WHEN WATER RUNS UPHILL – A FLOOD CONTROL SCHEME THROUGH GROUNDWATER MANAGEMENT

Positioned next to Maungatapere Township in Northland, the residential subdivision Te Mara Estate has been developed with construction undertaken through the 2015/16 summer. The sites location within a basin with no defined outlet has seen the area frequently inundated following prolonged wet periods. Drainage to the neighbouring catchment was identified as the most feasible long term solution. The requirement for minimised total lifecycle cost, constraints such as covenanted bush areas, and the sites inherent soil and topographic attributes, culminated in a groundwater management scheme involving rain gardens and subsoil drainage, a 400m Ø200 syphon line primed by vacuum pump, and control system by PLC with remote groundwater monitoring stations. The design objectives and considerations, along with scheme construction, testing and operation are discussed.