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.