The political problem of defining “flood prone”

Apr 29, 2021
Flood water feature
Credit - Unsplash

The words ‘flood’ and prone’ are simple enough to comprehend, but when they are put next to each other in a sentence they can quickly become problematic.

“This block of land is flood prone,” or, even worse, “This block is not flood prone” easily become statements that are contentious, the latter especially if it is proved wrong. The problem, of course, lies in the politics of using the words.

The literal meaning of the term ‘flood prone’ is not difficult to fathom. All land is prone to flooding if rainfall is intense enough to overwhelm the ability of drainage lines, whether natural or artificial, to hold the water and it surcharges onto ground that is usually dry. Even land on hills can experience flooding, therefore. But most flooding occurs on floodplains when runoff is too great to contain within stream banks. Defining just which areas can be affected does pose some difficulty, however.

Hydrologists usually define land that is prone to flooding as land that will be inundated in the biggest possible flood event, the so-called Probable Maximum Flood (PMF). Any other definition, for example, one based on a flood of a particular average return period such as the so-called 100-year flood, must exclude land which will be inundated in some events. A PMF is an enormous flood, well beyond individual experience, and might occur when, a week after a huge flood has left the ground saturated, a flood of even more gigantic proportions is generated by a rain event of an extreme nature. The height that a PMF will reach at a specified location can be estimated given knowledge of potential rainfall intensity (assessed from past extreme events in similar climatic zones) occurring on already saturated land. Assessed PMFs are approximations, and they may change as analytical techniques evolve, or indeed with climate change over long periods of time.

None of this is particularly complex, at least conceptually. But add the human dimension to the language and things change. Real estate agents are frequently said to minimise the flood problem of a block of land or a dwelling they are trying to sell: calling it ‘flood prone’, after all, is likely to reduce its attractiveness, discourage a desired sale and/or reduce the price a property will fetch. So agents, not armed with or necessarily interested in flood histories or hydrological studies, will sometimes be heard to say that a block has not been flooded in 10, 20 or more years or even “ever”. Potential buyers welcome this assurance. Generally they do not consider the risk of flooding (or indeed bushfire or earthquake) that might apply only rarely, and they are not motivated when seeking to buy a property to think about extreme events in nature.

Yet when people are affected by floods they feel let down and say: “We weren’t told our place was flood prone.” Council notifications, indeed, frequently fail to make a property’s flood risk clear, and the rules governing disclosure vary considerably across Australia. So does the level of knowledge that councils have about flood risk within their jurisdictions: not all flood liable areas have been subjected to detailed flood analysis from which risk can be established accurately and with clarity.

Moreover, not all buyers can tell whether a property is on a floodplain, the more so after the floodplain has been built upon and signs of the natural environment (including views of watercourses) obliterated or obscured. And people living behind levees, constructed for the explicit purpose of keeping floods out, prefer not to think of themselves as living in a flood liable location. Yet levees are not infrequently overtopped or breached, with serious consequences. Mentioning this to residents in such areas can hit a nerve and even produce an angry response.

Some real estate agents go close to denying the risk of flooding, or at least severe flood events. One, a local government councillor in western Sydney years ago, was in the habit of referring in council forums to the great Hawkesbury River flood of 1867 as the “alleged” 1867 flood. Self-evidently that event preceded living memory, but it was real, has been much studied and is well understood. We know that a repeat under today’s circumstances, with tens of thousands of people living in the valley and with dwelling floors well below the level reached in 1867, would wreak havoc. The damage bill would be colossal, as the death toll might be. Psychologically and politically the 1867 flood retains power in the Hawkesbury and the wish of some to cast doubt upon its veracity is understandable.

Yet one day a generation of Hawkesbury residents will have to confront such a flood (or an even bigger one). This should be seen as inevitable even though we cannot tell when it will occur.

The insurance industry also bears some responsibility for the problems that exist in relation to people’s understanding of flooding. For decades in Australia it was the norm for distinctions to be made by insurance companies between ‘flood’ and ‘storm’. The convention was widely adopted that water affecting a property was defined as the result of storm activity if it flowed overland towards a watercourse and caused damage on the way. Impacts thus created were covered by standard insurance policies. But water exceeding the bounds of a stream and thus escaping from its ‘normal’ confines was by contrast defined as being floodwater and the resulting damage was generally not covered. Flood and storm were words whose definitions were in effect controlled by business interests and used to their advantage.

The distinction caused much angst, and people obviously preferred to have their cases defined as having been the result of storms, not floods. Councils and news media sympathised with them, and it was common to hear the refrain that damage was storm-generated, not created by flooding. The technicalities of insurance decision making, using trained hydrologists whose rationales were not easily explained to people lacking the necessary specialist training, became politically problematic, and campaigns sought to force insurance companies to change their definitions and the nature of their coverage. During the first decade of the current century, things began to change.

The old distinction is now less commonly used, and an impediment to the provision of insurance cover has been partly removed. But making flood cover available does not solve the problem given that companies must price the risk in such a way that payouts can be made: to do otherwise is to risk bankruptcy which is in nobody’s interests or indeed in society’s. Premiums for the most highly flood prone residential properties are thus high, with instances of more than $20,000 being reported when the flood risk is incorporated alongside other risks in general household premiums. There are still many dwellings located in highly flood prone areas, and therefore many people who are faced with premiums they cannot afford. They live with a real risk of being ruined financially by floods.

The problem is vexed and highly political. In practice it is getting worse because floodplains in western Sydney and elsewhere are still being converted into suburbs, rapidly and at scale. The chance of governments buying out very substantial numbers of people from the effects of mistakes to which government land development policies have contributed is nil: the problem has become far too large, and the sterilisation of whole floodplains will not be contemplated. The best that can be hoped for, short of cataclysmic flooding which forces a radical change in thinking about government as an insurer of last resort, is a reduction in the rate at which the number of flood prone residential and other properties increases. Given the vested interests involved, it is hard to see this happening.

And all this is without even considering the question of climate change, which is likely to exacerbate the problem yet further. Flood proneness will always be with us and we continue to make it worse. Our use of language has often confused and politicised the issue, which never helps.

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