Hinze Dam stands up to its biggest test

An analysis into how Hinze Dam operated during ex-Tropical Cyclone Debbie has found its most recent upgrade was a major contributor in reducing the risk of flooding for thousands of downstream homes.

Minister for Water Supply Mark Bailey said heavy rainfall from ex-Tropical Cyclone Debbie in late March produced the largest flow in the Nerang River valley in the past 50 years.

“Hinze Dam reduced the peak outflows by 80 per cent, which prevented flooding for several thousand homes across the vast floodplain of the Nerang River, including Surfers Paradise, Bundall, Carrara and canal estates further to the south,” Minister Bailey said.

“The most recent upgrade which was constructed under Labor governments and completed in 2011, saw the dam wall raised by 15 metres, which has doubled the dam’s capacity and provided increased water security and flood mitigation,” he said.

“There is no doubt this upgrade saved a lot of homes.”

Minister Bailey said a post event analysis undertaken by Seqwater, showed Hinze Dam had significantly reduced the flooding to the Gold Coast’s most populated floodplain area.

“During the event, inflow into Hinze Dam peaked at about 1.9 million litres per second at midnight on 30 March – the equivalent volume of about 45 Olympic sized swimming pools every minute,” he said.

“The water level at the Hinze Dam peaked at a record of 100.28 metres above sea level – about 5.7 metres above the spillway.

“With the Hinze Dam in place though, the peak outflow from the un-gated dam was reduced to 310,000 litres per second, holding back what would have been a disastrous flood. 

“Many people value Hinze Dam for its water supply and recreational use but what is not immediately obvious is the benefit the dam provides for flood mitigation.

“As we plan our long-term water future, Hinze Dam will continue to be a key asset in the South East Queensland Water Grid.”

Seqwater Chief Executive Officer Jim Pruss said Hinze Dam had operated as it was designed to do.

“It was very pleasing to see the dam perform as efficiently and effectively as it did,’’ he said.

“While no dam can flood-proof a community, Hinze Dam will continue to provide significant flood mitigation for the Gold Coast into the future.’’

South East Queenslanders are encouraged to sign up to Seqwater’s free Dam Release Notification Service to receive vital information about dam operations during extreme weather event.”

To sign up go to www.seqwater.com.au/dam-release-information-service or download the Seqwater app.

Hinze Dam history

• Stage 1 of the dam was originally built by the Gold Coast City Council for water supply in 1976. 
• In 1989 the Stage 2 construction raised dam wall and spillway level to increase the water supply and to provide flood mitigation.
• In 2008 to 2011 the Stage 3 construction further raised the dam wall and spillway level to the current height to increase water supply, increase flood mitigation benefits and to upgrade the dam to meet modern dam safety standards. 
• Seqwater’s estimates of earlier floods show the notable June 1967 flood peak inflow was approximately one million litres per second at the location where Hinze Dam is now built.
• The estimate for the January 1974 flood at this location is approximately 1,450,000 litres per second peak flow
• Historical data for previous flood estimates indicate there were some nine previous floods in the past fifty years that exceeded one million metres per second at the site of Hinze Dam.
• Many of these previous floods were also significantly mitigated by the Hinze Dam Stage 2 configuration such as the 1989, 1990, and 2008 flood events.

ENDS

Media contact: Zoe Russell - 0428 079 640