Catchment Projects: Darley Drain

The Darley Drain catchment includes properties within the Wallnutt Ave/Marine Ave area. This catchment is most heavily impacted by flooding due to its low lying nature.

A large diameter concrete pipe was installed between Wallnutt and Marine Ave to Darley Drain. The pipe network is not designed to cater for large rainfall events, which causes localised flooding during heavy rainfall. The lower area acts like a basin, filling up until it can no longer hold stormwater. At this point stormwater will spill towards Palm Grove area.

Extensive modelling has been undertaken to identify solutions to best manage the stormwater. Modelling indicates properties within this catchment will flood in a two year event. This is especially likely if a heavy rainfall coincides with a high tide.

All modelling indicates that due to the nature of this catchment, cost effective protection of dwellings from flooding during large storm events may be unfeasible. Council strongly encourages landowners to raise their dwellings above the flood level and will support them by waiving our resource and building consent processing fees if they choose to do this.

Further mitigation options are being considered to reduce flooding during the more frequent rain events and funding has been included in the Long-Term Plan.

Council plans to commission assessments on the feasibility of detention and diversion options within the “Maranui” catchment. These options could potentially provide some mitigation towards existing flooding in the area however, it is unlikely to fully resolve the flooding issue.