The objective of this study is to quantitatively assessment future community scenarios that take into account climate change and socioeconomic factors using the Climate Change related Quality of Life (CC-QOL) indicator. First, a conjoint analysis was conducted on citizens' perceptions of CC-QOL indicator based on a questionnaire survey. The results revealed that perceptions of climate change risk vary with life stage and adaptive capacity with aging, as well as with occupation and understanding of climate change. In addition, multiple community future scenarios were developed for Aichi Prefecture, and CC-QOL values were evaluated on a 500m mesh scale, revealing that disparities among regions and attributes will become increasingly large in the future. This indicates the need to monitor both climate change impacts and citizens' perceptions, which vary from region to region, and to promote localized understanding of climate change risks and adaptation measures.

 It has been a problem that fish stray into the water intakes of dams and weirs and are injured. In particular, the depletion of Anguilla japonica and Plecoglossus altivelis, which have a high value in fisheries, is a serious problem that may damage the local economy. Light is one of a methods of inducing repellent behavior of fish. The effects of continuous and blinking light on the avoidance behavior of fishes have been elucidated, but very few studies have been conducted on Anguilla japonica. In this study, the blink frequency of flashing light were changed from 0.3 to 15 Hz and also the illuminance from 60 to 1300 lx using yellow-phase Anguilla japonica in 300 mm total length. It was found that Anguilla japonica avoided the flashing light in the present conditions and also that the repellent characteristics became more pronounced as the blinking frequency and illuminance increased. The range of blink frequency and illuminance must be expanded more than this study, so that the stray rate will be decreased and the population of Anguilla japonica will be increased.

 There is no definitive agreement about the appropriate geometric form and hydraulic conditions of eel ladder. At present, it has been recognized utility of bunches of brushes, mesh mat, boulders and cylindrical protrusions as the material of eel-ladder bottom, but it is not cleared that which material is the most suitable for Anguilla japonica migration. In this study, it attempted to clarify the effect of varying material of eel-ladder bottom and discharge on migration characteristics of Anguilla japonica. It was found that migration and migration success rates were higher in the case of cylindrical protrusions. On the other hand, those rates were the lowest in the case of bunches of brushes. It is assumed that Anguilla japonica can rest by wrapping body under the condition of cylindrical protrusions. Therefore, it is suggested that the best material of eel-ladder bottom is cylindrical protrusions for Anguilla japonica migration.

 Following the Second World War, a major shift toward a more Westernized diet occurred in Japan. However, fish meat is attracting renewed attention as a high-quality protein source that is low in fat and rich in micronutrients. Sea desertification, which is widespread along the Japanese coast, has increased feeding pressure on species that feed on algae, such as rabbitfisf, Siganus fuscescens. This fish contains large amounts of flavor components, such as inosinic acid. In this study, we report the results of a taste test of Siganus fuscescens and discuss its potential as a food product. The participants cited taste as the most important characteristic of raw fish, while both taste and texture were deemed important for fried fish. Smoked Siganus fuscescens, as well as risottos and salads containing the fish, were rated positively. In addition, food preferences differed according to participant characteristics.

 In this study, we focused on the forest surrounding a shrine in Hyogo Prefecture, which is a familiar semi-natural space in the area. We grasped the characteristics of vegetation and maintenance forms, etc., and pointed out the vegetation of shrine forests that are resistant to disasters, location requirements, and disaster risks. We also clarified the ecosystem services of the shrine forest and clarified its value as a local resource.

 Coastal flood area is usually evaluated using a digital elevation model, but it is considered that the results are overestimated because the digital elevation model does not include the information of coastal protection structures height. Construction of coastal protection structures is progressed based on the construction standard; however it is not completed countrywide. This study focused on the estimation of the height of coastal protection structures in Japan based on the assumption that the coastal protection structures are constructed at least the level up to the usual height of sea surface caused by tide, waves and storm surge. The estimated results was verified by the coastal protection structures height measured in field investigation conducted in this study. The results showed a good agreement with the measured height at the coast where external forces are assumed to affect to the water surface height. However, on the coast affected by tsunami, the results showed large differences between the estimated and measured heights, and the estimated height of tsunamis should be included in the estimation.

 Adaptation measures for sea level rise due to climate change will become increasingly important in the future. Based on multiple scenarios, the present study focused on protection measures and estimated the cost of adaptation against sea level rise for the coastal areas of Japan, taking into account existing coastal protection facilities. Similar research to date has assessed the potential inundation impact without considering the current level of protection and concluded that the inundated area was approximately 2,300-2,400 km² in 2020, while the present study estimated the area to have been about 1,000 km². The total adaptation cost was estimated to be approximately 1.72 trillion yen for SSP1-2.6, 2.03 trillion yen for SSP2-4.5, and 3.28 trillion yen for SSP5-8.5 assuming adaptation to prevent all such inundation until 2100.

 This study demonstrates the possibility of reducing the amount of open-piled shell particles by using them as a soil structure material. Additionally, it shows the amount of carbon dioxide (CO₂) reduction potential for applying this material to reinforce the backside of river levees by unique geotechnical properties of flat scallop shells. First, the CO₂ emissions associated with the reduction of shell mass due to acid rain were determined by laboratory experiments. Then, this study estimates and evaluates the potential amount of carbon dioxide (CO₂) reduction resulting from the use of scallop shells as an embedded material in shallow ground. Finally, it clarified that the amount of CO₂ emission due to the reduction of shell mass by acid rain depends on the pH of the acid rain and the particle size of the shells etc. In addition, the potential of CO₂ emission reduction by the application to the reinforce the backside of river levees was clarified.

 The electricity supply from variable renewable energy (VRE) is crucial to mitigate global climate change. Although variability of VRE poses integration challenges for the power systems, the impact of climate change on variability has not been clarified. This study aims to assess the climate change impact on the supply potential of VRE and to find implications for the probability of VRE-oriented power systems using the VRE model for the entire world. The results show that climate change mitigation has a positive impact on the technical potential of VRE and that the climate change impact on periods when VRE output is low relative to the annual average is small and that the periods are strongly dependent on regional factors. The results also show that the seasonal variability of large-scale solar PV is greater than that of onshore wind power, but that combining them may mitigate the seasonal variability. On the other hand, it is also shown that even with the combination of solar and wind, it is important to manage the variability when VRE provides the majority of the electricity.

 The purpose of this study was to estimate the economic damage from land loss caused by potential inundation due to sea level rise by 2100 in the coastal areas of Japan, and to compare this estimate with those calculated by conventional estimation methods. We used the posted land prices for residential land and the prices of rice paddies, crop fields, and timber forests to estimate the economic damage from land loss. Average land prices were calculated and interpolated for each municipality. Inundated area and economic damage were calculated under three scenarios: SSP1-2.6, SSP2-4.5, and SSP5-8.5. The potential inundated area nationwide in 2100 was estimated as 2,542-2,707 km² (SSP1-2.6 to SSP5-8.5). The economic damage varied from 158 to 200 trillion yen (SSP1-2.6 to SSP5-8.5) in 2050 and from 185 to 428 trillion yen (SSP1-2.6 to SSP5-8.5) in 2100.

 It has been pointed out that NO_x emissions contribute to the formation of ozone, which has various environmental and social effects, and reduces greenhouse gases such as methane by increasing the oxidation potential of the atmosphere. However, very few studies have comprehensively evaluated these effects. In this study, we estimated the changes in thermal radiation, health effects of ozone, and agricultural effects when NO_x emissions are reduced in a sensitivity analysis manner. The results showed that reducing all anthropogenic NO_x emissions increased global average methane concentrations by 250 ppbv, radiation increased by 8.3%, and both mortality and yield loss decreased significantly. These results indicate that while NO_x emission reductions are effective in solving air pollution issues, they also increase methane concentrations and slightly accelerate global warming, indicating the need for further greenhouse gas emission reductions to simultaneously solve air pollution and climate change issues.

 Tropospheric ozone is known to have a negative impact on plant CO₂ uptake. On the other hand, climate change mitigation generally lead to reductions in emissions of ozone precursors such as NO_x, thereby reducing ozone concentrations. Howerver, ozone impacts on CO₂ uptake by terrestrial ecosystems on by vegetation has not been interpreted in terms of climate change mitigation measures. In this study, we quantifies the ozone impact on Net Biome Production (NBP) under two scenarios, one is without any mitigation policy and the other is equivalent to 1.5 degree target. The results show that ozone impacts are reduced by mitigation measures. For all vegetation, the reduction effect was considered to be large enough, corresponding to 11%-44% of the global reduction in CO₂ emissions from managed forests.On the other hand, the CO₂ emission reductions from managed forests were expected to increase as the ozone impact was reduced, but the amount of change was considered to be small.

 Tropospheric ozone, which has been increasing in recent years, has a strong oxidizing power and is said to have a negative impact on crops, especially on crop yields. This paper clarifies the effects of changes in tropospheric ozone concentration associated with climate change mitigation measures on food consumption and the population at risk of hunger through changes in crop yields, based on climate scenarios. As a result, the global population at risk of hunger decreased by 474, 000 under the scenario corresponding to the 1.5 degree target. By region, large decreases were seen in the Middle East and other parts of Asia, which are still facing severe hunger. It can be said that the secondary benefits brought about by the reduction of these tropospheric ozone concentrations will serve as incentives for the introduction of climate change mitigation measures centered on developing countries.

 Water shortages are becoming more serious due to population growth and climate change. To solve this problem, it is expected that water resources will be exported from water-rich countries to water-poor countries through food trade. However, previous studies that have examined this question by asking "whether comparative advantage can be established in virtual water trade" have conducted their analysis with incomplete predictions of the comparative advantage theory, and have not reached a clear conclusion. In this study, we focused on bilateral crop trade and analyzed the relationship between the volume of trade and the relative abundance of water resources to other ones. The results show that about 60-80% of bilateral crop trade is consistent with the theory. Some previous studies have shown that countries with absolute water abundance in comparison to the world average do not necessarily become crop exporters, i.e., they deny comparative advantage. In this analysis, too, when looking at trade among "net exporters" whose total exports exceeded their total imports, absolute water endowment was not a source of exports. However, when we focus on the "relative abundance of water resources compared to population or capital" in light of the original definition of comparative advantage, we find that comparative advantage is also established in trade among net exporters. In other words, trade in water resources through food is economically efficient.

 Agricultural sector accounts for approximately 70 % of global water withdrawals, which shows that food production requires a large amount of freshwater resources. Food import raises the dependence on foreign water resources because of indirect water consumption for importing countries in exchange for the increase of water use to produce food products for export in producing countries. This study aims to evaluate water supply and demand balances with food production and consumption in 2008 and 2018 to compare with each other. Water supply-demand ratio is defined as the ratio of irrigation water requirement to the amount of available water resource to evaluate the intensity between water demand and supply (water supply-demand intensities). Rice has the largest irrigation water requirement with food production, import and export in both years. Although food import and export have little impact on changing water supply-demand intensities, most Asian countries show larger water supply-demand ratio with food consumption than that with food production.

 This study carried out the hydrological analysis for an urban basin in the Tama hills considering infiltration capacity of various land use, targeting on the land use plan for “River Basin Disaster Resilience and Sustainability by All”. The hydrological model for mountainous basins developed by Fujimura is improved for this study. The results were obtained from the long-term runoff analysis for 22 years and flood runoff analysis for 10 events. The improved hydrological model approximately reproduced the flow duration curve for 22 years and 10 flood hydrographs, using the relative error and Nash-Sutcliffe coefficient. We showed the reliability of the improved hydrological model for urban basins based on the results of both long-term and short-term hydrological accuracy.

 Forests generally contribute to the water conservation function and soil erosion control in a watershed. Soil erosion in a dominantly forested catchment, in particular, is affected by various factors such as topography, geology, and vegetation composition, and such factors are intricately related to each other. The Bureau of Waterworks of the Tokyo Metropolitan Government manages the Ogouchi Dam watershed for more than 120 years and has measured various geophysical parameters in their maintained forests. In this study, the spatial distribution of forest characteristics that are generally influenced by sustainable management along the watershed was first mapped out and analyzed. Field measurements of some forest parameters like ground slope, tree height, breast height diameter, stand density, and forest floor coverage were conducted to verify the local conditions and an improved soil erosion equation was developed based on the new datasets obtained. The improved model was then applied to the entire watershed, and a soil erosion susceptibility map was created to visualize the areas with potentially higher risk for sediment-related disasters. The results showed that erosion susceptibility was less in forests managed by the Tokyo Metropolitan Government because of their canopy and surface properties that can reduce the raindrop impact.

 In this study, we developed hypsometric curves for 109 class-A river watersheds in Japan. We proposed a new model function to optimize the hypsometric curves. As a result, the coefficient of determination exceeded 0.85 in more than 80% of the watersheds in Japan, and the hypsometric curves were reproduced with high accuracy. Cluster classification was performed based on the parameters obtained by optimization, and consistency with cluster classification based on topographical information such as watershed area and length of trunk river channel was examined. As a result, the Yodo River and the Shonai River, and the Yahagi River and the Kuzuryu River were classified into the same cluster, indicating the possibility of extracting basin characteristics from the parameters of the new model function proposed in this study.

 Precipitation data are available at various spatial and temporal resolutions, it is not clarify to how differences of various precipitation data affect the results of hydrological and hydraulic simulations such as runoff analysis. In this study, we performed a fundamental study to contribute to the spatial evaluation of precipitation observation using JMA Radar-AMeDAS analyzed data in the Onga River basin.

 As a result, it was shown that different areal rainfall data characteristics are tend to occur by increaseing reduction rate of the precipitation data. Relative frequency distribution of the areal rainfall with over 40% reduction of precipitation data was shown that polarize for the areal rainfall with no reduction at all.

 This study shows snow and hydrological observations resulting from the experiment conducted at the Jozankei observation site in the upper catchment of Toyohira River. The dielectric sensor continuously measured the interior of snowpack. By combining hydrological and snowpack observations, the timing of the peak of the snow depth and the peak of the snow equivalent water volume were found to be clearly controlled by air temperature and solar radiation. The comparison of snow equivalent water content observed by the dielectric sensor and lysimeter shows that the characteristics of the difference between both sensors change during the snowfall, mid-snowfall, and snowmelt seasons. It can be reduced by applying a correction formula that is based on its observation principle. It was also shown that the dielectric sensor may be useful not only for estimating the amount of water equivalent, but also for estimating the snow charactristics of snowpack.

 This study aims to develop slope disaster prevention monitoring system with the participation of residents, using the IoT slope sensors to save human lives from slope disasters, which are becoming more frequent due to the effects of climate change. Trial monitoring was conducted in Fukuchiyama City, KyotoPrefecture, and analyzed in terms of residents' opinions, slope behavior, and evacuation switch settings. As a result, it was confirmed that the IoT slope sensor is expected to be useful as an evacuation switch for residents to escape from slope failures nearby and that it is beneficial in determining the risk level of slopes that behave sensitively by rainfall. Moreover, it is also found that setting an appropriate warning level as an evacuation switch is necessary by fully considering the slope behavior.

 The purpose of this study is to examine the method of analyzing producer behavior using the hypothetical behavior method by selecting the industry of the survey subjects. The target of the study was the travel industry, and questions were asked regarding the additional fees that could be added to the price of travel to reduce the risk of death from the novel coronavirus. The mean value of the amount of additional fees that would be acceptable ranged from 700 yen to 4,700 yen, and the median from 100 yen to 3,800 yen, for a 20% to 80% reduction in the risk of mortality. The results suggest that it is necessary to include company information in the hypothetical situation and to derive evaluation results with the influence of personal attributes set to zero.

 In an evacuation, it is important to properly identify risks and quickly secure personal safety by evacuating through the safest route. The purpose of this study was to verify the effectiveness of methods for evacuating inundated areas via the shortest possible route. Using the results of inundation simulations for 56 different rainfall patterns, evacuation methods were evaluated for each inundation pattern using network analysis. The evaluation results showed that methods for evacuating inundated areas via the shortest possible route was more effective for larger inundation areas patterns, and that there were locations in each pattern where the use of evacuation centers outside the city was effective. In addition, the locations where the effectiveness of methods for evacuating inundated areas via the shortest possible route was high were distributed throughout the city, and in particular, the locations where the frequency of inundation risk was high were highly effective. In the future, safe evacuation routes should be considered according to the inundation risk in district disaster prevention plans.

 This study compares the factors of heavy rainfall caused by Typhoon Hagibis (Typhoon No. 19) in 2019 to the Kanto Mountains with those of previous typhoons that had similar paths and those extracted from a huge ensemble of data (d4PDF). The mountain separates the upper reaches of the Tone River and Chikuma River. The results indicate that the heavy rainfall was caused by the southeastward inflow of large amounts of water vapor and by the collision of dry cold air from the north and moist warm air from the southeast over the Chikuma River basin, which collided with a wall of cold air moving southward and then turned around. Furthermore, this typhoon was found to be one of the largest typhoons in the future meteorological field. The methodology can be commonly applied to the analysis of heavy rainfall cases caused by typhoons in a certain basin.

 Capillary barriers are expected to be effective in reducing rainwater infiltration into the ground, and much experimental and theoretical knowledge has been obtained on how to evaluate their performance. On the other hand, fingered flows, which occur due to slight heterogeneity in infiltration from low to high permeable layers, have been experimentally confirmed, but quantitative evaluation methods have not been established. In this study, we attempted to quantitatively evaluate the effect of heterogeneity on impervious performance by 2-D simulations using a spatial distribution model of heterogeneous fields that can take into account the occurrence of fingered flow. The results showed that the impervious performance of heterogeneous fields is more sensitive to the permeability of the upper layer than that of homogeneous fields, and that the impervious performance of heterogeneous fields deteriorates in a long-term evaluation under actual rainfall conditions.

 This study presents effects of global warming and climate change on water quality in Lake Kasumigaura located in the southeastern part of Ibaraki Prefecture, Japan. Meteorological and water quality data between 2005 and 2022 (18 years) were analyzed to investigate variations of vertical mixing and oxygen distributions in the lake. Air temperature increased with a ratio of approximately 0.1 degrees per year in summer and the increase in air temperature was clearly correlated with water temperature in the lake. Stratification increases as air temperatures increases due to surface heat flux toward the lake, which weakens vertical mixing/transport leading to hypoxia in the bottom boundary layer. The combination of shear due to wind stress and surface heat fluxes due to solar radiation (shortwave radiation) explains stratification resulting in hypoxia. In order to investigate effects of increase in temperature due to climate change, we examined differences in water quality between the hottest(2018) and the coolest( 2007) summer in the data set. Stratification in 2018 was stronger than that in 2007. Dissolved oxygen (DO) in the bottom layer in 2018 was smaller than in 2007. In addition, a comparison of hot summers(6 years) and cool summers(6 years) showed the same trend appeared in the comparison of the hottest and coolest summers. These findings imply that the water quality in Lake Kasumigaura would likely modulated by the increase in temperature owing to global warming. Furthermore, there is concern that increase in temperatures associated with future global warming may alter the water quality in lake Kasumigaura.

 Increasing hydropower generation is one of the most important issues for contributing to carbon neutrality and climate change mitigation. On the other hand, hydropower producers have been required to reduce flood discharge due to recent extreme rainfall events. This study presents a method for detecting a rule curve that satisfies both increasing electricity generation and decreasing flood discharge in reservoir-type hydropower. Specifically, we applied a multi-objective optimization method to a water balance model for reservoir-type hydropower which can consider electricity generation and flood control. As a result of a case study, although we observed that the reservoir level could not always be adjusted according to the rule curves, we obtained the rule curves that reflected characteristics of objective functions in the optimization well.

 To investigate the characteristics and trends of water resources in the snow-covered regions of the Hoheikyo and Jozankei dams, we conducted an analysis using the inflow data of the hydrology and water quality database and the snow observation data at the upstream point of the Jozankei dam. Defining the snowmelt period from April 1 to June 30, we found that the total inflow volume into the dam lakes during the snowmelt period of the Hohei-kyo and Jozankei dams from 2003 to 2022 was generally synchronized, and that the total inflow volume during the snowmelt period for both dams decreased annually. The maximum snow water equivalent and snow depth at the Jozankei observation site occurred earlier, indicating an earlier melting period. Furthermore, based on the observations using the snow water equivalent, we investigated the relationship between the snowfall and snowmelt during the snow accumulation period in the Jozankei dam basin and the inflow volume during the snowmelt period into the dam lakes.

 The purpose of this study is to characterize the longitudinal water quality of the Chao Phraya River based on eight water quality observations: salinity, EC, TDS, DO, chlorophyll concentration, turbidity, pH, and water temperature over a seven-year period and water temperature over a seven-year period and to determine the actual condition of the water environment at the Samlae intake. The results showed that salinity, EC, TDS, temperature, and chlorophyll increased in the dry season and decreased in the rainy season. On the other hand, turbidity decreased during the dry season and increased during the rainy season. pH showed no clear seasonal variation. The water quality of the Sam Lae intake site was evaluated using salinity and DO, which are water quality standards set by the Thai government. The results showed that the salinity was strongly influenced by the accumulated precipitation and the short rainy season. The percentage of DO in class 3 (>4 mg/L) was on a decreasing trend, indicating that the water quality was deteriorating.

 Wood is expected to have climate change mitigation effects by replacing steel and cement and by storing carbon in buildings for long periods of time. This study quantitatively evaluates the role of wood substitution of steel and cement used in buildings in a scenario to achieve the 1.5°C target on a global scale. The results show that wood substitution has a GHG emission reduction effect of 0.45-4.0 GtCO₂eq/yr from 2020 to 2100, and reduces the GDP loss, which is a metric of climate change mitigation cost, by 0.2-0.9% in 2100 under the 1.5°C target scenario. The magnitude of these effects varied depending on the substitution rate. The feasibility of wood substitution would not be solely determined by economic rationality, but rather policy guidance could play a significant role. It is considered important to proceed with discussions on actual policy while comprehensively evaluating the advantages and disadvantages based on the results of this study.

 The agriculture and livestock sector accounts for 24% of anthropogenic greenhouse gases in the global warming problem. Therefore, we estimated the emissions of CH₄ and N₂O in the agriculture and livestock sectors in the Latin America region, which have not been studied before, the amount of possible emission reductions, and effective countermeasure technologies. As a result, it is estimated that the emissions of CH₄ and N₂O in the agriculture and livestock sectors in the Latin American region will be 633MtCO_₂eq/year in 2050, which is 528MtCO_₂eq/year (45.5%) lower than the case where no countermeasures are taken. The study covered 34 countries in the Latin American region, and the top three countries accounted for 71.1% of the reduction. The most effective reduction technology in 2050 was shown to be the change to highly productive livestock species, followed by the highly efficient use of fertilizers.

 It has been reported that the introduction of GHG reduction measures in the agriculture and livestock sectors will play an important role in mitigating greenhouse gas (GHG) emissions in Asia, but no evaluation of countermeasure technologies at the national level in all Asian regions has yet been conducted. Therefore, this study clarified the amount of methane and nitrous oxide that can be reduced by countermeasure technologies in the agriculture and livestock sectors of 36 Asian countries and the costs associated with the reduction and proposed specific cost-effective measures for reduction. As a result, it was found that GHG emissions can be reduced by about 1750 MtCO_2eq (about 49% of the emissions in the same year) by implementing GHG reduction measures in 2050 in Asia as a whole.

 There has been growing concern in recent years about the intensification and frequency of natural disasters due to climate change. The impact of natural disasters is significant on railways. Thus, it is an urgent issue to promote measures against flood damage based on the impact of climate change on transportation networks. This research aims to assess the current and future flood risk of railroads in Japan, by applying three evaluation indices "hazard," "exposure," and "vulnerability. According to the findings, the flood risk at the end of the twenty-first century will increase a little in the sustainable scenario and increase a lot in the fossil fuel-dependent scenario compared to the end of the twenty century.

 In this study a quantitative evaluation of changes in peak flood discharge and erosion potential under a future climate and effects of various adaptation measures on water level reduction and erosion control was conducted for rivers in Toyama Prefecture, Japan. In particular, this study examines the differences in flood and erosion risks and the potential for adaptation when the impact of global warming is limited to a 1.5°C increase instead of a 2°C increase based on mitigation efforts. The results show that the peak flood discharge of five rivers is reduced by an average of 1.21 times with a 2°C increase, but by 1.13 times with a 1.5°C increase. In addition, the proportion of sites with high risk of erosion potential could be limited to a 2% increase. Furthermore, it was found that adaptation measures were highly effective in the Oyabe River, and that a 1.5°C increase in water level and erosion potential could be controlled by implementing rice paddy dams in 30% of the total paddy field in the basin under the combination with river vegetation management. It was found that the percentage of the paddy field area in the basin area at the middle and upper region is the key for the effects of the paddy field dam. Also, the existance volume of the vegetation in rivers and the flood flow time on the flood plain are the key for the effects of the vegetation cutting and management.

 This study simulated energy systems that could achieve carbon neutrality in 2050 for Kushiro City, Hokkaido, Japan, using an energy system model which can take into account the use of synthetic fuels and regional characteristics. The results show that a scenario with no emission reduction targets could reduce CO₂ emissions by 61% from 2015 levels, and even a scenario without synthetic fuels could reduce emissions by 80% from 2015 levels through aggressive mitigation measures. Key mitigation measures in the mitigation scenario included the introduction of solar photovoltaics in the residential sector, the substitution to LP gas in the industrial sector, and the promotion of electrification in the transportation sector. The study also showed that carbon neutrality in 2050 could be achieved by using synthetic fuels to meet the energy demand that should be supplied by liquid and gaseous fuels, i.e., space heating in the cold region and industrial heat. Policies that encourage the cost reduction of synthetic fuels are key to decarbonizing cold regions and industrial clusters, where the demand for liquid and gaseous fuels may remain.

 Biomass, hydrogen, and CO₂ utilization technologies have recently attracted attention as CO₂ emissions reduction measures while previous climate change mitigation studies rarely evaluated these technologies. This study aims to develop the global energy system model which can explicitly consider chemical production technologies and to clarify the role of feedstock substitution technologies in chemical production process. As a result, electrolytic hydrogen utilization technologies were implemented only in ammonia production, and CO₂ utilization technologies were never introduced due to its high cost even under the assumption of limited availability of biomass and CCS that should give an advantage to CO₂ utilization. It is suggested that CO₂ emissions reduction from the use of fossil fuel feedstock strongly depends on the availability of biomass, which plays a central role in feedstock substitution.

 Climate change can cause economic losses and increase poverty. However, climate change mitigation measures can also cause economic losses and increase poverty. Previous studies have not assessed the impact of climate change and climate change mitigation on poverty simultaneously. This study aimed to quantitatively assess the impact of climate change and climate change mitigation on poverty worldwide. The results show that, while poverty impacts of climate change can be reduced in the scenario that achieves the 2°C target of the Paris Agreement, the impacts of climate change mitigation measures will be larger, and the number of poor people will be 26-42 million in the short term and 2-10 million in the long term, which is larger than in the scenario that does not achieve the 2°C target. This is based on a uniform global carbon price. This is due to the fact that climate change mitigation measures using carbon taxes based on a uniform global carbon price would cause significant economic losses in low-income countries. Climate change mitigation measures need to be discussed.

 Kyoto City has announced its goal of achieving net zero carbon dioxide emissions by 2050, ahead of all other cities in Japan. Previous studies have quantified the city's net-zero emissions of energy-related carbon dioxide. In this study, we developed a method for creating decarbonized society scenarios that also take into account the waste sector. Then we examined the feasibility of achieving net zero carbon dioxide emissions in 2050 for Kyoto City by applying the method. The results showed that the city can achieve net zero carbon emissions in 2050 by reducing energy-related emissions through the use of renewable energy, electricity and hydrogen derived from renewable energy, and by the introduction of BECCS at waste incineration plants, so that emissions from the waste sector turn negative and the city's emissions are lower than the amount of carbon dioxide absorbed.

 This study aims to grasp the potential flood damage reduction effect of riparian vegetation removal in Japan. We calculated changes in flood damage before and after riparian vegetation removal through the estimation of roughness coefficients of river channels using the normalized vegetation index obtained from satellite images and the calculation of damage based on flood inundation analysis. The damage reduction rate was estimated to be 1.3% whole of Japan when vegetation was removed in river channels where Strahler's stream order was four or higher. The class A river systems with the highest damage reduction rates were the Sekikawa River system (16.3%), Tokachi River system (14.7%), Oita River system (13.6%), Tenjin River system (11.7%), and Oyabe River system (10.9%). We also estimated the damage reduction rate depending on the section of riparian vegetation removal. The result shows that the flood damage reduction effect of vegetation removal in river channels with Strahler's stream order of five or higher is approximately 80% of the flood damage reduction effect of vegetation removal in river channels with Strahler's stream order of four or higher.

 The combined effects of increased river flow due to heavy rainfall, vegetation in the river channel, and driftwood have increased the damage caused by floods. However, the interaction of vegetation and driftwood during floods has not been studied. In this study, hydraulic model experiments were conducted to understand the behavior of driftwood in the presence of vegetation, and the relationship between the density of vegetation and the length of driftwood. The results showed that the rate of driftwood accumulation and the rate of water level rise during floods decreased as the length of driftwood became shorter and the density of vegetation became smaller.

 As an initial study to clarify the impact of flood disasters on population change, this study quantitatively analyzes the impact of flood damage on the rate of change in the social population in all municipalities in Japan in the case of recent flood damage. The variables selected to represent the scale of flood damage were the area inundated, the percentage of households inundated under the floor, inundated above the floor, and the percentage of households totally destroyed or lost in each municipality. The results of both multiple regression and DID analyses showed that the rate of households inundated under the floor, the rate of households inundated above the floor, and the rate of households totally destroyed and lost had a negative impact on the rate of change in the social population (p < 0.05). Floods have a negative impact on social population change at the municipal level in recent flood disasters in Japan, i.e., they reduce the social population.

 In recent years, there has been an increase in the frequency of heavy rainfall disasters, leading to floods. However, there is a lack of established methods for considering disaster responses, including evacuation, at the regional and watershed levels while accounting for the impacts of climate change. The objective of this study was to develop a method for evaluating the issuance of evacuation information in municipalities, specifically in response to heavy rainfall events that may occur during climate change progression. We proposed a method for generating flood scenarios at the regional level based on climate projections provided to a municipality, and using these scenarios to issue evacuation information. As a result of applying this exercise method in Obihiro City, Hokkaido, the municipality consider the specific timing and areas for issuing evacuation information in response to unprecedented-scale flood scenarios predicted by the climate projection database. This approach facilitated discussions on appropriate responses, such as the issuance of evacuation information, for similar heavy rain and flood events.

 Two representative heavy rainfall disasters in Hokkaido occurred during the approach and passage of Typhoon Lionrock (2016) and Typhoon Phyllis (1981). In this study, the analysis of reanalysis datasets indicates that both typhoon cases originated in the low-pressure area of the low-latitudes, moved northward across the Pacific Ocean due to the northeastward shift of the Pacific High, approached Hokkaido, and then moved toward the cut-off low that existed to the west of Hokkaido. In both cases, rainfall was concentrated along the mountain. However, in the case of Typhoon Phyllis (1981), a front existed around Hokkaido so that heavy rainfall also occurred along the front. In the past, there have been cases of not only small rainfall but also heavy rainfall in meteorological fields where both typhoons and fronts existed. Furthermore, it was found that there were no other typhoon cases with the same combination of reanalysis datasets as the two cases after 1958.