Topographic Runoff Accumulation and Potential Waterlogging Mapping in Arid Suburban Plains Using TWI: A Case Study of Suluq and Jardina, Southern Benghazi, Libya

الملخص

This research investigates topographic runoff accumulation and potential waterlogging susceptibility across, low relief suburban plains of Suluq and Jardina in southern Benghazi, Libya. By integrating USGS Digital Elevation Models(DEM), D8 flow routing algorithms, and Topographic Wetness Index (TWI) mapping with OpenStreetMap infrastructure inventories, a practical geospatial framework was established to couple terrain morphology directly with urban risk evaluation. The empirical findings indicate that favorable macro topographic drainage conditions generally prevail, with the vast majority of the landscape situated within low TWI categories. Nevertheless, subtle micro topographic depressions generate critical localized pooling hazards. Specifically, the combined High and Very High runoff accumulation zones total area of 318.75 ha in Suluq (in the High and Very High class) and 70.61 ha in Jardina (in the High and Very High class). These severe tiers directly intersect a combined total of 120 vulnerable structures in western Suluq (91 in High and 29 in Very High) and 11 structural units in central western Jardina (7 in High and 4 in Very High). By explicitly isolating these topographic accumulation nodes, the applied methodology provides municipal engineers with empirical metrics to evaluate surface water pooling potential, noting that the index reflects terrain driven saturation rather than hydrodynamic flood depth modeling.