Questions and Answers

Questions and Answers

Find key facts and commonly asked questions about the Proposal below.

Technical studies and surveys are currently underway to inform the Environmental Impact Statement. The detailed information on the findings will be placed on public exhibition. If you would like to be updated about the Proposal and notified of the public exhibition period please email the Warragamba Dam Raising team at

There is a very real and substantial existing risk to life, property and community from rapid and deep flooding in the Hawkesbury-Nepean Valley after significant rainfall events.

For example, if a flood similar to the worst on record in the valley happened now, around 90,000 people would need to be evacuated, 12,000 homes would be directly impacted by floodwater, and there would be more than $5 billion dollars in damages to homes, businesses and critical infrastructure.

The proposal to raise Warragamba Dam for flood mitigation, would significantly reduce this risk to people’s lives and livelihoods downstream, provide more time for evacuation and reduce flood damages by 75% on average.

For more information please see the ‘Land Use in the floodplain’ fact sheet on the Infrastructure NSW website at Hawkesbury-Nepean Valley Flood Risk Management Strategy.

Temporary inundation of the Greater Blue Mountains World Heritage Area and National Parks occurs now during flood events.

Raising Warragamba Dam to create a flood mitigation zone of around 14 metres would temporarily hold back floodwater upstream of the dam for a matter of days to around two weeks, while the floodwaters are gradually released.

The duration and depth of temporary flooding would vary as it relates to the specific location, the size of the flood, the level of the dam storage at that time, the inflows from the dam's tributaries, and the rate of the managed release of the captured floodwaters.

Comprehensive ecological studies are currently being undertaken to assess the upstream impacts of a temporary increase in upstream inundation which will be fully documented in the Environmental Impact Statement.

Preliminary modelling indicates a temporary inundation increase in the Greater Blue Mountains World Heritage Area of 0.04 to 0.05% of the total area (1,000,000 hectares). This equates to an area of 400 hectares for a 1 in 100 (1%) chance per year flood, and up to 550 hectares for the Probable Maximum Flood or PMF, which has approximately a 1 in 100,000 chance of occurring in any given year.

There is only one declared wild river located in the Warragamba Dam Catchment – the Kowmung River. Based on preliminary modelling, there would be no change to the level or extent of inundation for the Kowmung River, its streams or tributaries, with the proposed wall raising. As part of the environmental assessment, the impact of temporary inundation on other rivers and streams is being analysed.

Flooding of areas upstream of Warragamba Dam happens now during significant rainfall events.

Comprehensive ecological studies are currently being undertaken to assess the upstream impacts of a temporary increase in upstream inundation as a result of the proposal to raise Warragamba Dam for flood mitigation. This includes assessing impacts on threatened plant, animals and ecosystems and identifying measures to mitigate impacts where possible. The findings will inform the Environmental Impact Statement which will be made available for public comment.

A detailed Aboriginal Cultural Heritage Assessment is being undertaken as part of the environmental assessment process. This process has been developed and is being undertaken in close collaboration with Registered Aboriginal Parties, including traditional owners, the Gundungurra Tribal Land Council.

The impacts on Aboriginal cultural heritage values from infrequent and temporary upstream inundation and options for minimising the impacts, will be assessed in the Environmental Impact Statement.

Registered Aboriginal Parties have participated in the field surveys, will review the Aboriginal Cultural Heritage Assessment Report, and are being consulted on the proposed options for mitigating and minimising impacts.

Regular and ongoing consultation with Aboriginal communities is being undertaken in accordance with the NSW National Parks and Wildlife Regulation 2009 and its legislated instruments — the Aboriginal Cultural Heritage Requirements for Proponents 2010 which establishes a process to consult any Aboriginal people who hold cultural knowledge relevant to, or who have a right or interest in determining the cultural heritage significance of Aboriginal objects and places in the potentially impacted area.

Following early discussions with the Gundungurra Indigenous Land Use Agreement Consultation Committee, WaterNSW engaged a respected Aboriginal heritage consultant with links to the Gundungurra People and specialised knowledge of Aboriginal heritage in the Blue Mountains region to participate in conduct of the survey.

The Aboriginal Cultural Heritage Assessment methodology was agreed in consultation with traditional owners. Aboriginal groups and individuals from the Registered Aboriginal Parties for the proposal have also been participating in the field surveys and will review and provide input to the Aboriginal Cultural Heritage Assessment Report.

The report will be included in the comprehensive Environmental Impact Statement being prepared for the proposal.

There are a number of ways the community has had, and will continue to have, input to the Environmental Impact Statement including:

  • directly contacting the project team by email, phone or letter to provide feedback
  • participating in the surveys for the socio-economic impact assessments
  • talking to the project team at information sessions, community workshops, briefings or community forums
  • making a formal submission to Department of Planning and Environment when the Environmental Impact Statement is on public exhibition.

Our community webpage provides a detailed breakdown of the engagement activities undertaken to date.

We invite all community members to view the Environmental Impact Statement during the display period and make a submission about what matters to them. All submissions will be addressed as part of the subsequent Preferred Infrastructure Report. More information about how to view and make a submission will be available closer to the display period.

To raise awareness in the community regarding the role of the environmental assessment and to engage with the community and other stakeholders at a stage when the scope of the project and environmental assessment can be influenced.

We will keep the community informed about the progress and status of our technical studies and surveys, and the timing of the public exhibition of the findings in the Environmental Impact Statement.

Early and ongoing community engagement ensures information about the proposal, and the environmental assessment process, are known so community members can have their say and provide input into the proposal.

The proposal to raise Warragamba Dam for flood mitigation will be considered under both NSW and Australian Government legislation. Construction can only begin if the environmental and planning approvals are granted and once the NSW Government has made a decision on a final business case.

WaterNSW is currently undertaking technical studies and surveys to inform an environmental impact statement which will be placed on public exhibition. Formal submissions can be made by any organisation or individual and submissions are encouraged. If you would like to be notified about the public exhibition period, and how to make a submission, please register for proposal updates by emailing

The NSW Government’s consideration of a Final Business Case for the dam raising proposal is not expected until 2020 (subject to all environmental and planning approvals being obtained).

Contact the Warragamba Dam Raising team:

Call: 1800 932 066


The Flood Strategy

Contact the Hawkesbury-Nepean Valley Flood Risk Management Directorate, Infrastructure NSW on:


The Flood Strategy is available online at:


Sunday 17 January
2,410,467 ML
2,581,850 ML
10,599 ML
1,515 ML
-29,081 ML
Sunday 17 January