ANALYSIS OF FACTOR OF FLOODING DAMAGE EXPANSION BY THE NORTHERN KYUSHU HEAVY RAIN IN JULY 2017

A Northern Kyushu heavy rain caused a lot of flooding and landslides. The disaster gave a great damage to Fukuoka and Oita prefecture on July 5 in 2017. In this study, for the purpose of analyzing the factor of the flooding damage expansion, I collected information from newspaper, confirmed state of the damaged houses and measured the inundation level in disaster area, and conducted numerical simulation. First of all, in this disaster, 40 people died and 2 people are missing. From newspaper I could find that 73% people of victims didn’t refuge. In field survey, I found that many disaster area damaged by flood, sediment and driftwood. Comprehensively judge from a lot of collected information, it is considered that a lot of people of victims injured by flood. This is one of the character of this disaster. Next, I conducted flood simulation in Akatani River and Myoken River using iRIC which is river simulation software. I could not reproduce the real flooding area and water depth in both river when using the topography before disaster, because the simulation model takes only the water flow into account without sediment transport. However, in Akatani River, I could resemble the flooding area and water depth in the real flooding area and water depth when using topography after filled the river with sand. As a result of this research, I concluded that one of the factor of flood expansion is caused by the sand and driftwood.