What's the risk of a natural disaster in New Zealand and around the world?

Thursday, 22 December 2016

Cyclone Pam devastated Vanuatu in March 2015.

New Zealand is precariously situated, jutting skyward between two colossal tectonic plates, slap bang in the middle of a deep ocean, and vulnerable to tsunami, earthquakes, storms, floods, and volcanic activity. A deadly natural disaster is possible. So what's the risk?

Hundreds of deadly natural disasters occur around the world each year.

In individual terms these are infrequent events, generations apart.

So, what are the chances of being caught in one in New Zealand?

Broadly, on a worldwide playing field, there is an extremely low likelihood of being killed by a natural disaster.

**READ MORE:

* Wellington's quake woes nothing new

* The murky science of quake engineering**

A ship swept up by the tsunami in Kamaishi City in Iwate Prefecture, Japan, March 2011.

That risk profile changes depending where you live.

If you live in a high-risk zone your chances are higher, but you are also much more likely to die from natural causes, disease, or injury, than in a natural disaster.

If you're a New Zealander under 35, suffering a physical illness (as opposed to an illness) is the leading cause of death.

Obviously for older Kiwis, illness and old age is the leading cause.

The risk from an earthquake or a similar natural disaster is less than the risk posed by boarding a commercial aircraft and much less than the risk of a road traffic crash.

115 people died when the Canterbury Television building collapsed in the February 2011 earthquake.

That said, a natural disaster could kill thousands of New Zealanders. Last year, a worst-case report said a large-scale tsunami could kill 33,000 people and the responses required for the country's tsunami risk were poorly understood.

GNS Science general manager of natural hazards strategic relationships Kelvin Berryman said large, deadly events were rare.

A selection of natural hazard deaths including estimates in New Zealand 1858-2011.

Public awareness was high after a disaster, he said.

'They are potentially catastrophic but a lot of things in New Zealand are mitigating that already.

NIWA scientist Dr Rob Bell was in Thailand soon after the Boxing Day tsunami to survey the damage and learn.

'We're dealing with 4.5 million individuals here. Trying to get the right message to all of them so that it resonates with all of them is a difficult task. The mortality rate with natural disasters is less than flying in a commercial aircraft, way less than deaths on New Zealand roads.

'Right now we're in a state of eagerness for people to understand earthquakes. They're not very often so it's really easy to lose perspective and consciousness falls away very quickly. It's a big challenge but not impossible.'

The remains of the Sofitel Hotel after the Boxing Day tsunami, Khao Lak, Thailand, 2004.

Berryman's tips: be prepared, make a plan, take action if necessary.

RISK

People walk past the rubble following a 7.3 magnitude earthquake on May 13, 2015 in Kathmandu, Nepal.

Risk, or probability, changes with time too.

So, a one-in-200-year quake could happen any year during a two century window, but on a longer timeline the probability increases. The probability of a one-in-200-year quake occurring in a 70-year period is one-in-three.

A tsunami warning sign south of Hanmer Springs.

GNS Science base the risk of an earthquake on the likelihood of damaging ground movement, so being close to the Alpine Fault or living in Canterbury or the Wellington-Wairarapa regions presents a greater risk.

In a report into risk assessment in Port Hills, Christchurch, GNS estimated the average natural hazard fatality risk to New Zealanders since 1870, by taking an average population and the historical fatality rates for each hazard type.

The overall hazard fatality risk faced by a New Zealander over this period was, on average, less than three in a million per year. In other words, about the same chance as winning the Lotto first division.

National Institute of Water and Atmospheric Research principal scientist Dr Rob Bell said assessing risk was difficult.

The most underrated modern day risk was a tsunami, he said. New Zealand is flanked by subduction zones, where a tectonic plate forces itself beneath another plate, and there was some evidence of ancient large-scale 'paleo-tsunami'.

Evidence also pointed to an increase in climate-related disasters, such as drought and heatwaves.

'I think tsunami is probably the most under-estimated disaster risk and it could turn up at any time.'

Even so, the odds of a deadly tsunami were low, he said.

'We're not talking about this in terms of Haiti or Bangladesh where the building stock is of a much lower quality.

'New Zealand is much more likely to experience damage to assets, roads, infrastructure. We have hazard warning systems. There's still the damage. That's kind of the mode we're in now, the effects of natural hazards. The same with the building codes, buildings stay up to save lives, but if a tsunami at 30kmh and five metres deep strikes not all of them are going to cope with that.

'The geohazards pose quite a sizeable risk. We've had a short history. We do have paleo evidence that suggests we've had some big events. We do have the pre-conditions, offshore zones like Banda Aceh or Japan.

'We are not short of hazard exposure. I wouldn't say the risk is low. We would be low with casualties, medium with casualties plus damage. That's what risk is: the damage and the effects on the economy and on people.'

TOLL

When large-scale quakes do occur, and if they occur in developing countries or concentrated poorly-built urban areas such as Haiti, the death tolls can be shocking, and difficult to comprehend.

The 2010 earthquake in Haiti killed an estimated 230,000 people (the official toll is disputed).

Broadly, most natural disasters are weather-related events - storms, floods, droughts, heatwaves - but around 40 per cent of the deaths caused by natural disasters are caused by earthquakes and tsunami.

There are other ways to measure loss too, such as the economic impact of an earthquake, demographic effects, and the psychological impact of quake stress and upheaval. The risk industry measures the likelihood of a natural disaster by combining vulnerability - the mix of people, location, and hazard type - with the potential for damage, in human terms and economics.

So, for example, someone living in Hamilton is not as exposed to risk as someone living in a tsunami zone below a cliff near a faultline.

Director of the Joint Centre for Disaster Research at Massey University Professor David Johnston said New Zealand still did not have a comprehensive natural disaster database. There was no one source for information on fatalities, injury rates, and types of disaster, he said.

More work was being done to consolidate this, he said.

One study suggested at least six people, possibly many more, had died in tsunami in New Zealand but, officially, the historical record attributes one death to tsunami.

Johnston said that without a national disaster database it was difficult to crunch the numbers.

'That's only what we have had, not what we could have.

'It's hard to get the numbers. People know there's a risk but there's no definitive source.

'History doesn't tell us the future very well. And if earthquakes continue we have more people in denser areas. Just dividing the number of years by the fatalities gives you a historically accurate number but it doesn't actually tell you about the risk.

'We haven't got a good handle on flood risks and flood deaths. In the 19th century they were very high. Nobody has ever pulled a fatality list together.

'We don't have a national disaster database.'

HISTORY

Victoria University psychology professor John McClure, whose research includes behaviour in natural disasters, said risk also involved a subjective component.

With a spate of fatal and destructive quakes in New Zealand over the past five years, earthquakes and natural hazards were uppermost in people's minds. Risk was a tricky concept, he said.

'Worldwide, earthquakes are a huge problem. In Haiti over 200,000 people were killed.

'In New Zealand, the United States and Japan we don't get those levels of fatalities. That's with building standards.

'A key aspect of these events is that they are low frequency events but can have a large magnitude effect. I think the big risk of these events is they are infrequent but when they do occur they have huge magnitudes.

'People should think: 'This may not happen in my lifetime but if it does it's worth being prepared sensibly.'

After the 2010 and 2011 Canterbury quakes, researchers discovered some Cantabrians were not prepared because they thought Wellington and the 'big one' was the biggest risk. And the Darfield fault was, up until then, unknown to geoscience.

In addition, some research suggests people who live in quake risk zones under-estimate the risk and believe they will fare better than others in the event of a disaster, but those who experience a disaster are much more likely to change their behaviour to adapt for future risk.

McClure said the longer the timeline then the more accurate the forecast - but the historical record can be incomplete. In terms of global preparedness, New Zealand was a leader and up there alongside Japan and Chile.

'You don't base perception of risk from recent data. In an earthquake a big city like in Haiti, it's like a nuclear bomb. In Japan their buildings are built so that after a big earthquake they are still usable. Buildings [here] are meant to not kill anybody but they can come down.

'There's a lot of thinking about earthquakes at the moment. In six months most people will have forgotten about it. It's worth capitalising on that window. Quakes are high on people's radar at the moment.

'We've had a series of recent earthquakes. If you get a really big one, an M8 or M9, and 40 buildings collapse it would be really devastating for the whole of New Zealand. Even though that's highly unlikely it could happen so it's worth taking precautions.'

The countries with the most deaths from natural disasters and the most frequent natural disasters are China, India, the United States, Indonesia, and the Philippines.

Since 2000, there have been three disasters in which more than 100,000 people were killed - the 2004 tsunami, the 2008 Myanmar cyclone and the 2010 Haiti quake.

Last year, according to the Centre of Research on the Epidemiology of Disasters, there were more than 300 natural disasters, causing 22,765 deaths and 110 million affected victims.