More than 1700 people are stranded in their homes by floodwaters in northern NSW, as river levels continue to rise.
The State Emergency Service (SES) says that the number of people cut off is expected to increase, as more rain falls on Tuesday.
Areas around Grafton, bordered by the Clarence River, are of most concern to the SES on Tuesday, spokesman Phil Campbell said.
"The Clarence River is probably the big problem for us today," he said.
The river has swollen to 4.2 metres at Grafton on Tuesday morning and is expected to peak at 6.5 metres early on Wednesday, potentially cutting the Pacific Highway and requiring the evacuation of caravan parks.
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Downstream from Grafton the SES has a rescue operation underway on Tuesday with teams called to help two people stranded on the back of a ute in floodwaters on a property near Coldstream.
Three other people were rescued overnight, after more than 25 people were rescued on Monday.
"Ulmarra, downstream from Grafton is experiencing major flooding which is expected to cut the Pacific Highway and result in around 200 people there being isolated," Mr Campbell said.
Further north in the Clarence River valley, 500 people are isolated at Bonalbo, about 200 at Urbenville and another 300 at Tabulam.
To the south, at Darkwood on the Upper Bellinger River more than 500 people are cut off by floodwaters.
The town of Bellingen is cut in two and may be isolated later on Tuesday.
The Bureau of Meteorology released a severe weather warning on Tuesday for flash flooding in the Northern Tablelands, Northern Rivers and Mid North Coast districts.
Flood warnings remain in place for some 14 rivers in northern NSW.
