In this paper, the effect of the flood hazard map distributed to the residents who experienced flood disasters recently and an effective method for improving consciousness of flood di saster prevention are discussed. The questionnaire surveys were conducted on the residents living in the middle basin of the Nishiki River, Iwakuni city, Yamaguchi Prefecture, before and after the distribution of the hazard map. It is found from this investigation that "knowledge", "att achment", and "crisis", are the main factors in the psychological process related to the flood prevention behavior. The effect of the distribution of the hazard map is judged from the probability of the flood prevention behavior. In addition, it is also found that "knowledge", "flood experiment of T0514", "crisis", "eff ectiveness", "load", and "easy reading of the hazard map", are keys to improve the cons ciousness of flood di saster prevention.

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 Characteristics of inner structure of oblique upward flow in one-sided compound open channel flows at low Reynolds number were investigated by using Particle Tracking Velocimetry (PTV) and flow visualization techniques. The results of flow visualization in the flows with relative deep flood plain depth show that some fixed formative regions of str eamwise vortex exist and that large-scale streamwise vortices developing toward the water surface concentrate over the junction edge of the flood plain. The streamwise vortices have inclined motion toward th e main channel and generate instantaneous secondary flow, local low speed regions and instantaneous Reyno lds shear stress. On the basis of the results, time averaged properties ,which is large-scale twin circular secondary currents including oblique upward flow, are caused by spatial-temporal concentration of streamwi se vortices in the vicinity of the junction edge of the flood plain.

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 The current pattern and suspended sediment dynamics in the meandering channel of the Chikugogawa estuary were investigated. A secondary current was observed in the upstream region of the curve when the turbidity maximum migrates landward during a flood tide, and the suspended sediment concentration near the bottom increases at the inside of the curve. A fluid mud layer with a maximum velocity of 0.4 m/s was formed at the inside of the curve. The maximum thickness of the mud layer increased to 1.3 m during a flood tide, and it remained 0.2 m after three tidal cycles. Because the settling velocity of the suspended particles, as estimated by the Rouse equation, was higher than the theoretical velocity for a single mineral, particles collide and flocs are formed. The relationship between the pick-up rate of the bottom sediment and the shear velocity indicates reduced sediment erodibility during an ebb tide. Fine sediment processes in an estuarine channel could be explained as follows: suspended sediment is transported to the inside of the curve and settled sediments form fluid mud during a flood tide, following which the particles consolidate over the course of several hours and the pick-up rate reduces during an ebb tide; the morphological evolution of the river bed occurs at a semi-diurnal scale.

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 Recently, we often experience a localized torrential rain whose intensity exceeds much beyond the designed magnitude for both a drainage system and an urban river in Tokyo. On September 4-5, 2005, such an extremely heavy rainfall caused the inundation damage in the Myosyoji River basin. And also on August 5, 2008,five workers who worked in a trunk drainage pipe drowned because of the sudden concentration of rainwater in it in Zoshigaya area, Toshima Ward. In this study, numerical simulation model was developed in order to investigate how the rainwater can be removed by both a drainage system and an urban river in these areas during such a rainfall event.The validity of the model was verified by comparing the numerical results and the observed data. As a result of this study, the expanding process of inundation in each region explained above was made clear for some extent hydraulically.

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 Bedrock outcrops were observed in the lower reach (4.5 km long) of the Kurobe Dam in the Kinu River, Tone River system, from 1991 to 2008. The numbers of the bedrock channels were 19, 27, 41, 50 in 1991, 2001, 2006 and 2008 respectively, increasing gradually. In 2001, all bedrock channels that had been observed in 1991 existed and 8 bedrock channels had ne wly appeared. In 2006, sa nd and gravel accumulated in 2 of 27 bedrock channels that had been observed in 2001 and 16 bedrock channels newly appeared. In 2008, 6 of 41 bedrock channels in 2006 were sand-graveled and 15 bedrock channels newly appeared. Total length of the bedrock channels was 571 m, 756 m, 1247 m and 1309 m in 1991, 2001, 2006 and 2008, respectively. Percentages of the total length of bedrock channels in 100 m long sections were significantly greater in the upper sections (the sections near the dam) in each year. It was supposed that the dam had trapped sand and gravel that came from upstr eam and the river flow carried away sand and gravel that had accumulated in the lower reach below the dam causing the bedrock outcrops. In order to rehabilitate the bedrock channels, artific ial supply of sand and gravel below the dam with the installation of sand and gravel trapping structures in the riverbed is needed.

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 The wind response of salinity structures in Isahaya Bay was investigated by using the data of wind and salinity measured by the Kyushu Regional Agricultural Administration Office. In Isahaya Bay, the south-southwest wind and north-northeast wind were prevailing in summer season. It is known that the fresh water discharged from Chikugo River is transported along the west coast of the inner area of Ariake Sea and reaches to the mouth of Isahaya Bay. When a large amount of fresh water is discharged from Chikugo River and the northerly wind is blowing for a long period, the strong salinity stratification appears in Isahaya Bay. It is caused by that the northerly wind accelerates the transport of the Chikugo River originated fresh water into Isahaya Bay. After that, the salinity stratification is gone with the blow of southerly wind. The data-analysis reveals that the salinity structure in Isahaya Bay depends strongly on the fresh water from the Chikugo River and the wind blowing over Ariake Sea.

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