| Project/Area Number |
13660147
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
林学
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| Research Institution | Hiroshima University |
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Principal Investigator |
KAIBORI Masahiro Hiroshima University, Faculty of Integrated Arts and Sciences, Associate Professor, 総合科学部, 助教授 (30183776)
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| Co-Investigator(Kenkyū-buntansha) |
HIURA Hiromasa KOCHI UNiVERSITY, Faculty of Agriculture, Professor, 農学部, 教授 (30046495)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2003: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | trees / sediment movement / debris flow disaster / eqiulvalent coefficient of friction / velocity estimation / delay-effect / areal ratio occupied by trees / 侵食 / 流動性 / 流木 / 室内実験 / 遊砂地 / 緩衝作用 / 緩衝樹林帯 / 土石流 / アカマツ混じり二次林 / 堆砂勾配 |
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| Research Abstract |
It is very important that the control effect of trees against sediment movement should be discussed with the correlation between trees and the spatial circumstances, not with the trees characteristics only. Namely, it cannot consider those effects without thinking of the situation of trees in front of residential area and the kinetic energy of sediment movement. We expressed firstly the difference with the equivalent coefficient of friction. We showed that the trees on the debris-flow path could sometimes behave as an assailant of driftwood disaster, and sometimes contribute to disaster prevention as the breaking material against debris flow. Also, we showed that rich trees on the steep slopes could make delay to initiate failures and debris flows. Residual soil could not exist on the steep slopes without rich trees. Then there were a lot of unstable materials on the channel. Formerly, these materials turned easily to debris flows, however, the tendency decreases with trees growth nowadays. We showed that the areal ratio of trees was more effective than the number density of trees on the discussion of those effects against sediment movement. And we indicated that those effects could be mobilized over some per mil in the areal ratio occupied by trees. We showed the calculation method for the velocity estimation of debris flows, which was very important to discuss the strength of trees against external forces. Estimated velocities agreed with the result of field investigation. We can conclude that this estimation can be utilized to evaluate the control effect of trees against sediment movement.
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