Climate Adaptation and Mitigation Needed for NZ’s Rising Sea-level Certainty and Uncertainty

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“It is certain that the sea is rising and will continue to do so for centuries to come. But much is uncertain – how rapidly it will rise, how different coastal areas will be affected, and how we should prepare. And we do need to prepare. “

– The Parliamentary Commissioner for the Environment Report

Preparing New Zealand for rising seas: Certainty and Uncertainty,” a report by the Parliamentary Commissioner for the Environment published in 2015,  talks about how New Zealand can prepare for the rising sea level with a sense of certainty while being prepared for uncertainties.

It mentions the many hazards that the continuous sea-level rise brings, such as the flooding of low-lying lands, coastal areas, erosion of beaches and soft cliffs, and saltwater intrusion of aquifers and groundwater.  It evaluates that not all impacts are equal, open coasts are more vulnerable than enclosed bays, and while groundwater problems will be common in reclaimed lands from the sea.

Although the sea-level rise is unstoppable and steady, there is enough time to prepare for it, according to the paper. The following paragraphs are some of the points that the paper discussed robustly.

The central government of New Zealand under the Resource Management Act provides directions for councils on what can be done with these hazards. One of which is the setting of coastal hazard zones based on projections of future flooding and erosion. There is also a need to include the sea-level rise into government policies. New Zealanders value their coasts and its natural beauty so much that most houses are relatively close to the sea, while some live along the coasts.

Infrastructures like roads, water systems are also built on these coastal areas with storm surges and high tides being considered. Because of rising sea levels, these infrastructures are in danger as waves are predicted to reach inland areas, resulting in flooding. Rising sea levels will also cause coastal erosion and receding shorelines but protective barriers like sand dunes, sea walls, and mangroves can help lessen its impact.

Then there are other consequences of climate change like the change of wind and rainfall patterns which can either increase or decrease the impacts of sea levels.

The need to prepare is highlighted in this paper, but technical complexities from scientific reports and data gathering, plus the fact that the extent and timing of the impact are still unknown create some uncertainty.

This paper is a follow-through on the 2014 report released by the Parliamentary Commissioner for the Environment.  The 2014 report intends to explain in clear terms to New Zealanders the science of climate change, how it will affect them, how low-lying can be mapped out, how councils have begun planning for it, and lastly identify the gaps with regards to the direction provided by the Central government.

It reveals that New Zealand’s sea-level rise is in line with the Global average sea-level rise of about 20cm from the beginning of the 20th century.

Adapting to sea-level rise

Bangladesh and Kiribati are two countries identified as most vulnerable by sea-level rise, however, every country or area that is bordered by the sea is also at risk.

Examples of adaptations can be seen in Brisbane Airport. Because it is low-lying and close to the coast, the height of the runway is adjusted against the calculated height of storm surges and waves, the frequency of tropical cyclones and rainfall is also considered. Then there is the question of the acceptable level of risks. Should the runway be built high enough so that it will never be flooded or just high enough to tolerate a once a month flooding?

In London, the Thames barrier began operating in 1984 to protect the city from tidal and river flooding. The incidence of flooding has increased snce then. They built the Thames barrier to a high standard that modification is not expected until 2070.

Both examples are an exercise of mitigation and adaption, using a unique approach to each situation.

What the report does not cover are the following: the reduction of greenhouse gas emission, effects of climate change such as rainfall patterns, or acidification of the oceans, impacts of sea-level rise to ecosystems and landscapes, and ownership of the foreshore and seabed in relation to the treaty of Waitangi.

What’s in store for the future

According to the paper, the IPCC projected the sea level under different scenarios from strong mitigation to lesser mitigation of greenhouse gases emissions, the result: sea level will indeed ‘likely to rise’ and will continue to at varying degrees. Stronger mitigations will see a higher increase and lesser mitigations will have a lower increase in sea level rise, however, the sooner greenhouse gas emissions are curbed the greater its effect in the long term.

In New Zealand, the rate of sea-level rise is about the same rate as the global average.

Factors that influence the sea-level rise in New Zealand are:

  • High tides, particularly king tides that usually occur twice a year when the earth, sun, and moon are aligned, and the moon is closest to the earth.
  • Storm surges, brought by high winds that cause the sea to bulge in long slow waves, one of interest was the 88-centimetre storm surge in 1968 in Tauranga Harbour. The surge was brought by cyclone Gisell, the largest one recorded in New Zealand. The waves reached up to 12 meters in Cook strait sinking the Wahine.
  • Aside from high tides and storm surges, and long-tern weather patterns like the El Nino and La Nina also affect the rise and fall of the sea levels. Falling during El Nino and rising during La Nina.
  • At times a combination of high tides and storm surge can overwhelm stormwater systems and cause flooding in coastal areas like what happened in Auckland in January 2011.

Effects of warming temperature

Rainfall is projected to increase in intensity as the atmosphere warms. Increased rainfall is projected on the west side of both islands, and the south of the South Island. Winds are expected to become more prolonged and intense especially in the winter.

Storm patterns are likely to change. It is projected that cyclones that form in the South Island will become more intense.

3 Types of coastal hazards caused by sea-level rise:

Flooding. Low-lying areas, coastal areas, and unsheltered coasts are most vulnerable to flooding. But natural and built defences like sand dunes, wetlands, cliffs, and tidal barriers can be effective barriers. These barriers, however, needs upkeep as they can also erode or collapse.

The paper shows records of sea-level rise in four NZ ports. It showed the year recording began and the dates of highest sea levels recorded. Today, however, the occurrence of sudden sea-level rise, that happens, for example, every 3 months, twice a month or week, is happening more frequently than what is experienced in the past.

Erosion. Rising sea levels will see erosions in many places and coasts around the country as can be seen now in Waihi beach, Haumoana in Hawkes bay, and the beach road south of Oamaru.

Groundwater problems. The water table can rise as a sea-level rises, and it can cause surface ponding, damaging buildings, and infrastructure. Liquefaction can also occur during earthquakes like what happened in Christchurch. Rising sea levels can cause salt-water intrusion and can damage aquifers.

The paper mentions the use of mapping systems, such as the LiDAR which can accurately measure the elevations of land areas, particularly along the coasts. Use of mapping systems and technology can assist the government in planning and preparing for sea-level rise and consideration of coastal margins, management of the coasts, and relocation plans when necessary.

Conclusion and recommendations from the commissioner

Mitigation and adaptation are the way to do. Mitigation by reducing the emission of carbon dioxide and other greenhouse gases as soon as possible to slow down climate change.

Adaptation is dealing with the consequences of climate change. With regards to sea-level rise, there is still time for planning and develop good policy surrounding the issue, thus it is good to focus on preparation rather than rushing to do something about it.

With regards to the existing two documents: the 2010 New Zealand Coastal Policy Statement (NZCPS) and the 2008 MfE Guidance Manual that provides guidance to councils on how to deal with sea-level rise, do these documents need revisions or a need for a creation of a new policy that will deal directly with the hazards of rising sea levels and how will it affect the community.

There is a need for accurate data gathering using mapping systems and a national repository for it accessible for the public.

Projections of the Intergovernmental Panel on Climate Change (IPCC) with the sea level rise should be contextualised in New Zealand for its application while serving as a guide and incorporated into the councils’ planning.

How far ahead to plan

This is the question that the government and councils need to answer regarding urban and infrastructure planning while considering scientific and technical assessments.

There is also a suggestion that hazard information is included in the Land Information Memoranda (LIMs) of affected properties, and property owners should have the right to clear and accurate information as soon as it comes.

Active engagement with the community should be sought. They are experts in their local community and area and an exchange of information between them should be encouraged.

In developing strategies for coastlines, the question, “what is the best way to protect the coast and who will pay for it?” remains.

Strategies would need to deal with uncertainties while considering an adaptive management approach.

Lastly, the paper recognized that adaptation to sea-level rise and mitigating will be costly. When all information is provided to the community regarding its hazards and the best approach to take, decisions can sometimes be left on the individual or community on what to do about it. Building stronger and bigger defences is one way, while a managed retreat can also be an option.

In New Zealand, there is an underlying expectation for the government to provide financial assistance when natural disasters hit.

However, as the paper states earlier on, there is still time to prepare as financial risks brought about by sea-level rise require inputs from the public, government, and private institutions like banks, and infrastructure providers.

The paper provides so many interesting information on the effects of sea-level rise in the New Zealand context. It talks about how the country is dealing with it and what could be done about it.

It will be worth your while to read the report and get some facts and ideas on climate change, climate adaptation and mitigation processes.

CLICK on the button below to get a copy of the research report.

PHOTO CREDIT: Featured Image: Cathedral Cove by Karl Hipolito

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