The effectiveness of Carbon Dioxide Removal (CDR) as a climate change mitigation measure has been acknowledged. However, there are few comprehensive studies evaluating CDR, and they often overlook the social constraints that act as barriers to its implementation. This study focuses on CDR directly related to the energy system and aims to elucidate the impact of social constraints on the quantity of CDR introduced and energy supply and demand. The results suggest that the effects on the energy system vary depending on the constraints. For instance, if Carbon Capture and Storage are restricted, a significant transition to low-carbon energy sources will be necessary. Conversely, if energy crops are restricted, there is an increase in the introduction of CDR, and a tendency to continue using fossil fuels in the transportation sector is observed. Therefore, the importance of considering the impact of social constraints on the energy system when deliberating decarbonization policies is highlighted.

 The implementation of Climate Change mitigation measures in Japan leads to a heavy burden on low-income groups. Therefore, there are concerns that mitigation measures have a regressive impact on household consumption. Although there are a variety of energy scenarios to achieve long-term decarbonization goals, previous studies targeting Japan have not analyzed the impact on household consumption considering the uncertainty of energy scenarios across models. Therefore, in this study, we focused on Japan and evaluated the impact on household consumption by income group under the 2050 decarbonization scenario, considering the uncertainty by using multiple models. The results showed that climate change mitigation measures have a regressive impact on household consumption until 2050. Furthermore, it was found that the impact will continue to increase until 2040. However, after 2040, there was a wide range of results among the models. It was suggested that economic and technological policies are necessary to suppress its regressive impact.

 In 2019, Agriculture, forestry and other land-use sectors account for 22% of global anthropogenic green-house gases emission, and its proportion in developing countries is high. Agriculture sector is expected to play an important role to reduce greenhouse gases emissions. In this study, we aim to reveal potential reduction amounts of methane and nitrous oxide emissions in agriculture sector in Africa region at country level using the AFOLUB model. As a result, the amounts of reduction of GHG emissions were estimated 330 MtCO_2eq/year in 2050. Top 10 countries accounted for 64% of the reduction potential. “Breeding management” is the most effective technology in many countries in Africa region.

 Climate change impacts and its mitigation measures can exacerbate poverty by causing consumption losses among low-income groups through changes in average income, income distribution, and prices. It’s unclear how poverty changes when these impacts are considered comprehensively, and which factors affect poverty and to what extent. This study investigted the impact of climate change mitigation on global poverty and its factors, considering the economic impacts of both climate change and its mitigation measures comprehensively. The results showed that climate change mitigation would increase poverty headcount up to the middle of the century, but decrease it by the end of the century, compared to the case without climate change mitigation. This would be attributed to the high-income loss due to climate change mitigation measures until the middle of the century and significant reduction of the consumption loss of low-income groups due to climate change impacts at the end of the century.

 The economic cost of climate change mitigation measures is one of the main concerns when making policy decisions. There are several ways in which developing countries and developed countries can share the burden of climate change mitigation measures, but no study has examined the difference in impact when developed countries offer the financial support for investment to developing countries. Therefore, this study attempts to clarify the amount of financial support for investment from developed countries to developing countries necessary to avoid macroeconomic losses in developing countries and the economic impact on developed and developing countries under a scenario in which the 1.5°C target is achieved for the entire world. The results show that the required amount of financial support is about 3% of GDP of developed countries, and that the cumulative consumption loss rate for 2020-2100 is reduced from 12% to -1.6% for developing countries and increased from 3.0% to 5.8% for developed countries. Further study is needed on the realism of the assumptions made in this study, to translate the results of this study into feasible policies.

 The effectiveness of the international grid has been highlighted in decarbonizing the power system in East Asia. However, its role for achieving net-zero emissions by 2050 has not been evaluated. This study aims to develop a power system model focusing on four East Asian countries and analyze the impact of utilizing the international grid on the power system to provide insights into the planning of power systems. As a result, the international grid has facilitated the integration of solar and wind resources in China and Mongolia, reducing the cumulative additional system costs for East Asia by 7% since 2040. The impact within Japan includes a decreased reliance on solar power in Hokkaido due to electricity imports and the need for increased domestic interconnections in western Japan, highlighting the importance of considering these factors during the planning of power systems.

 Pyrogenic organic matter after wildfires becomes more thermally recalcitrance, however, its characteristics vary depending on the type of combustible material and combustion properties. In this study, thermogravimetry differential thermal analysis (TG-DTA) was conducted on burned samples from the Nishinomiya wildfire of 2021 (burned area: 167 ha) to establish conditions for analyzing the characteristics of pyrogenic organic matter in a general ignition loss test. As a result, organic matter that burns at approximately 300 and 400°C in an air atmosphere was confirmed in the unburned samples, while only substances that burn at approximately 400°C were observed in the burned samples, suggesting that cellulose had been burned off. The 𝑅𝑅50 index of thermal recalcitrance was consistent with values obtained in previous studies. Moreover, the TG-DTA was conducted at fixed temperatures of 300 and 400 °C. The ignition loss of the unburned and burnt samples showed little difference at 400 °C and a 20-30% difference at 300 °C, where the characteristics of the pyrogenic organic matter can be indicated even by the general ignition loss test.

 It is widely acknowledged that efforts aimed at conserving water quality have resulted in a decrease in the inflow load to Lake Biwa. However, significant concerns have been raised regarding the reliability of the “unit-load” approach upon which this assumption is predicated. To address this issue, our study enhances the existing hydrological and substance cycle model for the Lake Biwa basin by incorporating additional functionalities. These enhancements enable us to assess the historical change of the inflow load and compare it with the traditional unit-load method. The model incorporates Total Organic Carbon (TOC) for organic matter, integrates a model for Suspended Solids (SS) generation, and includes mechanisms for change in forms and substance decomposition processes. Our findings suggest that the rate of load reduction over time was significantly slower compared to the unit-load method. This is because the model effectively calculates variations in meteorological conditions, purification and sedimentation processes, as well as load from nonpoint sources during rainfall events. The results indicate that future climate change may lead to an increase in inflow load.

 In order to restore the spring water ponds on the Musashino Upland, which are valuable waterfront areas of the urbanized area, it is necessary to elucidate the hydrological process. This study performed a hydrological analysis using a simple structure consisting of storage tanks which was proposed in the 1980s for Sanpoji Pond in Shakujii Park to an eight-month analysis from January 1 to August 31, 2023. The main points newly taken into consideration in the model are that the amount of groundwater pumped is added to the amount of pond runoff, and the amount of loss due to outflow outside the groundwater recharge area is taken into account. As a result, the Nash-Sutcliffe efficiency of daily pond runoff exceeded 0.7, and the hydrological model showed good reproducibility. Furthermore, based on the correspondence between measured values of groundwater level and analytical values of groundwater storage, we showed that the effective porosity of the aquifer may change in response to heavy rain. From the above, we were able to present an example of the hydrological characteristics of a spring pond on the Musashino Plateau where spring water has dried up.

 An artificial neural network (ANN) was constructed to predict riverbed deformation along the Mogami River for up to 14 years. This study utilized river survey data and numerical simulations to develop and validate the ANN's predictive capabilities. The explanatory variables considered were the river discharge and initial riverbed slope. However, the ANN model, trained solely on river survey data, exhibited poor predictive performance, yielding a coefficient of determination of -1.805. In contrast, the ANN model trained on numerical simulation data demonstrated superior predictive accuracy, achieving a coefficient of determination of 0.810. Nevertheless, this model faced limitations in predicting riverbed deformation over periods longer than the training data or in scenarios with different initial riverbed deformations. Subsequent analysis revealed that restricting the explanatory variables to the initial riverbed slope maintained a high coefficient of determination, even for extended prediction periods beyond the training data. This under-scores the significance of the initial riverbed slope as a crucial variable for accurately predicting long-term riverbed deformation.

 In recent years, the frequent occurrence of extreme rainfall has necessitated flood control cooperation even in utility dams. Meanwhile, increasing the power generation capacity of hydropower is considered one of the important challenges for contributing to carbon neutrality. This study developed and analyzed an operation method to enhance the flood control function and increase the power generation capacity of reservoir-type hydropower using the Deep Reinforcement Learning method (DQN). The results showed that the DQN in this study could flexibly respond to data from periods not used in training. Additionally, it is inferred that relatively high power generation was achieved due to the possibility of operating at high water levels throughout the year. Furthermore, during floods, the water level never exceeded the full water level, and the peak flow during floods could be appropriately reduced. Moreover, the water level during the flood season was maintained lower than during the non-flood season, indicating that water level operation in preparation for floods was implemented.

 This study assessed the uncertainty of potential inundation impacts using multiple global climate models (GCMs) and proposed effective adaptation measures against sea level rise. Based on scenarios covering the coastal areas of Japan for 2100, the estimated economic damage varied from 218.0 to 278.2 trillion yen for SSP1-2.6, and from 423.7 to 576.8 trillion yen for SSP5-8.5. The efficiency of protection was calculated by classifying potential inundation areas in detail and used to reveal efficient protection options for preventing most inundation impacts at little adaptation cost. Furthermore, a cost-benefit analysis of multiple adaptation scenarios showed that it is effective to protect inundated areas according to the priority for protection. Comparison of these adaptation scenarios suggested that it is more effective to protect an inundated area not once, but several times in later years.

 The purpose of this study is to obtain rare knowledge of countermeasures against disasters utilizing ecosystems by clarifying the characteristics of trees that are expected to have sediment discharge buffer effects based on universal environmental field conditions such as tree spacing, area, average tree age, average tree height, and slope inclination. Based on numerical geographic information and aerial photography using a UAV, the sediment production buffer effect was verified by focusing on the environmental conditions such as the distance between trees. As a result, cases of sediment buffering were extracted in areas where sediment production was concentrated. The possibility that environmental factors that form a forest zone, such as the distance between trees, contribute to the sediment buffer was also identified. The environmental factors of forest formation change over time, and the need for maintenance and management of forests becomes important.

 The purpose of this study is to compile knowledge that can induce the relationship between the forest aspect, tree species, and slope failure. In order to obtain knowledge, a comparative analysis of the environmental conditions in the mountainous area including the forest types and forest types was attempted with the heavy rainfall that occurred in August 2022. The study consists of a comparative analysis of multiple watersheds using slope failure records and numerical geographic information, and a detailed analysis of watersheds using information obtained from UAVs. The comparative analysis of multiple watersheds showed that slope failures were more frequent in the Quercus distribution area on steeply sloping slopes. The dense watershed analysis revealed that the Quercus serrata distribution area has a mixture of tree species and a large difference in tree height. Slope failures were more likely to occur in areas with large height differences.

 This study investigated the influence of the presence/absence of linear structures such as roads on inundation propagation through numerical experiments using the 2015 Kanto/Tohoku heavy rainfall disaster as a case study. The numerical experiments revealed that the propagation speed of inundation flow differs by up to half depending on the presence/absence of linear structures such as roads. Specifically, the maximum speed of inundation flow without roads was 0.49 m/s, while that with roads was 0.27 m/s. Since the estimated walking speed for people with walking difficulties or physical disabilities is 0.5 m/s, it was suggested that the presence/absence of linear structures such as roads plays an important role in ensuring that evacuees have a sufficient distance to travel before the inundation flow reach them.

 Typhoon Hagibis 2019 caused combined inundation damage including overflows from Abukuma River and Ouse River, and inundation from sewage pipes in the Koriyama urban area, where two rivers converge. The rise in the water level of the Oise River was affected by the backwater from Abukuma River. This study developed flood analysis model which takes in to account river, sewage and inundation flows as well as sluice gates and drainage pump operation around the the criver onfluence. This model was applied and validated to Typhoon Hagibis 2019 and estimated the proportion of inundation sources in the target area. The results showd that 82.8% of the inundation was caused by overflow from Ose River due to backwater from Abukuma river. Since the model can represent individual source of combined inundation, it is exptedted to be useful for the influence of the main river development on the inundation of its tributaries and the effective operation of sluice gates and drainage pump stations.

 This study presents the development of a pluvial inundation model for the Oizumi district of Toyama City, which was affected by flooding on August 13, 2022, and quantitatively demonstrated pluvial inundation countermeasures. The analysis results were validated, and the effectiveness of various flood mitigation measures was quantitatively demonstrated through numerical simulations. Our findings show that implementing multiple flood control measures resulted in a comparable reduction in inundation area compared to individual measures in several scenarios. This similarity in effectiveness can be attributed to the significant impact of the most effective measures, which may diminish the added benefit of supplementary measures. Consequently, combining multiple flood control measures, while avoiding redundancy, is recommended for maximizing the reduction of inundation damages.

 This paper estimates the future amount of photovoltaic panel waste generation in Shiga Prefecture until 2060. Furthermore, the sensitivity analysis of the effects of the following factors on the amount of panel waste and the weight of the panels waste generation ; w/w.o consideration of time related deterioration, the average lifetime between 20 and 30 years, and changes in the amount of newly installed panels.

 The actual power generation output capacities are 5% and 7% lower than the target capacity in 2030 and 2050, respectively. The amount of panel waste will not reach a clear peak until 2060. After a rapid increase, from 2045 onward it remained flat or increased slightly in the range of 86 to 130 MW. The weight of panel waste is expected to peak at 6,000-8,000 tons, but if new introduction is not promoted, it will be around 5,000 ton. Under the condition of minimizing fluctuations in the weight of panel waste generation, the amount of recycling required between 2035 and 2060 is estimated to be approximately 6,000 ton.

 This study aimed to understand the dynamics of river space use based on mobile spatial statistics data. This study proposed a method to estimate the number of visits to river spaces and to the river waterfront facilities, considering the areal ratio of the river space to the data mesh, visiting time, and visitors living area. The estimated results for the 109 target rivers using the proposed method captured the inter-rivers variability well (R=0.92) but were about 10 times higher than the values obtained from the national field survey of the river space use in average. Our analysis suggested that the population dynamics can be captured with a certain degree of accuracy both on an annual and daily basis. In the estimation of the number of visitors to 240 river waterfront facilities in Japan, multiple regression analysis using the number of visitors as the objective variable was performed. Though our multiple regression analysis did not necessarily result in developing an accurate model, we found that the accessibility to the river water facilities showed statistically significant results, indicating its influence on the number of visitors.

 In this study, we conducted a questionnaire survey among individual farmers and agricultural corporations to identify their willingness to implement agrivoltaic systems. The results of a simple tabulation showed that only 30% of all respondents were aware of agrivoltaic systems, and 20% of all respondents were willing to implement agrivoltaic systems. A chi-squared test on the willingness to implement agrivoltaic systems by individual farmers and agricultural corporations revealed that individual farmers were significantly more likely to be unwilling to implement agrivoltaic systems or to implement agrivoltaic systems under a business system in which the farmer and the power producer are different, while agricultural corporations were significantly more likely to implement agrivoltaic systems under a business system in which the farmer and the power producer are the same. A regression analysis of the factors influencing individual farmers’ willingness to implement agrivoltaic systems showed that concerns about technical and environmental aspects of agrivoltaic systems, interest in agrivoltaic systems, and crop type had significant effects on individual farmers’ willingness to implement agrivoltaic systems.

 The negative rumors have damaged citizens' and companies' benefits for many years. The purpose of this study is to investigate the robustness of consumers' decision-making for eco-friendly goods under the conditions of some negative rumors. A hypothetical market method assuming a dishwashing liquid is employed for investigating the impacts of rumors. Willingness-to-pay (WTP) values are asked for respondents under information conditions 1) no information about negative rumors, 2) simple information about negative rumors, 3) more specific information. The median WTP values per a good on eco- and non-eco-friendly goods are found to range from 210 yen to 300 yen, and from 220 yen to 290 yen, respectively. The results of the study suggest that the value of environmental goods is robust to negative rumors, and that negative rumors with short content may cause more damage.

 Japan has the second lowest per capita meat consumption among the 38 OECD countries. It is known that transitioning to a diet with lower meat consumption has a large effect on reducing greenhouse gas (GHG) emissions. In this study, we defined the recommended diet in Japan as the Japanese diet and analyzed the effects on the environment and food systems in the case where the low meat consumption Japanese diet becomes widespread globally. The results showed that the spread of the Japanese diet increased global GHG emissions in 2050 by 6.6% compared to the baseline scenario without dietary changes. This increase was mainly due to a rise in GHG emissions in Africa, driven by changes in global food prices and demand, leading to increased production of rice and meat in Africa, where they can be produced more cheaply than in other regions. In order to promote the Japanese diet as an environmental measure, it is necessary to shift from meat to protein sources such as soybeans and seafood, and to take measures to reduce methane emissions from rice cultivation.

 This study assessed the vision of Japan's power sector in 2040 by using conjoint analysis based on the results of a model intercomparison project. The attributes of the conjoint analysis were safety, economic efficiency, environmental suitability, and energy security, which are the basic principles of Japan's energy policy. The levels of each attribute were set based on the results of scenario analyses assuming the achievement of Japan's long-term emission reduction targets by using the multiple energy system and integrated assessment models. The results of the conjoint analysis showed that the preferences for lower economic performance, lower safety, and lower energy security were significantly low. Economic efficiency and energy security were the dominant factors in the relative importance assessment, accounting for about 45% and 38%, respectively. Meanwhile, environmental suitability had no significant effect on the preference of the visions. This may be because that all the options of CO₂ emission targets under the long-term emission targets we presented, which is the index of the environmental suitability, are ambitious compared to current levels and, therefore, are not taken seriously by the respondents; instead, other attributes that they consider may directory affect their lives influence their preferences of 2040 visions.

 The anticipated effects of climate change include an increase in both the frequency and intensity of heavy rainfall, potentially leading to a higher likelihood of areas becoming isolated due to frequent road disruptions caused by slope failures. This research simultaneously evaluates the current and future probabilities of road disruptions from slope failures during heavy rains and examines the potential for resulting isolated areas, while also projecting changes in these probabilities. The findings reveal statistically significant increasing trends in the likelihood of isolated areas for the periods 2031-2050 and 2081-2100, compared to the base period, regardless of Shared Socioeconomic Pathways (SSPs). Furthermore, the findings indicate that the most substantial increase in the likelihood of isolated areas could reach up to 17% under SSP1 and 30% under SSP5.

 For long-term sediment management in a watershed, it is necessary to quantitatively estimate sediment transport in the entire watershed from upstream to downstream, taking into account changes in rainfall characteristics. Many studies have been conducted in each of mountaineous, riverine, and coastal area, but the estimation method has not been established. The objective of this study is to construct a sediment production estimation model for Japan by combining the soil erosion model (RUSLE) and the sediment delivery ratio (SDR), and to project the future sediment yield. The SDR equation is constructed with dam deposit data at 64 watersheds of first-class rivers in Japan. The sediment yield in the period 2091-2110 projected by using the RUSLE results and SDR equation shows that the sediment yield would increase by a factor of 1.25 compared to the period 1991-2010.

 Global warming is expected to cause more severe water-related disasters, such as sea level rise, increased precipitation, and activation of tropical cyclones. Therefore, countries located in coastal areas are concerned about the increase in flood damage, and at the same time, it is desirable to take adaptive measures based on accurate inundation damage prediction results. In response to these issues, the authors have developed a global levee data set and have been assessing flood damage using this data. However, the effectiveness of levee data for coastal areas of multiple countries has not yet been verified nor has inundation damage been assessed. In this study, we evaluated storm surge inundation damage using levee data for the entire coastal areas of East and Southeast Asia. As a result, we confirmed the effectiveness of levee data for a wide area and summarized the amount of inundation damage for each administrative district in the countries in East and Southeast Asia.

 In recent years, flood disasters have occurred frequently due to heavy rainfall, and the importance of evacuation of residents has been increasing and basin-wide flood control is being promoted. Hence, hazard information needs to be improved. However, small and medium-sized rivers lack hazard information. Therefore, the purpose of this study is to propose a flood inundation analysis method suitable for small and medium-sized rivers with insufficient data by using topographic elevation data. The river flow discharge was calculated using the assumed maximum rainfall in Hokuriku region. River cross sections are generated for each granularity of topographic elevation data by 5-meter mesh topographic elevation data, 1-meter mesh aerial laser survey data. Calculation of levee breach locations using 1-meter mesh aerial laser survey data. Flood inundation calculations were performed using 5m mesh topographic elevation data for flood plain. From the results of the analysis, use of river cross-section data prepared by the most detailed data in the existing is recommended. In addition, there is a possibility that potential levee breach locations could be investigated by aerial laser survey data and field survey data.

 In this study, we analyzed the frequency of heavy rainfall events and meteorological factors in the Ishikari River basin over the past several decades. Observations indicate that the frequency of heavy rainfall events has increased since the late 1990s, especially the number of events caused by stagnant fronts has doubled. The 1981 flood, the largest ever recorded in the basin with average daily precipitation exceeding 100 mm/day, is known for being caused by a front and a distant typhoon that brought heavy rainfall over a two-day period. Furthermore, using historical experiments of ensemble climate prediction information, it was found that the probability of a heavy rainfall event exceeding the historical maximum was more than twice that of a heavy rainfall event caused by a frontal pattern than by a combination of a frontal pattern and remote typhoon.

 Global climate change has led to an increase in the frequency and the intensity of heavy rainfall events. As a result, flooding has become more frequent in recent years. In Japan, the concept of “green infrastructure” has been introduced as a countermeasure, and measures to actually put it into operation have been in motion since 2013. Green infrastructure for flood control is mainly installed in administrative facilities such as public parks, and most of them are small scale. Based on the principle of flood control in a river basin, we believe that flood control functions should be introduced to large-scale private facilities that have not yet been utilized as green infrastructure. In this study, we focused on green spaces of large-scale factories, which are required by the Factory Location Law to have a certain scale of green space. Also, we proposed that the land should be used as a storage and infiltration facility, and examined the effectiveness of such a facility. The results showed that the effect was comparable to that of the existing flood control reservoirs.

 In 2021, the Japanese government made a major shift in its flood control policy to River Basin Disaster Resilience and Sustainability by All (RBDRSA) in view of the recent increase in the severity and frequency of flood and sediment disasters. It is no exaggeration to say that RBDRSA, which requires the cooperation of many stakeholders, poses an even higher hurdle than before in terms of careful explanation, promotion of understanding, and consensus building. In this study, a numerical experiment was conducted in the lower basin of the Jinzu River in Toyama Prefecture, Japan, to quantitatively clarify the effects of flooding on the socioeconomic damage caused by flooding in downstream areas. In this numerical experiment, two cases of RBDRSA option were set up: one in which the entire Nakajinzu basin was flooded, and the other in which a part of Fuchu machi was accepted to be flooded up to below floor level. Numerical experiments showed that the maximum benefit ratio of the economic damage caused by the watershed flood control menu was 1, 081.0% in the case of the Nakajinzu reservoir and 194.7% in the case of allowing flooding (Fuchu machi wide flood control area). The results of this study can be evaluated as one of the methods to provide information and data necessary to promote understanding from public people and consensus building in RBDRSA.

 Through disaster education campaigns in Playas City, Ecuador, this study identified the need for a tsunami risk communication methodology tailored to residents' map reading skills. A survey revealed low adoption rates of hazard maps, limited awareness of tsunami risks, and challenges in map reading skills among residents. Given high smartphone penetration, a map application displaying current location, evacuation routes, and inundation areas was developed to complement map reading skills. Experimental testing with residents showed a significant increase in tsunami risk awareness after viewing both hazard maps and the map application, with a notably larger increase observed with the latter. However, the study also revealed there was no significant change in evacuation intention, highlighting an area for improvement.

 Disaster education content for flood was developed using 3D city data and Minecraft. The educational effectiveness of this content was evaluated through outreach classes at elementary schools. Results indicated that: 1) Geographical features of actual cities were accurately replicated in the game's 3D space, 2) The extent of flooding and water depth in the 3D space were consistent with existing hazard maps, and 3) The use of the developed content showed an increased willingness to share information with family members, thereby effectively capturing the interest and curiosity of the students. This content enables students to learn about their local flood risks in a self-directed and proactive manner, indicating it as an effective disaster education tool.

 To examine the current situation and trends of disaster prevention education at school events, we conducted text mining particularly addressing social facility tours, Saturday classes, and evacuation drills described on the websites of Osaka municipal elementary schools during the 2022 fiscal year. Results showed that students engaged in hands-on learning at a disaster prevention experience facility in Osaka City during a social facility tour. During Saturday classes, training such as disaster prevention studies, evacuation drills, returning home in groups, and student–parent pick-up drills were conducted cooperatively with the elementary school and the local community, taking advantage of the district characteristics. Evacuation drills were often held on Saturdays, in January, and before the rainy season and typhoons. For typhoons, the students participated in training of returning home in groups and the Osaka 8.8 million drill. The use of the Osaka City Disaster Prevention Experience Facility, Saturday classes held in cooperation with the local community in each ward, and three-stage tsunami evacuation drills were particularly noteworthy.

 The purpose of this study was to obtain more accurate estimates of the height of coastal protection facilities in order to assess more realistically flood risks along the Japanese coast. This was achieved by evaluating the impact of tsunami height on coastal areas and estimating the height of coastal protection facilities, considering the obtained results. In this study, numerical calculations were conducted for 16 tsunamis in total, resulting in estimates of tsunami height along the Japanese coast. The obtained results were validated with the values in the published reports, confirming that the estimated tsunami heights accurately represent the characteristics of each tsunami. Considering the influence of tsunamis yielded significant improvements in estimating the height of coastal protection facilities, especially on the coast of the Pacific Ocean. A comparison with the previously measured values by other studies showed that the estimated height of coastal protection facilities in the coastal area of Gobo City, Wakayama Prefecture, demonstrated a good agreement compared to the previous research.

 This study utilized the grided Gross Domestic Product (GDP) and Gross Regional Product (GRP) as indicators of inundation damage due to sea level rise to calculate the nationwide and regional loss amounts and loss ratios, and analyze the impacts on the regions of Japan. GDP loss amounts for the year 2100 were estimated to be 39.1 trillion yen under SSP1-2.6, 28.5 trillion yen under SSP2-4.5, and 65.2 trillion yen under SSP5-8.5, and these amounts were compared with those from existing damage estimation methods. The three metropolitan prefectures of Tokyo, Aichi, and Osaka accounted for 70% of the total GDP loss. It was found that the distribution of damage varies depending on the characteristics of the municipalities prone to inundation, for example, those found within Saga, Mie, Kochi, and Kumamoto prefectures, as well as the three metropolitan prefectures.

 Although dam reservoirs have been actively developed in the Mekong River basin, the sparse hydrological observation network makes it difficult to explain whether changes in river flow are caused by dam reservoirs or not. Therefore, in this study, the RRI model is used to reproduce the flow without the impact of the dam reservoir using the observed flow data before the dam reservoir was developed and reanalyzed precipitation data as input datas for nine stations along the main stream of the Mekong River. The impact of the reservoir development on the flow is evaluated by comparing the reproduced flow for the observed flow with the MK test. As the results, The observed flow rates were significantly higher than the reproduced ones, with a decreasing trend in the high water flow rate, an increasing trend in the low water flow rate, an increasing trend in the dry season, and a decreasing trend in the rainy season. These results suggest that dams in the Mekong River basin play a role in flood control during the rainy season and stabilize low water during the dry season.

 In response to the increasing frequency of water-related disasters attributable to climate change, a river-water flow index that integrates synthetic aperture radar (SAR) and multispectral data has been developed in this study. The basic maps of river environment are generated every five years through national censuses based on surveys of river environments and vegetation distributions. However, these maps may not accurately reflect short-term environmental changes, such as vegetation growth over a five-year period. Hence, we focused on satellite imaging that facilitates periodic observations. SAR, an active sensor, effectively captures the densities of objects and materials on the ground. Although the integrated-data-based index may differ according to seasonal variations and coverages, our preliminary findings from the Kuji River case study suggest its potential as an effective evaluation index for river water flowability.

 This study aims to clarify appropriate methods to reduce the impact of phosphate on the coral reef ecosystems, which are in decline due to multiple global environmental impacts, the current phosphorus content of agricultural soil was investigated and analyzed in the Todoroki River watershed, Ishigaki island. In addition, from the standpoint of the precautionary principle, a factorial linkage structure analysis was also conducted on the reduction of point source load to analyze negative factors related to composting and utilization of livestock manure.The results showed that phosphorus is likely to be discharged from soils with high pH, soils with low phosphate absorption coefficients, some soils in sugarcane summer plantings and stubble cultivation, and soils near composting yards. Furthermore, to promote the intra-regional cyclic approaches of phosphorus in agriculture, it was found that various activities are necessary such as increased collection of livestock wastes, increased composting, increased use of compost, increased markets for compost, a shift to environmentally positive agriculture, and others.

 In this study, we conducted spatial information analysis on reservoirs in Hyogo Prefecture, which boasts the largest scale in the country, to examine the changing environment surrounding reservoirs. Res-ervoirs have played a crucial role as water resources for agriculture, water supply, and other purposes in local communities for a long time. However, the aging of facilities due to long-term use, increased risk of disasters caused by recent severe weather events, and the lack of personnel to manage reservoirs due to aging demographics have significantly altered the surrounding environment. Through this research, we aimed to clarify the risks of tsunami, floods, and sediment disasters, as well as the regional characteristics of reservoirs. Additionally, we conducted a questionnaire survey targeting reservoir managers to reveal the actual state of reservoir management and the environmental and disaster prevention functions of reservoirs.

 Recently, the insufficient management of small to medium-sized rivers due to population decline has been a major challenge in Japan, thereby, an adaptation to future degradation of social infrastructure is required. However, the impact of the depopulation and related environmental changes (e.g., land-use changes) on riverine ecosystem is not well understood. This study aims to evaluate the benthic macroinvertebrate communities in small river chatchments under depopulation in the Kiyotake River catchment in Miyazaki Prefecture. Based on nonmetric multidimensional scaling, the community was most characterized by water quality changes associate with population changes in the study catchment. Generalized linear models revealed that the decline in watershed population led decrease in density of a macroinverteberate habit type “gliders”. This result suggests that decline in nutrient load impedes growth of riverbed algae, which is important food resource of dominant biological groups in the gliders.

 This study aims to evaluate the hydropower potential of irrigation reservoirs throughout Japan, using a neural network model to estimate the flow regime and calculate the hydropower generation. The results showed that reservoirs throughout Japan have the potential to generate between 14 GWh/year and 63 GWh/year of electricity. The annual hydropower generation potential of irrigation reservoirs, estimated according to the flow regime of eight large agricultural irrigation dams, was found to range from 44 GWh/year to 180 GWh/year. In addition, the results show high hydropower potential in Kochi, Hyogo, Kagoshima, Miyazaki and Oita prefectures, with the maximum estimated hydropower generation of 16 GWh/year, 8 GWh/year, 4 GWh/year, 4 GWh/year and 3 GWh/year, respectively.

 The objective of this study was to establish basic information on vegetation growth in the river channel. Specifically, the vegetation in the river channel was classified based on the Normalized Difference Vegetation Index (NDVI) calculated from satellite images and the average annual change in NDVI. Differences in classification were also examined by first-class water systems and upstream and downstream. The results showed that the vegetation growing in the river channels of first-class water systems throughout Japan was generally herbaceous. The NDVI tended to increase in the upstream and downstream areas, mainly in eastern Japan, and there were many forested areas with positive values of NDVI change. In western Japan, however, there was a trend toward more herbaceous species with positive NDVI change and fewer forested areas with positive NDVI change. In addition, differences in herbaceous species growth were observed by first-class water systems upstream and downstream. The basic information developed in this study is expected to contribute to effective river channel management planning for flood damage reduction and global warming mitigation.

 This study conducted a nation-scale evaluation of changes in CO₂ emissions from a ground-source heat pump system when the effective thermal conductivity increases due to groundwater flow, resulting in apparent thermal conductivity. The evaluation was performed for different office buildings (with floor areas of 300 m² and 2000 m²) and various Darcy flow velocities (50, 100, 250, and 500 m/year). The regionally averaged changes in CO₂ emissions increased with higher flow velocities, but remained within a range of a few to ten times. The changes in the same assumptions of Darcy velocity were larger and more variable in warmer regions compared to colder regions. For larger buildings, the changes in emissions were smaller in warmer regions and larger in colder regions compared to the proportional increase in building size due to the product characteristics of the heat pumps. These results indicate that considering apparent thermal conductivity improves the accuracy of CO₂ emissions estimates, while site-specific estimates based on thermal loads and groundwater flows become crucial.

 In Northeast Thailand, where 60% of the nation's rice fields are located, the majority of rice cultivation depends on precipitation, making it highly sensitive to changes in weather patterns. Given this background, this study introduces a model developed to estimate rice planting dates and areas using detailed daily weather data, topographical information, and land usage patterns. This approach sets itself apart from previous research by integrating daily precipitation fluctuations to estimate the planting dates. Model calibration was conducted using observational data from 2005, resulting in errors of 8.66%. Model validation was conducted using data from 2004 and the error was 13.9 %, indicating a reasonable replication of observed values. The model was employed to analyze the impact of variations in precipitation from 1981 to 2017 on planting dates. The results show considerable shifts in planting dates, characterized by a trend towards increased variability and postponement in planting. These adjustments are primarily attributed to changes in precipitation at the onset of the rainy season. Furthermore, by inputting future precipitation data, we estimated the future planting dates. The results showed that the trend of delayed planting dates would continue in the near future and would shift to earlier dates in the distant future.

 Climate change is one of the most significant long-term challenges faced by humans. Possible future scenarios on both climate and socioeconomic changes are commonly used to assess the impacts and adaptation measures of climate change. Shared socio-economic pathways (SSPs) are widely used in socio-economic scenarios for global future projections. The data associated with Japan SSPs, which are downscaled by global SSPs, include population and land use. However, it has been discovered that the building area tends to decrease more than the actual land area owing to the simplistic method employed, wherein the building area changes in proportion to the population. Therefore, the aim of this study is to estimate the future building area by 2100 by classifying the building areas into industrial, commercial, residential, and other uses. The land area for residential buildings was estimated by determining which buildings will be utilized and which not, based on vacant house projections.

 Questionnaire surveys were conducted in January 2024 and October 2023 of Okukuji apple and Daigo lacquer farmers in Daigo town, Ibaraki Prefecture, that examined climate change impacts and the farmers’ adaptations. Previous studies have investigated the overall impact of climate change on agriculture in Ibaraki Prefecture, including rice and vegetables. However, this study conducted surveys on the impact on specific crops within a municipal area. These crops are deeply connected not only to agriculture but also to local tourism and culture.

 Most respondents reported recognizing signs of climate change, such as high temperatures, and had already experienced some damage due to climate change, such as decreased yield, poor quality, and heat stress during work. In addition, factors affecting the adaptive behaviors included business ingenuity, perception of positive climate impacts, and awareness of climate change.

 In previous studies, emissions estimated by integrated assessment models have been downscaled to the grid and input into earth system models. However, the current method cannot account for future land cover changes. In this study, we developed a downscaling model coupled with a land cover partitioning model, and developed a downscaling method that takes future land cover into account. The downscaled emissions were then input to an atmospheric chemistry transport model to estimate pollutant concentrations. The objective of this study was to evaluate the impact of land cover change on air pollution by comparing the results with existing methods. The maximum difference in concentration changes between the methods between now and the future was estimated to be 6.4 percentage points. However, the difference in concentration change was small, and it was concluded that the impact of land cover change on air pollution is small.

 Growing concerns have arisen in Jakarta due to the worsening impact of urban flooding, leading to an escalation in cases of diarrhea. This research, conducted in response to the January 2020 floods, aimed to clarify the relationships between water usage patterns and diarrhea. By using satellite image, inundated areas were identified, followed by a questionnaire survey to assess actual water usage in these regions. An analysis was then conducted to examine the relationship between drinking and utility water sources and diarrhea. The findings revealed that having a water supply contract was linked to increased instances of diarrhea after flooding. Additionally, evacuation status is also considered to be related to be diarrher during floods. Possible contributing factors include the deterioration of water quality following flooding, the social circumstances of households with water supply contracts, evacuation behaviors, and poor hygiene conditions in shelters. Therefore, further exploration and additional research are deemed necessary to validate these findings and delve deeper into the underlying issues.