Characterization of the March 13th 2020 flash flood in the Eastern Sahara and recommendations for unconventional protection measures in arid deserts

Climate change increases the reoccurrence of torrential rains in the Sharan-Arabian desert leading to unprecedented flash floods. The study characterizes the March 13, 2020 event that hit the Eastern Desert (ED) of Egypt and proposes unconventional protection measures using Wadi An-Nu’amiyyah basin as a test site. Supported by topographic and geological maps, remote sensing and field data, the study applies the Soil Conservation Service–Curve Number method (SCS-CN) and Manning equation. Findings showed that 67% of the rainfall occurred between 11 am and 2 pm on March 12th. The total time of discharge was 22 h with three discharge peaks of 96, 92.1 and 85.6 m3/s. The current protection includes concrete culverts (120 m3/s) beneath the Eastern Military road and the artificial flash flood channel (AFFC) (48.07 m3/s). However, the AFFC is not sufficient to accommodate the readily increasing flash floods, yet the close proximity of urban areas impedes the efforts to increase its capacity. Moreover, denudation and tectonic processes have led to the development of very wide wadis (> 400 m) thus challenging the construction of—dams. Instead, the study suggests establishing two retention reservoirs along/near active channels through enlarging the abandoned open pits for quarrying of raw building materials with a total capacity of 5.5 million m3. Under forecasted increase in flash floods in the ED, a large-scale open quarrying along/near active channels should be encouraged as an unconventional measure for flash flood protection in the ED and similar arid areas.