The Manawatu Gorge has been closed due to rising river levels damaging the temporary route through the gorge.
Transport Agency Palmerston North state highways manager David McGonigal says the route was closed to traffic late on Thursday.
River levels rose to nearly seven metres higher than normal, eroding the slope and washing away the slip material which helped to support the temporary road, he said.
A team was sent to man the floodgates on the Manawatu River from 6pm on Friday after the river threatened to burst its banks. However, the Manawatu-Whanganui Regional Council later said it was unlikely the gates would have to be opened.
Farmers collapsed their fences and cleared stock from the floodway as a precaution.
The Opiki floodway is already under water and the Opiki road has been closed on Friday, but the council says there are no concerns about water levels in the rest of the region.
The Manawatu Gorge was shut for nine months after 370,000 cubic metres of debris fell on the road in August last year.
A temporary route through the gorge was opened to motorists in May this year while the Transport Agency continued its work on slip-damaged State Highway 3.
David McGonigal said the level of damage meant it was unlikely the temporary road would be rebuilt, and the agency would instead focus its efforts on accelerating the construction of bridges to replace those destroyed by last year's slip.
He said that on current estimates, the bridge work was expected to take between four to six weeks to complete.
Motorists are advised to use the Saddle Road or Pahiatua Track.