Modeling of rainfall-runoff and flooding using HEC-HMS model through GIS in an arid environment: A case study in the Safaga Valley basin, West Safaga city, Egypt

Abstract

Reliable forecasts of rainfall-runoff are crucial for reducing flood risks. Furthermore, the risk of such floods can be prevented and reduced with the use of appropriate modeling. So, accurate runoff calculation is regarded as necessary for rainfall-runoff modeling. However, the lack of runoff measurements in watersheds is considered a big obstacle in many developing countries. So, this study uses an uncalibrated model based on established physical parameters. In Egypt, there are no monitoring field measurements for every watershed. Hence, the statistical distributions were adopted for the approximate estimation of rainfall depth at the meteorological station that affects the research area for various return periods and created an intensity duration frequency curve (IDF) in the return periods (25-50-100 years) in the Safaga Valley Basin. In the present study, the HEC-HMS model was used to create a runoff simulation in the Safaga Valley Basin. Also, the SCS curve number method, SCS unit hydrograph method, as a transform method was applied to simulate the hydrological processes. Also, assessing the study's findings by carrying out a field visit in the Safaga Valley Basin. The primary goal of this study is hydrological modeling of rainfall-runoff and Flooding in the Safaga Valley Basin applied the HEC-HMS Model through GIS environment to calculate the peak discharges, direct runoff volume and create hydrographs in the return periods of the sub-basins in the Safaga Valley Basin. Results showed result of the modeling in the return periods of the sub-basins in the Safaga Valley Basin where the total peak discharge in return period 100 years is 698.4 (m³/s) and sub-basin 7 is the largest peak discharge in return period 100 years where reached 137.5 (m³/s) and the total discharge volume in return period 100 years is 12288.5 (1000m³) and sub-basin 7 is the largest discharge volume in return period 100 years where reached 3050.2 (1000m³). In this regard, a flash flood risk assessment of the Safaga Valley sub-basins identified five possible hazards: very low, low, moderate, high, and very high. In addition, the finding shows that the hydrodynamic hazard is largest (High and Very high) in the SB2, SB3, SB4, and SB6 subbasins. In recent decades, the study area has seen devastating flash floods, which have had a significant impact on infrastructure, livelihoods, and human lives. So, this study recommended emphasizing these regions as top objectives for future flood mitigation strategies. The results demonstrate that the developed HEC-HMS model provides a crucial tool for sustainable land use planning and the design of flood protection infrastructure in the Safaga Valley Basin.