A dam created by a landslide between Gisborne and Wairoa earlier this month is rising rapidly and could fail at any time, Hawke's Bay Civil Defence is warning.
A large landslide on the Mangapoike River created a new lake on private property about 50 metres deep and is rising by 60 centimetres a day.
The landslide, likely triggered by a small localised earthquake, has resulted in approximately 80 million tonnes of material forming a large dam on a small tributary to the Wairoa River.
The area affected by the landslide is 25.8 hectares and the landslide is still moving.
"Downstream landowners and river users are strongly advised to keep out of the riverbed. The dam might fail at any time and there is a significant amount of water behind the landslide," Hawke's Bay Civil Defence Group Manager Ian Macdonald said.
"We're working closely with Gisborne and Wairoa District Councils, with support from Hawke's Bay Regional Council to assess the risk of dam failure and develop an ongoing management plan."
Specialised engineers engaged by the Hawke's Bay Regional Council are due on the site today.
Paparatu Road in the area is currently closed to the public and appropriate signage has been installed.