Evaluation of Structural Measures for Flash Flood Mitigation in Wadi Abadi Region of Egypt.

Wadis, an Arabic term referring to a wadi, in the Eastern Desert of Egypt have undergone rapid unsustainable development in areas vulnerable to flash flooding and water scarcity. To reduce the risk of damage and loss of life from flash floods to a wadi's new residents, the priority is to develop mitigation strategies with distributed (watershed scale) or concentrated (localized) mitigation structures to promote sustainable development. The focus of this study is to develop a new approach that will help in assessing various flood mitigation scenarios in Wadi Abadi in the Eastern Desert of Egypt. The proposed approach considers the limited data availability in the wadi system and utilizes spatial analysis and an in-house developed distributed hydrological model, Hydrological River Basin Environmental Assessment Model (Hydro-BEAM), upgraded with a reservoir routing module. Sensitivity analysis of the key Hydro-BEAM model parameters indicated that the most significant parameters controlling the wadi flood peaks are soil thickness and porosity, runoff coefficient, subsurface layer outlet coefficient, and channel roughness. Digital Elevation Model (DEM) data and satellite imagery were utilized to propose the locations and derive design characteristics of the mitigation structures. The mitigation strategies evaluated in this study resulted in a peak flood reduction percentage of 90% and 86% for the distributed and concentrated dam scenarios, respectively. The results show that a group of distributed dams could outperform a single concentrated dam when flood mitigation and water resources management aspects are considered in the wadi region, where the distributed dams scenario has 600% more protected area and 21% more reservoir volume than the concentrated scenario (i.e., use of one dam). However, the concentrated dam scenario may have advantages due to the cost of construction and operations. The proposed approach can assess the flood risk reduction due to different mitigation measures and provide strategies for development and planning in wadi regions. [ABSTRACT FROM AUTHOR]