The widespread flooding in northern NSW has prompted the Insurance Council of Australia to add the region to its catastrophe declaration in the wake of Cyclone Debbie.

Flood waters were expected to peak on Thursday afternoon for rivers in the state's north, with the Tweed, Wilsons and Richmond valleys of most concern.

Lismore, a major centre on the Wilsons River, had its 10.6 metre levee breached, with flood waters expected to peak at about 11.8 metres, the Bureau of Meteorology said.

The Insurance Council's declaration comes as some 7500 claims for damage had been lodged from Queensland alone after the category-four cyclone slammed into the coast near Bowen and the Whitsunday Islands on Tuesday.