During the heavy rain in July 2018, emergency warning was issued by Japan
Meteorological Agency, and evacuation orders and recommendations were issued by
municipalities. In fact, many people, however, did not evacuate and stayed at home. This study
conducted a questionnaire survey in Nishikyo Ward, Kyoto City, where there was concern
about the flood of Katsura River and for which an evacuation order (emergency) was issued.
The survey aims to investigate the relationship between personal attributes such as differences
in the recognition of disaster and the actual situation of evacuation behavior. Results show that
there is a relationship between perception of river flooding and evacuation behavior. Even after
obtaining evacuation order, low percentage of people evacuated. The reasons for the failure
to evacuate indicate the surrounding conditions such as weather condition and time affected
the evacuation behavior. Despite recognizing that the house was expected to be inundated by
the inundation hazard map, few people actually evacuated, indicating that there was cognitive
This research defines “evacuation attitudes” as people’s predetermined principles regarding whether they have a possibility of taking evacuation actions during a heavy rain or under evacuation advisory information issued from a local government. Evacuation attitudes can be thought as formed by peoples’ experiences such as vain evacuations in past disasters, and/or various restrictions such as having pets or mobility problems. Our analysis classified evacuation attitudes into three different types: a group to evacuate under evacuation advisory information, a group to evacuate by their own decision, and a group never to evacuate. Based on the analysis of 3000 households replying to our questionnaire surveys, it is demonstrated that nearly 50 indices, including flood/landslide risks and community activities, affect the evacuation attitudes and actual evacuation actions at the time of the 2018 Japan floods.
Due to the heavy rainfall caused by Typhoon No. 19 in 2019, precipitation was recorded at 300-400mm in the Saku District of the upper Chikuma River on October 12. The highest water level ever observed was recorded at 12.46m at the Tategahana Water-Level Observatory located at the middle reaches of the Chikuma River at 3:20 the next day. As a result, the dike collapsed 70m section in the Hoyasu District of Nagano City (approximately 4km from the upper reaches of the Tategahana Water-Level Observatory), and the ensuing floodwaters flowed onto the inland bank. Residential houses were washed away and completely destroyed. At the Shinkansen vehicle center located in the low-lying area of the floodplain, 120 vehicles comprising 10 compositions were flooded to seat level and considered a total loss. Inundation damage of 100-400cm occurred in the former town office area and in the new residential area in the Toyono District, caused by the floodwaters that flowed over the dike for the Asakawa River (a branch of the Chikuma River) from the Akanuma District. The inundation area in the northern region of Nagano City (Naganuma, Toyono, Furusato) encompassed approximately 934ha and almost coincided with over 2m of flood inundation assumption areas. Furthermore, there were 1,034 buildings completely destroyed, 285 buildings large-scale partially destroyed, and 360 buildings partially destroyed, 292 buildings part destroyed for a total of 1,971 buildings.
The autumnal rain front became active, and precipitation reached nearly 400 mm in 24 hours in Takeo in the upper Rokkaku River area of West Saga Prefecture from the early morning of August 27, 2019 until the early morning of the 28th. The precipitation was observed to be particularly heavy in the early morning hours of August 28th, with 210 mm falling in 3 hours. As a result, the water level of the Rokkaku River rose, and “driving adjustment” to turn off a pump to prevent the collapse and overflow of the embankment was carried out. Inland flooding occurred since rainwater in the city area inside of the dikes could not drain. The heavy rain caused the water level of the Ushitsu River, a tributary of the Rokkaku River, to rise, and flood damage occurred in farmlands and in the city area from water that overflowed the dikes.
In addition, inland flooding occurred in the city of Saga, and damages within the prefecture extended to 6,060 buildings.
This study tries to clarify the factors and mechanisms affecting the embankment dams that were either damaged (d) or undamaged (u) due to the earthquake on northern Awaji Island.
Multivariate statistical analyses (including 10 or 11 items) were performed on 395 dams (d:112, u: 283) in the Nojima fault area (Nj) and on 1562 dams (d: 348, u: 1214) in the 5 Town area (5T). On the peaks of category score (CS) for main items, there are six angles to the epicenter (Nj: 10, 150, 30, 70, 100 and 130 deg. in the order of CS peak values, 5T: 100, 160, 140, 70, 40 and 10 deg.id.), seven angles to the fault (Nj: 100, 80, 20, 160, 40, 140 and 120deg..id.), one for the distance to epicenter (Nj・5T: 10 km), and two for the distance to the fault (Nj: －150 and 600 m). These results can be explained by the radiation patterns. When they are combined with the relation between the emphasized seismic waves ( P or SV: 45 and 135 deg, and SH: 0 and 90 deg., theoretical emergent angles to fault) and CS peak angles, they support secondary strong motion source As’ as well as the primary As near the epicenter.
On September 6-7, 1898, a typhoon brought continuous torrential rain which caused floods and severe damage in the whole of Yamanashi Prefecture. In particular, a debris flow occurred at about 1:30 a.m. on September 7 at the southern foot of Yatsugadake, leaving 55 people dead and 51 injured in Yato section in Oizumi-mura. With 120 years having passed since the event, not only what was caused by the debris flow but also the disaster itself has disappeared from the memory of most local people. The author investigated newspapers published just after the disaster, and the “National Disaster Pictures” and “Storm Damage Survey Tables,” both compiled in the Meiji era and archived in the Imperial Household Agency. From these historical documents, the route of the debris flow that had caused the disaster was identified in this study. The author conducted debris flow simulation in the affected area applying Hyper KANAKO system. The results of simulation were compared with the debris flow route estimated from historical documents. It is suggested that a hazard of similar debris flow still exists in this area.