Hostname: page-component-586b7cd67f-g8jcs Total loading time: 0 Render date: 2024-11-25T07:59:15.306Z Has data issue: false hasContentIssue false
  • English
  • Français

Free instability of channel bifurcations and morphodynamic influence

Published online by Cambridge University Press:  28 June 2016

M. Redolfi ,
G. Zolezzi  and
M. Tubino
M. Redolfi*
Affiliation:
Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy
G. Zolezzi
Affiliation:
Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy
M. Tubino
Affiliation:
Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy
*
†Email address for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Channel bifurcations are a fundamental element of a broad variety of flowing freshwater environments worldwide, such as braiding and anabranching rivers, river deltas and alluvial fans. River bifurcations often develop asymmetrical configurations with uneven discharge partition and a bed elevation gap between the downstream anabranches. This has been reproduced by one-dimensional (1-D) analytical theories which, however, rely on the empirical calibration of one or more parameters and cannot provide a clear and detailed physical explanation of the observed dynamics. We propose a novel two-dimensional (2-D) solution for the flow and bed topography in channel bifurcations based on an innovative application to a multi-thread channel configuration of the 2-D steady linear solution developed decades ago to study river bars and meandering in single thread river settings. The resonant value of the upstream channel aspect ratio, corresponding to the theoretical resonance condition of regular river meanders (Blondeaux & Seminara, J. Fluid Mech., vol. 157, 1985, pp. 449–470) is the key parameter discriminating between symmetrical and asymmetrical bifurcations, in quantitative agreement with experimental observations and numerical simulations, and qualitatively matching field observations. Only when the aspect ratio of the upstream channel of the bifurcation exceeds resonance, is the bifurcation node able to trigger the upstream development of a steady alternate bar pattern, thus creating an unbalanced configuration. Ultimately, the work provides an analytical explanation of the intrinsic legacy between bifurcation asymmetry and the phenomenon of 2-D upstream morphodynamic influence discovered by Zolezzi & Seminara (J. Fluid Mech., vol. 438, 2001, pp. 183–211).

JFM classification

Instability: Instability Geophysical and Geological Flows: River dynamics Geophysical and Geological Flows: Sediment transport
Type
Papers
Information
Journal of Fluid Mechanics , Volume 799 , 25 July 2016 , pp. 476 - 504
Check for updates
Copyright
© 2016 Cambridge University Press 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bertoldi, W. 2012 Life of a bifurcation in a gravel-bed braided river. Earth Surf. Process. Landf. 37, 1327–1336.Google Scholar
Bertoldi, W. & Tubino, M. 2005 Bed and bank evolution of bifurcating channels. Water Resour. Res. 41, W07001.CrossRefGoogle Scholar
Bertoldi, W. & Tubino, M. 2007 River bifurcations: experimental observations on equilibrium configurations. Water Resour. Res. 43, W10437.Google Scholar
Bertoldi, W., Zanoni, L., Miori, S., Repetto, R. & Tubino, M. 2009 Interaction between migrating bars and bifurcations in gravel bed rivers. Water Resour. Res. 45, W06418.Google Scholar
Blondeaux, P. & Seminara, G. 1985 A unified bar-bend theory of river meanders. J. Fluid Mech. 157, 449–470.Google Scholar
Bolla Pittaluga, M., Coco, G. & Kleinhans, M. G. 2015 A unified framework for stability of channel bifurcations in gravel and sand fluvial systems. Geophys. Res. Lett. 42 (18), 7521–7536.Google Scholar
Bolla Pittaluga, M., Repetto, R. & Tubino, M. 2003 Channel bifurcation in braided rivers: equilibrium configurations and stability. Water Resour. Res. 39 (3), 1046.Google Scholar
Burge, L. M. 2006 Stability, morphology and surface grain size patterns of channel bifurcation in gravel-cobble bedded anabranching rivers. Earth Surf. Process. Landf. 31, 1211–1226.Google Scholar
Edmonds, D. A. & Slingerland, R. L. 2008 Stability of delta distributary networks and their bifurcations. Water Resour. Res. 44, W09426.Google Scholar
Einstein, H. A.1950 The bed-load function for sediment transportation in open channel flow. Tech. Bulletin No. 1026.Google Scholar
Engelund, F. & Fredsoe, J. 1982 Sediment ripples and dunes. Annu. Rev. Fluid Mech. 14, 13–37.Google Scholar
Federici, B. & Paola, C. 2003 Dynamics of channel bifurcations in noncohesive sediments. Water Resour. Res. 39 (6), 1162.Google Scholar
Ferguson, R. I., Ashmore, P. E., Ashworth, P. J., Paola, C. & Prestegaard, K. L. 1992 Measurements in a Braided river chute and lobe. 1: flow pattern, sediment transport and channel change. Water Resour. Res. 28 (7), 1877–1886.Google Scholar
Frascati, A. & Lanzoni, S. 2009 Morphodynamic regime and long-term evolution of meandering rivers. J. Geophys. Res. 114, F02002.Google Scholar
Hardy, R. J., Lane, S. N. & Yu, D. 2011 Flow structures at an idealized bifurcation: a numerical experiment. Earth Surf. Process. Landf. 36, 2083–2096.Google Scholar
Ikeda, S., Parker, G. & Sawai, K. 1982 Incipient motion of sand particles on side slopes. J. Hydraul. Div. ASCE 108 (1), 95–114.Google Scholar
Kleinhans, M. G., Cohen, K. M., Hoekstra, J. & Ijmker, J. M. 2011 Evolution of a bifurcation in a meandering river with adjustable channel widths, Rhine delta apex, The Netherlands. Earth Surf. Process. Landf. 36, 2011–2027.Google Scholar
Kleinhans, M. G., Ferguson, R. I., Lane, S. N. & Hardy, R. J. 2013 Splitting rivers at their seams: bifurcations and avulsion. Earth Surf. Process. Landf. 38, 47–61.Google Scholar
Kleinhans, M. G., Jagers, H. R. A., Mosselman, E. & Sloff, C. J. 2008 Bifurcation dynamics and avulsion duration in meandering rivers by one-dimensional and three-dimensional models. Water Resour. Res. 44, W08454.Google Scholar
Lanzoni, S. & Seminara, G. 2006 On the nature of meander instability. J. Geophys. Res. 111, F04006.Google Scholar
van der Mark, C. F. & Mosselman, E. 2013 Effects of helical flow in one-dimensional modelling of sediment distribution at river bifurcations. Earth Surf. Process. Landf. 38, 502–511.CrossRefGoogle Scholar
Marra, W. A., Parsons, D. R., Kleinhans, M. G., Keevil, G. M. & Thomas, R. E. 2014 Near-bed and surface flow division patterns in experimental river bifurcations. Water Resour. Res. 50, 1506–1530.Google Scholar
van der Meer, C., Mosselman, E., Sloff, K., Jager, B., Zolezzi, G. & Tubino, M. 2011 Numerical simulations of upstream and downstream overdeepening. In Proceedings of the 7th Symposium of River, Coastal and Estuarine Morphodynamics, Beijing, China, pp. 1721–1729.Google Scholar
Miori, S., Repetto, R. & Tubino, M. 2006 A one-dimensional model of bifurcations in gravel bed channels with erodible banks. Water Resour. Res. 42, W11413.Google Scholar
Mosley, M. P. 1983 Response of braided rivers to changing discharge. J. Hydrol. New Zealand 22 (1), 18–67.Google Scholar
Mosselman, E., Tubino, M. & Zolezzi, G. 2006 The overdeepening theory in river morphodynamics: two decades of shifting interpretations. In Proceedings of River Flow 2006 Conference, London, UK, pp. 1175–1181.Google Scholar
Parker, G. 1990 Surface-based bedload transport relation for gravel rivers. J. Hydraul. Res. 28, 417–436.Google Scholar
Redolfi, M.2014 Sediment transport and morphology of braided rivers: steady and unsteady regime. PhD thesis, University of Trento, Queen Mary University of London.Google Scholar
Seminara, G. & Tubino, M. 1989 Alternate bars and meandering: Free, forced and mixed interactions. In River Meandering (ed. Ikeda, S. & Parker, G.), vol. 12, pp. 267–320. AGU Water Resources Monograph.Google Scholar
Seminara, G. & Tubino, M. 1992 Weakly nonlinear theory for regular meanders. J. Fluid Mech. 244, 257–288.Google Scholar
Seminara, G., Zolezzi, G., Tubino, M. & Zardi, D. 2001 Downstream and upstream influence in river meandering. Part 2. Planimetric development. J. Fluid Mech. 438, 213–230.CrossRefGoogle Scholar
Siviglia, A., Stecca, G., Vanzo, D., Zolezzi, G., Toro, E. F. & Tubino, M. 2013 Numerical modelling of two-dimensional morphodynamics with applications to river bars and bifurcations. Adv. Water Resour. 52, 243–260.CrossRefGoogle Scholar
Struiksma, N. & Crosato, A. 1989 Analysis of a 2-D bed topography model for rivers. In River Meandering (ed. Ikeda, S. & Parker, G.), vol. 12, pp. 153–180. AGU Water Resources Monograph.CrossRefGoogle Scholar
Struiksma, N., Olesen, K. W., Flokstra, C. & de Vriend, J. H. 1985 Bed deformation in curved alluvial channels. J. Hydraul. Res. 23 (1), 57–79.Google Scholar
Talmon, A. M., Van Mierlo, M. C. L. M. & Struiskma, N. 1995 Laboratory measurements of direction of sediment transport on transverse alluvial-bed slopes. J. Hydraul. Res. 33 (4), 495–517.Google Scholar
Thomas, R. E., Parsons, D. R., Sandbach, S. D., Keevil, G. M., Marra, W. A., Hardy, R. J., Best, J. L., Lane, S. N. & Ross, J. A. 2011 An experimental study of discharge partitioning and flow structure at symmetrical bifurcations. Earth Surf. Process. Landf. 36, 2069–2082.Google Scholar
Wang, M. G., Fokkink, R. J. & de Vries, M. 1995 Stability of river bifurcations in 1D morphodynamics models. J. Hydraul. Res. 33 (6), 739–750.Google Scholar
Zolezzi, G., Bertoldi, W. & Tubino, M. 2006 Morphological analysis and prediction of channel bifurcations. In Braided Rivers: Process, Deposits, Ecology and Management. Special Publication (ed. Best, G. H., Bristow, J. L & Petts, C. S.), vol. 36, pp. 227–250. Blackwell.Google Scholar
Zolezzi, G., Guala, M., Termini, D. & Seminara, G. 2005 Experimental observations of upstream overdeepening. J. Fluid Mech. 531, 191–219.Google Scholar
Zolezzi, G., Luchi, R. & Tubino, M. 2009 Morphodynamic regime of gravel bed, single-thread meandering rivers. J. Geophys. Res. 114, F01005.Google Scholar
Zolezzi, G. & Seminara, G. 2001 Downstream and upstream influence in river meandering. Part 1. General theory and application to overdeepening. J. Fluid Mech. 438, 183–211.CrossRefGoogle Scholar