Soil, Water, and Settlements: Understanding Flood Patterns in Aweil East and South, South Sudan

This study presents an integrated geospatial and hydrological assessment of flood patterns in Aweil East and South, located in Northern Bahr el Ghazal, South Sudan. Using HEC-RAS v6.6 Rain-on-Grid modeling, the research simulates rainfall-induced runoff across low-gradient catchments characterized by subsistence agriculture, grasslands, and seasonal wetlands. High-resolution datasets including the FABDEM v1.2 bare-earth elevation model and ESA World Cover land use classification were used to delineate watershed boundaries, estimate surface roughness, and calculate runoff volumes. Rainfall frequency analysis over a 110-year period was applied to determine return periods and hazard thresholds. A weighted Curve Number of 87.2 was derived from land cover proportions, enabling accurate runoff estimation using the SCS method. Results show that even frequent rainfall events with 1–2 year return periods can generate significant flood hazards due to minimal elevation change and poorly defined drainage channels. Flood hazard categories were evaluated using depth-velocity criteria from the Australian Rainfall and Runoff Guidelines, highlighting risks to settlements and infrastructure. The findings offer a robust framework for flood risk mapping, climate resilience planning, and disaster preparedness in vulnerable agro-pastoralist communities.