| Summary: | 碩士 === 國立屏東科技大學 === 土木工程系所 === 98 === This study divides the effective factors of soil erosion on the nature channel into two characteristics, hydraulic and vegetation. Hydraulic factors include flow velocity, flow density, flow viscosity, gravity, depth and cross section area, while vegetation factors include characteristic area of plant, manning resistance coefficient, root density and root length density. The study also deduced six dimensionless parameters by dimensional analysis, to build up the relationship between those parameters and soil erodibility. The experimental data collected from a straight flume with bahia grass on channel bed, which was set up by 3 different planted density and 9 different growing period. The results show that roots are the key parameter to affect soil erosion. Roots strength can protect the sample over 80 percent, while leaves can only protect the top soil about 10 percent. Once root density exceeds 2 g/m³ or root length density exceeds 100 m/m³ the soil with bahia grass can protect soil effectively from flow erosion. With the growing day longer, root’s pulling resistance lift rapidly, and soil erodibility decrease obviously. The result also show that the soil erodibility has a power relationship with physics and dimensionless parameters. Finally, the study established the regression equations between vegetation parameters and soil erodibility in different vegetation conditions.
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