The Dart River has been blocked by a landslide and is posing hazards for trampers, campers and boaties.
DOC and the Queenstown Lakes District Council are warning people to stay well away from the area of the slip, at Sandy Bluff, until experts can assess the extent of the slip and the hazard it poses.
They say there is extensive flooding upstream at Dredge Flat.
Trampers are having to detour two kilometres 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.
Harbourmaster Marty Black says boaties, kayakers and other recreational users should stay out of the Dart River until further notice.
While the Dart Rivers flow has dropped to minimal levels because of the damming effect upstream, there is a constant risk that 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.