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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.

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.

The purpose of this study is to clarify the influence of entering fresh water from rivers into Tanabe bay area. The water temperature of fresh water is one of an important factor for ocean flow structure and three-dimensional structure of water temperature and salinity in coastal area. Fluctuation of river water temperature is repeated every day and seasonally, and it is influenced by elevation, atmospheric condition, confluence of river branch, groundwater, and water utilization of upstream area. In this study, we have conducted field measurement of river water temperature in neighboring rivers of Tanabe bay and will continue it for the next few years, in order to create estimated equations for river water temperature based on our measurement results. In this paper, we reported measurement method and initial progress of measurement results.

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.

This paper presents numerical simulation of riverbed variation using two-dimensional depth-averaged flow model with a simplified Lagrangian bedload model and its application to actual river. The scheme of Lagrangian-type bedload model resembles the actual phenomenon of sediment movement in comparison with the model of Euler type and it is useful when the change of sediment movement direction is extreme on a small scale. The Lagrangian-type model can simulate a change in the direction of moving sediment considering the local flow and bed slope along the moving paths regardless the computational grid structure. However, the heavy computation load is a significant bottleneck for a simulation in many cases. In this study, we introduced the simplified Lagrangian bedload model to a two-dimensional depth-averaged flow model and applied the model to an actual river.

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 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 paper presents an experimental study on the impacts of series of spur-dikes on bed topography and sediment sorting process of bed surface around impermeable spur-dikes. It was found that the vortex systems around spur-dikes were different in comparison with different number of spur-dikes and different submerged conditions on equilibrium stage. Compared with the results of single spur-dike cases and series of spur-dikes cases, the vortex systems are quite different between the spur-dikes. These differences cause different sediment transport and sorting process between the spur-dikes. The coarsened longitudinal region and fine sediment regions were observed, and it was indicated that series of spur-dikes also create not only bed morphology, but the diversity of surface bed composition. Furthermore, the scouring, deposition and sorting processes around spur-dikes were simulated by 3-D RANS with non-equilibrium bed load model using unstructured mesh system. The simulated results show generally good agreement with the experimental results of bed morphology and sediment sorting.