Engineers are surveying the new channel cut by the Waiho (Waiau) River at Franz Josef Glacier, but there are no plans to try to re-train the river back to its normal course.
An estimated 95% of the main flow of the river started flowing north through the Tatare Stream after heavy rain on January 18-20.
The river began shifting towards the neighbouring Tatare in mid-2023, forcing the council to abandon plans for a series of bunds or embankments along the lower Waiho, below the Franz Josef town sewerage ponds.
While there was now concern about the river being up against the northern bank in front of the sewerage ponds, the southern bank stopbanks on the usually vulnerable Waiho Flat side of the river, have been left high and dry.
West Coast Regional Council engineering staff were now surveying those stopbanks before carrying out interim maintenance, and was also awaiting the results of a new Lidar survey of the riverbed, which used light to create three-dimensional images of a landscape, to understand the new direction of the river’s main channel.
A South Westland resident claimed last week a large bulldozer was being moved towards Franz Josef, probably in an effort to change the course of the river.
Responding, council chief executive Daryl Lew said the council was simply “mobilising” its resources in the area as it weighed options to deal with the situation.
Chairman Peter Haddock said the bulldozer seen last week was nothing to do with the regional council or any plans to divert the Waiho River.
Haddock said he was aware a private landowner at Waiho Flat had contracted a large bulldozer to undertake work to protect their land, but it had nothing to do with the council.
“To my knowledge, the bulldozer is not being engaged by council,” he said.
However, the council was getting organised for the medium term maintenance of the existing stopbanks on the south side “to hold the line” while the riverbed was dry.
It hoped to get the green light from Government funding agency Kanoa to use some of the reserved $8.77 million granted under the original co-funded $24 million Waiho protection scheme for that work, he said.
The south bank repairs were ahead of the longer term plan to abandon the Waiho Flat to the river by pulling down the banks, starting in about 10 years’ time.
Haddock said options for possibly diverting the river channel would need to go to the community first before any decisions were made.
“Unless there’s a distinct emergency, that needs to go to the rating district first.”
Sewerage pond risk to be assessed
The risk to the sewerage ponds on the north bank remained a matter for the Westland District Council to assess, he said.
While Westland had now said it wanted to add protection below the sewerage ponds, that would only be an interim solution and would also need to go to the rating district, “if it’s deemed the ponds are at risk”.
“The rating district has to decide if it has an appetite.”
Haddock said the regional council continued to monitor the Waiho flowing via the Tatare Stream and the gorge.
If it continued to escalate, then any protection solutions from below the end of the sewerage ponds were likely to be beyond the rating district and council’s capacity and would require Government intervention, he said.
DISCLAIMER: Te Runanga o Makaawhio chairman Paul Madgwick, who is a member of the West Coast Emergency Management Joint Committee and the Franz Josef Joint Rating District is also the editor of the Greymouth Star. He took no part in commissioning, writing, or editing this story.
By Brendon McMahon for Local Democracy Reporting
LDR is local body journalism co-funded by RNZ and NZ on Air