Abstract:

It has become increasingly important in recent years to study the effects of vegetation fields on the fluvial areas which are very important for the ecosystem.  The water plant fields can be classified as submerged, emergent and suspended vegetation.  The major difference of the suspended vegetation is the effect of the bottom boundary layer under the plant.  Suspended vegetation is obstacle and will cause a decrease in speed of the flow and the vertical velocity distribution will deviate from the classical logarithmic distribution.  Contrary the decrease in speed in the upper layer due to the plant, the speed increase will ocur in the gap beneath the plant.  In this research, 181 rigid cylinders with a diameter of 1.0cm were fixed to a 30cm diameter wooden head and mounted on the upper side of the channel.  The plant was allowed to enter into 15cm of water and there is a 15cm gap beneath the plant, between the channel bed and the plant end.  An ADV (Acoustic Doppler Velocitymeter) was used to collect data from 11 different points (4 points before the plant and 7 points after the plant) and 8 different depths.  Experimental results have shown that the suspended vegetation is a barrier to flow and affects the the velocity of the flow.

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