Giving a dam

Warragamba Dam is in flood!

That’s right. Despite the dam’s present low water level, media is being swamped with contentious arguments about Sydney Water’s proposal to raise the height of Warragamba’s wall by a further fourteen metres - the equivalent height of four floors of a normal apartment building, 

Not increasing the height is seen as threatening to put 43,000 residents and 9000 local employees at risk of an overflow destroying 6500 homes, and flooding 14,000 homes above floor level.

It is predicted that up to 134,000 people who live and work downstream of the dam, a figure forecast to double in the next 30 years, could require evacuation in the event of a large flood.

Every day, Sydney Water, wholly owned by the New South Wales Government, supplies over 1.5 billion litres of drinking water to homes and businesses.  Its catchment area is over 16,500 square kilometers and about 80% of it comes from Warragamba Dam.

The NSW Government says a decision to raise the wall could provide vital flood protection for downstream communities, and may offer significant extra protection to populations in Windsor, Richmond, and part of Penrith. 

Now, there is a fierce battle between advocates of wall height extension and those defending the flora and aboriginal sacred sites located upstream in the Burragorang Valley.

One factor of this growing conflict is the fact that ever since the dam was constructed between 1948 and 1960, few steps appear to have been taken to highlight flood prone sections of the river, or to restrict building development there.

The Hawkesbury-Nepean Valley is deemed to have the greatest flood risk in New South Wales, which poses a serious danger to life and property in Western Sydney.

Evacuation of that valley would need to be supported by an adequate regional road network, and community education and awareness. Previous community surveys conducted by the State Emergency Service indicate that less than 10 per cent of people have a plan for what to do in a flood, and about 20 per cent of people are unlikely to evacuate when directed to do so. 

Enhancements of the road network would be needed to meet the evacuation requirements of any future population growth in the Valley. Potential options have been identified for road augmentation, including upgrading the M4 motorway, or the Great Western Highway.

Raising the dam wall is expected to reduce any potential economic impacts from flood risk by about 75 per cent on average, with a dam wall that would hold the equivalent of an additional two Sydney Harbours, increasing the upstream water level and costing taxpayers close to $1 billion to build. The NSW Government’s declared reason for such a massive dam project is flood mitigation, despite its already having built an auxiliary spillway in 2002 to provide dam safety and downstream flood mitigation.