Surge threat from Dart landslip dam

A lake forms last night behind the Dart Valley landslip. Photo / GNS Science/GeoNet

All trampers are safe and have been accounted for after the Dart River was blocked by a landslide at Sandy Bluff, about 10km above Chinaman's Bluff.

The slip occurred on Saturday about noon and posed a hazard for trampers, campers and boat enthusiasts, authorities said.

Everyone was warned to stay away from the area, the Department of Conservation (DoC) and the Queenstown Lakes District Council said in a joint statement on Sunday.

GNS scientists from Dunedin and Wellington attempted to assess the landslide and hazard by helicopter yesterday afternoon, but were hindered by poor weather conditions.

DoC conservation services senior ranger Richard Kennett, of Glenorchy, said there is extensive flooding at Dredge Flat, upstream of the slip. Trampers were having to detour 2km through forest to get around flooded parts of the track.

"DoC is strongly advising people to defer planned tramps on the Rees Dart circuit until the hazard has been fully assessed and more information is available," Mr Kennett said.

Harbourmaster Marty Black said boat enthusiasts, kayakers and other recreational users should stay out of the Dart River until further notice.

While the Dart River's flow has dropped to minimal levels because of the damming effect upstream, there is a constant risk pressure behind the slip will force a surge of water through. This would be a danger for anyone in the river bed below the slip.

Mr Kennett said yesterday afternoon the water was clearly rising in volume by the hour.