Human beings have an extraordinary ability to act like lemmings.
Even when the danger is obvious we sometimes continue with a course of action that leads to disaster.
Many would argue that that is what is happening with climate change.
Despite the evidence of a significant chance of catastrophe, people and governments are unwilling and unable to do anything like enough to halt changes before they spiral out of control.
This is understandable to some degree because of the complexity of the issues, because probable calamity, if it actually happens, will take decades to unfold and because of the difficulties in finding feasible solutions.
Action within nations is hard enough let alone across many countries with their many different interests.
Less intelligible, though, is the lack of effective responses at local levels to obvious local problems, such as the continued construction of private houses on flood-prone parts of the Taieri Plain.
It was at this time of year in 2006 - April 25 - that sudden downpours in the upper Silver Stream catchment caused it to rapidly become a mountain torrent thundering on to the Taieri Plain.
The stream burst its left bank and flooded homes and drowned animals. From the Otago Regional Council's point of view, the overall flood scheme worked well and Mosgiel itself was spared.
The trouble was that an area that had been pasture was now "lifestyle blocks" and was flooded, resulting in much anguish and much damage.
Subsequently, residents in the Mill Creek subdivision area said the Dunedin City Council, which allowed homes to be built there, and the regional council, which has responsibility for rivers, should protect their homes.
Subsequently, too, despite no additional protection, houses continue to be built on this and other vulnerable parts of the Taieri. As Cr Stephen Woodhead said last week at a regional council meeting, allowing people to continue to build homes with the floor level to the ground on "a known flood plain" was "craziness".
In some places, as a council officer said, the risks were so high it did not matter how high the floor level was.
The problems are obvious and the issues have been talked about over the past four years, but building continues.
The regional council says it lacks the power to ban construction in such places.
The building code and the city council's building consent rules only require living areas to withstand a one-in-50 year flood, but this proved hopelessly inadequate for the 1996 deluge (a "one-in-148 year flood"), and they are sure to be insufficient again.
Exacerbating matters is the fact that the spread of houses is increasing run-off, so the risks calculated for farmland inundation, as well as the inexact nature of flood estimation itself, are out of kilter with reality.
What is needed, the regional council insists, is for the city council to front up and deal with planning issues so that house building on flood-prone areas can be controlled.
At the same time, the regional council is to investigate the option of initiating a change to the city's district plan to try to prevent matters getting worse.
The frustration of the regional councillors last week was palpable. It has taken four years - far too long - to prepare a report on the flood risk for the lower Silver Stream, and in the meantime houses have continued to be built.
The traditional containment solution, building floodbanks, will prove far too expensive and, anyway, that often just diverts the floodwater somewhere else.
Flooding on the Taieri is complex and interrelated and more floodbanks could require Taieri people to be, as Cr David Shepherd put it, "rated off the face of the Earth".
How is it, then, that in the 2000s building continues to be permitted in risky, flood-prone places?
Is it the irresponsibility of developers and subdividers?
Are the section and house purchasers imprudent and should they take much more personal responsibility?
Should the city council district plan or its building codes be stricter?
Has inertia at the regional council delayed the further highlighting of this issue?
To be fair, the two councils in 2006, in a joint media briefing, did urge property owners in the Mill Creek subdivision to build higher, at least 20cm above the height of the April 25-26 flood.
But it is most disappointing that no-one has been able to prevent subsequent building on the Taieri Plain's high-risk areas.
