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One of two river gauges upstream of Eugowra showed Mandagery Creek rising as much as 35 inches per hour Sunday night as rain fell over the northeastern reaches of the Lachlan Basin.
But Water NSW, which manages the meters, said they existed to provide information to government agencies for planning purposes and were “not designed or intended for an instantaneous emergency management function in the event of flash flooding.”
A Department of Industry map shows four other gauges above Eugowra that are no longer working or are managed by a different agency.
Meanwhile, the nearest rain gauge that sends real-time rainfall figures to the Met Office is at Forbes, 50 kilometers downriver from Eugowra.
The rain gauge in Eugowra has not recorded any data since November 1, according to the office’s website, and the nearest working rain gauge, 17 kilometers to the north, only sends data to the office once a day, at 9 a.m. a. flag if there is a sudden extreme gust of rain running into the creek.
Former NSW chief scientist Mary O’Kane, who co-led the NSW Independent Flood Inquiry earlier this year, said a comprehensive and well-maintained network of meters was critical to helping authorities see how an event was unfolding. , especially when it came to places at risk of flash flooding.
Cameras focused on risky rivers could also be useful, along with remote sensing, radar and aerial surveillance.
“All of that needs to be merged together, so that you get a better picture of what a given flood is doing, but also for later modeling,” he said.
The inquiry recommended that the state government improve the network of rain gauges and rivers, to make flood warnings and modeling more accurate, and build on existing radar to ensure there are no gaps in coverage. He also suggested that more data be provided to residents in real time, to ensure they are informed of any flood risk.
Meteorologist Anthony Cornelius, who runs a private service called Weather Watch, said the computer model used by the bureau to report its forecasts initially predicted heavy rain for the southern Tablelands on Sunday, not the central west.
“There are limitations to the tools we have in Australia,” he said. “They are not detecting these high intensity rain events. They can be quite unpredictable.”
Australia would benefit from a more powerful computer model to better predict extreme rainfall, as well as a better rain gauge network and more research into Australia’s extreme weather, also recommended by the Independent Flood Research.
“It needs to be a priority to understand what is driving our rainfall patterns,” he said. “[On Sunday] We knew there was going to be something wrong, but you couldn’t necessarily pinpoint the location.”
UNSW water resources expert Ashish Sharma said the rainfall would only become more intense due to climate change, leading to higher possible flooding, and that the measurement network needed to be improved to improve the flood modelling.
His team has just published a paper warning that maximum daily rainfall could increase by as much as 38 percent between now and 2100 in Australia.
That significantly increased the risk of dam failure, he said, because it meant that “probably peak flood” levels would be higher now than when the dams were built.
“A dam is supposed to overflow with a certain frequency and they are designed to accommodate that, but if the volume of water coming in is too much, there is a risk that it will overflow… [then it] It starts to get dangerous in terms of the stability of the dam,” he said.
Authorities would have to consider engineering solutions to improve the safety of dams like Warragamba, where failure would be catastrophic.
Sharma said the data from the river gauges was also important for building accurate flood models, but that the funds to maintain them tended to dry up with the weather, and it was only when the floods came that it became apparent just how valuable the information was. they provided.
“It is very difficult for cash-strapped water agencies to justify obtaining these observations, which are expensive. One person has to go and measure them. Automation is not completely possible. It’s hard to justify the cost when nothing has happened for so many years. Most managers are thinking about the next two or three years, not 100.”
The Bureau of Meteorology has been contacted for comment.
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