The Parliamentary Commissioner for the Environment (PCE) has hired Crown research institute NIWA to draw up coastal hazard lines.

Yet the 2012 hazard line guidance co-authored by NIWA staff fails to define, even in principle, what likelihood such lines are meant to represent, let alone justify that choice in cost-benefit terms.

The folly of coastal hazard lines of unknown likelihood and net benefit is illustrated by the experience in 2012-14 of the Kapiti Coast District Council.

A 2012 coastal scientist’s report, commissioned by the Kapiti council, drew lines on a map that it described as predicted shorelines, 50 and 100 years hence.

On examination, they were not predictions at all. They were actually unreliable, speculative “what if” projections. For example, they simply assumed zero future accretion for a long-accreting shoreline.

Unfortunately, the Kapiti council was taken in. It immediately wrote to affected ratepayers, myself included, incorrectly representing these coastal hazard lines as the “likely” position of the future shoreline.

The same letter advised that the land information memorandums attached to their properties would be annotated accordingly forthwith. All this without consultation.

Affected property owners were not amused. After all, they have the strongest incentive to accurately assess and manage the risks to their own properties. They formed an association – Coastal Ratepayers United – to get those irresponsibly-misleading annotations removed. I am an active member.

The Kapiti council quickly discovered its error. Belatedly, the report’s author acknowledged the “predicted” shorelines were not showing likely positions after all; instead they were “conservative” “estimates.“ The Kapiti council must have been unamused.

Well, how conservative and in which direction? Even the report’s author did not seem to have an answer to the first question. But the direction became apparent when the favoured official description of what the lines represented became “worse case” or “worst case.”

The obvious questions – “worse than what and by how much?” – were apparently unanswerable. Nor did there seem to be any basis for representing them as “worst case.”

In short, no one was able to interpret those hazard lines in probabilistic terms, not even their author.

This arguably violated policy 24, a provision in central government’s National Coastal Policy Statement 2010 that requires high risk areas to be identified. High risk does not mean extremely remote risk.

Lines in the sand that no one can interpret are next to useless for decision-making purposes.

It is also bizarre to use the word “conservative” to describe speculative projections that postulate a radical change from the observed statistical trend.

The resulting prolonged divisive shambles was costly for everybody. We now have a new mayor and deputy mayor, a suspended district plan and the removal of the said annotations.

However, a replay of much of the above could easily occur. Witness the Parliamentary Commissioner’s hiring of NIWA to draw up coastal hazard lines for the whole country.

Coastal scientists and central government guidelines fail the community when they refuse to address the question of likelihoods in a mainstream statistical manner.

Suppose someone offered to toss a coin for you; heads you win a dollar, tails you lose a dollar.

In this case, if you are risk averse you refuse to take the gamble. If you are risk neutral you don’t care either way. If you are a risk lover, you agree to the coin toss. (All by definition.)

Ask a statistician

But what if you do not trust the coin? Perhaps it is biased against you? Well, you could ask a statistician to assess the degree of bias, if any. Statisticians can do this. Thus informed, you can readily decide what to do.

Note that the decision remains yours alone.

In general, our preferred response to uncertain outcomes rests on: (1) the probability of each and every outcome; (2) the scale of the consequences (benefits or costs) in each case given our options; and (3) our personal attitude to risk.

The statistician can help us with (1) but not with (2) or (3).

The issue of how to respond to uncertainty about the future coastal shoreline is much the same.

Where a concern arises, the first logical step is to consult coastal science experts with the requisite statistical expertise. Property owners want a robust assessment of the probability distribution for future shoreline outcomes. The natural starting point is the probability distribution that best fits the historical record.

If the said coastal scientists provided the required probabilities, property owners, including the Kapiti council, might next consult valuers, engineers, insurers and contractors to help assess the costs and benefits of the options that present themselves. Risk preferences only enter at step (3). Some property owners may decide to sell their properties to others for whom the risks are acceptable.

Scientists with expertise?

We would not expect coastal scientists, NIWA or the Parliamentary Commissioner to help us with steps (2) or (3) for obvious reasons. So why does the Parliamentary Commissioner think NIWA is competent to produce meaningful coastal hazard lines?

In my view the answer is in good part because NIWA and the Ministry for the Environment are not explaining these matters adequately, perhaps even to themselves.

Far from telling readers that knowledge of the full probability distribution for natural hazard events is required for risk analysis, the ministry’s July 2008 guidance manual recommends (at P20) the use of specific values of unspecified statistical likelihood for future sea-level rise. Its guidance concerning risk preferences is non-existent. Confusion at the centre spreads from the centre. Kapiti council is, in part, a victim.

Decision-makers need coastal scientists with the request statistical expertise to focus on assessing the full probability distribution for future shoreline locations, taking into account consistency with the observational record, and ignoring risk. (Of course, the effort they put into assessing that probability distribution should be influenced by their client’s assessment of the value of that effort.)

Communities will continue to pay for formally useless reports from coastal hazard experts for as long as the farce continues of asking such experts to produce hazard lines that are statistically and economically meaningless.

Unfortunately, foolish risk regulation is not confined to coastal hazards, as some readers can no doubt attest.