Abstract. The study of flash flood hazard phenomenon and runoff potentialities are the major task of a hydrologists especially in arid and semi-arid regions. This paper presents a new approach to modeling flash floods in dryland catchments by the integration between physiographic features of the study basin, Geographic Information System (GIS) and Watershed Modelling System (WMS). Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) data was used to prepare a digital elevation model (DEM) with 30 m resolution and Geographical Information System (GIS) was used to evaluate the linear, areal and relief characteristics of Wadi El Azariq basin, East Sinai, Egypt. The qualitative and quantitative analysis of thirty eight morphometric parameters were estimated and interlinked to produce nine effective parameters for evaluation of the flash flood hazard in the study area. As a result of the sparse hydrologic information, the relation between rainfall and runoff was calculated depending on the morphometric information, GIS techniques, Watershed Modeling System (WMS) and Hydrologic Engineering Center-Hydrologic Modeling System software (HEC HMS). Based on the nine effective morphometric parameters that have a direct effect on flood prone area and control the hydrologic behavior of the basin, flash flood hazard of Wadi El Azariq sub-basins were identified and classified into two groups (High and low hazard degrees). Hydrographs for Wadi El Azariq basin were constructed with different return periods of maximum daily rain fall. The calculated volume of the total surface runoff ranges from 4.1 × 10⁶ m³ to 13.8 × 10⁶ m³ at return periods of 5 years and 100 year respectively based on the maximum daily rainfall events. This study draws specifics about the flash flood prone areas, planning rainwater harvesting and flood management approaches of Wadi El Azariq basin.