Relationship between surface failure due to rainfall and geology�|Experience of sediment-related disasters in Miyazaki Prefecture due to typhoon No. 4 and No. 5 in July, 2007 as example

Naomasa HONDA, Nao KATO and Maiko KASAI

Geology is one of the important inherent factor of collapse generation. In this paper, we discuss the relationship between surface failure due to rainfall and geology by comparing actual collapse data with geological map data. Two sediment�]related disasters in Miyazaki Prefecture in 2007 are chosen. The correlation between rainfall characteristics and collapse generation depends on rainfall index R'. As a result, many surface failures occurred on the Neogene system. These surface failures occurred mostly in igneous rock areas, according to lithofacies, regardless of slope inclination. In addition, collapse generation rates differ between slopes with large inclinations.