In 2019, Typhoon Hagibis caused enormous damage in eastern Japan. This study investigates the characteristics of the residents’ response behaviors to Typhoon Hagibis. I employed a questionnaire survey to analyze the effects of prior risk information and recorded the time-wise behavioral change of the responses. These were classified based on their timings during the approaching typhoon. The study also examined the influence of the attributes of residents on their responses and conducted a review of the situation after the disaster and behavioral changes caused by explaining the situation of disaster potential. The responses were classified into six categories, three of which accounted for a major proportion. Time-series analysis confirmed that most residents acted after October 12, judging that danger was imminent. Prior risk information was not adequate for raising awareness of the disaster risk, and gaps were confirmed in the disaster images before and after the disaster.

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This study proposes the productive application of the “nudge” concept to the field of disaster risk reduction and evacuation. Nudge, the concept proposed by Thaler and Sunstein, is the indirect induction to influence behavior using the choice architecture. The nudge is conceptualized as two binary opposition axes that locate the “rational human model/heuristic human model” on the vertical axis and “freedom of choice/restriction of choice” on the horizontal axis. The upper part of the conceptual diagram is the “judge” domain based on the actor’s rational choice and the lower part is the nudge domain, based on the actor’s heuristic choice. The conceptual diagram and criticism in using the nudge identified that consensus building between the interferer and the interfered person and mutual use of “nudge” and “judge” is the key to effectively utilize the nudge.

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Most of the rivers in Japan are small and medium-sized rivers managed by local governments. In order for rivers to fulfill their functions at all times and during floods, maintenance such as periodic longitudinal surveying and weeding is necessary. The purpose of this study is to understand the actual conditions of maintenance in small and medium-sized rivers. The results show that maintenance is not sufficiently implemented in small and medium-sized rivers. In addition, conventional methods are still the mainstream surveying techniques, and new technologies such as UAV photogrammetry have not been widely adopted. On the other hand, it was found that there is an Adopt-a-River system throughout the country, which is responsible for weeding.

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The active thunder cloud accompanied by the cold front went ahead through the middle area of Shizuoka Prefecture towards the east at about 60 km/h at around 18:30 on May 1, 2021, and a tornado occurred in the unstable atmospheric situation in the area of Makinohara City. The tornado advanced from Sabaka, Kikugawa City eastward to Katsuta, Kiriyama, Katsuma and Sakabe district through Nunobikihara district of Makinohara City. According to the field investigation, the migration length of the tornado was 7 km and the maximum damage width recorded in the Nunohikihara area was 130 m. The damage, extending to about 100 buildings such as houses, factories, and warehouses, as well as agricultural pipe housing, utility poles, and carports, was evaluated as JEF2, based on the Guidelines for the Japanese Enhanced Fujita Scale.

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