Example $10\mathrm{.}2$: Direct$-$step calculation for a wide rectangular channel

Consider a smooth and near$-$horizontal wide rectangular channel with a unit discharge of $3\frac{m^2}{s},$ a normal depth $h_n=2m$ and Manning's coefficient $n=0\mathrm{.}035$ and slope $S_0=0\mathrm{.}00013.$ The direct$-$step method is used for the water$-$surface profile calculation near a vertical drop.