Flash flood is one of the most important natural hazards all over the world. It is very dangerous because of its effect on people's lives and can lead to death. So we must be aware of the flash flood by studying the factors that affect it and predict it. In this paper, hydrological parameters that affect flash floods in arid or semi-arid areas are studied. The study area is Wadi Al-Baroud El-Abiad which is located to the northwest of Safaga city on the red sea coast that is frequently subjected to a severe flash flood. Parameters affecting floods are considered i.e. meteorological (climatic), morphological, and geological factors. Climatic data are analyzed to reach the design storm values for different return periods by knowing the annual rainfall values of the study area by using rainfall data from a rain gauge station near the area. In this research, the mean monthly rainfall values of Safaga meteorological station from 1994 to 2018 are used and the annual maximum values of rainfall rates are extracted from it. Digital elevation model (DEM) and digital terrain data of the catchment are obtained from the USGS EathExplorer website and inserted into WMS and ArcGIS software. To obtain the hydrological characteristics such as unit hydrograph, concentration-time, delay time, and storage coefficient, the land use and soil type in the study area must first be determined by the geomorphological and geological study. SCS and curve number methods are used in estimating the soil type and land use of the basin. Many software and tools are used in data analysis and watershed delineation among them, GIS, WMS, SURFER, HYFRAN, GOOGLE EARTH. From this study, watershed morphological characteristics, flood quantity, and flow hydrograph at Wadi Al-Baroud El-Abiad dam are estimated for different rainfall intensity, duration, and return periods. Moreover, the storage capacity of the dam reservoir at different rainfall intensity, duration and return periods is estimated and the time required for storage water to evaporate and infiltrate into the subsurface soil is identified. The results of this research can help the developer, planners, and decisionmakers for flood management in arid areas.