World Library  


Add to Book Shelf
Flag as Inappropriate
Email this Book

A Theoretical Analysis of River Bars Stability Under Changing Channel Width : Volume 39, Issue 39 (01/04/2014)

By Zen, S.

Click here to view

Book Id: WPLBN0003979755
Format Type: PDF Article :
File Size: Pages 9
Reproduction Date: 2015

Title: A Theoretical Analysis of River Bars Stability Under Changing Channel Width : Volume 39, Issue 39 (01/04/2014)  
Author: Zen, S.
Volume: Vol. 39, Issue 39
Language: English
Subject: Science, Advances, Geosciences
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2014
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

Citation

APA MLA Chicago

Tubino, M., Zolezzi, G., & Zen, S. (2014). A Theoretical Analysis of River Bars Stability Under Changing Channel Width : Volume 39, Issue 39 (01/04/2014). Retrieved from http://www.ebooklibrary.org/


Description
Description: Department of Civil, Environmental and Mechanical Engineering, via Mesiano 77, 38123, Trento, Italy. In this paper we propose a new theoretical model to investigate the influence of temporal changes in channel width on river bar stability. This is achieved by performing a nonlinear stability analysis, which includes temporal width variations as a small-amplitude perturbation of the basic flow. In order to quantify width variability, channel width is related with the instantaneous discharge using existing empirical formulae proposed for channels with cohesionless banks. Therefore, width can vary (increase and/or decrease) either because it adapts to the temporally varying discharge or, if discharge is constant, through a relaxation relation describing widening of an initially overnarrow channel towards the equilibrium width. Unsteadiness related with changes in channel width is found to directly affect the instantaneous bar growth rate, depending on the conditions under which the widening process occurs. The governing mathematical system is solved by means of a two-parameters (Ε, Δ) perturbation expansion, where Ε is related to bar amplitude and δ to the temporal width variability. In general width unsteadiness is predicted to play a destabilizing role on free bar stability, namely during the peak stage of a flood event in a laterally unconfined channel and invariably for overnarrow channels fed with steady discharge. In this latter case, width unsteadiness tends to shorten the most unstable bar wavelength compared to the case with constant width, in qualitative agreement with existing experimental observations.

Summary
A theoretical analysis of river bars stability under changing channel width

Excerpt
Ashmore, P.: How do gravel-bed rivers braid? Can. J. Earth Sci., 28, 326–341, 1991.; Ashmore, P.: Laboratory modelling of gravel braided stream morphology. Earth Surf. Process. Land., 7, 201–225, 1982.; Bertoldi, W. and Tubino, M.: Bed and bank evolution of bifurcating channels, Water Resour. Res., 41, W07001, doi:10.1029/2004WR003333, 2005.; Church, M. and Rice, S. P.: Form and growth of bars in a wandering gravel-bed river, Earth Surf. Process. Land., 34, 1422–1432, 2009.; Colombini, M., Seminara, G., and Tubino, M.: Finite-amplitude alternate bars, J. Fluid Mech., 181, 213–232, 1987.; Crosato, A. and Mosselman, E.: Simple physics-based predictor for the number of river bars and the transition between meandering and braiding. Water Resour. Res., 45, W03424, doi:10.1029/2008WR007242, 2009.; Hall, P.: Alternating bar instabilities in unsteady channel flows over erodible beds, J. Fluid Mech., 499, 49–73, doi:10.1017/S0022112003006219, 2004.; Lewin, J.: Initiation of bed forms and meanders in coarse grained sediment. Geolog. Soc. Am. Bull., 87, 281–285, 1976.; Parker, G.: On the cause and characteristic scales of meandering and braiding in rivers, J. Fluid Mech., 76, 457–479, doi:10.1017/S0022112076000748, 1976.; Parker, G., Shimizu, Y., Wilkerson, G. V., Eke, E. C., Abad, J.D., Lauer, J. W., Paola, C., Dietrich, W. E., and Voller, V. R.: A new framework for modeling the migration of meandering rivers. Earth Surf. Process. Land., 36, 70–86, doi:10.1002/esp.2113, 2011.; Parker, G., Wilcock, P. R., Paola, C., Dietrich, W. E., and Pitlick, J.: Physical basis for quasi-universal relations describing bankfull hydraulic geometry of single-thread gravel bed rivers, J. Geophys. Res., 112, F04005, doi:10.1029/2006JF000549, 2007.; Repetto, R., Tubino, M., and Paola, C.: Planimetric instability of channels with variable width, J. Fluid Mech., 457, 79–109, 2002.; Surian, N. and Rinaldi, M.: Morphological response to river engineering and management in alluvial channels in italy, Geomorphology, 50, 307–326, 2003.; Tubino, M.: Growth of alternate bars in unsteady flow, Water Resour. Res., 27, 37–52, 1991.; Visconti, F., Camporeale, C., and Ridolfi, L.: Role of discharge variability on pseudomeandering channel morphodynamics: Results from laboratory experiments, J. Geophys. Res., 115, F04042, doi:10.1029/2010JF001742, 2010.; Welford, M.: A field-test of Tubino's (1991) model of alternate bar formation, Earth Surf. Process. Land., 19, 287–297, doi:10.1002/esp.3290190402, 1994.; Zolezzi, G., Bertoldi, W., and Tubino, M.: Morphodynamics of bars in gravel-bed rivers: Bridging analytical models and field observations, in Gravel-bed Rivers: Processes, Tools, Environments, edited by Church, M., Biron, P. M., and Roy, A., Chap. 6, 69–89, John Wiley & Sons, Chichester, UK, 2012.

 

Click To View

Additional Books


  • The Critical Role of Volcano Monitoring ... (by )
  • Study of 11 September 2004 Hailstorm Eve... (by )
  • Time Variability of Cyclonic Geostrophic... (by )
  • The Verification of Seasonal Precipitati... (by )
  • Large Scale Integrated Hydrological Mode... (by )
  • Synoptic-mesoscale Analysis and Numerica... (by )
  • A Cloud-to-ground Lightning Climatology ... (by )
  • An Observational and Numerical Case Stud... (by )
  • Mtg: Resolution Enhancement for Mw Measu... (by )
  • Studying the Extremes: Hydrometeorologic... (by )
  • Integration by Identification of Indicat... (by )
  • Tracer Dispersion in Bedload Transport :... (by )
Scroll Left
Scroll Right

 



Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.