(c) Culvert outlet structures
A proper device has to be provided at the outlet of a culvert to prevent the
downstream erosion of the bed and the slopes of the embankment. For
small discharges a straight or U-shaped end wall is sufficient. For moder-
ate flows a flaring wing-walled outlet connecting the much wider down-
stream channel will reduce the scouring of the embankment and channel
banks. The suggested flare angle for supercritical flows should be under 1
in 2, decreasing linearly with the flow Froude number. For subcritical flows
it may be larger than 1 in 2.
(d) Scour below culvert outlets
The flow through a culvert may cause undesirable erosion (scour) at its
unprotected outlet which can lead to undermining of the culvert structure.
432 CROSS-DRAINAGE AND DROP STRUCTURES
Fig. 10.9 Drop inlet culvert
