The disbelief was tangible at the Queensland flood inquiry yesterday when the Bureau of Meteorology gave evidence that it has no ability or responsibility for forecasting flash flooding.

Queensland regional director Jim Davidson told a courtroom packed with lawyers, government officers and local flood survivors yesterday the first he knew of Toowoomba’s flash flood was when he walked into the bureau’s forecasting room and saw meteorologists and hydrologists watching video footage on television. Its three radars had all been indicating rainfall rates on the “high end of moderate” that day and had not shown the true rainfall rates.

But radar images could under or over-estimate rainfall rates by a factor of two to four and became more inaccurate the heavier the rainfall, he said.

Today, the inquiry will hear recordings of the 000 calls made by Donna Rice and her son, Jordan Rice, 13, from their Mercedes sedan, minutes before they were swept away and drowned in Toowoomba’s flash flood in East Creek on January 10. Counsel assisting the Commission Elizabeth Wilson said the content of the phone calls was distressing and the inquiry would examine the behaviour of a senior constable of police who took the calls and the response of emergency services.

But it was the bureau’s response to the disaster that captivated the assembled journalists, victims and officials yesterday. Davidson told the inquiry extraordinarily high river gauge readings at Helidon had been automatically flagged by the bureau’s computer system as errors. Only when staff saw vision of the flooding did they realise the readings were correct.

“The bureau was unaware that Grantham could be flooded by Lockyer Creek,” he said. “No one had rung the bureau to say we had a problem.”

Once they knew there had been deaths and widespread destruction, the office stepped beyond its responsibility to create a template for issuing an extraordinary flash flood warning.

“We made a template — we just forgot about the books and turned on the SEWS [Severe Weather Warning Siren] as well,” Davidson said.

Davidson said that although the bureau had statutory responsibility for weather warnings, there was a change made in 1987 that the bureau would not be providing flash flood warnings and this would become a local government role. Local councils were the lead agencies to establish end-to-end flash flood warning systems in their local areas, assisted by the bureau.

Davidson said many councils had strong relationships with the bureau but Toowoomba Regional Council was “not one of the strongest”.

In his 40 years as a meteorologist Davidson said he had never seen an upper level low so late in the season.

On January 10, the bureau had joined in a teleconference from 11-11.40am run by the State Disaster Co-ordination Centre, an office three to five metres away from the bureau’s office in Brisbane. During the teleconference, meteorologists had spoken about the rain storm in Esk that was heading for Toowoomba, but it was not until 11.55am that a meteorologist phoned the SDCC to alert them to the possibility of flash flooding in Toowoomba.

Davidson said it was normal procedure for the bureau not to upgrade a severe weather warning to a flash flood warning until there was confirmation by someone on the ground phoning the bureau to let them know there was a flash flood.

But a meteorologist received a phone call from a storm spotter at Cressbrook Dam at 12.39pm and in turn phoned the State Disaster Centre to “give them a heads up” that there was exceptionally heavy rain on the way and it could cause flash flooding in Toowoomba in the following hour.

Flood Commissioner Justice Kate Holmes asked Davidson why it did not cross anyone’s mind to phone Toowoomba. “It’s not something we would ordinarily do. The SDCC knows better than we do who to ring,” he said.

Earlier in the day, an independent hydrologist told the inquiry the bureau had enough information to issue flash flood warnings more than five hours before it issued the 5pm warning after flash flooding had already killed 21 people and destroyed hundreds of homes in Toowoomba and the Lockyer Valley.

Showing BOM radar images on a screen in the court, Sinclair Knight Merz senior hydrologist Dr Phillip Jordan said that by 11.48am on January 10, the bureau had enough information from its radar to indicate two storm cells had converged and intensified to form a storm 40 kilometres in diameter that was dropping rain at up to 100mm/hour. The storm was moving at 30km/hour across the Lockyer Valley towards Toowoomba where the catchments were already saturated by previous rainfall, causing immediate run-off down steep catchments.

He said a flash warning for Grantham and communities downstream could have been issued at least by 2.45pm when the Helidon river gauge shot from four metres to 12 metres in 23 minutes.

At Murphy’s Creek the rain gauge at Holmes Station recorded 93mm in an hour — a one in 350 year event — and on the Toowoomba escarpment a rain gauge at Prince Henry Drive recorded 94mm in an hour, equivalent to a one in 370 year event. Neither of these rainfall gauges feed information in real time to the bureau.

Dr Jordan said flows in the mountain creeks peaked almost simultaneously and joined at Helidon where the flow in Lockyer Creek was 3500 to 4000m3/second. As the flood reached Grantham it broke the creek banks and flowed through the town, backing up once it hit the railway embankment.

Dr Jordan said if warnings of flash floods were to be improved, a new hydrological model would be needed to model each catchment incorporating rainfall data and radar image data to create automated flash flood alerts. He said he thought the bureau was the best-placed organisation to undertake the task.