Qld quarry slowed Grantham flood: owner

A new inquiry into the Lockyer Valley floods will show a quarry actually reduced the severity of the inland tsunami that hit Grantham, the facility's owner believes.

Twelve people died on January 10, 2011, as the flood west of Brisbane tore homes from their foundations without warning.

Locals believe the excess rainfall over the previous week filled a quarry on a creek bend downstream from the town of Helidon before bursting through an embankment and surging down Grantham's main street.

Queensland premier Annastacia Palaszczuk on Tuesday agreed the matter required further investigation, and ordered a new commission of inquiry.

The inquiry, which will begin next week, will focus primarily on what landscape features - including the quarry - contributed to the flood, and to what extent.

Former quarry owner Denis Wagner said he was confident the inquiry would show it actually slowed the flow of water.

"It delayed the time the water hit Grantham and it reduced the height of the water in Grantham," he told the ABC.

"Let's get the facts on the table again and talk about the facts rather than speculation."