The hydraulic analysis of culverts is complicated when using hand calculations. Fortunately, several computer programs are available to assist in analyzing culvert hydraulics, some of which include HY-8, Fish X-ing, Broken-back Culvert Analysis Program (BCAP), Hydraflow Express, Culvert Master, Culvert, and Hydrologic Engineering Center River Analysis System (HEC-RAS). While all of these programs can simulate the behavior of flow through a culvert, slightly different methodologies are utilized among the programs to complete a full hydraulic analysis, resulting in different predictions for headwater depth, flow control, and outlet velocities. The purpose of this paper is to compare (1) the available hydraulic features and (2) the numerical solutions from the seven programs to manually computed values. Four test cases were developed to test the accuracy of program results. The headwater depths and outlet velocities were compared to those obtained through calculations based on culvert hydraulic theory outlined in the Federal Highway Administration publication, Hydraulic Design Series 5. Based on the results, Fish X-ing was unable to analyze culverts under inlet control, while Culvert incorrectly predicted inlet control headwater depths at low flow conditions. Hydraflow Express struggled to predict correct outlet control headwater depths while BCAP had difficulty analyzing straight barrel culverts acting under outlet control. Overall, HY-8, Culvert Master, and HEC-RAS produced accurate results most consistently.



College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering



Date Submitted


Document Type





culvert hydraulics, hydraulic analysis