Slip closes track until next year

River bank erosion in the Dart Valley has brought down trees, creating a ''tangled mess'' for the...
River bank erosion in the Dart Valley has brought down trees, creating a ''tangled mess'' for the Department of Conservation to deal with. Doc announced yesterday the track, affected by a massive slip in January 2014, will be closed until at least...

The Department of Conservation says ''nature is in charge'' when it comes to carving a new track through the Dart Valley - which will probably remain closed until next year.

And, once an active slip which has been wreaking havoc in the area is deemed stable enough to resume work, it will cost up to $250,000 and could take as long as 10 years to fully reinstate the track.

Following a slip in the area in January 2014, which formed a new lake, a downstream section of the track was lost.

Doc began forging a new ''rough'' track around the lake, but that has also been lost due to recent heavy rain keeping the slip active.

Doc conservation services manager John Roberts said the new lake had begun rising again and had ultimately ''overtopped the rubble dam'', carving out a deep overflow channel and pushing more sediment over boulders and sand deposited by the landslide.

''As a result, the bed of the Dart River has been raised even higher than before, exacerbating erosion issues over the first kilometre or so downstream from the landslide,'' he said.

''The river is scouring and destabilising this area and the scale of undercutting erosion continues to surprise.''

Formerly intact hillsides had slipped, new tracks were emerging and trees had been washed away with some crashing into others, producing a ''tangled mess''.

GNS Science had had to ''rescue'' monitoring equipment which had been thought safe from the river's erosive force.

Mr Roberts said the delay in reinstating the track had been frustrating. However, ''we have to acknowledge that nature is in charge''.

''The river could keep eroding until it meets some nearly vertical bedrock lining the valley edge.

''If we build a new track too soon, it could again be lost and our efforts wasted, too.

''When we do get going, we are expecting slow progress through steep bluffs.

''We regret to announce the Dart Valley track may remain closed until at least the new year.''

Doc partnerships ranger Chris Hankin, of Queenstown, said before the initial slip the department had been upgrading sections of the track to ''manage impact'' due to its increasing popularity.

Some of that work had been lost because of the initial and subsequent slips.

Further, the department had spent about $10,000 and almost two months of staff time on forming the temporary track and doing logistical work on planning for an alternative route.

Funding for that work had come from Doc's ''reactive fund'', which was available to help with capital expenditure relating to natural events.

The majority of that investment was now gone.

''The estimate, at this stage ... to get a track in past all the damaged bits is up to $250,000,'' Mr Hankin said.

''That's why we're not going ahead until the situation is stable ... we can't categorically say when [that will be].

''We are hopeful of getting in there and getting it open in the new year, but ... if another event happens that will set us back more.

''It's in the lap of the gods.

''It [the slip] has proven to be more of a headache then we initially thought.''

tracey.roxburgh@odt.co.nz

Add a Comment

 

Advertisement