Many Gold Coasters had their homes inundated with water after the heavy rainfall from ex-Tropical Cyclone Debbie, but the Queensland Government says that, without the most recent Hinze Dam upgrade, the event could’ve been a lot worse.
“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,” The State’s Minister for Water Supply Mark Bailey said.
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The Minister said heavy rainfall from ex-Tropical Cyclone Debbie produced the largest flow in the Nerang River valley in the past 50 years, and that the most recent upgrade – which was completed in 2011 and saw the dam wall raised by 15 metres – doubled the dam’s capacity and provided increased water security and flood mitigation.
“There is no doubt this upgrade saved a lot of homes,” said Minister Bailey.
“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,” he said.
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.