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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.

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 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.

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 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 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.

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 intensive field observations carried out in the summer seasons in 2012. The intensive field observations have been conducted at the observation tower of Shirahama Oceanographic Observatory (SOO), DPRI, Kyoto University. One of the aims of the observations is field data measurements to comprehend the vertical mixing process due to wind and wind wave. During the observations, one typhoon (TC17, Jelawat) hit the Kii peninsula and passed along the southern coast of Japan. In the observation, the vertical profiles of currents and water temperature have been measured as well as wind and wave conditions. The main results are as follows: Strong wind and high wave conditions have occurred when the typhoon hit the observation site. The water temperature felt down a few hours later the typhoons come close to the observation site. The observed results underline the needs for the continuous observation activities and multidimensional data analysis.

白浜海象観測所では，毎年夏期に台風接近時の気象・海象データ計測を目的とした集中観測を実施している．2011年の夏期集中観測は8/11-11/8の間実施され，観測塔による波高，潮位，海水温計測に加えて，ADCPによる流速分布計測，水深30mまで計測範囲を拡張した海水温計測が実施された．観測期間中，台風12号および台風15号が紀伊半島付近を通過した．観測塔近くでADCPにより計測された流速分布は，風の変化(特に南北方向)に対応した変化を示した．台風最接近時にはADCP設置地点(水深約9.2m)付近まで鉛直混合が発達していることが確認された．また，台風接近時の観測塔付近の波浪状況や水温の鉛直分布が異なる様子が計測されたほか，河川水位の上昇に対応した表層水温の低下も観測された．, This paper shows some results of a field observation carried out in the summer of 2011. The field observation have been conducted for three months (from August to October) at the observation tower of Shirahama Oceanographic Observatory. During the observation, two typhoons (No.12 and No.15) hit the Kii peninsula, and the current and temperature profiles have been measured under the storm conditions as well as wave and wind conditions. Under the storm conditions, the current and temperature profiles show uniform distributions in the vertical direction, and this means that vertical mixing develop well in the surface layer. After typhoon passed, water temperature decreased in 04 Sep. 2011. Electric conductivity also dropped down at the same time. It is expected that flood water from the river would flow into the Tanabe bay and reached to the observation area.

バングラデシュ国の河川では, 河岸侵食が大きな問題となっている。河岸侵食は科学と工学的な問題だけでなく, この南アジアの国にとっては, 大きな社会や経済問題でもある。本稿は, ブラマプトラ川の下流(バングラデシュ国内ではジャムナ川と呼ばれる)における河岸侵食防止対策及びそれらが流れ及び地形に及ぼす影響について報告する。数回の現地調査及び計測により, ジャムナ川における河岸侵食のメカニズムの解明を図った。また, 既存の河岸侵食防止対策の機能を評価し, 可能な改善策を提案した。特に, 現地の歴史的な方法で土着工法の代表であるバンダル型水制について着目し, ジャムナ川の河道安定及び河岸侵食防止方策としては, バンダル型水制の設置の繰り返しが現地に適応した工法となり得る可能性を示唆した。, Bank erosion is a severe problem in the rivers of Bangladesh. Besides the important scientific and engineering relevance, bank erosion also exerts significant social and economic impacts in this southern Asian country. This paper describes typical bank protection measures as well as their hydraulic and morphological consequences in the lower part of the Brahmaputra River (named the Jamuna River in Bangladesh). Based on a series of field investigation results, attempts have been made to clarify the mechanisms of bank erosion along this large alluvial river. Moreover, the performances of existing bank protection measures are evaluated and possible solutions for further enhancement are proposed. Special attention is paid to a historied and indigenous river training structure: Bandal. The recurrent use of Bandal-like structures is suggested for bank protection and channel stabilization of the braided Jamuna River.

本報告は, 2008年夏の大潟波浪観測所・観測桟橋撤去後に行われている海底地形計測および海底底質の調査結果を示すものである。今回の観測は, 大潟波浪観測所の旧観測桟橋周辺において2010年8月に行われた。調査項目は, GPS機能付き測深器による海底面形状の計測, 海底表層の底質採取, および海底底質のコアサンプリング調査である。海底面形状の計測では, 2009年に計測された結果とほぼ同様の海底面形状となっていることが確認された。海底底質のコアサンプリング調査からは, 沿岸砂州をはさんで岸側と沖側で粒径分布が大きくことなり, 沖側では淘汰が進み深さ方向にほぼ一様の粒径分布となっていることが確認された。, This paper shows some results of a field observation carried out in Aug. 2010 in Joetsu-Ogata coast. In this field observation, three measurements have been conducted; (1) bottom profile measurement with depth sounder and (2) collection of the samples of bottom sediment, and (3) sampling of boring cores. The observation site is near the location of old observation pier, and the size of the measurement area in longshore and cross-shore directions are about 900m and 800m, respectively. The bottom profile in the observation site is measured by the depth sounder with GPS locator. It is found in the 2D bottom profile that a crescent-shaped sandbar and shoreline retreat exist. From the results of core sampling, the sorting of grain size in cross-shore direction and the deposition in alternate layers are observed.

近年, 記録的短時間降雨の発生頻度が増加しており, 下水道による雨水排水能力を超えた内水氾濫や中小河川の疎通能力を超えた外水氾濫が発生している。本研究は, 大規模地下街を含む都市域を対象にし, 内水氾濫時における地下空間の浸水に対する脆弱性と避難困難度についての検討を行ったものである。地表部での内水氾濫を下水道網を考慮したモデル(InfoWorsk CS)を用い, 地下街への流入量を算定して地下空間の脆弱性を検討した。さらに, 2次元構造格子モデルを用いて大規模地下街における浸水過程を計算し、実物大模型を用いた避難体験実験結果に基づく避難困難度指標を用いて地下空間浸水時の避難困難度を評価した。その結果, 安全な避難計画の策定に資する避難困難度マップが得られた。, Torrential rains have been observed frequently in recent years in Japan and these rainfalls caused inundations in urban areas. Intensity of such rainfalls were sometimes excess over the capacity of drainage systems and rainwater was running over the road. In these floods, some portion of rainwater intruded into underground spaces and people there faced the danger of underground flooding. In this paper, underground flooding in a mega-underground mall were investigated by using 2D shallow flow model with structural mesh and evacuation from there was also studied with the criteria of safety evacuation obtained by evacuation tests. The results show that flooding processes and safety of evacuation depend on the inflow conditions into underground space.

本研究は, バンダル型水制周辺の流れがもたらす河床変化に着目した。バンダル型水制はインド亜大陸で古くから用いられており, バングラデシュを流れるジョナム川のような沖積河川では, 河岸浸食の防止, 航路の維持を目的として設置されている。しかし, 透過型・不透過型水制のような従来から用いられている治水構造物の代用として, バンダル型水制が真に有効であるかを検証した研究や現地調査は少ない。そこで, バンダル型水制が河川形態にもたらす影響を明らかにするために, バンダル型水制による複雑な流れや流砂メカニズムについて検討を行った。片側に２基の水制を設置した直線水路を用いて, 動的洗掘状態の移動床実験を行い, 水制周辺の河床位の計測と洗掘河床上の流れ場の計測を行った。数値解析モデルでは非構造メッシュを用いており, 各水制タイプについて流れと河床変動の計算を行った。これらの実験および計算結果を分析し, バンダル型水制が従来の水制と比べて周辺の局所洗掘を低減し, 水制背後への土砂堆積を促すのに有効であることを示した。, The present investigation is focused on river bed variation caused by flow patterns around Bandal-like structure in channels. This type of structure have been used from the past in the Indian Sub-Continent to protect the river bank from erosion and to maintain the navigational conditions in alluvial rivers as the Jamuna river in Bangladesh. Few laboratory studies and field observations using Bandal-like structures was realized to verify the real applicability of them as an alternative structure over conventional river training structures as groins (impermeable and permeable ones). To clarify the effectiveness of Bandals in river morphology, detailed investigation about the complex flow structures and sediment transport mechanism influenced by Bandal-like structures was realized. Laboratory experiments were conducted in a straight flume with two structures positioned on one side of channel to the measurements of the velocity field and bed level near the structures under live-bed scour condition. A morphological model based on unstructured meshes was developed to simulate the flow patterns and bed variation around these structures. The experimental and numerical results of flow distributions and bed level variation around each type of structure were analyzed. The Bandal-like structure shows promising results as the reduction of local scour around them and deposition of sediment at downstream of Bandals in comparison with the conventional structures as groins.