ABSTRACT
Measurements have been carried out to clarify the effects of the tree belts along the edges of roughened floodplains on the flow field. A meandering main channel having 0.87 m width and 0.040 m depth with a wavelength of 3.64 m is located along the center of a straight flume, which is 21.8 m long and 2.2 m wide. Flows in a compound channel with three different vegetation layout are measured at the same flow rate: (i) no tree along the floodplain edges, (ii) trees along the half of the floodplain edges, (iii) trees along all the floodplain edges. Measurement has shown that spiral motions are present in the main channel with/without tree belts and that the regions of high primary velocity is concentrated in the main channel over the depth. The tree belts are found to significantly increase the water level, hence decrease the magnitude of primary velocity over the entire channel while they produce small change in velocity distribution, indicating that the flow pattern in the main channel under high water condition is strongly affected by the geometry of the meandering main channel and not by the tree belts along the floodplain edges.
