Te Hapū o Ngāti Wheke Inc is the Papatipu Rūnanga legal entity that represents Ngāti Wheke, the hapū with manawhenua status over the Whakaraupō basin and surrounding areas as outlined in the Port Cooper Deed. This entire area is culturally significant to Ngāti Wheke and sustains the hapū. Te Hapū o Ngāti Wheke has a strategic plan, a key part of which is the protection and enhancement of the whenua, moana and awa. Ngāti Wheke hopes to be a part of the leadership in climate action for future generations.

Mō tātou, ā, mō kā uri ā muri ake nei.

For us and our children after us.

Christchurch City Council recognises the rangatiratanga of Ngāti Wheke over its whenua and is working in partnership to plan for impacts on public assets and places of value.

Small sections of the Governors Bay-Teddington Road are at risk of coastal hazards. This road is part of a network that provides access between the city and communities around Whakaraupō Lyttleton Harbour and Koukourarata Port Levy.

The Allandale landfill contains household rubbish that was dumped directly onto an area of mudflat. The landfill is about 1.4 hectares in size and was used from the mid-1960s to 1993, when it was officially closed, covered, and planted over. Rock armouring was built along the coastal edge of the landfill in 2010 to protect it from erosion. The land underneath the parking area to the south of the landfill is also expected to contain some waste material because of how close it is. This area isn’t protected by a rock wall, so we check the coastal edge of the parking area on a regular basis to make sure no old waste has been uncovered.

The inter-tidal mudflats and remaining saltmarsh, found at the head of Whakaraupō in Allandale, hold significant conservation value and potential. Saltmarsh ecosystems are nationally rare and threatened because humans have changed many of the natural environments they exist in. There’s an opportunity to restore the saltmarsh in this area, enhancing its ecological value.

The inter-tidal mudflats provide important habitat for a range of seabirds, including the second-largest flock of Bar-Tailed Godwits and South Island Pied Oystercatchers, making them of national importance. The mudflats also make up the largest area of inter-tidal habitat in Waitaha Canterbury. The area has a rich cultural past and is important to mana whenua as a place of mahinga kai.

Allandale has several community facilities, including:

The Governors Bay Foreshore Track is a scenic walkway that follows the coastline, connecting Allandale to Governors Bay. The walkway has historical and cultural significance, having been built by prisoners of Parihaka in the mid-1800s while they were imprisoned in the area. The walkway is protected in many areas with rock armouring, parts of which are collapsing and in need of repair, but other areas have no armouring at all. There are plans to strengthen some of these at-risk areas, but this will focus on existing issues rather than long-term protection.

Allandale Hall was built in the early 1900s, extended in the 1970s, and extensively repaired after the Canterbury Earthquakes. It has mainly been used as a function space by locals and other Christchurch residents about a dozen times a year, and is valued for its scenic, rural setting. However, the hall is currently closed for health-and-safety reasons because a lack of airflow under the floor has caused the floorboards to become rotten and mouldy. It’s expected that the high groundwater table has also added to the problem. A decision is yet to be made about if and how the hall will be repaired.

The hall sits on Allandale Domain, a large, grassed area that was once used as the Diamond Harbour rugby grounds. The domain is now mainly used for recreation, dog-walking and as a pitstop to stretch the legs and use the public toilet which is separate to the hall. The domain is low-lying and can get very wet during heavy rain and storms. The coastal edge of the domain will naturally start to turn back into wetland and saltmarsh as sea levels rise.

Coastal flooding, coastal erosion and rising groundwater all pose a risk to Allandale. The images below show that as sea levels rise, the area will experience deeper flood events over a larger area. The water may also stay around for longer as groundwater levels rise and it gets harder for surface water to drain away into the soil. Areas at risk of erosion are likely to lose land at a faster rate as sea levels rise.

It’s important to note that while we have a good understanding of how coastal hazards will impact us, it’s hard to predict the rate at which sea levels are going to rise further in the future. The rate of change will depend on global greenhouse gas emissions and what impact this has on our climate. If different tipping points are reached, it’s possible we’ll see sea levels rise much more quickly. That’s why it’s important to have a plan in place for the future of our coastal communities.

The historic landfill, Allandale Hall and domain, the walkway, and a section of the Governors Bay-Teddington Road are all vulnerable to coastal hazards. If nothing is done, coastal hazards will cause the front of the landfill to erode, releasing contaminated material into the harbour. The road and foreshore track will flood, causing the road to close more regularly and increasing maintenance costs. The Allandale domain will be eaten away by erosion along the shorefront, and a combination of rising groundwater and more frequent flooding will mean the domain and Allandale Hall will become increasingly damp.

The Coastal Panel has considered the workable options that would address the risks to each of these assets. These options are set out in the section titled ‘Adaptation pathways’.

Sometimes the way we decide to manage one asset will have an impact on how the other assets could be affected by coastal hazards and the options we have available to manage those risks. In Allandale, decisions to protect the landfill or foreshore track could have an impact on the road and the neighbouring domain and hall.

1. Hold the line

We could protect the at-risk foreshore track, parking area and landfill. This option could be used to buy a bit more time or a lot more time, depending on how much is invested. A decision could then be made to switch to a ‘work with nature’ approach and move away from coastal hazards.

A ‘hold the line’ approach would likely involve repairing, improving, and extending the existing rock armouring in this area to protect against erosion and potentially raising the surface of the road and foreshore track above future flood levels. These measures would not solve the risk posed by flooding for all assets, or rising groundwater, and may need to be supported by improved culverts and drainage.

Extending the hard edge along the shorefront would have an impact on the natural environment, preventing the mudflats and saltmarsh from migrating inland as sea levels rise and conditions change. Armouring one section of the shorefront would also have an effect on the neighbouring land, causing Allandale domain to erode faster. Protection of the domain itself isn’t proposed as an option.

The Allandale Hall and public toilet could be maintained for some time, depending on whether the existing issues with the hall were repaired and how much was invested. The options to manage coastal hazard risk to the hall are the same under both the ‘hold the line’ and ‘work with nature’ approaches. They include removing the hall and replacing it with a different type of outdoor structure, building a new hall in a new location, or simply removing the hall.

2. Work with nature

In time, it may be better to remove the landfill and work towards creating a natural shoreline that supports the ecological values in the area. This approach could be used when it becomes too hard and expensive to maintain the existing armouring along the shorefront of the landfill – likely at least 10 years from now – or when a ‘hold the line’ approach becomes less effective.

This approach would avoid hard-protection options along the coastline, meaning the foreshore track would need to be moved or closed at a point in time – perhaps in the next 20 years – when it becomes unsafe to use. The at-risk sections of road could be flood-proofed and protected as discussed above, or possibly moved out of the hazard zone, although this would mean a significant amount of work and investment.

Removing hard edges and infrastructure from along the coast would allow it to function naturally again. Native saltmarsh and wetland ecosystems could be regenerated, enhancing the ecological values in the area.

To best align with a ‘work with nature’ approach, Allandale Hall would be removed, a new hall built in a new location, or the hall could be replaced by a facility that worked better with the surrounding environment. Options to adapt the hall are the same as those described under the ‘hold the line’ approach.

Both of these approaches come with their own opportunities, risks and costs, and they may need to be used at different times or could be more appropriate for some assets than others. Regardless of what we do, it’s going to get harder, more expensive and environmentally disruptive to keep public assets in this area, particularly near the shorefront where coastal erosion, flooding and groundwater all pose a risk.

Maintaining the at-risk sections of Governors Bay-Teddington Road is expected to become harder and more expensive over time. The adaptation pathway map below shows that at a certain point – likely around 20 to 30 years from now – changing conditions will mean a decision needs to be made to avoid increasing costs and disruption. As we near this point, we could look to flood-proof the road to different levels to buy us a bit more time or a lot more time. Alternatively, we could move the road straight away, or wait until a point in time when flood-proofing doesn’t work as well, and then move it.

*We don’t yet have enough information to understand exactly what the cost of this option would be.

Maintaining the walkway in its current state is expected to become much harder and more expensive over time. Because of its location between the ocean and steep slopes and cliffs, we can’t keep maintaining the walkway forever without having a significant impact on the natural environment. In as soon as 20 years, the increasing maintenance costs and impacts of coastal hazards will mean we need to make a change.

As we near this point, we could look to flood-proof and armour the walkway to different levels to buy us a bit more time or a lot more time, depending on the type and scale of work. Alternatively, we could look to relocate the walkway in the first instance, or at a point in time when the flood-proofing and armouring becomes less effective. Alternatively, we could look to close the walkway at the point when defences start to fail and the relocation option proves to be too difficult or costly.

*We don’t yet have enough information to understand exactly what the cost of this option would be.

Maintaining the landfill with its current defences is expected to be possible for around 10 to 20 more years, then it’s only going to get harder and more expensive. As we near this point, the existing armouring could be improved to different levels to buy us a bit more time or a lot more time, depending on the scale of work. Alternatively, the landfill could be removed straight away, or at a point in time when the armouring isn’t as effective.

*We don’t yet have enough information to understand exactly what the cost of this option would be.

As sea levels rise, we expect the domain will be increasingly impacted by coastal flooding, rising groundwater and coastal erosion.

The adaptation pathway map below helps to show that while the existing sports field might continue to function for a time, nature will eventually take its course and the area will become damper and more difficult to use. The decisions the Coastal Panel is considering are whether to actively encourage the regeneration of the area, and at what point. It could be straight away, or it could be once the sports field can no longer be used and maintenance becomes too difficult. These decisions are something we want your feedback on because they’ll influence the way the area can be used.

*We don’t yet have enough information to understand exactly what the cost of this option would be.

Allandale Hall is currently closed for health-and-safety reasons. Fixing these issues will cost between $40,000 and $400,000, depending on how much work is completed and how long the hall is intended to be kept in use. Because of its age, condition and location in a hazard-prone zone, it may be hard to justify investing in these repairs, let alone the investment needed to keep the hall its location once it’s at risk from coastal hazards.

Coastal hazards are unlikely to significantly impact the hall for another 20 to 30 years because of its elevation and distance from the coast. If the issues are fixed, then the hall could likely stay in its location over this timeframe. However, high groundwater levels and rainfall-related flooding affect the hall already. Because it’s used as a function venue, the state of the surrounding grounds will likely have an impact on how often it gets used and what it can be used for.

The adaptation pathway map below helps to show that if a decision is made to repair the hall, we’ll still need to take action at some point to address the risk posed by coastal hazards. This action will be needed sooner if the hall isn’t repaired. Options to reduce the risk of coastal hazards include replacing the hall with a different kind of facility that’s more resilient to future flooding, such as an outdoor shelter. Alternatively, a decision could be made to build a new hall outside of the hazard zone, or to remove the hall straight away, or at a point when the other options become less effective. Moving the hall would likely involve building a new hall in a different location and removing the existing hall.

*We don’t yet have enough information to understand exactly what the cost of this option would be.