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Coastal Hazards and Climate Change: A Guidance Manual for Local Governmentin New Zealand

Executive Summary

1 Introduction to the Guidance Manual

2 The Changing Climate

3 Implications for New Zealand’s Coastal Margins

4 Responding to Climate Change: Future-proofing Decision-making

5 Understanding Changing Coastal Hazard Risk

6 Managing Coastal Hazard and Related Climate Change Risks

7 Further Resources

8 References

9 Glossary

10 Appendix 1: Relevant legislation

11 Appendix 2: Relevant case law

12 Factsheet 1: Coastal erosion

13 Factsheet 2: Coastal inundation (storms)

14 Factsheet 3: Coastal inundation (tsunami)

15 Factsheet 4: Components of sea level

16 Factsheet 5: Tides

17 Factsheet 6: Mean High Water Spring (MHWS)

18 Factsheet 7: Storm surge

19 Factsheet 8: Long-term sea-level fluctuations

20 Factsheet 9: Datums – Mean Sea Level and Chart Datum

21 Factsheet 10: Waves

22 Factsheet 11: Wave set-up, run-up and overtopping

23 Factsheet 12: ENSO and IPO

11 Appendix 2: Relevant case law

Disclaimer: This appendix has been prepared for the Ministry for the Environment by external contractors, as noted on the verso of this document’s title page.  To the extent that this guide deals with legal matters, it does not necessarily represent the views of the Ministry for the Environment; readers should not rely on it as legal advice.

11.1   Introduction

The following sections summarise a selection of case law relating to coastal hazards and the effects of climate change on coastal hazards (listed in Table 11.1).  For this revision of the Guidance Manual, the case law summary has not been updated from 2004 to 2008, except that Fore World Developments Ltd v Napier City Council W029/06 has been included.

Table 11.1: Case law summarised in Appendix

11.2   Maruia Society v Whakatane District 15 NZPTA (1991)

High Court, Judge Doogue presiding.

This case was decided under section 274(1) of the Local Government Act 1975, which was a similar provision to section 106 of the RMA.  The case involved subdivision of land fronting Ohiwa Harbour at Port Ohope.  The minimum ground levels imposed by the Council had been based on the effects of the 1968 Wahine storm.  The Council’s engineer considered that section 274(1) of the Local Government Act did not allow Council to recognise the possible effects of rising sea levels in determining conditions relating to the subdivision.  This was a judicial review of the Council’s decision.  In relation to interpreting section 274(1), the Court said:

I find it difficult to see ... that any decision-making body faced with that particular language is meant to put aside what it is known by it to be likely to occur within the immediate or foreseeable future, regardless of the fact that the event may not have occurred in the historical past.

That is now to say that an authority would have to go to any particular lengths to determine what are clearly difficult areas in respect of likely future changes in sea or ground level.  Whether the evidence at present available in respect of matters such as the ‘greenhouse’ effect is anything more than conjectural I do not know.  ... It would be a matter entirely for the council or the Planning Tribunal as to the extent to which it took such information into account.

The Court also held that the council does not have to protect every part of the land in the subdivision from inundation.  Section 274(1) gives the council discretion to determine whether there is sufficient protection against inundation suitable for subdivision.  This is important case law for interpreting section 106 of the RMA.

11.3 Bay of Plenty Regional Council v Whakatane District Council A 003/94

Environment Court, Judge Bollard presiding.

11.3.1  Overview

This case was decided under the provisions of the Local Government Act 1975 because the proceedings were initiated before the RMA came into force.  The case also concerned a subdivision at Port Ohope.  The Regional Council appealed the District Council’s decision to grant the subdivision based on the effects of sea-level rise.

The Regional Council’s witness (Professor Kirk) referred to sea-level rise predictions published by the Intergovernmental Panel on Climate Change (IPCC) and by the New Zealand Climate Change Programme (Ministry for the Environment).  The Court said:

We were told that the IPCC estimates are expected to be reviewed in the next year or two.  Be this as it may, Professor Kirk asserted that the climate models used to make predictions in country-wide, let alone global, terms are ‘crude in respect of ocean/atmosphere interactions and spatial resolution, especially in the southern hemisphere’.  In short, he considered that reliance placed on IPCC global estimates by other witnesses was misconceived.

Professor Kirk recommended a forecasting period of 2050 in preference to 2100 on the basis that reliable predictions cannot be made much past the year 2050.  He noted that the IPCC projections for global average sea level have an uncertainty range of +50%.

The Regional Council’s witness (Professor Healy) referred to the IPCC’s (1990) best estimate for sea-level rise: 66 cm by the year 2100.  He said that shoreline retreat would likely be accelerated by the ‘Bruun’ effect.  He recommended a coastal hazard zone line.  Other Regional Council witnesses (Dr Gibb and Mr Pemberton) regarded the IPCC best estimate data as important for reference purposes.

11.3.2  Court’s decision

... we are of the view that, in this case at least, a forecasting period to 2050 AD is reasonable.  Given the present state of understanding of the factors causing global and regional sea level changes, we accept the 2050 AD time horizon for present purposes – that being, in our view, as far as the ‘foreseeable future’ may reasonably be extended, allowing for the uncertainties of scientific knowledge and balancing the interests of the applicant and succeeding landowners.  By adopting such a time frame in this instance, it should not be thought that in another planning context a different time frame ought not to apply.  We simply say that, on the evidence before us and against the background of this particular case, such a forecasting period seems to us appropriate.  We thus adopt Professor Kirk’s evidence on this aspect.  On the other hand, we are persuaded by Dr Gibb and others that the IPCC ‘best estimate’ for general sea-level rise of 0.3 m as at 2050 AD should be taken heed of.

We accept ... that it is notoriously difficult to make a reliable prediction as to the sea-level change that will affect the subject land as far ahead as 2050, let alone beyond that.  Nevertheless, we consider that the best prediction currently available of the likely sea-level rise that will affect the country generally as at 2050 should be adopted.

The Court accepted Dr Gibb’s evidence on predicted rates of coastal erosion over the evidence of the Regional Council witnesses.  The Court adjourned the proceedings to allow the developer to prepare an amended scheme plan with a scaled-down proposal with an amended minimum building platform.

11.4   Opotiki Resource Planners v Opotiki District Council A 15/97

Environment Court, Judge Bollard presiding.

This case involved an appeal against a consent granted to construct a new integrated primary health care centre in the main shopping street of Opotiki.  It was argued that the proposal should be rejected for a number of reasons, including the site’s susceptibility to flood risk (sea-level rise, aggradation of local rivers over time, lack of a guarantee that the stopbanks would not fail during a major flood event).

The Court did not consider that this hazard risk warranted declining the consent.

One cannot overlook that, in reality, the district has a considerable investment incorporated in the commercial area, of which the former post office building, in itself a relatively modern and substantial building, forms part.  We do not regard upholding the proposal as some sort of unreserved and final endorsement of the town being located in perpetuity where it is.  Rather, our decision recognises the substantial infrastructure of present urban development and associated facilities/ services – including the stopbank protection works and the ongoing scheme directed to their maintenance and improvement.

Much of the evidence we heard was really pertinent to the basic question whether the location of the town itself is appropriate on account of the flood risk element, despite the measures taken to protect the town.  It lies well beyond the realm of this appeal to draw so bold a conclusion on an ‘across the board’ footing, and then go on to illustrate such a finding by rejecting the proposal.

The consent was granted with a condition relating to the floor level of the new building.

11.5 Judges Bay Residents Association v Auckland Regional Council and Auckland City Council A 72/98

Environment Court, Judge Sheppard presiding.

Resource consents had been granted by the Auckland Regional Council and Auckland City Council for extension of the Fergusson Container Terminal the Ports of Auckland.  Five parties appealed the decisions.

The Proposed Auckland Regional Policy Statement contained provisions regarding natural hazards – identified as including erosion, inundation of low-lying areas, land instability, rising sea levels and tsunami.  Policy 11.4.1(10) stated that location and design of new subdivision, use or development should be such that the need for hazard protection measures is avoided.  Policy 11.4.1(12) required a ‘precautionary approach’ to be used in avoiding, remedying or mitigating the adverse effects of natural hazards on development.

Expert evidence presented at the hearing addressed matters of extreme events such as sea-level rise and tsunamis.  The witness for Auckland Regional Council gave the opinion that the proposed wharf level would be adequate for extreme events.  The extension was proposed to have the same levels as the existing built port environment, and therefore the same protection from natural hazards.

The opinion was given that the standard design (particularly in regard to possible sea-level rise) was appropriate and that inundation and erosion were not relevant risks to a built port environment.  The Court found that the proposal would not cause any adverse wave effects or any other adverse effects in extreme events.

11.6 Auckland City Council v Auckland Regional Council A 28/99

Environment Court, Judge Sheppard presiding.

This case involved appeals against refusal of resource consents required for the proposed Britomart underground transport and parking centre in central Auckland.

The proposed five-level underground development involves construction below groundwater level and thus diversion was required.  The appeals opposed the consents for earthworks and the diversion of groundwater, based on potential damage to land and buildings in the vicinity from ground movement resulting from excavation and groundwater diversion.

A submitter urged that consideration be given to the possibility of tsunamis and storm surges causing the water of the harbour to overtop seawalls and flood the Quay Street underpass, although acknowledging that it would be unlikely that seawater would enter the Britomart transport centre itself.  The Court held that sea-level and climate change issues were relevant only to the extent that the bases for ground water modelling had been properly prepared, having regard to contingencies.

The key witness explained that effects on groundwater levels would fully manifest themselves within 10 years of the start of construction, which is a relatively short period within the context of sea-level rise.  Sea-level rise due to climate change would have no effect on the validity of the groundwater model predictions.

11.7   Kotuku Parks Ltd v Kapiti Coast District Council A 73/00

Environment Court, Judge Sheppard presiding.

This was an application for consents for subdivision and earthworks and involved an appeal against some of the conditions imposed by Kapiti Coast District Council.  Ultimately, the consents were declined by the Court on grounds that included failing to protect significant habitat or indigenous fauna, adverse visual effects and impairment to kaitiakitanga.

It was argued by the Waikanae Estuary Guardians that the land proposed to be subdivided would be likely to be subject to material damage by subsidence as a result of earthquake, and by inundation and erosion from the sea in conditions of storm surge, tsunami, and sea-level rise.  This was relevant for consideration under section 106 of the RMA.

The Court found that although a major event causing extensive inundation or erosion could occur on this coast at any time, it was not standard practice to design for such extreme events as those described by witnesses for the Waikanae Estuary Guardians.  The evidence about catastrophic events had been in relation to the next hundreds of years, and would have effects along the entire Kapiti Coast.  Another witness gave evidence of catastrophic events having a return period of at least every 250 years, and of larger saltwater inundation events occurring one every 400 years.

Sufficient provision to avoid or mitigate the likelihood of damage was made by the building platform levels that had been set by the Council.  This building platform level had been based on a:

• river flooding event of 1% probability combined with a storm sea-surge event of 5% probability; or
• storm sea- surge event of 1% probability with a similar allowance for future sea-level rise.

This was considered to be sufficiently conservative to avoid or mitigate the likelihood of damage.

11.8 Lowry Bay Residents Association v Eastern Bays Little Blue Penguin Foundation Inc W45/01

Environment Court, Judge Kenderdine presiding.

This case involved appeals against consents to establish a facility for the reception, recovery and rehabilitation of wild birds for release back into the wild.  The Court said:

It was the Association’s case that the applicants and respondents appear to have studiously ignored the fact that the proposed buildings will be located in an area having an obvious natural hazard.  It is not sufficient to say that buildings will be built in accordance with the Building Code.  The evidence of the witnesses for the Association demonstrate that location of any buildings on the site proposed is unwise and courting disaster.

The Hutt City Council’s witness said that any reference to the potential for the proposed facility to be affected by severe storms, salt deposits and spray drift was not relevant to the consideration of the grant of the consent sought, because the design and construction of the buildings was a matter to be considered under the Building Act 1991.

The Court said:

We do not understand how a dwelling house (large enough to hold small children), an educational facility (which will include small children), and a cafe for 54 visitors could be approved for this site ...

We concluded that the location of all aspects of the proposal and the activities it imports, is not commensurate with the principles of sustainable management.  The last word on natural hazard goes to Mr Churchman who submitted it is impossible to say that siting this proposal in an area demonstrably subject to coastal hazards is in accordance with the plan or commonsense – a submission we endorse.

11.9   Save the Bay v Canterbury Regional Council C6/2001

Environment Court, Judge Jackson presiding.

11.9.1  Overview

The reference related to provisions of the Proposed Regional Coastal Environment Plan (PRCEP) dealing with coastal hazards as they relate to Taylor’s Mistake and Hobson’s Bay (Banks Peninsula).  The plan contained:

• Hazard Zone 1 – land at risk from coastal erosion within 50 years (its boundary, the ‘hazard line’, runs approximately parallel to the shoreline)
• Hazard Zone 2 – inland from Hazard Zone 1; land at risk from coastal erosion within 50 to 100 years.

These zones were defined only by reference to coastal erosion.  Other natural hazards were not dealt with by the rules but were to be the subject of further plan reviews.  These included tsunami events and the possible effects of global warming (on sea level, coastal sediment supply and storm generation).

The plan stated:

There is a need to undertake more investigation on the magnitudes frequencies and possible effects of these events.  The results are to be used in future reviews of coastal hazard management policies and methods.  In the absence of consensus as to the precise effects of global climate change, the wisest course is to adopt a precautionary approach when considering developments in the coastal area.

Save the Bay was concerned about storm damage by wave action and rockfall.

11.9.2  Court’s decision

The Court was concerned that the objectives and policies in the plan related only to coastal erosion and inundation and not to other natural hazards and, for inundation, the objectives policies were not followed through with rules (because the hazard zones related only to coastal erosion risk).  Outside the natural hazard zones, the reconstruction of those buildings damaged by the sea was not controlled by the plan at all.

The Court considered that there was totally inadequate recognition of catastrophic natural events.  Ninety per cent of damage to the environment caused by natural hazards occurs in 10% or less of events.

If resource management has a significant function in relation to natural hazards – and it seems important enough to Parliament to give functions in respect of natural hazards to the regional and territorial authorities – then surely authorities should recognise that inverse relationship in the preparation and wording of their plans.

The Court heard evidence about the location of the hazard line and said:

In our view drafting a hazard line is not as scientific as ascertaining where the MHWS is (although that too is fraught with difficulty).  The task is to draw a line as an administrative boundary which is conveniently ascertainable.

The boundary line for Hazard Zone 1 at Taylor’s Mistake was amended.

11.9.3  Conclusions on the case

This case provides guidance on the interpretation and administration of sections 30 and 31 of the RMA:

• regional and territorial authorities need to recognise the significant function of resource management in relation to natural hazards in the preparation and working of their plans
• councils need to recognise serious, but infrequent, events when planning
• dealing with only one coastal hazard in the plan rules is not an integrated management approach.

11.10 McKinlay v Timaru District Council C 24/2001

Environment Court, Judge Jackson presiding.

The Canterbury Regional Council controlled the use of land in relation to natural hazards through its regional policy statement.  In relation to the site in question, the regional policy statement did not contain any rules relating to natural hazards.  Nor were there in the proposed regional coastal plan.  However, there were rules governing natural hazards at the site in the Timaru Proposed District Plan.  Under those rules, construction of a residential building was prohibited at the site (because it was within the ‘Coastal Inundation Line’).

The Court was asked to decide what would happen if an existing residence at the site was destroyed by a natural hazard such as a flood, and whether reconstruction would be prohibited by the proposed district plan.  This relates to ‘existing use rights’ (sections 10 and 20 of the RMA).  The Court said that the property owner would have existing use rights to rebuild provided that the dwelling rebuilt was the same or similar in character, intensity and scale as the present building (section 10).  However, if there had been regional rules governing the reconstruction, then the situation would be different (sections 10(4) and 20(2)(c)).  So, although regional rules can ‘override’ existing use rights, district rules do not.

11.11 Bay of Plenty Regional Council v Western Bay of Plenty District Council A 27/02

Environment Court, Judge Bollard presiding.

11.11.1 Overview

This reference related to provisions of Variation No.  1 to the Western Bay of Plenty District Council’s proposed plan – development controls affecting coastline areas at Waihi and Pukehina beaches.  The referrers were the Regional Council and the Waihi Beach Protection Society.

The plan contained a ‘Coastal Protection Area’ line, based on a 1993 study.  (The Regional Plan also contained an ‘Areas Sensitive to Coastal Hazards’ line, which was compatible but not identical to the coastal protection area line).

The coastal protection area was split into ‘high risk’ and ‘low risk’ areas.  Within the ‘high-risk’ areas, new buildings and alterations were a discretionary activity.  In ‘low-risk’ areas, such activities were permitted, subject to conditions.  Subdivision was discretionary in both areas.  The Regional Council sought discretionary activity status for buildings in both areas.  The Society sought permitted activity status for buildings in both the areas.

The District Council pointed out that, for permitted activity status, further conditions on building could be imposed under the Building Act 1991.

The plan variation was supposed to be an interim solution, providing adequate protection until ‘future options for coastal management are known’.  These include coastal protection works, but the Council did not want to proceed with those until other options had been investigated.

11.11.2 Court’s decision

The Court considered that the planning instruments had properly recognised coastal erosion, inundation, dune stability and sea-level rise issues.

The Court considered that the Regional Council’s approach should be accepted.  It was sound to plan for a 100-year predicted risk period.  The District Council argued that only a 50-year risk period should be planned for, but this was rejected, particularly considering the principles in the New Zealand Coastal Policy Statement.  The areas should be categorised as ‘primary’ and ‘secondary’ areas of risk rather than ‘high’ and ‘low’, as both areas carry significant risk.  Potential adverse effects through changed climate conditions and sea-level rise were accepted as existing.  In secondary risk areas, buildings and extensions should be a limited discretionary activity.

The argument from the Society was rejected as follows:

... it was argued that the voluntary assumption of risk by private property owners does not abrogate the Council’s responsibility of controlling the use of ‘at risk’ land for the purpose of avoiding or mitigating natural hazards.  We accept that submission … Failure to manage known actual and potential effects of natural hazards at Waihi and Pukehina Beaches under the Act’s regime would not, in our view, be consistent with the legislative purpose of sustainability.

The Court commented on the evidence and the uncertainty inherent in this area of planning.  These, together with the New Zealand Coastal Policy Statement, pointed to a precautionary approach to planning.

It commented on the interface with the Building Act:

... the respective means of control under the RMA and the Building Act should not be narrowly construed as merely amounting to alternatives available to a Council to achieve the same ends.  Rather they should be viewed in a broader light, both individually and in combination, of assisting to serve the public good.  Were the contrary contention sound, Parliament’s recognition of the two separate Acts’ frameworks of authority and control might be seen as unnecessarily repetitious.  Each in fact serves its particular purpose – that under the RMA of promoting the sustainable management of resources in the context of the wide environmental perspective that the Act embraces; and that under the Building Act by focussing on the integrity and safety of buildings wherever they are located.  Logically, any relevant controlling provisions that govern a development proposal under the holistic management regime of the RMA will generally fall to be invoked initially, with the application of controls under the Building Act following as appropriate in terms of that Act.

11.11.3 Conclusions on the case

Given the uncertainties in this area of planning, a precautionary approach should be taken.

The Building Act should not be relied on completely – the RMA’s purpose of sustainable management should still be fulfilled.

(The final plan provisions for this case were resolved in Bay of Plenty Regional Council v Western Bay of Plenty District Council A 141/02.)

11.12 Skinner v Tauranga District Council A 163/02

Environment Court, Judge Bollard presiding.

11.12.1 Overview

The reference related to provisions of the Tauranga District Council’s proposed plan – development controls affecting coastline areas at Papamoa Beach.  The referrers were residents represented by a Mr Skinner.

The plan contained a ‘Coastal Hazard Erosion Policy Area’ (the Area).  Within the Area were the following hazard risk zones:

• an extreme risk erosion zone (the area immediately susceptible to notable adverse effects from coastal hazards) – any development a prohibited activity
• a high-risk erosion zone (erosion predicted 2050–2100, taking into account global warming predictions) – development is limited discretionary
• a moderate-risk erosion zone (erosion predicted 2050–2100, taking into account global warming predictions) – development is limited discretionary
• a buffer zone – (an ‘at risk’ area should parameters used to arrive at the other zones should be too low) – has an in-built safety factor of 30%.

The Area had been developed by a coastal hazards expert Mr Gibb.  Mr Skinner (resident) sought the Area to be relocated seaward of the residences.  He had already commissioned a report from a Mr Smith.  In response, the Council had asked a Mr Reinen-Hamill and experts at the Auckland Regional Council (Mr Brookes) to review the Smith report and the Gibb report – concluding that the Gibb report should be preferred.

There was much expert evidence on the assessment of coastal hazard risk.  The Tauranga District Council called as witness Mr Gibb, Mr Reinen-Hamill, and Mr Brookes, supported by Dr Bell (NIWA) and Dr de Lange (Waikato University).  Some of these witnesses applied the ‘Bruun rule’.

Mr Skinner called evidence from Mr Smith (NIWA), supported by Dr Abbott, Dr T Lustig and Mr Oldham (NIWA).  Mr Smith considered it unlikely that cutback from a one in 100-ear storm would cause sufficient damage to endanger beachfront houses, even allowing for future climatic uncertainties and sea-level rise.  The use of the ‘Bruun rule’ was rejected by these witnesses.

11.12.2 Court’s decision

The Court concluded that the beach was susceptible to erosive cutback when major storm events occur, and to continual dune line change.  The 100-year period was deemed reasonable for coastal planning.  Predictions were difficult but a lack of field data meant that the Area should not be moved as Mr Skinner wanted:

In the absence of such data, it would not be prudent to adopt an approach that postulates that the future dynamics of the beach profile will carry no hazard risk to seaward-facing parts of properties immediately proximate to the beach during the next 100 years.

Also:

Of major import in arriving at a determination in this instance in the face of the conflicting evidence, is the lack of certainty as to future climate change and how such change will affect the various ‘drivers’ that lead to shoreline movement.

In relation to sea-level rise, the Court noted the ‘most likely’ mid-range predicted by the IPCC.

Bearing in mind the precautionary element in the New Zealand Coastal Policy Statement, the Court found in favour of the witnesses who considered the ‘Bruun rule’ (which applied to ‘closed systems’ –

we find that the notion of an ‘ample cushion’ of sediment supply cannot be endorsed with [a] degree of confidence ...).

Economic evidence was put forward on development potential and on the decrease in property values of beachfront properties.  However, the evidence was not sufficient to override the need for the Council to plan ahead for coastal hazard risk.

The Area was upheld, with the extreme, high and moderate risk zones in it, but the Court considered the safety buffer zone could be removed as it was ultra cautious.

The effect is to place a zone restriction on the properties affected beyond the extent necessary to ensure sufficient and appropriate recognition of coastal hazard risk to those properties during the 100-year forecasting period.

However, the Council was directed to monitor trends so that the plan could be refined based on continuing experience and additional data.

11.12.3 Conclusions on the case

• The District Council had appropriately fulfilled its function in relation to natural hazards.
• It was correct to take a precautionary approach, given the uncertainties involved.
• The IPCC predictions on sea-level rise were endorsed.
• The case is interesting because of the large number of coastal hazard expert witnesses that were called.

11.13 Fore World Developments Ltd v Napier City Council W 029/06

Environment Court, Judge Thompson presiding.

In this case, appellants sought to have land zoned residential to enable subdivision, despite coastal erosion concerns.

The Court acknowledged that sea-level rise would result in wave action occurring at a higher elevation on shore and thus cause coastal erosion.  In order to calculate the rate of coastal erosion, the Court accepted the sea-level rise estimates of the IPCC.

In its overall assessment, the Court stated that climate change aspects such as increased storminess require the consideration of an additional buffer allowance.  This was explained as follows:

It is not a situation where it is necessary to be overly cautious but it would be prudent to provide for a buffer in addition to the estimated extent of the coastal erosion to make some sort of allowance for the factors that have not been estimated and included.  ...  That buffer should be in the order of 25% of the sum of the estimated distance.

The decision further described the inland extent of the coastal hazard zone based on the information before it and the buffer area.

11.13.1 Conclusions on the case

• A 100-year timeframe is appropriate for considering coastal issues.
• The ‘Bruun rule’ was accepted as an adequate method for assessing the effects of sea-level rise on coastal retreat.
• A graduated coastal hazard zone was not favoured in this case owing to difficulties of application and enforcement with a relatively small overall width of land.
• Adoption of a precautionary approach, based on weighted consideration of the level of knowledge of the risk, its likelihood of occurrence and the consequences, was accepted.
• The case is interesting because of the large number of coastal hazard expert witnesses that were called.

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