Introducing Large Rivers. Avijit Gupta
because of coupling (Harvey 2002). Partial decoupling has been seen between large rivers and their floodplains and between main and subsidiary channels. Coupling is limited in small rivers.
11 Basins of large rivers may include polyzonal sub-basins.
4.6 Conclusion
Large rivers are huge systems that transfer water and sediment from the continents to the oceans. Their nature and behaviour determine the morphology of their drainage basins, which are often subcontinental in size, as the entire drainage network is connected to these massive conduits. Thus large rivers may shape the physiography of the land surface over time.
Their location, morphology and behaviour depend on plate tectonics, regional and local geology, and large-scale climatic systems. Several of these rivers have existed for a long period, and all of them have been affected by the repeated climate and sea level changes in the Quaternary. The majority of large rivers are related to human habitation because of the availability of water, fertile fine-grained sediment, extensive floodplains, and ease of irrigation. Several floodplains and deltas have been anthropologically modified, even impounded, and altered from their natural forms and functions.
The following chapters highlight special cases of the morphology of large rivers, their long association with human civilisation, and their probable adjustments to the changing climate of the future.
Questions
1 What are the principal properties of a large river? What effect do such properties have on the morphology of a large river?
2 What is a megafan? Where are megafans found?
3 Describe the physiography of a megafan.
4 Describe the movement of flood water and sediment in a large river valley.
5 Discuss the morphological complexity of a large river.
6 Large rivers have been described as plural systems by Ashworth and Lewin (2012). Why?
7 Discuss the polyzonal sub-basins which may form part of a large river basin.
References
1 Aalto, R., Maurice-Bourgoin, L., Dunne, T. et al. (2003). Episodic sediment accumulation on Amazonian floodplain influenced by El Niño/ Southern Oscillation. Nature 425: 493–497.
2 Archer, A.W. (2005). Review of Amazonian depositional systems. In: Fluvial Sedimentology VII (eds. M.D. Blum, S.B. Marriott and S. Leclair), 17–39. Blackwell.
3 Ashworth, P.J. and Lewin, J. (2012). How do big rivers come to be different? Earth Science Reviews 114: 84–107.
4 Baker, V.R. and Costa, J.E. (1987). Flood power. In: Catastrophic Flooding (eds. L. Mayer and D. Nash), 1–21. London: Allen and Unwin.
5 Best, J.L., Ashworth, P.J., Bristow, C.S., and Rodin, J. (2003). Three-dimensional sedimentary architecture of a large mid-channel sand braid bar, Jamuna River, Bangladesh. Journal of Sedimentary Research 73: 516–530.
6 Chakraborty, T., Kar, B., Ghosh, P., and Basu, S. (2011). Kosi megafan: historical records, geomorphology and the recent avulsion of the Kosi River. Quaternary International 227: 143–160.
7 Coleman, J.M. (1969). Brahmaputra River: channel processes and sedimentation. Sedimentary Geology 3: 129–239.
8 Das Gupta, S.P. (1984). The Ganga Basin, Part 1. New Delhi: Central Board for the Prevention and Control of Water Pollution.
9 Dietrich, W.E., Day, G., and Parker, G. (1999). The Fly River, Papua New Guinea: inferences about river dynamics, floodplain sedimentation and fate of sediment. In: Varieties of Fluvial Form (eds. A.J. Miller and A. Gupta), 346–376. Wiley: Chichester.
10 Douglas, I. and Guyot, J.L. (2005). Erosion and sediment yield in the humid tropics. In: Forests, Water and People in the Humid Tropics (eds. M. Bonell and L.A. Bruijnzeel), 407–421. Cambridge University Press.
11 Dunne, T., Mertes, L.A.K., Meade, R.H. et al. (1998). Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil. Geological Society of America Bulletin 110: 450–467.
12 Fielding, C.R. (accepted for publication). Sedimentology and stratigraphy of large river deposits: recognition and preservation potential in the rock record. In: Large Rivers: Geomorphology and Management, 2e (ed. A. Gupta). Chichester: Wiley.
13 Franzineli, E. and Igreja, H. (2002). Modern sedimentation in the Negro River, Amazonas State, Brazil. Geomorphology 44: 259–271.
14 Gole, C.V. and Chitale, S.V. (1966). Inland delta-building activity of the Kosi River. Journal of the Hydraulics Division, American Society of Civil Engineers 92 (2): 111–126.
15 Gupta, A. (2005). Rivers of Southeast Asia. In: The Physical Geography of Southeast Asia (ed. A. Gupta), 65–79. Oxford: Oxford University Press.
16 Gupta, A. (2007). Tropical Geomorphology. Cambridge: Cambridge University Press.
17 Gupta, A., Kale, V.S., and Rajaguru, S.N. (1999). The Narmada River, India, through space and time. In: Varieties of Fluvial Form (eds. A.J. Miller and A. Gupta), 113–143. Chichester: Wiley.
18 Guyot, J.L. (1993). Hydrogéochimie des fleuves de l'Amazonie bolivienne: Colllection Etudes et Thèsis. Paris, Editions de l'ORSTROM, 261p. (as listed in Mertes and Dunne, 2007).
19 Harvey, A.M. (2002). Effective timescales for coupling within fluvial systems. Geomorphology 44: 175–201.
20 Johnsson, M.J. and Meade, R.H. (1990). Chemical weathering of fluvial sediments during alluvial storage: the Macuapanim Island point bar, Solimões River, Brazil. Journal of Sedimentary Petrology 60: 827–842.
21 Junk, W.J. (ed.) (1997). The Central Amazon Floodplain: Ecology of a Pulsating System. Berlin: Springer.
22 Knox, J.C. (2007). The Mississippi River system. In: Large Rivers: Geomorphology and Management (ed. A. Gupta), 145–182. Chichester: Wiley.
23 Kuehl, S.A., DeMaster, D.J., and Nittrouer, C.A. (1986). Nature of sediment accumulation on the Amazon continental shelf. Continental Shelf Research 6: 208–225.
24 Latrubesse, E. and Franzinelli, E. (2002). The Holocene alluvial plain of the middle Amazon River, Brazil. Geomorphology 44: 241–257.
25 Leier, A.L., DeCelles, P.G., and Pelletier, J.D. (2005). Mountains, monsoons and megafans. Geology 33: 289–292.
26 Lewin, J. and Ashworth, P.J. (2014). Defining large river channel patterns: alluvial exchange and plurality. Geomorphology 215: 81–98.
27 Meade, R.H. (2007). Transcontinental moving and storage: the Orinoco and Amazon Rivers transfer the Andes to the Atlantic. In: Large Rivers: Geomorphology and Management (ed. A. Gupta), 45–63. Chichester: Wiley.
28 Mertes, L.A.K. and Dunne, T. (2007). Effects of tectonism, climate change, and sea-level change on the form and behaviour of the modern Amazon River and its floodplain. In: Large Rivers: Geomorphology and Management (ed. A. Gupta), 115–144. Chichester: Wiley.
29 Mertes, L.A.K., Dunne, T., and Martinelli, L.A. (1996). Channel-floodplain geomorphology along the Solimões-Amazon River, Brazil. Geological Society of America Bulletin 108: 1088–1107.
30 Milliman, J.D. and Syvitski, J.P.M. (1992). Geomorphic/tectonic control of sediment discharge to the ocean: the importance of small mountainous rivers. Journal of Geology 100: 525–644.
31 Nunn, J.A. and Aires, J.B. (1988). Gravity anomalies and flexure of the lithosphere at the middle Amazon basin, Brazil. Journal of Geophysical Research 83: 415–428.
32 Potter, P.E. (1978). Significance and origin of big rivers. Journal of Geology 86: 13–33.
33 Sarkar, M.H., Thorne, C.R., Aktar, M.N., and Ferdous, M.S. (2014). Morpho-dynamics of the Brahmaputra-Jamuna River, Bangladesh. Geomorphology 115: 45–59.
34 Scatena, F.N. and Gupta, A. (2013). Streams of the montane humid tropics. In: