Hydraulics

Once design flows are obtained, culvert hydraulics is employed to determine the required culvert size. Standards vary by the jurisdiction, but the primary design criteria for culverts is Headwater and Velocity.

To perform a culvert hydraulic analysis, the Channel Hydraulics must be analyzed first, then the Culvert Hydraulics. The channel flow depth from the Channel Hydraulics is an input variable into the Culvert Hydraulics analysis.

Channel Hydraulics

Channel hydraulics must be performed before Culvert hydraulics, because the channel flow height is an input into the culvert hydraulics analysis. An approximate channel cross-section is usually sufficient to analyze the flow. Enter the channel cross section, slope, and flow data and the flow height and normal channel velocity will be calculated.

Culvert Hydraulics

To determine the required culvert size, use this calculator. The required criteria varies by jurisdiction but normally the primary variables are the headwater elevation (for flooding, backwater purposes) and flow velocity (for erosion purposes). This analysis engine uses the HDS-5 methodology, developed by the U.S. Federal Highway Administration (FHWA).