Computer Determination of Flow through Bridges

Techniques used for the computer determination of water surface profiles through bridge structures of various shapes and sizes, including culverts under high fills, are presented. The techniques are incorporated in the Hydrologic Engineering Center Program on Water Surface Profiles. Theoretical aspects of procedures for low flow-through bridges using momentum principles are described in detail for both supercritical and subcritical flow. Methods for determining the controlling type of flow (low flow, pressure flow, weir flow, or various combinations of these) and corresponding changes in water surface elevation, are described and illustrated. Stress is placed on the need for additional research and field data to evaluate the accuracy of various techniques that are suited to computer determination of water surface profiles through bridges. Limitations of the procedures are described.