2 and SB-4 demonstrated rapid response and a high flood generating potential. The degree of susceptibility was determined by incorporating the TWI and TPI through overlay analysis. Overall, the Upper Awash River basin accounts for 23%, 42%, and 36% of the total bay has been classified as high, medium, and low flood-prone, respectively. According to the study, topographic indices (TWI and TPI) are critical attributes that show specific flood potential areas and inundation extents in addition to morphometric parameter-based flood susceptibility analysis. The analysis provided input for holistic water and soil erosion management by providing the hydrological behaviour of the stream, geomorphological characteristics, basin responsiveness, and stream power to flood potential and denudation characteristics in the subbasins.