Based on problem $12-43.$ Uniform flow: compute velocity $V$ and volume flowrate $Q$ for the following portions of the compound channel:

A $-$ Central "main" channel section with $y=2ft$

B $-$ Floodplain sections only $(1$ & $3)$ with floodplain depth $=6ft$

C$-$Entire stream channel section $($main $+$ floodplains$)$ at "bank$-$full" flow conditions, $y=8ft$

Given conditions: $S=0\mathrm{.}0008,n1=n3=0\mathrm{.}08($sparse vegetation$),n2=$ unfinished concrete $0\mathrm{.}015$