Kumeū flooding review

Following the extreme weather events in 2023, Auckland Council determined the Kumeū area could benefit from a blue-green network project, as part of Making Space for Water.

This assessment builds upon a review conducted following the flooding that affected Kumeū and Huapai in August 2021. As a result of that review, we:

• updated our flood models
• revised floodplains to consider future urban development.

Flood resilience options investigation

In 2024, we worked with experts to investigate ways to enhance flood resilience in the Kumeū-Huapai township. This included identifying potential infrastructure options and assessing their costs and benefits.

The investigation showed that there is currently no viable solution to reduce flood risk. Because of this, we will not continue further planning of a large-scale risk reduction infrastructure project.

Read about the challenges of flood management and the details of our community meeting in February 2025:

Options available

We focused on three main options:

• extending the existing floodway
• diverting the Kumeū river
• building a dam.

Floodway extension

A 70m wide and 2.8km long extension to the existing Kumeū floodway to increase capacity.

Cost estimate: $379 to $573 million.

Assessment: Not financially feasible and increases flood levels downstream. Would reduce risk for 30 to 100 properties but leaves 70 to 140 at risk.

River diversion

A tunnel, 4.5m diameter and 1.9km long, to divert flows from upstream.

Cost estimate: $214 to $295 million.

Assessment: Very expensive relative to the benefit provided. Relies on inlet staying unblocked. Likely to experience opposition during consenting process because of environmental impacts.

Dam

A dam on the Kumeū River holding 1,800,000m³.

Cost estimate: $107 to $163 million.

Assessment: Would encourage further development in the existing floodplain. It will place properties and infrastructure at risk if the dam overflows or fails.

Ongoing maintenance

We will continue working to find ways to keep people safe - but understand that decisions made so far may be disappointing to some.

Since the weather events in 2023, we continue to:

• increase maintenance of the stream to help water flow better during smaller storms
• improve monitoring in known high-risk flood areas
• remove debris from streams across the region
• test new tools, including a river level alert system which we will trial with community involvement later in 2025.

Our Healthy Waters team conduct pre-storm and post-storm clearance checks on the public stormwater network's critical inlets and outlets.

Help prevent flooding

Report a problem online or call 09 301 0101 to tell us about any:

• potential blockages
• damage to stormwater assets
• flooding.

We have contractors available to respond to emergencies at all times.

Prevent flooding at home

Streams can overflow during heavy rain. If you have a stream on or near your property, keep waterways clear of debris and blockages. This can help prevent potential damage to your home.

For information about protecting your home from flooding, download our guide 'Preparing your Property for Flooding'.

More information

Visit What to do in a flooding emergency and Reduce flooding risks on your property .

Download the Rodney Local Board Emergency Readiness and Response Plan to learn what you and your family should do in an emergency.

Follow the Kumeū Emergency Network Facebook page to stay connected during an emergency.

Use the interactive map on the Auckland Flood Viewer to see if there are flood hazards present on your property.

Email bluegreen@aucklandcouncil.govt.nz for more information.