Channel metamorphosis in part of middle Ganga basin,India -A study based on multi-data sets
Interpretation and Results
A sequential and comparative study of the multidate datatopographic maps, aerial photographs and Landsat MSS and TM imagery was carried out . The changes in observed channel location range from about 0.5-30 km. Based on the observations it was inferred, that the river Ganga experienced severalstages of migration generally towards south, to occupy, its present -day course. The Ganga, in the past must have been flowing approximately 20 km north of its present course. The river has shifted in five major stages southwards punctuated by four episodes of relatively rapid changes in course. The shifting due to rapid changes in course may not leave any renant for long distances in the transverse direction. but within each stage the river is found to have possessed a locally oscillating character, as is indicated by numerous oxbow lakes and palaeochannels in the vicinity of each of the major stages (Fig. 5).
Fig.3: Landsat TM image (Date 25 May, 1986) showing abandoned channels (AC), meander scars (MS) and oxbow lakes (OL) around Biswa and Parihara. These features pertain to the Burhi-Gandak River.
Fig.4 Salient palaeofeatures of the Burhi-Gandak river and their corresponding stages.
Similarly, the Burhi-Gandak river which is a major tributary to the river Ganga in this area also shows evidences of migratory nature in the past, in the form of wide-spread oxbow lakes and palaeochannels (Fig.4) It is estimated that the Burhi-Gandak river has also migrated over a distance of about 30 kms from north to south in the recent past. The palaeofeatures of the Burhi-Gandak river indicated three main stages in shifting of this river (Fig.5).
| Stages of shifting of Ganga river |
Stages of shifting of Burhi Gandak river |
i - Stage
ii - Stage
iii - Stage
iv - Stage |
1- Stage
2 - Stage
3 - Stage |
Fig. 5: Various stages of shifting of Ganga and Burhi-Gandak rivers
Thus it is found that an integrated study using various data sets such as aerial photographs, images from satellite sensors, surface and subsurface data have provided extremely valuable information in establishing the migratory trend as well as the metamorphosis of the Ganga and Burhi-Gandak rivers in the area.
Acknowledgements
The authors are grateful to Dr. B.B.S. Singhal, Professor, Department of Earth Sciences, University of Roorkee, for providing many fruitful suggestions, GP would like to thank the CSIR, New Delhi for the financial assistance. Bihar Minor Irrigation Department, Patna provided litholog data and assistance in field work. GP would also express his thanks to the Director, WIHG for granting the permission to present this paper.
References
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