Gully Control and Drop Spillways

A drop spillway headwall has weir crest length $L = 5.0\text{ m}$ and head $H = 0.64\text{ m}$ ($0.64^{1.5} = 0.512$). Taking discharge coefficient $C = 1.8$, discharge $Q = C L H^{1.5} = 1.8 \times 5.0 \times 0.512$ in $\text{m}^3/\text{s}$ is (rounded off to two decimal places):