Flood Risk & Drainage
The site lies within Flood Zone 1 which is an area classified at low risk of fluvial flooding. All other sources have been assessed to present a low residual risk to the site and therefore it can be concluded that the site is suitable for its proposed use as residential development.
Preliminary surface and foul water drainage strategies have been prepared which demonstrate that the site can be satisfactorily drained without detrimental effect to third party land. The site requires a foul pumping station in order to drain foul flows.
It is proposed that surface water is attenuated on site within above and below ground attenuation features before discharging at restricted greenfield runoff rates to the nearby existing watercourse below Warwick Highway. An online detention basin is proposed along the eastern edge of the development which will restrict flows to 2.1 l/s and discharge back into the adoptable network. Due to the feature being constructed as online basins, water quality enhancement will be provided prior to discharge.
A second attenuation feature which comprises a combination of an underground cellular tank and an above ground basin is proposed to be situated in the south of the development prior to final discharge to the existing watercourse beneath Warwick Highway. Flows will be restricted via flow control chambers to equivalent greenfield run-off QBAR rates of 16.4 l/s.
