Problem $3\mathrm{.}31$

Based on the Manning's $n$ values of Tables $3\mathrm{.}7$ and $3\mathrm{.}8,$ determine the average relative

error that should be expected in a value of $n$ for the following conditions: $($a$)$ Unlined

open channel $($earth$,$ uniform section$)$; $($b$)$ roadside channel and swales $($depth up to

$0\mathrm{.}7$ ft $)$; $($c$)$ natural stream channels, minor stream $($fairly regular section$)$; and $($d$)$ natu$-$

ral stream channels, floodplains $($cultivated areas$).$ Assuming that the velocity, $V,$ and

roughness are related by $V=\frac{0\mathrm{.}2}{n},$ what would be the mean velocity and relative error

in the mean velocity for each of the four flow conditions?