NSW awaits a momentous decision on housing development on floodplains

Jul 12, 2022
Windsor: Western Sydney flood 2022
Image: iStock

When it comes to the management of weather-related disasters like floods, governments can be relied upon to act in only two circumstances – catastrophe or repetition.

Lately, in New South Wales, we have had both – catastrophe at Lismore in February and March (in the shape of a flood whose peak level exceeded the previous highest recorded there by more than two metres), and repetition (in the Hawkesbury, which has seen three big and damaging floods in less than 18 months).

Will the state government act decisively on this occasion? And if it does, will its response be an appropriate one?

But first, back to the matter of catastrophe and repetition and governmental response. The Netherlands, one of the most flood-prone countries in the world, has had long experience with floods both from the North Sea and from the rivers which flow through the country from the south. Its flood-repelling dykes were big and famous, and they had over the centuries provided the country with a degree of security. But in 1953 the dykes designed to keep the North Sea out were breached – with horrendous consequences including more than 1800 people dead. (In neighbouring Belgium and across the sea in Essex, scores more died).

Flooding became defined as a threat to the viability of the Netherlands as a nation, even more than had previously been realised. The government reacted quickly and decisively, in effect deciding to spend much more heavily and in perpetuity to upgrade the flood defences and guard the country against future flooding. Modern science and engineering were invoked. Since 1953, the equivalent of hundreds of billions of Euros today have been invested in innovative flood mitigation defences against both the North Sea and the rivers.

The Netherlands has survived and prospered. The massive expenditure has not imperilled its ability to offer the living standards and services of a first-world country. Indeed it has enhanced that ability. The expenditure has been a sound investment.

Nobody would claim that NSW and the Netherlands are equivalents in terms of the severity of their flood problems. But there are parallels, and there is no doubt that flooding presents severe challenges to community sustainability and financial and emotional well-being in many parts of NSW.

Unlike the Dutch, who have wrestled with the flood problem for centuries and learned to live with it, NSW has largely let it build up stealthily through ill-advised approaches to development on floodplains. It is still doing that, and the valley of the Hawkesbury-Nepean River has as a result become an exemplar of inappropriate development. Housing development on a huge scale is still going on apace at Riverstone, Marsden Park and Marsden Park North, and one government report has forecast a virtual doubling of the population on the floodplains of the Hawkesbury-Nepean between 2020 and 2050.

Once in its history, NSW has acted decisively on floods. That was in the mid-1950s, after six years in which most parts of the state had experienced severe flooding. Some parts (like the Hunter Valley) had been hit repeatedly and disastrously. The response of the ALP government under JJ (Joe) Cahill was, first of all, to create the State Emergency Service as a volunteer-based, community-level flood agency dedicated to the real-time management of the effects of flooding. In effect its role was to guide community responses in times of flood.

The second policy reaction was for the government to involve itself in flood mitigation activity throughout the state. Previously, mitigation endeavours had been managed by councils, private citizens and local organisations like farmer-based ‘embankment committees’ which built and maintained levees. By the mid-1950s their efforts had been undertaken for nearly a century. They were well intentioned but haphazard: the levees were not built to sound engineering principles or standards, and they were regularly found out in big floods. Henceforth, government agencies (the Department of Public Works and the Water Conservation and Irrigation Commission) were given the responsibility for mitigation works – largely levees but also flood bypasses and detention basins and eventually extending to the introduction of house-raising and voluntary property buy-back schemes.

A third response, which evolved during the 1960s and 1970s, was an attempt to ‘discipline’ development – especially housing development on floodplains. Eventually, after many policy ‘tweaks’, NSW settled on the 1% Annual Exceedance Probability flood (the so-called 100-year flood) as the level below which residential floors would not be permitted. But this ignored the fact that, especially in the towns and suburbs on the rivers that flow to the Tasman Sea, floods can reach levels much higher than those defined by 1% AEP flood events.

The lower floodplains were more or less ‘sterilised’ from urban development, but not the middle and higher parts of them. Meanwhile, much ‘old’ housing development, dating from before the modern controls were instituted, remained vulnerable. These are the dwellings which on the Hawkesbury have been repeatedly inundated since early 2021. None of these floods has remotely approached 1% AEP levels.

What to do in Lismore, along the Hawkesbury and in many other parts of NSW? We can invest in further mitigation works, the past approach (and there is room for some of this) or we can focus on the root cause of the problem – past and continuing development on floodplains. The NSW Cabinet is divided on the matter, but both the Premier (Dominic Perrottet) and his party’s deputy leader (Stuart Ayres) favour a traditional mitigation measure for the Hawkesbury. It is the raising of Warragamba Dam to temporarily store floodwaters and thus reduce downstream peak levels in floods like those we have recently seen. In the Lismore case, some people advocate building several large dams upstream to contain floodwaters.

There will be substantial environmental costs, and damage to significant Aboriginal sites, from inundation above a raised Warragamba, and building several new dams above Lismore will be similarly problematic. But equally the impacts from floods on streams entering the main stem of the river below Warragamba (primarily the Nepean and Grose rivers and South and Eastern creeks) will remain ‘uncontrolled’ and in extreme floods like the one recently experienced at Lismore (and in the small towns below it on the Richmond River) the mitigative benefits as assessed by Infrastructure NSW will at best be slight.

Better, surely, to start focussing on the problem at its core – which is development on the floodplains. We could, and the Netherlands has done this at a considerable scale, buy back the developmental mistakes of the past and alter building regulations so as to reduce future development. To do either or both of these things will be extremely expensive, and the politics of making the regulations more ‘flood-defensive’ will be very difficult.

Buy-backs have been part of the arsenal of management strategies in NSW for decades, but they are poorly, perhaps even pathetically, funded. There are possibly 250,000-300,000 dwellings on floodplains in NSW, all of them by definition exposed to the flood risk. An unknown but large number of them have floors below 1% AEP flood levels, and it would be fanciful in the extreme to expect that they could all be bought out at public expense. But we could commit ourselves to buying out some, perhaps a few hundred in the most dangerously vulnerable locations, every year and resolving to keep doing it for decades to come. In some areas we could make it compulsory, in the public interest, in order to avoid repeated recovery expenditure.

There would be some unfortunate effects, for example on the commercial viability of established central business districts such as Lismore’s. But that would be preferable to the continued, repetitive and extremely expensive relief and recovery measures that we are currently forced to fund.

And then we could tighten the regulations governing future development, perhaps by raising the standard for residential floor levels to the 0.2% (so-called one in 500 years) or 0.1% (one in 1000 years) flood level on the east-flowing rivers. Better still, we could abandon the statistical measure entirely and focus on assessing the risk to the new owners of property from rare but nevertheless inevitable future big floods like Lismore’s of earlier this year (and Maitland’s in 1955 and Windsor’s in 1867).

In conjunction with buybacks and stronger restrictions on new housing, lowering the water storage level of Warragamba Dam to create ‘airspace’ for the storage of floods, and relying on water re-use, recycling and Sydney’s so far little-utilised desalination plant when drought strikes, would make vastly more sense than raising the dam.

We must start thinking big and long term, and recognise that huge floods will occur in the future. Almost certainly they will occur more frequently under the climate change that is now clearly embedded in what we face. Every town and suburb on a river will eventually experience a huge flood as Lismore did a few months ago. The potential savings on recovery spending, not to mention in pain and heartache, are considerable if we alter our thinking about development on floodplains.

The focus here is on the state government in the first instance. Will it do the traditional thing and invest in an expensive mitigation measure which cannot do more than palliate the problem at its edges, or will it emulate the government of the 1950s and commit to a new, admittedly costly approach but one with real promise eventually of taming the problem to a significant degree?

The signs at the moment are that with a decision near and many people along the Hawkesbury desperate for a solution  – any solution, however inadequate and short-sighted  – the state government will opt for the raising of the dam. Soon, the spotlight will shift to the federal government, because NSW will need Commonwealth funding for the project to proceed. In effect the Albanese administration will make the final decision.

In all this the NSW Flood Inquiry, presently being conducted under the Chair of the Independent Planning Commission of NSW (Mary O’Kane) and a former Police Commissioner (Mick Fuller), will be extremely important. The Inquiry will recommend by the end of July on how the government should proceed. Perrottet has staked his political future on dealing effectively with the flood problem of Lismore and he might be thinking of doing the same for the communities of the Hawkesbury. The Commission’s recommendations might steel his resolve – or not. We need recommendations that are bold and spark a bold, twenty-first century response from the state government. We do not need timidity or a solution redolent of those of the past.

Today NSW is where the Netherlands was in 1953 and the state was in 1955. Do we carry on as usual, sleepwalking towards the next big flood while nibbling at the edges of the problem, or do we take far-reaching action of a different sort to deal with the problem at the level of its root cause?

NSW is on the cusp of a truly momentous decision.

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