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WATER RESOURCES RESEARCH, VOL. 44, W05420, doi:10.1029/2006WR005260, 2008

Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France

H. Piégay

UMR 5600, Site ENS-lsh, CNRS, University of Lyon, Lyon, France

C. R. Hupp

U.S. Geological Survey, Reston, Virginia, USA

A. Citterio

UMR 5600, Site ENS-lsh, CNRS, University of Lyon, Lyon, France

S. Dufour

CEREGE, University of Aix-Marseille, Aix-en-Provence, France

B. Moulin

UMR 5600, Site ENS-lsh, CNRS, University of Lyon, Lyon, France

D. E. Walling

Department of Geography, University of Exeter, Exeter, UK

Abstract

Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides ¹³⁷Cs and unsupported ²¹⁰Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a⁻¹ over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and ¹³⁷Cs approaches are cross validated for estimating the sedimentation rate within a channel infill.

Received 20 June 2006; accepted 20 February 2008; published 29 May 2008.

Keywords: floodplain accretion; dendrogeomorphology; radionuclides; channel stability; cut-off channel; floodplain lake.

Index Terms: 1861 Hydrology: Sedimentation (4863); 1820 Hydrology: Floodplain dynamics; 1825 Hydrology: Geomorphology: fluvial (1625).

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Citation: Piégay, H., C. R. Hupp, A. Citterio, S. Dufour, B. Moulin, and D. E. Walling (2008), Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France, Water Resour. Res., 44, W05420, doi:10.1029/2006WR005260.

Copyright 2008 by the American Geophysical Union.