Authorities are conducting new modelling to see what the wall of water ripping through the Lockyer Valley will mean for Wivenhoe Dam, Premier Anna Bligh says.

Much of the deluge that fell in the Toowoomba region and is now ripping a path of devastation in the Lockyer Valley will move into the catchment of the Wivenhoe Dam system that feeds Brisbane.

The Brisbane City Council has warned about 200 properties could be flooded, most in the areas of Rocklea, Albion, Milton and Auchenflower.

Authorities say Wivenhoe Dam, built partly as a flood mitigation strategy after the 1974 flood, was all that stood in the way of a repeat of the devastating event.

Ms Bligh said engineers were assessing what the water would mean for the dam and the water release strategy into the Brisbane River.