Part 2: Understanding the impacts and risks of a changing climate

2.1
Climate-related actions are likely to be more effective if they are based on an understanding of how climate change will affect councils and communities. We looked at how the four councils were informing themselves about the impacts and risks of a changing climate.

2.2
We expected to see the councils ensuring that they had a robust understanding of current and likely effects of a changing climate for their region and the potential impacts on council infrastructure and their communities.

2.3
We found that all four councils have taken steps to be informed about the current and likely impacts of a changing climate on their infrastructure and communities. These steps included commissioning expert advice and, for councils that have in-house expertise, carrying out their own modelling. Two councils – Nelson City Council and Christchurch City Council – use an interactive online risk mapping tool to identify and communicate climate-related risks. These types of tools could be useful for other councils.

All four councils have taken steps to be informed about climate-related impacts and risks

2.4
All four councils have taken steps to understand the current and likely impacts of a changing climate on their infrastructure and communities. The climate change risk assessments completed provide a good basis for the councils to work with their communities to develop priority responses to risks for the short, medium, and long term.

2.5
All four councils have taken steps to supplement climate and sea-level rise projections provided by organisations such as the National Institute of Water and Atmospheric Research (NIWA) with other information. All councils have commissioned climate change risk assessments for their specific region or locality.

2.6
Environment Canterbury commissioned, in partnership with the Canterbury Mayoral Forum,¹ the Canterbury Climate Change Risk Assessment. The risk assessment, published in 2022, rates climate-related risks in 11 domains: biodiversity, water, infrastructure services, energy, prosperity, well-being, equity, sense of community, historic heritage, knowledge, and governance.

2.7
Environment Canterbury also commissioned its own organisational climate change risk assessment, focusing on how climate change might affect Environment Canterbury's operations.

2.8
Environment Canterbury carries out its own flood modelling. This modelling explicitly considers the effect of climate change scenarios on sea-level rise and rainfall in severe weather events.

2.9
Christchurch City Council supplemented the Canterbury Climate Change Risk Assessment with its own climate change risk screening for the Christchurch district. This risk screening considers risks across both the natural and built environment. It provides, for each locality, a level of detail that is not available in the Canterbury Climate Change Risk Assessment. It includes analysis of impacts and the implications of changes in factors such as temperatures, sea levels, rainfall, and wind.

2.10
Christchurch City Council also commissioned a detailed Coastal Hazard Assessment to provide updated information about the potential effects of coastal erosion, coastal flooding, and rising groundwater, and how this might change over time with sea-level rise. This information has fed directly into the Council's Coastal Hazard Adaptation Planning (CHAP) programme. Again, the analysis provides additional detail to what is included in the wider regional assessment.

2.11
Nelson City Council's risk assessment – prepared in partnership with Tasman District Council – takes a similar approach to that of Christchurch City Council. It considers the impact of a changing climate across five "well-being domains" on eight distinct geographic areas. These localised approaches recognise that climate risks and capacity to adapt can vary significantly throughout a region.

2.12
Whanganui District Council's local climate change risk assessment was still being prepared at the time of our audit. Whanganui District Council's risk assessment is expected to initially focus on council assets. Subsequent work will cover the wider community and district. Horizons Regional Council commissioned a wider, regional Manawatū-Whanganui Climate Change Risk Assessment in 2021. However, like Christchurch City Council, Whanganui District Council recognised that it needed a more detailed and localised risk assessment.

2.13
Whanganui District Council also carries out modelling of severe and frequent rainfall events caused by climate change. This modelling has helped the Council to assess and confirm priorities in its stormwater management programme. The Council has also identified where it needs further specific data, especially on how sea-level rise will affect the Whanganui River.

Christchurch City Council and Nelson City Council are using an interactive online risk mapping tool

2.14
Both Christchurch City Council and Nelson City Council are investing in an online risk mapping tool to help them understand climate-related risks at a more detailed and local level. This tool is tailored to each council's territory, infrastructure, and community. It provides detailed hazard impacts and vulnerabilities for different scenarios, including erosion, sea-level rise, coastal flooding, and earthquakes.

2.15
Both councils use the tool in their coastal hazard adaptation planning work. The tool helps with community engagement on climate-related impacts and risks by showing their vulnerabilities to a changing climate. It also helps the councils to design and prioritise climate responses.

2.16
Christchurch City Council used the tool to inform work on its housing portfolio and to help rūnanga understand the vulnerability of their assets to coastal flooding over time. We were told that the Council has also used the tool to inform long-term planning for council assets and in preparing its 2024-34 LTP. We were also told that the Council has agreed through the 2024-34 LTP to invest in further developing the tool. The Council anticipates that the extra investment will allow for additional hazard models and vulnerability assessments to create a "one-stop shop" for understanding climate risks.

Other councils might find these types of tools useful

2.17
We understand that each council's version of the online risk mapping tool has data relating to hazards and assets only within that council's boundaries. For example, Christchurch City Council staff told us that their tool showed rūnanga asset vulnerability in relation to only the Council's own information and geographic boundaries. Staff were aware – and concerned – that information about rūnanga assets might be missing or incomplete when those assets extend into a neighbouring council's boundaries.

2.18
This example highlights an opportunity for councils to work together on tools that are jointly populated with local information to provide better information to communities and to inform regional adaptation planning. We were told that councils in Canterbury were already collaborating using the online mapping tool.

2.19
Nelson City Council is also investing in an online risk mapping tool in partnership with neighbouring Tasman District Council.

2.20
There is clear benefit in the wider use of these types of tools. Other councils that are beginning climate-related risk identification might want to find out more about Christchurch City Council's and Nelson City Council's experiences and consider whether there is benefit in using similar online risk mapping technology, potentially in collaboration.

1: The Canterbury Mayoral Forum comprises the mayors of the 10 territorial authorities in Canterbury and the chairperson of Environment Canterbury. The Forum's functions include being a mechanism for councils in Canterbury to identify and prioritise issues of mutual concern and foster co-operation, co-ordination, and collaboration to address them. The Forum meets quarterly and is supported by a permanent secretariat hosted by Environment Canterbury. The mayoral body is supported by a Chief Executives Forum and technical working groups comprising staff in the member councils. A Climate Change Working Group, for example, co-ordinates climate change policy work among the 11 councils.