impact of single natural vegetation elements on flow characteristics

In this experimental study, measurements were conducted to explore the impacts of different forms of individual natural vegetative elements within the flow domain on velocity and turbulence characteristics. All the experiments were performed in a flume measuring 26 m in length, 0·98 m in width and 0·85 m in depth, and real tree saplings were utilized to represent the vegetation element. In order to analyse this commonly observed nature phenomenon in floodplains, trees with wide trunks were classified into three groups on the basis of their volume versus height relation. Throughout the velocity measurements three acoustic Doppler velocimeters were employed. Time-averaged velocity, streamwise and vertical turbulence intensities and turbulent kinetic energy parameters were examined. Additionally, a formulation that gives the velocity profile at a certain distance downstream of vegetation was introduced and the validity of the proposed formulation was checked with experimental data. It is seen that despite their porous structures, the presence of vegetation considerably disturbs the flow field and dissipates a remarkable amount of energy by turbulence. Copyright © 2008 John Wiley & Sons, Ltd.