Crews are redirecting the Conway River away from State Highway 1 south of Kaikōura as work steps up to rebuild a section of road badly damaged by last month’s flooding.

New Zealand Transport Agency said on Friday significant progress was being made on restoring the highway near Hawkswood, where floodwaters from the Conway River ate away large sections of the road during severe weather in July.

SH1 between Cheviot and Kaikōura reopened on 15 July after being closed for several days, but traffic management remains in place across a section of more than one kilometre where the river runs close to the highway.

Motorists are being advised to continue planning for delays of up to 20 minutes, with traffic held at times in both directions and a temporary reduced speed limit in place.

Following the flooding, crews initially cleared slips and brought in large quantities of rock to reinforce areas where the highway had been eroded.

NZTA said the focus had now shifted to redirecting the Conway River away from the road, allowing crews to begin rebuilding the embankment.

The ultimate aim is to restore SH1 to two full traffic lanes and a road shoulder.

Where possible, existing river channels are being used to guide the river flow away from the base of the washout.

Ecologists have also been working at the site as the recovery operation moves into the river environment.

Traps have been set and fish found within the work area are being progressively relocated before construction takes place, with NZTA saying the work is being carried out in a way designed to minimise impacts on the river.

The damage followed heavy rain in early July which caused major disruption to the South Island road network.

Floodwaters from the Conway River washed away sizeable sections of SH1 near Hawkswood, while slips brought rocks and vegetation down onto the highway.

The extent of the damage meant SH1 between Cheviot and Kaikōura remained closed while crews brought in rock, cleared debris and stabilised the road corridor.

Geotechnical engineers were also brought in to assess the surrounding hillsides for further movement and slip risks.

By 13 July, NZTA had set a target of reopening the highway at midday on 15 July, subject to there being no further slips or safety concerns.

The reopening went ahead as planned, although the damaged section near Hawkswood was reduced to a single lane with stop/go traffic management and a reduced speed limit.

NZTA said despite those delays, reopening SH1 provided a significant time saving compared with the alternative route using State Highways 7, 65, 6 and 63.

Recovery work has continued since then as crews work towards fully reinstating the highway.

NZTA has thanked motorists for their patience and understanding while the work continues.