Assessing morphological changes of the Ganges River using satellite images

Abstract

Using eight dry season satellite images of Landsat MSS (1973–1984), Landsat TM (1993–2003), and IRS LISS (2009), this study assessed morphological changes of the Ganges River within Bangladesh. As a typical alluvial river, morphological changes of the Ganges River had been a common phenomenon. In the 1973–2009 study period, with its morphologically dynamic nature, the Ganges River had undergone considerable changes in its river banks and its vegetated islands. The bankline movement rates (m/y)and erosion–accretion rates (ha/y) of the river were analyzed under four time periods: 1973–1984, 1984–1993, 1993–2003, and 2003–2009. The results indicate that both the left and the right banks of Ganges have changed significantly due to varying erosion and accretion rates that had occurred. On a whole, the left bank was more prone to accretion while the right bank to erosion. The magnitude of bank erosion along the Ganges River is closely related to the erodibility of riverbank materials which vary spatially. In 1973–1984, the average river width and the overall islands area had decreased considerably due to a net river bank accretion which resulted in an increase of 6790 ha of land area. However, afterwards, both river width and islands area continue to increase to the end of this study period (2009) because of a net erosion (loss of 18,830 ha of land). Furthermore, from 1984 to 2009, the sinuosity of Ganges had generally increased and was related to increased river width caused by a net bank erosion. Compared to other major rivers, Ganges has a very high erosion rate probably because its river banks are primarily composed of highly erodible materials and its high discharge rate especially during the Monsoon season.