$7\mathrm{.}63.$ Design a $40-$m$-$long overflow spillway that will discharge

a design flow rate of $1600$ m$3/$s at a maximum$-$allowable pool elevation of $200$ m$.$ The bottom elevation behind the spillway is $170$ m$,$ the upstream face of the spillway has a $1$:$1$ slope, and the spillway chute is to have a slope of $1$:$1\mathrm{.}5($H:V$).$