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

Remote sensing and GIS technologies presently has an essential tool for fluvial morphological studies i.e. historical morpho-dynamics, mean river with, spatio-temporal analysis of erosional / depositional areas, bankline migration analysis as well as geological mapping, geomorphological mapping, gravity changes and groundwater storage changes, and bathymetry analysis. These studies have been performed in an area around Dibru-Saikhowa National Park is a river island in the upper Brahmaputra valley of Assam, India by using multi-temporal, multi-spatial, and multi-spectral Landsat satellite imageries from 1973 to 2021; Geo-technical investigations and sub-soil explorations data of year 2020; Gravity Recovery and Climate Experiment (GRACE) data from 2004 to 2017; and bathymetric survey data of year 2020. River width has been measured at 123 cross-sections of Brahmaputra river and observed that average river width is suddenly change from 13.03 Km in 1996 to 17.53 Km in 1997, when Dibru-Saikhowa National Park become an isolated patch of land forming as river island. The area around Dibru-Saikhowa National Park is highly morpho-dynamics in term of erosion, deposition and bankline migration. The average depositional area from 1973 to 2021 on right bankline and left bankline is 3.23 Km², and 2.90 Km² respectively, while average erosional area from 1973 to 2021 on right bankline and left bankline is 4.70 Km², and 5.79 Km² respectively. The erosion rate and bankline migration rate is higher along the left bank then the right bank. Dibru-Saikhowa river island has a total area of 340.79 Km² in 1998 but having lost significantly to erosion it has an area of 219.60 Km² in 2021. Landsat satellite imageries analysis result (1998-2021) shows that the Dibru-Saikhowa river island is continuously shrinking due to heavy erosion and flooding, and it has lost its area every year, and average rate of land degradation is 5.27 Km² / year. GRACE data are providing a quantity of available gravity and terrestrial water storage changes. The available datasets have been divided into two group 2004-2010, 2011-2017 and analyzed, and observed that the gravity and groundwater storage have been shifted approx. 5 Km from NW to SE direction during the period of 2004-2017. The same pattern has been also observed in the bathymetric data analysis. it has cleared that the maximum depth of water has detected in the mainstream of Brahmaputra river, which is continuously moving from north-west to south-east direction due to gravity change over the study period.

Morphology, Geo-technical, Geomorphology, Gravity Change, Bathymetry, Brahmaputra River

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