Local Govt | National News Video | Parliament Headlines | Politics Headlines | Search

 


Wellington - Highest Rate of Sea-Level Rise in NZ

Wellington - Highest Rate of Sea-Level Rise in NZ

Two reports released today show Wellington has the highest rate of sea-level rise in New Zealand and highlight areas in the region that are vulnerable to coastal flooding over the next 100 years.

The reports, commissioned by the Greater Wellington Regional Council (GW), look at sea-level rise and coastal flooding from storm events in the Wellington region including current trends and future scenarios based on those trends. Wave heights, wind strength, storm-tide levels, sea-level variability and large-scale storm events are all assessed.

Findings from the studies and the implications they are likely to have on the Wellington region’s coasts, communities and local authorities were presented today.

It was found that the Wairarapa and south coasts are exposed to the largest waves, with average wave heights of over 6.0m in places during some of the computer-simulated storm events, but that these areas experience lower storm tides*. In contrast, the Kapiti Coast experiences smaller waves, but is subject to larger storm tide inundation due to shallower sea floors near the coast.

Another key finding in the report is that Wellington Harbour has experienced an average rise in sea level of about 2mm per year over the past 100 years. Most of this rise is due to climate change but is being exacerbated by subsidence of the city over the past decade, caused by slow-slip seismic events from deep tectonic plate movements. Projections for the end of this century indicate sea level in Wellington region could rise by 0.8m by the 2090s or 1.0m by 2115.

The reports will be useful for anyone involved in urban planning to help make decisions around the development of buildings, roads and other infrastructure in low-lying coastal areas.

“It will be especially important to have the reports to inform the new 10-year regional plan we are currently putting together,” says GW Senior Hazards Analyst Dr Iain Dawe.

“We need integrated coastal management in the region with authorities working together to plan for natural disasters in the future. It’s critical we have a long-term view of issues such as sea-level rise that will impact our coastal communities.”

The reports were written by NIWA scientists (Rob Bell, Emily Lane, Scott Stephens, Richard Gorman and David Plew) with consultants Prof. John Hannah and Dr Jeremy Gibb. Funding assistance was provided by Wellington City and Kapiti Coast District Councils.

The sea-level rise report is available at www.gw.govtnz (look under ‘Plans & Publications/Document library/Hazards’). The report on storm tide and coastal flooding will be available on this site soon.

* Storm tide results from a combination of low air pressure, high waves and strong onshore winds that push water up against the shoreline, causing a temporary rise in water levels for up to three days When this occurs at high tide, it can cause coastal flooding and damage in low-lying areas, such as that which occurred in Wellington’s Owhiro Bay a few weeks ago.


QUESTIONS & ANSWERS

1. Is the sea rising?
Yes. Tide gauge recordings from the mid-19th century and satellite measurements from the early 1990s all show that the sea is rising. In New Zealand there are tide gauge recordings from all the main ports, including Wellington, that date back over 110 years.
2. How fast is the sea rising?
The long term record from New Zealand shows that sea level has been rising at an average rate of 1.7mm/yr. However, in Wellington it is slightly higher due to subsidence and is currently increasing at 2.03mm/yr. This equates to a little over 0.2m over the last 100 years alone.
3. What is storm-tide?
Storm-tide results from a combination of low air pressure, strong winds and high waves that act together to raise the water level at the coast. The effect, which can last up to three days depending on the severity of the storm and when it coincides with high tide, can cause coastal flooding, erosion and damage from debris being thrown up by wave activity.
4. What areas are vulnerable to coastal flooding?
All low-lying areas around the coast are subject to storm-tide flooding but this vulnerability will increase due to sea-level rise. Areas at risk include:
• the mouths of rivers and streams including the Otaki, Waikanae, Hutt and Whakataki Rivers
• low-lying parts of Wellington and Porirua Harbours, as well as the lower Wairarapa Valley including Pauatahanui, Eastbourne Bays, Petone and Lake Onoke
• areas subject to severe erosion such as Paekakariki, Raumati South and Te Kopi.
5. Why is the sea rising?
Water expands when it is heated and this is what is happening to the oceans due to global warming. Temperature measurements show Earth has warmed by an average of 0.7oC over the past century and this in turn is warming the seas, causing them to expand. Global warming is also causing increased melting of the polar ice caps and glaciers that is increasing ocean volumes.
6. Will storms become more frequent due to climate change?
Current research indicates that while storms in New Zealand are not likely to become more frequent, the storms we do get may increase in severity. Thus, storm-tide events may become longer, increasing the likelihood of coastal flooding and erosion.
7. What are local authorities doing?
Greater Wellington Regional Council along with City and District Councils are in the process of identifying areas vulnerable to coastal hazards and are developing plans to manage high hazard areas. Guidance documents have also been produced by central government to assist local authorities in managing climate change and coastal hazards. See the Proposed Regional Policy Statement on www.gw.govt.nz (look under ‘Plans & Publications/Regional plans, policies & strategies’).

8. What can I do to be better prepared?
Have a household plan that includes how to contact each other in an emergency and how you would manage if you were cut off due to coastal flooding. Put together a emergency kit that contains enough food and water, essential medications and toilet paper to last three days, as well as a battery radio, torch, spare batteries and first aid kit. For more information check out: www.gw.govt.nz/emergencies or www.civildefence.govt.nz


© Scoop Media

 
 
 
 
 
Parliament Headlines | Politics Headlines | Regional Headlines

Gordon Campbell:
On The Team Behind Trump's Throne

Forget the Putin factor. Daily, the team of charlatans, bigots and stunningly ignorant crackpots that Trump is appointing to head key federal agencies is just as alarming. These are positions with vast power and budgetary discretion over policies that stand to affect tens of millions of vulnerable Americans. Sad! More>>

 

Gordon Campbell: On Bill English, Abroad

If David Cameron was the closest thing John Key had to a political mentor, their successors also share a whole lot in common. Theresa May and Bill English were both propelled into the top jobs as the result of unexpected resignations, and without much in the way of credible competition from their colleagues... More>>

ALSO:

Pike River: Labour Bill To Override Safety Act For Mine Entry

“Bill English has been hiding behind the legal excuse that any attempt to re-enter the mine to recover the bodies might place the mine’s owner, Solid Energy Limited, and its directors in breach of the Health and Safety at Work Act 2015." More>>

ALSO:

Gordon Campbell: On Populism And Labour 2017

For many people on the centre-left, populism is a dirty word, and a shorthand for the politics of bigotry. In this country, it has tended to be equated with the angry legions of New Zealand First. Who knew they were not just a reactionary spasm, but the wave of the future? More>>

Oxfam: 30% Of NZ Owns Less Wealth Than Our Two Richest Men

The research also reveals that the richest one per cent have 20 per cent of the wealth in New Zealand, while 90 per cent of the population owns less than half of the nation’s wealth. The research forms part of a global report released to coincide with this week’s annual meeting of political and business leaders at the World Economic Forum in Davos, Switzerland. More>>

ALSO:

Hospitals: Resident Doctors Set To Strike Again

Despite discussions between the DHBs and NZRDA over safer hours for resident doctors progressing during the last week, the strike planned for next week appears set to proceed. More>>

ALSO:

Not So Super Fund: More Burning Ethical Questions For Steven Joyce

Greens: Radio New Zealand reported this morning that the New Zealand Superfund has $77 million invested in 47 coal companies that the Norwegian Government’s Pension Fund – the largest sovereign fund in the world – has blacklisted. More>>

Activism: Greenpeace Intercepts World’s Biggest Seismic Oil Ship

Greenpeace crew have made contact with the world’s biggest seismic oil ship after travelling 50 nautical miles on two rigid-hulled inflatables off the coast of Wairarapa... Greenpeace radioed the master of the Amazon Warrior to deliver an open letter of protest signed by over 60,000 New Zealanders. More>>

ALSO:

Gordon Campbell: Why Tax Cuts In 2017 Would Be A (Proven) Bad Idea

Ever since the world fell prey to the mullahs of the free market in the 1980s, no amount of real world evidence has managed dispel one key tenet of their economic faith. Namely, the idea that if you cut income taxes and taxes on small business, a wave of individual enterprise and entrepreneurial energy will thus be unleashed, profits will rise and – hey bingo! – the tax cuts will soon be paying for themselves ... More>>

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
More RSS  RSS
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news