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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME A: Engineering and Management of Fresh-water Systems : Changes of morphodynamic regime in evolving meandering rivers
Changes of morphodynamic regime in evolving meandering rivers
Author : Rossella Luchi, Guido Zolezzi
Two main regimes characterize the morphodynamics of meandering rivers, with relevant consequences on their planimetric evolution. These regimes are defined by a threshold value of the channel width to depth ratio corresponding to resonance conditions of the linear solution for the flow-bed topography field. Under these sub- and super-resonant conditions morphodynamic influence is dominantly felt down- and upstream respectively, with consequences for channel planform dynamics: meandering patterns accordingly migrate down- and up-valley and meander loops are skewed upand downstream. Whether a meandering river is sub- or super-resonant depends on its reachaveraged characteristics, which slowly vary in time due to the progressive elongation of the channel axis: therefore, morphodynamic regime might be more a dynamical rather than a static concept and possibly change during planimetric evolution. Based on a wide dataset for single-thread, gravel bed rivers, we have explored the possible scenarios originating from the mutual feedback between changes of the reach-averaged hydraulic and geometric characteristics and channel axis deformation. Results indicate the range of parameters where transitions between morphodynamic regimes are more likely to occur; in this respect, the most frequent of these transient behaviors is from the super- to the sub-resonant regime. Careful examination of the temporal changes of the reach-averaged conditions bring an improved insight into the simulated processes, thus providing useful indications in the application of meander simulation models. The present outcomes finally reinforce the need to investigate the effects of flow nonlinearities close to the resonant threshold also to assess the extent to which they might modify the emerging picture.
File Size : 441,872 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME A: Engineering and Management of Fresh-water Systems
Date Published : 01/07/2007
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