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Coast

We live on a long narrow island with an abundant coastline. Coastal hazards have always been a part of our lives. However, with the changing climate, hazards are changing in their nature, magnitude, frequency and extent of their impact.

In 2020 the Hurunui District Council commenced a project to identify coastal hazards that are impacting Hurunui’s coastal communities and to understand how these hazards will change over the next 100 years. The project seeks to establish a long-term approach for managing the risk of coastal hazards at each of the settlements, in partnership with the local communities.

The project focuses on six small beach communities – Amberley Beach, Leithfield Beach, Motunau Beach, Gore Bay, Conway Flat and Claverley Beach – how these communities will take control of their future and how, as a community, they will adapt to the changing hazard risks over the next 100 years.

The project was based off the Ministry for the Environment’s Coastal Hazards and Climate Change Guidance (2017) but was scaled down and tailored to each settlement.

The project was carried out in four phases:

Image setting out the four phases of the coastal conversations project - Phase 1 - What is happening?; Phase 2 - What matters most?; Phase 3 - What can we do about it?; and Phase 4 - How can we implement the strategy?

Predicted sea level rise scenarios

The MfE Guidance identified four sea level rise scenarios based on differing green-house gases emissions:

  • RCP2.6 - low/ reduced emissions
  • RCP4.5 - moderate then declining emissions
  • RCP8.5 - continuing status quo high emissions
  • RCP8.5+ - continuing status quo high emissions and possible instabilities in the polar ice sheets

As time increases the uncertainty in sea level rise increases (Fig x). We can be fairly certain about the rate of sea level rise over the next 30 and 50 years – there is only a small difference between the highest and lowest sea level rise scenarios. There is much greater uncertainty when looking out 100 years or further.

The risks also changes over time – we know that we are expecting 1 in 100-year events to occur more frequently as sea level rises. What we consider a 1 in 100-year event today could occur every 15-30 years by 2050, every 6-12 years by 2070 and annually by 2120.

The Hurunui District Coastline Hazard and Risk Assessment considered how the hazards might change over a 30-, 50- and 100- year period under the RCP 8.5 and RCP 8.5+ sea level rise emission scenarios.

Council then presented these findings to each of the settlement, and together with the communities, worked through feasible pathways to mitigate the risks presented by the hazards identified for each community. Navigate to the individual beach communities below to learn about their story and what their plan is to manage the different hazards.

Navigate to the relevant tiles below to find out where the conversation is at with your community:

Dynamic Adaptive Pathways Planning Approach: having an adaptive plan

We cannot be certain of all the changes we will face from climate change, especially further into the future. However, doing nothing until we have certainty is not a viable option – by the time we have certainty it will be too late to adapt. Developing a plan early means we have the most options and opportunities available.

The Coastal Adaptation Plans were developed using the Dynamic Adaptive Pathways Planning (DAPP) approach, which looks at a series of actions over time, known as pathways, instead of locking ourselves in on a specific solution.

An adaptive plan allows us to prepare for the future despite its uncertainty. The multiple pathways that are designed to be dynamic and flexible allows decisions to be revisited as new and improved information becomes available.

The plan is trigger-based, not time-based. These triggers are agreed points where we will revisit our approach or change course. A trigger-based approach means that we don’t act until we need to, but we are well prepared to act when we do.

An example adaptive pathways map adapted from the Ministry for the Environment's Coastal Hazard and Climate Change Guidance 2017

Changing information

The maps and information in all the plans developed are derived from the information available in 2020. Since then, there has been regular updates to the scientific information and national policy guidance. This information has been reviewed throughout the project and does not significantly change the projected hazards. We will continue to periodically review new information and guidance as they arise, and the plans will be amended as required.

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