The design discharge for a culvert is 13.8m3 /s when the normal depth in the rectangular river channel is 1.9m. The channel has a bankful width of 4.2m, a slope of 1 in 300 and a Manning’s n of about 0.040s/m1/3. The maximum permissible upstream depth is 2.2m (i.e. 2.5m less 0.3m freeboard). The culvert will have a length of 35m. Design a single barrel, rectangular culvert that will operate with outlet control, following the general procedure and example given in the text. The site is environmentally sensitive so allow for the invert being 0.15m below existing bed level, thus enabling a layer of stones and gravel to be provided on the channel bottom.