In Japan, there was no widely-used general-purpose platform software, on which hydraulic and hydrological analysis model developed by others conduct water circulation simulations of river basins. This fact made it difficult to accumulate study results and reflect them in projects such as river improvement works. In this paper, firstly, we analyzed wide-range of domestic problems regarding hydraulic and hydrological analysis, and secondly surveyed development history and development specifications of existing general-purpose platforms, and then studied adaptivity of these general-purpose platforms for the problems. Based on the results, we analyzed development policies and functional requirements of a general-purpose platform to be developed in order to solve the problems. Finally, we designed program of the general-purpose platform to realize these functional requirements.

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 An emergency response-type flood prediction was conducted for the devastating 2011 Thailand flood with a recently developed Rainfall-Runoff-Inundation (RRI) model. The prediction conducted in mid-October 2011, when the flood peak was just approaching, indicated that the large-scale inundation in the lower part of the Chao Phraya River basin might remain in the area even until the end of November. The post flood analysis verified that the above prediction was reasonable. On the other hand, the predicted discharge and inundation water level during the peak flood were overestimated by approximately 40% and 2 m, respectively. According to the numerical simulations with updated input information, the ignorance of the evapotranspiration effects was the dominant factor for the overestimation among uncertainty factors including the representations of dams and river cross-sections. Based on the detailed validations and analysis, this paper discusses what the up-to-date RRI model can and cannot predict and what information should be prioritized as input over other information.

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 Numerical simulation of inundation in actual underground space in Tokyo was conducted. Urban inundation around the space was also computed simultaneously. Characteristic of the inundation process in the space was made clear as a result of this investigation. Evacuation movement of persons from the space was also studied by using the newly invented numerical model. An evacuation route from this space was successfully found and recommended in this study. It was confirmed that the guide for evacuation was effective to make the persons evacuate orderly and safely. The announcement for the persons there to be urged toward the evacuation is also effective so that the evacuation can complete more rapidly. But the special consideration must be needed about the timing not to make the persons be in panic.

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 This study clarifies the water quality characteristics of stagnant, eutrophic water bodies that freeze in winter, based on our surveys and simulations, and examines how climate change may influence those characteristics.
 The survey found that climate-change-related increases in water temperature were suppressed by ice covering the water area, which also blocked oxygen supply. It was also clarified that the bottom sediment consumed oxygen and turned the water layers anaerobic beginning from the bottom layer, and that nutrient salts eluted from the bottom sediment. The eluted nutrient salts were stored in the water body until the ice melted. Climate change was surveyed as having caused decreases in nutrient salts concentration because of the shortened ice-covered period; however, BOD showed a tendency to increase because of the proliferation of phytoplankton that was promoted by the climate-change-related increase in water temperature in spring.
 To forecast the water quality by using these findings, particularly the influence of climate change, we constructed a water quality simulation model that incorporates the freezing-over of water bodies. The constructed model shows good temporal and spatial reproducibility and enables water quality to be forecast throughout the year, including during the ice-covered period. The forecasts using the model agree well with the survey results of shortened ice period and climate-change-related increase in the BOD in spring.

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 The phase lag of a stream meandering to channel curvature generates a lateral shift in the main stream toward the bank and deforms the river channel. This paper presents a new 1-D analysis method for calculating the lateral shift of the main stream in arbitrary curved channels. The model includes the effect of secondary circulation on transverse momentum transport differently from an existing 1-D analysis method based on shallow water equations. The new model, which is a quasi-3-D 1-D model, was first tested for laminar flow in a single-bend channel and a meandering channel, and then applied to turbulent flow in sharp and mild single-bend channels and a meandering channel. Comparison with flume experimental data showed that the new analysis method reproduced the longitudinal variation in the stream shift very well, both in laminar and turbulent flows.

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 This study aims to investigate evacuation strategies for residents in big cities during large-scale flood damage. Based on the result of the flood disaster citizen opinion poll with the residents of Edogawa ward, a flood evacuation simulation was created a model their intended behavior. Using this simulation, an evacuation strategy was investigated that allows zero casualties in the case of the banks of the Arakawa River being broken. This paper covers problems identified from simulation studies, countermeasures in order to resolve such issues, as well as the course of action of future efforts to be taken.

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