Farmers asked to think long-term while still dealing with last year’s flood damage

Farmers are being asked to work together on long-term solutions to flooding in Te Hoiere/Pelorus, while some just want immediate riverbank repairs to protect their properties.

A meeting was held on Thursday night at local pub, The Millers Rest, to encourage farmers to support a community approach to reducing floodwater damage.

Keeping the meeting on course proved difficult though, with some vocal landowners more interested in urgent fixes to damage caused by the August 2022 floods, when up to a metre of rain fell in the catchment in 24 hours.

They were frustrated they weren’t allowed to remove gravel and trees from rivers to stop bank erosion, without expensive resource consents.

Matt Oliver, an environmental scientist at the Marlborough District Council, promised a separate meeting with rivers staff to talk through solutions to those problems. Thursday night’s meeting was about longer-term, community-led restoration, Oliver said.

Dr Jon Tunnicliffe, geomorphologist at Auckland University, spoke at the meeting, and said the history of the waterways of Te Hoiere/Pelorus could be used to inform solutions to flood damage.

Tunnicliffe had been studying the Pelorus catchment with funding from the Marlborough District Council, Te Hoiere/Pelorus Project and Department of Conservation. He showed historic aerial photos and high-tech LiDAR imaging which gave a detailed picture of its history.

With large-scale maps, it would be possible to anticipate where sediment was coming from and where it might go – a planning tool which would help people think more strategically and be used to protect river ecology, Tunnicliffe said.

Oliver invited the landowners to work with Tunnicliffe to identify river control techniques which could help slow the river, slow erosion and reduce flood flows. Techniques would be based on solutions used along erodable rivers in Europe and the United States.

The aim was to “flatten the curve” like the familiar Covid graph, Oliver said. Modelling could simulate the ability of large and small structures like bunds, barriers, leaky ponds and wetlands to capture sediment and diverting flow onto former floodplains to minimise damage.

This was an alternative to hard engineered works like stopbanks which once overflowed were no longer providing protection and may impound water.

Geoff Dick, the council’s senior rivers technical engineer, said there was no community scheme to protect Te Hoiere/Pelorus River from floods, although this was proposed in 1969 by the Marlborough Catchment Board. At today’s prices, that would cost $100 to $130 per hectare in rates.

Several voices in the audience suggested this might be cheaper than the cost of flood damage to their farming businesses.

Dairy farmer Justin Morrison said if LiDAR modelling showed 60% of sediment in the Havelock Estuary came from eroded riverbanks, why did the council make it so hard for landowners to get permission to fix upstream problems.

Dick said the council could give permission to do urgent works, such as removing a tree that was blocking the river to protect assets like houses and bridges.

“But … don’t put a digger in the river and start working on corners, or you’re breaking the law.”

Otherwise, works required resource consents. A joint application by neighbouring landowners was possible.

Removing gravel from the riverbed might benefit the person doing it but was likely to have downstream impacts, he said.

This echoed an earlier caution from Oliver, that “the gravel buildup in one person’s land tends to come from an eroding spot further upstream”.