Ashley Rakahuri flood resilience project

Over the next several years, we’re planning to create new flood resilience measures along the 22km section of the Ashley Rakahuri that runs between the Ōkūkū River and Waikuku Beach.

Our goal is to strengthen flood resilience for Rangiora, Kaiapoi, Waikuku, and surrounding areas.

The feedback survey closed on 31 August 2026. You can still add comments in the design options section, ask questions in the questions and answers section, or email us at rivers.delivery@ecan.govt.nz

Feedback received by 5pm on Wednesday 30 September 2026 will also be considered as part of the options analysis process.

There will be further opportunities to have your say as the project progresses.


Why we’re doing this work now

Early flood protection works on the Ashley Rakahuri started in the 1930s. The existing stopbank scheme has protected the district for around 70 years, but over that time, the flood risk has increased.

  • Recent events, such as the Kaikōura floods, Auckland Anniversary floods and Cyclone Gabrielle, have demonstrated that extreme rainfall and flooding are happening more often and causing greater damage than in the past. Scientific evidence shows these types of events are becoming more frequent and intense.

  • There are now more people, homes, businesses and infrastructure located within the Ashley Rakahuri floodplains. This means the consequences of flooding are higher than they were when the scheme was first built. View our flood modelling maps to see the areas that could be affected during a 1‑in‑500‑year flood event.

  • Our modelling shows there is a risk of floods breaking out at different points along the river. We want to ensure our flood protection reflects today’s risks and that they are fit for the future.

Our approach

As we follow the Ashley Rakahuri from its confluence with the Ōkūkū River to the coast, the river changes. Flood breakouts can travel in different directions and have different impacts in different places. That's why we're looking at the river in three reaches, each requiring different ways to manage breakout flooding risk.

Reaches:

  • Reach 1: Ōkūkū confluence → Rangiora Railway Bridge

  • Reach 2: Railway Bridge → SH1 Bridge

  • Reach 3: SH1 → the ocean


What options we're considering

We’re considering a range of possible solutions that may be combined. Different approaches may be needed for different parts of the river. These include:

  • Upgrading or modifying the existing primary stopbank
  • One or more secondary stopbanks
  • Managed floodways
  • Stopbank retreat
  • Berm vegetation management
  • Wetland creation / room-for-the-river approaches
  • Gravel management

At this early, investigative stage of the project, we have no preferred option/s. Your feedback will help select a preferred option by correcting our assumptions and highlighting unintended consequences. This will be balanced with other criteria such as safety, practicality for land use, environmental and cultural outcomes, feasibility and cost.

Have your say on flood resilience options

Over the next several years, we’re planning to create new flood resilience measures along the 22km section of the Ashley Rakahuri that runs between the Ōkūkū River and Waikuku Beach.

Our goal is to strengthen flood resilience for Rangiora, Kaiapoi, Waikuku, and surrounding areas.

The feedback survey closed on 31 August 2026. You can still add comments in the design options section, ask questions in the questions and answers section, or email us at rivers.delivery@ecan.govt.nz

Feedback received by 5pm on Wednesday 30 September 2026 will also be considered as part of the options analysis process.

There will be further opportunities to have your say as the project progresses.


Why we’re doing this work now

Early flood protection works on the Ashley Rakahuri started in the 1930s. The existing stopbank scheme has protected the district for around 70 years, but over that time, the flood risk has increased.

  • Recent events, such as the Kaikōura floods, Auckland Anniversary floods and Cyclone Gabrielle, have demonstrated that extreme rainfall and flooding are happening more often and causing greater damage than in the past. Scientific evidence shows these types of events are becoming more frequent and intense.

  • There are now more people, homes, businesses and infrastructure located within the Ashley Rakahuri floodplains. This means the consequences of flooding are higher than they were when the scheme was first built. View our flood modelling maps to see the areas that could be affected during a 1‑in‑500‑year flood event.

  • Our modelling shows there is a risk of floods breaking out at different points along the river. We want to ensure our flood protection reflects today’s risks and that they are fit for the future.

Our approach

As we follow the Ashley Rakahuri from its confluence with the Ōkūkū River to the coast, the river changes. Flood breakouts can travel in different directions and have different impacts in different places. That's why we're looking at the river in three reaches, each requiring different ways to manage breakout flooding risk.

Reaches:

  • Reach 1: Ōkūkū confluence → Rangiora Railway Bridge

  • Reach 2: Railway Bridge → SH1 Bridge

  • Reach 3: SH1 → the ocean


What options we're considering

We’re considering a range of possible solutions that may be combined. Different approaches may be needed for different parts of the river. These include:

  • Upgrading or modifying the existing primary stopbank
  • One or more secondary stopbanks
  • Managed floodways
  • Stopbank retreat
  • Berm vegetation management
  • Wetland creation / room-for-the-river approaches
  • Gravel management

At this early, investigative stage of the project, we have no preferred option/s. Your feedback will help select a preferred option by correcting our assumptions and highlighting unintended consequences. This will be balanced with other criteria such as safety, practicality for land use, environmental and cultural outcomes, feasibility and cost.

Have your say on flood resilience options

Questions and answers

Questions about the project? Ask them here. We aim to reply to questions within five business days.

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  • Hi there, Is there any way to access more details of the flood modelling? Does it account for debris build up under the bridges? Thanks, Mel

    MelP asked 11 days ago

    Kia ora Mel, thanks for your question.
    You can see more flood modelling maps on the Waimakariri District Website:  http://www.waimakariri.govt.nz/environment/natural-hazards
    It is worth noting that the WDC modelling is similar to but not the exact same as the modelling we are using.

    At this early stage, the bridges themselves have not been modelled. We know that the actual water level immediately upstream and downstream of the bridges will differ slightly from our model results, but this effect is constrained to a localised area. Debris buildup is accounted for when assessing the capacity of the bridges by allowing a safety margin (freeboard) between the model water level and the underside of the bridge. Our modelling will be refined as the project progresses.


  • How does this account for further land development on the south side, such as Gressons Road, the Pegasus Golf Course, and Tulls Road? The Ashley problem should not be investigated in isolation.

    Carsten asked about 2 months ago

    Thanks for your question.

    Environment Canterbury is working closing with staff from Waimakariri District Council (WDC) on the Ashley Rakahuri Flood Resilience Project. Our project focuses on reducing the risk and impact of out-of-river flooding, which offers increased protection to existing and future land uses.  

    We understand there is some concern about the impact of increased development on stormwater flow and volumes, particularly in Taranaki Creek and Waikuku Stream. Land use planning is a responsibility shared between Environment Canterbury and Waimakariri District Council, and consideration of effects on receiving waterways would be required as part of the design and consenting process. 

    We've shared feedback and questions about the proposed development with WDC. You can also contact Waimakariri District Council directly for more information on how stormwater from new developments is managed in the district.

  • Who maintains the proposed secondary stopbanks if they go ahead- are the able to be grazed if not they will need to be mowed on a regular basis to stop them being a fire danger in the summer

    TrevR asked 5 months ago

    Thanks for your question. If an option including stopbanks is selected, Canterbury Regional Council (Environment Canterbury) would maintain vegetation on those stopbanks through a combination of mowing and grazing. Grazing of stopbanks with light livestock such as sheep would be arranged with individual landowners in a way that ensures stopbanks are not damaged by prolonged livestock movement.  

  • The proposed secondary stopbanks in many cases pass through productive farmland . The land used for the stopbank will reduce the productive area of land . Will ecan compensate farmers for loss of income . I suggest farmers will need to be compensated on a yearly basis

    TrevR asked 5 months ago

    Thanks for your question. It depends on the option selected and how it interacts with a piece of land. In any case where land is required for stopbanks or floodways, landowners would be supported through Public Works Act processes, including independent valuation for compensation. The productive value of the land is considered as part of that compensation process. Any compensation payments would be on a one-off basis.

  • Where the proposed secondatry stopbank passes across a property how do you provide access across stopbank for machinery tractors etc and stock movement

    TrevR asked 5 months ago

    Thanks for your question. If a secondary stopbank is constructed, access considerations would be worked out on an property-by-property basis. If a stopbank runs across a property, earth ramps would be constructed to provide access for stock or machinery. 

  • Has the ecology of the areas of land that may be used for secondary stopbanks been considered , in my case there are lizards and also birds nesting

    TrevR asked 5 months ago

    Thanks for your question. Any ecological concerns or assessments will be addressed during the consent application phase once we have selected a preferred option. We will need to clearly demonstrate in our consent application that we are not having an adverse effect on the receiving environment, including any ecological impacts.

Page last updated: 31 Aug 2026, 05:09 PM