A 1D sediment transport model for the Amazone river
Julien
Nicod, INPT,Toulouse, France, nicod@imft.fr
Jean-Pierre
Baume, Cemagref, Montpellier, France, jean-pierre.baume@cemagref.fr
Pascal
Kosuth, Cemagref, Maison de la Teledetection, Montpellier, France Janeiro, Brasil, pascal.kosuth@teledetection.fr
Benoit
Le Guennec, IRD-LMTG, Coppe/UFRJ, Rio de Janeiro, Brasil, benoit@peno.coppe.ufrj.br
(Presenting)
A one-dimensional hydrodynamic model is built for the Amazon river from Manaus to Obidos. Floodable areas, major bed and varzeas, are estimated by fitting the observed and computed flood hydrographs.
Campaigns of measurements were performed at different periods of the hydrologic cycle on Amazon, Madeira, Solimoes and Rio Negro rivers: cross sections, bed levels, hydraulic discharges and velocity profiles with ADCP.
To analyse, understand and quantify the suspended load, solid transport capacities are computed and a loading law is used in the sediment transport model under non equilibrium conditions.
In a first attempt, a model of sediment transport between Manacapuru and Obidos is built using some available in situ measurements. These data come from the HyBAm measurement stations net. Samplings of suspended matter are done every ten days. They are taken just under the free surface and so consider only the finer particles of the suspended load. The needed data for the boundaries conditions are here the suspended load in the three upstream contributors (Rio Negro, Solimoes and Madeira). They are estimated by multiplying the concentrations of suspended matter near the free surface by the mean discharge in the cross section. This first model shows that deposit can occur on some reaches, even for the finest particles. That is due to the high or low water flow regimes and depends on flooded areas contribution which can trap sediments.
In the last years, the solid discharges were also estimated measuring concentration profiles by sampling, along three verticals for each cross section in different reaches of the rivers. Grain size distributions were then obtained in laboratory. These data allow to define the balances and fluxes of the suspended matter with more accuracy, and will be used to calibrate a sediment transport model in order to account for the total suspended load, and to precise the contribution of the flooded areas.
Submetido por Benoit Le Guennec em 17-MAR-2004
Tema Científico do LBA: SH (Hidrologia e Química das Águas)