This paper presents an uncertainty evaluation method for rainfall-runoff models and applies it to model selection considering data availability. Simulating model users' parameter calibration processes with Monte Carlo simulation technique, this method evaluates parameter uncertainty and its propagation to model output. Uncertainty in simplified models are evaluated comparatively from an ideal model that takes into account detailed physical rainfall-runoff processes.

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The mean-velocity properties of both polystyrene particles and fluid as well as particle concentration in smooth open-channel flows were investigated with a discriminator PTV. The particle and fluid were separated by discriminating the occupied area sizes of particle images and water tracers on a CCD camera. Of particular significance is the interaction between the turbulence and particle motion, and therefore in the present experiments, the ratio between the particle scale and the turbulence-length scale was changed systematically. The relative velocity is revealed by varying the particle diameter and specific density. The average particle-velocity, U_p, is slightly smaller than the carrier-fluid velocity, U_f, farther from the wall. In contrast, U_p is larger than U_f in the region of y⁺≤15. These noticeable phenomena are caused by the fluid-particle interaction. This interaction causes the momentum transfer of particles to the carrier fluid and the velocity gradient of fluid becomes flatter in the viscous sublayer.

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In compound open-channel flows, there are some large-scale horizontal vortices with a vertical axis. It is very important in hydraulic engineering and river environment to investigate hydrodynamic characteristics of coherent horizontal vortices in compound open-channel flows. From recent turbulence measurements, it was inferred that the horizontal vortices have 3-D structure of vortex tubes. However, the 3-D structure of horizontal vortices has not yet been revealed in detail in deep-depth floodplain flows. Therefore, in the present study, turbulence measurements were conducted in deep-depth floodplain flows by using dual-layer PIV technique. The vertical correlation between horizontal eddies was revealed by the dual-layer PIV measurements.

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We highlighted mainly on the transition region from straight to meandering compound open-channel flows, in which horizontal vortices are changed due to the spatial variations of velocity shear and secondary currents. 3-D velocity measurements were conducted by electromagnetic velocimetries (EMV), and the bed-shear stress, secondary currents and the momentum exchanges were investigated experimentally. Furthermore, PIV measurements were also conducted in order to visualize horizontal eddies, and the meandering convection mechanism of these coherent eddies was revealed and a hydrodynamic model was proposed then in the present study.

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Inundation process in underground space as well as on a ground surface in urban, which is caused by a heavy rainfall, was studied numerically. Considering the real data of (1) road network, (2) drainage network and (3) underground space in the area around Shinjuku Station, a simplified numerical model was developed. Based on the results, it was revealed that both the underground space and some local area whose ground elevation is relatively lower have the possibility to have a serious damage if there happens to be the rainfall whose intensity exceeds the designed one. Some more investigation was conducted to understand how we could mitigate the damage of inundation in underground space.

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The purpose of this study is to verify the applicability of Carrier and Greenspan's theory for the case when internal waves shoal and break on a slope. Because Carrier and Greenspan's theory could not provide the solution in the internal wave breaking zone, we assumed that there is no flow in the breaking zone corresponding to that turbulence due to internal wave breaking does not influence on the flow field in the breaking zone and is consumed by dissipation on the slope. The internal wave breaking point was estimated from stability analysis. From three dimensional numerical computation, it was confirmed that the turbulence due to internal wave breaking disappeared without reflecting on the slope due to dissipation. Therefore, the validity of the assumption that the turbulence due to internal wave breaking is consumed on the slope was confirmed.

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Dominant hydrodymic forces on beach material of gravel beach and mechanism of resulting sediment movement are investigated. To evaluate hydrodynamics forces, velocity fields on the beach are measured in laboratory experiments using cantilever-type velocimeter. In the experiments, deformations and grading process of material of different sizes are investigated. Critical conditions for several types of sediment movements are derived assuming static state. Then these conditions are compared with acting wave forces evaluated by the Morison equation and mechanism of sediment movement is discussed. Through the investigations, infiltration flow during rundown process is found to cause asymmetric exerting force on bed material. Comparisons between wave force and stability condition give good explanation for dominant direction of sediment movement and resultant beach profile. Moreover, the present results are found to be consistent to the beach profile observed at real gravel beaches.

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A flowage analysis in the period of the Seawater Introduction Survey in 2002 at the Reservoir of the Isahaya Bay Reclamation Project was conducted with the three dimensional numerical model of Ariake Bay developed by four ministries of the government of Japan. The phenomena observed at the Isahaya Bay and its adjacent area were almost reproduced by this model. But there were a few differences between the calculation and the obserbation, response analysis carried out to improve the model by inputting various data of wind and temperature. The details of input data of wind and temperature are important to fitting the model to the northern part of Ariake Bay.

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A questionnaire survey was undertaken for residents' evacuation against tsunami attack and factors of their decision-making on the earthquake of Miyagiken-Oki which occurred on May 26, 2003 and it was carried out in Kesennuma City, Miyagi Pref.. As the result of the survey, it turned out that almost all residents were afraid of tsunami attack, but they did not evacuate.
Then we analyzed residents' evacuation and their consciousness of tsunami. The main problems of residents' consciousness of tsunami cleard by the analysis are follows. 1) Since residents depend for decision-making of evacuation on evacuation order and tsunami warning, they cannot make decisions evacuation even if they feel a big shake. 2) By the normalcy bias, residents estimate the danger level of tsunami optimistically. 3) Residents' tsunami experience has influenced with their tsunami image strongly. 4) However residents depend on tsunami information, they tend to make light of them. In this paper, we discussed what education the tsunami prevention should be for improving those problems.

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The old river facilities “Shingen-embankment” in Japan and “Dujangyan” in China are still working in the present days. Several techniques of water control and the wisdom of living with flood can be found in these facilities. These forerunner's wisdoms can also be found in the Japanese historical documents.
The present paper aims to clarify the symbiotic science which had been learnt in the long history with rivers, and to arrange these wisdoms to utilize for today. It is proposed here to apply these wisdoms including establishing a local self-management system and a mutual partnership between the government and the public, as a principle on water management to build a sustainable society in the 21st century.

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By using the MHI oceanic model, the upper layer currents, the surface heat and freshwater fluxes, the sea surface temperature (SST) and the sea surface salinity (SSS) are simulated for the Japan Sea. Given atmospheric variables are used for the surface heat and freshwater balance calculation; no restoration condition towards observed SST or SSS is applied. The simulated surface fluxes, SST, and SSS compare well with the long-term data. The simulated freshwater flux is directed from the air to the sea in spring and summer and from the sea to the air in autumn and winter. The simulation results suggest that SSS in the Japan Sea is mostly controlled by the surface freshwater flux and advection through the straits.

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Study results show the propagation of near bottom cold onshore currents that followed the internal waves in an area where bottom topography is characterized by gentle slopes. The cold water currents finally penetrated into Shiraho reef area and were found to affect the water circulation pattern and thermal environment significantly around Tooru-guchi region where a big reef gap is located. After cold westward current penetration, a significant temperature fall was observed in the reef area. As cold westward current flowed in the bottom layer, warm currents headed offshore through the surface layer. The characteristic currents and thermal environment of the region are discussed in detail.

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