Hydrodynamique et végétation d'une île de l'Isère

Hydrodynamics and vegetation of an island on Isere River

¹ Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE (INPG, CNRS UMR 5564, IRD, UJF), BP 53X, 38041 Grenoble Cedex
² Laboratoire de Géographie Physique, UMR 6042 CNRS, Maison de la Recherche-Université Blaise Pascal, 4 rue Ledru, 63057 Clermont-Ferrand Cedex 1
³ Laboratoire Hydrosystèmes alpins, UMR Ecologie et Changements Environnementaux, Centre de Biologie Alpine, UJF, BP 53X, 38041 Grenoble
⁴ Société Grenobloise d'Etudes et d'Applications Hydrauliques, SOGREAH, 6 rue de Lorraine, 38130 Echirolles.

Abstract

We modelize the flood over an island in a section of the Isere river (France) to evaluate the hazards of the small trees on the island being uprooted or broken. At small discharge, the island is out of water, but it is under water for discharge greater than 700 m³/s. This section of Isere is 1100 m long from the Brignoud bridge (the bridge is 15 km upstream of Grenoble), and the island is at 250 m of the bridge, near the right bank. With the building of hydroelectric dams upstream on the river, which have significant impacts on frequent floods (f < 10 years), islands are stabilized and so the shrub growing on them. On the studied island, the small willows have now 7 m height and 10 cm of diameter. We use the software Telemac2D to modelize the bidimensional flow and to calculate the forces acting on the trees, for discharges with frequency of 10, 50 and 100 years.