The swollen Drupromg last night submerged village Duprong and washed away the Rangiya-Jonai-Mukongchelek metre gauge rail tracks near Tatibahar station affecting movement of trains to the neighbouring state, official sources said.
The Arunchal Express and other goods trains pass through the railway track, they said.
An estimated 2.5 lakh people were affected by the first wave of floods in the state as the Brahmaputra and its principal tributary Subansiri rose above the danger level, fed with incessant rain waters from the Himalayan foothills in Arunachal.
In worst-affected Lakhimpur district, both the rivers were in spate with the Subansiri flowing one metre above the danger level at Silikhagur and Ghonsoraighat, the sources said.
The Gohin river rose menacingly and threatened to breach a dyke and affect the construction work of state's second veterinary college in Lakhimpur district.
Meanwhile, most parts of the two rhino habitats of Kaziranga National Park in Golaghat district and Pobitora Wild Life Sanctuary in Morigaon district near Guwahati were submerged, wildlife department sources said.
The animals in both the parks were safe taking shelter in the highlands and round-the-clock patrolling continued against poachers.