Resistance and Sedimentation by Trees

Abstract

Many sabo facilities utilizing trees in streams or sorting basins are often planned to promote sedimentation. It is expected that trees in stream have a function of sedimentation because trees can be hydraulically regarded as a group of roughness. then the velocity is decreased. Flow resistance and sedimentation by trees were investigated in flume experiments.
Results showed that the coefficient of roughness increases as the percentage of area occupied by trees becomes larger, then the drag coefficient decreases conversely in terms of interference of wakes between trees. Sedimentation is remarkable when the percentage of area occupied by trees is large, and the ratio of the interval between trees to maximum diameter is small. But the volume of sedimentation decreases when the percentage of area occupied by trees is more than 2. 5×10^-2 and the ratio of the interval between trees is less than 1.5.