Runoff modeling of the wadi systems for estimating flash flood and groundwater recharge potential in Southern Sinai, Egypt

Evaluating the likelihood of a flash flood as well as flood water resource is vital for establishing properly sustainable developments in arid environments. However, the high degree of spatial and temporal variability in hydrometeorological processes and the general lack of suitable data limit these efforts. In the present work, a runoff model, adopting the simple Soil Conservation Service method, was built for 13 ungauged catchments in Southern Sinai, Egypt. Runoff modeling was conducted as a function of the descriptive parameters of the catchments, and the maximum average rainfall occurred in 1 day in the period 1960-1990, designed according to a storm event recorded at the outlet of one of the studied catchments on the 2nd of November 1994. The catchments' descriptive parameters were extracted from available remote sensing data and field investigations. Land covers including road networks and 83 rock-soil types were also extracted from the maximum likelihood classification of the Landsat-7 ETM+ imagery. The catchments were then subdivided into 103 smaller subcatchments, which were then placed into different terrain types according to hydrologically relevant surface characteristics. Hydrologic characteristics and soil type(s) in the subcatchments were estimated during on-site visits. Morphometric parameters of the wadi catchments and the channel networks were derived from the analysis of the SRTM3 digital elevation model (DEM). Hydrographs were drawn and routed to the main catchment outlets based on appropriate wadi dimensions and roughness using the Muskingum's method. The runoff and infiltration volumes were quantified. The resulting models have been used to investigate the relative potential for flooding and the groundwater recharge in the catchments. Further, in order to determine specific sites with a high potential for flood risk and groundwater recharge, decision-ruled integrated analysis of the generated GIS layers describing relative stream power and wetness indices were applied. Due to the lack of flow data, the results of the hydrological models were validated against the DEM-derived relative stream power and the wetness indices as well as against field checks and available reports as an alternative. The results of this study could help to prioritize areas where flood control measures should be directed, as well as effectively augment management plans for the appropriate development of water resources.