Station owner hopes for 'permanent lake' after landslide stabilised

Monday, 16 April 2018

A landslide on the Mangapoike River between Wairoa and Gisborne caused this large lake to form.

A landslide between Gisborne and Wairoa which caused a large lake to form has been stabilised.

On Monday, Gisborne District Council said strategic management of the slip in Muriwai had stabilised the area, and the previously-closed Paparatu Rd had been reopened.

Last month, Hawke's Bay Civil Defence manager Ian Macdonald said the landslide, which was likely triggered by a small, localised earthquake, had become a 'significant hazard' and people were warned to stay away from it.

It resulted in about 80 million tonnes of material forming a large dam on a small tributary to the Wairoa River, which was about 40 metres deep and rising by about 60 centimetres per day.

Explosives were used to cut a two-metre deep trench to release water from the lake.

That trench had since been enlarged to improve water flow and further reduce water levels, eliminating risks to a nearby bridge and farmland.

Mangapoike Station owner Dan Jex-Blake said it had been a stressful few weeks.

'We are hopeful we can have a permanent lake at the end of this that will provide a habitat for rare and endangered wildlife. It's been amazing to see how fast rare species such as dabchicks have adapted to life on the new lake.'

The landslide and lake are located on private property, with the lake occupying about 33 hectares and being inaccessible to the public.

Council scientist Murry Cave said it was too soon to predict the end result, but indications were that the lake would remain at a safe level.

Council staff had been working with Hawke's Bay Regional Council, Wairoa District Council and scientists from Auckland University throughout the response.

The council would continue to monitor the situation over the next few weeks until long-term stability of the lake was established.