Abstract
One of an important parameter to study water flow in channel is Manning’s coefficient (n). This coefficient is produced not only from material forming the channel, but also due to presence of vegetation in channel. The aim of research is to study the effect of vegetation density and height on Coefficient of Manning in open channel. The study was conducted in open channel with 15.5 m long, 0.5 m wide and 1.0 m high. At the center of 3 m long of channel is planted with Sweet flag (Acorus calamus). The impact of various densities and heights of sweet flag were examined using fixed discharge to measure velocity and slope energy. Coefficient of Manning was obtained using Manning’s equation. Statistical analysis of variance with significance level of 0.05 was adopted to evaluate the effect of variables. The result showed that increasing density and height of Sweet flag make decreasing velocity and increasing Coefficient of Manning to be 0,043-0,064, or 1.40-2.10 times compared to un-vegetated channel (no=0.031). Based on statistical analysis, it is found that Fcalc=15.646 and 16.928 for vegetation density and height respectively, which is larger than FStat=2,603. It can be concluded that density and height of vegetation significantly influence on Coefficient of Manning.
Highlights
One of an important parameter to study water flow in channel is Coefficient of Manning (n)
[7] studied the influence of height variation of vegetation on flow resistance, where the results showed that there was an increase in flow resistance in the channel which was indicated by an increase in the Manning coefficient ranging from 0.01-0.031 due to an increase in plant height
We can conclude that the presence of Sweet flag (Acorus calamus) with different height and density in the channel can influence the mean velocity
Summary
One of an important parameter to study water flow in channel is Coefficient of Manning (n). The study of flow resistance due to the vegetation is very complicated since there are many different kinds and type of plants changing in relation to time of growing, and may be definitely different from one place to another place. These inhomogeneous character of the vegetation in the field make difficulty to figure out the accurate prediction of the channel's roughness in a model of the equation. It is necessary to do further research by including for different treatments and type of vegetation growing in the channel to obtain the more reliable approach in general application of model
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