Flash-flood hydrology and aquifer-recharge in Wadi Umm Sidr, Eastern Desert, Egypt

Abstract Rapid urbanization and irrigation agriculture along the hyperarid Red Sea coastal plain in Egypt are dependent on freshwater supply from coastal aquifers. The aquifers are recharged by flash-floods from catchments (wadis) in the Eastern Desert, but large floods also cause infrastructure damage and deaths. Flood management strategies require knowledge of flood magnitude-frequency relationships, but in this regard quantitative data are lacking. Here, we reconstruct the peak discharge of a large flash-flood in 2016 using field measurements and flood discharge modelling along Wadi Umm Sidr, ~50 km west of Hurghada. In addition, we estimated the total flood volume, the flood duration, the infiltration rate and the transmission losses. Results are consistent with the few published determinations for large floods across the wider Levant. Field survey of recent floods (and palaeofloods) is a robust means to develop regionally applicable magnitude-frequency relationships. We close with some recommendations regarding flood protection of the Red Sea coastal infrastructure.