Vegetation patch effects on flow resistance at channel scale

Jean-Stéphane Bailly (1, 2) , Fabrice Vinatier (2) , Gilles Belaud (3, 4) , David Combemale (2)

1 AgroParisTech
2 UMR LISAH - Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème
3 UMR G-EAU - Gestion de l'Eau, Acteurs, Usages
4 Montpellier SupAgro - Centre international d'études supérieures en sciences agronomiques

Thanks to a specific experimental design in a controlled channel, this paper aimed at quantifying how patches of four different ditches plant species affect integrated flow resistance parameters, the Manning coefficient. These plants, frequently encountered in the farmland ditches and irrigation channels of the south of France, were selected according to a large range of hydrophilic requirements, flexibility and branching complexity related to the plant blockage factor. Eight different spatial patches (regular, random, lateral or central patches) of each plant with crescent or similar plant densities were implanted at the bottom of a controlled channel where the water levels and water velocities were measured for three different discharges in steady and unsteady flow conditions. Resistance parameters (Manning parameters) were then estimated from the total head-loss, or from flow propagation velocity in the channel thanks to inversion of an hydrodynamic model. These experiments allow us to test the significance effect of channel vegetation patches and densities on flow resistance parameters at the reach scale.

Mots clés: channel hydraulics; Manning coefficient; plant

Domaines: Milieux et Changements globaux; Mécanique des fluides [physics.class-ph]

Jean-Stéphane Bailly, Fabrice Vinatier, Gilles Belaud, David Combemale. Vegetation patch effects on flow resistance at channel scale. E-proceedings of the 36th IAHR World Congress, IAHR, Jun 2015, The Hague, Netherlands. pp.1-5. ⟨hal-01349589⟩