Introducing Large Rivers. Avijit GuptaЧитать онлайн книгу.
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
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