$6\mathrm{.}8\mathrm{.}3.$

An obstruction is lodged in a $10-$ft wide rectangular channel $($concrete$)$ that has a bottom slope of $0\mathrm{.}0025.$ The depth of the channel just upstream of the obstruction is $5\mathrm{.}0$ ft $.$ If the flow rate is $325$ cfs$,$ determine the channel and flow classification $($e$.$g$.,$ S$-3,$ M$-2,$ etc.$).$

Explain your supporting logic.