Waihōpai Invercargill stop bank upgrade

In May 2024, Environment Southland completed an upgrade to the Waihōpai River (true left) stop bank, designed to address the increased risk of extreme sea levels in the Kōreti New River Estuary due to climate change. This work is part of a broader effort to enhance flood defences for Waihōpai Invercargill.

Waihōpai Invercargill faces flood risks from three surrounding waterways and high sea level/storm surge events in the estuary. Flood protection measures have evolved over time, with the last major improvements occurring after the devastating January 1984 floods, which displaced more than 5,000 residents. Substantial investment in flood protection infrastructure followed, including the construction of the Waihōpai River flood detention dam, which can hold the equivalent of 800 Olympic-sized swimming pools of water.

This stop bank upgrade, along with recent work completed by the Invercargill City Council, marks the first major enhancement to the city's flood defences in 30 years.

Key upgrades completed

The project involved widening and raising the Waihōpai River (true left) stop bank between the Ohai Rail Line Crossing and Stead Street and installing rock protection along the riverbank. The original 3.2 km stop bank, which combined reclaimed land and constructed sections, has been strengthened to create a more robust flood defence for the city.

To complement this work, the ICC replaced the Stead Street stop bank with a sheet pile wall and widened and raised the adjoining Cobbe Road stop bank, further strengthening the city’s flood resilience.

Why these upgrades matter

Widening and strengthening the Waihōpai stop bank ensures it remains robust and adaptable to future climate impacts, allowing for potential height increases as climate models and predictions evolve. Together with complementary upgrades, these projects begin to address Invercargill's vulnerabilities and enhance resilience for the community and critical infrastructure.

Benefits

• Enhanced protection for people, homes, communities, and critical infrastructure in Waihōpai Invercargill.
• Future-proof design allows for further height adjustments as climate resilience needs change.
• Work completed with central government funding assistance, reducing costs for local ratepayers.
• The newly reinstated multi-use pathway meets high regional standards for shared pathways, offering both utility and recreational value.

Looking ahead

Community engagement will guide further resilience measures for Waihōpai Invercargill, ensuring the city remains prepared for meeting future climate risks.

Funding and collaboration

The Waihōpai River stop bank upgrade is part of the national Resilient River Communities initiative and was a collaboration between Environment Southland and Kānoa – the Regional Economic Development & Investment Unit, with support from Invercargill City Council and Waihōpai Rūnaka. It is one of six Resilient River Communities projects Environment Southland undertook with co-funding from central government via the Covid-19 Recovery and Response Fund in the period 2021-2024.

By building resilient river communities, we aim to minimise the environmental, economic, and social impacts of flooding, creating a safer Aotearoa New Zealand for everyone.