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Why do we manage flooding so poorly?

By Chas Keys - posted Thursday, 10 January 2013


The folly of governments' thinking on the matter of urban development on floodplains can be demonstrated in many areas, but two cases will make the point. In Brisbane, the great flood of 1974 saw the Bjelke-Petersen government build Wivenhoe Dam partly for the purpose of flood mitigation. The mitigation benefits were loudly trumpeted and their limitations ignored, and the impression was given that the dam would solve the problem of flooding from the Brisbane River. Further development on the floodplain within the city was greatly encouraged. The 2011 flood peaked at a lower level in Brisbane than the 1974 event had done, partly because of the increased flood storage available, yet many more dwellings and other buildings took in water. The mitigation benefits of the dam were more than countered by the increased development of the floodplain.

The other example is Maitland, in the Hunter Valley. Eleven people died there in the 1955 flood and more than a hundred houses were swept away or had to be demolished later. The state government reacted by banning residential redevelopment in and around the town's Central Business District and creating a system of levees and floodway bypasses. Many home-owners, tired of repeated flooding and alarmed by the severity of the 1955 event, trucked their houses to high ground nearby, and the processes of out-migration, demographic aging and commercial expansion saw the population of central Maitland drop to a third of its pre-1955 level by 2011. Unsurprisingly, the CBD began to suffer.

The council's response to the CBD's woes was to convince the state government to drop its decades-old opposition to residential redevelopment on the floodplain. Now, Maitland has the explicit goal of housing as many people in the area as lived there before 1955. Yet the levees are designed to keep out only floods up to the level of the 5% Annual Exceedence Probability flood â"€ the so-called once-in -20-years (on average) event. A case can be made that the intended development will restore the community's pre-1955 level of flood vulnerability. Infrastructure that will inevitably be damaged or destroyed will have to be replaced, repeatedly, and many more people will be put at risk even though the floors of their dwellings will be above the level of the estimated 1% flood. The problem of the faltering CBD will be addressed by creating an even greater problem, that is, by placing more lives and assets at risk.

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There is an underlying pattern here. State and local governments are determined to achieve 'development', despite the risks that are involved, so questions about the location of that development are either not posed or are carefully circumvented in planning processes. The threat posed by flooding is deliberately minimised and the improvements in flood management that have occurred are emphasised and sometimes exaggerated. Departments of planning, both state and council, have become departments of development supporting the needs of the development industry. Protecting lives and property has become secondary.

Society regularly debates the merits of development versus environmental preservation, but rarely the impacts of development on public safety and the protection of assets. Between floods we (like our political and bureaucratic masters) become convinced that the risks of flooding are overstated, and we agonise about the problem only when flooding strikes again. Then we lose interest once more. Yet those whose dwellings or businesses are flooded can find the experience ruinous as well as distressing.

Brisbane and Maitland exemplify what is known as 'the levee paradox' in which a community, tired of flooding, pressures government for protection. When the protection is provided (for example in the form of levees, mitigation dams or other works), there is pressure to further develop the land in the protected areas. Then a flood occurs that exceeds the capacity of the mitigation devices, and the costs to the community are greater than they would otherwise have been because of the additional or intensified development. This is precisely what happened in Brisbane between 1974 and 2011, and precisely what will happen in Maitland when the levees are overtopped as they are designed to be in a flood much smaller than 1955's.

We have allowed the problem of flood vulnerability to grow - slowly but inexorably. The legacy of decades of ill-advised development has increased to the point that it is economically impossible to remove residential and other development from all but the most severely flood-prone locations. Yet we keep increasing the size of the problem in the usually lengthy periods that elapse between episodes of significant flooding in particular locations, only to be surprised when the inevitable occurs and the costs imposed are shown to have increased greatly. We also condemn ourselves to funding expensive recovery programmes which have to be mounted repeatedly (sometimes with special levies being needed) as well as to increased home and business insurance premiums. Costs are piled upon costs, and one way or another we all pay.

Yet there is no need to develop floodplains in ways that will guarantee more economic loss and put more lives at risk. Both in and around most of our towns and cities substantial tracts of land are available beyond flood reach. But we cannot grasp the in-built contradictions and inefficiencies of our approach to development.

Between individual complacency with regard to floodwaters and wilful governmental blindness in the utilisation of floodplains, we cause ourselves much pain. The pain is deserved, because it is self-imposed. We lack the will to deal sensibly with the risks of flooding.

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We could do better. We could follow Queensland's lead and prosecute people for reckless behaviour in floodwaters, or make those whose recklessness requires them to be rescued pay the costs. We could also act decisively on flood warnings to protect our belongings, and evacuate promptly when necessary. And we could insist that governments and councils make sensibly conservative, long-sighted decisions on the use of floodplain land.

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About the Author

Chas Keys is a flood consultant, an Honorary Associate of Risk Frontiers at Macquarie University and a former Deputy Director-General of the NSW State Emergency Service.

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