Threats of sea level rise, security implications of climate change

An Otago University research paper warns that the effects of sea level rise will impact most on vulnerable people (that’s likely), while a Defence Assessment “identifies climate change as one of the most significant security threats of our time”.

While it is still debatable how much the sea level is likely to rise there is no doubt it has been (slowly) rising over the past half century.

Some still say nothing should be done about climate change, but academics and officials are at least thinking and writiing reports about possible effects and implications.

RNZ:  Sea level rise threatens major NZ infrastructure – report

The burden of sea-level rise will weigh on the most vulnerable unless a new approach is developed and legislated, a new report says.

The paper, written by University of Otago Associate Professor Lisa Ellis, is part of research from the Deep South National Science Challenge. It looks at how New Zealand distributes the risks of sea-level rise.

It proposes an “ethically robust” policy to adapt to the risks of climate change.

Tens of thousands of buildings, infrastructure including airports, railways, and roads, and more than 100,000 residents are at risk of serious loss and damage associated with sea-level rise within the next century.

Dunedin’s airport is low lying, and has already flooded.

Image result for dunedin airport flooded

Flooding on the Taieri Plain, 1980 (airport in lower half of photo)

Rising sea levels and predicted more rain and storms would make this sort of ‘100 year flood’ more common.

South Dunedin in also low lying (it is reclaimed swamp) and has flooded in recent years.

Prof Ellis said sea-level rise was entirely predictable but if New Zealand was proactive about adaptation to climate change, peoples’ wellbeing would not be threatened.

But she said it was possible existing inequality would be exacerbated and the cost of adapting to climate change would rise if the status quo remained.

Her report recommended a government resource about adapting to sea-level rise nationwide, so community resilience did not vary with ratepayers’ ability to pay.

At local level the public should be engaged as early and deeply as possible.

Also from RNZ:  Sea level rise threatens major NZ infrastructure (audio)

Local Government New Zealand: Young and vulnerable shouldn’t shoulder sea-level rise burden

A report released this morning by the Deep South National Science Challenge supports LGNZ’s call for a national framework to deal with sea-level rise, saying that New Zealand’s youngest and most vulnerable are at risk of shouldering the burden if we don’t act now.

“Preliminary findings from our upcoming sea-level rise report shows that billions of dollars of local government roading, water and public transport infrastructure is at risk from as little as half a metre of sea-level rise.  That’s not including private buildings and houses, including potentially billions of dollars in residential real estate,” says LGNZ President Dave Cull.

“Areas like South Dunedin illustrate just how difficult it is to adapt to climate change without hitting lower socio-economic families in the pocket, so we need a national plan that doesn’t leave anyone behind.”

“Local government stands alongside our communities on the front line in the fight against climate change, but we can’t do it alone – we need central government to set stronger, national rules around risk and liability to property owners in the path of sea-level rise.”

Research from NIWA reveals that sea level rise in New Zealand has increased from 1.7mm a year over the past century, to 4.4mm a year since 1993, which is higher than the global average.  In combination with more severe weather events, storm surges and king tides, sea-level rise presents a huge problem for coastal businesses and residents.

“We need to treat sea-level rise the way we do earthquakes, and that requires a national strategy that gives councils a stronger platform on which to make decisions about building in high-risk areas.”

Ministers of Defence, Climate Change: Defence Assessment on Climate Change and Security Released

Minister of Defence Ron Mark and Minister for Climate Change James Shaw have today released a Defence Assessment on the security implications of climate change.

The Climate Crisis: Defence Readiness and Responsibilities explores the implications of climate change for New Zealand Defence Force operations.

It identifies climate change as one of the most significant security threats of our time, and one that is already having adverse impacts both at home and in New Zealand’s neighbourhood.

“This Government is committed to ensuring New Zealand does its part to address climate change,” says Ron Mark.  “This means both contributing to mitigating climate change itself, and working with our international partners to respond to the intensifying impacts climate change will bring.

“Earlier this year the Government’s Strategic Defence Policy Statement recognised climate change will have a big impact on Defence operations, particularly in the Pacific.

“It proceeded to highlight that disruptive weather patterns are causing an increased frequency and intensity of weather extremes such as cyclones, rainfall events, droughts, and flooding from sea level rise. In addition, the state of the Southern Ocean is changing, meaning our current vessels are getting close to the limits of being able to operate safely.

“Therefore it stands to reason that we needed to look deeper in order to better understand the social and security implications of climate change, and what our Defence Force will face when it responds to these weather events.

“The Coalition Government already has a work programme underway to help alleviate the effects of climate change.  This includes re-energised Pacific policy settings, the development of a new climate change law, and the commitment to make 100 per cent of New Zealand’s electricity renewable by 2035,” says James Shaw.

The assessment has been produced by the Ministry of Defence in consultation with the New Zealand Defence Force, other New Zealand agencies, Pacific partners and academics.

There is certain to be a lot of ongoing talk about the possible effects and implications of climate change and sea level rise, but it is yet to be seen whether there will be any significant action.

Alarm at more Dunedin flooding

In June 2015 a surprisingly bad storm caused bad flooding in the reclaimed but still low low lying south Dunedin area. In the aftermath there were admissions of poor maintenance of drainage systems (storm water drains, mud tanks, screens and pumping stations). Changes were made with assurances things would work better in the future.

A near record 160.2 mm of rain fell in a day then.

Leading up to yesterday, in January this year, there was low rainfall of 26.4 mm (at the University weather station), and most (16 mm) of that was in one day two weeks ago. Things were very dry.

There was ample warning of impending heavy rain, so there was plenty of time to be properly prepared. Yesterday there was 109.6 mm of rain, significantly less than when the 2015 floods happened.

But there was still serious flooding in south Dunedin, not as bad as in 2015 but bad enough to have a state of emergency to be declared and for homes (and a rest home) to be evacuated.

ODT: Stormwater system overwhelmed

Torrential rain overwhelmed Dunedin’s stormwater system yesterday, flooding parts of Mosgiel and South Dunedin and sparking evacuations and road closures.

History repeated itself for many residents, who faced similar flooding in 2015 and wake this morning facing  another clean-up. A state of emergency was declared at 2.20pm. Dunedin  had received 18mm of rain an hour in the previous two hours.

“That is more than our system is designed to cope with, even though it has operated exactly how it is intended to,” Mayor Dave Cull said.

This is an alarming admission.

South Dunedin’s stormwater system was unable to cope with the 2015 deluge, and struggled with the amount of rain which fell in a short time yesterday.

“It was just the sheer volume of rain in such a short period of time meant that some of the groundwater entered the wastewater system, and that’s what caused the problem,” Civil Defence controller Leanne Mash said.

So two and a half years after major floods in part caused by poorly maintained drainage systems, the improved drainage systems still can’t cope with just two thirds of the rainfall.

This is alarming, not just for those who were directly affected by the flooding, but also by at least one ratepayer, me.

How bad will flooding be if we get a repeat of the 2015 rainfall?

South Island flooding effects

A satellite photo of the South Island following the heavy rain and floods shows all the sediment washing out to sea:


Zoomed in to show the Taieri Plain flooding (just to the left of ‘Dunedin’, with the sediment outflow at Taieri Mouth washing up the coast.


I went down the coast to Taieri Mouth on Sunday, the river looked like a swollen sludge outflow. The surf right down the coastline was very dirty.

The sediment from the Taieri River is drifting up the coast towards Dunedin.The Taieri River comes from the Maniototo where there was also heavy rain.

The sediment outflow in the bottom right of the photo is from the Clutha River. There was also flooding upriver there.



From the CawthronEye Satellite.


Edgecumbe flooding

There has been flodding in various parts of the North island over the last couple of days but the worst has been in Edgecumbe in the Bay of Plenty, near Whakatane, where are river stop bank breached and hundreds of houses have been flooded – it looks like up a meter of water in and around properties in the town.

The water is bad enough, but it usually recedes quite quickly, leaving a coating of mud and slime, mixed with fuel and sewerage.

I worked for a week in Mataura after it flooded in 1978. The aim was to assess and try to save home appliances, but it was hopeless. The lower third to a half had been soaked and coated. Fridges and ovens with fibreglass insulation were sodden. It was often a fairly hopeless task, and the occupants were in shock.

I remember floor level bookcases with the books expanded with water and jammed tight. Carpets had to be all ripped out.

So I can imagine what it will be like in Edgecumbe, once people return to their homes.

It can be devastating.

Flooding, slips, rain warnings

Cyclone Debbie that hit Queensland and caused major flodding in northern New South Wales is no longer a cyclone but the resulting weather is causing havoc in the North island.

MetService severe weather warning:

ISSUED BY MetService AT 8:20 pm 04-Apr-2017

Heavy rain for many parts of the North Island and the upper South Island, and strong winds across central New Zealand

A deepening low over the Tasman Sea is forecast to cross central New Zealand overnight Wednesday and early Thursday morning and move away to the southeast later Thursday. Heavy rain has already fallen in many places and is expected to continue until the passage of the low early Thursday morning. The heaviest rain is expected from Northland to Whanganui, including Coromandel Peninsula, Bay of Plenty, the Central North Island High Country, Gisborne, Hawkes Bay,Wairarapa and the Kaikoura Coast. Rainfall totals could exceed 250mm in some areas. There is also potential for thunderstorms and downpours with hourly rainfall rates of 25 to 45mm.

This is a significant amount of rain and people are advised to watch out for rapidly rising rivers and streams, flooding and slips.

In addition, strong southeasterly winds are forecast about central New Zealand. Horowhenua Kapiti Coast, Nelson and Buller are expected to have the strongest winds, where gusts could reach 120 km/h in exposed places for a time during Wednesday. Winds of this strength could cause damage to trees, powerlines and unsecured structures and make driving hazardous.


NZ Herald Live: Weather, rain, flood chaos as Cyclone Debbie wreaks havoc on Auckland, Whanganui, Rangitikei and other parts of North Island, South Island


  • A state of emergency has been declared in Whanganui, with up to 500 people being evacuated this morning.
  • Rangitikei district is also in a state of civil defence
  • Cliff in Auckland’s Kohimarama collapses onto units.
  • Fire services responding to dozens of flooding-related callouts in Auckland as the city is lashed by rain.
  • A heavy rainfall warning applies to the entire North Island and the north and west of the South Island.
  • Some areas may get three times April’s normal rainfall in just 48 hours.
  • Central North Islanders are being told to keep survival items nearby.

Hundreds of residents are being evacuated in Whanganui, a mud slip slammed into homes in one of Auckland’s upmarket suburbs and flooding has closed roads – New Zealanders are waking up to the havoc being wreaked by the tail of Cyclone Debbie.


This is how Cyclone Debbie swung south east after hitting northern Queensland:


The MetService 3 day forecast suggests there could be a lot of rain to come yet, especially in the lower North Island and upper South Island.


Disagreement over Dunedin sea level predictions

Professor Jim Flynn has provoked some discussion after making some radical predictions about potential rapid sea level rises in South Dunedin and the rest of the low lying parts of the city.

These predictions have been disputed by other academics.

ODT: Flynn’s sea level figures disputed

Associate Prof Nicolas Cullen and senior lecturer Daniel Kingston have described the predictions by Jim Flynn as “very unlikely”.

On Monday, Prof Flynn told a Dunedin City Council public forum huge erosion of polar ice that had begun in 2014 meant predictions on the rate of climate change had changed.

He said there were 1932 homes in Dunedin, mainly in South Dunedin, built below 25cm, and a 25cm sea-level rise could occur before 2034.

He said by 2090, South Dunedin would be under 5m of water, along with Forsyth Barr Stadium, the Otago Polytechnic and other low-lying areas.

That’s fairly extreme. Many would claim bonkers, with some justification.

…approached for comment on the predictions, Prof Cullen and Dr Kingston disagreed.

Prof Cullen, whose expertise includes glaciology and climate change, said Prof Flynn’s figures were “questionable”.

He said the observed sea-level rise was 3.4mm a year, which was “quite high compared to historical estimates”.

If that rate continued for the next 20 years, there would be a total 68mm sea-level rise – “quite different”from Prof Flynn’s estimate.

“I agree that there is evidence that the two large ice sheets [Greenland and the Antarctic] may contribute more to sea-level rise in the future than previously thought, but I would think it is very unlikely that South Dunedin will be under 5m of water in 2090.”

Dr Kingston, whose expertise includes atmospheric circulation patterns and climate change, said he agreed with Prof Cullen.

“The numbers in that article, like 5m by 2090, are at the very, very extreme end of what’s likely.”

To Prof Flynn’s suggestion the more recent erosion of polar ice had changed what could be expected in terms of sea-level rise, Dr Kingston said, “I don’t think the matter is settled by any means.”

A rise of 5m would mean the entire West Antarctic ice sheet disappearing, or the entire Greenland ice sheet disappearing.

“The likelihood of that happening by the end of the century is low – not impossible – but the real extreme end of the situation.”

Flynn’s claims may cause some concern. Things like insurance cover and resale values of low lying properties won’t be helped by worst case scenarios being portrayed as likely.

I’m at 100, so way out of the danger zone but even a half metre rise would cause significant problems in the drained wetlands of South Dunedin where flooding cause major problems in 2015.

Jim Flynn can be a very interesting dude but he isn’t helping anyone with worst case claims that amount to scaremongering, but perhaps his aim was to attract attention to a real potential problem with a bit of exaggeration.

The problem is that claims like this are easy to dismiss as nuts.

Dunedin council admits flooding fault

The Dunedin City Council has admitted that a blocked pumping station meant that the flooding in South Dunedin last year was about 20 cm deeper than it would otherwise have been if the pumping station was fully effective.

This was revealed at a public meeting where anger at the council was expressed.

RNZ: Dunedin council concedes flood worsened by faulty pumping station

South Dunedin residents have been waiting for a year for its council to front up for the flooding – and last night it did so en masse. At least eight city councillors, the chief executive and her two deputies were quizzed by 200 locals about what happened last June, and what will stop it happening again.

Chief executive Sue Bidrose told the crowd of 200 people the council had reports showing the flood was caused by more rain falling than the stormwater system was designed to cope with.

But Dr Bidrose made a major concession, saying the council now accepted a key pumping station was blocked, adding an extra 20cm of water to the area.

20 cm makes a big difference as to the severity of flooding or whether houses got flooded at all.

Surrey Street, South Dunedin.

Surrey Street, South Dunedin. Photo: RNZ / Ian Telfer

She said the council was fixing the pumping station, had all the drains and mud tanks in South Dunedin fully cleared and had new procedures when heavy rain was forecast.

Checking that flood protection was in good working order prior to forecast heavy rain seems a fairly basic thing. That new procedures are required to remedy fundamental flaws does not give one confidence in their council.

I think Sue Bidrose is generally doing a good job trying to sort out problems in the council. There seems to be less public confidence in the mayor.

But it will take more than her words to sort out the ill feeling with residents, who said they felt neglected and betrayed by the council, and especially by Dunedin Mayor Dave Cull.

Shortly after the flooding, Mr Cull linked the event to climate change and warned South Dunedin may have to beat a managed retreat.

Local woman Kathinka Nordal Stene said she was shocked Mr Cull undermined the community at the time when it most needed his support.

Kathinka was a neighbour of mine in Central Otago when I was very young and she was quite a bit older. I don’t remember much of her, but good to see her in action on this. Her mother was prominent in  protest against the flooding of Lowburn through the Clyde dam last century.

The ODT also reported on the meeting: Anger about South Dunedin’s future

Unanswered questions about the long-term future of South Dunedin and the city’s response to climate change loomed large at a heated public meeting last night.

Attendees heard about the short-term measures the council had taken or was about to take to ensure South Dunedin’s infrastructure would run at full capacity should there be a repeat of last June’s devastating flood.

But the meeting was at its most heated when the long-term future of the area was discussed. Council representatives said it was too soon to say how it might respond to the difficult issues posed by rising sea levels and groundwater caused by climate change.


…SDAG spokesman Ray MacLeod finished the meeting by praising some of the council’s short-term measures, but had harsh words when it came to what he perceived as a “green” agenda on the council.

This agenda had resulted in a council policy of “strategic withdrawal” from South Dunedin “by stealth”, Mr MacLeod said.

Perhaps a fairly Green leaning council that has been seen to have put a priority on cycleways through South Dunedin (that were poorly designed and had to be rebuilt so fire engines could use the streets) could shift focus to pedal powered boats, although mobility scooters are probably more relevant to South Dunedin than bike power.

Seriously, what is particularly concerning is that a Green council that has stated an importance on preparing for climate change was so poorly prepared for a bit of heavy rain.

Council chief executive Sue Bidrose earlier said there was no such plan, but both she and Mayor Dave Cull, whose speech was read out by Acting Mayor Andrew Noone, said such an option could not be counted out, given the serious threat posed by climate change.

There has been more threat from basic council ineptitude.

But it is no wonder some of the many residents of South Dunedin are concerned about the council not counting out a plan for a “strategic withdrawal” from South Dunedin.

Much of the South Dunedin area was swamp in the 1800s before being drained.

Prior to European settlement, much of the area of The Flat was poorly drained and marshy.

Much of the swampy land of The Flat was drained through the efforts of Chinese settlers were notable among early residents in the St Clair area, and largely through their effort the swampy land inland from the beach was drained and converted into market gardens.

There have been potential problems with drainage, low level land and high water tables long before ‘climate change’ and rising sea levels were raised as a potential future problem.

Dunedin City flooding report

The report on flooding in South Dunedin is included in an Infrastructure Services Committee report:


  1. This report follows the November 2015 report titled “Infrastructure performance during June 2015 Flood event” that focused on the water, wastewater and stormwater networks. Its purpose is to outline the known management challenges with the South Dunedin catchment, the performance of the stormwater infrastructure in South Dunedin during the June 2015 event and discuss the role of mud tanks within that.
  2. Changes in the South Dunedin catchment since the stormwater network was designed combined with operational challenges and ground water levels all contributed to the effects of the extreme rainfall event that occurred in June 2015.
  3. Staff have previously reported the contribution of the pipes and Portobello Road pump station operation to the volume of water on the surface at the peak of the flood. This modelling cannot take into account other influences such as cross catchment flows, the displacement of water by obstacles in secondary flow paths or vehicles, or the increase in hard surfaces across the catchment.
  4. Staff are therefore unable to determine the contribution to the event arising from mud tanks but have mapped mud tank conditions against known flood levels and compared this with predicted stormwater network flooding resulting from a significant rainfall event.
  5. The mapping shows correlation between known and predicted flooding. Flooding below road level would have required ground water levels to drop for it to be absorbed or to be pumped to the road where it could make its way to the system.
  6. In investigating mud tank performance, issues have been identified with the overall road maintenance regime. A number of steps, including a full review and re-tendering the road maintenance contracts, and full cleans and asset data capture of the mud tanks in South Dunedin have been taken to address these.
  7. In 2010, Council published its 3 Waters Strategy (the Strategy), which identified that stormwater flooding was a risk in some areas of the city and likely to get worse or more frequent with predicted weather pattern changes. The strategy also noted that unless appropriately managed, demographic changes and ageing infrastructure would exacerbate the situation.
  8. The strategy outlines the key technical issues, challenges and community priorities for the effective and sustainable management of Dunedin’s water infrastructure. One of the main priorities is to ensure that key service levels are maintained into the future, based on the premise that there will be no increase in the number of residential or commercial properties at risk of sewer flooding. This means that the existing levels of service across the city will be maintained.


Climate change and South Dunedin flooding

Major flooding in South Dunedin last year is sometimes cited as a sign of future problems with climate change, but it isn’t a simple issue.

Last week the Commissioner for the Environment spoke in Dunedin, reported by the ODT in South Dunedin flood risk ‘an issue’:

‘‘The most troubling example of this in New Zealand, at least in the short term, is South Dunedin,” she said.

‘‘As the sea rises, that groundwater will rise higher and higher over time.”

Last June’s flood was an example of what was to come.

‘‘This flooding from underneath will become more and more of an issue.”

However, the warming of the oceans presented the greatest risk of flooding.

Much of South Dunedin is less than a metre above sea level. It is drained and reclaimed swamp (originally turned into market gardens by Chinese settlers). So obviously a potential rise in sea levels is a concern.

Last year’s floods occurred after the second worst rainfall since records began in 1918. It’s impossible to say if this event was a symptom of climate change or not.

But the causes of flooding were varied and some at least were due to local human effects and poor maintenance of drainage infrastructure. A just released report highlights some of these problems.

ODT: Mud-tank maintenance failure

A long-awaited report into last June’s flood has found 75% of mud tanks in South Dunedin were not properly maintained.

A Fulton Hogan spokeswoman said in a statement last night it was confident it fulfilled the requirements of the contract.‘‘Due to the age and historic nature of the stormwater network, including the mud tanks, effective maintenance is a challenge.”

The failure of drainage infrastructure has been talked about for a while.


The report also raised longer-term issues about the state of South Dunedin’s infrastructure and said further work would be done to find out what investment was needed.

It found changes in South Dunedin meant the stormwater network, much of which was installed in the 1950s and 1960s, did not perform as well as intended when built.

This included the expansion of hard surfaces, which had increased the amount of rainfall that needed to be dealt with by the stormwater system from 45% to 60%.


In a separate issue, it found the screen on the Portobello Rd pump station was unable to be cleared of debris due to the severity of the flood, an issue that would be fixed when modifications were made this year.

So whether the rainfall was a hundred year type weather event or a symptom of climate change there are a number of other factors involved.