At least a dozen personnel were injured when two military vehicles on rescue and clean up duties in northern NSW crashed, and authorities on Sunday morning warned people not to become complacent as heavy rain and winds from a weakened cyclone lashed Brisbane and towns up and down the coast.

One man was confirmed to have been swept to his death by floodwaters near Dorrigo, inland of Coffs Harbour, in the first known fatality caused by ex-cyclone Alfred, which was downgraded on Saturday but was still bringing wild weather to a huge area.