Session1: River Engineering and Management
Title: NUMERICAL SIMULATION OF MUD FLOW GENERATED IN ATSUMA, HOKKAIDO, JAPAN
Arata Ishikawa, Hiroshi Takebayashi, Masaharu Fujita
In Atsuma, Hokkaido, mud flow occurred due to the 2018 Hokkaido Eastern Iburi Earthquake. In this study, numerical simulation of the mud flow is conducted to discuss its flow characteristics. The governing equations on the bases of the two-dimensional continuum body model are used in the numerical analysis. Results showed that the depth averaged velocity of the mud flowing down the slope is 13.5 m/s and the depth of the mud flow when reaching the house is about 6 m. The mud flow spread over farmland widely. The mud flow reaches the house in about 6 seconds. It is impossible for residents living at the bottom of the slope to evacuate, because the mud flow originated from the earthquake, and 6 seconds is too shot to evacuate. Therefore, it is important to avoid as much as possible to build houses near slopes with topsoil composed of fine-grained pyroclastic fall materials with high moisture retention