5 Conclusion
The principal conclusions from this study can be summarized as-
- This study on the short-term dynamics of the Brahmaputra River shows
its erosion-dominant nature with an overall channel widening of
~1.7 km in the last four decades. Erosion and
accretion are dominant in braided sections of the Brahmaputra River,
while it is limited in nodal sections.
- There are five stretches- lying in lower, middle, and upper reaches-
identified as the most dynamic sections of the Brahmaputra during the
study period. The lower active stretch lies in Bangladesh and impacts
both banks along Brahmaputra-Jamuna. Two active stretches in the
middle Brahmaputra division lie near the confluence of Manas on the
right bank and along the upstream of Guwahati on the left bank. The
remaining two active stretches lie in the upper reaches near the
confluence of Subansiri and Lohit tributaries.
- Brahmaputra-Jamuna is identified as the most dynamic stretch which is
mostly active in the initial decades (1976-1998). A trend of decreased
bank erosion in the Brahmaputra-Jamuna during recent decades is
noticed, attributed to relatively efficient channel evolution over
time.
- The active sections in the middle and upper divisions of Brahmaputra
are promoted by lowland areas in the floodplain and rapid bed
aggradation.
- Sustained and dominant second order channels have largely decided the
intense erosion in major eroding sections of Brahmaputra.
- The observed morphological change of the Brahmaputra River is the
continuation of the recent planform evolution of the river that can be
traced back to 2-3 centuries where seismically induced high
sedimentation looks to be a dominant trigger.