INVESTIGADORES
ORFEO Oscar
capítulos de libros
Título:
Large river channel confluences
Autor/es:
PARSONS, D., BEST, J., LANE, S., KOSTASCHUK, R., HARDY, R., ORFEO, O., AMSLER, M., AND SZUPIANY, R.
Libro:
River Confluences, Tributaries and the Fluvial Network
Editorial:
John Wiley & Sons
Referencias:
Lugar: West Sussex; Año: 2008; p. 73 - 91
Resumen:
River channel confluences are a fundamental component of fluvial systems and are ubiquitous within both dendritic drainage networks and most channel planforms. Despite the clear importance of fully understanding the processes and dynamics of river channel confluences, our current understanding is based largely on laboratory experiments (e.g. Mosley, 1976; Best, 1988; Best and Roy, 1991) and on the observations, measurements and numerical modelling of small-scale natural junctions, which are often less than tens of metres wide (Rhoads and Kenworthy, 1998; Bradbrook et al.,et al., River Confluences, Tributaries and the Fluvial Network Edited by Stephen P. Rice, Andr´e G. Roy and Bruce L. Rhoads C 2008 JohnWiley & Sons, Ltd PIC OTE/SPH PIC OTE/SPH and Bruce L. Rhoads C 2008 JohnWiley & Sons, Ltd PIC OTE/SPH PIC OTE/SPH Edited by Stephen P. Rice, Andr´e G. Roy and Bruce L. Rhoads C 2008 JohnWiley & Sons, Ltd PIC OTE/SPH PIC OTE/SPH C 2008 JohnWiley & Sons, Ltd PIC OTE/SPH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 JWBK179-05 February 26, 2008 17:15 Char Count= 0 74 CH 5 LARGE RIVER CHANNEL CONFLUENCESCH 5 LARGE RIVER CHANNEL CONFLUENCES 1998; Lane et al., 2000; Rhoads and Sukhodolov, 2004). Although investigations of channel junctions have become increasingly sophisticated, allowing for the identification of some of the key variables that control confluencemorphodynamics, this advance has largely focused on small-scale confluences. Until recently, there have been almost no detailed studies of flow, sediment transport and bed morphology at larger scales, and it is reasonable to question whether or not current conceptual models of confluence dynamics are valid for larger rivers (channels ∼>100m wide). This question is significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsons significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsons channel junctions have become increasingly sophisticated, allowing for the identification of some of the key variables that control confluencemorphodynamics, this advance has largely focused on small-scale confluences. Until recently, there have been almost no detailed studies of flow, sediment transport and bed morphology at larger scales, and it is reasonable to question whether or not current conceptual models of confluence dynamics are valid for larger rivers (channels ∼>100m wide). This question is significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsons significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsons et al., 2000; Rhoads and Sukhodolov, 2004). Although investigations of channel junctions have become increasingly sophisticated, allowing for the identification of some of the key variables that control confluencemorphodynamics, this advance has largely focused on small-scale confluences. Until recently, there have been almost no detailed studies of flow, sediment transport and bed morphology at larger scales, and it is reasonable to question whether or not current conceptual models of confluence dynamics are valid for larger rivers (channels ∼>100m wide). This question is significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsons significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsons ∼>100m wide). This question is significant as the junctions of smaller channels can be expected to differ considerably from the junctions of channels several orders of magnitude larger. For example, smaller channels are usually characterized by relatively low channel width–depth ratios, whilst larger channels are usually wider and shallower. Moreover, the junction of two larger channels may drain significantly different areas in terms of geology and climate, and can thus have a greater range of inflow conditions at the confluence as compared to smaller junctions, which more frequently drain areas with similar catchment characteristics. Understanding the influence of such scale effects on the process dynamics of large river confluences is vital since they adopt a pivotal role in controlling, and regulating, the passage of colossal volumes of water and sediment, and determine the delivery and timing of fluid and sediment discharge to downstream coastal zones and oceans. Such influences can thus have a wide range of impacts at both the regional and global scale. Recent developments in technology, and in particular advances in global positioning systems and the advent of acoustic Doppler current profiling and multibeam echo sounding, have begun to facilitate investigations of large river morphodynamics (e.g. Richardson and Thorne, 2001; McLelland et al., 1999; Ashworth et al., 2000; Parsonset al., 1999; Ashworth et al., 2000; Parsons et al., 2004, 2005, 2007; Szupiany et al., 2005; Lane et al., inpress). Thesenewinstruments enable the rapid and precise mapping of flow fields and bed morphology from such large channels, and the initial results from these investigations (e.g. McLelland et al., 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. enable the rapid and precise mapping of flow fields and bed morphology from such large channels, and the initial results from these investigations (e.g. McLelland et al., 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. , 2004, 2005, 2007; Szupiany et al., 2005; Lane et al., inpress). Thesenewinstruments enable the rapid and precise mapping of flow fields and bed morphology from such large channels, and the initial results from these investigations (e.g. McLelland et al., 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. et al., 1999; Parsons et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising. et al., 2007) question whether large-scale secondary flows are present at large river channel confluences and suggest that boundary-layer effects at higherwidth– depth ratios and the impacts of high form roughness might suppress the development of such flow structures. This chapter will examine the influence of scale on junction morphodynamics and highlight the similarities and differences between large and small confluences. The flow structure present at larger river confluences will be compared with models developed for smaller junctions, allowing discussion and speculation on the influence of these processes on the dynamics of fluid mixing at large river channel confluences. This chapter presents details from relatively new material, as data on large-scale confluences are only now becoming available, and highlights some of the challenges that such new information is raising.
rds']