Feature

Nature-Born Killers

Natural disasters can strike anywhere in New Zealand -- are we ready?

Ian Collins

Given New Zealand's geography and history, it's not surprising that the country is often referred to as the "Shaky Isles". What is surprising is that New Zealand's approach to natural disaster prediction and prevention is not as sophisticated as many citizens might imagine.

"The fact is that we're not very well prepared at all," says Lincoln University Reader in Natural Resources Engineering Dr Tim Davies.

With a research interest in natural hazards and disaster prevention, Davies has plenty of material near at hand for his work and a well documented catalogue of national calamities illustrating the frequency with which New Zealand has been "caught out" by nature.

The river of volcanic mud triggering the Tangiwai rail disaster of 1953...New Zealand's worst ever storm which sank the Wahine in 1968...Cyclone Bola wreaking economic devastation on the North Island's East Coast in 1988...they're all examples of nature's untamed fury.

Figurative language aside, what do we actually mean by the term "natural hazard"?

Davies says the question really starts with the way we look at "natural resources". His working definition for these is "bits of nature that are potentially useful to people".

"From there it is not too difficult to see that sometimes these bits of nature' are going to occur inconveniently -- the wrong place at the wrong time sort of thing.

"A simple example is the abundance of water in Westland -- more than is needed locally -- and the frequent lack of it in Canterbury when farmers need it.

"If a resource behaves very inconveniently it becomes a hazard' and that leads to a definition of a natural hazard as a bit of nature that is potentially damaging to people'.

"As you can see, every resource can become a hazard. But here's the important aspect -- it is the presence and behaviour of people that defines natural hazards or hazardous situations. If there are no people around to be killed, injured or inconvenienced then nature can take its course innocently.

"This is a vital point because the most practicable option for dealing with potential hazards is often to change the behaviour of people so that the hazard no longer exists.

"For example, instead of building control banks to try to prevent a recurrence of the 1975 flash flood catastrophe at Blandswood, Peel Forest, in which four children died, an alternative option is to relocate the dozen or so holiday homes at risk to a safe site nearby.

"A more extreme example, but obviously socially and politically impossible, would be to relocate the city of Christchurch instead of raising the stopbanks of the Waimakariri River. Absurd as that sounds, in the long term it might well make economic sense!"

In essence Davies is saying that with potential disasters we have two options -- controlling the hazard or getting out of the way. Given that the former is usually very difficult and, over the long term, often impossible, we're left with getting out of the way as the better choice, but that, he says, needs careful planning and it may involve major social and economic dislocation.

"New Zealand is a resource rich country -- we are wonderfully well endowed with natural resources such as soils, rivers, lakes, groundwater, mountains, plains, valleys, wind, rain, snow, ice, sun, fresh air, flora and fauna -- but as I have said, these resources can often occur inconveniently and they have the potential to cause human damage and distress. At that point they become hazards.

Mountain Hazards

"Take mountains, for example. Despite all sorts of human effort there is no indication that scientific knowledge and technological capability have succeeded in reducing the toll of mountain-related disasters.

"On the contrary, the increasing use of mountains as resources for energy generation, industry, transport, and recreation actually raises the potential for havoc.

"Natural processes affect more and more people as hazard-susceptible lands are occupied and additional processes occur as mountains are modified by dams, bridges, roads, ski areas and deforestation.

"Think about what happened this year at Ohakune, Chateau Tongariro and the Whakapapa and Turoa ski fields when Mount Ruapehu erupted -- social and economic disruption on a large scale. Not to mention the ash hazard grounding airline flights over most of the North Island and damaging pastures on farmland.

"Despite increasingly sophisticated technology, the devastation caused by mountain hazards is not being significantly reduced by present approaches to disaster prediction or prevention. Indeed, efforts to modify natural events actually encourage people to invest in hazard-prone areas, and when the modification attempt fails the result is worse than it would be without the attempt."

Davies says the existing system of predicting the likelihood of a disaster occurring through the use of "event" statistics and then applying a cost-benefit analysis, is not satisfactory because a design life of, say, 100 years takes into account only a very small sample of major events and the past record is inadequate to describe the full tally of events over all time. Also, he says, cost-benefit analyses are liable to major imprecision.

"What we need to do is base disaster prevention strategies on a realistic assessment of our knowledge of past and future events.

"Although large events -- like volcanic eruptions of the size that created Lake Taupo -- are very infrequent they can occur at any time and when one does it will be devastating. A strategy combining restricted land use in the potentially hazardous area plus the provision of warning and evacuation procedures would therefore seem to be sensible.

"Also, an approximate magnitude-frequency relationship for much smaller events can be established if adequate records are available.

"Smaller events can be controlled by structural means designed on the basis of these statistics without the need for warning and evacuation procedures."

According to Davies the broad picture is this -- reducing natural hazards can only be reliably accomplished by changing human behaviour. You can't win by trying to alter the natural behaviour of a natural system that is hazardous -- it's too difficult.

"Changing natural systems by the use of technology (eg. stopbanks on a river or erosion control structures on a hillside) works for a limited time only," he says. One day an event will occur which will exceed the capability of the technology to cope.

"When, not if, that big one' happens, the damage will be very great indeed because the event will restore the long-term average natural behaviour and will thus be much more intense than the equivalent event would have been in the absence of the inhibiting technology. However, more significantly, while the technology was being effective people will have become used to the absence of the hazard and started behaving in ways that make them much more vulnerable to the hazard when it does occur."

Don't blame the engineers for disasters when they occur -- that's the message from Davies, who says it is impossible to know the future in sufficient detail to plan confidently for the control of natural processes that lead to hazards.

"This is rather depressing for those who wish to use science and technology to build a wonderful future for mankind," he says, "but such an expectation is the inevitable result of a simple view of the way nature behaves in contrast to a realistic appreciation of the limits of science in predicting its behaviour."

"We must continue to use resources and live with hazards. But we must maintain a realistic view of what we can know about the future, what we can do to modify natural systems, and how accurate our predictions are about the response of systems to modification," says Davies.

"Because the behaviour of natural systems is non-linear and therefore unpredictable, we must base our future management of hazards on experience rather than theory, and on altering human behaviour instead of trying to change natural systems."

Davies says that perhaps the relevant phrase of the Resource Management Act should be re-written to read: "...to carefully select the present and future needs of people and communities so that they are able to be met by the use, development and conservation of natural systems".

Ian Collins is a Lincoln University journalist.