Flood basins put to the test

Busselton’s multi-million dollar compensating basins were put to the test during heavy rains recently.

The State Government’s Flood Mitigation Project was completed at a cost of $20 million in 2009 in response to flooding in Busselton in 1997.

The three basins are capable of holding nearly 5 million cubic metres of water during a major storm, gradually releasing it back into the system over the following days.

Water minister Terry Redman confirmed all three basins were used last week to lower peak flows in the Vasse River diversion drain and prevent flooding.

On Thursday 8 August, the water level in the basins reached an average maximum height of 2.14m, dropping down to 0.4m by Monday.

Minister Redman said the basins had served their purpose as a flood mitigation tool.

“Last week, Busselton received approximately 75mm of rain over a three day period. The compensating basins captured additional water, with levels of all three compensating basins rising significantly, effectively lowering the peak flow,” Minister Redman said.

“This prevented this additional water making its way into the Vasse River diversion drain and subsequently flooding the surrounding area.”

Minister Redman said before the compensating basins were installed Busselton received 100mm of rain over two days in 1997 and the drains overflowed causing localised flooding.

“Without the compensating basins in place, Busselton would likely have experienced similar flooding as a result of the recent rain,” he said.

Real estate agent and farmer Chris Kemp said he looked at the compensating basin near Busselton Regional Airport last week.

“If the basins weren’t there the water would have gone through Busselton and the drains would not have coped,” he said.

Mr Kemp said he thought the basins could possibly be breached during future heavier storms, but this would likely require substantial rainfall for an extended period.

“It was a cool thing to see, seeing this massive lake in what is normally an open paddock,” he said.

At midday yesterday, Busselton had received 96.6mm of rain so far in August – only 8mm less than the monthly average.

The forecast is for continuing showers until Monday before a sunny change on Tuesday.