HR: 0800h
AN: H51E-0813    [Abstracts]
TI: Long-Term Evolution of Meandering Rivers
AU: * Frascati, A
EM: frascati@idra.unipd.it
AF: Dipartimento IMAGE, University of Padova, via Loredan 20, Padova, I-35131, Italy
AU: Lanzoni, S
EM: lanzo@idra.unipd.it
AF: Dipartimento IMAGE, University of Padova, via Loredan 20, Padova, I-35131, Italy
AB: Natural rivers are self-formed features whose shapes are the result of interaction between erosion, deposition and transport of sediments. The study of their morphodynamics and the characterization of related sedimentary processes are of great interest not only to environmental engineers but also to hydrology and historical geology, contributing to the interpretation of stratigraphic records. In the present contribution we focus our attention on the long-term behaviour of meandering rivers, a very common pattern in nature, which belongs to a class of dynamical systems occurring at the spatial scale of the channel width and driven by the coexistence of complex linear and non-linear processes. On the short term time scale, the formation of meandering patterns can be suitably explained as an instability process, driven by bank erosion (bend instability). The planar development of the river is described by a non-linear integro-differential bend evolution equation, complemented with a suitable model for flow and bed topography in sinuous channels with cohesionless bed. On the long-term timescale, a further highly non-linear process must be accounted for, namely channel shortening via cutoff processes. Depending on the description adopted for the flow field, various mathematical models allowing the description of the temporal evolution of the channel axis can be developed. The problem then arise to compare the morphologic characteristics of the planimetric configurations obtained using the different flow field models as well as the differences/analogies between calculated patterns and those observed in the field. The goal of this contribute is to test the prediction capabilities of numerical models simulating the long-term evolution of meandering rivers planform. To this end the morphological characteristics of the planar configurations resulting from different numerical models and those extracted from Landsat mosaic images will be compared through suitable statistical methods. In particular, various morphological variables (e.g channel axis curvature, cartesian wavelength, sinuosity, asymmetry coefficient) will be considered in order to ascertain the ability of synthetical patterns to reproduce the complex morphological features (e.g. compound bend, multi-bend loop) usually observed in nature.
DE: 1815 Erosion
DE: 1825 Geomorphology: fluvial (1625)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Fall Meeting