'Useful data' flows from study
THE head of the Warwick Shire River Improvement Trust has welcomed the draft of a new flood study for the Condamine River, which he says gives a clearer picture of likely flood height and speed of water flow.
Talgai producer David Brown chairs the trust, which is responsible for carrying out erosion control and flood mitigation works along the river and its tributaries.
Mr Brown yesterday said when formally in place, the flood study by Brisbane-based consultant hydrologists SKM would allow council to better control development on the flood plain.
A draft of the study was handed out to Southern Downs Regional councillors this week and will be placed on public display in the coming weeks, with Mr Brown describing it as "a very comprehensive document".
"The study gives us what I feel is a clearer picture into cause and effect, such as the issue of non-native species of vegetation which have proliferated along the river and adjoining creeks in recent decades," Mr Brown said.
"Willow trees in particular can trap debris coming downstream during a flood and this can have the effect of pushing floodwater into places it has never been before.
"Debris which collects at the Madsen Bridge in Warwick also has the effect of worsening the situation."
Mr Brown said while the December and January floods in the Condamine River catchment caused widespread devastation, they had given the hydrologists a new set of data to work with in determining where development should be controlled in the catchment.
"The combination of recent and historical data will also allow us to better design new infrastructure, such as bridges, to account for the potential reach of floodwaters," he said.
"What the study does bring up is a need for more flood gauges and in better locations so we can more accurately measure what happens when there is a flood."
The study does reveal that in the case of Allora, the predicted or "design" flow of water in a flooded Dalrymple creek has been estimated in the past at 450 cubic metres per second, but actual flows in the December flood were double that velocity, at 900 cubic metres per second.
The discrepancy has been blamed on a lack of adequate rainfall records from the area.