Earthquake legacy project

Underpinning the Earthquake Legacy Issues Project is the acknowledgement that earthquake legacy issues have had, and continue to have, a significant impact on community wellbeing in Southshore and South New Brighton.

It was clear from community feedback we received that people felt very strongly about addressing earthquake legacy issues first, before starting a conversation about coastal hazard adaptation planning.

The purpose of the Earthquake Legacy Issues Project was to investigate and develop responses to earthquake-rated changes to the estuary edge in Southshore and South New Brighton.

Examples of earthquake legacy changes:

• If it’s in relation to inundation (flooding), we mean changes in the level of service that was provided prior to the earthquakes. For example, the level of flood control that was in place.
• If it’s in relation to erosion, we mean damage to existing structures as a result of the earthquakes.
• If it’s about land damage from the earthquakes, we mean changes to land elevation and damage to land, such as lateral spread.
• And if it’s about groundwater, we mean changes in groundwater levels.

Options to address earthquake legacy issues need to be practicable, feasible and not compromise the range of options available to the community when the Coastal Hazards Adaptation Strategy project begins.

For the Council, practicable and feasible would mean the best options for preventing or minimising the adverse effects on the environment and complying with the Council’s regulatory, operational, budgetary, and benefit/cost requirements.

The options also need to address outstanding community needs.

During May and June  2019 we worked with the South New Brighton and Southshore communities to identify a long list of community needs relating to earthquake changes to the estuary edge. We collated and themed the needs, and came up with some draft statements that were published for comment. With the help of some community representatives, and using the feedback we received, we then finalised the community needs.

These needs were used to help assess options to respond to the earthquake-related changes to the estuary edge.

Related documents:

• Full list of community needs identified at workshops [PDF, 419 KB].
• Feedback received on draft community needs [PDF, 952 KB].
• Finalised themes and community needs [PDF, 378 KB].

Timeline

About the area

Land in this area dropped after the earthquakes, which has increased both the risk of flooding and the effects of shallow groundwater. 

While remediating earthquake-related land damage is the Earthquake Commission’s responsibility(external link) Council has mitigated the increased flood risk by raising and repairing stopbanks in this area.

The stopbanks are now at a level of RL 11.4m, which is higher than was provided before the earthquakes and consistent with, or higher than, other parts of the Ihutai/Estuary.

However, we know that if the river was to exceed the height of the stopbanks, the consequence to people and property is now greater. This is because the land is lower on the landward side of the stopbank, which increases the potential depth of floodwaters.

Latest project update

At the end of 2019 we commissioned GHD to provide an updated risk-to-life assessment of the stopbanks between Pages Road and Bridge Street, to account for the updated 2018 high tide statistics. The risk-to-life assessment is being done using the ISO 31000 risk framework. 

Once the report results are finalised we will publically release the report and communicate the outcomes of the assessment to the South Brighton community.

Proposed option for the area:

• Phase One: Investigate stopbank condition and safety [PDF, 629 KB]

This option addresses the following community need:

• Ensure that stopbanks are well-constructed and do their job of keeping people safe from flooding.

Community feedback on the option and Council decision

In total 45 residents provided feedback with 54% agreeing that this option responds to the earthquake legacy issues identified by the community. 

In their comments, people indicated that they wanted assurance that any remedial actions would be addressed, and they raised concerns that this work had not progressed more rapidly.

The option included in the report to Council on 29 August 2019 was to undertake a stopbank condition assessment and an update of previous investigations into the life-safety risk of flooding from a breach or overtopping of the stopbanks between Pages Road and Bridge Street to account for the updated 2018 high tide statistics and to report the result of that investigation to the Council and the community.

On 29 August 2019 Council decided to request staff to undertake the assessment.

About the area

South New Brighton Park, between Beatty Street and the boardwalk, is the part of the Project Area that is the most affected by tidal flooding and erosion.

While this area experienced flooding and erosion before the earthquakes, the earthquakes have caused the land to drop in places, and some of the existing erosion protection structures have moved. This has led to further erosion and flooding of the edge.

The assets most at risk from these changes are the existing tracks and the Reserve land. However, there is also a potential increase risk from flooding to low-lying Estuary Road properties and the South New Brighton Holiday Park and Tennis Club.

There is little evidence of erosion north of Beatty Street, and the area is well planted. Land that has dropped along the estuary edge has potentially increased the flood risk to low-lying properties in Seafield Place and north of Bridge Street, but the level and extent of this risk have not been fully investigated.

The boardwalk in South New Brighton Park and adjacent embankments have been repaired to the pre-earthquake condition. South of the boardwalk to Caspian Street there are no obvious or outstanding earthquake legacy issues.

The Ebbtide Street stopbank and rock wall have been repaired to respond to earthquake damage and provide a consistent level of service as existed before the earthquakes.

Latest project update - November 2020

Since August 2019 we have constructed the southern and northern sections of a bund in South New Brighton, between Bridge Street and South New Brighton School.  Work on the middle section of the bund will be completed in 2021 following the bird-nesting season.

For the estuary edge from the Yacht Club to the boardwalk, the August 2019 Council resolution was to restore using reno mattresses and gabion baskets as previously existed pre-earthquake.

We looked at both reno mattresses and a cobble beach approach to restoration. In the end, we determined the cobble beach was the preferred option and best met the intentions of the Council resolution. Both options would achieve pre-earthquake levels of erosion management, but the cobble beach is better because it:

• Is easier to repair and maintain.
• Has a shallower slope which reduces the potential for its base to erode.
• Can be adapted for sea-level rise.
• Enables easier to access the shoreline,
• Creates a more naturalised edge
• It will help restore the salt marsh in the area,
• Is more consistent with the Council’s Biodiversity Strategy and the South New Brighton Reserves Development Plan.
• Is more likely to be granted consent.

To address flooding in the area, we also now have Council approval to progress a bund set back from the estuary edge by 25-100m. Together with the Southshore Bund, this will reduce flood risk to 450 homes as well as the campground.

The next steps for both projects are to review the South New Brighton Reserves Development Plan, to enable this work to proceed. We are estimating work will start on the estuary edge and bund in early-mid 2022.

Proposed options for the area

• New bund close to the estuary edge with repair, replacement or infill of existing erosion protection structures [PDF, 632 KB], or
• New setback bunds (25 – 100 m from the edge) with repair, replacement or infill of existing erosion protection structures [PDF, 654 KB], or
• New setback bunds (25 – 100m from the edge) with re-contoured and planted estuary edge to develop sloping beaches [PDF, 633 KB]. 

These options address the following community needs:

• Protection from flooding from the estuary.
• Protect the estuary edge from further erosion.
• Protect the South New Brighton Park and Playground, South New Brighton School, South New Brighton Tennis Club, South Brighton Playcentre and the South Brighton Holiday Park from increased flood risk.

Community feedback on the options and Council decision

In total 110 residents provided feedback on these options with a preference for the set-back bund and sloping beach across all three questions asked. 

63% agreed or strongly agreed that this option responds to the earthquake legacy issues identified by the community, 66% agreed that this option would improve their quality of life, and 65% agreed that this option provided the community with a sense of confidence in their future.

However, a significant number of respondents also supported the option of a bund close to the edge with the repair of the existing protection structures (53% agreed or strongly agreed that this option responds to the earthquake legacy issues identified by the community). 

The recommended option included in the report to Council on 29 August 2019 was for new setback bunds with a range of hard and soft erosion management methods between Bridge Street and the boardwalk adjacent to the South New Brighton Park.

On 29 August 2019 Council decided to proceed with the following: 

• For the Estuary Edge, Bridge Street to Jetty area, acknowledge the current salt marsh and implement engineered set back bunds giving protection to the South New Brighton School and Seafield Place.
• For the Estuary Edge, Yacht Club to the boardwalk, implement restoration of the edge as per earthquake legacy edge repairs using reno mattresses and gabion baskets as previously existed pre-earthquake.
• For staff to report separately on any flood protection measures that may be required for the area, in the context of this report.

About the area

There have been changes to the estuary edge due to the land lifting in places, damage to some private protection structures, and some small areas where the land was lowered during clearance works.

Removal of residential red zoned properties along the estuary edge has left an area of open space which is largely being used for recreation and enjoyment but has not been enhanced or developed for this use.

Many of the private structures which provided varying levels of erosion and flood protection still provide a functional purpose in their current state. However, there are also sections which are unstable or have left exposed materials which create a health and safety risk.

There may be some increased risk to low lying properties on Rocking Horse Road adjoining the red zone due to changes to the estuary edge structures and the clearance of land where there used to be houses.

Any flood risk is largely managed through the bund which was constructed by Land Information New Zealand (LINZ) after the clearance works. Emergency works in July 2017 extended the bund across the road ends. There are some remaining low points in the LINZ bund on Crown land, otherwise a consistent level of protection of RL 11.2m is provided.

There are pockets where increased erosion is occurring immediately behind private protection structures increasing the risk to residential red zone land and parts of the LINZ bund where this is close to the estuary edge.

Latest project update

A collaborative working group has been established to develop a suitable erosion mitigation plan for Southshore. Jacobs, an engineering consultancy, has been contracted to provide the independent technical expertise and the Southshore Residents' Association has appointed Gary Teear as their community-nominated technical expert. Council staff form the third party in the Working Group. 

You can read more about project progress in the June 2020 Coastal Futures newsletter [PDF, 2.7 MB]. 

The Working Group is now in the process of finalising its report on the the various erosion management options. Once the report is finalised, it will be made publically available. 

Proposed options for the area

The proposed options to address flooding were:

• New set-back bund adjacent to houses along the residential red zone [PDF, 618 KB]. 
• Improve existing Land Information New Zealand bund. [PDF, 618 KB] 

These options address the following community need:

• Protection from flooding from the estuary.

The proposed option to address erosion was:

• Phase One: Investigate erosion and private structures [PDF, 633 KB]. 

This option addresses the following community needs:

• Protect estuary edge from further erosion.
• Repair of estuary-edge erosion protection, taking into consideration the protection that was previously afforded by structures that were privately owned.

Community feedback on the options and Council decision

In total, 141 residents provided feedback on the Southshore options and a large proportion of the community disagreed that either of the proposed flooding options met their needs. 

While 44% of respondents agreed that the proposed setback bund met their needs, 47% disagreed.  Only 31% agreed that improving the existing bund met their needs, while 59% disagree.

A higher proportion of respondents (66%) agreed that the proposed option to address erosion through an initial investigation met their needs, and 29% disagreed.

Sentiments raised at the Community Assessment drop-in, and reinforced by emails from the Southshore Residents Association and the Christchurch Coastal Residents United noted the following issues:

• An engineered bund is sought, but not set back as proposed and instead located where the LINZ bund is currently positioned.
• Erosion protection should be integrated with any proposed flooding solution.
• Residents are seeking immediate solutions to erosion and flooding for now and into the future.  However, there is some appetite for Council to undertake further investigation and then provide the community with an integrated flooding and erosion proposal.

While the proposed bunds were an appropriate response to the increased flood risk created by earthquake legacy issues, Council staff recognised that these options may not sufficiently address the community need for certainty and wellbeing. 

The recommended option included in the report to Council on 29 August 2019 was therefore, Phase one: Investigate immediate and longer term erosion options (including options for the edge structures) and advise on the position of the bund.

On 29 August 2019 Council decided to proceed with the following:

• Requests staff to investigate immediate and longer-term erosion options in Southshore (including options for the privately-owned edge structures).
• Requests that a collaborative group be established which includes a technical expert nominated by the Southshore community, to investigate the immediate Earthquake Legacy edge issues for the Estuary Edge repair and protection including the development of a suitable erosion mitigation plan with costings (including options for the formerly, privately-owned edge structures, and the position of the 11.4 m bund).
• Notes the above Southshore Erosion Mitigation Plan will be presented in the first instance to the Southshore Residents Association and the Coastal-Burwood Community Board for comment before presentation to Council in early 2020.
• Recommend that funding be made available for implementation of the estuary edge earthquake legacy repair in 2020 and urgently prioritised. 

In response to the community needs around recreation, access and enjoyment, we've proposed an option for this whole area:

Option: Continuous walkway/cycleway and enhanced recreation areas [PDF, 636 KB].

• Provide a continuous walkway/cycleway adjacent to the estuary, with occasional setbacks where required, to ensure that it is safe and not prone to regular flooding.
• Sections would be raised, repaired, finished, widened or rerouted.
• Community-led enhancement of the Southshore red zone to include picnic tables, plantings, and spaces to learn about and observe nature.

This option provides a continuous walkway/cycleway along the Ihutai/Estuary, which is occasionally set back from the estuary edge where required to ensure that it is safe and not prone to regular flooding. It would enhance the red zone land in Southshore through the addition of picnic tables, native plantings, and spaces to learn about and observe nature.

We will raise, repair, finish, widen or reroute the existing walkway/cycleway from Evans Avenue right down to south end of the red zone. In the future this cycleway could link to the Te Ara Ōtākaro trail.

The track will be finished to the Council standard track design - 1.5m wide, 75mm base layer of compacted gravel, topped with 25mm crusher dust, with timber edge.

The enhancement of red zone land in Southshore could be community-led through the application for a transitional use lease from Land Information New Zealand (LINZ) and there are opportunities to apply to Council for community grants funding.

This option will be broken into smaller projects, and staged so that some work could happen quickly.

Maintenance and levels of service

We’ve heard your concerns about how we maintain and care for the parks and public spaces in this area.

We’re reviewing our maintenance schedules to make sure this area is receiving the same level of service, and to the same standard as the rest of the city.

Recreation, access and enjoyment

The South New Brighton Reserves Development Plan(external link), which covers the four South New Brighton reserves has a whole programme of work around maintaining and enhancing the parks and reserves along the estuary edge, including some significant planting work.

We’re reviewing the Plan to make sure the timing of this work is prioritised and is well-coordinated with other work that may be happening in the area.

We also have an area-wide option for a continuous walkway/cycleway and enhanced recreation areas [PDF, 636 KB].

Stormwater management

There are no quick fixes to the stormwater issues in this area. Even before the earthquakes Southshore and South New Brighton were low lying areas that experienced issues with stormwater drainage.

Changes to the land from the earthquakes have only made this worse, as it has in other areas of the city. Read more about stormwater [PDF, 798 KB].

In the short term, we will be increasingly reliant on temporary pumping, as we are in other areas of the city, to manage stormwater.

We are reviewing our longer-term approach to stormwater management through existing Council programmes, and this is something that will be considered as part of adaptation planning for the area.

Coastal Futures newsletter

• Coastal Futures newsletter - November 2020 [PDF, 1.7 MB]
• Coastal Futures newsletter - June 2020 [PDF, 2.7 MB]
• Coastal Futures newsletter - February-March 2020 [PDF, 2.2 MB]
• Coastal Futures newsletter - 29 October 2019 [PDF, 2.1 MB]
• Coastal Futures newsletter - 26 July 2019 [PDF, 1.5 MB]
• Coastal Futures newsletter - 12 July 2019 [PDF, 1.1 MB]
• Coastal Futures newsletter - 21 June 2019 [PDF, 708 KB]

Community needs

• Finalised themes and community needs [PDF, 378 KB]
• Draft themes and community needs [PDF, 583 KB]
• Feedback received on draft community needs [PDF, 952 KB]
• Full list of all community needs identified at 29 May and 13 June workshops [PDF, 419 KB]

Options

•  Options suggested by the community - how they have been considered and assessed [PDF, 437 KB]

Fact sheets

• Flooding [PDF, 805 KB]
•  Stormwater [PDF, 798 KB]
•  Groundwater [PDF, 1.3 MB]
•  Stopbanks, bunds and other structures [PDF, 1.2 MB]
•  2018 new high tide statistics [PDF, 652 KB]
•  What is a 100 year flood [PDF, 182 KB]
•  Planning and approvals [PDF, 672 KB]
•  Life safety risk from stopbanks and flooding [PDF, 884 KB]
•  Christchurch Drainage Datum and other levels [PDF, 752 KB]
•  Pre and post earthquake levels of structures around the estuary - map [PDF, 2 MB]