Two state highways could be closed every time the Mataura River looks like it could peak above four metres at Gore.

The roads were closed last week when a state of emergency was declared, so a large sand bund could be built north of Mataura, and sandbags could be placed near Kana St in Mataura.

Council general manager critical services Jason Domigan said based on advice and data from Environment Southland, the need to sandbag SH93 and SH1, north of Mataura, was triggered whenever the Mataura River was predicted to peak at 4.1m above normal at Gore.

“Modelling and knowledge from previous events has shown that the river will inundate land on the east and west sides at this level. There are flood banks to protect property. However, sandbagging the state highways intersecting these flood banks is required to stop flood waters breaching at the road,’’ he said.

Last Friday the modelling at 3:20pm (received by the council at 3:37pm) predicted the Mataura River would peak at 3.9m.

“While below the 4.1m trigger, there is always a level of uncertainty with this modelling, and it was too close to call. Keeping people safe and their property dry are always our priorities,’’ Domigan said.

Environment Southland, which owns the stop banks, referred comment to Waka Kotahi NZ Transport Agency.

An Agency spokesperson said there had not been any discussions about raising the level of the highway at either site to alleviate flooding issues.

At the State Highway 1 site it was very flat so elevating the road to go over a flood bank would need wider consideration (including safety) and resilience support.

At the State Highway 93 site, the flood bank was near the base of a hill, which if run to the hill would protect more land and leave SH93 protected by the flood bank.

“However we understand that there was no support from local landowner/s at the time to do this, so it was not pursued,’’ the spokesperson said.