Читать книгу Introducing Large Rivers - Avijit Gupta - Страница 10
ОглавлениеPreface
An edited anthology on geomorphology and management of large rivers was published in 2007.1 The book filled a gap in our knowledge about large rivers as fluvial geomorphology used to be based more on smaller streams of manageable dimensions. We needed to extend our study to big rivers which shape a significant part of the global physiography, carry a high volume of water and sediment to the coastal waters, and support a very large number of people who live on their floodplains and deltas. That was an advanced treatise. This volume is written primarily as a textbook on large rivers, introducing such aspects. A number of line drawings and photographs illustrate the text, and a set of questions at the end of the chapters encourage the reader to explore various issues regarding large rivers.
The book introduces the environmental characteristics of river basins and forms and functions of channels commonly seen among the large rivers of the world. Specific discussions cover their complex geology, water, and sediment. The great lengths of these rivers stretch across a range of different environments. The Mekong, for example, flows on both rock and alluvium with varying form and behaviour. The geological framework of a large river is based primarily on large-scale tectonics commonly derived by plate movements. An uplifted zone, the primary source of sediment in the river, and a nearly subcontinental-scale water catchment area are necessary. A range of morphology exists in large rivers, and the associated floodplains and flood pulses are ecologically important. Large rivers could be geologically long-lived. In future, their forms may change and their functions may alter, following construction of engineering structures and climate change.
The quality of the book has been enhanced by detailed and well-illustrated discussions on two important topics: (i) large rivers and their floodplains: structures, functions, evolutionary traits and management with special reference to the Brazilian rivers by W.J. Junk et al. (Chapter 5), and (ii) large arctic rivers by O. Slaymaker (Chapter 11). I am grateful to all of the authors of these two chapters for their in-depth discussion on these topics. Lastly, the book indicates that the existing rivers possibly are undergoing dynamic adjustments in a world with a changing climate. Rivers change with time, and we usually know a large river only at a particular point in its existence.
Completion of the book has been a demanding task and I am grateful to the editorial and production teams of John Wiley & Sons, Ltd for their remarkable patience, editorial assistance, and continuous encouragement. I would like to thank Athira Menon and Joseph Vimali for guiding me through the intricacies of book production. Lee Li Kheng has produced many of the diagrams from my rough sketches. I have tremendously benefited from the critical readings by Colin Murray-Wallace of Chapter 7 on past rivers and by Colin Woodroffe of Chapter 6 on large river deltas and a discussion on climate change with John Morrison.
Wollongong, Australia, June 2019
Avijit Gupta
