Flood warning: upgrade gauging networks, focus on warning messages

May 18, 2023
Drone aerial photograph of severe flooding of the Nepean River and flood plain in Penrith in New South Wales in Australia.

Last Monday, Minister for the Environment Tanya Plibersek and Minister for Emergency Management Murray Watt announced an intended spending of $236 million to upgrade the nation’s flood warning gauge networks. This is welcome news, but it must also be recognised that for flood warning to be truly effective we will need to pay more attention to what is done with the information the gauges provide.

In particular we must focus more on how warnings are communicated to those in the path of floods, ensuring that people understand what is coming and how they should respond and, crucially, are motivated to carry out actions which will save items of property and keep them safe.

Warning a community that is about to experience flooding is a complex business involving a chain of processes. Firstly, it requires the gathering of information on the likely impacts of recorded and potential rainfall on stream levels upstream of the community at risk. Then there must be a capacity to predict how high stream levels will get at a nominated gauge to which the community refers, and from that hydrological prediction there must be a capacity to work out what the impacts on members of the soon-to-be-affected community will be. Then, finally, the communication of those likely impacts must be undertaken in ways that community members will comprehend: they must be provided with advice on what they should do to minimise the risks they face.

In all this, data gathering is involved along with predictive modelling of likely flood heights and the communication of the expected flood heights and likely consequences to the flood-liable community via the media and the internet and, in some situations, by door knocking. Several agencies will be involved, including those owning stream gauges (the Bureau of Meteorology, state and local governments, universities, irrigation interests and others), those predicting flood heights (largely the Bureau, but with input from other gauge owners and local councils), and those responsible for the dissemination of flood warning information (typically the State and Territory Emergency Services and local governments) to at-risk communities. There is a need for slick and efficient transmission of information between agencies, usually within tight time frames before floodwaters arrive, and for the communication of information to the community which must be quick, comprehensible, persuasive and contain helpful advice on appropriate actions for people to take.

Those responsible for the processes involved will often need to focus on several communities along a river (or along multiple rivers affected by the same rain event), and they will need to be cognisant of the variegated makeup of the communities for which warning information is to be provided. Typically, communities will be both rural and urban, the farmers and townsfolk having different interests and needing to make different responses before the flood waters arrive. There is little that is simple here.

The gauges to which Plibersek and Watt were referring in their funding announcement are those situated in the early part of the chain of processes described above. These gauges transmit stream-level data to those whose task it is to predict how high the stream will reach over following hours and days. Having enough of these gauges, and having them work reliably, is critical to the integrity and accuracy of forecasting processes: hence the need for gauge maintenance and repair, especially after floods which will have damaged or destroyed some of them. Then there is the issue of the means by which gauge data is transmitted to those doing the predicting. It is still the case that some gauges must be manually read and data passed on in ‘slow time’ rather than using telemetry which provides instantaneous transmission. Conversion to telemetry is necessary but is a process that is taking time (indeed, time measured in some cases in decades) to complete.

Without doubt, we have under-invested in gauge networks in the past. Resources are always scarce and upgrades partial and incomplete.

Plibersek and Watt are correct to place an emphasis on the quality of gauging networks. Gaps in networks (such as little-gauged or ungauged sub-catchments) impede the Bureau’s ability to forecast how high a flood will reach at specified locations. They also impede the ability of those who will use the height forecasts to identify where the floodwater will go as it rises to the peak, who will be affected and in what ways. This is a critical matter in terms of identifying what people should do to lessen the consequences as far as their interests are concerned whether that is moving livestock out of harm’s way, lifting items in houses or business premises or evacuating in a timely and safe manner to higher ground. Sometimes, the scope of what is required of people who are at risk is daunting, and the same can be true of the scale of evacuations which must be managed by State/Territory Emergency Services, the Police and other authorities.

During the early 1990s, after severe flooding in Queensland, New South Wales and Victoria which saw the virtually complete evacuation of whole towns including Charleville and Nyngan, an agreement was reached by the multi-agency, multi-faceted Australian flood warning community to produce a best-practice manual on flood warning for Australian usage. This, it was clear, was necessary to guide agency responses in a complex field of endeavour. The manual was produced in 1995 and updated in 1998 and 2009.

All three versions noted that the greatest deficiencies in prevailing practice were not in the quality of the gauging networks or the prediction of flood heights, notwithstanding gaps and imperfections in both these areas, but in the communication of estimates of impact to at-risk communities. This remains the case today and is demonstrated in virtually every significant flood.

There are substantial differences between states and regions in Australia in the sophistication of flood warning practice. Not all flood-prone areas have developed high-quality banks of ‘flood intelligence’ from which the impacts of floods reaching different heights can be estimated, and not all involved agencies have invested equally or sufficiently in the resources needed to incorporate the estimates in warning messages that go out as floods are approaching. Not everybody with a role in flood warning dissemination has been involved in developing warning messages outside flood time for fine-tuning when flooding is imminent: practising the role and ensuring that messages are properly devised, compelling and convincing has thus not been achieved to equal effect in all jurisdictions. Unsurprisingly, the warnings that are disseminated all too frequently fail to produce the intended results in terms of the responses of community members.

There is ample evidence that many people in flood-liable areas have no clear understanding of what floods can mean for them, especially the bigger floods which are of scales that occur only infrequently. Many floods provide evidence of the truth of this statement, people reacting too little and too late because they did not realise what a coming flood would mean and were not informed optimally by flood warning messages about the importance of doing what was necessary to protect their interests and lives.  Frequently, people claim that they were not warned ꟷ though the more common problem is that they did not hear or failed to comprehend the messages that were sent. Sometimes, it is clear that people simply do not recognise warning messages for what they are or do not believe that the information contained in them is relevant to their own situations.

The result is that people often under-react or fail to act at all as a flood is approaching and they are caught short when it arrives. In some environments, the potential for mass deaths because of under-response the Hawkesbury, on Sydney’s north-western edge and the Gold Coast in southern Queensland, for example, is considerable. In extreme floods (such as Lismore’s early last year) in these areas there will be genuine risk to the lives of thousands of people, something that is not clearly understood in the communities themselves. Indeed the risk to the many flood-prone communities on our rivers and creeks, in all states and territories, is significant and inadequately recognised by those who at some stage are likely to be placed in harm’s way by floods.

There is a need here for sophisticated, targeted education programmes to be developed about the flood threats people may face, the flood responses they might need to undertake and the flood warning systems which are intended to help them.  The existence, operation, meaning and potential usefulness of flood warning systems must be explained. As with anti-smoking, defensive driving, safe-sex and sports anti-gambling campaigns, such education will be expensive, especially since it must be ongoing. In Australia we have invested relatively little in such education as far as flooding is concerned: we have tended, instead, to focus on structural flood mitigation devices such as levees and flood detention basins. Probably a massive flood disaster, involving a very large death toll, will be needed to trigger the sort of investment in warning communication alluded to here.

Flood discussions in Australia since the several severe floods of 2021 and 2022 have focused on relief measures, buy-backs and land swaps. Land use development policy, specifically with reference to the development of new housing estates on floodplains, has yet to produce significant change to past practice despite the recognition at the time of these floods that much current development practice is flawed and continues to place people at risk. Now, substantial investment in gauging networks is being undertaken, and the building of further protective levees is under consideration.

These are all important elements of our flood management activity, which requires approaches from several different angles. Ensuring that flood warning works to the benefit of people at risk of floods is also vital, yet it remains less than adequately resourced especially in the context of the way communication is undertaken as floods approach. This is a facet of our flood management toolkit that remains very much in need of improved development.

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