Coastal Hazards FAQs
This page contains answers to frequently asked questions about coastal hazards.
Updated 15 March 2013
1. What do the 50 and 100 year coastal erosion projection line mean?
2. What is meant by ‘managed’ and ‘unmanaged’ scenarios?
3. What does ‘shoreline’ mean?
4. What is council doing about the shoreline projections?
5. Why has this information come out now?
6. What does this have to do with recent publicity by Greater Wellington Regional Council about sea level rise?
7. How does the new information relate to the District Plan?
8. What sorts of provisions are being looked at in the Proposed District Plan?
9. What else is Council doing about the effects of climate change?
10. What are other councils doing?
11. How do we know the coastal erosion projection lines are accurate?
12. What methodology was used?
13. How many properties are at risk of potential coastal hazards?
14. What are LIMs for?
15. When will any changes to the District Plan take effect?
16. Does Council have an obligation to protect the beachfront?
17. What can residents do to protect their properties?
18. Can property owners build a seawall?
19. What is wrong with seawalls?
20. What about existing seawalls?
21. What about existing privately-owned seawalls?
22. Why should Council pay to maintain seawalls that protect properties at Raumati but not other areas?
23. What’s the approximate cost of seawalls?
24. What is the value of properties affected by the shoreline projections?
25. How do I know when my property will be at risk?
26. What can I do to dispute the shoreline projection for my property?
27. If nothing is done, will homes be lost to the sea?
28. Is Kāpiti more affected than other parts of New Zealand?
29. What do the shoreline projections mean for home owners or buyers?
30. How do other councils’ 100 year assessments compare?
31. How was the coastal hazard assessment peer reviewed?
32. Why wasn’t the community forewarned shoreline projections would be included in LIMs?
33. Are there currently setback lines in Kāpiti?
34. What kind of input can people have to the District Plan Review provisions?
35. What about cross-leased sections?
36. Why are some coastal erosion projection lines on land higher than projected sea level or higher than properties behind them?
37. How are LIMs prepared?
38. When will the rules in the new District Plan take effect?
39. What is a Certificate of Compliance and how does it operate?
40. I’ve heard the proposed District Plan provisions have some weight in relation to consents even before it becomes operative. What does that mean if I want to build?
1. What do the 50 and 100 year coastal erosion projection lines mean?
The lines are the result of a coastal erosion hazard risk assessment. They project the shoreline (See FAQ 3) along Kāpiti within 50 and 100 years, factoring in the risk of sea level rise and erosion as an effect of climate change.
The potential shoreline retreat was based on a sea level rise of 0.3m within 50 years and 0.9m within 100 years. Ministry for the Environment guidelines for assessment suggest 0.8m by the 2090 decade, plus 0.1m per decade after that date.
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2. What is meant by ‘managed’ and ‘unmanaged’ scenarios?
The risk assessment includes shoreline projection for:
- Managed 50 year
- Unmanaged 50 year
- Unmanaged 100 year
- Managed 100 year (river and stream mouths (inlets) only)
The managed and unmanaged scenarios mean different things for different parts of the coast. They look at hard protection structures such as seawalls, but not soft protection measures such as planting or dune restoration.
No ‘managed’ projected shorelines are shown on the maps where there are currently no publicly maintained hard protection structures i.e. most of the coastline north of Paraparaumu. The exception is the Ōtaki and Waikanae rivers and Waitohu and Waimeha stream mouths managed by Greater Wellington Regional Council, and some other stream mouths managed on an as needed basis by Kāpiti Coast District Council.
Open coast and inlet ‘managed’ scenario
This assumes existing public seawalls would be maintained in the short term, but that very heavy storms or other coastal processes would cause them to fail within 50 years. Some coastal erosion could occur in the time before repairs could take place (meaning the shoreline could gradually retreat in parts).
The scenario presumes no new hard protection structures are built, and existing structures are not heightened or extended.
There is no 100-year managed scenario for seawalls because hard protective structures would have to get bigger and stronger to ‘hold the line’ against erosion, but the risk of failure would remain. In addition, in line with the New Zealand Coastal Policy Statement, Council has signalled in the Long Term Plan its intention in the longer term to move its infrastructure away from the coastline.
A separate assessment was done for areas near streams or river mouths (inlets).
The ‘managed’ scenario assumes Greater Wellington continues to straighten the channel at the river mouth and continues any maintenance of existing engineered structures such as stop banks that constrain the river mouth.
Unmanaged scenario
The ‘unmanaged’ scenario for river and stream mouths (inlets) looks at what might happen if current management stopped.
The coastline north of Paraparaumu is largely unmanaged at present and the unmanaged scenario assumes this continues.
South of Raumati the unmanaged scenario considers where the shoreline line may be if current seawalls fail and are not repaired.
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3. What does ‘shoreline’ mean?
The shoreline is the extent of active coastal processes on a natural beach - identifiable as the edge of the vegetation. In terms of the projected shoreline the extent is related to the erosion caused by a storm, so will be further inland than the regular high tide (as shown in the photo to the right which shows a house on the cliff top in South Wairarapa).
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4. What is council doing about the shoreline projections?
How to manage coastal erosion and other hazards that may worsen due to climate change is expected to be a big focus for Council and the community in the coming decades. Council’s current policy through the Long Term Plan is to maintain and protect roads and public health infrastructure (water supply, stormwater and sewerage) assets in the short term, but to progressively move public infrastructure away from areas at high risk. Council will not intervene to protect private property with new or improved seawalls or similar hard structures.
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5. Why has this information come out now?
Concern about coastal erosion is not new. The effects of climate change were noted as a significant issue in the 2006 Long Term Council Community Plan and many coastal residents were involved in developing the 2006 Coastal Strategy. Managed retreat was indicated in the 2009 LTCCP and again in the 2012 Long Term Plan. In addition, a discussion document released in 2010 at the start of the District Plan Review covered coastal erosion risk.
Hazard risk assessment is a long and complicated process. The final reports for both the 50 and 100 year hazard risk were received by Council in August 2012. Council is legally obliged to place this technical information on LIMs. However, LIMs have noted since 2004 that coastal hazard information is being reviewed.
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6. What does this have to do with recent publicity by Greater Wellington Regional Council about sea level rise?
Kāpiti Coast District Council’s risk assessment was on coastal erosion, whereas GWRC looked at flooding from coastal storms. Two reports released by GWRC in July 2012 show Wellington has the highest rate of sea-level rise in New Zealand. Its coastal flooding report showed Kāpiti experienced smaller waves than some areas but was subject to larger storm tide flooding due to shallower sea floors near the coast.
The sea level rise component of this research also took into account some new research by GNS Science which shows that between major earthquakes, the Kāpiti Coast is currently subsiding by about 1-2mm per year. Copies of the reports and other background information can be viewed here.
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7. How does the new information relate to the District Plan?
The Proposed District Plan notified in November 2012 included policies and rules in response to the coastal hazard risk.
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8. What sorts of provisions are being looked at in the District Plan?
Proposed provisions include coastal development restrictions that create a ‘no build’ and ‘relocatable’ area. Seaward of the no-build line development would be restricted to the current building footprint and floor area. Development between the no-build and relocatable lines would need to be able to be relocated if threatened by the sea. Subdivision would be prevented in the no-build and relocatable areas.
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9. What else is Council doing about the effects of climate change?
Council has done a lot of work on natural hazards, including coastal erosion and flood mapping. How to respond to coastal hazard risks will be a major focus for Council, the community and coastal property owners in the next few decades. Around 200 people attended a series of natural hazard information exchanges held in May and June 2012 and following on from these working groups are being set up to identify issues and ideas to respond to local impacts of climate change.
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10. What are other councils doing?
The New Zealand Coastal Policy Statement (NZCPS) required all councils to do a 100 year assessment of their coastal erosion hazard risk.
Some have already taken steps to restrict development in coastal erosion risk areas, including the following district councils:
- Whangarei
- Thames Coromandel
- Opotiki
- Whakatane
- Western Bay of Plenty
- Hastings
- Napier
- Tasman, and
- Tauranga City Council
Their assessments looked at similar themes, including long term trends and dynamic fluctuations, but used different methods depending on the nature of the coast, type of data available and resourcing.
Councils are taking a consistent approach to their district planning, including the use of two hazard risk lines. Development restrictions generally include no building or extensions in the more immediate risk ("no build") area and only relocatable buildings in the longer term risk area.
Councils that completed their 10-year District Plan Review before the requirement for a 100 year assessment was imposed by the NZCPS are not required to propose any coastal development restrictions until their next review.
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11. How do we know the coastal erosion projection lines are accurate?
The information is the result of a robust scientific assessment following best practice methodology, which was peer reviewed by leading coastal erosion scientists. View the full Kāpiti Coast Erosion Hazard Assessment report here.
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12. What methodology was used?
The methodology is explained in the reports, but used the following formula:
Coastal Erosion Prediction Lines = LT + ST + SLR + DS + CU, where:
LT = longer term historic shoreline change
ST = shorter term shoreline fluctuation
SLR = shoreline retreat associated with sea-level rise
DS = dune stability
CU = combined uncertainty.
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13. How many properties are at risk of potential coastal hazards?
Around 1,800 properties are at risk of being affected by changing shorelines within 100 years, up to 1,000 of these within 50 years. This means at least part of the property is at risk of being encroached on by rising shorelines. Some properties may be affected much sooner.
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14. What are LIMs for?
LIMs are property reports generated by councils on request. They outline all information a council holds on a property, including permitted land use, consents, storm water and sewer drains, rating information and potential natural hazard risk including erosion and flood risks. They are most commonly requested by potential property purchasers.
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15. When will any changes to the District Plan take effect?
The coastal hazard rules will not apply until all submissions have been considered, hearings completed and any appeals resolved. The earliest that this could occur is September 2013. Submissions on specified coastal environment provisions in the Proposed District Plan close at 5pm, Tuesday 2 April 2013. Submissions on all other provisions closed on 1 March 2013.
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16. Does Council have an obligation to protect the beachfront?
No. Council receives money from ratepayers to provide them with services and outlines in the Long Term Plan how their money will be spent. There is no legal obligation to hold a shoreline. The presumption in the NZ Coastal Policy Statement 2010 is that natural processes should be able to occur.
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17. What can residents do to protect their properties?
Coastal scientific thinking is that the shoreline is more resilient if left natural.
Community groups are already undertaking dune restoration projects along the coast that may slow the rate of erosion. People with private structures such as sea walls may continue to maintain them, but if they do not have resource consent they may be asked to remove them at some stage.
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18. Can property owners build a seawall?
[updated 26 March]
A protection wall built inland of the average high tide is referred to as a retaining wall, while one built seaward of the average high tide (on regularly wet land) is referred to as a seawall.
Retaining walls
Under the current District Plan owners may build a retaining wall up to 1.5 metres high without a resource consent, so long as any earthworks comply.
In the Proposed District Plan, a resource consent will be required for any retaining wall longer than 5 metres in a no-build zone. The earliest this change could occur is September 2013, after close of submissions, hearings and decisions. Appeals may delay this further.
Seawalls
If you want to build a wall on land below the average high tide mark (i.e. regularly wet by the sea), it is classified as a seawall and requires resource consent from Greater Wellington Regional Council (GWRC).
If consent is granted by Kāpiti Coast District Council for a retaining wall but coastal erosion later results in the wall being seaward of the average high tide, it may effectively become a seawall.
If this happens owners are no longer covered by existing use rights under the District Plan, as seawalls are under the jurisdiction of GWRC. People should seek advice from GWRC before construction if there is a risk a retaining wall may change to a seawall in the future.
Council’s District Plan and the Wellington Regional Coastal Plan must take note of the New Zealand Coastal Policy Statement and Wellington Regional Policy Statement, both of which strongly discourage new coastal protection structures.
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19. What is wrong with seawalls?
Seawalls and other hard structures have significant negative effects on the natural environment. This includes reduced beach amenity and restrictions to beach access, as well as increased erosion, known as ‘end effects’, on the land at either end of the wall. With sea levels likely to rise sea walls would need to be increasingly stronger and higher, which would be unattractive and very expensive. Development also reduces the ability of natural coastal processes to enable dunes to function as a natural barrier to coastal hazards.
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20. What about existing seawalls?
Council’s current policy is to maintain existing critical public assets. However, it has indicated through the Long Term Plan that it may not manage public seawalls in the longer term.
Sections of timber seawalls at Paekākāriki and Raumati are nearing the end of their life. Some strengthening can still take place but this is not expected to be effective beyond the 50-year timeframe.
Importantly, both the 50 and 100 year shoreline predictions assume that all seawalls will fail at some stage during this time. The risk assessment does not presume damaged seawalls will be repaired beyond 50 years because this may become impractical and unaffordable.
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21. What about existing privately-owned seawalls?
Privately-owned seawalls have not been factored into the coastal erosion risk assessment because it cannot be presumed landowners will be in a position (financial or otherwise) to continue to maintain and repair them for 50 years or beyond.
Council will not maintain private seawalls and they may have to be removed if they do not have a resource consent.
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22. Why should Council pay to maintain seawalls that protect properties at Raumati but not other areas?
Council maintains the community seawall in Raumati and Raumati South as part of an agreement reached in the 1970s when the wall was built. Central government funded the wall, along with residents, on the understanding local government would undertake the maintenance.
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23. What’s the approximate cost of seawalls?
It can vary substantially, but as an example the recent upgrade at Paekākāriki cost more than $1m for a 500 metre length that already had rock toe protection in front of the existing timber wall (because it already had rock in front of it, no resource consent was required from Greater Wellington Regional Council for the wall).
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24. What is the value of properties affected by the shoreline projections?
Around $1.6 billion, based on Quotable Valuations.
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25. How do I know when my property will be at risk?
The coastal hazard risk assessment looked at the whole Kāpiti Coast, not individual properties. Some properties may be affected earlier than the 50 and 100 year time frames used for shoreline projections.
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26. What can I do to dispute the shoreline projection for my property?
The shoreline projections are modelled scenarios undertaken at a local level. Individuals can pay for a site or property-specific assessment to be carried out (e.g. to input into the District Plan Review), but would need to supply evidence for consideration by Council and peer review.
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27. If nothing is done, will homes be lost to the sea?
If the shoreline projections prove accurate this could happen to some homes, if alternatives such as relocating them are not an option. Severe storms in 1968 caused some Kāpiti coastal homes to be lost to the sea and this could happen again.
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28. Is Kāpiti more affected than other parts of New Zealand?
Kāpiti has been built up around a long, narrow strip of coastline that is almost fully developed with residential properties. By global standards our coastline is particularly dynamic, having gone through widespread change in the past few thousand years at a rate not diminished since European settlement. It is more prone to erosion than other areas with different shoreline characteristics such as New Plymouth which is rockier.
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29. What do the shoreline projections mean for home owners or buyers?
At this stage the shoreline projections are hazard information only. Current District Plan rules apply until the new Plan is in place (the earliest that new rules will have any effect is September 2013, after all submissions have been considered, hearings completed and any appeals resolved). The risk information will be used immediately when any new subdivision applications are considered and will mean new buildings receive notice about any relevant hazards. People thinking of buying, developing or renovating a coastal property should be aware of the coastal hazard risk before making any decisions.
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30. How do other councils’ 100 year assessments compare?
The assessments looked at similar themes including long-term trends and dynamic fluctuations, but used different methods depending on the nature of the coast, type of data available and resourcing.
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31. How was the coastal hazard assessment peer reviewed?
Coastal hazard assessment is a long and complicated process, and peer review has taken place throughout.
The methodology to be used in Council’s 50-year assessment was peer reviewed and then consulted on publicly in 2005. That assessment was commissioned before the requirement for a 100-year assessment came in via the New Zealand Coastal Policy Statement in 2010. The same methodology was used in the 100-year assessment completed in August 2012.
Throughout the process the assessment reports have been peer reviewed by:
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Dr Mike Shepherd (coastal geomorphologist, Massey University)
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Mr John Lumsden (coastal engineering consultant)
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Dr S Ganesalingham (mathematician).
Review on specific aspects was received from practitioners with direct involvement with coastal process or management investigations on the Kāpiti Coast over the past 30 years including:
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Dr Jeremy Gibb (coastal management consultant)
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Professor Bob Kirk and Dr Martin Single (coastal geomorphologists, University of Canterbury)
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Mr Richard Reinen-Hamill, Senior Coastal Engineer (Tonkin and Taylor Ltd).
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32. Why wasn’t the community forewarned shoreline projections would be included in LIMs?
Council has been clear in its strategies and planning for several years about its concern regarding climate change effects. Additionally since 2004, LIMs have noted coastal hazards are being reviewed. Draft shoreline projections from the assessment were shown to around 200 people at natural hazard information exchanges which were publicised and held around the region in May and June 2012. Council is legally required to include hazard information it holds in LIMs, but speculating beforehand on what that information might be was not considered useful.
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33. Are there currently setback lines in Kāpiti?
Coastal setbacks (i.e. development restrictions) have been in the District Plan for areas south of Raumati since 1981. This followed severe coastal erosion in Paekākāriki and Raumati in 1968.
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34. What kind of input can people have to the District Plan Review provisions?
People may make a written submission on coastal environment provisions in the Proposed District Plan - the closing date is Tuesday 2 April 2013, 5pm. You can specify that you want to speak to your submission at the Council hearing. Submissions on all other provisions in the Proposed District Plan closed on 1 March 2013.
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35. What about cross-leased sections?
Owners with property where any part of it falls within the 50 or 100-year line have been sent information on the new hazard risk information and this will go on any LIM requests for their property.
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36. Why are some coastal erosion projection lines on land higher than projected sea level or higher than properties behind them?
The lines project coastal erosion not flooding. Erosion can affect elevated property when water undermines land stability. Cliffs and escarpments are examples of the effect of coastal erosion, which may not result in flooding on the elevated land or the properties further inland. See photo attached to FAQ 3 which demonstrates this difference.
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37. How are LIMs prepared?
Information about a property is put together on request using the most up-to-date data available at the time. Therefore, a LIM for a particular property can change each time it’s requested if new data has come through.
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38. When will the rules in the new District Plan take effect?
The new coastal hazard rules relating to building, development and subdivision along the coast will only come into effect once the new District Plan becomes operative. Effectively, this means the earliest date they could take effect would be about September 2013 once consultation has been undertaken and the Council’s decision-making process has been completed. In reality, it is likely there will be appeals on aspects of the proposed District Plan which will further delay the date when the rules will take effect.
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39. What is a Certificate of Compliance and how does it operate?
A Certificate of Compliance (CoC) is a written confirmation from Council that a particular project is fully in accord with the provisions of the operative District Plan and can be undertaken at the time of the application for CoC without the need for a Resource Consent. However, if the application is made after a proposed District Plan is notified and the proposed activity could not be undertaken lawfully without a Resource Consent under the proposed District Plan, Council cannot issue the certificate.
It is therefore possible to obtain a CoC for a proposed building before lodging an application for a building consent. A CoC is issued if plans of a building footprint, building envelope, total floor area and position on a lot are provided and Council is satisfied they do not breach any existing rules in the operative District Plan. A proposal also needs to be in accordance with any provisions of the proposed District Plan which have legal effect (coastal hazards rules do not have legal effect yet).
Most CoCs are valid for five years. This means even if decisions are made on coastal or any other rules in the proposed District Plan during the period for which the CoC has been issued, the CoC can be treated as if it were an appropriate Resource Consent for the proposed building. The building works must strictly follow the footprint, envelope, floor area and position on the lot approved in the CoC.
Before a District Plan becomes operative it goes through a lengthy process of public consultation and, potentially, appeals. As a result, the Plan which finally becomes operative can be different from the one that is proposed at the time the application for a CoC is made. Any changes made to the Plan after the date of application do not affect the validity of the CoC.
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40. I’ve heard the proposed District Plan provisions have some weight in relation to consents even before it becomes operative. What does that mean if I want to build?
If your proposed building/development meets the permitted activity standards of the operative District Plan and the relevant code requirements, you will be able to get a consent right up until any relevant part of the new Plan becomes operative.