Combined aeromagnetic, GIS, and remote sensing evaluation of flash-flood susceptibility and groundwater potential in an arid environment: Wadi Marwani, Western Saudi Arabia

Introduction Groundwater is the primary dependable freshwater source in the arid coastal catchments of western Saudi Arabia, where natural recharge is limited and occurs mainly through episodic rainfall and flash‐flood infiltration along wadi systems. This study assesses groundwater potential in the Wadi Marwani basin (≈2,347 km 2 ), a major tributary of the Khulais system southeast of Rabigh, by integrating multi‐source remote sensing, GIS, and aeromagnetic data. Methods Lithology was mapped from Sentinel‐2 imagery using support vector machine (SVM) classification, while structural fabrics were constrained using Sentinel‐1C SAR lineaments and aeromagnetic structural analysis. Terrain attributes (e.g., elevation, slope, drainage and flow indices, topographic wetness, and ruggedness) derived from a 30 m digital elevation model (DEM), together with NDVI, soil moisture, rainfall, and 10 m land‐cover data, characterized the surface conditions that control infiltration and storage. Aeromagnetic data were reduced to the pole, upward continued, and enhanced using the modified Elliott function (MEF) filter and Center for Exploration Targeting (CET) grid analysis. Source Parameter Imaging (SPI) was then applied to estimate relative depth to magnetic basement. Results Surface and magnetic lineaments consistently define a dominant N–S to NNW–SSE trend with subsidiary NW–SE and NE–SW sets that remain coherent at depth, reflecting reactivated Pan–African structures. A magnetically subdued, elongate basement depression along the central wadi axis, widening westwards, coincides with high lineament density and thick Quaternary alluvium, indicating favorable conditions for groundwater accumulation. The integrated groundwater potential map divides the basin into five classes; comparison with existing wells yields an AUC of 0.789, indicating acceptable to good predictive skill. Discussion The most promising zones lie along the central wadi corridor and the western alluvial plain. The integrated workflow is readily transferable to other basement‐controlled arid catchments.