Opinion: Coastal hazards report helps us plan, invest, adapt

Published 02 Mar 2022

An updated coastal hazard assessment for the Kāpiti Coast will provide information to help us plan how we might respond to future sea level rise. The Council’s Group Manager, Infrastructure Services, Sean Mallon, talks about why Kāpiti needs the information in the new report.

It’s Council’s job to plan where and when we invest in maintaining, repairing, or building new public infrastructure. In our coastal areas these are things like stormwater pipes, beach accessways, roads, parks, wastewater pumping stations and seawalls. Some are big-budget items that take years to plan and pay for. To do it well, we need good data and reliable projections about what the locations for those assets might look like in 30, 50 or 100 years. Otherwise we risk wasting ratepayers’ money. Your money.

The updated ‘coastal hazard susceptibility and vulnerability assessment’ helps us understand what we’re dealing with so we can start to plan and adapt effectively.

Kāpiti was one of the first councils in New Zealand to recognise the need to plan for the effects of climate change on our coastline. We saw the inevitability of parts of our coast being more and more frequently damaged by erosion and coastal flooding.

Our first attempt hit some speed wobbles. A review in 2014 found our approach was sound but questioned some of the technical aspects. Those have been addressed this time round. We’ve been able to follow the Coastal Hazards and Climate Change Guidance for Local Governments issued by the Ministry for the Environment (MfE) in 2017. And we’ve learned from the experiences of other communities who have done coastal hazard mapping.

Taking more time to work through this process, keep the community informed and obtaining two independent peer reviews prior to the release of this report, are further lessons learnt from the previous hazard assessment work.

The updated assessment focuses on coastal erosion and flooding – two coastal hazards that the MfE guidance recommends as baseline information. The report is based upon the best available data, guidance and modelling we currently have available for Kāpiti. We’ll continue to update this information as we collect more data, and as our knowledge around sea level rise and coastal responses to climate change evolves.

Further information will come from the NZ SeaRise Programme which will be issuing New Zealand-specific vertical land movement and sea level rise data later this year. When that’s available we’ll be looking at how it could affect the projections in the report. Fluvial flooding (from rivers and rainfall) is being addressed in a separate programme of work we’re doing to update our flood hazard maps. We currently don’t have reliable groundwater information for our district but that too can be added to the mix as local data improves. The Government’s RMA reforms are also expected to address climate change planning but that could be another two years away.

Without releasing this report now:

Council infrastructure will face repeated repairs and rebuilds;
people will continue to invest in land that will likely be subject to coastal erosion or flooding; and
our community cannot start to plan for the changes we can expect to see in the future due to climate change.

This is not only illogical but also unsustainable and unfair on our community. We shouldn’t continually delay waiting for ‘perfect’ information. That will never be available. We need to get on with it.

Read the report at www.kapiticoast.govt.nz/coastal-science. 

Uses for coastal hazards data

Kāpiti now has good information about how coastal erosion and flooding is likely to affect our future shoreline so what next?

Our first goal has to be to raise public awareness about the nature and likely extent of these coastal hazards which are the result of climate change and sea level rise. Our community needs this information to start a conversation on how we respond to these hazards.

Council will use the information to manage our coastal infrastructure and assets responsibly and cost-effectively. The report will also provide essential base hazard data for future district planning.

People who own or want to buy property in the district will have full information about coastal hazards, just like the information they currently have access to on flooding, earthquakes, and tsunamis that affect our district.

Read the report at www.kapiticoast.govt.nz/coastal-science.

Why we look at extremes

We need to consider the full range of possible scenarios to assess whether we are doing enough to invest wisely and adapt to climate change.

The Ministry for the Environment’s 2017 climate change planning guidelines for councils, tells us to consider the total range of international greenhouse gas concentration trajectories (called RCPs), from RCP2.6 to RCP8.5+. These describe different climate futures, all of which are considered possible depending on the volume of greenhouse gases emitted globally in the years to come.

The guidance says the upper scenarios need to be considered by decision-makers to ‘stress test’ greenfield development (new suburbs or towns) or major new or upgraded infrastructure projects to be sure they won’t be affected by coastal hazards during their anticipated lifetimes.

It’s the right thing to do when we’re spending millions of dollars on developments that we want to last many, many decades.

We’re in this together

Council made a commitment to our community to work on coastal challenges in its 2018-2038 and 2021-41 long-term plans because they affect the services and lifestyle of our whole district and impose costs on all of us. The new technical report on coastal hazards affecting Kāpiti is part of that commitment.

Locally, public awareness about the need to plan for the impacts of climate change is increasing thanks to the efforts of groups like Schools 4 Climate Action and Low Carbon Kāpiti.

Nationally, the need to plan for coastal change is gathering pace. In 2017 the Government provided guidance for councils on planning for climate change. The Climate Change Commission, the Insurance Council of New Zealand, and the media have done a lot to highlight the need for communities work together on how to respond and adapt to coastal hazards like erosion and flooding.

What it means to ‘adapt’

With updated information on where and when we are likely to experience coastal hazards, we can start to talk about how we might adapt. There are five main approaches but it’s likely we’ll need a combination of these:

Maintain – we do what we’re doing now but increase our emergency response capability and raise community awareness.
Accommodate – we live with the hazard but use mechanisms like requiring higher floor levels or relocatable new buildings.
Protect – we keep the hazard away using engineering solutions such as dune planting or seawalls.
Retreat – we move away from the hazard, perhaps using options such as buyouts, land swaps or leasebacks.
Avoid – we don’t move into the way of the hazard in the first place e.g. through land zoning or setbacks to prevent development in that area.

Keep up to date with our coastal adaptation project at Takutai Kapiti - Have Your Say