The present study aims to clarify thermal function of tidal flat and mangrove area in summer and winter. We conducted long-term field measurements for water and soil temperature in Sumiyo Bay, Amami Oshima Is. , which are known as a habitat of Ryukyu-ayu. The results showed that the water temperature of tidal flat and mangrove area was close to that of outer sea in summer and river in winter, showing the heat fluxes from water surface and bottom were dominant in tidal flat and mangrove area. The heat budget analysis indicated that the sensible heat flux from bottom of the tidal flat and mangrove cooled significantly water column in winter.

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In Isahaya Bay, the secular variation of hypoxic water mass and the correlation of concentration of dissolved oxygen (DO) near the seabed were investigated using the data obtained by the Kyushu Regional Agricultural Administration Office. The factors controlling the DO concentration and the characteristics of the spatial variation were also investigated by means of multiple regression analysis and principal component analysis, respectively. The rate at which Isahaya Bay was covered with the hypoxic water mass (DO . 4 mg/l) was largest in 2006. The hypoxic water mass occurred most frequently near the center of the bay, and the probability decreases toward the inner area and the Shimabara Peninsula. The multiple regression analysis indicated that the density stratification decreases the DO concentration near the seabed, and the Chl.a concentration increases the DO concentration. The three main modes in the spatial variation of DO in Isahaya Bay are shown using the principal component analysis.

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In this study, climate change impact of future water temperature on the fishery resources was considered. Future water temperature changes of Kiso River and Ise Bay were calculated by coupled river-ocean model under the CMIP3 A1B scenario. Water temperature increase of Kiso River was about 3 degrees, and sea surface temperature increase of Ise Bay was about 2 degrees. Coastal areas were more strongly influenced.
By the analysis of observed data, the upstream migration timing of sweetfish was negatively correlated with water temperature difference (sea – river). Calculated future water temperature difference was smaller than that of present, which resulted in earlier start of the upstream migration of sweetfish.

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The Shiretoko Peninsula which is located in the eastern part of Hokkaido, where nutrient circulataion between inland and the ocean is revealed to play a great role in ecological system. Because of the unique system, "Shiretoko" was registered as the World Natural Heritage. However, previous studies demonstrated that precipitation pattern has been affected by climate change, which may cause the change in the ecological system. Therefore, this study aims to evaluate nutrient flux from the inland to the ocean in the future. According to the previous studies, precipitation is consdered one of the most significant components controlling nutrient supply. Two bias correction techniques were applied by using the MRI-AGCM3.1S. As a result, it is revealed that the cdf correction techique shows better reproduction regarding the nutrient flux compared to the normal distribution correction technique.

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Run off characteristics of nutrients from small basins in Sigenobu river catchment area were invested in detail. These characteristics are summarized by using L-Q curve relationship, and first flush phenomenon in which nutrients concentration increased quickly during the early stage were observed in the cases of SS, T-P, PO₄-P, and T-N. Detail observation was conducted in Yuwatari area in which urbanized area, citrus grove, and forest exist. SS and phosphorus concentration in discharged water increased with the increase of flow rate of discharged water, which means the pattern of the loading rate of SS and phosphorus was "washout type". Run of amounts of T-P and T-N were calculated and 84% of T-P, and 61% of T-N were discharged during rainy days. Management of catchment area in rainy days is more important than in fine days in the area.

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This study examines a relationship between rainfall, land use and inflow loads of major rivers flowing into the Ariake Sea. Inflow loads are estimated by normal or freshet stage of water discharge. A multiple regression analysis is implemented to obtain both factor for characterizing the inflow loads and those of varying the amount of the inflow loads. From 1976 to 2006, the change of land use were not dominant in the river basins for the Ariake Sea. The Rainfall patterns, change were not recognized in the Ariake sea basin from 1981 to 2010. The river basin areas affect the inflow discharge and loads of COD, T-N and T-P. The land use greatly affects the inflow loads.

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Combined sewer overflow (CSO) has a major impact on water and benthic environments of rivers where CSO inflows. In this study, field surveys and laboratory analyses of water and sediment quality were carried out to clarify the influence of CSO on water qualities in an urban tidal river in Osaka City. Moreover, numerical simulation using a 3-D hydrodynamic model was also conducted to clarify the behavior of CSO pollution load in the river channel. Results indicated a strong possibility that suspended sediment delivered with CSO deposited immediately and affected water quality such as hypoxia in the channel near the CSO outlet.

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This paper treats the water quality problem on Hori river, Nagoya, Japan. Matsushige Lock Gate area is a big water area, situated at the middle part of the Hori River. This area is a place where the maximum sludge has been deposited and still during tidal behaviors, this sludge may play a pivotal role to change the water quality. Moreover, the transmitted water form Nakagawa canal has also made the water quality changed at Hori River. Therefore, water quality observations were done at Matsushige and Sanno Bridge, which are up and down streams of this Lock Gate area. From observation results, the inflow discharge from Nakagawa canal has an impact on the water quality of Hori River. Additionally, ADCP is carried out to find the distributions of water velocity along the longitudinal profile of Hori River. Finally, an effective timing of inflow discharge from Nakagawa canal is examined considering tidal change.

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In order to examine a water environmental improvement, human sense data on the water environment is very important criteria. However, human sense on the water environment has not been discussed in detail. This study examined the feature of human sense on the water environment and the relation between human sense data and physical behaviors which are tide, rain situation and seasonal change. This study area is Hori river which flows in Nagoya City. This study treats the human sense data of last 2007, 2008, 2009 and 2010 year from Horikawa Sennin Chosatai 2010. The place difference of feature of human sense as dirty is shown by using statistical examination with the Hayashi's quantification methods. And the human sense model is developed and the validity is shown by comparison forecasting human sense data and questioner results.

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The influence of the chemical water composition over water quality has been barely studied in the Andes. Condoriri River basin is located in the Royal Range of the Andes and provides drinking water to millions of people from La Paz and El Alto, the two major cities in Bolivia. The purpose of this study is to investigate the effects of nutrients and major ions composition over water quality formation during two different seasons, in order to determine the influence of glacier melting and the weathering of rocks. Field measurements were done during the dry and the wet season for the determination of physicochemical parameters and the water analysis for organic carbon, nutrients, and major ions. All water samples were slightly alkaline with pH average values of 7.99 and 7.85 in both seasons. Major ions have shown spatial variations, SO42- and Ca2+ had higher concentrations at the effluent water from the glacier. Source of major ions was identified as silicate, carbonate and sulphate weathering from rocks like gypsum.

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In the upstream area of Nagarariver estuary barrage, the high increasing of phytoplankton and decreasing of dissolved oxygen (DO) are occurred and these water quality changes are examined as the typical water quality problem on water area of Nagarariver estuary barrage. In this study, the analysis model developed for the examination of the water quality change. The validity of this analysis model, which is consist of the analysis of water flow, water temperature, chlorophyll, DO etc., is evaluated by comparing with observed data. And the method of the gate operation is discussed for the improvement of bad situation of water quality ( i.e. decreasing of DO). From this study, the keep of gate operation with under flow causes the decreasing of DO at near upstream and bottom region of the gate.

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A numerical model for calculating the behavior of radioactive contaminant associated with the sediment transport in rivers has been proposed in this study. The equations for simulating the concentration of radioactive contaminant of the sediment has been derived from the governing equation of the sediment transport model. The proposed model has been applied to a simple river confluence to understand the mixing process of the sediment and the radioactive contaminant in the confluence point. The numerical results provide a useful data for discussing the relation between the bed evolution process and the behavior of radioactive contaminant. In addition, the model can contribute to estimate the origin of the sediment by using the relationship between the simulated sediment diameter and the concentration of the radioactive contaminant.

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Water quality of sewage-treated water from Seibu sewage plant in Nagasaki city is always low value compared with the drainage regulations. However, it is necessary to consider about chromaticity and smell of sewage-treated water. In this study, experiments for chromaticity improvement of sewage treated water with micro ozone and jet equipment is done. As a result, chromaticity is reduced about 50 percent more effectively than conventional method, because ozone consumption rate goes up dramatically. And, it is clear that chromaticity is dominated by reaction rate equation. This developed method may reduce the initial and running costs for water quality improvement.

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Anchor ice is a phenomenon to accumulate of frazil ice on the river bed. This is formed due to the super cooling and a shallow, turbulent section of the river. But, it is a poorly understood and little studied topic. Our study focuses on elucidate the material cycle of freezing river. We observed a continuous observation of air temperature, water temperature, water level and all day shooting of anchor ice formation using IP-camera during an anchor ice presence-absence cycles. From the result, we found the critical element of anchor ice presence-absence is keeping super cooling condition. We attempted to analyze two-dimensional flow calculation and spatial distribution of photo image analysis of an anchor ice. As a result, we found spatial distribution of anchor ice is proportional to the Froude number.
We analyzed the contained materials of an anchor ice. As a result, a lot of algae (Hydrurus foetidus and diatoms) existed in the anchor ice. We showed the possibility that anchor ice affected the material cycle of freezing river.

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In Japan, environmental education on water quality has been conducted by schools and civic actiongroups across the country. PACKTEST is convenience tool to measure water environment in imminentwater space. However, the measurement of water quality value by PACKTEST is left to the sense of sightby observer; the measurement value tends to lack the quantitative performance. In this study, we proposean easy-to-use method to decide the water quality value of PACKTEST by using spectrophotometer andmonitoring on water environment of urban river is carried out. This method can remove the sight errormeasurer and keep the quantitative performance.

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This topic presents the effect of radioactive pollution in river on Stenopsyche sp. (Trichoptera: Stenopsychidae) at upstream and immediately downstream of Mano dam in Fukushima Prefecture, Japan. Stenopsyche sp. has high productivity with bivoltine life cycle among all invertebrate species, and can be a good indicator for any kind of environmental pollutions. The total radioactive cesium is always detected from Stenopsyche sp. with the order of 4,000 Bq/kg. A cause of high radiation intensity is due to very high intensity from the fine particulate organic matter (FPOM). However, its biological half-life was only about 6 hours for non-winter generation. Thus, FPOM is mostly excreted without assimilation.

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This study quantitatively evaluated Habitat Suitability Index (HSI) and species diversity of benthic invertebrates using a distributed hydro-thermal model and observed benthic samples from 45 localities in the Natori River basin, Northeast of Japan. We applied probability density function and histogram analysis to the Suitability Index (SI) model analysis. To evaluate basin-scaled habitat values of invertebrate families, we used the index Weight Usable Ratio (WUR). From the viewpoint of repeatability in the multiple modeling manners, Diptera had the highest WUR in basin. We estimated spatial distribution of Shannon-Weiner diversity index based on the HSIs to evaluate species diversity throughout the basin. Results in the both applications showed that regions found in the top 80% of the diversity index were allocated from the upper to the middle stream.

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As expected global increase in stream temperature triggered by climate change would alter benthic community composition of streams, it is necessary to understand the future variation of benthic invertevrates. First, we developed simple linear regression model to estimate the density of invertebrates by a water temperature metric as predictor variable. These data for the model were monthly collected during May-October within headwater streams which were homogenous in hydro-morphological characteristics. Secondly, we projected water temperature distribution within this basin for the two period in future using a distributed hydro-thermal simulation model which needed GCM data as inputs. Finally, we projected the variation of the density of benthic assemblage based on the regression model by annual mean of water temperature.

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Ohyamagawa Dam is an intake weir for two hydroelectric power plants along the upper Chikugo River, so-called the Ohyama River. After 2002, environmental flow regime has been changed from 1.5m3/s to 4.5m3/s in summer (April-September) and 1.8m3/s in winter for river restoration under regulated condition by dams. But, this improvement of environmental flow regime was not considered to give a satisfactory condition for the river environment. Thus, in 2011 we attempted artificial flushing experiments from the dam to improve it by detaching attached algae on the riverbed material as a possible countermeasure. In-situ measurement for hydraulic conditions and attached algae sampling were conducted during the flushing experiment. As a result of this research, flushing discharge of 40m3/s is the minimum appropriate discharge for the Ohyama River under the realistic restriction.

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We investigated effect of a fixed weir on sediment transport characteristics and aquatic invertebrate. The weir is located in an upper reach of Katsuura River (Tokushima Pref., Japan). We measured hydrologic parameters and performed quantitative samplings for benthic animals. In the rapids, component ratio of the sediment inside river bed changes in the downstream of the weir due to only the sand passing through the weir. Therefore, the species richness decreases because the habitats of benthic animals are influenced by this change. Especially, the animal having a life type of creeping is suggested to be strongly affected. However, in a mountain stream, effect of damming on eco-system in the downstream is suggested to be reduced in contrast to that in middle and lower reaches.

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Riverbed armoring is one of the most significant effects on stream communities caused by upstream dam constructions. Practically, there are some of the mitigation measures to be rehabilitated riverbed environment for conserving river ecosystem. Although the sediment additions below the dams have been applied as one of the effective measures, there are a few findings related to the physical-biological responses. The present study conducts field survey below and above the dam which are tried to be supplied gravel at its downstream, with particular references to benthic fish communities and their habitats. The canonical correspondence analysis for these benthic fish and habitat characteristics could show that the impacts of armoring and the mitigations due to gravel additions have altered the benthic fish fauna, respectively.

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For clarifying the effects of sand supply on the down stream riffle of Futase-Dam, field survey data at two locations on bed material and invertebrate composition from autumn to early spring were analyzed. Downstream site has more distinct trend to shift smaller particle size distribution after the sand supply. During winter season, from autumn to early spring, changes in invertebrate community showed different temporal pattern before and after the sand supply. The downstream site has clearer tendency not to increase in the abundance of net-spinning caddis-worms, but to increase in the species which can escape from flood disturbance. The particle size distribution before sand supply affects the change in flood season and movement of small size particle at small flood event from autumn to next spring. The possible movement time of small particle size is greatly changed with the sand supply amount and the location.

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Dynamics of invertebrate community in a gravel bed riffle has been investigated in relation to the microhabitat characteristics of boulder wake region. Two types of microhabitat, separation type (S) and hydraulic jump type (J), were constructed considering typical flow pattern around some boulders in upstream river. The relative depths (ratio of water depth to boulder height, H/hb) are 2.25 and 1.1 for S and J, respectively. Invertebrate samplings were conducted at the two type habitat and at control. Significant differences have been found not only by velocity profile but also by resilience of invertebrate according to the different H/hb. In the colonization processes, each tolerance type for disturbance of invertebrate showed different colonization patterns according to the hydraulic characteristics of each experimental microhabitat.

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In this study, the effects of sediment supply on fish habitat focused on water-column fish species are discussed. A flume experiment was conducted with boulder-bed which is modeled after armor coated boulder-bed downstream of large dams. At first, the characteristics of velocity profile are discussed, especially in roughness layer. As the gaps among boulders are filled with pebbles, velocity near the bed-surface get larger and the depth of roughness layer become thin. Secondly, an estimation of space volume which is suitable for fish cruising speed is applied to experimental result data. Finally, a consideration to construct a quantitative estimation for fish habitat with sediment supply is presented.

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This article shows how spatiotemporal patterns of geomorphological processes influence riverine habitat suitability. We conducted a case study in a middle reach of the Tenryu River in Japan and a set of interval-recording-cameras has been installed at 60m above the riverbed on the electric supply tower located in the middle of a river corridor. Firstly, we identified different types of habitat structures in a reach, such as riffles, side pools, and back waters, and analyzed characteristics of inundation processes for each habitat type. Secondly, we analyzed, at a micro scale, hardening and softening processes of habitat structures by small floods in relation to lotic and lentic inundation characteristics. Thirdly, in order to analyze erosion and deposition processes at a macro scale, we developed a 2-D model using the photogrammetric method and analyzed temporal series of the aerial photo data and 2-D-transformed data by quantifying deposited and eroded areas due to different types of floods.

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The experiments for the erosion of tall and flexible vegetation by non-disturbed large scale samples were carried out in order to establish an evaluation method for the erosion resistence of the vegitation on river levees.
The mechanism of the erosion resistence was described by the results of the experiments. Then, the framework of the evaluation method was examined by the analysis of the relation between the condition of the vegitation, such as plant species, plant height and vegitation density; and the hydraulic condition, such as water depth and surface slope.

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From technological and ecological viewpoints, it is a critical issue to control overgrowth of trees vegetated in floodplains. The authors have developed a hydraulic model which is able to describe flow and drag force in vegetated channels. The model has a two-layer structure in order to analyze both the slow flow through the vegetation and the fast flow over and besides the vegetation. The model was already confirmed to have a satisfactory reproducibility of flood flow structure through the authors' previous studies. In the present study, by collecting additional field data of trees and flood events, the model's performance in identifying areas and amounts of destructed trees was verified. The model could be a useful engineering tool for making a proper ecological management of tree vegetation and channel restoration projects.

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Vegetation in rivers causes serious problems such as increases in flood risk due to water level rise during flood. Salicaceae trees are dominant on flood plains and sand bars of rivers in cold and snowy Hokkaido. Therefore, it is crucially important to inhibit the growth of salicaceae trees for river management. While there is a problem that salicaceae trees are flourishing in the Satsunai River, one plant species in the family salicaceae, chosenia arbutifolia, is losing its habitat. Chosenia arbutifolia is registered in the red data book of Japan. Hokkaido Development Bureau, the management authority, is performing field experiments to sweep away young salicaceae, and to form fluvial bars covered with gravel by artificial flash flood with the use of snow melting water released from Satsunaigawa Dam. Authors studied the habitat situations of young salicaceae and chosenia arbutifolia before and after an artificial flash flood, and relations between hydraulic conditions and habitat of the plants.

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Forestation in rivers generally causes reduction of river flow capacity. Therefore, we have to manage a vegetation condition in the river properly. The object of this study is to forecast the vegetation condition with enough accuracy for effective management tasks. We had conducted a field observations of an annual vegetation growth rate, hydraulic conditions of wash out and lodging of vegetation, and bed deformation at Ohara area in the Asahi River from 2008 to 2013. Then, we developed a vegetation dynamic model based on the field observations. We simulated the vegetation condition at Ohara area in 2013 by using this model, and also examined the model by comparing the simulation results with an aerial photograph taken at Ohara area. The simulation results showed that the model can basically reproduce vegetation condition in Ohara area.

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An individual based dynamic model describing Nitrogen cycles and vegetation growth and succession was developed. The model is composed of tree modules, where recruitment, self-thinning, growth, defoliation/decomposition processes were simulated, herbaceous plant modules, which provide the biomass given by the soil nitrogen content, soil particle size and shading effect by trees, and nitrogen budget modules, providing nitrogen budgets through the decomposition of herbs and tree leaves. The model was applied to the observed data at Aara and Kurobe rivers'sediment bars, showing the suitable agreement. Then, it was applied for the simulation of the 20-year succession, subjected to frequent floods to see the trend of vegetation biomass and nitrogen cycle.

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This paper investigates effects of thinning and cutting-down of a vegetated channel for reducing the flood water level by using a stochastic process model. The model has been developed for statistically evaluating vegetation and flow status on a floodplain, consisting of the following four processes: (i) stochastic behavior of flow discharge, (ii) hydrodynamics in a channel with vegetation, (iii) variation of riverbed topography and (iv) vegetation dynamics on the floodplain. The river channel analyzed here is one of the vegetation overgrowth locations in the Kako River floodplains. Sensitivity of the flood water level and the vegetation overgrowth tendency is statistically evaluated in terms of the different cutting-down levels, timings and scales of the thinning by the Monte Carlo simulation of the model.

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Vegetation overgrowth on sand bars and floodplains has been a serious engineering problem for both flood protection and ecological conservation in many river basins in Japan. This paper tries to evaluate both vegetation overgrowth tendency and flood protection safety in an integrated manner for several vegetated channels in Kako river basin. The evaluation employs a stochastic process model, which has been developed for statistically evaluating flow and vegetation status on a floodplain through the Monte Carlo simulation. The result shows that the river channels with high flood protection priority are extracted from the several channel sections with the corresponding vegetation status.

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In recent years, the forestation in rivers is one of the biggest problems for river administrator. In this study, the factor analysis on the forestation about the willow and bamboo communities in rivers is conducted for the long-term and appropriate management. The twelve first-class rivers in Chugoku District are divided into small drainage basins, where a rate of trees and seven parameters: distance from a weir, total nitrogen, total phosphorus, maximum discharge divided by ordinary discharge, distance between levees divided by average water surface width, slope of the river bed and bed deformation are allocated. The correlation analysis and the cluster analysis between the rate of the trees and these parameters were performed to find the contributing factor of the forestation in rivers. These factor analyses indicate that the deformation of riverbed is a main factor for the river forestation about the willow.

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The field observations on water quality and amount of organism: detritus, attached alge and benthic animal were conducted at several points in Saba River and Ashida River of Chugoku District, which have a different characteristic of land load. An ecosystem assessment method based on exergy efficiency was applied to these rivers, and were compared with that using water quality and biodiversity of benthic animal. The result shows that the exergy efficiency can clarify the difference of the soundness of river ecosystem between the observation points of Saba River and Ashida River, and correlates with the biodiversity of benthic animal, which is not clearly related to the water quality.

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We evaluated the linkage between genetic diversity and habitat suitability index (HSI) of aquatic animals including freshwater fishes, amphibians and macroinvertebrates in the Natori River basin located at the middle of Miyagi prefecture. The HSI has been structured by variables calculated from a distributed hydro-thermal model and GIS based geographical variables. We found a strong positive correlation between genetic diversity and HSI in one caddisfly (Hydropsychidae), indicating that a prospective habitat (i.e., locality which has high HSI) might contribute to increase in genetic diversity. The genetic diversity of one caddisfly (Hydropsychidae) had significant positive correlations with the HSIs of predatory fishes and aquatic insects. This result suggests that exposures to predation pressure can enhance genetic diversity. We derived negative correlations between genetic diversity and the HSIs within niche competitors, suggesting inter-species selective pressure constrains intra-species genetic diversity.

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The present study attempts to understand the behavior of radioactive cesium-134 and -137 in sediment in urban watershed, river and lake and its association to fish contamination. For these purposes, we measured the radioactive cesium in the sediments and fishes in the watershed of Lake Teganuma. The results indicate that the decrease of radioactive cesium concentration in roads was appreciably larger than that in roofs due to the differences of non-radioactive sediment supply. The radioactive cesium in bottom sediments has increased in the downstream reach of the river and the lake. The radioactive contamination of fish were not closely related to that of bottom sediments, showing the importance of the radioactive contamination of feed environments on the fish contamination.

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Short-time heavy rainfall and high intensity rainfall events have increased in Japan. The rainfall events cause flush floods in urban area. In these floods, some rainwater intruded into underground spaces like a shopping mall and the users faced the danger of underground flooding. Therefore, it is very important to have an emergency plan for flooding. In order to make a plan, manager for underground spaces should know when and from which entrances the rainwater will flow into there. We simulate an inflow discharge by three different profiles of short-time high intensity rainfall using 1D-2D urban flood model and calculated an underground flooding using shallow flow model with structural mesh. It is found that inflow volume, start time of inflow and velocity spread are quite different in the three cases, but location of inflow is almost same. These results indicate that we have to move a quick response to the flush flood by high intensity rainfall.

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Recently, the warming on the earth advances gradually. Under such circumstances, occurrence frequency of the torrential rain increases in Tokyo. The technique of numerical prediction of the inundation is an effective tool in order to reduce damage due to such a torrential rain in urban area. In this study, the numerical prediction was conducted by using the rain data of the X-band MP radar as the first step to realize a real-time inundation forecast at the time of the localized torrential rain occurrence. Inundation in Shinjuku area that was highly-urbanized was investigated in this study by using the actual rain data that was measured locally on August 26, 2011. It was suggested that an inundation forecast could be realized soon in future.

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In this study, inundation process in lowland areas of Tokyo which is bordered by the Ara River and the Sumida River was investigated numerically. Numerical technique developed by the first author was applied in order to estimate how hazardous the urban lowland area under two different conditions. The state of inundation which is caused by a localized torrential rain was predicted. Inundation rocess in this area was also investigated numerically under the assumption that the overflow from the Ara River into this area occurred. As a result of these simulations, the time series of information about the flow path of inundated water were obtained, and the aracteristics of inundation in this area were made clear.

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Mega cities in Japan, for instance Tokyo, Nagoya or Osaka, are susceptible to floods, because they locate in lowlands which are below the flood water level of rivers. These areas are prone to floods caused by rainwater, river-water and sea-water. Some cities are fully urbanized, and underground shopping arcades and subway stations are there. These underground spaces are also flood-prone areas. In this paper, Tsunami flooding in underground space caused by the Nankai Trough Great Earthquake is discussed by using calculations of surface and underground inundation. Results show that entrance location of flooded water intrusion by Tsunami flooding is quite different from a pluvial flooding case and that the amount of inflow is very huge. This means that counter measures for underground inundation should be planned for each kind of flood disaster.

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In this paper, an inundation .ow in the Matsugase district, Sanyo-Onoda City, during the 2010 July torrential rainfall event was analyzed. Topographical data of this area were measured by aerial LiDAR survey. The DEM obtained by the LiDAR survey was veri.ed by .eld survey data measured by RTK-GPS. A shock-capturing shallow water .ow model with a .ne calculation grid (two to 5 meters in resolution) was utilized to represent inundation .ow in the inundated area. The calculated water depth was compared with the water records. The characteristics of inundation .ow, especially the e.ect of the embankments in the inundated area, and those relation to local damage were discussed. E.ects of embankment rise and reduction of energy loss due to a bridge were evaluated.

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The northern part of the Yamaguchi Pref. was attacked by record severe rain storm called Yamaguchi-Shimane heavy rain, in which the maximum 1 hour rainfall was over 130mm and total over 350mm at the Susa weather station on July 28th, 2013. This paper describes the characteristics of the flood disaster in Susa River basin. The highest water depth reached to 2m and was beyond that expected in flood hazard map there. 4 dike breaks occurred by the flood. According to our flood simulation, inland flooding contributes to the flood more than river water flooding.

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This paper analyzes the flood situation of the Yoshino River in the Meiji era. From the result of the analysis of the 1911 flood of the Yoshino River in the Meiji era, how to raise the levels of disaster reduction technologies and skills of the flood-prone community are examined. The flood hazard map which the result of the analysis of the past floods is applied will help the planning of the evacuation of the people from the flood-prone community.
It is shown that the levels of disaster reduction technologies and skills of a present-day flood-prone community may be raised, and the damage from a flood may be able to be reduced by analyzing the condition of the past floods in detail.

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Massive flooding in the Chao Phraya River basin, Thailand, in 2011 has caused great damage on the most parts of the country. In order to identify inundated areas due to large-scale floods like that in 2011, analysis of the satellite data is an effective way to understand both overall and detailed situation of inundation. In this paper, we proposed a method to estimate inundated areas utilizing data from two kinds of satellite, HJ-1A and ENVISAT, with different resolutions and spectral bands. In this method, the water surface in some local areas was extracted from HJ-1A data, by which the threshold value of ASAR image of ENVISAT was adjusted so that the inundated area matches with the result of HJ-1A. Then, the inundated area in a larger sample domain was estimated by the ENVISAT data. The result indicated that the inundated areas spread over paddy fields along with time, but they were limited to these low elevation zones. In another domain, we found that inland areas located far from rivers were largely inundated, which is probably due to the water storage in paddy fields, while previous estimation did not detect these areas.

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Hydroelectric power is sustainable and a pure domestic energy with low CO2 emissions. It is necessary to promote a further enhancement in the future. While it has been difficult to construct a new dam due to the environmental impacts and fiscal tightening, retarding basins have been recognized as leading plans for flood control in recent years. Because basically there is no submerged houses in basins and they are environmentally friendly. In this study, we recognize retarding basins are utilized not only for flood control but for water resources; enhancing effect of hydroelectric power is one of efficient and significant ways of their roles. This paper identifies the potential for the power development to examine increased power of the downstream power plant with assumptions of discharging water in accordance with the conditions. Experimental results from the Shinano River are being used as numerical model simulations to provide insights here.

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This study investigates small-scale hydropower generation utilizing the dam water currently released solely for maintaining the river discharge. Toward improving such small-scale hydropower generation, a method for flexible operation of dams is proposed. In flexible operation, a portion of the flood control capacity is allocated to water storage. When a flood is forecasted, it is necessary to release that amount of water to recover the dam's flood control capacity. In conducting such release, accurate forecasting with sufficient lead time is desirable. This study examined the possibility of determining the necessity of water release ahead of forecasted rainfall by estimating the amount of water flowing into the dam reservoir based on forecasted cumulative rainfall computed from numerical weather prediction models (RSM and GSM).The examinations clarified that by employing the proposed method it would be possible to secure water which is about 8 times that currently used for power generation.

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The Watarase retarding basin which is located in the lower Watarase River has an important role on the flood control in the Tone River. The design flood discharge of a period of about 30 years hereafter in the Tone River is 14,000m³/s at the Kurihashi of the Tone River.
In this paper, the flood control functions of the Watarase retarding basin are investigated by the flood flow analysis when the peak flood discharge under various discharge hydrographs is about 14,000m³/s at the Kurihashi in the Tone River. It is shown from the calculation that the Watarase retarding basin reduces peak flood discharge and delays the peak occurrence time at the Kurihashi by storing flood discharge flowing back to the Watarase River from the Tone River. Furthermore, some remarks are given for the enhancement of flood control functions of the Watarase retarding basin.

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The lower Shinano River is known as a typical low-lying river in Japan. The river system comprises several tributaries, a branched river and a non-embankment area. The flood propagation and bed variation in such a complex river system have not been cleared from the total views of the river basin.
In this paper, we develop the numerical model applying the BVC method and 2D bed variation using observed water surface profiles during 2011 flood in the lower Shinano River with complex river systems. We evaluate effects of the pumping drainages, inundation in non-embankment area and river improvement works on the flood control functions by using the developed numerical model.

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In Japan, safety degree against flood is said to have increased by river improvement. However, frequently flooded areas still exist. This means that frequently flooded areas has some characteristics which prevent river improvement. Therefore it is important to clarify the distribution and characteristics of frequently flooded areas for thinking about future river improvement plans.
In this research, we clarified the distribution of frequently flooded areas in Japan, using flooded area maps. As a result, it is clarified that most frequently flooded areas exist in narrow valley plains, and the reason why such areas are still flooded is difficulty of embankment.

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An impact assessment of a risk of water-related disaster under a changing climate has been highly concerned recently. For the assessment, it is important to examine a change of the magnitude of inundation disasters as well as that of flow regime under various climate conditions. To make an ensemble assessment of the magnitude of inundation disaster, systematic and computational cost-effective simulation is required. In this research, a flood-inundation model which nests a distributed rainfall-runoff model and is applicable to any part of a basin was developed. The developed model was successfully applied to the Shirakawa River catchment in Kyushu, Japan.

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