A battle to stop building housing in the highest risk locations on Australia’s floodplains appears to be finally gaining traction with a NSW Government decision to prevent some proposed development in the Hawkesbury-Nepean Valley west of Sydney. 

The Insurance Council of Australia (ICA) says it’s the first tangible decision by a State Government in response to a National Cabinet agreement last year that said “the days of developing on floodplains need to end”, establishing a landmark in an ongoing campaign. 

The NSW Government’s announced decision applies to thousands of proposed homes in the Riverstone Town Centre, Marsden Park North and West Schofields developments, and follows the release of a Flood Evacuation Modelling report for the Hawkesbury-Nepean Valley that makes clear the extent of the dangers. 

“This valley has the highest unmitigated flood risk exposure in Australia related to its unique landscape and large existing population,” the report says. 

The valley has highly interconnected flood-prone areas and the waters can be extensive and much deeper than most other floodplains in NSW and Australia, reflecting a “bathtub” effect created by unique geography. 

Most river valleys tend to widen as they approach the sea, but the opposite is the case in the Hawkesbury-Nepean and gorges create natural choke points.  

The Flood Evacuation Modelling report says the February flooding in Lismore last year, which was close to a 1 in 1000 chance per year event, was just over 2 metres higher than the 1 in 100 flood level. But a 1 in 1000 year flood in Windsor in the Hawksbury Nepean would be 3.3 metres above the 1 in 100 chance per year level. 

The dangers were highlighted by Insurance News in a magazine article in 2011 and the stakes have risen with the repeated devastating floods of the past few years, while housing pressures are also increasing. 

The flooding potential has long been known and was highlighted 200 years ago when NSW Governor Lachlan Macquarie in 1817 issued a third warning to settlers about the need to build on higher ground. The warning noted the recurrence of “awful visitations” and the “inevitable consequences” of placing stockyards and residences within the reach of floods. 

“Those who notwithstanding, shall perversely neglect the present admonition and exhortation to their own benefit, must be considered wilfully and obstinately blind to their true interests and undeserving of any future indulgences,” he wrote. 

Assistant Treasurer Stephen Jones after a recent trip to London and Munich with insurers has noted that reinsurers today are singing from a similar “stop doing dumb things” songbook. 

“When they see us taking steps to reduce the risks associated with severe weather events and climate change they mark us up, it makes a difference,” he told the ICA Annual Conference. 

“But when they see us make dumb decisions, which can compound poor planning decisions that have been made over the last 200 years, all of that work is undone.” 

The Flood Evacuation Modelling report says it’s considered unsafe to stay to defend homes, livelihoods or assets from major regional floods in the Hawkesbury-Nepean Valley and it’s best for people to evacuate before roads are cut off by floodwater. 

The more development, the harder it is to evacuate people and given road connections, growth in one area can have significant consequences on risk to life for existing populations across the floodplains. 

“To have allowed developments to proceed in these areas in full knowledge of the flood risk would have been unforgiveable,” ICA CEO Andrew Hall said. 

“It was never a question of whether these areas may flood; the science, data and modelling show we know they will flood – to put further housing in these areas of unmitigated flood risk would have been a terrible strategy.”  

The ICA, Planning Institute Australia and Master Builders Australia held a roundtable in July to press home the issues that exist around Australia when it comes to floodplain risk, and to make the case for changing rules to the nation’s planning ministers. 

The region west of Sydney provides a stark example of risk, but the record-breaking floods of the past two years have shown just how much of the country is exposed and many of those areas are far less well modelled and understood. 

Driving change is also never easy when federal, state, territory and local governments are all involved, along with a myriad of departments and agencies. 

There’s been strong progress on mitigation project spending, which is one part of the action needed to address natural catastrophe issues, and the insurance sector is hoping there’s gathering momentum on preventing high risk developments being built in the first place.