MODELLING HYDRAULIC EFFECTS FOR VARIOUS POSITIONS OF VEGETATION PATCHES IN A MEANDERING RIVER

Abstract

Meander dynamics create elegant vegetation patterns on the river floodplain. Vegetation on the floodplain is known as riparian vegetation. This vegetation redistributes flow to the main channel and the water sets up in the river reach. However, generic effects of the position of the vegetation patches are not identified and can have implications for river and floodplain management of meandering systems. This study aims to find the hydrodynamic responses of the positioning of vegetation patches. With depth-averaged hydrological modelling, the hydraulic response is quantified by implementing vegetative patches on the floodplain in an idealized meandering system. The hydrological conditions, the location and the vegetation type determine the blockage factor of flow. Varying the position of the patch sets up the water level several centimetres in the main channel and a reduction of 10’s of percentages of flow velocity on the floodplain. Vegetation closer to the channel redirects more flow through the channel as well as more vegetation patches. Submerged vegetation close to the main channel redistributes less flow compared to larger vegetation stands. Furthermore, flow between the patches seems to interact and further obstruct the flow over the floodplain. River and floodplain managers should take these findings of the effect of the position into account for future planning in river restoration projects and accounting for flood protection.