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This report shows the field observation results conducted in the summer of 2018. The intensive field observation has been carried out for two and a half months (from August to November) at the observation tower of Shirahama Oceanographic Observatory. During the observation, three typhoons (No.20, 21, 24) approached the Kii peninsula, and the typhoon Jebi (No.21) and the typhoon Trami (No.24) brought sever wind and wave conditions. The observed maximum significant wave height and maximum instantaneous wind velocity are 11.09m by No.24 and 55.79m/s by No.21, respectively. High wave conditions caused significant damage to measurement devices on the observation tower which are installed for wave observation at the level of 10m high from mean sea level. Fortunately, wave data measured by ADCP (Acoustic Doppler Current Profiler) has a good agreement with wave data by measurement devices on the observation tower, and there is no major problem in data collection during high wave and strong wind conditions.

This paper shows the relationship between onshore-offshore movements of the Kuroshio and water temperature variation at an observation tower. Field observation has been carried out at at the observation tower of Shirahama Oceanographic Observatory (SOO), DPRI, Kyoto University, and measured water temperature data from 2015 to 2019 include both periods of straignt and meandering paths of the Kuroshio. When the Kuroshio has straight path, the axis of the Kuroshio exists close to the land, and the bifurcation current called "Furiwakeshio" often occurs. On the other hand, when the Kuroshio has meandering path, the axis of the Kuroshio aparts from the land. From the results of frequency analysis, variations of water temperature with about 30 days interval exist regardless of the axis positions of Kuroshio. This result indicates that some factors other than the onshore-offshore movements of the Kuroshio lay behind the water temperature variations at the observation site. Water temperature variations in the winter of 2017, 2018 and 2019 are also influenced by onshore-offshore movements of the Kuroshio. In 2017, the Kuroshio exists close to the land, and the existence of Kuroshio has a dominant influence on the water temperature variations. When the axis of Kuroshio is apart from the land in 2018 and 2019, water temperature variation at the observation site is affected primarily by the water temperature distribution in adjacent area. Drop in air temperature and movement of cold water mass act as triggers for an event of colder water around the observation site in 2018.

The annual intensive field observations have been conducted using Tanabe-Nakashima observation tower by research group of Shirahama oceanographic observatory in Tanabe bay, Wakayama prefecture. In this study, we have conducted CTD (Conductivity (salinity)-Temperature-Depth) measurements supplementarily in the same bay area during the same period as the annual intensive observations. Those CTD results showed seasonal variations of water temperature and salinity, such as thermocline and density stratification which were observed at many points in Tanabe bay and freshwater entering from neighboring rivers. This paper reports our observation activities in 2016 and shows CTD results and three-dimensional structures of water temperature and salinity based on observed data.

We made a diorama typed miniature model of urban area with river which can express urban inundation by river overflow, heavy rainfall and Tsunami. The miniature model includes underground space and underground storage pond. Using this model, we had a class on disaster prevention and reduction as a comprehensive school study for third and fourth grade students in three elementary schools, Kamitsu and Itami-Mimani elementary schools in Itami City, Hyogo Prefecture, and Nishitonda elementary school in Shirahama Town, Wakayama Prefecture, Japan. As a result, students could understand the flood mechanism and its countermeasures with interest. The miniature model introduced here can be an effective tool for education activities for students of elementary schools.

This paper shows some results of intensive field observation carried out in the summer of 2016. The vertical profiles of currents and water temperature measured as well as wave and wind conditions, and salinity observations carried out at the observation tower of Shirahama Oceanographic Observatory. In the summer in 2016, one typhoon (TC16, MALAKAS) approached close to the observation site, and the high wave and strong wind conditions more than 40m/s captured during the observation. Under the high wave and strong wind condition, ADCP (Acoustic Doppler Current Profiler) measured high echo intensities for several hours, and this result indicates that strong mixing occurs. Water temperature variation at 30m deep has opposite phase to the fluctuation of salinity. This result means that low temperature and high salinity water approaches to the observation site. It is also found in water temperature distributions in November that some influences of the warm and cool water mass exist.

This report shows the field observation results conducted in the summer of 2018. The intensive field observation has been carried out for two and a half months (from August to November) at the observation tower of Shirahama Oceanographic Observatory. During the observation, three typhoons (No.20, 21, 24) approached the Kii peninsula, and the typhoon Jebi (No.21) and the typhoon Trami (No.24) brought sever wind and wave conditions. The observed maximum significant wave height and maximum instantaneous wind velocity are 11.09m by No.24 and 55.79m/s by No.21, respectively. High wave conditions caused significant damage to measurement devices on the observation tower which are installed for wave observation at the level of 10m high from mean sea level. Fortunately, wave data measured by ADCP (Acoustic Doppler Current Profiler) has a good agreement with wave data by measurement devices on the observation tower, and there is no major problem in data collection during high wave and strong wind conditions.

This paper shows some results of a field observation carried out in the summer of 2015. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. In the summer in 2015, no typhoon approached around the observation site, and the high wave and strong wind conditions have not been captured during the observation. Several short-term rainfalls due to front and low pressure occurred, and it is reported that local areas in Shirahama town and neighboring towns suffered some damages with windblasts from late August to early September. It is found in the observation results of water temperature that the temporal variations of water temperature have a period of 3 to 6 days in the deeper layers like 20m deep and 30m deep. The cyclical fluctuation of water temperature at 30m deep has opposite phase to the fluctuation of salinity. This result means that low temperature and high salinity water approaches to the observation site periodically and that some influences of the water mass of the open sea exist.

The purpose of this study is to clarify the relation between sediment transport from river and topographical changes of mouth-bar by field measurements in Tonda river, which is second grade river flowing in south of Wakayama prefecture. Upstream areas of Tonda river were damaged by slope failures due to heavy rainfall which was caused by Typhoon No. 12 in 2011, and a large amount of sediment was supplied into the river. In this study, we will conduct field observations using RTK-GNSS during the next few years in order to capture the transporting phenomena of the overabundant supplied sediment from upstream area to estuary and sea. In this paper, we reported our recent results of field measurements.

This paper shows some results of a field observation carried out in the summer of 2014. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity and dissolved oxygen level observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. In the summer in 2014, a total of 4 typhoons (No.11, No.12, No.18 and No.19) approached to the Kii peninsula, and the high wave and strong wind conditons due to 2 typhoons (No.18 and No.19) have been captured during the observation. When the typhoons passed around the observation site, the high wave and strong wind occurred. However, the observation data of 2014 doesn't have clear shift of water temperature and salinity like the one by the typhoon No.18 in 2013. On the other hand, it is repeatedly found in the observed data that the reduction of water temperature and the increase of salinity happened simultaneously. This result indicates that the water temperature and the salinity around the observation site have some influence of the water mass of the open sea.

This report shows questionnaire results on disaster prevention consciousness of Tsunami. The targeted area is the school district of Nishi-tonda primary school in Shirahama Town, Wakayama prefecture. This targeted area includes a possible inundation area due to a massive earthquake occur in the Nankai Trough, and the maximum inundation depth is up to 10 m deep. The questionnaire survey conducted in all grades of Nishi-tonda primary school. Each family answered the questionnaire, and 221 answers in all returned (the collection rate is about 82 percent). The questionnaire has 26 questions regarding respondent's attribute, evacuation in the event of an earthquake, Nankai and Tonankai earthquakes, regional evacuation sites, gathering of information on disaster due to tsunami, and countermeasures on disaster mitigation. From the questionnaire results, it is found that public awareness of disaster prevention is potentially good, and some respondents recognize well that correct situational judgment for evacuation behaviors is important to ensure their safety in the event of an earthquake. On the other hand, some respondents answered that they don't know well about the regional evacuation sites and tsunami hazard map. Survey results showed that requests on transmission of relevant information and dissemination of knowledge have a majority as the countermeasures against damage due to tsunami. Even though the publicity of relevant information and knowledge is modest way as the countermeasures, constant publicity activities are important to raise the public awareness of disaster prevention.

The Kuroshio has a straight path before 2017 and change its path drastically to a large meandering path since the summer of 2017. The influence of the path change of Kuroshio on water temperature variation is investigated based on the comparisons of field observation data at the observation tower of Shirahama Oceanographic Observatory (SOO), DPRI, Kyoto University. Warm water mass often intrudes toward the north along the west coast of Kii peninsula when Kuroshio has the straight path. Warm water intrusion causes rapid water temperature variation at the observation site, and the frequency of rapid water temperature variation is more than the one when Kuroshio has the meandering path. Water temperature variation between the observation site and another observation site on the south side has relatively large correlation in the straight path case, and its correlation reduces in the meandering path case. This result indicates that the Kuroshio path has effects on the characteristics of water temperature variation at the observation site through warm water intrusion from south and that the characteristics of water temperature variation show different trends when Kuroshio has a meandering path. In the observed data of water temperature, noticeable variations of water temperature with about 30 days interval exist in both the straight path and meandering path cases of Kuroshio. This long period of water temperature variation is observed in the previous measurement data in 2013, and it is possibly suggested that noticeable variations of water temperature have influence of this kind of long period effect.

This paper shows some results of a field observation carried out in the summer of 2013. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity and dissolved oxygen level observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. During the observation, one typhoon (No.18, MAN-YI) approached to the Kii peninsula. When the typhoon passed around the observation site, the vertical mixing develops well, and water temperature at all measurement points show almost uniform distributions. It is also found during the typhoon passing that coastal upwelling through the Ekman transport happened clearly due to continuous southward wind. An EOF analysis decomposes the water temperature variation during the typhoon passing into 1) the increase and decease of water temperature and 2) the magnitude of the temperature difference in the vertical direction.