Discussion and Closure: New Approach to Design of Culverts

The tests conducted by the author cover two types of culvert flow, both with inlet control. The first has an unsubmerged inlet in which the upstream head is less than about 1.3 D and the second has a submerged inlet but a free outlet, with air access from downstream. The culvert used by the author in his tests is rather short, less than 20 pipe diameters, so that in this case there is no question of outlet control unless a high TW level is present. The 1:40 barrel slope seems to have been chosen to ensure supercritical flow in the barrel. The author suggests two empirical equations for the case where HId is less or greater than 1.28. Eqs. (3) and (4) can be put in the form