In developing countries in Asia and Africa, where flood risk information is insufficiently obtainable, companies often use available flood hazard maps developed from the Global Flood Model (GFM). As described, this study compares existing flood hazard maps based on GFM used in business practice. Then the factors causeing differences in inundation areas and depths are analyzed, particularly addressing the model structure and input data. Results indicate that inundation patterns in low-lying areas are affected by the accuracy of elevation data and that the methods of reflecting flood protection information differs greatly among GFMs. The results also suggest that the consideration of backwater effects in river sections near large lakes and the consideration of channel bifurcation in delta areas are necessary to obtain realistic inundation distributions. Based on these findings, we propose a flow of selecting a flood hazard map to be used in corporate practice. Although no single map can be recommended for all purposes, the benefits and shortcomings of each map can be listed for objective prioritizeation of maps that should be used. The outcome of this study can be extended to the use of other risk maps including paid products, and might provide fundamental scientific information for use in the implementation of appropriate and accountable flood risk assessments.

　To elucidate the characteristics of groundwater near the coastal area in Sendai and the variation in its quality, water samples were collected every month since December 2018. Water quality assessment of the open-channel flow (hereafter referred to as the channel) indicated the presence of Na-Cl with extremely high electrical conductivity. Shallow groundwater contained (Na+Ca)-HCO₃, while deep groundwater contained Na-(Cl+HCO₃) or Na-HCO₃. The water quality of the channel and shallow groundwater exhibited seasonal variations owing to precipitation. The quality of deep groundwater was almost constant with no seasonal variation; however, S-3, which is a deep well located near the seashore, differed slightly from other deep groundwaters in that the Na⁺ and Cl^- concentrations in this well were higher than those at other sites, perhaps owing to the effect of sea salt. The δ¹⁸O and δ²H values were relatively low in S-3; therefore, its recharge elevation was likely higher than that of other sites owing to the effect of altitude. Additionally, the residence time of deep groundwater estimated using CFCs was approximately 70 years.

　The international community has agreed through the Paris Agreement to limit the global temperature rise to less than 2 °C above the pre-industrial level. In recent years, many targets with carbon-neutrality as the keyword have been announced. The realization of carbon-neutrality is much more ambitious than the Kyoto Protocol-based climate change countermeasures, and will necessitate major shifts in social structure. Nevertheless, even economic organizations organized by corporations have been announcing that they will cooperate with carbon-neutral goals rather than oppose them. This study investigates the past trends by particularly addressing on the progress of climate science, the economic policies of various countries, the efforts of corporations and investors, and the activities of NGOs, etc. Furthermore, this study clarifies the background to elucidate why the world is moving toward carbon-neutrality from a broad perspective. The literature review confirmed that climate science progress has influenced the international agreement, and that development of new countermeasures such as TCFD, which requests private enterprises to open their climate risk information, has encouraged the carbon-neutral movement. In the private sector, climate risk reduction and economic benefits are linked through TCFD, suggesting a paradigm shift in the awareness of the parties involved that climate change measures are “no longer a social contribution but are necessary for their own survival”. Along with the supports of these changes in social conditions, the international community is thought to have moved toward carbon-neutrality.