The challenges that managers and urban planners have long observed are preventing urban flooding, and failure of drainage structures. Only stormwater drainage systems hydraulically with high reliability can accomplish this. The objective of this study was to evaluate the hydraulic performance of the existing stormwater drainage systems in Woreta Town. Maximum annual rainfall data from 1987 to 2016 were used. The intensity duration frequency curves of the study area was developed using the Log-person type III. The physical parameters of the sub-catchments, especially the terrain of the catchments of the study area, were examined using Google Earth and ArcGIS. The SCS TR-20 method was utilized in HydroCAD to determine the culvert catchment peak discharge. The analysis of the culvert flow overtopping was performed using HY-8. The maximum channel flow rate, maximum velocity, and maximum water level were assessed using a stormwater management model. The 213-hectare region was chosen for the SWMM area because it has drainage problems and has historically been prone to flooding. 42 sub-catchments make up the model's area, and its drainage system consists of 56 conduits, 57 junctions, and 7 outfalls. The two most sensitive parameters N-pervious and N-impervious were calibrated using ten channel flow depth observations in 2021 until the simulated and observed flow depth values reached an acceptable threshold, and seven events in 2022 to verify the model. The SWMM model performs best at C21 (R 2 =0.95, d=0.97, and NSE =0.84), C36 (R 2 =0.93, d=0.96, and NSE =0.85), and C21 (R 2 =0.79, d=0.94, and NSE =0.78), and C36 (R 2 =0.71, d=0.82, and NSE =0.58), respectively, in terms of calibration and validation. According to the SWMM finding, the research area has poor freeboard performance on several channels. But there is high velocity performance on almost all channels except C39. The weighted System reliability is 68%. This shows that while the all over system's performance is acceptable, it is not exceptional. The HY-8 model's findings show that culverts 1 and 3 have overtopping problems. This study suggests redesigning road culverts that have issues with overtopping and storm drainage to meet the minimum freeboard standard. Key Words: HydroCAD, HY-8, SWMM, Reliability