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Coastal hazard risk science

Council has commenced a review of the existing coastal provisions of its District Plan, including the “coastal building line” and “relocatable building area”[1]. This review will be informed by the best available information on coastal hazards.

This page identifies and provides a short introduction to sources of information known to Council about coastal erosion and inundation risk hazards in Kāpiti. This includes:

  • Information commissioned by different organisations, including Council, a community group, Greater Wellington Regional Council (GWRC) and the National Institute for Water and Atmosphere (NIWA).
  • Information about current risks, as well as modelled projections about future risks based on potential climate change scenarios.

This page will be updated as existing information is reviewed and/or new information comes to hand. If you have any enquiries about the information on this page, please contact the District Planning team at [email protected].

Council-commissioned science | Mapped projected coastal hazards | Community-commissioned information | Other information

Council-commissioned science

Council commissioned independent consultancy Jacobs New Zealand Limited to assess our district for coastal hazards, from Ōtaki in the north to Paekākāriki in the south. Their assessment updates previous coastal hazard assessments of the Kāpiti Coast District shoreline.

The coastal hazard assessments commissioned by Council to date include area-specific risk assessments and a susceptibility and vulnerability assessment. As explained further below, this work was completed in stages, starting with a methodology report released in 2021 (Volume 1), followed by a results report in 2022 (Volume 2), and risk assessments in 2024 (Volume 3).

At the time of their preparation, the assessments reflected both national and international best practice, and met the requirements of the New Zealand Coastal Policy Statement 2010 (NZCPS) and Ministry for the Environment: Preparing for Coastal Change. Guidance for Local Government. However, in response to more recent Intergovernmental Panel on Climate Change (IPCC) and Ministry for the Environment (MfE) guidance, Council released an Addendum to Susceptibility and Vulnerability Assessment February 2024. [PDF 756 KB] This updated Volumes 1 and 2 removing the previously highest scenario (RCP8.5+) of sea-level rise for the purposes of coastal hazard assessment work (eg, risk assessments and adaptation planning). The Volume 3 risk assessments take into account the updated IPCC and MfE guidance.

To ensure the coastal plan change review process is based on the best available information, Council will consider the need for further updates as part of its intended review of these assessments.

Risk assessments (Volume 3)

Risk assessments (Volume 3)

The risk assessments commissioned by Council were released in May/June 2024 and comprise four documents:

These assessments summarise identified risks in each area to the built environment, human, ecological, natural character, and cultural domains from projected coastal hazards over the next 100 years (i.e. to 2130) if no future adaptation is undertaken. They reflect updated advice from the Ministry and use scenarios SSP2-4.5 (middle-of-the-road scenario) and SSP5-8.5 (fossil-fuel-intensive scenario).

The assessments identify where the risk to domains within the coastal environment could change over time with increased projected relative sea level rise; and identifies where and when high and extreme risks could occur.

Susceptibility and vulnerability assessments (Volumes 1 and 2)

The susceptibility and vulnerability assessments [PDF 11.98 MB] were released in 2021 and 2022. They identify areas susceptible to current and future coastal erosion and inundation under various potential magnitudes of sea-level rise over 30, 50, and 100 years. It identifies Council infrastructure, community services and private property vulnerable to those hazards. They comprise three documents:

The Volume 1 methodology report has been externally peer reviewed by Beca and Greater Wellington Regional Council, and statements of review are attached at end of it. Additionally, as previously noted, in response to recent IPCC and MfE guidance Council updated both Volume 1 and 2 with an Addendum to Susceptibility and Vulnerability Assessment February 2024 [PDF 756 KB].

The combination of susceptibility and vulnerability assessments and risk assessments are intended to collectively provide the substantive evidence base for a risk assessment in accordance with the direction set by the NZCPS. However, in recognition that new information has been received since this work was commissioned, Council will commission a further review of these assessments to ensure the coastal plan change review process is based on the best available information.

Concerns raised

Council has been engaging with interested groups on the coastal science. Feedback has included critique from the group Coastal Ratepayers United (CRU) of the approach taken by Jacobs.

Council responded to those concerns by seeking clarification from the Department of Conservation (DOC) and Ministry for the Environment regarding the use of the New Zealand Coastal Policy Statement (NZCPS) and related DOC and Ministry for the Environment guidance. Our letters to DOC and Ministry for the Environment and the CRU critique (which is appended to the end of those letters), along with central government’s responses, can be found below:

The DOC and Ministry for the Environment responses indicated the approach taken by Jacobs is appropriate. Those responses informed advice provided to the Coastal Advisory Panel, and they are also likely to be drawn upon in guiding future district plan change work.

Council has also written to DOC regarding Council’s obligations under the NZCPS (which DOC is responsible for administering) to “take a 100-year perspective” when managing natural hazard risks along the coast.[2] Council’s letter and DOC’s response can be found below:

The DOC response confirmed that while the NZCPS requires coastal hazard risks to be identified over at least 100 years (Policy 24), and that councils are not allowed to modify this timeframe, Council has some discretion in the preparation of district plan provisions to manage this risk.  DOC also highlighted upcoming RMA reforms which will be relevant to the future coastal district plan change

Mapped Projected Coastal Hazards for Kāpiti Coast

Based on the Council-commissioned science, we’ve mapped the extent of coastal land on the Kāpiti Coast that may be affected by coastal hazards from projected sea level rise.[3]

View the map and check out the instructional video below for extra tips on how to use it.

Community-commissioned information

On 31 October 2024 a request was made on behalf of Coastal Ratepayers United (CRU) for an independent report by Dr Willem de Lange to be tabled with Council that includes information on coastal hazards.

Council received the De Lange report, submitted by CRU, in a briefing on 19 November 2024. The report can be found at Coastal Hazard Risk Assessment for the Kāpiti Coast [PDF 21.05 MB], and further information on his work at CRU Coastal Hazard Risk Assessment (including maps and a peer review).

Council acknowledges the views of CRU and others shared at the briefing on 19 November 2024 that the De Lange report contests some of the information in reports prepared by Jacobs NZ Ltd for the purposes of the Takutai Kāpiti project.

In response, Council will commission a further review of its assessments to ensure the coastal plan change review process is based on the best available information.

Other information

NIWA extreme coastal flood hazard maps

NIWA has modelled New Zealand’s 1% annual exceedance probability (100 year) extreme sea level flooding under current climatic sea conditions, plus relative sea level rise up to 2m above present-day mean sea level. Reports and a GIS viewer can be found at Extreme Coastal Flood Maps for Aotearoa New Zealand.

Greater Wellington Regional Council (GW)

GW has modelled inundation areas at a range of sea level rise values in the Wellington region, and modelled storm surge flooding at different sea level rise values, for a one percent annual exceedance probability (100 year) event. Background information and a GIS viewer can be found at Sea Level Rise and Storm Surge Modelling.

[1] The spatial location of the “coastal building line” and “relocatable building area” can be viewed on Council’s ePlan. On the right-hand side of the webviewer, turn on “Additional Spatial Layers” and underneath that ensure “District Plan 1999 Features” are also turned on. To understand what to look for, look in the legend under “District Plan 1999 Features”.  

[2] In 2023 Council also raised practical concerns with taking a 100 year perspective in its submission on a Proposed National Policy Statement on Natural Hazard Decision-Making [PDF 259 KB]. On p.4, Council’s submission states: “The issue is understanding at what point in the future a risk is likely to become intolerable, and understanding what timeframe we are supposed to be managing to. If we assume the useable life of a residential house is 50-years, then should we be managing for risks that will become intolerable over that timeframe.”

[3] Council has not made any decisions regarding the use of these maps or any particular sea level rise scenario for its coastal district plan change review.

Updated 28 February 2025