STORMWATER SYSTEMS $(30\%)$

You are asked to design a stormwater pipeline for a small portion of the urban$/$rural area within the city of Colorado. This pipeline has diameter of $0\mathrm{.}80m($Manning$\text{'}$s $n=0\mathrm{.}015),$ slope of $1\%$ and discharges water from an area of $80,000m^2\mathrm{.}25\%$ of this area is urban with runoff coefficient $c=0\mathrm{.}60,$ whereas the remaining $75\%$ is rural with runoff coefficient $c=0\mathrm{.}30.$ The intensityduration$-$frequency curve is given by the following equation:

$i(\frac{mm}{hr})=\frac{260(T^{0\mathrm{.}15}-0\mathrm{.}60)}{(1+\frac{\text{d}\text{u}\text{r}}{0\mathrm{.}15}{)}^{0\mathrm{.}75}}$