A wealthy Queensland family were portrayed as "selfish", "suspicious" and "disgraceful" by a Nine Network program suggesting they caused the 2011 floods that killed 12 people, a court has heard.

Toowoomba's Wagner brothers are suing the network and journalist Nick Cater for defamation over a 60 Minutes report aired in May 2015 on the wall of water, described as an "inland tsunami", that fatally swept through Grantham.

John Wagner is seen arriving at the Supreme Court in Brisbane on Tuesday. Credit:Darren England/AAP

Denis, John, Neill and Joe Wagner say the report by journalist Michael Usher incorrectly insinuated the collapse of a wall of a Lockyer Valley quarry they owned caused the "man-made catastrophe", in which a two-year-old girl died.

A four-person jury has watched the report, titled The Missing Hour, after the Brisbane Supreme Court trial began on Tuesday.