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'''Old Brahmaputra River''' a river that originates from the left bank of the [[Brahmaputra River|brahmaputra]] to the north of Bahadurabad. Flowing more or less to the southeast it passes by Jamalpur and Mymensingh towns and falls into the [[Meghna River|meghna]] at Bhairab Bazar. River shifting has been a characteristic feature of the [[Bengal Basin|bengal basin]], affecting small sections or even the entire river. The most dramatic was the shifting of the courses of the [[Tista River|tista]], Brahmaputra and lower [[Ganges River|ganges]] river channels as evident from maps prepared hundreds of years ago. James [[Rennell, James|rennell]] produced the most accurate map back in 1760. According to this map, the Brahmaputra at that time was flowing a course east of the [[Madhupur Tract|madhupur tract]], presently known as the Old Brahmaputra. The lower part of the Brahmaputra channel between Dhaka and Mymensingh subsequently was silted up diverting the Old Brahmaputra flow to [[Shitalakshya River|shitalakshya]] river and then to the [[Dhaleshwari River|dhaleshwari]] and Meghna rivers southeast of Dhaka.

The Old Brahmaputra acquired its present course between the Madhupur Tract and the [[Barind Tract|barind tract]] in the year 1787. In that year the river shifted its course and was named the [[Jamuna River|jamuna]]. This shifting followed a major [[Flood|flood]] in the same year. The severe [[Earthquake|earthquake]] reported from Mymensingh region in 1782 may also have contributed to this shift. The shifting of the Old Brahmaputra, along with other major shifting rivers, is now considered the effect of neotectonic activities in recent times. The shifting process seems to have taken place over a period of 30 years. The Old Brahmaputra floodplain stretching from the southwestern corner of the Garo Hills along the eastern rim of the Madhupur Tract down to the Meghna river exhibits a gentle morphology composed of broad ridges and [[Depression1|depression]]s. [[Soil|soil]]s of this geomorphic unit are more oxidised and darker than soils developed in the last 200 years on the Young Brahmaputra Floodplain. [[Groundwater|groundwater]] in the unit has a characteristic chemical composition. [Kazi Matinuddin Ahmed]

''See map in'' [[Brahmaputra-Jamuna River System|brahmaputra-jamuna river system]].

[[Category:natural sciences]]

[[bn:পুরাতন ব্রহ্মপুত্র নদ]]

Old Brahmaputra River - Revision history

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