$9\mathrm{.}14$ Use flood routing analysis to determine the maximum water level for a flood control reservoir that has a watershed area of $50ha.$ The runoff depth for a $50-$ year return storm is $90mm,$ and peak runoff rate is $5\mathrm{.}4\frac{m^3}{s}.$ The outlet structure is a box$-$inlet spillway, $0\mathrm{.}9m$ square $($one side is the headwall$)$ with a weir coefficient of $1\mathrm{.}7$ and a $610-mm$ diameter concrete outlet pipe. The pipe is $34m$ long, with $K_e=1\mathrm{.}0$ and $n=0\mathrm{.}014.$ The elevation of the crest of the box inlet is $26\mathrm{.}8m$ and elevation of the center of the pipe at its outlet is $25\mathrm{.}6m.$ The cumulative storage available at each $0\mathrm{.}6-$ meter stage above the crest is $0\mathrm{.}06,0\mathrm{.}17,0\mathrm{.}41,0\mathrm{.}76,1\mathrm{.}32,2\mathrm{.}10,$ and $3\mathrm{.}22ha*m.$