FLOOD09911

• County: Statewide
• Basin: Statewide
• Title: Culvert Design
• Date: 8/1/2000
• Prepared By: Ayres Associates
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Lesson 3

Culvert Design - Participant Workbook

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INLET CONTROL
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3.31 a Outlet Velocity Under Inlet Control

3.31 b Outlet Velocity Under Outlet Control

E. The outlet velocity should then be considered to evaluate the need for
outlet protection:

1. If the controlling headwater is based on inlet control, determine the
normal depth and velocity in the culvert barrel. The velocity at
normal depth is assumed to be the outlet velocity.
2. If the controlling headwater is based on outlet control, determine
the area of flow at the outlet based on the barrel geometry and the
following: (1) critical depth if the tailwater is below critical depth, (2)
the tailwater depth if the tailwater is between critical depth and the
top of the barrel, (3) the height of the barrel if the tailwater is above
the top of the barrel.

F. The evaluation of headwater conditions and outlet velocity is repeated
until an acceptable culvert configuration is determined. To facilitate the
design process, a Culvert Design Form is provided in HDS-5.

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3.32 Culvert Design Form

G. Once the barrel is selected, it must be fitted into the roadway cross
section. The culvert barrel must have adequate cover, the length should
be close to the approximate length, and the headwalls and wingwalls must
be dimensioned. Culvert analysis and design can be completed using
HYDRAIN.

3-15

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