Land drainage  |  24 Jun 2019

Flood protection work in Christchurch’s southwest has lessened the risk of properties near the Heathcote flooding and created a new wetland area and walking tracks for the public to enjoy.

The work has been done by Christchurch City Council as part of its Land Drainage Recovery Programme and has involved substantially increasing the capacity of the Wigram East storage basin, which sits within Ngā Puna Wai.

Sunset over the new Wigram basin.

Sunset at the Wigram East storage basin, which lies within Ngā Puna Wai.

“We have lowered a large area of the park for flood storage and created four hectares of wetland,’’ says Council Land Drainage Manager Keith Davison.

“In a one-in-100 year storm event the basin can now store around 590 million litres of water – the equivalent of more than 236 Olympic-sized swimming pools – which means there will be less risk of properties along the upper reaches of the Heathcote flooding.

“The new wetland area will provide a habitat for a number of threatened species and will also help to clean the water as it leaves the basin and flows into the Heathcote,’’ Mr Davison says.

The Council fast-tracked the $7.25 million project to extend the Wigram East storage basin to provide critical flood mitigation, and scheduled it at the same time as work on neighbouring Ngā Puna Wai Sports Hub.

By doing the two projects in tandem, the Council was able to use the material excavated for the basin to help build the sports hub, saving millions of dollars and greatly reducing the need for material to be trucked away through neighbouring residential streets.

As part of the flood protection work an extra kilometre of walking track has been added to the park.

“This area has always been popular with walkers and as part of this project we’ve been able to add to, and improve, the existing walking tracks. The tracks now link into the newly opened Ngā Puna Wai sports hub and to the Southern Motorway cycleway,’’ Mr Davison says.

“By the end of July we hope to bring the fences around the site down so that people can get in and explore the area.’’