$(9$ pnts$)$ Using the Manning$$s equation and assuming that the flow depth will remain

constant please give the effect of $\backslash$pm $20\%$ inaccuracy in the channel roughness $($n$)$ on the

velocity of flow $($V$,$ fps$)$ for

a$.$ An unlined open channel $($earth$,$ uniform section$)$

b$.$ A Bermuda grass covered grass lined roadside channel with a flow depth of $6$

inches, and

c$.$ A minor stream with a gravel bottom with no vegetation