Hydraulic Design of Highway Culverts - DOT On-Line Publications

Figure I-5--Precast Concrete Box Culvert
(American Concrete Pipe Association)
3
Figure I-6--Corrugated Metal Arch
(Contech)
The hydraulic capacity of a culvert may be improved by appropriate inlet selection. Since the
natural channel is usually wider than the culvert barrel, the culvert inlet edge represents a flow
contraction and may be the primary flow control. The provision of a more gradual flow transition
will lessen the energy loss and thus create a more hydraulically efficient inlet condition (Figure I-
8). Beveled edges are therefore more efficient than square edges. Side-tapered and slopetapered
inlets, commonly referred to as improved inlets, further reduce the flow contraction.
Depressed inlets, such as slope-tapered inlets, increase the effective head on the flow control
section, thereby further increasing the culvert efficiency. Figures I-9 and I-10 depict a sidetapered
and a slope-tapered inlet respectively.
Figure I-7--Four Standard Inlet Types (schematic)