Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Part I Background
- Part II Upstream controls
- Chapter 4 History
- Chapter 5 Tectonics and relief
- Chapter 6 Lithology
- Chapter 7 Climate: hydrology
- Chapter 8 Humans
- Part III Fixed local controls
- Part IV Variable local controls
- Part V Downstream controls
- Part VI Rivers and humans
- References
- Index
Chapter 4 - History
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Part I Background
- Part II Upstream controls
- Chapter 4 History
- Chapter 5 Tectonics and relief
- Chapter 6 Lithology
- Chapter 7 Climate: hydrology
- Chapter 8 Humans
- Part III Fixed local controls
- Part IV Variable local controls
- Part V Downstream controls
- Part VI Rivers and humans
- References
- Index
Summary
It may be difficult to view history as an upstream control (Figure 1.2, but changing relief, and climate through time, should have the greatest effect on upstream high relief areas, thereby increasing the impact downstream, as the delivery of water and sediment from upstream causes a downstream channel response.
The Davis cycle of landscape change through time, which is based upon the assumption of rapid uplift and then tectonic stability, can be used to explain the variability of rivers in the context of geomorphic history. Assume an uplifted block with a well-defined drainage divide and base level, and flowing water that will initiate channel incision (Figure 4.1). One can envision a large river incising down the right side of the block with the tributary incising to keep pace. The longitudinal profile of the tributary will change (Figure 4.1), with regime developing only at about stage 7 and extending upstream at stages 8 and 9 (Schumm, 1956; Whipple et al., 2000.
The hypothetical cross-sections in Figure 4.2 reveal how the valley develops through time, and they also show how, with each increment of incision, the valley walls provide a significant yield of sediment to the channel, which probably is subjected to alternate periods of aggradation and degradation.
During stages 1–4 the channel is confined by bedrock valley walls. During stages 5–7 the channel is constrained by bedrock valley walls and terraces of older alluvium. During stages 8 and 9 the channels are in regime.
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- Information
- River Variability and Complexity , pp. 39 - 49Publisher: Cambridge University PressPrint publication year: 2005