In certain unique situations, a drop-inlet-type of culvert might be employed to a greater advantage than the standard box- or pipe-type culvert. A drop-inlet consists merely of a vertical drop-section at the upstream end of the culvert. The drop section is connected to the main barrel of the culvert by means of an elbow or merely a rightangle intersection. The entrance to the drop-section must collect and funnel the channel water into the drop section. Thus, intercepting dams and sidewalls may be needed to form the entrance. Figure 1 illustrates, in a general way, some of the options which may be considered in the design of a highway culvert. The diagram alludes to the particular case where the difference between inlet and outlet elevations is such that the slope-gradient is quite steep. Likewise, as envisioned in Fig. 2, drop-inlets may find some application in situations where there is not sufficient head-room beneath the pavement to permit the installation of a culvert to the desired slope -- that is, on the uniform grade between the upstream channel and the outfall channel.
Digital Object Identifier
Hughes, Ronald D., "A Study of the Hydraulics of Drop-Inlet-Type Culvert Models" (1963). Kentucky Transportation Center Research Report. 1219.