Flash floods and groundwater evaluation for the non-gauged dryland catchment using remote sensing, GIS and DC resistivity data: A case study from the Eastern Desert of Egypt

The coastal and alluvial areas of the Red Sea Mountains are mainly being developed for resorts and tourism activities. Given the development of occasional flash floods in the central part of the Red Sea area can be of destructive consequences to the various anthropogenic activities; thus the quantitative and qualitative assessments of the hydrological parameters and groundwater occurrence are presented. As a case study, Wadi Isl at the Red Sea coast has been hydrogeologically analyzed using an integrative approach of remote sensing, GIS and direct current resistivity (DCR) tools. The time area-zones have been estimated using and Manning's equation into the spatial analyses routines embedded within the ArcGIS. In this study, a synthetic effective rainfall of 10 mm has been applied to compute the spatially distributed runoff hydrograph. The estimated total runoff volume is approximately 8 million cubic meters, and the peak discharge rate is estimated to 163 cubic meters per second, which can be destructive to the main infrastructures in the flash flood pathways. Then, the 2D-electrical resistivity tomography (2D-ERT) surveys have been carried out at various localities along the main wadi course to explore the lateral and vertical variation of alluvium thickness and the saturated zones. Notably, the groundwater occurrence is contained in the structurally controlled graben. Therefore, the study has recommended the construction a main barrier at a natural deep gorge of the main outlet in order to fully control the flash floods and to enhance the potential recharge to the underlying alluvium aquifer. The present integrative approach of both surface and subsurface data is definitely needed to maximize the flash flood benefits.