The data of Assam State Disaster Management Authority showed that the Brahmaputra was flowing over danger mark at Nematighat in Jorhat district.
Two of its tributaries -- Dhansiri and Jia Bharali -- were also flowing over the danger mark at Numaligarh in Golaghat and N T Road crossing in Sonitpur, respectively.
In nine districts, 248 villages have been submerged, ASDMA said.
As per official sources, over 75,000 people have been affected in this spate of flood. A 12-year-old boy has died at Jengpuri in Morigaon district.
Flood and erosion have devastated human habitation and crop fields in Morigaon's Bhuragaon and Mayong revenue circles.
5,000 hectares of agricultural land with standing crops, including rice, have been damaged, it said.
The Brahmaputra has left 100 families homeless at Jengpuri, Nathgaon and Boralimari under Bhuragaon revenue circles of Morigaon district.
Three relief camps have been set up in Dhemaji district, where nearly 1,000 people are taking shelter.
Six roads, one bridge and three culverts have been damaged in Golaghat district and an embankment each breached at Madanpur and Chandpur in Karimganj district, the Authority said.
In Dhemaji, erosion has been noticed on Khalihamari Butikur Road. Temporary restoration work has been carried out at the affected stretches.