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.

The government also believes an even larger dam wall would allow developers to build thousands of hectares of urban sprawl across western Sydney floodplains. What they are not highlighting is the vast increase in revenue which might also cover the cost of extending Warragamba’s wall.

Both the Government and property developers think that raising the dam height will allow thousands of houses built on floodplains to be safe from flooding, whilst not appreciating that floods are natural phenomenons which happen regardless of dams. Remember the 2011 Queensland floods?

There is little exactitude in forecasting whether sufficient high rainfall may occur in this area, endangering civilisation without the protection of additional wall height.

It also is similarly uncertain that easily-damaged parts of the environment would be affected if such a rare event did happen, because both downstream flooding and upstream inundation are equally dependent on a weather event outside human control.

In 2012, Infrastructure NSW said a study it commissioned found that a one-in-1000-year flood in the area is possible, meaning that the welfare of residents and workers is one part of a contentious decision the state government must make in the face of fierce opposition by protestors.

 Some dissenters claim that the massive catchment increase in heavy rain with a wall height being mooted would destroy sensitive vegetation, as well as sacred Aboriginal traditional upstream sites. 

A proposal to raise the Warragamba dam wall would flood 4,700 hectares of the Blue Mountains world heritage area, destroying more than 50 recognised Aboriginal heritage sites, and wiping out pockets of threatened plant species, they say.

Indigenous protesters say that WaterNSWclaims that it is going to save more sites downstream, but that a different organisational culture overlooks the appreciation that everything behind the dam wall belongs to the Gundungurra and Dharawal people, and everything that’s downstream belongs to the Darug.

This statement concerns me a little regarding whether the mentioned areas existed as discrete tribal zones before the dam was even built, and also seems at variance with indigenous belief that land does not belong to them – they belong to it.

Among the sites at risk behind the dam wall are rock art sites, burial sites, and ochre deposits in a cave on the waterline, all of which are at risk of being submerged fourteen metres.

Infrastructure NSW  has said it is still assessing the impact on these Aboriginal heritage sites.

It seems reasonable to propose that plant species threatened by flooding could be moved before any wall height increase, similar to back in Warragamba’s planning days when the authorities moved in, and the township of Burragorang Valley was demolished to make way for the building of the dam. The government acquired every property and bulldozed every structure.

Sixty-four square kilometres of bushland also was cleared to avoid dislodged floating trees from clogging the dam outlets, and cemeteries were dug up and relocated.

Why not today’s plants and sensitive indigenous settings?

As a youngster I remember my parents telling me about the many times they holidayed at settlements in the Burragorang Valley in the late 1920s where they enjoyed horse riding, exploring, and camping.

I also remember being driven a number of times to gaze at the massive aerial ropeway system which carried millions of tons of sand from McCann’s island, on the Nepean River just near Penrith, during the dam’s construction. This ropeway worked non-stop, and its impressive lumbering buckets were quite near the ground at places en route.

What this all suggests to me is the reality that such a massive water storage project may never be fully complete.

It also suggests that I would not like to be the government minister charged with making the ultimate decision of whether or not to proceed with this proposed step.