Experimental Study on the Impact of Emergent Vegetation on Flow

Vegetation growing in the water along rivers has been the subject of several studies since it was recognized that it could have a significant impact on the water flow. It may increases resistance to flow and causes higher water levels. Also, it has affects on the turbulent structure such as the mean velocity profiles. For flow of water through emergent vegetation, previous investigations show different results. Hence, better knowledge on its impact on flow conditions is needed. The purpose of this paper is to investigate, how density and placement of emergent vegetation influence flow resistance, water depth and velocity profile. Experiments using artificial vegetation selected to simulate emergent vegetation were carried out in a laboratory flume instead of natural channel, and Manning’s n is used to denote the resistance coefficient. The results show large variations in the Manning resistance coefficient with depth of flow and vegetative density. Vegetation causes resistance to flow; it reduces flow velocities and increases water depth. For the vegetation densities considered, the presence of foliage significantly reduces the mean velocities. Also mean velocity profile is set by the vertical structure of the vegetative drag.