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There is no immediate danger of a large volume of water being suddenly released down the Dart River below a dam created by a landslip on Saturday, GNS Science staff asserted yesterday, but Doc is still watchful.
The landslip occurred at Sandy Bluff, about 10km above Chinamans Bluff, about noon on Saturday and a silt band had been deposited in the river, causing a lake to form behind the band.
A statement from the Department of Conservation (Doc) yesterday said the lake was now more than 3km long, spanned the full width of the Dart Valley and was up to 20m deep.
The Dart River flowed through the lake before exiting across the landslip debris and as water had begun to flow past the landslip debris, the river was no longer blocked, Doc said.
The lake was expected to slowly subside as the river eroded the landslip debris.
Jet-boat operator Dart River Jet resumed trips on the river yesterday afternoon. The company had suspended operations shortly after the slip.
Dart River Jet regional manager David Kennedy said while the main Dart River channel had changed direction at the point of the slip, this was normal for the river after heavy rainfall.
''GNS, Doc, the harbourmaster and Dart River Jet are all confident that the lake that has formed will gradually lower, that no abnormally high flows will be experienced downstream, and that there are no additional hazards posed in the Dart River below the slip area,'' he said.
Doc conservation services manager John Roberts said many sections of the Dart Valley Track between Daleys Flat Hut and Bedford Stream ''are either underwater or are undercut and have fallen away''.
The track was closed between Daleys Flat Hut and Bedford Stream and would be for ''some time''.
''As the lake is not likely to disappear quickly, this track closure will remain in place until further notice. Tramping the complete Rees-Dart circuit is, therefore, not feasible.''
However, trampers could still walk the Rees Valley to Dart and Daleys Flat Huts but would need to return the way they came or exit via the Matukituki Valley.
From the Dart Valley road end, people could still walk from Chinamans Bluff as far as Bedford Stream before returning.
The landslip occurred within an known area of instability in the Te Koroka-Slip Stream area and recent rain had brought down significant debris, which in some places was several hundred metres wide.
Queenstown Lakes District harbourmaster Marty Black said people could undertake recreational activities near the river but should stay alert for any condition changes.
Doc said until more was known about long-term consequences of the landslip, it would be monitored closely.