The Forecast Never Hit the Trigger, So Moreton Bay’s Sandbag Stations Stayed Closed

When the Courier-Mail found a man filling sandbags in the car park of the Caboolture council depot on Thursday afternoon, he admitted he had seen nothing online saying the depot was open. He had come on a feeling.

The City of Moreton Bay’s own explanation, given to Newsreel on Thursday, was that earlier forecasts had not reached the council’s operational trigger for activating sandbag stations. The mechanism never fired. So while a slow-moving cell dropped 243mm on Caboolture between 3am and 9am, about 40mm an hour sustained for six hours, the official stations stayed shut. The council told residents to stay off the roads.

The Bureau of Meteorology’s tally reads like a misprint. The Caboolture Water Treatment Plant recorded 263mm in the 24 hours to 9am Thursday. Sheep Station Creek in Morayfield took 168mm in three hours to 7:30am, and 345mm over the five days since Saturday. Beerburrum registered its wettest October day on record at 170.8mm, more than double the 81.4mm October average. Toowoomba, inland, picked up 42.6mm, its heaviest October day in 29 years and nearly as much as the four dry months from June to September put together.

The system that did open was unofficial. Division 3 councillor Adam Hain used his Facebook page to tell residents the sandbag station at 98 Beerburrum Road was open, while the council’s disaster dashboard listed stations as closed. When the Courier-Mail visited, council workers said the station had been running since midday, with a rush of residents stocking up that morning. Stations at Elimbah and Narangba were listed closed too, but both had piles of sand ready and bags were visible at Narangba. Morayfield MP Mark Ryan, whose electorate took the worst of it, said residents had been caught off guard. “There’s a very rapidly developing event, in some respects it wasn’t forecast to be this heavy and this intense so the usual things about people having to get sandbags just wasn’t there,” he said.

Twenty kilometres south, the arithmetic was different. Brisbane City Council had more than 140,000 sandbags ready at its depots. “Up to 80mm rain is forecast, but we’re ready to assist,” Lord Mayor Adrian Schrinner said. Moreton Bay was the council area the rain actually hit. Of the 277 SES call-outs logged between 6am and 2pm, 152 were in Moreton Bay. And its sandbag stations opened on a councillor’s Facebook post rather than a plan. Premier David Crisafulli called it “typical storm season rain.”

Caboolture resident Sara Wessling told AAP Thursday was the worst flash flooding she had seen. “I had just walked over to have a look at how deep it was getting and saw an older guy flashing his head lights as he had driven into the water not realising how deep it was,” she said. A second four-wheel-drive drove straight in behind him and needed help as well. She called triple zero. As far as she knew, everyone was fine.

Nine schools in the Caboolture region closed for the day. 1,949 properties lost power by mid-afternoon. Most were in Moreton Bay: 1,202. Floodwater inside Morayfield Shopping Centre mixed with sewage after a pipe burst. Unitywater, which runs the wastewater network for Moreton Bay, the Sunshine Coast and Noosa, told residents their toilets might start “gurgling” as stormwater entered the system. The council opened eight libraries as places of refuge.

The creeks told the story in hours. At 6:40am, MoretonAlert’s gauge on King Johns Creek read 1.8 metres, still under the 2.0m minor-flood threshold. In councillor Hain’s warning two hours later it had reached 2.7m, 2.7 metres above normal, and he said another half-metre, possibly thirty minutes away, would bring major flooding. Burpengary Creek hit 10 metres at the Dale Street gauge, 6.5 metres above its usual level, and Burpengary and Burpengary East were told to prepare to leave. At Beachmere, Goong Creek crept over Beachmere Road and cut off properties.

The Bureau’s meteorologists say the setup was the problem. “Because the winds are quite slow coming off the ocean, and the winds through the first few kilometres of the atmosphere are quite slow, that means the storms are slow moving, so that’s what’s making it worse,” BOM meteorologist Robert Urbaniak told AAP. Weatherzone’s Ben Domensino traces it to two streams of moisture-laden air colliding over eastern Australia: one riding mid-to-upper-level winds from the Indian Ocean, another flowing onshore from the Coral and Tasman Seas, meeting a surface trough and an upper-level trough that wrung the moisture out. Up to 270mm in one morning. BOM’s Tristan Sumarna put Thursday morning’s fall across Caboolture at 200 to 270mm. Weatherzone’s Jess Miskelly says the same machinery is due back on Monday.

The severe storm warning was cancelled at 3:13pm. The prepare-to-leave notice for Burpengary and Burpengary East was not.