Relation between number of slope failures and degree of heavy rainfall regarding sediment-related disasters

Setsuo HAYASHI and Takashi YAMADA

Abstract

We previously proposed the degree of rainfall (H) as an indicator to evaluate heavy rainfall that causes sediment-related disasters. This indicator was introduced by using two factors for local rainfall: antecedent rainfall and triggering rainfall. Although the proposed degree of heavy rainfall (H) is useful to classify and evaluate extreme torrential rainfall in various places, the effectiveness as a factor to determine sediment-related disasters has yet to be evaluated. To clarify this relationship, we examined the relationship between the number of slope failure occurrence areas (n) and the degree of rainfall (H) for major heavy rain by year in Kure City from 195l to 1972. There is a strong relationship (n=aH ^b, a= 3.39, b=4.3 coefficient of determination: R²=0.94), suggesting that slope failure strongly depends on the degree of heavy rainfall (H). Consequently, the degree of heavy rainfall (H) is a useful indicator to evaluate and analyze heavy rainfall causing sediment-related disasters.

Key words

evaluation of heavy rainfall, amount of heavy rainfall, local rainfall, antecedent rainfall, triggering rainfall