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Sea level rise is not science fiction – it is my children's future


Defending buildings against the sea is a short term and expensive solution. The massive defenses in the Netherlands won’t be practical in New Zealand – our fault lines and deeper oceans make these defenses more complex and riskier.


What happens to Wellington if we build a massive sea wall which then cracks and fails during an earthquake? The city would be flooded on top of all the other damage.


Defense is generally only cost effective when retreat is not an option – when there is no higher ground to move to. This is the case in the Netherlands where the entire country is a flat floodplain. In Wellington we have lots of lovely hills that provide many options for us to move to higher ground. Retreat will be much cheaper than defending, if it is planned well in advance.


Abandoning buildings and other assets is only expensive if those buildings still have lots of useful life in them. Once a building has reached the end of its useful life the choice is

between renovating in that location or rebuilding elsewhere – the cost difference is minimal. It is council’s role to provide property owners with reliable information to support them in making sensible decisions. Council should ensure property owners are informed of the risks of sea level rise and as far as possible allow them to make their own decisions. If owners decided to stay and defend their assets that risk should be borne by them, not by ratepayers.


Insurance companies will also be sending strong signals to owners about the risk that applies to their property through rising premiums. It is inevitable that some buildings will become uninsurable.


Scroll down to read the full policy document for adapting to sea level rise.

Here are the key points:


  • Long-lived infrastructure and heritage public buildings should not be placed on sites which are vulnerable to sea-level rise within at least the next 200 years – i.e. not within ~5m of current sea levels.

  • New residential development, including services such as local roads and sewer and water services, should not be placed on land that is not expected to survive for more than 70 years, perhaps within ~1m of current sea levels. (Commercial and industrial owners have more sophisticated risk management procedures so they should be allowed to build on lower land, at their own risk.)

  • For each property, the LIM should show the amount of further sea-level rise that is likely to make the property uninhabitable, and should refer the reader to the latest available IPCC report to understand how many years that might mean.

  • To minimise the risk of the Council being held liable in future for property owners’ decisions, it should be a condition of every resource and building consent, and recorded on the LIM, that the owner states that they have considered the consequences of sea-level rise and accept that they are solely responsible for the decision to undertake the work.

  • Council should develop a complete list of all assets that provide services to private property (local roads, sewer and water lines, and so forth), and should set down criteria for when those assets will be abandoned in the face of sea-level rise.

  • For new developments, we should not permit any kind of defence; if the development requires protection from the start, it should not be undertaken in that location.

  • For protecting existing assets, Council should develop specific plans for each area. Soft defence approaches should be identified, and planned to be used until a certain amount of sea-level rise has occurred. Hard defences such as sea walls should be paid for by the private owners who benefit from them, subject to resource consent (these defences have significant negative impact on the coastal ecosystem).


Sea level rise – policy document

1. Background


Property rights

Owners of land and other property receive the primary benefits from that property. In fairness, they should also bear the primary costs. We do not expect the community to pay for the periodic painting of someone’s house: likewise, we should not expect the community to pay for the costs of protecting that house from sea-level rise, or the loss if the house is destroyed.


Protecting against bad outcomes is the usual function of insurance, not of councils. If the risk is high, the insurance premium will be high. If a bad outcome is certain, insurance is not designed to cover it, and will not. In all of these cases, the cost should fall on the property owner.


But councils should not create a loss by trampling on property rights and forcing owners to abandon existing assets.


Both the benefits and the costs of private property are passed on when the property is sold to new owners. If the parties are well-informed, the price will reflect whatever is known about the prospects for the property, including climate change effects. The Land Information Memorandum is one mechanism for informing the parties, and council should ensure that the information on a LIM reflects what is known, but is not biased towards either the buyer or

the seller, and does not make claims which go beyond what is known.

Time horizons

Climate change is real, and rising temperatures and sea levels are real. But they are rising gradually over many decades. The next decade is going to look pretty much like the last decade, but the next century will not look like the last century. Decisions with long time horizons need to consider the relevant time scale.

  • Commercial investments typically have a fairly short horizon. Rental yields for commercial property in Wellington have been above 5%, so that an office building will pay for itself in 20 years or less (the profit comes from its continued use after that). Most investments in industrial plant have shorter payback times than this.

  • Houses should last longer. The Building Act requires structural elements to have a life of at least 50 years. A house that makes it to a century will almost certainly have been extensively renovated, perhaps more than once. If the house was not viable at the time of renovation, the owner would have left it to decay or knocked it down and replaced it. Demolishing a house that is close to that point in its life does not create an appreciable loss and is not something that we should fret about.

  • Some public infrastructure should have a much longer life, measured in centuries. Major roads, railway rights of way, major airports, sewer and water supply infrastructure are all extremely expensive and disruptive to move. Public buildings that speak to our history as a nation (perhaps Parliament, Te Papa, the Town Hall, and a handful of others) should be retained far longer than a purely commercial assessment would justify. Many public buildings, however, are simply utilitarian and can be easily replaced elsewhere if required. These buildings will in fact be replaced from time to time, sea-level rise or no.


All of New Zealand’s existing infrastructure and housing has been constructed in the last 200 years, almost all of it in the last 100. Most of it is likely to be rebuilt or abandoned in the next 100 years, with or without sea-level rise. The cost has not bankrupted us, and the future cost will not bankrupt us either. The additional cost of adapting to sea-level rise, above what would be spent anyway, will be relatively small; this is nothing like rebuilding after an earthquake.

2. Policies: what I support

Sea-level rise is happening gradually over many decades. This means that the available options are very different from dealing (for example) with preparing for earthquakes.

Where infrastructure should go

Long-lived infrastructure and heritage public buildings should not be placed on sites which are vulnerable to sea-level rise over at least the next 200 years. Because the amount of sea-level rise over that time is much less certain even than during this century, I would favour a generous margin: new long-lived infrastructure should not be placed lower than 5m above sea level*.


This does not mean that existing infrastructure should be removed while it is still useful. If it has to be replaced, we should do that when necessary, not before.


There are immediate implications: for example

  • the CBD route proposed for light rail is unacceptable. If light rail is to be built, it must be on a higher-level route. Implications of sea level rise must be considered in the business case comparing light rail with alternative modes of mass transit.

  • the unsafe buildings in Civic Square should only be strengthened if the cost is justified by the likely useful life that will be added before inundation, at 80cm above current sea levels. Alternatively, they should be replaced with new buildings on higher ground. As a second benefit, this takes the buildings away from the earthquake-prone ground on which they now sit.


Regulation of private property

Much of this is governed by the District Plan, which is updated at intervals. Some of these policies reflect issues that I would like to see addressed when the plan is next revised.


New residential development, including services such as local roads and sewer and water services, should not be placed on land that is not expected to survive for more than 70 years (say, with less than 0.7 m freeboard above existing storm surges). This allows for a reasonable useful life for housing.


For each property, the LIM should show the amount of further sea-level rise that is likely to make the property uninhabitable, and should refer the reader to the latest available IPCC report to understand how many years that might mean. Council should not offer its own estimate of the lifetime in years, and should not state or imply that particular properties are at risk beyond that factual statement. This ensures that both buyers and sellers have access to property-specific information which is neutral and factual, and can form their own views of whether they wish to own the property and at what price.


Owners of industrial and commercial property should be permitted to develop it as they see fit (subject to other planning provisions).


To minimise the risk of the Council being held liable in future for property owners’ decisions, it should be a condition of every resource and building consent, and recorded on the LIM, that the owner states that they have considered the consequences of sea-level rise and accept that they are solely responsible for the decision to undertake the work.

Protection and managed retreat

When existing assets that are vulnerable to sea-level rise have reached the end of their life, they should be removed and not replaced. However, private and public assets that still have value may be worth protecting to avoid having them prematurely destroyed.


Protection of private assets should be at the cost of the owners, not the community. Council should not lightly prevent property owners from protecting their property at their own cost. In some cases, it may be useful for the Council to play a coordinating role for a neighbourhood, and pay for the protection by a targeted rate on the properties that benefit. Where protection works benefit both public and private property, the costs should be apportioned fairly between the property owners and ratepayers in general.


Council should develop a complete list of all assets that provide services to private property (local roads, sewer and water lines, and so forth), and should set down criteria for when those assets will abandoned in the face of sea-level rise. Those criteria should be expressed in terms of the amount of sea-level rise, not in terms of dates, since it is the sea level that determines when it is no longer practical to preserve the asset. This information will provide a much clearer sense of when retreat will become necessary.


The cost of abandoning a property should fall on the property owners. Only exceptionally should any contribution come from ratepayer funds (for example, when Council has clearly failed to perform some duty to the property owner). Information on the LIM should ensure that the affected owners were properly informed of the effects of sea-level rise, and that should have been reflected in the price that they paid, which can be expected to decline as a property comes to the end of its life. If they paid more than the property was worth given its expected future, that is not something for which ratepayers should compensate them.

Adaptive approaches

Council is bound by various policy statements of central Government and the Wellington region. Some approaches to dealing with sea-level rise are preferred to others.


Soft approaches, such as adding sand to beaches to raise their level, or planting vegetation to stabilise the shore, are preferred to hard structures such as sea walls. Eventually, all of these defences will be overwhelmed by continuing sea-level rise, but in many cases they can buy additional decades to prevent the premature destruction of existing assets. The character of Oriental Bay, for example, is greatly enhanced by the combination of an (artificial) sand beach and a high strong sea wall.


For new developments, I do not favour allowing any kind of defence; if the development requires protection from the start, it should not be undertaken in that location.


For protecting existing assets, Council should develop specific plans for each area. Soft approaches should be identified, and planned to be used until a certain amount of sea-level rise has occurred. Beyond that point, if assets still remain to be protected, there might be a case for hard protection until the sea has risen so far that this protection can no longer be sustained and the assets must be abandoned.

* Estimates of worst case sea level rise by 2300 under a moderate emissions scenario were 5.31m, 6.96m, and 5.27m in this review paper. (95th percentile at RCP4.5)

Mapping Sea-Level Change in Time, Space, and Probability, Annual Review of Environment and Resources Volume 43, 2018 Horton, pp481-521 https://www.annualreviews.org/doi/10.1146/annurev-environ-102017-025826

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