[01] Kuldeep Pareta, DHI (India) Water & Environment Pvt Ltd., New Delhi, India.

The construction of any structure on a river affects its flow and morpho-dynamics. A river like the Brahmaputra, which has a high volume of flow and sediment, can have huge consequences. Therefore, a morphological study understanding the effect of a structure on a river is also necessary. The present paper focusses on the morphology and morpho-dynamics of Brahmaputra river near the Bogibeel bridge, which aim is to investigate the effect of the bridge on the river morphological behaviour and to inspect any attack on the structure of the bridge and its components (guide bunds, embankments, abutments) by the river. This study of the reach of Brahmaputra river near Bogibeel bridge has been carried-out using the cross-section data - bathymetry data (2004-2017), Landsat satellite imageries (2004-2021), and field assessment data (2020). Morphological dynamics of rivers are affected by any natural and anthropogenic perturbation in the system. The effect of any structure can be seen in the morphological changes in the river system pre-and post-construction. It is, therefore, necessary to familiarize with the major geomorphic attributes of Brahmaputra river. Notable these are braided planform, bedforms and sediment transport. The erosion and deposition pattern of Brahmaputra river reach nearby Bogibeel bridge is showing a decreasing trend, which corresponds to the good river training work and flood management in that area over the last few years. Riverbed level change analysis indicate that the average change in the riverbed level is -0.20 m. the maximum fall in the bed level was found to be 1.15 m from the year 2010 to 2011. The slope of the deepest channel of the study reach of the river is found to be nearly 0.35 m / Km. In the trend analysis of the riverbed slope, the results reveal that there is a fall in the slope of the overall channel at a rate of 0.01 m / Km per year, i.e. the slopes are getting steeper. This can be due to narrowing of the river near the bridge leading to active degradation of channel. During the field assessment survey, it has observed that due to Bogibeel bridge, the water level and frequency of flood is increase in u/s (within 6 Km) of Bogibeel bridge. The study can be used as a baseline for future studies near the Bogibeel bridge, and similar studies may be carried-out for other constructed or upcoming bridges on Brahmaputra river.

Morphodynamics, River Morphology, Brahmaputra River, Bogibeel Bridge, RS/GIS

[01] Pareta K. 2021. Why Indian largest river island Majuli is shrinking: biophysical and fluvial geomorphological study through historical multi-temporal satellite imageries. American Journal of Geophysics, Geochemistry and Geosystems. Vol. 7 (1), pp. 38-52. [02] Baishya SJ and Sahariah D. 2015. A study of bank erosion and bankline migration of the Baralia river, Assam, using remote sensing and GIS. International Journal of Current Research. Vol. 7 (11), pp. 373-380. [03] Aher S, Bairagi S, Deshmukh P and Gaikwad R. 2014. River change detection and bank erosion identification using topographical and remote sensing data. International Journal of Applied Information Systems. Vol. 2 (3), pp. 1-7. [04] Alam JB, Uddin M, Ahmed UJ, Cacovean H, Rahman HM, Banik BK and Yesmin N. 2007. Study of morphological change of river old Brahmaputra and its social impacts by remote sensing. Geographia Technica. Vol. 4 (2). pp. 1-11. [05] Lawler DM, Couperthwaite J, Bull LJ and Harris NM. 1997. Bank erosion events and processes in the upper Severn basin. Hydrology and Earth System Sciences Discussions, Copernicus Publications. Vol. 1 (3), pp. 523-534. [06] Yang X, Damen MCJ and Zuidam RAV. 1999. Satellite remote sensing and GIS for the analysis of channel migration changes in the active Yellow river delta, China. International Journal of Applied Earth Observation and Geoinformation. Vol. 1 (2), pp. 146-157. [07] Sarma JN. 2004. An overview of the Brahmaputra river system. In: Singh VP, Sharma B, Shekhar C and Ojha P. (Eds.), the Brahmaputra Basin Water Resources. Kluwer Academic Publishers. pp. 72-87. [08] Sarma JN. 2005. Fluvial process and morphology of the Brahmaputra river in Assam, India. Geomorphology. Vol. 70, pp. 226-256. [09] Sarma JN and Phukan MK. 2006. Bank erosion and bankline migration of Brahmaputra river in Assam during the twentieth century. Journal of the Geological Society of India. Vol. 68, pp. 1023-1036. [10] Sarma JN, Borah D and Goswami U. 2007. Change of river channel and bank erosion of the Burhi Dihing river (Assam) assessed using remote sensing data and GIS. Journal of the Indian Society of Remote Sensing. Vol. 35, pp. 93-100. [11] Lahiri SK and Sinha R. 2012. Tectonic controls on the morpho-dynamics of the Brahmaputra river system in the upper Assam valley, India. Geomorphology. Vol. 169-170, pp. 74-85. [12] Das AK, Sah RK and Hazarika N. 2012. Bankline change and the facets of riverine hazards in the floodplain of Subansiri-Ranganadi Doab, Brahmaputra Valley, India. Natural Hazards. Vol. 64, pp. 1015-1028. [13] Sarker MH, Thorne CR and Aktar N. 2013. Morpho-dynamics of the Brahmaputra-Jamuna river, Bangladesh. Geomorphology. Vol. 215, pp. 45-59. [14] McLelland SJ, Ashworth PJ, Best JL, Roden JE and Klaassen GJ. 1999. Flow structure and transport of sand-grade suspended sediment around an evolving braid-bar, Jamuna river, Bangladesh. In: Smith ND. (Ed.), Fluvial Sedimentology, International Association of Sedimentologists (Special Publications). Vol. 28, pp. 43-57. [15] Best JL, Ashworth PJ, Bristow CS and Roden J. 2003. Three-dimensional sedimentary architecture of a large, mid-channel sand braid-bar, Jamuna river, Bangladesh. Journal of Sedimentary Research. Vol. 73, pp. 516-530. [16] Gilfellon GB and Sarma JN. 2000. Markov chain analysis as applied to the modern bar-top sediments of the Brahmaputra river. Journal of The Indian Association of Sedimentologists. Vol. 19 (1&2), pp. 107-114. [17] Sarma JN. 2002. A Study on pattern of erosion and bankline migration of the river Brahmaputra in Assam using GIS. Report Disaster Management in North-Eastern region, Dept. of Revenue, Govt. of Assam. pp. 50-53. [18] Gilfellon GB, Sarma JN and Gohain K. 2003. Channel and bed morphology of a part of the Brahmaputra river in Assam, India. Journal of the Geological Society of India. Vol. 62 (2), pp. 227-236. [19] Pareta K. 2020. Riverbank erosion and shifting determined from satellite images. DHI Internal Report prepared under Assam Integrated Flood and Riverbank Erosion Risk Management Investment Program (AIFRERMIP) Scheme for Flood and Riverbank Erosion Management Agency of Assam (FREMAA), 63801442-04. [20] Sarma S and Talukdar BP. 2019. Effect of channel width contraction at Bogibeel bridge site on the morphology of the river Brahmaputra. Bulletin of Pure and Applied Sciences. Vol. 38F (2), pp. 128-140. [21] Sharma N. 2004. Mathematical modelling and braid indicators. In: Singh VP (Ed.) The Brahmaputra river basin water resources. Dordrecht. Kluwer Academic Publishers. Vol. 47, pp. 229-260. [22] Krishnaswami S and Singh S. 2005. Chemical weathering in the river basins of the Himalaya, India. Current Science. Vol. 89 (5), pp. 841-849. [23] FAP24. 1996. Final report, main volume. Water Resources Planning Organisation, Dhaka, Bangladesh.