Estimating surface runoff volume using a curve number model in the Wadi Bani Walid basin – Libya

Abstract

This research aims to conduct a hydrological analysis of the Wadi Bani Walid basin to assess its response to surface runoff. The Curve Number-Corridor (SCS-CN) method was used to estimate the runoff from a rainstorm with an average rainfall of 73.44 mm. Calculations showed that the basin has a low maximum storage capacity (S=11.14) mm and an initial loss (Ia=2.23) mm, resulting in a large surface runoff depth of 61.58 mm and a total volume exceeding 104 million cubic meters. Four different experimental methods were applied to calculate the concentration time (Tc): Kirbych, California practice, Giandotti, and SCS delay. Comparison of the resulting unit curves revealed a significant variability in the peak discharge (Qp) and peak time (Tp), with Qp values ​​ranging from 15.33 to 33.59 m³/s per 1 mm of runoff. The time-discharge curve for the original storm was derived, showing a peak discharge of 2067.8 m³/s, indicating... High flood risk; the research provides a detailed engineering and hydrological analysis of these findings and their crucial impact on the design of flood control structures and soil erosion risks.