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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 : Hydraulic modeling of an anabranched river reach: riffle-pool reversal and maintenance mechanism d...
Hydraulic modeling of an anabranched river reach: riffle-pool reversal and maintenance mechanism during a flood event
Author : Nistoran Daniela, Moatar Florentina, Rodrigues Stephane, Philippe Jugé
Hydraulic modeling is used to extend the measured hydrodynamic parameters during a flood event, in order to explain the pool-riffle maintenance mechanism and the grain sorting patterns observed by field investigations performed on an anabranched reach (mainstream and three secondary channels named A-C) of Loire River (at Bréhémont, France). LiDAR topographic data and bathymetric surveys, coupled with hydrologic data for the studied area are used to build two hydraulic models: a 1-D, full-network one (with the help of GeoRAS and HEC-RAS codes), and a two-dimensional, triangular unstructured mesh (with the help of TELEMAC 2D code), based on finite-difference and finite-element numerical techniques, respectively. The two models are calibrated in terms of roughness coefficients on measured values of water surface elevations, discharges and velocities. The analysis of the hydrodynamic parameters for different values of the mainstream discharge was focused on the secondary channel A. Observed important erosion of its right bank in the entry area is explained with the velocity field direction computed by the 2D model. Velocity and shear stress reversal is proved for the pool and riffle sequences along channel A by both hydraulic models and the maintenance mechanism is explained on the base of Shields parameters and the break and subsequent renewal of armour layer.
File Size : 2,918,098 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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