Estimates of flow resistance and eddy viscosity coefficients for 2D modelling on vegetated floodplains

• Published in: Hydrological processes Vol. 18; no. 15; pp. 2907 - 2926
• Main Authors: Vionnet, C. A., Tassi, P. A., Martín Vide, J. P.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 30.10.2004; Wiley
• Subjects: compound channel; Computer Science; Earth sciences; Earth, ocean, space; eddy viscosity; Exact sciences and technology; finite elements; flexible vegetation; floodplain modelling; flow resistance; Hydrology; Hydrology. Hydrogeology; lateral distribution method; Modeling and Simulation; shallow water; Iberian Peninsula; Catalonia Spain; Southern Europe; Barcelona Spain; Spain; Spain, Cataluna, Barcelona, Besos; experimental studies; mathematical models; lateral distribution method; vegetation; digital simulation; shallow water; physical models; eddy viscosity; two-dimensional models; compound channel; rivers; flow resistance; Europe; finite element analysis; turbulence; floodplains; flexible vegetation; viscosity; depth; one-dimensional models; vegetation effects; flumes; floodplain modelling; shallow-water environment; finite elements
• ISSN: 0885-6087; 1099-1085
• DOI: 10.1002/hyp.5596

The problem of quantifying the effects of flexible plants on flow resistance and eddy viscosity by vegetated floodplains is first addressed with a one‐dimensional (1D) approximation based upon the so‐called lateral distribution method. The estimates so obtained are then tested with two‐dimensional (2D) numerical simulations based on the full shallow water equations through the use of the computational code Telemac‐2D. Data obtained on a physical model of the Besòs River (Spain), whose floodplains were covered with plastic ornamental plants to mimic the effect of flexible vegetation, is used for the validation of the numerical results. Additionally, the values of flow resistance estimated numerically with the 1D and 2D simulations are compared with values obtained in a rectangular flume under flow conditions (slope, water depth and artificial lining) similar to those used on the reduced model. It is then established that as more physical mechanisms are included in the mathematical model used to study the problem, the ratio between the floodplain and the main channel flow resistance coefficient increases. The approach demonstrates that whenever enough flow data is available, the lateral distribution method delivers values of flow resistance and eddy viscosity which are highly consistent with 2D numerical modelling. This finding could mean considerable savings in the burdensome task of specifying flow resistance and turbulence dissipation values for 2D modelling of large compound channel systems. Copyright © 2004 John Wiley & Sons, Ltd.