In considering a countermeasure against urban flooding, it is necessary to predict inundation flooding exactly. In this study, it is aimed to develop inundation flow models which can take account of streets and buildings in urban area. Cartesian coordinate, Generalized curvilinear coordinate, Unstructured meshes are applied to inundation flow analysis, and Street network model is also developed. Their results are compared with one another. These models have their own characteristics, therefore, in accordance with characteristics of the computational area or required accuracy of the results, the proper choice of these models will lead to advanced inundation analysis in urban area.

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A computational method has been proposed for viscous incompressible flows accompanied by oscillating free surfaces. The free surface profiles are represented by general curvilinear coordinates generated at every computational time step. The internal grid points are located by solving elliptic partial differential equations on the basis of the Arbitrary Lagrangian-Eulerian formulation. The transformed Navier-Stokes equations are discretized on the collocated grid arrangement. The velocity-pressure correction is performed with C-HSMAC method, which is effective for free-surface flows on the present coordinates and grid system. The computational method was applied to small amplitude standing waves under the effect of gravity and surface tension forces. In addition, it was also applied to non-linear waves caused by a pressure pulse imposed on a free surface. As a result, it has been shown that the predicted results are in good agreement with the theory and that the fluid mass is preserved with sufficient accuracy with the C-HSMAC method.

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Bed regulation works such as groins are effective measures to control the deformation of river bed near hydraulic structures. Myoken-zeki weir was constructed in the Shinano river in 1990. The result of this study shows the bed variation upstream from the weir according to installation locations of the bed regulation work, and the rectifiable effect of the weir on the downsream bed variation. The appropriateness of this measure has been proved by the floods that have happened after the construction. Further, it is confirmed that the results of river bed variation by the field measurement, the physical model tests and the numerical simulations coincide well. It was proved that both methods of physical model tests and numerical simulation adopted in the present paper provided a useful means for the design of river bed regulation works.

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The process of mass transfer across the interface between flowing water and bottom sediment is modeled to estimate the release flux of a dissolved substance in bottom sediment. Mass transfer through a diffusive boundary layer just above the sediment is analyzed using the theory of heat transfer. The distribution of solute concentration in the sediment as well as the mass flux at the sediment-water interface is formulated by considering adsorption/desorption between solute and sediment particles in sediment. These analyses yield the relationship of the release flux to flow velocity, adsorption/desorption parameters and physical properties of sediment. By using the values of adsorption/desorption parameters obtained from laboratory experiments, the present model has given satisfactory agreement between the release flux estimated by the model and the one observed in experiments.

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In this paper, turbidity behavior in a pumped storage reservoir is examined using a prediction method which enables to predict it well with taking account of turbulent flow, water temperature, turbidity and change of water level. The prediction results indicate that the upward flow and the turbulent diffusion, which are caused by a high-speed flow from an intake, may carry turbidity in the lower layer of the reservoir to the upper layer in plant operation. The present study suggests that adequate selection of operational conditions would suppress the increase of the turbidity at the upper layer of the reservoir. It means that there is a possibility to mitigate the turbidity with the optimal plant operation.

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A dynamic model associated with shoot density variation along water depth gradient including landward site has been developed to illustrate the growth dynamics of Phragmites australis. The environmental factors affecting the strength of tillering of vertical rhizome has been considered. The validity was confirmed by the below ground and above-ground biomass ratio and shoot height. The tendency that the growth potential of landward reed is changed dynamically by the water defficiency or nutrient condition was well represented by vertical rhizome length and land height. The growth potential curve is shifted to landward or waterward, when water depth become deeper or shallower than the water depth when the rhizome was formed, respectively. The importance of landward reed is depicted as a bufferzone of water-level fluctuation. The difference between potential biomass and observed data indicates nutrient or healthy conditions and the thickness of organic layer is closely related the difference.

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Field observations were performed to know the characteristics of flow and transport of materials in a mangrove area located in Ishigaki Island, in which geographical features, vegetation, water qualities, characteristics of soils and flow were measured by using various devices. At spring tide, organic materials and nutrients which have been provided by the mangrove forests are exported to the coastal area during low tide. On the contrary, the seawater which contains a large amount of dissolved oxygen moves toward the mangrove swamp during high tide. These results suggest that these transports of organic materials, nutrients and dissolved oxygen support biological activity in the mangrove and the coastal areas.

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Growth models of Typha angustifolia and Typha latifolia were developed by using energy budgets among their each organ. These models were validated by above-ground to below-ground biomass ratio, composition ratio, growth characteristics to water depth, and seasonal variation of above-ground and below-ground biomass in the center of colony. Seasonal change of each organ of Typha angustifolia observed in their senescent season was indicated that fertile and sterile shoots have their each strategy to form their seeds or clone, new rhizome, respectively. The rhizome expansion of Typha latifolia and Typha angustifolia in river is found to change much by the shape of transverse section and by the surrounding external force of their site.

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Turbidity is optical scattering intensity to suspended sediment. In this study, the influence of particle size on turbidity output was examined in laboratory, and the instructions for using turbidity meter in the field was discussed based on observation data. As particle size grow bigger, turbidity decrease for same SS concentration (SSC). The optical scattering intensity can be obtained up to the size of 0.42mm. SSC can be calculated by turbidity and particle size accurately. When turbidity is monitored in actual water area, SSC is converted from only turbidity using correlation curve between SSC and turbidity, because particle size distributions are not change significantly in the same station. It is desired to develop the new type backscatterance nephelometer which can measure not only the turbidity but also the particle size.

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