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砂防学会誌，Vol．５５，No．３，p．２１−３２，２００２
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表層崩壊発生予測モデルによる地下水位の再現精度の検討
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Accuracy of a shallow‐landslide prediction model to estimate groundwater table
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論文
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小　杉　賢一朗＊　　水　山　高　久＊　　藤　田　正　治＊＊
Ken'ichirou KOSUGI Takahisa MIZUYAMA Masaharu FUJITA
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Abstract
　Physical models, which combines simplified hydrological processes and a mechanical analysis of slope stability, have been proposed. Although they can be practical tools for predicting shallow‐landslides, model performances were not adequately evaluated in comparison with observed groundwater generation processes. Accuracies and limitations of one of such models were examined by using groundwater levels observed at a forested watershed for ７ years. For the model calculation, whole watershed was divided into rectangular parallelepiped elements. In each time step, water balance in each element and both saturated and unsaturated lateral flow between two adjacent elements were computed. The model assumes a new convex H‐Se relationship, where is the groundwater level and Se is the effective saturation, instead of the previously‐suggested linear H‐Se relationship. Results showed that the model can regenerate peak time and level of groundwater table observed at a main hollow and middle part of a ０‐order valley during heavy storms. Model performances were improved by assuming the convex H‐Se relationship instead of the linear H‐Se relationship. However, the model did not succeed in estimating groundwater dynamics measured at the lowest part of the ０‐order valley, and the computed safety factor at the main hollow often suggested occurrences of landslides although no landslide was actually happened. These contradictions were attributable to the difference between the digital topography used for model calculations and the actual topography. Observed groundwater tables around the outlet of the watershed occasionally exhibited long‐lasting recession tails, and the model could not explain such dynamics of groundwater.
Key words：physical model, shallow‐landslide, groundwater, forested watershed, safety factor
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砂防学会誌　Vol．５５　No．３（２４２）September　２００２
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