Flow structure at the downstream of a one-line riparian emergent tree along the floodplain edge in a compound open-channel flow

Abstract

This study focuses on the effects of one-line emergent natural tree (Cupressus Macrocarpa) planted at the edge of the floodplain in a compound open-channel flow. The flow velocity and water level are measured and used to analyze the flow structure. The time averaged and depth-averaged streamwise velocity distributions with root mean square (rms) and time series of streamwise velocity distrbution are analyzed. The velocity distribution considerably changes along the compound channel. The streamwise velocity distribution fits with logarithmic distribution in the non-vegetated case, but for vegetated cases, the streamwise velocity distribution shows S shaped profile at the 1/3 part of floodplain (B f / 3) and main channel (B m / 3) close to the boundary between floodplain and main channel. Additionally, it is obtained that the presence of tree line increases turbulence intensity over the compound open-channel. Moreover, an oscillation period is obtained in the flow caused by tree line by analyzing time series of the streamwise velocity distribution. The oscillation is present everywhere in the floodplain and present at almost B m / 3 part of the main channel which is close to the junction between floodplain and main channel.