New report assesses coastal hazards risk

The challenges communities face in adapting to climate change are highlighted in a new report assessing the coastal hazards across Christchurch and Banks Peninsula.
The report was prepared by environmental and engineering consultancy Tonkin & Taylor Limited and contains the most detailed and up-to-date information on coastal hazards facing the communities within the Christchurch City Council’s boundaries.

A new report assessing the likely impact of coastal hazards in Christchurch and Banks Peninsula has been released.
It will be formally presented to the Council at its meeting on Thursday 9 November.
The 2017 report is the end result of a thorough and independent peer review of an earlier report, the 2015 Coastal Hazard Assessment Report.
“A peer review panel made recommendations to improve the 2015 report. This new report addresses all those recommendations and includes the findings of further investigations,’’ says Christchurch City Council Head of Strategic Policy Helen Beaumont.
“It will be a starting point for a conversation with our community about how we are going to adapt to the realities of climate change, particularly sea-level rise and increased storminess. It will also help inform any future changes to the coastal hazard provisions in the Christchurch District Plan,’’ Ms Beaumont says.
Climate change is expected to accelerate sea level rise and the New Zealand Coastal Policy Statement requires Christchurch City Council to consider coastal hazards over the long term – at least 100 years.
The 2017 report covers the key inhabited coastal areas within the Council’s boundaries and investigates the potential for erosion and inundation (flooding by the sea) over a 50-year and a 100-year timeframe for four climate scenarios.
The report classifies the areas into two coastal environments:
• The open coast, which stretches 16km from Waimairi Beach to Southshore, and also includes Sumner and Taylors Mistake.
• The harbour coast, which takes in the Avon-Heathcote Estuary, Brooklands Lagoon and the Banks Peninsula harbours.
The 2017 report shows the harbour coast is more at risk of inundation than the open coast, which is generally protected by sand dunes.
Where can I find more detailed information?
You can read the full 2017 Coastal Hazard Assessment for Christchurch and Banks Peninsula report here(external link) along with a summary of the report.
How can I find out if my property is likely to be affected by coastal hazards?
A property search tool will be available at www.ccc.govt.nz/livingwithwater(external link) after the Report is received by the Council on 9 November.
What difference is climate change going to make to our coastal areas?
We’ve produced a short Coastal Hazards 101 video to help explain this.
Canterbury has an accreting (building out) coastline, why does the report say it will erode?
The southern Pegasus Bay part of the Canterbury coastline is currently accreting. Shorelines undergo continuous cycles of accretion and erosion. Our open coast in Christchurch is dynamic. Coastline monitoring indicates most of the coastline is currently accreting while some is stable or slightly eroding. Short-term erosion is normally associated with storm events.
However, the very long-term trend is of a shoreline moving further inland, and this is the trend we need to plan for. With climate change, along with sea-level rise, more frequent and severe storms are expected with significant coastal flooding during storm events and progressive erosion of the estuaries, harbours and the open coast.
Will information from the updated report go on Land Information Memorandums (LIMs)?
The Council is required by the Local Government Official Information and Meetings Act to include hazard information in a LIM if it is known to us. Once the 2017 Report is received by the Council on 9 November, LIMs will be updated to reflect this information. From this date, when a LIM is applied for on a property within areas the report identifies as potentially impacted by coastal hazards, the LIM will state:
“The Council has a report, Coastal Hazard Assessment for Christchurch and Banks Peninsula (2017) that indicates this property or part of this property may be susceptible to coastal inundation (flooding by the sea) and/or coastal erosion over the period to 2120. The 2017 report considers four sea level rise scenarios. A copy of the 2017 report and other coastal hazard information can be found at www.ccc.govt.nz/coastalhazards.”
What does the new information mean for building and rebuilding in these areas?
Under the Building Act 2004 a building consent application must take into account all conditions that may apply to the site and demonstrate that the building work will comply with the building code. In this case, the 2017 Report shows coastal hazard conditions that need to be considered by the designer of the home and assessed by the Council, (as the district’s building consent authority) as part of a building consent.
The 2017 Coastal Hazards Report is designed to help the Council with planning. It looks broadly at areas and how they might be impacted by the hazards. Staff assessing building consents for properties in these areas would refer to the Report to flag that coastal hazards need to be considered. They would likely need to check that the designer of the home has considered the issue on a site specific basis as a part of assessing a building consent in these areas.
If someone wanted to rebuild, or do a major alteration (including full foundation repair) in a coastal hazard area (as identified in the 2017 report), their building consent application would need to show that they can adequately protect the land, the building and other property from the hazardous conditions, in this case, coastal inundation or erosion. It's important to note that the Council, as the consenting authority, cannot offer design advice. People would need to seek this advice from a designer.
If they can't show there will be adequate protection from the hazard, a building consent may sometimes be issued, with a section 73 notice (hazard notice). If someone chooses to construct a building that complies with the building code but does not (or cannot) mitigate the hazard to the surrounding land, a hazard notice allows an owner to take the risk of building on that land, with the territorial authority (the council) protected against legal liability for this risk. The hazard notice goes on the certificate of title.
The Christchurch District Plan already identifies many of these coastal inundation areas as High Flood Hazard Management Areas because of the potential risk to people’s safety and property as a result of predicted flooding depths greater than 1metre. The District Plan requires that new developments or intensification of land uses in these areas are to be avoided. This is to limit the exposure of residents to known future hazards as required in ECan’s Regional Policy Statement. Resource consent may be issued for uses which do not increase the present intensity of land use in the High Flood Hazard Management Areas. The District Plan(external link) and the High Flood Hazard Management Areas can be viewed online at http://districtplan.ccc.govt.nz/(external link).
How does the coastal hazard information relate to river flooding?
The Report looks at the risk of coastal inundation or flooding. Within the urban area of Christchurch city these areas have already been recognised as susceptible to flooding from a combination of rainfall, river and coastal inundation. These areas are mapped in the Christchurch District Plan as Flood Management Areas or High Flood Hazard Management Areas (as above).
What will this mean for planned new Council developments in coastal areas, like the New Brighton hot pools?
The 2017 report is the latest in a series of four reports commissioned by the Council since 1999 to help gain a comprehensive understanding of the effects of climate change, including sea-level rise and the increasing frequency and severity of weather events. All this information has been, and will be used, as we plan the maintenance, repair and rebuild of the Council's infrastructure and facilities in coastal areas, to make sure the risk from these hazards is considered.
Will property values in the coastal hazard areas drop and will it become more expensive to get insurance?
The Council is providing insurance, banking and real estate industry bodies with information on the new report to help them understand the nature and extent of coastal hazards. Having good clear information allows insurers, banks and the market to respond appropriately to the actual risk.
How can I get involved in the conversation about coastal hazards and how we can adapt to them?
The Council will be working with communities to have these important discussions. And in Southshore and South Brighton, we will work with Regenerate Christchurch, as they lead adaptation planning through the Regeneration Strategy for these areas.
In coming weeks we will hold drop-in sessions in coastal areas where people can come and discuss the report with Council staff and technical experts. Keep an eye on www.ccc.govt.nz/livingwithwater(external link) for more details on this.
Email livingwithwater@ccc.govt.nz with your name and address and we’ll keep you updated on ways you can be involved, including details about events in your area.

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