June 1, 2021
To supporters, raising the wall of Warragamba Dam offers a way to protect hundreds of thousands of people living in low-lying areas in Western Sydney. Opponents point to the threat of environmental and cultural destruction from higher water levels upstream of the dam.
The NSW Parliament is conducting a Senate Inquiry on raising the dam wall 17 metres higher, a move supported by the Department of Planning and Infrastructure NSW.
In theory, the idea is to use a higher dam as flood protection rather than water supply, which means keeping the new extra capacity empty at all times.
There is one problem with this strategy: in a major rain event, the higher dam wall will still not be nearly enough to protect the flood plain. It will only work for smaller amounts of rain.
If a flood similar to the record-setting 1867 flood occurred today, the estimated damage across the valley would be $5 billion, and it would take six months or more to restore critical infrastructure. Raising the dam would not prevent this damage.
Raising the dam might be useful for other reasons, but it won’t solve the problem of badly-located development. We have to face the fact that 134,000 people are living and working in the flood plain today, and they are living with a severe risk.
This is why the Flood Prone Lands package release by Planning last week is an important first step. It provides local government with the flexibility to manage the complexity of flood risk, rather than just using a line on a map.
But it’s not the end game. It’s just the beginning of improving how we manage risk.
For instance, some evacuation routes are already at capacity, leading the relevant Minister to hold back development in places like Marsden Park North until this human safety issue is resolved.
We think the Minister is onto something here. Don’t stack more demand onto at-capacity roads. Don’t create more uninsurable addresses. In short, don’t put more people in the way of the floods.
And make this plan future proof, especially as events like the March 2021 floods are projected to increase in frequency and intensity, increasing insurance premiums and reducing the length of time available for recovery.
It’s time to make a long term plan to reduce the number of people and households living in harm’s way, for assisting vulnerable people to relocate to safer grounds, and to absolutely, totally prohibit new housing in locations like this where it is not safe.
In 1810, Governor Macquarie sought to move settlers from the Hawkesbury and Nepean rivers to higher ground after repeated floods.
Two centuries later, in 2015, the Productivity Commission identified land use planning as “perhaps the most potent policy lever for influencing the level of future disaster risk.”
Today, the NSW Government is working on a Regional Land Use Planning Framework to manage the Hawkesbury-Nepean Valley.
This plan needs to set a clear vision and action plan for how the Government will reduce the number of people at risk to floods across the floodplain.
Through zoning, tradeable development rights, and upgrading evacuation routes, the plan should reduce the risk to current residents, and stop adding new ones. And through a buy-back policy, it should provide a safety net for those unable to afford insurance, or to rebuild post-disaster, to exit the floodplain.