Question One: Road Drainage $(15$ marks$)$

a$)$ A proposed subdivision near Hamilton city consists of $45\%$ medium$/$high density residential

areas, $30\%$ open spaces, $15\%$ business areas and $10\%$ transport corridor including arterial

roads. Assuming that the catchment area approximates a rectangle measuring $1800m$ by

$6500m.$

Hamilton city's rainfall design data is derived from the Ruakura rainfall gauge. The values of

rainfall intensities and runoff coefficient are provided in tables $1$ and $2.$ Assume the

catchment has a time of concentration of $3$ hours for a $10$ year ARI event. Using the rational

formula, calculate the catchment discharge for a $10$ year ARI event. $(5$ marks$)$

Table $1$: Rainfall Intensities $(m\frac{m}{h}r)$

Table $2$: Runoff Coefficient