THERE are fears more than 300 properties in southeast Queensland - including more than 200 homes - could be swamped by "unprecedented" floodwaters this afternoon.
The figure already includes more than 100 flooded homes and businesses in low-lying areas of Logan as the Albert and Logan Rivers swell to never-before-seen levels.
Logan Mayor Luke Smith on Friday said flood modelling for low-lying areas along the Albert River was changing by the hour and 211 more homes in the area were expected to go under.
"The Albert River has increased and is continuing to increase much to our surprise," he said.
"We are seeing roads cut off even more and we are seeing heavier inundation than predicted."
He said the river was at an "unprecedented state" and local authorities were now waiting to see what that meant for localised flooding.
"We have never seen the kind of inundation we have right now in the Albert River catchment areas, and now we are focusing on the Logan River catchment over the next 24 hours," he said.
Logan River catchment areas are on high alert over the next 24 hours.
The Logan River had almost reached its predicted peak for midday on Saturday and was staying higher for a lot longer than expected, Mr Smith added.
"It actually could rise above the Waterford Bridge on Logan River Road," he said.
Water was already lapping just under the bridge early on Friday afternoon after evacuations began earlier in the day, while other nearby creeks were rising.
"The mayor will tell you that we've never seen the heights of the floodwaters down here before ,"
Premier Annastacia Palaszczuk told reporters in Beenleigh, where the local train station has been swamped by floodwaters. Windaroo resident Craig Collard told AAP the water levels are over bridges built over the high watermarks from the 1974 flood.
'We've never seen it over this before," he said.
At Premier Anatasicia Palaszczuk's media briefing at Beenleigh State High School this afternoon, Logan City Mayor Luke Smith said 106 homes were already flooded.
A total of 323 are expected to become inundated in the coming hours.
211 other homes in the region may also experience some flooding.
"We've never seen this kind of inundation we've had right now in the Albert River catchment," Ald Smith said.
"The river is at an unprecedented state."
Police fear residents trying to flee floodwaters could be trapped because of 'rubber-necks' clogging roads.
Roads north and south of the Gold Coast are experiencing lengthy traffic jams as thousands of residents are evacuated.
The M1 is closed in both directions at Tweed Heads and police are urging people to avoid unnecessary travel.
"A number of roads in the Kingscliff, Chinderah, Tweed South and Tweed Heads areas have become congested with vehicles and there are concerns motorists attempting to flee may become trapped in rising flood waters," a NSW police spokesman said.
"The M1 Motorway is closed in both directions between the Tweed Heads exit and Tweed Valley Way.
"Residents in high level areas are asked to remain in their home and avoid travel on the road where possible. Residents in low-lying areas are urged to move to higher ground and seek shelter."
Traffic jams are also being reported in the Pimpama-Jacobs area, parts of which is being evacuated.
Ms Palaszczuk said Waterford MP and fellow minister Shannon Fentiman's home was among those flooded.
But the Premier stood by her eleventh hour decision to close all school yesterday.
"It reaffirms the decision we made at the advice of experts to close the schools."
Beenleigh State High School is among those that have experienced flooding.
Queensland police commissioner Ian Stewart said the residents could expect river peaks to coincide with high tides at midnight and midday tomorrow.
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