Effects of bed topography and vegetation on 3D flow patterns in low-gradient rivers

RODRÍGUEZ, J. F.; GARCÍA M.H.; LÓPEZ, F. M.; GARCÍA, C.M.

Brisbane, Australia

Conferencia; ICHE 2004, Sixth International Conference on Hydro-Science and Engineering; 2004

A set of laboratory experiments was carried out to investigate how the 3D flow structure andturbulence characteristics of open channel flow are affected by bed topography and vegetation. The topographic pattern selected for the uneven bed was a sequence of pools and riffles, a common bedform observed in low-gradient rivers. Both centred and alternated pools were simulated. Flexible vegetation placed in a hypothetical seasonal flooding zone was later added to the alternate pool configuration. Each configuration included low and high flow experiments.The spatial analysis of the velocity vectors showed that bed topography plays an importantrole for low flow conditions. For high flow, the flow patterns are almost independent of the shape of the bed. The effects of bed topography are less apparent in the experiments with vegetation. Both low and high flow patterns showed similar behavior, dominated by the spatial distribution of the plants.