Browsing by Autor "L. Bourrel"

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Temporal relations between meander deformation, water discharge and sediment fluxes in the floodplain of the Rio Beni (Bolivian Amazonia)
(Wiley, 2006) Erwan Gautier; Daniel Brunstein; Philippe Vauchel; M. Roulet; Oscar Fuertes; Jean‐Loup Guyot; J. Darozzes; L. Bourrel
Abstract The Andean Cordillera and piedmont significantly influence river system and dynamics, being the source of many of the important rivers of the Amazon basin. The Beni River, whose upper sub‐catchments drain the Andean and sub‐Andean ranges, is a major tributary of the Madeira River. This study examines the river in the south‐western Amazonian lowlands of Bolivia, where it develops mobile meanders. Channel migration, meander‐bend morphology and ox‐bow lakes are analysed at different temporal and spatial scales. The first part of this study was undertaken with the aim to link the erosion–deposition processes in the active channel with hydrological events. The quantification of annual erosion and deposition areas shows high inter‐annual and spatial variability. In this study, we investigate the conditions of sediment exportation in the river in relation to three hydrological parameters (flood intensity, date of discharge peak and duration of the bank‐full stage level). The second part of this study, focusing on the abandoned meanders, analyses the cutoff processes and the post‐abandonment evolution during 1967–2001. This approach shows the influence of the active channel behaviour on the sediment diffusion and sequestration of the abandoned meanders and allows us to build a first model of the contemporary floodplain evolution. Copyright © 2006 John Wiley & Sons, Ltd.
The dynamics of floods in the Bolivian Amazon Basin
(Wiley, 2009) L. Bourrel; Lloyd Phillips; S. Moreau
Abstract In 1997, a study was initiated by IRD, Bolivia to analyse the dynamics of floods in the Bolivian Amazon, which commonly affect an area of 100 000 to 150 000 km 2 for about 4 months of the year. This region is characterized by vast isolated areas with difficult access and is continuously covered by clouds in the wet season. For these reasons, this hydrological study depends heavily on the use of remote sensing, and particularly radar data, for flood monitoring and the identification of areas at risk of inundation. This article presents preliminary results obtained in the Trinidad area, around the Mamoré River, using LANDSAT, ERS and RADARSAT radar data from dry, wet and flood seasons (collected between 1996 and 1998), and water level and, hydrometeorological data obtained from the upper and lower parts of the Mamoré basin. After characterizing the annual flood cycle within the study area, a TM colour composite (to map the vegetation) and a radar colour composite (multi‐temporal), are used to evaluate the potential contribution of microwave data (RADARSAT and ERS) for mapping the extent of flooding at both the regional (all the flood plain) and the local scale (around the city of Trinidad). Copyright © 2009 John Wiley & Sons, Ltd.