Changes in the characteristics and transport of surface sediment in Osaka Bay after the Kansai Airport reclamation (1987) and Akashi Bridge construction (1998) were investigated by analyzing surface sediment samples collected in 1982 (27 sites) and 2003 (28 sites). The median diameter of the sediments became coarser in size, while the distribution of sediments shifted to the finer fraction, and the sorting coefficient became bad in the central part of the bay in the period between 1982 and 2003. The northward transport of the sediments was dominant in the central part of the bay between these years. These results suggest that the current speed in the central part of the bay became stronger from 1982 to 2003 due to large scale developments such as Kansai Airport reclamation and Akashi Bridge construction, and the transport of coarser surface sediments from the central part to the Akashi Strait became a dominant process.

Frontal waves around tidal fronts and their influences on the cross-frontal nutrient transport were investigated by the observation around the Hayasui Strait int he western parto fth e SetoI nland Sea, and byli near stability analysis and numerical modeling. A frontal wave with a wavelength of about 10 km was detected in the field observation. Using stability analysis, the wave was explained by a baroclinic instability wave with the maximum growth rate. In addition, the numerical model well reproduced frontal waves with nearly the same wavelength. In the numerical model, passive tracers representing nutrients int he real ocean were carried fromt he mixed region intot he thermocline of the stratified region by the cross-frontal transport associated with frontal waves. These results therefore suggest that the cross-frontal nutrient transport caused by frontal waves is important to produce thermocline chlorophyll-a maxima that have been observed frequently around tidal fronts in the real ocean.

The characteristics of velocity and temperature of a horizontal buoyant jet, cooler and denser than the in situ unstratified environment fluid, were studied experimentally. Based on these experiments, the behavior of the horizontal buoyant jet depends on parameters such as internal Froude number (Fr), Brunt-Väisälä frequency and Reynolds number.

Because the behavior of diffusion in the discharged water changes as these parameters change, it is important to understand how these parameter affect the diffusion process of the buoyant jet. However, few studies of the dependency of the parameters have been reported so far.

Present work focuses on the dilution of velocity and temperature along the trajectory of the buoyant jet and its dependency on internal Froude number. As a result, normalized trajectory of the negatively-buoyant jet can be expressed by x₂/lм∞(x₁/lм)³(Fig. 2, 3). This is independent of the internal Froude number and of the dilution of mean velocity and mean temperature, which have different processes according to difference of an internal Froude number.