A broad$-$crested weir is designed for a riprap

lined trapezoidal channel that has a bottom width of

$6-$ft and side slopes of $3$:$1($H:V or m $=3).$ The riprap

lining has a Manning$$s n of $0\mathrm{.}042.$ The channel bed has

a slope of $0\mathrm{.}1\%(1$:$1000),$ however the slope is

horizontal through the weir transition zone. The

trapezoidal geometry through the weir is constructed

by pouring concrete into a form that has the same $3$:$1$

side slope as the channel, but with a $4-$ft bottom width

that is located $2-$ft higher than the channel bed.

Assume the flow entering the weir transition zone is at

normal depth. Over what range of flow rates is this

broad$-$crested weir valid