Qld flood victims testify in Jones' trial

Residents of the Queensland town of Grantham have described how they ran and clung for their lives as a wave of water descended on them during the 2011 floods.

Lisa Spiering fought back tears as she told the Brisbane Supreme Court on Wednesday she saw people drowning as a wave "like you'd find at a beach" chased her along the railway track.

"It had a roll at the front, a crest," she said.

The court heard she, her children and some other residents thought they were safe from the rolling water when they made it to the raised track, only to realise a wave was coming from another direction.

Ms Spiering said their only option was to make a run for it.

"I put my daughter on my back and she kept asking me not to let her die," she said, adding they managed to make it to the school on higher ground.

Daniel McGuire told the court he spent six hours in a tree after his Rural Fire Service truck was hit by waves of water and pushed into a ditch.

"The impact of the water was roughly like a cyclone on the beach, it was really going for it," he said.

Ms Spiering and Mr McGuire are giving evidence in defence of talkback radio host Alan Jones, journalist Nick Cater, Harbour Radio and 4BC, who are being sued for defamation by the Wagner family over 32 broadcasts between 2014 and 2015.

Brothers John, Denis, Neill and Joe Wagner claim they were accused of the deaths of 12 people in Grantham during the floods when one of the walls of a quarry they owned collapsed.

They also allege they were accused of a high-level cover-up with politicians, as well as corruption and intimidation, relating to their Wellcamp Airport.

Tom Friend was not in Grantham when the floods hit but his property was destroyed.

Mr Friend, whose land was near the Wagner family's quarry, told the court he noticed mounds of dirt on the western side of the site increased in size in the years prior.

The trial continues.