Problem $2$

Compute the peak runoff, $Q_p,$ for a $15-$year storm using the Rational Method

for a drainage basin located in Phoenix, Arizona, and having parameters as

follows:

$A=14\mathrm{.}06$ acres

Time of concentration

Overland flow: average grass, $100\text{'}$ long, $5\mathrm{.}0\%$ average slope

Shallow concentrated flow: ${50}^{\text{'}}$ long, $7\mathrm{.}0\%$ average slope

Runoff coefficient

Impervious: $0\mathrm{.}06$ acres

Grass: $6\mathrm{.}5$ acres

Woods: $7\mathrm{.}5$ acres

Note: In the Arizona I$-$D$-$F curves, a $15-$year storm is located by the

corresponding $P_1$ value, which for Phoenix is $1\mathrm{.}75$ inches.