Hydraulic Design of Highway Culverts - DOT On-Line Publications

Example Problem #4 (English Units)
An existing 7 ft by 7 ft concrete box culvert was designed for a 50-year flood of 600 ft³/s and a
design headwater elevation of 114 ft. Upstream development has increased the 50-year runoff
to 1,000 ft³/s. The roadway is gravel with a width of 40 ft. The roadway profile may be
approximated as a broad crested weir 200 ft long. Use Figure III-11 to calculate overtopping
flows, and the following site data:
Inlet Invert Elevation: 100 ft Entrance Condition: Square Edges
Slope: 5 percent Roadway Centerline Elevation: 116 ft
Culvert Length: 200 ft
Prepare a performance curve for this
installation, including any roadway overtopping,
up to a flow rate of 1,000 ft 3 /s.
NOTE: Design Charts 8B, 14B, 15B, and Figure
III-11 are used in this solution.
66
Tailwater Information:
Flow, ft³/s TW, ft
400
600
800
1000
2.6
3.1
3.8
4.1