HEC‑RAS Culvert FHWA Full Flow Computations

Culvert flowing full

For culverts flowing full, the total head loss (or energy loss) through the culvert is measured in feet (or meters). The head loss, HL, is computed using the following formula:

The head loss (1)

The friction loss in the culvert is computed using Manning’s formula, which is expressed as follows:

Manning's formula (2)

friction loss

The exit energy loss is computed as a coefficient times the change in velocity head from just inside the culvert, at the downstream end, to outside of the culvert at the downstream end. The entrance loss is computed as a coefficient times the absolute velocity head of the flow inside the culvert at the upstream end.

About the Author Chris Maeder

Chris Maeder

Chris is an experienced civil engineering and software technology leader, with over 30 years industry experience. With proven expertise in global software development, he has built engineering teams that adapt quickly, focus on what’s important and, most importantly, deliver. He is a licensed professional civil engineer with extensive experience in water resource engineering. He has performed and supervised engineering projects in urban stormwater drainage, transportation and roadway drainage, storm sewer design, detention pond design, stormwater quality, green infrastructure, watershed management planning, wastewater sewers, water distribution networks, pump stations, FEMA flood studies, bridge and culvert design, bridge scour and armoring, dam failure analysis, seepage and groundwater modeling, and environmental permits.

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