A 350m stretch of road near Maheno is going to be raised 1.25m, in hopes of reducing flood-related road closures.
The $3million project, which will take eight to 10 months to complete, will start at the end of this month.
Locals are concerned the increased road height will act as a dam, and make flooding worse.
Waitaki District mayor Gary Kircher understands the need to raise the road, but said some things should be done in conjunction with the works.
Gravel build-up should be removed from under the bridge culverts and included in the works.
He said locals pushed for culverts to be added so the water would not all be pushed to one spot.
Mr Kircher had heard from locals who had completed works to minimise flooding at their own properties.
"It may be worth nothing if a whole lot more water gets pushed their way."
He thought Waka Kotahi was taking the simplest option to keep the road open.
"They need to look further than just how to keep the road open."
Waka Kotahi NZ Transport Agency senior project manager Jason Forbes said other options had been assessed, including adding culverts, finding an alternative route for SH1 and maintaining the current road height.
Modelling showed culverts would not be effective and the road would potentially have to be raised higher to allow culverts located between ground level and the road.
Alternative routes for the highway were considered but required the use of Kakanui Point Bridge, which did not accommodate heavy vehicles.
Other alternatives routes also had limitations.
Raising the road "achieved a balance between improved resilience to the transportation network, construction costs and impacts upon other landowners".
He said modelling showed the 1m increase would significantly decrease flooding in a one-in-50-year flood and would have no more closures for the three to five-year floods.
The adverse effects of the roadworks were considered minor, while the resilience of the highway would be improved and communities could stay better connected during flooding events.
Otago Regional Council consultant planner Ralph Henderson prepared the resource consent application.
Consents to divert water as well as land use consent to alter defence against water and alter a structure over a river were granted.
The ORC received two submissions against the change — one from the Waitaki District Council and one from the Maheno Water Committee.
The application was approved to be processed on December 23, 2021.
In a Tonkin and Taylor report commissioned by the ORC, the consultants identified that while the raised road would act as a dam and exacerbate flooding on some properties, it would do so only marginally and the buildings would be inundated during large flood levels anyway.
Those affected would include farm landowners, the Maheno Bowling Club, the Maheno Rugby Football Club and some residential properties on Island Stream Rd and Maheno-Kakanui Rd.
Maheno resident Kerri Bell thinks the works are unnecessary.
She said the river did not flood often and it would be better to have gravel build-up removed from the river.
"If they take that out, that would fix some of the problem."
She said the roadworks would cause 10 months of inconvenience, compared to a few hours of inconvenience every two or three years, when it did close.
She thought the works would funnel water towards the bridge and put additional strain on the existing infrastructure.
Maheno Water Committee trustee Barbara Small has lived in Maheno for about 16 years and cannot remember the road being closed because of flooding for more than 24 hours.
She said the reports also underestimated the amount of flooding the area experienced.
Mrs Small said she would prefer to see the money spent upgrading Kakanui Point Bridge, allowing an alternative route through Kakanui.
The road was last closed in 2021, and she recalled people trying to get through despite the high water levels.
She estimated the road was closed for 12 hours.
She had other concerns about flooding, including a large pile of logs which were being stored upstream from the bridge.
Mrs Small said Waka Kotahi’s reports had not taken these factors into consideration.
Other community assets would still be affected by flooding including the rugby grounds and bowling club.
"These are people in our community."
The Tonkin and Taylor report said it was not all bad for the Maheno residents, as people living near Clarks Mill would have reduced flooding after the works.
