“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 rising sea levels with a sense of certainty while being prepared for uncertainties.
It mentions the many hazards that continuous sea-level rise brings, such as the flooding of low-lying lands and 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 groundwater problems will be common in reclaimed lands from the sea.
Although the sea-level rise is unstoppable and steady, according to the paper, there is enough time to prepare for it. 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 these is setting coastal hazard zones based on projections of future flooding and erosion. Rising sea levels must also be included in government policies. New Zealanders value their coasts and their natural beauty so much that most houses are relatively close to the sea, while some live along the coasts.
Infrastructures like roads and 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.
Other consequences of climate change include changes in wind and rainfall patterns, which can either increase or decrease the impacts of sea levels.
This paper highlights the need to prepare, 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 follows up 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 areas can be mapped out, how councils have begun planning for it, and lastly, identify the gaps with regard 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 to sea-level rise; however, every country or area 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, and the frequency of tropical cyclones and rainfall is also considered. Then, there is the question of the acceptable level of risk. Should the runway be built high enough never to 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 since then. They built the Thames barrier to a high standard that modification is not expected until 2070.
Both examples exercise mitigation and adaption, using a unique approach to each situation.
The report does not cover the reduction of greenhouse gas emissions, effects of climate change such as rainfall patterns or acidification of the oceans, impacts of sea-level rise on 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, usually occur twice a year when the earth, sun, and moon are aligned, and the moon is closest to the earth.
- Storm surges are caused 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 Giselle, 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, long-term weather patterns like El Nino and La Nina also affect the rise and fall of sea levels, falling during El Nino and rising during La Nina.
- At times, a combination of high tides and storm surges can overwhelm stormwater systems and cause flooding in coastal areas, like what happened in Auckland in January 2011.
Effects of warming temperature
As the atmosphere warms, rainfall is projected to increase in intensity. 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. Cyclones that form in the South Island are projected to 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. However, natural and built defences like sand dunes, wetlands, cliffs, and tidal barriers can be effective barriers. These barriers, however, need upkeep as they can also erode or collapse.
The paper shows records of sea-level rise in four NZ ports. It shows the year recording began and the dates of the highest sea levels recorded. Today, however, sudden sea-level rises, which happen, for example, every three months, twice a month, or weekly, are occurring more frequently than in the past.
Erosion. Rising sea levels will cause erosion 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 the sea level rises, causing surface ponding and damaging buildings and infrastructure. Liquefaction can also occur during earthquakes, such as in Christchurch. Rising sea levels can cause salt-water intrusion and damage aquifers.
The paper mentions the use of mapping systems, such as LiDAR, which can accurately measure the elevations of land areas, particularly along the coasts. These systems and technology can assist the government in planning and preparing for sea-level rise, considering coastal margins, managing the coasts, and making relocation plans when necessary.
Conclusion and recommendations from the commissioner
Climate adaptation and mitigation are the best options. Mitigation involves reducing the emission of carbon dioxide and other greenhouse gases as soon as possible to slow down climate change.
Climate adaptation involves dealing with the consequences of climate change. Regarding the rise in sea levels, there is still time to plan and develop sound policies. Thus, it is good to focus on preparation rather than rushing to act.
Regarding the existing two documents, the 2010 New Zealand Coastal Policy Statement (NZCPS) and the 2008 MfE Guidance Manual, which provides guidance to councils on how to deal with sea-level rise, do these documents need revisions or is a new policy needed that will deal directly with the hazards of rising sea levels and how it will affect the community?
Accurate data gathering using mapping systems and a national repository accessible to the public is needed.
Projections of the Intergovernmental Panel on Climate Change (IPCC) regarding the rise of sea level 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
The government and councils need to answer this question 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 exchanging information between them should be encouraged.
In developing strategies for coastlines, the question remains, ” What is the best way to protect the coast, and who will pay for it?”
Strategies would need to deal with uncertainties while considering an adaptive management approach.
Lastly, the paper recognized that adaptation to sea-level rise and mitigation 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 to 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, there is still time to prepare, as financial risks brought about by sea-level rise require input from the public, government, and private institutions like banks and infrastructure providers.
The paper provides interesting information on the effects of sea-level rise in the New Zealand context. It discusses how the country is dealing with it and what could be done about it.
It will be worthwhile to read the report and get some facts and ideas on climate change, climate adaptation and mitigation processes.
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PHOTO CREDIT: Featured Image: Cathedral Cove by Karl Hipolito