In recent years, rainfall-induced floods in various Egyptian towns affected several regions, and the area in east Cairo was the worst. The present study aims to detect the rainfall-runoff relationships of the Heliopolis watershed and its sub-basins, to estimate peak discharge and flood volume for the storm event (12 March 2020) and predicting the runoff volume and peak discharge of the flows for various return intervals. This was achieved by applying the Hydrological models (HEC-1and HMS) program using a unit Hydrograph namely SCS-CN. The drainage system and the identification of sub-basins were established using SRTM DEM, 90 m resolution. The maximum daily rainfall per year was investigated and determined for various return times using the statistical analysis tool Hyfran. Results reveal that the peak discharge (Qp) and flood volume value (Qv) of the Heliopolis watershed are 686.8 m3/s and 48039.8 m3.