An open area $(10$ acre$)$ in one town in Ba$,$ Fiji will be developed into parks and

golf courses $($area $=7$ acre$),$ with the rest of the area as paved parking lots.

The existing open space is in good condition soil group D$.$ A $10-$yr control

design period is required, with a $1-$hr rainfall duration $($the IDF curve given

below is found to be applicable in the area$).$ Using Natural Lost Method,

design the volume of detention pond $($in acre$-$ft$)$ required for the area to

minimize the impact on runoff flow brought by the development. $10$ points

TABLE $3-18$ Runoff Curve Numbers $($average watershed condition, $I_1=0\mathrm{.}2S)$

Curve Numbers for

Hydrologic Soil Group

Land Use Description

Fully developed urban areas ${?}^2($vegetation established$)$

Lawns, open spaces, parks, golf courses, cemeteries, etc.

Good condition; grass cover on $75\%$ or more of the area

Fair condition: grass cover on $50\%$ to $75\%$ of the area

Poor condition: grass cover on $50\%$ or less of the area

Paved parking lots, roofs, driveways, etc.

Streets and roads

Paved with curbs and storm sewers

Gravel

Dirt

Paved with open ditches