Almost all irrigation systems in Japan have, until now, been operated through supply oriented operation based on upstream control of open channel trunk systems that support paddy field cultivation. This study proposes an existing system renewal method for existing trunk systems that will permit response to new irrigation water demand trends and prevent problems with river management by introducing downstream control concept at appropriate locations on the system. The system was verified by carrying out a one-dimensional unsteady flow simulation. Based on the results, the concept of the design of intermediate regulation facilities and specific installation methods intended to effectively use the channel storage of the existing system were organized in response to problems encountered in the field.

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 The objective of this study is to evaluate effects of flood to agriculture and relationships between flood magnitude and agriculture productivity. By using a phosphorous transport model, potential cropping times was calculated limited by phosphorous, inundation water and both phosphorous and inundation water. Conclusions are as follows: 1) Current area ratio of paddies to reservoirs has high productivity in a middle magnitude flood year. 2) A large flood year has an advantage on obtaining phosphorous at the flood plain. 3) Differences of the potential cropping times limited by inundation water in flood magnitude is relatively small compared with phosphorous. 4) Although differences of the potential cropping times limited by both phosphorous and inundation water in flood magnitude is small, potential productivity through the area is high in a large flood year because of a huge inundation area. 5) Potential cropping times limited by both phosphorous and inundation water can express variations of harvested area (r=0.68).

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 Ensemble hydrological prediction is considered useful for reservoir operation for water supply, which need to take long-term hydrological prediction into account in general. However, they have not yet been widely considered in the actual reservoir management, because it is still unclear how to effectively utilize ensemble hydrological predictions considering their uncertainty. In this study, a method to artificially generate ensemble inflow predictions with designed error structures is developed. Monte Carlo simulation of long-term reservoir operation is then conducted by use of the ensemble hydrological predictions generated by the proposed method in order to clarify the effectiveness of reservoir operation for water supply considering ensemble hydrological prediction with various error structures.

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 To design integrated flood risk management, flood risk assessment based on the economic damage is essential. In previous studies, the authors have developed a method to estimate a flood risk curve considering spatio-temporal distribution of rainfall by applying the Synthesis Probability Method (SPM) that estimates probability function of annual maximum flood peak discharge (AMF). Recently, the SPM was improved by introducing the relation between total rainfall and the duration time, and the estimated probability distribution of AMF with the improved SPM showed a better agreement with the probability distribution of observed AMF. This study extended the improved SPM to flood risk curve development and estimated a flood risk curve of the Ayabe city in the Yura-gawa River basin.

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 The purpose of this study is to clarify the effect of uncertainty in the rainfall-runoff process. Though we have performed runoff analysis deterministically in the past, the uncertainty in the rainfall-runoff process is quantified stochastically through the introduction of the theory of stochastic process. We purpose the theoretical framework to evaluate the uncertainties using the relationship among Langevin equation, stochastic differential equation (SDE) and Fokker-Planck equation (FPE), because the lumped rainfall-runoff model is described by ordinary differential equation. That is, it is attributed to the similarity of structure between the lumped model and Langevin eq. or SDE. As a result, we provide a new perception into decision-maker in flood. Moreover, we theorize a new framework regarding reliability analysis with the distribution of water level as external force and the failure probability of levee as resistance.

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 The purpose of this study is to clarify the comparative study of areal rainfall of rain-gauge data and high-resolution radar data in medium and small river basins. This analysis used QPE of C-band radar and X-band MP radar as areal rainfall of radar data. As estimated of areal rainfall of rain-gauge data, this study has divided numbers of each watershed by Thiessen method.
 As a result of several analyses, areal rainfall of each radar data was similar to that of rain-gauge data. Areal rainfall of radar data haven't depended on domination area of a rain-gauge station. Areal rainfall of X-MP data wasn't difference from that of rain-gauge data in less than average altitude 300m of sub river basin.

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 Recently, there has been considerable interest to improve the flood control function of the dams by prior releasing. Carrying out prior releasing has the risk in terms of water utilization. Therefore, it should be taken into consideration that releasing larger amount of water than rain gives water shortage. In this study, we examined the possibility of prior releasing using accumulated rainfall forecasted by Japan Meteorological Agency. Concretely, we investigated that it could estimate the accuracy of forecasted accumulated rainfall based on Global Spectral Model (GSM) by adding the information of spreads calculated by One-week Ensemble Prediction System (WEPS). As a result, we found that the accuracy of forecasted accumulated rainfall based on GSM relates to the spreads calculated by WEPS in case of typhoon. The study results further suggest that it will be possible to improve the flood control function of the dams by prior releasing using forecasted accumulated rainfall.

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 Jakarta has experienced many floods in the past, and those floods resulted in not only human casualties but also economic damages. In this paper a rainfall runoff and flood inundation model was applied to the 2013 flood event of the Ciliwung River basin and Jakarta by using radar rainfall information as the input. The applied model relatively well reproduced the flood inundation situation in Jakarta. As the results of analysis, we concluded that the shortage of capacity flow in the lower Ciliwung River contributed 6.7%, the shortage of capacity flow in other rivers 72.9%, and the urbanization and the land subsidence 20.4% of the total flood inundation volume in Jakarta. Furthermore, it was found that the land use change from 1983 in the target areas contributed 38% of the total flood inundation volume.

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 A retarding basin is one of the most effective countermeasures to mitigate existing downstream flooding problems. Effectiveness of the basin is strongly dependent on design of an overflow levee. Experimental works have been commonly employed for the overflow levee design. The primary objective of this study is to demonstrate that a numerical model, which are comprised of the distributed hydrological model, the 2D unsteady flow model based on flux-difference splitting scheme as well as unstructured finite-volume method, and operation of drainage system, is an effective tool to evaluate the stage-discharge relationship of the Mutabe retarding basin in the Rokkaku River under the given conditions of rain-fall and tidal level of the Ariake Sea.

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 We examined relationship among specific discharge of flood and rainfall, geomorphology, land use and geology to reveal the influence of watershed characteristics on flood discharge. As a result of a correlation analysis, hourly rainfall depth was the most major factor to determine the flood discharge. Among the geomorphological factors, form factor and topographical gradient were major factors of increasing flood discharge. However, the effects of these factors differed by flood scale. In the land use factor, there was no clear relationship between broadleaf forest and flood discharge for each flood scale. Whereas, coniferous forest was factor to increase flood discharge at low frequency event.

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 Flood management is more and more adopting a risk based approach. This paper presents an outline approach and methodology for assessing flood hazard and social vulnerability and whereby, to deliver flood risk curve (FRC) of selected frequencies of 10%, 5%, 2% and 1% and then social annual risk in terms of people at risk, injuries and fatalities.
 An important point of the analysis process is to modify vulnerability factors to include not only direct and tangible issues but also indirect and intangible ones to be applicable in rural area of the developing countries as in Central Vietnam. The overall objective of this study is to produce a quantitative estimation of the human safety risk caused by flood disaster in the years to come.

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 The potential damage cost of flood and storm surge in whole Japan was estimated quantitatively. We also estimated the potential damage cost on flood and storm surge in compound disaster that two disasters happened in the same time. The error of damage cost on compound disaster was evaluated. We extracted larger risk disaster than others in each Japanese prefecture.
 The error of damage cost estimated on compound disaster was similar to change estimation by using future scenarios and GCMs. The potential damage cost of flood in whole Japan was 1.04 trillion USD, storm surge was 0.52 trillion USD and compound disaster of flood and storm surge was 0.88 trillion USD. Out of 46 prefectures, the damage cost of flood was larger than others in 37 prefectures. Additionally the damage cost of storm surge and compound disaster were larger than others in 1 and 8 prefectures in Japan, respectively.

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 Heavy precipitation event occurred for 8 to 10 September, 2015, over Tochigi and Ibaraki Prefectures caused an over-topping and an outburst of the left levee of Kinu-river in Wakamiyato and Misaka-cho districts in Joso city, Ibaraki prefecture around 6am and 1pm on 10 September, respectively. This precipitation event was caused by clustered linear rain bands influenced by Typhoon Etau (No 18) and Kilo (No 17). This paper aims to report our field investigations held on 10, 15, and 19 September, and to raise a couple of discussions for further improvement of flood control and river basin management in Japan.

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 Most of the past studies on the analysis of landslides are evaluated by determinism. It means the analysis are only two results, stable and unstable. However in the real environment, there are a lot of uncertainty factors that would affect the occurrence of landslides. In the study, the authors consider the hydrological uncertainty and the variability of soil parameters of the slope to propose a new method for the risk evaluation of landslide induced by rainfall. The uncertainty has two types, one is the limitation of observation or experiment and the other one is and the error of data. For the landslides analysis, the uncertainty analysis can be separated by the external force from rainfall and the resistance force of slope stability. In considering the external force, it would focus on the analysis the relationship between rainfall and storage by using storage function model based on the uncertainty rainfall and the analysis of slope stability would consider the deviation of the soil parameters. Finally the occurrence of landslides can be summarized as like the risk evaluation during rainfall based on the stochastic process theory.

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 A landslide and debris flow disaster information distribution service was developed to raise resident's awareness and enhance safe and quick self-evacuation. The information distribution service provides the information on the occurrence area of landslide and debris flow directly to the users. The landslide and debris flow occurrence is estimated by using the integrated information of the spatial and temporal rainfall distribution measured by the X-band multi parameter Radar, landslide and debris flow hazard expected area and topographic factors such as slope. The landslide and debris flow disaster information service is distributed by using an application software which works on Android and iOS base smartphones and PCs. The applicability of the predicted landslide and debris flow occurrence area was discussed by using the sediment disasters occurred in Tochigi prefecture in September 2015. The predicted alert areas have good agreements with the landslide and debris flow occurred area in Tochigi.

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 In sediment disaster, not only crucial hazards but also relatively small scales of multiple hazards make evacuation behavior dangerous. In this study, the integrated sediment runoff model connecting a landslide model and water-sediment transport model was employed to the actual sediment disaster caused in Tanba city, Hyogo, Japan. The temporal and spatial variation of risk was estimated in 3 groups of multiple hazards (rainfall-related, landslide-related, and flood-related hazards). The occurring times of landslide-related and flood-related hazards were agreed with the disaster report. This method can also estimate the risks in advance using the virtual rainfalls. In this paper, the risks in 3 rainfalls which have different timing of rainfall peak were estimated. The results showed that the difficulty of evacuation was not equal because the progress process of each hazard group was different according to rainfall characteristics.

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 We developed a victim data base (“2004-2014”) for heavy rainfall disaster events in Japan from 2004 to 2014, and classified the 712 victims. The purpose of this study is to analyze the characteristics of victims of the September 2015 heavy rainfall disaster in the Kanto and Tohoku districts (“Kanto Tohoku 2015”) and compare them with those for “2004-2014.” Characteristics of victims of “Kanto Tohoku 2015” were as follows: 1) 88% of the deaths were by flooding, 2) 88% of the deaths were outdoor, 3) 25% of victims were elderly, 65 years or older. “2)” is similar to the ratio of deaths by flooding in “2004-2014.” The ratio of “3)” is lower than that for “2004-2014.” The number of “Kanto Tohoku 2015” victims was 8: an unusually large number for recent heavy rainfall disasters in Japan. On the other hand, a dike break on the Kinu River in Joso City, Ibaraki prefecture, washed at least nine houses away. There were more than ten inhabitants in the houses, but all were saved. Worse weather probably leads to more deaths.

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 In this study, we compared the questionnaire data related to evacuation behavior, obtained in Hidaka city, Hokkaido in 2014 to another questionnaire, obtained in the same area right after the Great East Japan Earthquake. Moreover we analyzed the adaptation of disaster prevention awareness from those data. Then, we found that normalcy bias prevented residents from becoming active for disaster prevention. After that, we classified awareness of residents by 5 phases from questionnaire data and found that existence of close people made normalcy bias suppress. Additionally, we also found that the psychological closeness with the close people was one of the suppression factors for normalcy bias.

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 Local governments publicize flood risk information aiming to mitigate future damage and loss; however, the way in which residents recognize and understand them is unclear. Several researches by analyzing land prices have quantified residents' level of flood risk understanding, with an assumption that land prices are influenced by the perception of flood risk levels. Assuming that residents' perception of flood risk increases when flood occurs is natural; however, earlier studies have not yet succeeded to identify changes between flood risk indices and land prices by using the time series analysis.
 This study utilized land transaction prices of Kanda river basin, and found that the prices dropped immediately after the Great East Japan Earthquake in the high inland flooding risk area.

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 At the time of huge river flooding, it will be concerned to become broad and deep inundation. If there is no high-rise buildings in the region, it is difficult to secure evacuation place. In this study, we have defined “the survival mound” as the embankment for evacuation against the disaster. And we suggested the survival mound with river levees in these region.
 It is found to be useful for the easiness of evacuation, the accessibility to the outside area, the safety, and the cost reduction of construction. In order to understand the effect of the easiness to evacuate, we evaluated a completed percentage of the evacuation by evacuation simulation. In conclusion, it was found that “the survival mound” is effective approach in the target area.

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 In order to make clear the awareness in evacuation behavior in Hokusatsu heavy rain disaster, we conducted a questionnaire survey. The questionnaires were distributed to local sections where many rescuees reside, and the answers were analyzed by regarding the rescuees as the persons who could not determine an adequate behavior in a risky situation. As a result, it was clarified that many rescuees did not evacuate because of the action of normalcy bias and cognitive dissonance. In addition a possibility was suggested that the evacuation information for disaster might not be understood sufficiently by some residents and that it might delay the timing of evacuation.

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 A physically based simulator for sediment related disaster has been studied to provide information for warning and evacuation system. The simulator which is fed with rainfall data, elevation data and surface soil information predicts subsurface flow, overland flow, river discharge, initiations of shallow landslides and debris flow, and it is applied to the storm event occurred on 15th Oct. 2013 at Ookanasawa basin of Izu Ohshima Island. The results suggest that the simulator predicts the target phenomena such as river flows, initiation of shallow landslides and debris flow in this basin. The simulator is used to find a critical rainfall condition for initiation of shallow landslide and debris flow using various rainfall. The critical curve which is derived from the relation between simulated shallow landslides and rainfall conditions is confirmed by past disaster records.

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 An appropriate evacuation is necessary to reduce damages due to flood disaster. However there are little information for underwater walking in evacuation. In this study, we conducted the laboratory experiments for walking speed in water under various conditions. For this, we set totally 49 cases for water depth and velocity, and several surrounding environment for which kinds of shoes, turbidity of water and light conditions are changed. The results indicated that the inverse correlations between walking speed and hydraulic parameters were obtained. The walking speed with the environmental conditions were 50 - 60 % of it without the environmental conditions. Critical conditions of underwater walking were quantitatively evaluated under various hydraulic and environmental conditions.

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 In this study the flood inundation risk map was proposed as a new risk evaluation method reflecting spatial distribution of inundation probability. At first many scenarios were supposed to reflect various probabilistic uncertainty about broken point of the embankment and its degree. Then numerical simulations of flood inundation based on the scenarios were carried out. The maximum inundation depth map and the inundation probability map were created from the results of all scenarios. Finally the flood inundation risk map was developed by shading the maximum inundation depth map according to the inundation probability.

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 Severe flood inundation disaster happened in Ogurisu area, Kyoto City, on September 16, 2013. During that disaster the pumping station stopped its function due to an accident, which have caused severe inundation disasters in the surrounding area with more than two meter inundation depth. In this study, effects of that pump failure on the inundation disaster are evaluated through numerical simulation. From the simulation results, it is clear that the pump failure had affected the Ogurisu area significantly comparing with the simulation results with normal pump function. Finally we present a simulation result under the assumption of complete disorder of pump function, which shows much severer inundation damage, as a suggestion of preparatory hazard map for inundation disasters due to heavy rainfall considering one of the worst situations with pump failure.

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 In this study, similarities and differences of psychological processes were investigated based on the questionnaire survey which was carried out in 2 target area; Hirono town where it was affected by the Great East Japan Earthquake and Tosashimizu city where it will be further risk by the Nankai Trough Earthquake. The analysis was as follows: (i) Tsunami Disaster Prevention Awareness is unaffected real experience of large scale disaster, (ii) Tsunami hazard map is one of effective method for strengthen Disaster Prevention Awareness even though elder people, (iii) A rising “Behavior” directly connect to “Will for Evacuation” as countermeasure against next disaster.

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 There are more than 640 subway stations in Japanese cities. These stations make up tunnel networks as seen in Tokyo, Nagoya and Osaka. In this paper, subway inundation in Osaka is discussed on the basis of numerical result in a case of extreme pluvial flooding. In the previous work, it was found that about 80 percent of intruding flooded water into the mega-underground mall comes down to subway tunnels. In this paper, it is the objective to investigate how the intruding water spreads across the subway network, and how is the leading time for safe evacuation at each stations. From the result, flooded water broadly spreads across in the subway network and the leading time is not enough for safe evacuation from subway stations.

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 Japanese cities have many underground spaces such as subway and shopping malls. These cities locate in lowland of coastal zone near river mouths and are prone to extreme floods. The vulnerability of underground spaces to extreme floods are treated in this paper by using the results obtained by numerical method in densely urbanized area, Osaka, Japan. Pluvial, fluvial, storm-surge and tsunami flood cases were calculated. It is found that up to 60% of flooded water intrude into underground spaces if no counter measures were taken. Inundation depth and area in the underground shopping mall are different in the four types of extreme floods, and the flooded water enters into connected subway stations. This means that administrators of underground space have to make different counter measures for each type of extreme floods.

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 Recently, localized torrential rain occurs frequently. In order to clarify inundation risk of Tokyo metropolitan area, numerical simulation of urban inundation was conducted. In this study, following three investigations were conducted. First, numerical simulation of inundation event which occurred on June 29, 2014 was carried out by using the actual rain data which was obtained by X-band MP radar. Based on this result, validity of this prediction technique was confirmed. Another investigation was done to find out the inundation risk of each entrance gate to judge whether the inundated water on road could flow into the space of subway stations through it. We specified such entrances gate. And then, we attempted to understand the expanding process of water in the subway tunnel by another numerical computation.

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 Recently, the serious inundation damage due to local heavy rain has increased. This study treated the inundation damage due to heavy rain in Kasugai city, Aichi prefecture, JAPAN that occurred on September 20, 2011. To make clear the inundation situation and discuss the countermeasures, the numerical simulation model was developed for the complex water behavior of overland flood flow, river flow and sewer flow. The detailed model of the water behavior in overland, river and sewer system is indicated. From analysis results, it was shown that the area with high inundation water depth of analysis results are good agreement with the actual inundated area. This analysis results shows the validity of this analysis model. Moreover, the inundation analysis method in consideration of the origin was developed by using the T-SAS. This analysis can show the transport of rain water separated by space or time. Therefore, it is possible to clarify the origin of the water gathered in the inundation area. Such obtained knowledge of transport of rain water is available for discussion of effective measures.

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 A heavy rainfall generated by a stationary front in rainy season attacked northern Kyushu district in July 3-14, 2012. Extreme rainfall event was recorded particularly in Aso city of Kumamoto prefecture during 2 am-8 am of July 12, which could occur in a return period of 130 years statistically. It induced flood inundation and/or debris flow disasters in this river basin, and resulted in the number of killed or missing people 25.
 In this paper, picking up the Tatsuta Zinnai 4 district, where is most vulnerable one to flood disasters in Kumamoto city, we investigated the flood inundation in detail by hydraulic model experiments and clarified the main factors that affect death or injury to people during floods, which include flow velocity, flow depth, and the degree to which people are exposed to the flood on evacuation routes.

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