Planning for coastal adaptation

Why we need to adapt at the coast?

While much of the global focus and discussion around climate change has been on mitigating (reducing) greenhouse gas emissions, adaptation has now become an integral part of climate change policy worldwide.

An important component driving impacts on coastal areas is the very long response times of sea-level rise to warming of the atmosphere and then oceans. While global emission cuts can reduce the rate and the ultimate magnitude of sea-level rise, a long-term commitment (centuries) to continuing rise in sea level has already been built into the climate-ocean system from emissions to date, resulting in a need for substantial adaptation to rising seas around our shores.

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Coastal risk exposure for New Zealand

NIWA provided national and regional/district scale assessments of New Zealand’s future coastal risk exposure for the 2015 report Preparing New Zealand for Rising Seas produced by the Parliamentary Commissioner for the Environment (PCE). The NIWA report on coastal risk exposure used high-resolution land elevation data (LiDAR) and building and above-ground infrastructure information (e.g. location, type) from the RiskScape system, to count up (like census) the numbers of buildings, wharves/jetties, airports and kilometres of road and rail in different elevation bands around our coast up to 3 m above the present mean high water spring (MHWS) mark.
The infographic shows a summary of the risk-exposure census in low-lying coastal areas that are between 0 to 1.5 m above MHWS.

A second NIWA study for the PCE report highlighted the increasing change in frequency in coastal-storm inundation that will occur on the back of even modest rises in mean sea level. For example a 0.3 m rise in sea level will mean today’s 1-in-100 year coastal flooding event in Wellington or Christchurch will become an annual occurrence, with larger and deeper flood events less often. This change in frequency will occur for a slightly higher sea-level rise in areas with larger tide ranges e.g. 0.45 m rise is needed for this to become an annual event in Auckland.

Coastal adaptation guidance for local government

In 2017, a NIWA-coordinated team updated the Ministry for the Environment coastal hazards and climate change guidance for local government, from the previous 2008 version. The coastal guidance comprises a more-detailed technical document and a summary Preparing for Coastal Change, providing contemporary national guidance to local government and for a range of practitioners working on long-term planning or infrastructure projects at the coast and around estuaries.
The approach in the 2017 guidance differs from that in previous versions, and from current coastal hazard management practice, with regard to:
a) incorporating uncertainty into hazard/risk assessments and planning for adaptation, using a range of scenarios for the rate of rise in sea level towards the end of this century and beyond to 2150;
b) adoption of a dynamic adaptive pathways planning approach to planning around uncertainty, rather than locking in a particular response option based on a single pre-determined sea-level rise for a planning period (which may be over or under what actually occurs), and,
c) the central role of community engagement, based on sound principles, in the decision-making process.

Court case summaries relevant to coastal hazards and planning

In Appendices of the 2017 MfE coastal guidance for local government: Appendix A outlines the statutory framework for managing hazard risk in coastal and estuarine areas, and Appendix B lists relevant court cases that may be of interest to users of the coastal guidance.

During revision of the 2017 MfE coastal guidance, more recent case summaries were added by Sylvia Allan (Allan Planning and Research Ltd.) to those from the 2004 and 2008 MfE guidance editions. 

Summaries of these court cases to complement Appendix B of the MfE coastal guidance are provided here.

Disclaimer:  This summary material has been prepared for NIWA by external parties and is intended only to provide a summary and general overview of the court cases. The summary material does not represent the views of NWA, is not intended to be comprehensive nor does it constitute legal, commercial or other professional advice.  The summary material should not be relied upon as a substitute for seeking legal or other professional advice and readers should seek this advice before acting or relying on the summary material.  

 

Building Act 2004 determinations relevant to coastal areas 

(prepared by Sylvia Allan, Allan Planning and Research Ltd., Lower Hutt)

Appendix A of the 2017 MfE coastal guidance for local government outlines the statutory framework for managing hazard risk in coastal and estuarine areas.

Box A.4 of that Appendix outlines relationships between the Resource Management Act 1991 and the Building Act 2004, listing three determinations by the Ministry of Business, Innovation and Employment (MBIE) who administer the Building Act. These provide some clarity on the relationships that apply when building at the coast.  A summary of these determinations are provided below.

  1. Determination No. 2004/08 – Protection of other property from coastal hazards. Issued 23 April 2004 (Note: this determination applied the earlier natural hazard provisions under the Building Act 1991).

    A dwelling was proposed on an active coastal spit. The building had a concrete floor slab and was within the 2060 erosion zone and the seaward part of the house within the current erosion risk zone by 3 m (from investigations undertaken in terms of RMA considerations). Neighbours and the Regional Council expressed concern about the coastal hazard being exacerbated on their properties as a result of the new dwelling. The Council had considered the proposed building could be demolished and removed, and had granted a building consent with conditions that required that to occur when the dune-line was 10 m from any part of the house.

    The determination considered that demolition may not be able to be undertaken within the relatively short window of time available in a storm, and that collapse could occur and threaten neighbours’ property. It reversed the Council’s decision to issue the building consent. 

  2. Determination No. 2005/028 – Revisited protection of other property from coastal hazards. Issued 10 March 2005.

    This determination considered a subsequent building consent for a coastal property, with an increased distance (15 m trigger distance) from the seaward toe of the foredune, at which stage it was to be removed or demolished. The determination addressed the risk of the building collapsing resulting in erosion on a nearby property.

    The determination decided that scenario was unlikely and confirmed the issue of the building consent for the proposed building, subject to the territorial authority’s being satisfied on reasonable grounds that the design and construction of the house is such that erosion advancing a metre under the house would not cause it to collapse and form a groyne. 

  3. Determination No. 2007/110 – Building consent for a house on land subject to coastal hazards. Issued 17 September 2007.

    This referred to a coastal dwelling at Haumoana, Hawke’s Bay. The Hastings District Council had refused to grant a building consent for a house and carport on the grounds that the proposed building was on land subject to natural hazards (coastal erosion and inundation).

    The determination considered that for the particular building proposed, a building consent could not be granted that met the Building Code. However, the determination pointed out that if waivers had been sought by the applicant (e.g., a shorter building life specified, or a trigger for removal specified) a building consent may have been able to be issued. The decision discusses the purpose of the law in detail.

The full text (pdf) for these determinations can be found here.

Disclaimer:  This summary material has been prepared for NIWA by external parties and is intended only to provide a summary and general overview of the Building Act determinations by the Ministry for Business, Innovation and Employment (MBIE). The summary material does not represent the views of NWA, is not intended to be comprehensive nor does it constitute legal, commercial or other professional advice.  The summary material should not be relied upon as a substitute for seeking legal or other professional advice and readers should seek this advice before acting or relying on the summary material.  

Levels of coastal risk exposure, in terms of resident population, buildings, roads, railway, airports and jetties/wharves for land elevations below 1.5 m above MHWS at the coast. Results on the left have been aggregated from regional totals for regions where LiDAR data was available.