Wivenhoe dam holds 2.6 million megalitres of water. Catchment area of 5500 square kilometers. Currently at 190% of expected capacity. at 225% it overflows uncontrollably. They've been dumping 250,000 megaliters per day into the Brisbane river even during the flooding to prevent the dam from overflowing it's banks.

3 weeks of more rain or a cyclone, will IMO, overflow and then you enter territory of a dam failure....

Care to think what 2.6 million million litres of water will do to the Brisbane river and brissie suburbs ?