学会誌「自然災害科学」

土石流の危険度評価・発生予測手法の提案とその適用性の検討

Risk Assessment and Prediction of Debris Flow Occurrence

棚橋 由彦*

Yoshihiko TANABASHI*

Abstract

The complex mechanism of debris flow and the paucity of relevant data for its analysis have so far left us without any practical means for risk assessment and predicting its occurrence. This paper describes a development of synthetic and probabilistic risk assessments of debris flow by integrating two assessments from mechanical and statistical points of view. This paper also describes a study that utilizes available records and data on the 1982 Nagasaki localized heavy rainfall disaster in Japan as well as geographical and geological information of the city area, and aims at developing some practical means for predicting debris flow occurrence. Three approaches are therefore elaborated for the assessment; the first one based on a mechanical model of debris flow, the second one based on the quantification theory in order to take into consideration relevant environmental (and sometimes qualitative) information, and the third one that combines these two approaches.

The second one is a statistical risk assessment of debris flow which can be applied to any area where has its past history of debris flow occurrence by using the quantification method III taking the each item's weight (potential of vulnerability) for debris flow occurrence which can be calculated as the value of each item's range by applying the quantification method II to the same area.

The practice of these risk assessment methods with the records and data of the incident has demonstrated their usefulness.

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