1990 Fiscal Year Final Research Report Summary
Study on the Relationship Between the Fractal Characteristics of Rill Patterns on the Soil Surface and the Rate of Run-off Sediment
| Project/Area Number |
63460214
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
農業土木
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| Research Institution | Yamaguchi University |
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Principal Investigator |
FUJIWARA Teruo Yamaguchi University, Faculty of Engineering, Professor, 工学部, 教授 (40035019)
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| Co-Investigator(Kenkyū-buntansha) |
FUKADA Mitsuo Yamaguchi University, Faculty of Agriculture, Assistant, 農学部, 助手 (20116750)
HISAI Mamoru Yamaguchi University, Faculty of Engineering, Assistant Professor, 工学部, 助教授 (80110237)
TAKUMA Katsutoshi Tottori University, Faculty of Agriculture, Assistant Professor, 農学部, 教授 (40032297)
KUSAKA Tatsuro Yamaguchi University, Faculty of Agriculture, Professor, 農学部, 教授 (50038238)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Soil Erosion / Rill / Simulation / Fractal Dimension / Fourier Analysis / Power Spectrum / Entropy |
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| Research Abstract |
It is not too much to say that the best method to prevent soil erosion is to control the occurrence and the development of rill networks on the soil surface. Realizing this point, the purpose of this study is to investigate the relationship between the rill patterns and soil run-off, and, if possible, to know the method to estimate the soil loss from the rills.
As rill networks have a irregular and complex patterns, it is difficult to express the patterns numerically by the classic geometrical concepts. In this study, the relationship between the soil loss and fractal dimensions of rill patterns was discussed by using the new concept of fractal geometrics i. e. fractal dimensions.
First, we observed photograhically rill networks that develop on the bare slopes, and confirmed that they have a properties of fractal. And the relation between the fractal dimensions and entropy which can be obtained from power spectrum was discussed. On the other hand, the seasonable change of configuration of soil surface and the soil run-off have been also observed over three years on the test plots.
Experiments were carried out by supplying artificial rainfall on the slope. In this experiment, the time variations of soil run-off were measured, and the relationship between the fractal dimensions of rill patterns and soil loss was discussed.
The fractal dimensions of rill patterns that develop on-the-spot slopes which was composed of the four different soil were obtained. These soil are decomposite granite soil "Masado", "Kuroboku", weathered tuff and volcanic cohesive soil.
The process of formation of rill patterns was simulated with the aid of a random pattern model, which is used in the fields of fractal geometry. As a results of the simulation, the simulated patterns were very similar to the rill patterns that develop on-the-spot slopes.
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