New route to bypass flooding

21:29, Jan 09 2014
DOC team
From left, Department of Conservation services ranger Michael de Boulay, conservation services senior ranger Richard Kennett, works officer Richard Struthers and partnerships ranger Chris Hankin at Dredge Flat. Beyond the group is the lake, Sandy Bluff and the Slip Stream landslide.

Department of Conservation rangers spent yesterday bush-bashing in the Dart Valley to mark a route for a realigned track after the massive weekend landslide opposite Sandy Bluff.

The Rees-Dart track near Glenorchy is virtually impassable from south of Sandy Bluff for more than 3 kilometres to Dredge Flat after the Slip Stream, a well-known unstable region on the true right of the valley, deposited large volumes of rock and sludge-like silt into the river about 10km north of Chinaman's Bluff.

DOC conservation services senior ranger Richard Kennett and two other rangers, Michael de Boulay and Richard Struthers, were helicoptered to Dredge Flat to survey a possible route through forest above the lake and around the bluff.

Slip
The landslide opposite Sandy Bluff, Dart River.

Mr Kennett said rangers had already marked out part of a potential route with orange tape.

"We have to get the big picture first, understand the extent of the problem, the priorities and the issues.

"There are areas we know are safe around the bluff. We have to try and link a new system from here [Dredge Flat] down to there [Sandy Bluff] over about 3 kilometres."

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He said staff expected the lake to get bigger before it drained or reduced in size so any route through the bush to the bluff and beyond needed to factor lake level.

"We are looking at total realignment."

The landslide on Saturday cut a deep channel from the top of Slip Stream down to the fan-shaped existing debris field and was dumping sludge-like silt into the river.

Department partnerships ranger Chris Hankin said short sections of track remained around the bluff but the rest was now submerged.

The slow-moving silty material forced the river to run along the true-left below the bluff and eroded the bank where trampers previously walked.

Rangers planned to investigate potential routes before drawing up the cost of realigning the track.

The increasingly popular Rees-Dart multiday loop tramp attracts 2000 people a year and 3000 day walkers.

Trampers can still access the walk from the Rees Valley end and the first 4km section of the Dart Valley end of the track, but it remains closed between Bedford bridge and Daleys Flat.

All other tracks in the region - Routeburn, Greenstone and Caples - remain open.

The Southland Times