Three major rivers in Tangail swelled in the 24 hours to Sunday morning inundate new areas across the district.
Bangladesh Water Development Board (BWDB) said water at several points of the Jamuna, Dhaleshwari, and Jhenai rivers were flowing above the danger level.
The rise in the water level has flooded low-lying areas near Tangail district town as well as Nagarpur, Kalihati, Bhuapur, and Basail upazilas.
Thousands of people have been marooned due to the flood, which is likely to damage the crops.
The water in Jamuna River is flowing above 26cm of the danger level while the Dhaleshwari above 40cm and the Jhenai above 60cm of the level.
“The water level of the rivers is likely to rise further,” said BWDB Executive Engineer Sirajul Islam, who is based in Tangail.
Erosion, which has already hit several areas in the district, will become severe when the water recedes, added the official.
Flooding in low-lying regions across Bangladesh is worsening as rivers continue to swell due to heavy rains in the upstream.
The water level of the major rivers has been rising since the third week of August, triggering floods in the lower reaches of at least five other districts.
The situation began to improve earlier in the week but has since taken a turn for the worse, leaving thousands of people stranded in Kurigram, Nilphamari and Faridpur.
Out of the 109 points observed by the BWDB’s Flood Forecast and Warning Centre, water was flowing above the danger level at 12 places.
The situation in Kurigram, Tangail, Sirajganj, Pabna, Manikganj, Rajbari, Faridpur, Shariatpur and Chandpur districts may deteriorate, it warned.
The rains are likely to increase as a low-pressure area has formed over the northwest Bay of Bengal, according to Bangladesh Meteorological Department.
