Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

This study examined how urban river restoration processes can cultivate a sense of ownership and contribute to community-engaged climate change adaptation, focusing on the case of Okazaki City, Japan. The research employed a qualitative approach, analyzing local documents and interviewing ten key volunteers of ONE RIVER, a local citizens’ group. The case study demonstrated that local activities began with utilizing the river area and subsequently expanded to encompass community-based adaptation, including sustainably maintaining the river environment across the entire watershed. Additionally, it was observed that a sense of ownership over climate change adaptation was cultivated in stages through local activities. The volunteer members first recognized the natural appeal of the diverse river ecosystem services with the rich experiences of the natural dynamics, such as seasonal scenery changes and the presence of living organisms. Secondly, they perceived a hidden connection between the river environment and one’s own life by fostering relationships with a diverse range of stakeholders. Our findings indicated that urban river restoration would benefit community-engaged climate change adaptation by revitalizing the connection between urban society and rivers and building reasonable government-community relationships with local participation. The case study also suggested that considering sociocultural differences is crucial for evaluating the benefits of urban river restoration.

DOI： 10.3389/frwa.2025.1537235

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> It is important to evaluate the probability of discharge in a water environment since the discharge is effected on the development and occurrence of hypoxia in the coastal area. However, in the previous studies, discharge observational data have uncertainties by the data-scarce and observation method relative to precipitation observational data. Therefore, few studies have evaluated the probability of discharge. Thus, this study aims to reveal the optimal discharge probability distribution in each river basin with d4PDF by developing the runoff model which is considered the inundation based on the current river channel in the main eight river basins in Kyushu. As a result, it is found that the goodness of fit of the Gumbel distribution which is used for precipitation distribution evaluation widely is also high in the discharge. However, it is suggested that the evaluation of optimal probability distribution in each river basin is important since there is the case that it is different in a river.</p>

DOI： 10.2208/jscejj.24-16138

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> The impact of the heavy flooding caused by the historical heavy rain in July of 2020 on the Kuma River was evaluated in terms of the transition probability of “operation method during an extraordinary flood for disaster prevention” due to climate change, focusing on the existing storage-type dam, Ichifusa Dam, and the gate-controlled flood mitigation dam under construction, Kawabegawa Dam. The evaluation was conducted using a dam model incorporating an outflow model and dam operation rules, targeting the inflow volume to simulate the outflow discharge and water level in the dam. Additionally, the probability of excess floods at the downstream point of both dams, Hitoyoshi, was also evaluated. Measures to prevent abnormal floods and excess floods were verified, including the redevelopment of Ichifusa Dam, increasing the constant outflow discharge of Kawabegawa Dam during flood control operation, and creating reservoirs within the watershed areas. As a result, the quantitative evaluation of the changes in the transition probability of the operation for both dams and the probability of excess floods at Hitoyoshi due to climate change was possible. Furthermore, it was demonstrated that the redevelopment of Ichifusa Dam has a significant effect and, in combination with reservoirs, there is a possibility of achieving the target safety level under all climate conditions.</p>

DOI： 10.2208/jscejj.24-16064

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>本研究では，気候変動を踏まえた治水計画における技術的課題の一つとして，5km解像度のd4PDF降水量を十分に活用するため，バイアス補正手法による流量推計結果の差異に着目し，点単位の補正結果をティーセン分割により用いる従来の方法と新たに提案された空間内挿によるメッシュ単位のバイアス補正手法による流量推計が，どのように異なるかという点について分析を行った．その結果，流域平均雨量に対しては10～30mm程度，ピーク流量では5～10％程度の差が生じ，特に中程度の降水量・流量において相対的な誤差が大きい傾向が見られた．一方で空間分布を考慮することによりティーセン分割では捕捉できない降雨の分布を反映することによる利点も見られた．</p>

DOI： 10.11532/river.31.0_331

CiNii Research

Authorship：Lead author,　Last author   Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>本研究では将来河川流量推計で広く用いられている地球温暖化対策に資するアンサンブル気候予測データベース(d4PDF)のバイアス処理に関して，著者らが開発し広く利用されている従来の観測点単位の手法を，d4PDFのメッシュ単位の空間分布を持つデータへと拡張する空間補間技術を提案し，その有効性について検証した．検証においては流域に1地点しか参照値となる観測地点が存在しない流域を題材として，手法による降水量および流量推計結果の差を推計した．降水量の検証結果からは地形性降雨など参照値が限られる地点における再現性には課題を残すものの，単一の降雨を用いる場合と比べて多様な空間降雨パターンを再現することが確認できた．流量推計においてもこの降雨の空間パターンの反映により単一の降雨を用いた場合と大きく異なる流量が推定されることが示された．本研究成果は従来単一の降水量のみを使うしかなかった中小河川において空間分布を考慮した気候変動下での河川流推計を可能とするものであり，気候変動適応に資することが期待される．</p>

DOI： 10.11532/river.31.0_349

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>国土技術政策総合研究所は，全国版d4PDFダウンスケーリングデータについて，日降水量データと日平均気温データを対象に，全国109水系の流域内及び近傍の観測データを参照データとして，Dual-Window法によるバイアス補正データを開発した．また，このデータを，2025年2月にDIASで公開した．これは，d4PDFの全国をカバーする初の力学的ダウンスケーリングデータのバイアス補正データの開発・公開であり，本研究は，このデータのディスクリプションとして，開発手法と基本的なバイアス量を記述したものである．データの公開に加えて，これらを，気候モデルの開発者，バイアス補正法の開発者，他のユーザーと共有することで，技術の発展と気候モデルの利用促進という好循環への貢献を目的としている．</p>

DOI： 10.11532/river.31.0_421

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> Many studies have been conducted on the impacts of global warming on oxygen dynamics in estuaries like Osaka Bay. Although they focused on water temperature and changes in heavy rain, studies on future summer drought impact are rare. In this study, we performed numerical simulations to assess the impact of future changes in summer drought on the oxygen cycle in Osaka Bay. We used database for Policy Decision making for Future climate change (d4PDF) and prepared 21 samples based on the rainfall pattern before the drought season, as the input for a 3-D hydrodynamic and water quality model to predict the extent of hypoxia during present and future drought conditions. The results suggest that the combined impacts of temperature rise and discharge decrease during summer drought expand the volume of hypoxia, while the discharge decrease during summer drought itself may slightly reduce the volume of hypoxia. The decrease in discharge leads to less oxygen consumption due to less organic matter decomposition and increases dissolved oxygen in the middle layer of the inner bay. Meanwhile, the temperature rise decreases oxygen solubility, resulting in a decrease in dissolved oxygen throughout the coastal area. The impact of the decrease in discharge during summer drought on the oxygen cycle is smaller than the impact of the temperature rise.</p>

DOI： 10.2208/jscejj.25-17262

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p> Precipitation from two ensemble climate projections with different spatial resolution were compared. Comparisons were conducted for five river basins in Kyushu, Japan. Additionally, the river discharge estimated from numerical experiments using bias-adjusted precipitation as input values was also analyzed. The results indicate that the 20-km resolution experiment reproduced a variety of peak discharge at the same rainfall due to the large number of ensemble experiments. In contrast, the 5-km resolution experiment reproduced the designed peak discharge in each basin with a limited number of ensemble experiments, thereby demonstrating the advantages and disadvantages of using the 5-km resolution experiment in the evaluation of extreme discharge.</p>

DOI： 10.2208/jscejj.24-16134

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p>令和元年に公表された「気候変動を踏まえた治水計画のあり方提言」の中で将来気候下での降雨変化倍率が示され，これを現行の計画対象降雨量に乗ずることで気候変動の影響を見積もることが基本とされている．しかし，実績降雨波形を引き伸ばす方法が将来気候下での河川流量を評価するために十分であるかは不明である．そこで，本研究では，将来気候下における降雨パターンの変化と河川ピーク流量変化の関係を明らかにするため，茨城県主要河川流域を対象に，d4PDFの降水量から整備計画規模相当降雨を抽出して流出計算を実施した．各河川の治水基準点上流における計画降雨継続時間の年最大降雨イベントをバイアス補正済み降水量から抽出し，100年確率降雨量を推定した．抽出した計画規模相当の降雨イベントを用いてRRIモデルによる流出計算を実施し，治水基準地点における河川流量を評価した．その結果から，将来気候下においてはピーク雨量や強雨の継続時間だけでなく，降雨波形の特徴が変化することが明らかになり，これを治水計画の立案において考慮する重要性が示唆された．</p>

DOI： 10.11532/river.30.0_369

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Language：Japanese   Publisher：The Japanese Society of Irrigation Drainage and Rural Engineering  

<p>石垣島におけるSDGsの達成に向け，石垣島の将来像と関係する現在の社会課題を，高校生を含む住民参加のワークショップから抽出することを試みた。将来像を描くには各年齢層の意見を偏りなく抽出することが重要である。よって，高校生を参加者に含む議論の場を設定し，高校生の意見が議論に及ぼす影響や，高校生自身が議論を通じて，どのような変化や気づきを得られたかを分析した。結果から，高校生を含む参加者が参加前より広い話題への興味を触発されたこと，高校生の発言が議論の拡大・発展の鍵となっていたことが示された。同様の議論の場の設定は，農業農村工学がより強くSDGsに貢献するための有力なツールとなる可能性が示された。</p>

DOI： 10.11408/jjsidre.92.4_241

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p> In the case of instituting river planning, it is important to determine the exceedance probabilities based on long-term observational data. However, there are many data-scarce basins in the world, such as in developing countries. Although reanalysis data has been used instead of observation data in these areas, it has biases between the observational data since the spatial resolution of reanalysis data is low. In this study, we developed a statistical correction method for reanalysis data (ERA5) with four different calibration periods (rewind to 5, 10, 15 and 20 years from the latest year of observation data) and created long-term pseudo hydro-meteorological data such as precipitation and temperature. In addition, we examined the type of probability distribution and the number of years for the calibration period that should be applied to create highly accurate corrected data. As a result, it is found that river flow indices based on ERA5 which was applied to the statistical correction method are the almost same relative to the observational data. Furthermore, the corrected data which applied the statistical correction method with the gamma distribution developed based on over 15 years of observational data in the calibration period revealed the high accuracy river flow indices and annual exceedance probability flow based on observational data.</p>

DOI： 10.2208/jscejj.23-16117

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Authorship：Last author   Language：English   Publisher：IOP Publishing  

Two methods exist to address the degree to which past extreme events and associated disasters will be intensified due to climate change: storyline approaches and risk-based approaches. However, the risk-based approach applied to weather similar to the target event (typhoons, a stationary weather front,...etc) becomes theoretically similar to the storyline approach. We examine this theory for the climate change impact of a real event, Typhoon Hagibis, which caused devastating flood damage to eastern Japan in 2019, while focusing on basin-averaged accumulated rainfall (BAAR) in major eastern river basins. A risk-based approach was conducted to determine the future change of BAAR by calculating the quantile change corresponding to Hagibis from the probability distribution of typhoon-induced events in a large ensemble climate simulation dataset database for Policy Decision-making for Future climate change (past, +2K and +4K future climates). A storyline approach for Typhoon Hagibis was realized using a pseudo global warming (PGW) experiment with a 5 km non-hydrostatic model. The projected BAAR in the two approaches were consistent for all target basins, supporting the robustness of the calculated changes in extreme catchment precipitation. This presents an important practical benefit: one can assess future climate change impact on a past symbolic event using either PGW experiments or large ensemble climate projections for the target weather.

CiNii Research

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

Two methods exist to address the degree to which past extreme events and associated disasters will be intensified due to climate change: storyline approaches and risk-based approaches. However, the risk-based approach applied to weather similar to the target event (typhoons, a stationary weather front,…etc) becomes theoretically similar to the storyline approach. We examine this theory for the climate change impact of a real event, Typhoon Hagibis, which caused devastating flood damage to eastern Japan in 2019, while focusing on basin-averaged accumulated rainfall (BAAR) in major eastern river basins. A risk-based approach was conducted to determine the future change of BAAR by calculating the quantile change corresponding to Hagibis from the probability distribution of typhoon-induced events in a large ensemble climate simulation dataset database for Policy Decision-making for Future climate change (past, +2K and +4K future climates). A storyline approach for Typhoon Hagibis was realized using a pseudo global warming (PGW) experiment with a 5 km non-hydrostatic model. The projected BAAR in the two approaches were consistent for all target basins, supporting the robustness of the calculated changes in extreme catchment precipitation. This presents an important practical benefit: one can assess future climate change impact on a past symbolic event using either PGW experiments or large ensemble climate projections for the target weather.

DOI： 10.1088/1748-9326/accc24

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Other Link： https://iopscience.iop.org/article/10.1088/1748-9326/accc24/pdf

Repository Public URL： https://hdl.handle.net/2324/7234608

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

Research and social implementation related to carbon in marine and freshwater ecosystems are increasingly gaining emphasis in the global quest to achieve carbon neutrality. It is important not only to advance academic research, but also to solve practical problems for improved understanding, maintenance, and dissemination of information on carbon in marine or freshwater areas. In this study, we conducted a questionnaire survey of participants in activities related to carbon in marine or freshwater areas in Japan to clarify which issues were considered important and their understanding of the degree to which activities related to carbon in marine or freshwater areas had been achieved. Based on the responses to all questions, 77.9% of respondents, on average, among the practitioners in marine areas recognized the importance of the program strongly, while 46.5% recognized that the degree of achievement was insufficient. This tendency was more pronounced for carbon in freshwater than in marine areas(72.2% and 48.6%, respectively). The results, grouped by respondent attributes, revealed that the perception of importance and level of achievement varied depending on the organization of the activity, age, and years of knowledge of carbon in marine and/or freshwater areas. Practitioners with greater experience and those working on specific implementations perceived implementation-related aspects as more important and less accomplished than academic ones. This study provides valuable insights into the research aspects of carbon in marine and/or freshwater areas to achieve carbon neutrality.

DOI： 10.3389/fmars.2022.1036248

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：American Meteorological Society  

Abstract

Predicting the spatial distribution of maximum inundation depth (depth-MAP) is important for the mitigation of hydrological disasters induced by extreme precipitation. However, physics-based rainfall-runoff-inundation (RRI) models, which are used operationally to predict hydrological disasters in Japan, require massive computational resources for numerical simulations. Here, we aimed at developing a computationally inexpensive deep learning model (Rain2Depth) that emulates an RRI model. Our study focused on the Omono River (Akita Prefecture, Japan) and predicted the depth-MAP from spatial and temporal rainfall data for individual events.

Rain2Depth was developed based on a convolutional neural network (CNN), and predicts depth-MAP from 7-day successive hourly rainfall at 13 rain gauge stations in the basin. For training the Rain2Depth, we simulated the depth-MAP by the RRI model forced by 50-ensembles of 30-year data from large-ensemble weather/climate predictions. Instead of using the input and output data directly, we extracted important features from input and output data with two dimensionality reduction techniques (principal component analysis (PCA) and the CNN approach) prior to training the network. This dimensionality reduction aimed to avoid overfitting caused by insufficient training data. The nonlinear CNN approach was superior to the linear PCA for extracting features. Finally, Rain2Depth was architected by connecting the extracted features between input and output data through a neural network.

Rain2Depth-based predictions were more accurate than predictions from our previous model (K20), which used ensemble learning of multiple regularized regressions for a specific station. Whereas the K20 can predict maximum inundation depth only at stations, our study achieved depth-MAP prediction by training only the single model Rain2Depth.

DOI： 10.1175/aies-d-22-0036.1

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Other Link： https://journals.ametsoc.org/downloadpdf/journals/aies/aop/AIES-D-22-0036.1/AIES-D-22-0036.1.xml

Language：English   Publishing type：Research paper (scientific journal)  

DOI： doi:10.3389/fmars.2022.1036248

Repository Public URL： https://hdl.handle.net/2324/7234609

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>Wetlands, which are unique water environments, have various functions for water circulation and ecosystems, such as mitigating disasters such as floods and providing habitats for wetland creatures. On the other hand, there are many areas where part of the wetlands overlaps with the human residential area, and it has undergone various changes depending on the wetlands, such as being the target of development and disappearing, or being protected as a conservation area for rare creatures or a target area for tourism promotion. In this presentation, we will apply the interdisciplinary framework, which captures changes in the water environment from the perspective of fluctuations in the geosphere, the humanosphere, and the biosphere, to the discussion on solar power generation in the Kushiro Wetlands, and will demonstrate the effectiveness of the framework.</p>

DOI： 10.11520/jshwr.36.0_51

CiNii Research

Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>General Circulation Models (GCMs) used for climate change impact assessment have biases relative to observational data. These biases are corrected by applying long-term observational data (e.g. 20 years). However, there are many data scarce areas, such as developing countries. In these areas, reanalysis data is used instead of observational data. But reanalysis data also have biases since it targets global scale. This study aims to build statistical bias correction method for reanalysis data and verify the past river flow regime in the basin of Tateno dam. Tateno dam is under construction, so long-term pseudo-observational data is essential when we assess the river flow regime. As a result, it is revealed that the statistical correction method can reproduce the river flow regime comparison with observational data. Also, we found the reproducibility of discharge outflow from Tateno dam is almost same relative to observational data.</p>

DOI： 10.11520/jshwr.36.0_304

CiNii Research

Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>Recently, blue carbon, the amount of carbon captured by marine ecosystems, has been attracting attention since it is almost even equal to green carbon. In addition, it is said that ecosystems in freshwater areas such as aquatic macrophytes in agricultural ponds also have the possibility to capture and store carbon. However, the exuberance area and condition of macrophytes in freshwater areas has not been revealed in previous studies. Thus, this study aims to develop an estimation method for the exuberance area of macrophytes using satellite data (Sentinel-2). </p><p> We extracted water areas using near-infrared reflectance data, and ponds with NDVI values above a certain threshold were considered to have macrophytes. Then, the results were compared with field observations. </p><p> Of the 30 ponds extracted as water areas, 22 were correctly identified as having macrophytes, suggesting that satellite data can be used to estimate the presence of macrophytes in general.</p>

DOI： 10.11520/jshwr.36.0_300

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>We are engaged in transdisciplinary research on water. In this study, the water environment is considered as a "water cycle system" that always contains fluctuations caused by the interplay between the geosphere, the biosphere, and the humanosphere, and we are working to clarify the equilibrium under which the water cycle system has been evolving. The challenges and possibilities of transdisciplinary research are becoming clear from this effort so far. The challenge is how researchers from different fields can collaborate with each other. Because issues related to the hydrological cycle play an important role in the geosphere, biosphere, and humanosphere, there is potential for collaboration among the natural sciences, humanities, and social sciences, and biology, with specific goals.</p>

DOI： 10.11520/jshwr.36.0_47

CiNii Research

Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>Agricultural ponds, which have existed in a region since ancient times, are not only an important water resource for the region, but also play an important role in the water environment, biodiversity, and the history and culture of the region. Despite their diverse functions and challenges, agricultural ponds in Japan are undergoing a major transformation due to the declining birthrate and aging population, changes in the environment surrounding agriculture, and the increasing severity and frequency of heavy rainfall disasters. The changes are expected to be particularly significant for medium- and small-scale reservoirs, of which there are a vast number. Therefore, in this study, we conducted an analysis on agricultural ponds based on changes in the water environment, and conducted research on multifaceted evaluation of reservoirs that can be used for future maintenance and management.</p>

DOI： 10.11520/jshwr.36.0_49

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Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.78.2_I_925

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

EXPLORING APPROPRIATE INFLATION AND LOCALIZATION METHODSTO STABILIZE ENSEMBLE DATA ASSIMILATIONOF A RAINFALL-RUNOFF-INUNDATION MODEL
Data assimilation can improve forecast accuracy of dynamical models by combining model state variables and real-world observations. This study applied the ensemble Kalman filter (EnKF) for a rainfall-runoff-inundation (RRI) model to adjust model state variables with operational water-level observations. In contrast to atmospheric models, model state errors do not propagate in the non-chaotic RRI model. Therefore, it is important to explore error inflation methods for providing appropriate background error covariance for the EnKF. For that purpose, this study perturbed rainfall intensity for ensemble members as a way of the covariance inflation.

 A series of experiments with and without EnKF were employed in Omono River in Akita Prefecture. Our experiments showed that predicted water level was improved at both observed and unobserved stations compared to the RRI simulations without assimilation. This study also investigated effective localization methods for the RRI model. The application of localization along the river channel was found to perform as well as traditional localization based on Euclid distances commonly used in atmospheric data assimilation.

DOI： 10.2208/jscejhe.

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.envadv.2021.100153

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Hydrology and Water Resources  

DOI： 10.3178/jjshwr.35.122

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>Climate change and depopulation are expected to have a significant impact on various issues in the field of hydrology and water resources. Especially in Japan's mountainous regions, where the birthrate is declining and the population is aging, the problems associated with the aging of the people responsible for the maintenance and management of local water-related infrastructure are becoming more and more pronounced. One of the most notable examples is the maintenance and management of reservoirs. This study addresses the relationship between changes in land use, water use patterns, and rainfall patterns and sediment deposition in reservoirs and rivers. This study is significant in providing fundamental knowledge for considering the role of water infrastructure in agriculture under the circumstances of depopulation and climate change.</p>

DOI： 10.11520/jshwr.35.0_125

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> Reanalysis data has been used instead of observational data in the case of bias correction method is applied for outputs from GCM in an observational data scarce area, in which observational period is less than 20 years. However, reanalysis data does not match the real weather characteristics in a local scale since it is targeted at a global scale. In previous study, a statistical correction method for precipitation of reanalysis data has been developed. However, the method has not been applied for hydrometeorological data except for precipitation. Therefore, this study also developed and applied the method for the hydrometeorological data (temperature, humidity, pressure, shortwave radiation and wind speed). As a result, it is revealed that the distribution of corrected data by the statistical correction method is almost same relative to observational data. Furthermore, in order to increase the correction accuracy, it was found that we should apply probability distribution function (PDF) which is fitted the distribution of observational data according to the situation, since optimal PDF in the statistical correction method is different by the target station/area and/or hydrometeorological data.</p>

DOI： 10.2208/jscejhe.78.2_i_115

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Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般財団法人 住総研  

DOI： 10.20803/jusokenronbunjisen.48.0_155

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> In previous studies, climate data is considered the uncertainies by multi-ensemble data in climate change impact assessment. On the other hand, impact assessment model such as runoff model has not been taken into account the uncertainties like the range of predicted results by the model using the range of parameters that change with the predicted floods. Therefore, this study aims to evaluate the importance of the uncertainties of the runoff model for the future predictions by using d4PDF as input data to the model which is used the range of parameters ("the possible runoff model"). As the result, it is suggested that the changing trend that there is possible of missing such as the frequency of flood and draught in the case of using only "the best parameters model" which is optimized in calibration period could be able to predict by using "the possible runoff model".</p>

DOI： 10.2208/jscejhe.78.2_i_121

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Cavitation in fluid machinery can cause several problems such as degradation of performance, erosion, and so on. Therefore, the development of prediction methods for cavitation flow is an important research topic, and several cavitation models have been proposed. Multi-Process (MP) model, which is a homogenous one composed of multiple equations, can take account of main elementary processes in cavitation using the moment method for a size distribution function of cavitation bubbles. It is necessary to formulate the transport equations for each state variable based on appropriate assumptions. In this study, unsteady RANS simulation of the final stage model of a three-stage centrifugal pump using MP model was carried out to investigate the influence of the formulation of two kinds (types) of transport equations, i.e., advection-type and conservation-type. As a result, both types showed agreement with experiments in terms of head degradation curves, although differences were observed for cavity growth. In the conservation-type, bubble number density decreases in contrast to the increase in void fraction. It was confirmed that this suppresses the growth of cavities.</p>

DOI： 10.1299/jsmefed.2022.os07-24

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In the present study, the gas-liquid two-phase flow performance of a turbopump equipped with an inducer was experimentally investigated. The almost homogeneous bubbly two-phase flow condition was successively set by the uniform aeration of gas dissolved in water upstream of the test pump, which was realized by a sudden pressure decrease with the valve closure. The gas-liquid volumetric flow rate ratio was estimated from the pump inlet pressure and the initial amount of dissolved oxygen under the assumption of mass equilibrium condition of the local dissolved oxygen. The effect of dissolved oxygen content on the gas-liquid two-phase flow performance of a turbopump was investigated. The results showed that low DO conditions are not suitable for evaluating gas-liquid two-phase flow performance because of in-negligible effect of vaporous cavitation. In addition, the effects of a reduced-diameter suction pipe and a swirl brake on the gas-liquid two-phase flow performance of a turbopump were investigated. The results showed that the effect on the gas-liquid two-phase flow performance was small under high DO condition, but the performance deteriorated under low DO condition.</p>

DOI： 10.1299/jsmefed.2022.os07-20

CiNii Research

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_175

Authorship：Last author   Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_151

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_1153

Language：Japanese  

DOI： 10.2208/jscejhe.77.2_I_109

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_169

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_1279

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_1393

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_181

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_37

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.77.2_i_1219

Language：Others   Publishing type：Research paper (scientific journal)  

Abstract

Modern dietary habits in communities are linked and are part of the global food supply chain. To achieve sustainable food production and consumption, communicating the impact associated with food production and dietary choices at community level to consumers is important. However, previous footprint studies have primarily focussed on food consumption at the national level and neglected community–level consumption activities. This study surveyed the diets of a small island community and linked the results with multi-region land footprint analysis in Ollei Village, Republic of Palau. The analysis was used to determine the extent to which the dietary lifestyles of communities depend on external land use through the global supply chain. We showed that the global food supply chain has reached this corner of the world, and the dietary habits of the community are already heavily dependent on processed and imported foods. The community and country are highly dependent on large land use in some major producer/exporting countries through the global food supply chain. In addition, the amount of external land used for food production exceeds the biocapacity of the agricultural land in the community and country. This study bridges the gap between community–level consumption activities and national-scale footprint analysis, and quantitatively assesses the impact of consumption activities at the community level on the global environment. The results and approach of this study could contribute to the development and implementation of vertically integrated food policies between the national and community level in Palau.

DOI： 10.1088/1748-9326/ac0212

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/river.27.0_45

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/river.27.0_505

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/river.27.0_603

Language：English   Publishing type：Research paper (scientific journal)  

The increasing risk of coastal flooding and water shortage in Pacific Island Countries is usually attributed to climate change hazards. This ignores other risk components, exposure and vulnerability, of which a major contributor is urbanization.We develop simplified analyses that can be applied to other PICs. By dividing climate risks into hazard and exposure components we determine how urbanization contributed to present-day risks and then predict how growing climate change hazards may increase future risk, using the Republic of Palau as a case study.Results show that urbanization was responsible for 94% of the buildings exposed to coastal flooding today. Projected sea level rise, 30.2 cm by 2050, only increased exposure of today's buildings by 0.5%. In both present and future scenarios exposure resultant from urbanization was more significant than sea level rise.Our water scarcity index showed urbanization caused 3 of the 7 recorded water shortages from 1980-2018. From 2041-2079, analysis of projected rainfall showed mean reductions between 1.6-16.6% and increased variance between 0.3-3.4%. This led to three times as many water shortages under present population levels. In historical and future scenarios exposure from increased population was just as significant in causing water shortages as rainfall variation.These findings suggest that urban management is an important tool to lower exposure to coastal flooding and water shortage and we recommend that decision makers prioritize urbanization within climate risk policy in Pacific Island Countries.

DOI： 10.1088/1748-9326/abb9dc

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

This study highlights the severity of the low snow water equivalent (SWE) and remarkably high temperatures in 2020 in Japan, where reductions in SWE have significant impacts on society due to its importance for water resources. A continuous 60-year land surface simulation forced by reanalysis data revealed that the low SWE in many river basins in the southern snowy region of mainland Japan are the most severe on record. The impact of the remarkably high temperatures in 2020 on the low SWE was investigated by considering the relationships among SWE, temperature, and precipitation. The main difference between the 2020 case and prior periods of low SWE is the record-breaking high temperatures. Despite the fact that SWE was the lowest in 2020, precipitation was much higher than that in 2019, which was one of the lowest SWE on record pre-2020. The results indicate the possibility that even more serious low-SWE periods will be caused if lower precipitation and higher temperatures occur simultaneously.

DOI： 10.1038/s41598-020-75440-8

Language：Others  

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.3178/jjshwr.33.203

Authorship：Lead author,　Corresponding author   Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.3178/hrl.14.117

Language：Others  

Language：Others  

Language：Others   Publishing type：Research paper (scientific journal)  

Characteristics of the snow depth in 2020 and estimation of future changes based on the relationship between temperature and precipitation.

DOI： 10.2208/jscejer.76.5_i_261

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11408/jsidre.88.iv_17

Authorship：Lead author,　Corresponding author   Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.3178/jjshwr.33.111

Language：English   Publishing type：Research paper (scientific journal)  

Estimation of direct and indirect economic losses caused by a flood with long-lasting inundation: Application to the 2011 Thailand flood

Language：Japanese   Publishing type：Research paper (scientific journal)  

COMPARISON BETWEEN STATISTICAL CORRECTION METHOD AND DYNAMICAL DOWNSCALING FOR JRA-55 IN RIVER BASIN SCALE TOWARD CLIMATE CHANGE IMPACT ASSESSMENT

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.75.1_299

Language：English   Publishing type：Research paper (scientific journal)  

Observed past climate data used as input in glacier models are expected to differ among datasets, particularly those for precipitation at high elevations. Differences among observed past climate datasets have not yet been described as a cause of uncertainty in projections of future changes in glacier mass, although uncertainty caused by varying future climate projections among general circulation models (GCMs) has often been discussed. Differences among observed past climate datasets are expected to propagate as uncertainty in future changes in glacier mass due to bias correction of GCMs and calibration of glacier models. We project ensemble future changes in the mass of glaciers in Asia through the year 2100 using a glacier model. A set of 18 combinations of inputs, including two observed past air temperature datasets, three observed past precipitation datasets, and future air temperature and precipitation projections from three GCMs were used. The uncertainty in projected changes in glacier mass was partitioned into three distinct sources: GCM uncertainty, observed past air temperature uncertainty, and observed past-precipitation uncertainty. Our findings indicate that, in addition to the differences in climate projections among GCMs, differences among observed past climate datasets propagate fractional uncertainties of about 15% into projected changes in glacier mass. The fractional uncertainty associated with observed past precipitation was 33-50% that of the observed air temperature. Differences in observed past air temperatures and precipitation did not propagate equally into the ultimate uncertainty of glacier mass projection when ablation was dominant.

DOI： 10.1007/s00382-019-04868-0

Language：Others  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.75.2_i_1081

Language：Others  

Language：Others  

Language：Others  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.24709/jasdis.17.1_9

Language：Others  

Language：Others  

Efficiency and sustainability of land-resource use on a small island

DOI： 10.1088/1748-9326/ab1455

Language：Others  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

ESTIMATION OF FLOOD DAMAGE UNDER CLIMATE CHANGE WITH CONSIDERING DEPOPULATION AND ASSET DISTRIBUTION CHANGE

Language：Others  

Language：Japanese  

Classifying large ensemble database of future climate projection : A case of precipitation in Japan

Language：Japanese  

The development of bias corrected hourly precipitation dataset for AMeDAS stations based on the projections from d4PDF

Language：Japanese   Publishing type：Research paper (scientific journal)  

UNCERTAINTY FROM CLIMATE FORCING OF PROJECTIONS IN GLACIER MELT FOR HIGH MOUNTAIN ASIA

DOI： 10.2208/jscejhe.74.i_211

Language：Others  

Language：Others  

Language：Others  

Projection of the changes in weather Potentially affecting tourism in the Yaeyama islands under global warming

Language：Others  

Language：English   Publishing type：Research paper (scientific journal)  

This study represents the first attempt to quantify the effects of autonomous adaptation on the projection of global flood hazards and to assess future flood risk by including this effect. A vulnerability scenario, which varies according to the autonomous adaptation effect for conventional disaster mitigation efforts, was developed based on historical vulnerability values derived from flood damage records and a river inundation simulation. Coupled with general circulation model outputs and future socioeconomic scenarios, potential future flood fatalities and economic loss were estimated. By including the effect of autonomous adaptation, our multimodel ensemble estimates projected a 2.0% decrease in potential flood fatalities and an 821% increase in potential economic losses by 2100 under the highest emission scenario together with a large population increase. Vulnerability changes reduced potential flood consequences by 64%-72% in terms of potential fatalities and 28%-42% in terms of potential economic losses by 2100. Although socioeconomic changes made the greatest contribution to the potential increased consequences of future floods, about a half of the increase of potential economic losses was mitigated by autonomous adaptation. There is a clear and positive relationship between the global temperature increase from the pre-industrial level and the estimated mean potential flood economic loss, while there is a negative relationship with potential fatalities due to the autonomous adaptation effect. A bootstrapping analysis suggests a significant increase in potential flood fatalities (+5.7%) without any adaptation if the temperature increases by 1.5°C-2.0°C, whereas the increase in potential economic loss (+0.9%) was not significant. Our method enables the effects of autonomous adaptation and additional adaptation efforts on climate-induced hazards to be distinguished, which would be essential for the accurate estimation of the cost of adaptation to climate change.

DOI： 10.1088/1748-9326/aa9401

Language：English   Publishing type：Research paper (scientific journal)  

Landslides are more widespread compared to any other geological hazards in Thailand. The steep slope and high elevation areas have more potential for landslide hazards. However, weather extremes, particularly extreme rainfall, play a major role in the occurrence of landslides in Thailand. The objective of the present study is to analyze the changes in the probability of landslide occurrences in Thailand due to climate change. For this purpose, probabilistic landslide hazard maps for extreme rainfall values for 5-, 10-, 50-, and 100-year return periods are developed for historical and future climatic conditions, derived from 10 global climate models (GCMs) under two representative concentration pathway (RCP) scenarios, namely, RCP 4.5 and RCP 8.5. The results reveal that the 5-year return period extreme rainfall amount will reach 200 mm/month in the eastern and southern provinces for RCP 4.5 and the northwestern, eastern, and southern provinces for RCP 8.5. The increase in extreme rainfall will cause a sharp increase in the landslide probability in Thailand, except in low altitude regions. The probability of 100-year return period landslide will increase by 90% in 40% and 80% of the areas in Thailand under RCP 4.5 and RCP 8.5, respectively. It is expected that the landslide hazard maps developed in this study will help policy makers take necessary measures to mitigate increasing landslide events due to climate change.

DOI： 10.1016/j.crm.2018.03.002

Language：Japanese  

STATISTICAL CORRECTION METHOD FOR PRECIPITATION OF JRA-55 IN LOCAL SCALE TOWARD CLIMATE CHANGE IMPACT ASSESSMENT

DOI： 10.2208/jscejhe.73.I_115

Language：Japanese  

CONSIDERATIONS ON THE USE OF QUANTILE MAPPING BIAS CORRECTION FOR THE IMPACT ASSESSMENT OF CLIMATE CHANGE

DOI： 10.2208/jscejhe.73.I_121

Language：English   Publishing type：Research paper (scientific journal)  

Observational evidence indicates that a number of glaciers have lost mass in the past. Given that glaciers are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past glacier mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain glacier mass to detect and attribute past glacier mass changes. An 8,800-year control simulation of glaciers enabled us to evaluate detectability. The results indicate that human-induced increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed glaciers. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.

DOI： 10.1038/srep29723

Language：Japanese  

パラオ共和国バベルダオブ島における土地資源利用効率の検討

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejhe.72.i_37

Language：English   Publishing type：Research paper (scientific journal)  

Fine particulate matter (aerodynamic diameter <2.5 mu m; PM2.5) poses risks to human health. While precipitation is the main process for decreasing ambient pollutant concentrations, scavenging of PM2.5 by precipitation remains to be investigated. Here we formulated the processes of PM2.5 scavenging by precipitation from observed PM2.5 concentrations ([PM2.5]) and precipitation intensities. Then we analyzed how changes in precipitation patterns would affect health risks related to PM2.5 on the basis of a Monte Carlo simulation. Tokyo, the capital of Japan, was selected as the target for this study because of its social significance. We found that [PM2.5] decreased significantly through scavenging of PM2.5 from the atmosphere by precipitation. In contrast, we found no significant correlation between reduction of [PM2.5] and precipitation intensity. Our model for estimating the reduction of PM2.5 and the Monte Carlo simulation showed good agreement with observations. Among various changes in potential precipitation patterns, changes in the arithmetic mean of the number of events and/or in precipitation duration were more influential on reduction of [PM2.5] than changes in their standard deviations. Health risks due to PM2.5 will increase with decreases in precipitation duration and occurrence.

DOI： 10.2166/wst.2015.346

Language：Japanese   Publishing type：Research paper (scientific journal)  

GLOBAL WATER RESOURCE ASSESSMENT INCLUDING GLACIER MELTWATER FROM MOUNTAINOUS REGIONS

DOI： 10.2208/jscejhe.71.I_451

Language：English   Publishing type：Research paper (scientific journal)  

Application of performance metrics to climate models for projecting future river discharge in the Chao Phraya River basin

DOI： 10.3178/hrl.8.33

Language：English   Publishing type：Research paper (scientific journal)  

Projected hydrological changes and their consistency under future climate in the Chao Phraya River Basin using multi-model and multi-scenario of CMIP5 dataset
It is important to examine what future hydrological changes could occur as a result of climate change. In this study, we projected hydrological changes and their consistency under near-future and end-of-21st-century climate in the Chao Phraya River Basin. Through hydrological simulations using output from six AOGCMs under the RCP 4.5 and 8.5 scenarios, we have reached the following conclusions. Our results demonstrate a projected increase in mid-rainy season precipitation under future climate, which is a necessary condition for a large volume of runoff to occur in the late rainy season. Under end-of-21st-century climate, all simulations using six AOGCMs showed a large increase (> 20%) in runoff in Nakhon Sawan catchment under both RCP scenarios. Compared to the capacities of the Bhumibol and Sirikit dams, projected increases in runoff at the end of the 21st century are high. New flood management and mitigation plans will likely be necessary. Ensemble mean increases in precipitation and runoff were higher under RCP 8.5 than under the RCP 4.5 scenario in both projected periods. Thus, higher global mean temperature would cause higher precipitation and runoff in the basin. This inference is also supported by the higher precipitation and runoff projected under the late future compared with under the near-future climate.

DOI： 10.3178/hrl.8.27

Language：English   Publishing type：Research paper (scientific journal)  

A warmer climate would increase the risk of floods(1). So far, only a few studies(2,3) have projected changes in floods on a global scale. None of these studies relied on multiple climate models. A few global studies(4,5) have started to estimate the exposure to flooding (population in potential inundation areas) as a proxy of risk, but none of them has estimated it in a warmer future climate. Here we present global flood risk for the end of this century based on the outputs of 11 climate models. A state-of-the-art global river routing model with an inundation scheme(6) was employed to compute river discharge and inundation area. An ensemble of projections under a new high-concentration scenario(7) demonstrates a large increase in flood frequency in Southeast Asia, Peninsular India, eastern Africa and the northern half of the Andes, with small uncertainty in the direction of change. In certain areas of the world, however, flood frequency is projected to decrease. Another larger ensemble of projections under four new concentration scenarios(7) reveals that the global exposure to floods would increase depending on the degree of warming, but interannual variability of the exposure may imply the necessity of adaptation before significant warming.

DOI： 10.1038/NCLIMATE1911

Language：Japanese  

A STUDY ON THE DIFFERENCE OF THE FUTURE ESTIMATES FOR DAILY EXTREME PRECIPITATION CAUSED BY THE SELECTION OF GCM, RCP EMISSION SCENARIO AND BIAS CORRECTION METHOD

DOI： 10.2208/jscejhe.69.I_385

Language：Japanese  

Caucasus地域におけるASTER衛星画像を用いたデブリ広域被覆分布の推定

DOI： 10.2208/jscejer.69.I_45

Language：English  

Projection of glacier mass changes under a high-emission climate scenario using the global glacier model HYOGA2
We report a time series (1948&ndash;2100) of global-scale meltwater from mountain glaciers and ice caps (MGI) estimated by the global glacier model HYOGA2. HYOGA2 calculates the temporal fluctuation of the mass balance for 24,234 individual glaciers worldwide. It covers 90% of the total glacier area, except for glaciers in Greenland and Antarctica. HYOGA2 also accounts for regionally distributed changes in glacier area and altitude associated with glacier retreat and advance. By computation of individual glacier changes, future dissipation and glacier mass and area changes can be simulated in the model. The cumulative volume loss of water between 1948 and 2005 was estimated to be 25.9 &plusmn; 1.4 mm sea level equivalent (SLE). A future projection under a high-emission scenario demonstrated significant losses of water from MGI equivalent to 60.3 &plusmn; 7.9 mm SLE between 1948 and 2060 and 99.0 &plusmn; 14.9 mm SLE between 1948 and 2099.

DOI： 10.3178/hrl.7.6

Language：English   Publishing type：Research paper (scientific journal)  

Bias-correction methods applied to monthly temperature and precipitation data simulated by multiple General Circulation Models (GCMs) are evaluated in this study. Although various methods have been proposed recently, an intercomparison among them using multiple GCM simulations has seldom been reported. Moreover, no previous methods have addressed the issue how to adequately deal with the changes of the statistics of bias-corrected variables from the historical to future simulations. In this study, a new method which conserves the changes of mean and standard deviation of the uncorrected model simulation data is proposed, and then five previous bias-correction methods as well as the proposed new method are intercompared by applying them to monthly temperature and precipitation data simulated from 12 GCMs in the Coupled Model Intercomparison Project (CMIP3) archives. Parameters of each method are calibrated by using 1948-1972 observed data and validated in the 1974-1998 period. These methods are then applied to the GCM future simulations (2073-2097) and the bias-corrected data are intercompared. For the historical simulations, negligible difference can be found between observed and bias-corrected data. However, the differences in future simulations are large dependent on the characteristics of each method. The new method successfully conserves the changes in the mean, standard deviation and the coefficient of variation before and after bias-correction. The differences of bias-corrected data among methods are discussed according to their respective characteristics. Importantly, this study classifies available correction methods into two distinct categories, and articulates important features for each of them. Citation: Watanabe, S., S. Kanae, S. Seto, P. J.-F. Yeh, Y. Hirabayashi, and T. Oki (2012), Intercomparison of bias-correction methods for monthly temperature and precipitation simulated by multiple climate models, J. Geophys. Res., 117, D23114, doi:10.1029/2012JD018192.

DOI： 10.1029/2012JD018192

Language：Japanese  

平成23年7月新潟・福島豪雨による信濃川下流域での出水と被害の特徴―平成16年7月新潟・福島豪雨との比較を中心として―

Language：Japanese  

GCM出力値補正手法により生じる月平均気温および月降水量の予測差

Language：English   Publishing type：Research paper (scientific journal)  

The empirical relationship between solar radiation and sunshine duration in Thailand is studied in this paper. Although regional long-term regional solar radiation has not yet been measured in Thailand, the data of sunshine duration measurements are available. Hence, measurement of global solar radiation is conducted to find the relationship between daily solar radiation and sunshine duration, which is mostly linear. The distribution of regression coefficients is examined and the formula that can be applied in Thailand is estimated. The efficiency of the proposed formula is validated through its prediction. The result shows that the accuracy of the country-wide regression equations can be comparable to that constructed at each station. Moreover, it is found that the proposed equations are more effective from May to November than from December to April. The proposed equations are applied to estimate solar radiation in Thailand and the differences in their prediction are found in the characteristics of statistical distributions between May November and December April.

DOI： 10.2151/jmsj.2011-A25

Language：Japanese  

GCM月降水量補正手法およびMIROC5出力補正値の考察

Language：Japanese  

平成21年8月台風9号に伴う豪雨による水害の特徴

Language：Japanese  

気候変動下での全球水資源量評価に向けた気候モデル出力値補正手法の開発と検証

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researchmap

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<p>This study examined the validity of the widely discussed hypothesis that "flood disasters lead to population decline" in the Japanese context. Focusing on 2010 to 2020, we analyzed demographic changes at the district level in municipalities affected by major river floods and the 2011 tsunami. Using cohort-component methods, projected 2020 populations were compared to actual census data, and the difference was defined as "population decline acceleration.” Results showed slightly higher acceleration in tsunami-affected areas, but no clear trend in flood-affected areas. However, in flood-prone lowland regions, a significant decline among people in their 20s and 30s was observed, suggesting generational differences potentially linked to housing conditions or relocation decisions.</p>

DOI： 10.11520/jshwr.38.0_111

CiNii Research

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<p>The irrigation pond database published by Japan’s Ministry of Agriculture, Forestry and Fisheries is largely based on past surveys, and significant discrepancies between the database and actual conditions have been identified. In this study, we developed a method to improve the reliability of the database by detecting pond surface water using optical satellite imagery and incorporating multi-year water presence data. We found that the most accurate water detection was achieved using the near-infrared band of Sentinel-2 imagery. Applying this method to other regions revealed that the number of ponds with actual water differs significantly from the number recorded in the database.</p>

DOI： 10.11520/jshwr.38.0_399

CiNii Research

During the heavy rainfall in July 2020, 15,883 m³ of floating debris was collected in the Ariake Sea and Yatsushiro Sea, Kyushu, Japan from July 4th to 31st. This fact means that approximately 12 times of floating debris which is normally collected in just one month. If driftwoods are discharged into a coastal area, they will have serious effects on fisheries and marine ecosystem. Also, driftwoods accumulated under the bridge will make rivers overflowed. In this way, driftwoods affect various fields and regions, so it is necessary to evaluate the risk of driftwoods generation. The Japan Meteorological Agency uses the snake lines as a criterion for determining landslide warning information. The snake line is depicted by plotting the relation between the 60- minute cumulative rainfall and the soil rainfall index at regular intervals. If the snake line exceeds the landslide occurrence reference line (Critical Line: CL), it is judged that the risk of landslides become to be high. In the present research, we attempt to conduct the followings: i) to confirm whether the snake line in a geographical mesh with the slope collapse exceeds CL in the heavy rainfall in July 2020; ii) to develop the logistic model for predicting the amount of driftwood generation adding the information of CL; and iii) to assess the effect of the climate change by applying d4PDF to the model. As a result, we can see the followings: 1) the snake line can show the slope collapse by correcting the present CL; 2) in the case of a future climate with increase of 40C mean air temperature, compared to the present climate, amount of driftwood generation will increase by approximately 1.2 times. It is necessary to improve estimation of possibility using CL for precise real time prediction of driftwoods generation.

Scopus

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Climate change is profoundly altering precipitation patterns, leading to more frequent and severe flooding events that significantly impact riverine and marine ecosystems. The Ariake Sea, a vital estuarine ecosystem on Kyushu Island, Japan, is particularly susceptible to these impacts. Distinguished for its thriving fisheries and seaweed cultivation, the region experiences severe hypoxia during the rainy season, jeopardizing its ecological integrity and economic sustainability. This study used the d4PDF climate simulation database, which provides high-resolution regional climate simulations for Japan, to examine hypoxia dynamics in the Ariake Sea. By integrating current climate data with the Delft3D-FLOW hydrodynamic model and the Delft3D-WAQ ecosystem model, we analyzed dissolved oxygen (DO) dynamics under various flood scenarios. The findings revealed a strong correlation between flood exceedance probabilities and hypoxia severity, with hypoxic conditions reaching their peak during July and August. These results underscore the urgent necessity for implementing adaptive strategies to mitigate climate change impacts, preserve marine ecosystems, and protect the communities that depend on them.

Scopus

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<p>To evaluate impacts of climate change on water environment and ecosystem services, Global Climate Models (GCMs) are used in the previous studies. However, it is necessary to apply bias correction to GCM with long-term observation data (e.g. over 20 years) to evaluate impacts of climate change since GCMs has biases between the observation data. In generally, reanalysis data has been used in a data scarce area. However, despite reanalysis data has been applied data assimilation method based on observation data, reanalysis data does not match the real weather characteristics (e.g. precipitation) in a local scale since it is targeted at a global scale. In previous studies, statistical correction method for precipitation of reanalysis data has been developed. However, the method has not been developed for hydro-meteorological data except for precipitation (e.g. temperature, air-pressure, windspeed). Therefore, this study aims to develop and apply the statistical correction method for hydro-meteorological data of re-analysis data.</p>

DOI： 10.11520/jshwr.35.0_235

CiNii Research

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<p>We analyzed agricultural reservoir characteristics using multi-scale approaches and diverse data sources, ranging from nationwide open data analyses to participatory surveys in specific areas. Water areas were detected via satellite observation, and basin-specific reservoir characteristics were compared using open data. We analyzed newspaper articles related to reservoirs, examined reservoir name characteristics, and conducted participatory surveys to understand local perceptions. A workshop using aerial photographs and three-dimensional models from past to present was conducted to capture residents' perceptions. An automated reservoir extraction method, validated in Saijo City, Ehime, and Itoshima City, Fukuoka, showed higher accuracy than existing databases. Open data comparisons revealed areas critical for water resources and areas with maintenance challenges. Trend analysis of newspaper articles indicated differences in administrative responses between disaster prevention and environmental issues. Reservoir name analysis highlighted that size perceptions are regionally relative. Participatory surveys revealed generational differences in risk perception, with a shift from water resources to fire protection and environmental value.</p>

DOI： 10.11520/jshwr.38.0_79

CiNii Research

Language：Japanese  

<p>This study aims to elucidate the multifaceted roles and associated challenges of agricultural reservoirs within the Kuroo district of Takeo City, Saga Prefecture. In this region, three primary water sources are utilized: groundwater, irrigation channels sourced from the Hanjo Dam, and agricultural reservoirs. Among these, agricultural reservoirs are particularly valued for their function as a water source for fire prevention. The research employed participatory methods, including workshops that incorporated visual aids such as satellite imagery and three-dimensional models. These tools facilitated the elicitation of community memories and highlighted intergenerational differences in risk perception and awareness. The findings underscore the complexity of local perceptions regarding the functions and management of agricultural reservoirs. Moving forward, ensuring the sustainability of these reservoirs as regional resources will require ongoing intergenerational dialogue and integrative, cross-disciplinary approaches.</p>

DOI： 10.11520/jshwr.38.0_377

CiNii Research

Language：Japanese  

<p>This study analyzes the characteristics of agricultural reservoirs across Japan using open data, aiming to support the future development of broad-scale evaluation indicators. Agricultural reservoirs have multiple functions, including water resource storage, flood control, ecosystem conservation, and freshwater carbon management. However, disaster risks and maintenance challenges are growing concerns. Previous studies allowed municipal-level assessments, but regional comparisons were limited. Using data from the Ministry of Agriculture, Forestry and Fisheries and other sources, this study examined reservoir distribution, embankment shapes, water resource importance, and management difficulty by watershed. Results showed substantial regional variation in reservoir roles and risks. In the Seto Inland Sea region and the Kitakami River watershed, reservoirs are especially critical. In western Japan, elongated embankments suggest higher failure risks. Some areas also face heavy management burdens despite having fewer reservoirs.</p>

DOI： 10.11520/jshwr.38.0_379

CiNii Research

Language：Japanese  

<p>Flood-protection forests, woodlands planted and managed along riverbanks and levees, constitute a traditional flood-control practice in Japan. Although declines in riparian forests functioning as flood-protection forests have been reported in association with land-use changes along rivers, previous works have been limited to case studies of well-known demonstration sites. No study to date has examined the long-term dynamics of flood-protection forests across a broad study area without a priori selection of target stands.</p><p>In this study, we conducted a regional-scale analysis of temporal changes in riparian forests serving as flood-protection forests in western Japan, focusing on first-class river systems in the Chugoku, Shikoku, and Kyushu regions. By integrating river network, land-use, and terrain classification data in a GIS framework, we calculated both the absolute area and percentage cover of forest vegetation within a 100 m buffer zone along each river corridor for each region and river system. We then characterized the temporal trajectories and tested for trends.</p><p>Our results demonstrate that (1) flood-protection forests have exhibited a declining trend in all three regions; (2) this decline has persisted from 1976 through 2021 in Chugoku and Shikoku, whereas in Kyushu the downward trend was interrupted around 2009; and (3) in Kyushu, the pattern of change in forest cover ratios varies markedly among individual river systems. These findings provide the first broad-scale evidence of both regional and river-system differences in the long-term dynamics of flood-protection forests in western Japan.</p>

DOI： 10.11520/jshwr.38.0_415

CiNii Research

Language：Japanese  

<p>Aging infrastructure and climate change pressures on flood hazards highlight the importance of up-to-date flood risk management. Critical infrastructures, such as large dams, have been designed to withstand Probable Maximum Precipitation (PMP) in many regions. However, the PMP estimates in operation largely neglect climate change impacts due to limited understanding of how climate change affects such rare events. Although the Clausius-Clapeyron (C-C) rate (~7%/K) is often used to quantify precipitation changes with temperature, extreme events may exhibit stronger increases due to dynamic atmospheric effects. To address this, Hiraga et al. (2025) proposed a physically based method to estimate PMP under climate change. Applied to the Akagawa and Arakawa Basins, the results showed rainfall increases up to 21%/K for 1-hour duration—significantly exceeding the C-C scaling rate. We also evaluated the occurrence probability of the estimated PMP scenarios using large-ensemble data, proposed as a new framework for modernizing PMP concept.</p>

DOI： 10.11520/jshwr.38.0_25

CiNii Research

Language：Japanese  

<p>This study investigates the geographical and environmental characteristics of agricultural reservoirs in Japan by analyzing their names. Using national data from the Ministry of Agriculture, Forestry and Fisheries, we extracted reservoir names then analyzed the frequency of the remaining name components. The top 100 names were classified into six categories: "morphology", "topography", "location", "history", "faith", and "ecology"—excluding names derived from personal or place names. Regional patterns were examined in major river basins with over 200 reservoirs. The Seto Inland Sea region showed high proportions in “morphology,” “topography,” and “history.” The Kanto region had relatively higher rates in “faith” and “morphology.” We also explored the relationship between reservoir names and storage capacity, finding general correlations, though inconsistencies suggest local, relative naming practices.</p>

DOI： 10.11520/jshwr.38.0_383

CiNii Research

Language：Japanese  

<p>日本の古日記の多くには、日ごとの天気の種類（晴れ、曇り、雨など）が記録されている。これまでの研究は、このような記録を用いて、月〜季節平均気候が復元されてきた。しかし、日単位の気候を復元した研究はごくわずかであった。本研究では、データ同化を用いて、20km解像度で日毎の気象場を復元すること目指す。データ同化は、力学系理論と統計学に基づいて、モデルシミュレーションと観測を融合する。本研究では、d4PDF (database for Policy Decision making for Future Climate Change)として知られる大規模アンサンブル気候シミュレーションのデータセットをモデルシミュレーションとして用いる。d4PDFは3000年以上にわたるデータが入手可能であり、DAにおいては良質な事前情報として用いることができる。</p><p>本発表では、現在気候に提案手法を適用し、実現可能性を探る。観測にはAMeDASを用い、特に降水量に注目した評価結果について示す。</p>

DOI： 10.11520/jshwr.38.0_1

CiNii Research

Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>WACCA is a community of young to mid-career researchers and engineers in the field of hydrology and water resources. It serves as a platform for practical activities collaboration between industry, government, and academia. Before COVID-19(2019), WACCA had convened several meetings, including the 9th and 10th meetings. Post-2020, WACCA continued using online tools. In recent times, while the convenience of online communication has been widely acknowledged, there have been some who have expressed the view that it is difficult to engage in in-depth online discussions. Consequently, this year's activities were concentrated on offline activities, resulting in the convening of an offline meeting. This paper presents a report on the activities and an overview of the field survey planned for the meeting.Furthermore, the Next WACCA Project was initiated this year to study the next generation of WACCA. The activities and future plans of the organization will be presented.</p>

DOI： 10.11520/jshwr.37.0_3

CiNii Research

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Language：Japanese  

Report of the Series of Online Lectures and Workshop on Inter-sectoral Collaboration Among Early-career Researchers and Managers

DOI： 10.3178/jjshwr.34.386

Language：Japanese  

Report of the WACCA virtual laboratory

DOI： 10.3178/jjshwr.34.390

Language：Others  

Current Status and Issues Related to Agricultural Pond Management – A Case Report of Tanbara, Saijo, Ehime

DOI： 10.3178/jjshwr.34.127

Language：Japanese  

WACCA virtual laboratory, a research society of hydrology and water resources towards post covid-19

DOI： 10.3178/jjshwr.33.274

Language：Japanese  

Online Networking Activities Among the Early-Career Researchers and Managers in the Water Sector

DOI： 10.3178/jjshwr.33.271, 10.3178/jjshwr.34.386_references_DOI_8718O68P4LOCcmMYGhQ8mEmSs3w, 10.3178/jjshwr.34.390_references_DOI_8718O68P4LOCcmMYGhQ8mEmSs3w

Language：Japanese  

ラジコンボートと小型ソナーを活用した簡易ため池測深装置の試行

Language：Japanese  

WACCA meeting 10 「水文・水資源学Beyond2030ワークショップ」会議報告

DOI： 10.3178/jjshwr.33.17

Language：Japanese  

Language：Japanese  

Language：Others  

Climate change impact assessment on suspeded sediment loading using large ensemble of climate experiments -a case study in mountainous small basin, Hokkaido-

Language：English  

Prediction of river flow regime under climate change in a acold region using large ensemble of climate experiment

Language：Japanese  

Frontiers in Hydrology and Water Resources Research

DOI： 10.3178/jjshwr.31.509

Language：Japanese  

Interdisciplinary Research Approaches toward Sustainable Strategy for Flood Control and Water Use in Mountainous Rural Region

Language：Japanese  

Interdisciplinary Research Approaches toward Sustainable Strategy for Flood Control and Water Use in Mountainous Rural Region

Language：Japanese  

将来洪水リスク評価において人口減少を考慮する重要性

Language：Japanese  

Report of the 7th WACCA meeting "Discussion on future water-related research from the viewpoint of research methods"

DOI： 10.3178/jjshwr.31.33

Language：Japanese  

WACCA meeting 06会議報告「水関連研究の現状と課題」
&amp;emsp;The discussion in the WACCA meeting 06 is reported. The topics in the meeting was issues and breakthroughs in the field of water related researches. Based on the presentations about issues and breakthroughs in each research target, our next challenges to work on were discussed.

DOI： 10.3178/jjshwr.30.260

Language：Japanese  

気候変動によるタイ国の斜面崩壊影響評価

Language：Japanese  

Language：Japanese  

Language：Japanese  

Activity report of the Young Researchers Group 2011 : Our view to the current situations of disaster-prevention and suggestions for future activities