Geospatial hazard modeling for the delineation of flash flood-prone zones in Wadi Dahab basin, Egypt

Abstract

This study delineated flash flood hazard zones leading to vast destruction to infrastructure, property, and loss of life. An integrated approach using remote sensing and geographic information systems was applied to reveal flash flood-prone zones. The study approach evaluated topographic, geologic, and hydrologic factors holistically to assess these hazard zones. The morphometric characteristics of Wadi Dahab sub-basins were supported by topographic, geologic, and hydrologic information. Data from Shuttle Radar Terrain Mission and Operational Land Imager imagery were analyzed to characterize hydrological morphometrics, lithology, soil types, and land use. A Natural Resources Conservation Service model was selected to calculate runoff depth at ungauged watersheds. A spatially distributed unit hydrograph was adopted to create the flow time and runoff velocity. The Flashflood Hazard Model was developed by spatial integration of all contributing factors. An analytical hierarchy process was adopted for the logic ranking of the effective factors. The flash flood hazard map classifies Wadi Dahab basin into five relative hazard zones: very high, high, moderate, low, and very low. The highly hazardous zones are distributed at the downstream of Wadi Dahab basin corresponding to steep topography and Precambrian rocks. The hazard map was validated using the flash flood markers defined from field observations.