New Approach to Design of Culverts

The current procedures for the design of culverts are reviewed. Experiments at LaTrobe University, Bendigo, Australia, indicated that the head-versus-discharge relation under inlet control is slightly different from what the design charts give. New generalized relations between head water level and discharge are presented for inlet-control conditions after fitting the experimental data. As the ratio of end depth to the critical depth varies with the slope of the culvert and the discharge, the practice of considering the critical depth should be viewed with caution. The present investigation suggests that the head water depth required to pass a given discharge through a pipe culvert of a given size is much less when the pipe runs full with the tail water level at the top of the pipe at the exit than the head water level required to pass the same discharge under inlet conditions. It is therefore recommended that the culvert be designed to flow under outlet-control conditions with the tail water level coinciding with the top of the pipe.