Strengthening the resilience of Egypt’s canal-drain system to flash floods: an examination based on a recorded extreme discharge event

Egypt has an arid climate, yet it remains vulnerable to sudden extreme rainfall events, as shown by the Dragon Storm of March 2020. That storm raised water levels in canals and drains and threatened to flood canal embankments and pumping stations. Studies on the impact of such events on stormwater management are scarce and rarely linked to the Nile irrigation and drainage system. Irrigation canal-drain systems are vital assets for managing stormwater, but they often lack the adaptability to cope with intense and frequent events. This study proposes an adaptive hydraulic framework that uses the existing irrigation canal-drain network as an integrated stormwater management system to enhance flood resilience. The Giza Canal and El-Masanda Drain were selected as a representative case study because of their strategic hydraulic connectivity and operational importance. A comprehensive field investigation, including hydrographic surveys, flow discharge, and water level measurements, was conducted to develop a one-dimensional hydrodynamic model (SOBEK-1D). The model was calibrated using field measurements, achieving calibration errors below 1%, confirming its suitability for evaluating alternative flood mitigation strategies. Four scenarios were evaluated under an extreme storm-water discharge of 41.50 m 3 /s to investigate the hydraulic response of the canal-drain system. These scenarios included the existing operational condition, alternative overflow channel configurations, and drain rehabilitation through dredging. The simulation results showed that constructing an overflow channel between the Giza Canal and El-Masanda Drain substantially improved the hydraulic performance of the system by efficiently diverting excess storm-water from the irrigation canal to the drainage network. The selected configuration consisted of a 10-m-wide overflow channel combined with dredging the downstream reach of El-Masanda Drain to its design bed level. This integrated solution achieved the highest hydraulic efficiency by maximizing the storm-water diversion capacity, maintaining stable water levels throughout the system, reducing flow velocities within the drainage network, and significantly improving the overall hydraulic resilience of the canal-drain system under extreme hydrological conditions.