Influence of vegetation on compound-channel turbulent field

Abstract

During floods, rivers generally present a compound section configuration, constituted by a faster flow in the main channel and a slower one in the floodplains. The interaction of these flows has a complex turbulent 3D field composed by large-scale horizontal structures and secondary cells. These turbulent structures are responsible for significant lateral momentum transfer. Most rivers present also vegetation, namely trees along the floodplains edges. The wakes formed in front of the vegetation elements alter the classical compound channel turbulent field. In this paper, rods were placed at the edge of the floodplain of an experimental flume, simulating trees.A 2D LDV was used to measure the velocity field. The velocity distribution is modified by the rods due the formation of wakes. In particular, the 2D flow equations are not applicable and the turbulent scales and dissipation rate acquire a longitudinal variation due to longitudinal vortex propagation. © 2012 Taylor & Francis Group, London.