Invercargill City stop bank upgrade project
- Funded: $3m by Government
- Total project investment: $4m
- Project duration: 2 years
Environment Southland is upgrading the Waihōpai River, Otepuni Stream and Kingswell Creek stop banks to meet the increase in extreme sea levels in the New River Estuary/Kōreti resulting from climate change. This project is part of a more comprehensive programme of climate resilience work underway to protect our region's largest urban centre, Invercargill/Waihopai (population 57,000 +) and critical infrastructure (Invercargill airport) from inundation.
Flood protection for Invercargill from the three waterways and from high sea level/ storm surge events in the estuary has evolved and developed over time. The last significant improvement to these protection measures followed the devastating January 1984 floods, when floodwaters forced more than 5000 people from their homes. Substantial investment in flood protection infrastructure followed, including construction of the Waihopai River flood detention dam (large enough to hold a volume of water equivalent to 800 Olympic-sized swimming pools).
There have been no significant upgrades to this infrastructure since this time (essentially over the last 30 years).
The latest climate resilience initiatives for the city include widening and raising the height of the stop banks alongside the Waihopai River between North Road and Stead Street and enhancing existing flood defences along the lower reaches of the Otepuni and Kingswell streams. Government funding received via the Kānoa - Regional Economic Development & Investment Unit (within the Ministry for Business Innovation and Employment) will see the stop bank upgrades completed sooner than planned and at a much-reduced cost to Southland ratepayers.
To complement this work, Invercargill City Council are replacing the existing Stead Street stop bank with a sheet pile wall. The top of the new Stead Street floodwall will be the same height as the raised Waihōpai, Otepuni and Kingswell stop banks and will be a much more robust defence than the existing earth embankment. ICC will also be widening and raising the height of the adjoining Cobbe Road stop bank.
Together the projects will comprehensively address the vulnerabilities Invercargill has to climate change and provide much more resilient flood defences for our community and Invercargill's critical infrastructure.
The existing Waihopai and Kingswell stop banks will be increased in height and strengthened. New floodwalls will be built along the lower reach of the Otepuni Stream, matching the height of Invercargill City Council's Stead Street sheet pile floodwall. The work along the Waihopai will extend from the Philip Street Railway Bridge to the Stead Street Bridge. Multi-purpose pathways that have been developed along the stop banks will be reinstated.
There will be some disruptions to the movement of traffic, cyclists and pedestrians while the work is underway. We will be implementing temporary traffic management plans to mitigate the increase in heavy transport vehicles and construction machinery. Temporary road, footpath and cycle track closures and detours will also be necessary.
- Protection for our homes, communities, and critical infrastructure
- Flood protection upgrade projects completed much sooner and with a much-reduced impact on Southland ratepayers
- Enhanced shared path network for Invercargill/Waihopai
- Site investigations and detailed design associated with the Waihopai stop bank modifications are underway
- Engagement with affected landowners and key interest groups has commenced
- Obtaining resource consent
- Completing detailed design and calling for tenders for construction
- Construction is scheduled to start in early 2022