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Design options (Reach 2 and 3)
14 days agoThese options apply to Reach 2 and 3, from Rangiora Railway Bridge to the ocean.
Primary stopbank upgrades:upgrading existing stopbanks where required. This option proposes raising and strengthening existing stopbanks where required to increase the level of flood protection provided. A geotechnical engineering consultant will investigate how and where this is possible.
Pros
• Minimises impacts on private land.
Cons:
Doesn’t address flow restrictions at the SH1 bridge, so a spillway may still be required.
May not be feasible to upgrade all sections of stopbank.
Option D1: Stopbank retreat on Environment Canterbury-owned land. This option proposes building a new stopbank on Environment Canterbury-owned land on the north side of the river and, once established, lowering or removing sections of the existing stopbank.
For Options D1 and D2, new flood protection vegetation would be planted and allowed to establish. The existing stopbank would then be lowered or removed.
Pros Increases flood-carrying capacity in this section.
Reduces constriction created by the existing stopbank alignment.
Primarily uses Environment Canterbury owned land.
Cons:
Will take time for new flood protection vegetation to establish.
Addresses capacity issues over a relatively short section of the scheme
(1.2 km).
Option D2: Stopbank retreat on Environment Canterbury-owned land
This option proposes building a new stopbank on Environment Canterbury-owned land on the north side of the river and, once established, lowering or removing sections of the existing stopbank.
For Option D1 and D2, new flood protection vegetation would be planted and allowed to establish. The existing stopbank would then be lowered or removed.
Pros Increases flood-carrying capacity in this section.
Reduces constriction created by the existing stopbank alignment.
Primarily uses Environment Canterbury owned land.
Cons Crosses privately-owned land so would require property acquisition or compensation arrangements.
Managed spillway: Engineered spillway on north-side of the river upstream of the SH1 bridge
The State Highway 1 bridge limits how much water can safely pass through this section of the river during flood events.
If flood capacity is increased, a spillway could be used to allow water to overflow from the river in a controlled manner to the north and into either Saltwater Creek or across the highway and into the estuary.Pros Reduces flood pressure on the SH1 bridge.
Improves flood protection for Waikuku.
Allows overflows to occur in a controlled and predictable way.
Guidebanks can help direct flood flows along a defined path.
Cons:
Will result in flooding of properties within the floodway, when activated (likely in excess of 3,000 cumecs – almost twice the recorded peak flow in May 2021).
Some properties in this area are at risk of flooding under existing conditions.
Estuary options: Modifications to stopbank on north side of the Rakahuri at the estuary
This option considers modifying the existing stopbank on the north side of the river downstream of SH1.
This might include lowering or removing sections of the existing north-side stopbank to relieve pressure on the south-side stopbank, and to lower flood levels near Waikuku Beach.Pros May reduce flood levels near Waikuku Beach.
Allow for the future effects of sea level rise by retreating flood protection from land that may be inundated.
Creates opportunities for large-scale estuary restoration.
Cons:
May affect private land and farming activities.
These options apply to Reach 2 and 3, from Rangiora Railway Bridge to the ocean.
Primary stopbank upgrades:upgrading existing stopbanks where required. This option proposes raising and strengthening existing stopbanks where required to increase the level of flood protection provided. A geotechnical engineering consultant will investigate how and where this is possible.
Pros
• Minimises impacts on private land.
Cons:
Doesn’t address flow restrictions at the SH1 bridge, so a spillway may still be required.
May not be feasible to upgrade all sections of stopbank.
Option D1: Stopbank retreat on Environment Canterbury-owned land. This option proposes building a new stopbank on Environment Canterbury-owned land on the north side of the river and, once established, lowering or removing sections of the existing stopbank.
For Options D1 and D2, new flood protection vegetation would be planted and allowed to establish. The existing stopbank would then be lowered or removed.
Pros Increases flood-carrying capacity in this section.
Reduces constriction created by the existing stopbank alignment.
Primarily uses Environment Canterbury owned land.
Cons:
Will take time for new flood protection vegetation to establish.
Addresses capacity issues over a relatively short section of the scheme
(1.2 km).
Option D2: Stopbank retreat on Environment Canterbury-owned land
This option proposes building a new stopbank on Environment Canterbury-owned land on the north side of the river and, once established, lowering or removing sections of the existing stopbank.
For Option D1 and D2, new flood protection vegetation would be planted and allowed to establish. The existing stopbank would then be lowered or removed.
Pros Increases flood-carrying capacity in this section.
Reduces constriction created by the existing stopbank alignment.
Primarily uses Environment Canterbury owned land.
Cons Crosses privately-owned land so would require property acquisition or compensation arrangements.
Managed spillway: Engineered spillway on north-side of the river upstream of the SH1 bridge
The State Highway 1 bridge limits how much water can safely pass through this section of the river during flood events.
If flood capacity is increased, a spillway could be used to allow water to overflow from the river in a controlled manner to the north and into either Saltwater Creek or across the highway and into the estuary.Pros Reduces flood pressure on the SH1 bridge.
Improves flood protection for Waikuku.
Allows overflows to occur in a controlled and predictable way.
Guidebanks can help direct flood flows along a defined path.
Cons:
Will result in flooding of properties within the floodway, when activated (likely in excess of 3,000 cumecs – almost twice the recorded peak flow in May 2021).
Some properties in this area are at risk of flooding under existing conditions.
Estuary options: Modifications to stopbank on north side of the Rakahuri at the estuary
This option considers modifying the existing stopbank on the north side of the river downstream of SH1.
This might include lowering or removing sections of the existing north-side stopbank to relieve pressure on the south-side stopbank, and to lower flood levels near Waikuku Beach.Pros May reduce flood levels near Waikuku Beach.
Allow for the future effects of sea level rise by retreating flood protection from land that may be inundated.
Creates opportunities for large-scale estuary restoration.
Cons:
May affect private land and farming activities.
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Option A (Reach 1)
4 months agoA secondary stopbank extending from the terrace on Mount Thomas Road to the east of the racecourse
This option would see us building a second stopbank further south of the river, starting at the terrace on Mount Thomas Road and connecting back to the primary stopbank just east of the racecourse.
Option A: A secondary stopbank extending from the terrace on Mount Thomas Road to the east of the racecoursePros
This provides two levels of protection for the urban areas of Rangiora and Kaiapoi, as well as the rural areas that are currently within the modelled flow paths for breakouts between the Ōkūkū to Rangiora
Cons
This is the longest alignment
The option crosses a significant number of properties
This option wouldn’t improve flood protection for properties in between the primary and secondary stopbanks, and would increase flood depths for some of these properties
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.A secondary stopbank extending from the terrace on Mount Thomas Road to the east of the racecourse
This option would see us building a second stopbank further south of the river, starting at the terrace on Mount Thomas Road and connecting back to the primary stopbank just east of the racecourse.
Option A: A secondary stopbank extending from the terrace on Mount Thomas Road to the east of the racecoursePros
This provides two levels of protection for the urban areas of Rangiora and Kaiapoi, as well as the rural areas that are currently within the modelled flow paths for breakouts between the Ōkūkū to Rangiora
Cons
This is the longest alignment
The option crosses a significant number of properties
This option wouldn’t improve flood protection for properties in between the primary and secondary stopbanks, and would increase flood depths for some of these properties
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Thank you for your contribution!
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Option B (Reach 1)
4 months agoA secondary stopbank from the terrace opposite Groyne 8 to the east of the airfield
This option would involve building a second stopbank further south of the river, starting around Groyne 8 and connecting back to the primary stopbank just east of the airfield.
Option B: A secondary stopbank from the terrace opposite Groyne 8 to the east of the airfield
Pros
- This would maximise the length of secondary stopbank protection
- This option would provide increased flood protection for more people living on the south of the stopbank
Cons
- This option would have implications for potential land development south of the airfield
- Constriction of breakout flow where the proposed bank first crosses Mount Thomas Road, requiring mitigation for high water velocities
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.A secondary stopbank from the terrace opposite Groyne 8 to the east of the airfield
This option would involve building a second stopbank further south of the river, starting around Groyne 8 and connecting back to the primary stopbank just east of the airfield.
Option B: A secondary stopbank from the terrace opposite Groyne 8 to the east of the airfield
Pros
- This would maximise the length of secondary stopbank protection
- This option would provide increased flood protection for more people living on the south of the stopbank
Cons
- This option would have implications for potential land development south of the airfield
- Constriction of breakout flow where the proposed bank first crosses Mount Thomas Road, requiring mitigation for high water velocities
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Thank you for your contribution!
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Option C (Reach 1)
4 months agoA secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 to the east of the airfield
This option would see us building a second stopbank south of the river, starting south of Groyne 7 and connecting back to the primary stopbank just east of the airfield.
Option C: A secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 to the east of the airfield
Pros
- As with option B, this option would maximise the length of secondary stopbank protection, meaning:
- It would provide increased flood protection for people living on the south of the stopbank
- This has the benefit of incorporating more natural terrain features into the design, which will minimise earthworks when we come to construction
Cons
- This option would have implications for potential land development south of the airfield
- Many dwellings within existing breakout flow towards the west of the river (the Ōkūkū confluence) would not get additional protection
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.A secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 to the east of the airfield
This option would see us building a second stopbank south of the river, starting south of Groyne 7 and connecting back to the primary stopbank just east of the airfield.
Option C: A secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 to the east of the airfield
Pros
- As with option B, this option would maximise the length of secondary stopbank protection, meaning:
- It would provide increased flood protection for people living on the south of the stopbank
- This has the benefit of incorporating more natural terrain features into the design, which will minimise earthworks when we come to construction
Cons
- This option would have implications for potential land development south of the airfield
- Many dwellings within existing breakout flow towards the west of the river (the Ōkūkū confluence) would not get additional protection
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Thank you for your contribution!
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No thanks - As with option B, this option would maximise the length of secondary stopbank protection, meaning:
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Option D (Reach 1)
4 months agoA series of shorter secondary stopbanks upstream of Groyne 7
This option would see us build a short secondary stopbank from the confluence of the Ōkūkū River, which returns the breakout flow around Groyne 7.
Option D: A series of shorter secondary stopbanks upstream of Groyne 7
Pros
- This is the shortest option, which minimises impact on people living in the area in relation to impact on land and construction
- It focuses on the high-risk section where two rivers meet
- It could be a standalone option, or used in conjunction with the other options
Cons
- It doesn’t address the risk of the primary stopbank failing further downstream
- Its efficacy would rely on extensive primary stopbank upgrades (these may be implemented anyway)
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.A series of shorter secondary stopbanks upstream of Groyne 7
This option would see us build a short secondary stopbank from the confluence of the Ōkūkū River, which returns the breakout flow around Groyne 7.
Option D: A series of shorter secondary stopbanks upstream of Groyne 7
Pros
- This is the shortest option, which minimises impact on people living in the area in relation to impact on land and construction
- It focuses on the high-risk section where two rivers meet
- It could be a standalone option, or used in conjunction with the other options
Cons
- It doesn’t address the risk of the primary stopbank failing further downstream
- Its efficacy would rely on extensive primary stopbank upgrades (these may be implemented anyway)
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Thank you for your contribution!
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Option E (Reach 1)
4 months agoA secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 and joining the primary stopbank west of the airfield
This option would see us constructing a secondary stopbank starting at the low terrace on Mount Thomas Road and joining the primary stopbank along Priors Road, to the west of the airfield.
Option E: A secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 and joining the primary stopbank west of the airfield Pros
- This is a shorter alignment
- It reduces the impact of land use and construction impact on neighbouring properties
Cons
- If the primary stopbank failed, there would be no additional protection between the airfield and Cones Road
- Requires extensive upgrades to primary stopbank from airfield to Cones Road
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.A secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 and joining the primary stopbank west of the airfield
This option would see us constructing a secondary stopbank starting at the low terrace on Mount Thomas Road and joining the primary stopbank along Priors Road, to the west of the airfield.
Option E: A secondary stopbank starting at the low terrace across Mount Thomas Road from Groyne 7 and joining the primary stopbank west of the airfield Pros
- This is a shorter alignment
- It reduces the impact of land use and construction impact on neighbouring properties
Cons
- If the primary stopbank failed, there would be no additional protection between the airfield and Cones Road
- Requires extensive upgrades to primary stopbank from airfield to Cones Road
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Thank you for your contribution!
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Option F (Reach 1)
4 months agoUpgrading the existing stopbank network
This option considers upgrading the existing stopbanks, keeping the existing alignment the same (likely with a wider footprint), and increasing the height. Engineered erosion protection and strengthening measures such as rock protection and groynes would be required to increase resilience.
Option F: Upgrading the existing stopbank network
Pros
- This option minimises impact to private property as it follows the existing alignment
- Stopbank upgrades are likely to be required in some sections regardless of any alternative option selected
- Minimal impact on proposed developments and existing activities
Cons
- No backup protection if floodwaters overtop or erode the stopbank
- A higher stopbank allows the river to carry more water, which means better protection in most circumstances but potentially greater impacts for nearby properties if the stopbank is damaged during an extreme flood
- Extent of strengthening could be significant as erosion can occur anywhere along the stopbank system
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Upgrading the existing stopbank network
This option considers upgrading the existing stopbanks, keeping the existing alignment the same (likely with a wider footprint), and increasing the height. Engineered erosion protection and strengthening measures such as rock protection and groynes would be required to increase resilience.
Option F: Upgrading the existing stopbank network
Pros
- This option minimises impact to private property as it follows the existing alignment
- Stopbank upgrades are likely to be required in some sections regardless of any alternative option selected
- Minimal impact on proposed developments and existing activities
Cons
- No backup protection if floodwaters overtop or erode the stopbank
- A higher stopbank allows the river to carry more water, which means better protection in most circumstances but potentially greater impacts for nearby properties if the stopbank is damaged during an extreme flood
- Extent of strengthening could be significant as erosion can occur anywhere along the stopbank system
Note the options included here are for the part of the river that extends from the Ōkūkū confluence to Rangiora Railway Bridge. We will share design options for downstream areas later in 2026. You can add comments directly to these options or give your feedback via the give feedback section of the page.
Please note that comments you make in this section will appear publicly, so please protect your personal privacy and the privacy of others. Do not share personable or confidential information in this section.
Please remain polite and respectful of others and their opinions. We may remove content that contains: Racism or hate speech, disrespectful, rude, or abusive language, threats to another person or organisation, including us and our employees, potentially defamatory statements, spam or links to external sites, off-topic information irrelevant to the thread, obscene, offensive, harassing, or discriminatory content toward any person or organisation, including us and our employees.Thank you for your contribution!
Help us reach out to more people in the community
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No thanks