Lower Rangitāiki stopbank upgrade

We’re upgrading around 1.25km of stopbanks along the lower Rangitāiki River (next to Thornton Beach Road).

Why are we doing this?

Flood protection assets (such as stopbanks) are periodically checked to ensure they are still fit for purpose to protect communities from flooding.

Soil testing and computer modelling have been undertaken on the flood defences along sections of the Rangitāiki River (awa).

Using this information, as well as what we know about climate change, several flood defences along the awa have been identified as needing an upgrade – including this stretch of stopbanks along Thornton Beach Road.  

This upgrade will address the identified issues in the stopbank and ensure these defences can continue to protect the community, now and into the future.

This project is part of a wider work programme to upgrade our flood protection network on the Rangitāiki River. Other projects include the Rangitāiki Floodwalls and Rangitāiki Floodway and Spillway.

Flood protection is the first line of defence when it comes to reducing the impact of significant flooding and we currently manage more than $440M of flood defences on behalf of the community.

Find out more about our flood protection.

What’s happening?

We are upgrading around 1.25km of stopbanks along Thornton Beach Road.

One of the main reasons is due to seepage (the flow of water through stopbanks and underlying materials). While controlled seepage can relieve pressure within the stopbanks, excessive seepage can lead to stopbanks failing, putting people and properties at risk.

Find out more about seepage:

The stopbank upgrades include:

• Deconstructing the current stopbanks and rebuilding them with suitable soil.
• Raising the height of the stopbanks and the land level in the properties across the road.
• Installing seepage control drainage. This involves building a trench at the base of the stopbank (land side) and filling it with drainage material (such as gravel). This will allow water to pass through in a controlled manner, and relieve the water pressure building up inside and under the stopbank.

How will you be impacted?

• When construction is happening, traffic management will be in place as we may need to occasionally reduce traffic to a single lane. Residents will still have access at all times.
• There will be construction noise and vibrations, which we will be monitoring throughout.
• The boat ramp will remain open at all times, however there may be limited access to the awa in and around the construction site.
• Construction is from due to start by late 2023 and expected to be completed mid-2024.

Thank you for your patience during this time.

Got questions? Talk to our team: engineering@boprc.govt.nz