This approximately $11 million project is designed to reduce costly flooding in Whangārei's Central Business District and parts of Morningside and the Raumanga Stream floodplain.
The Hopua te Nihotetea detention dam forms an integral part of both council's region-wide priority rivers project and a multi-phase project to reduce the impact of flooding in Whangārei's CBD. (The latter also involves river clearance to remove blockages and a recent $1M jointly-funded upgrade of the city's Rust Avenue Bridge to improve stream flows beneath it.)
Physical construction of the dam, located at the ends of Raumanga Valley Road and Kotuku Street, began in September 2014 with practical completion achieved in December 2015.
The 18-metre high dam will hold up to 1.27 million cubic metres of floodwater during heavy rain (about two-thirds of the capacity of the existing Whau Valley dam, which meets much of the city's demand for drinking water).
The detention dam works by slowly releasing trapped stormwater over a couple of days, reducing river swelling and downstream flooding that would otherwise threaten Whangarei's CBD and surrounding suburbs during a storm.
The dam is being paid for via the targeted Whangārei Urban Rivers Management Rate on more than 17,000 properties in the CBD and contributing catchment areas.