Abstract
Typhoon No. 21 in October 2009 brought torrential rains to the southern part of the Kii Peninsula and did not cause external flooding of the Shingu River. However, about 1,000 households in the inland area were damaged by inland flooding due to the simultaneous occurrence of the peak river level, peak rainfall within the tributary river basin, and peak tide level. The purpose of this study is to understand the hydrological and hydraulic characteristics of the main and branch rivers that caused secondary inland flooding, and to propose measures to mitigate inundation damage based on these factors. We have clarified the causes of secondary inland water inundation from hydrological and hydraulic data, and summarized the actual damage from a questionnaire survey of the victims at the time. In addition, a model was developed to estimate the detailed damage. We estimated the amount of damage caused by the target typhoon and confirmed the effectiveness of disaster mitigation measures. It was found that the damage was reduced by several disaster mitigation measures, after we had estimated the past flood damage. The results of this study are expected to show the effectiveness of the project in promoting disaster mitigation measures in the objective areas.
