17 of the 23 dams in the affected area are 100% full or above capacity. The largest, Wivenhoe Dam is currently at 190%. All dam floodgates are fully open and have been for over a week Except Wivenhoe which had all 5 gates opened fully as of last night.
Its maximum capacity is 225%
Professor Hubert Chanson, a professor in hydraulic engineering at the University of Queensland, says the dam was built to withstand an event similar to what we are seeing. However......
"The Wivenhoe Dam is not designed to be overtopped, it is what we call an embankment dam. And if water was to flow over the top of the crest of the dam, there would be a very high risk of erosion of the dam wall and ultimately failure of the dam," he said.
"If the water was to spill over the top of the crest of the dam we would look at the failure of the dam on the possible complete emptying of the reservoir into the Brisbane River with deadly consequences for the people living downstream."
But he says there are a number of safeguards to prevent such an event.
"The first one is the primary spillway, the main spillway you have seen on the TV news," he said.
"That is the location where they are currently controlling the downstream release of water into the Brisbane River.
"But they also have a secondary emergency spillway where if the water were to reach dangerous levels it would start to provide further release from the dam wall."
Some towns have been hit twice in a few days by flash flooding. The water is making its way down to Brisbane and shoud peak tonight.
