HY8 is a BASIC program developed by the Federal Highways Administration and used to evaluate hydraulics of a culvert system. Results (peak flows) computed by one of the hydrologic models supported in WMS can be used to design/evaluate different sizes and combinations of culverts.
WMS contains a graphical user interface to the HY8 program for most of the frequently used options. In order to evaluate irregularly shaped culverts and other options not supported by the WMS user interface you will need to run the HY8 program outside of WMS. The installation of WMS includes a full installation of the HY8 program and is contained in the HY8 directory (this directory can be found in the same directory where WMS is installed). Because of the way the HY8 program is compiled all HY8 input/output files created by WMS will be stored in this directory.
Because of the difficulty of setting up the HY-8 program to run in automated fashion within a Windows environment (the executable is a DOS program) you may find it easier to use the computed results for hydrology from WMS and then run HY-8 outside of the WMS program. Documentation for the interface is provided here, but we recommend running HY-8 outside of WMS.
This section of the WMS reference manual describes the user interface to HY8 while more detailed explanations can be found in the HDS-5, "Hydraulic Design of Highway Culverts," HEC-14, manual describing the methods automated by HY8.
HY8 General Specifications and Limitations
Saving the Input File
Single Culvert Analysis
Minimizing Culvert Width
Multiple Culvert Analysis and Overtopping