Project introduction

This project aims to reduce the number of flood related closures on a low-lying section of SH1 near the Kakanui River just south of Oamaru. With no practical alternative route available, these closures cause serious disruptions on the main road freight corridor between Canterbury and Otago.

  • Estimated project cost

  • Project type

    Road improvements
  • Project status


About the project

This flood prone 350m section of SH1 travels through the Kakanui River flood plain. Changing weather patterns are increasing the frequency, about every three to five years of large floods that can shut the highway for up to two days.

These closures are highly disruptive and costly for businesses and communities who depend on the goods and services moved on this main road freight link between Christchurch and Dunedin. Alternative routes involve several hours of extra travel time, at least 200km of extra distance to journeys for highway users, and additional costs.

This project intends lowering the flood risk on a vulnerable 350m section of SH1 through the Kakanui River flood plain, by raising the highway up to 1.25m above its current height.

Project funding is being provided from the $6 billion NZ Upgrade Transport Infrastructure Programme, with $300m allocated for regional transport investment opportunities such as this. We expect to complete this project by mid-2024.

  • Key features
    • Raising 350 metres of SH1 by up to 1.25m through the Kakanui River floodplain.
    • New road surfacing and markings.
    • Better access to nearby historic Clarks Mill and construction of a new bridge structure over the existing historic Mill Stream Culvert.
    • Greater safety from a wider raised road fitted with 300m of safety barrier on its western side. 
  • Benefits
    • Fewer flood related disruptions with the highway passable during one in 50-year floods.
    • A reduction in flood-related delays on the main road freight route between Canterbury and Otago.
    • Improved road access to keep communities connected during major flooding.
    • Greater resilience on a flood-prone section of SH1 between Oamaru and Dunedin.