Waihōpai Invercargill stop bank upgrade

Waihōpai Invercargill is at risk from flooding from the three waterways surrounding the city and from high sea level/storm surge events in the estuary. As a result, the flood protection for the city 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 Waihōpai 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 work

The latest climate resilience initiatives for the city include widening and raising the eastern side stop bank on the Waihōpai River between the Ohai Rail Line Crossing and Stead Street and the installation of rip rap rock. The existing stop bank is approximately 3.2 km long and is a combination of reclaimed land and constructed stop bank. Work is being undertaken in four sections, beginning with Beatrice Street north to the railway line crossing.

This project will create a more robust flood defence for Waihōpai Invercargill City and is the first phase of work to future-proof the Waihōpai River stop banks. An upgrade to the western side stop bank will happen in the next phase of climate resilience projects.

To complement this work, Invercargill City Council has replaced the Stead Street stop bank with a sheet pile wall and widened and raised the height of the adjoining Cobbe Road stop bank.

Together the projects will systematically begin to address the vulnerabilities Waihōpai Invercargill has to climate change and provide much more resilient flood defences for our community and Invercargill's critical infrastructure.

Multi-purpose pathways that have been developed along the stop banks will be reinstated. These pathways will be wider and consistent with other shared pathways in the region.

Each section of stop bank will have diversions in place for cyclists and pedestrians while the work is underway. Traffic management will be in place to ensure the safety of track users while heavy transport vehicles and construction machinery are on the track.

The stop bank has several areas of trees and shrubs, which unfortunately need to be removed, but the team will be looking at alternative areas for planting and salvaging plants from these areas where possible.