Spatially Explicit Debris Flow Assessment in Flash Flood-Prone Wadi Mikeimin, Egypt: A Remote Sensing and GIS Approach

Abstract

Flash floods in Egypt’s arid wadis are brief, high-energy events that mobilise large volumes of sediment and debris. This debris flow amplifies their destructive power and loads dams, barrages and water-diversion works with sediment, eroding storage capacity and structural integrity while endangering downstream settlements and roads. Earlier studies have modelled sedimentation largely in isolation. This study maps sediment generation, transfer and delivery together with the flash-flood hydrology of the same design event in Wadi Mikeimin (11.53 km²), a sub-basin of Wadi Watir in South Sinai draining toward Nuweiba City. Five techniques are combined in one spatially explicit framework: the Revised Universal Soil Loss Equation (RUSLE), converted to sediment yield through a sediment delivery ratio (SDR) based on the Index of Connectivity (IC); Geographic Information Systems (ArcGIS Pro); remote sensing (Sentinel-2 land cover); analysis of a 12.5 m Digital Elevation Model; and event-based hydrological modelling (curve-number losses and unit-hydrograph routing in WMS 9.1) of the 100-year design storm. Field visits supplied ground data.
For the 100-year event, peak discharge was 8.02 m³ s⁻¹ with a runoff volume of 107,505 m³. Maximum gross soil loss reached 6.25 t ha⁻¹ h⁻¹ and maximum sediment yield 5.99 t ha⁻¹ h⁻¹ (SDR up to 0.968), concentrated along the main channel network draining toward Nuweiba City rather than spread across the catchment. The WMS workflow was benchmarked against a published flood-hazard study of a 70.44 km² basin, reproducing its curve number, time to peak and discharge volume within 1.4%, 2.8% and 4.8% and its peak discharge within 10%, and the RUSLE-GIS approach has been corroborated against surveyed check-dam sediment volumes elsewhere in Wadi Watir (within 2.5% and 7.4%). Because no discharge or sediment record exists for Wadi Mikeimin itself, the results are best read as relative, spatially distributed indicators of erosion hazard rather than absolute values. They allow check dams, sediment traps and channel protection to be targeted at a small part of the catchment, giving designers of mega hydraulic structures a quantified, spatially explicit basis. The workflow relies on openly available data and is recommended for comparable watersheds.