Entrance Loss Coefficients and Inlet Control Head–Discharge Relationships for Buried-Invert Culverts

In current practice, entrance loss coefficients and inlet control head–discharge relationships for buried-invert culverts designed for fish passage applications are either ignored or approximated using traditional culvert design data due to a lack of data specific to these alternative culvert geometries. This study experimentally determined entrance loss coefficients and inlet control head–discharge relationships for circular culverts with invert burial depths of 20, 40, and 50% and an elliptical culvert with 50% invert burial depth. In general, the inlet loss coefficients for buried-invert culverts were higher than for traditional culverts of the same cross-sectional shape without invert burial. The influence of approach flow conditions (ponded or channelized) on inlet loss coefficients and inlet control head–discharge relationships was also investigated. This paper outlines the experimental methods used to determine entrance loss coefficients and inlet control head–discharge regression constants relative to these alternative culvert geometries and presents the data relevant to the hydraulic design and evaluation of these culverts.