An Efficient Method for Mapping High-Resolution Global River Discharge Based on the Algorithms of Drainage Network Extraction

Inundation Analysis of the Oda River Basin in Japan during the Flood Event of 6–7 July 2018 Utilizing Local and Global Hydrographic Data

During the first week of July 2018, widespread flooding caused extensive damage across several river basins in western Japan. Among the affected basins were the Mabicho district of Kurashiki city in the lower part of the Oda river basin of the Okayama prefecture. An analysis of such a historical flood event can provide useful input for proper water resources management. Therefore, to improve our understanding of the flood inundation profile over the Oda river basin during the period of intense rainfall from 5–8 July 2018, the Rainfall-Runoff-Inundation (RRI) model was used, with radar rainfall data from the Japan Meteorological Agency (JMA) as the input. River geometries—width, depth, and embankments—of the Oda river were generated and applied in the simulation. Our results show that the Mabicho district flooding was due to a backwater effect and bursting embankments along the Oda River. The model setup was then redesigned, taking into account these factors. The simulated maximum flood-affected areas were then compared with data from the Japanese Geospatial Information Authority (GSI), which showed that the maximum flood inundation areas estimated by the RRI model and the GSI flood-affected area matched closely. River geometries were extracted from a high-resolution digital elevation model (DEM), combined with coarser resolution DEM data (global data), and then utilized to perform a hydrological simulation of the Oda river basin under the scenarios of backwater effect and embankment failure. While this approach produced a successful outcome in this study, this is a case study for a single river basin in Japan. However, the fact that these results yielded valid information on the extent of flood inundation over the flood-affected area suggests that such an approach could be applicable to any river basin.

The Role of Large Dams in Promoting Economic Development under the Pressure of Population Growth

The close relationship between large dams and social development (i.e., water, food, and energy consumption) has been revealed in previous studies, and the vital role of large dams in sustaining societies has been recognized. With population projections indicating continued growth during this century, it is expected that further economic development of society, e.g., Gross Domestic Product (GDP) growth, will be greatly affected by possible challenges, such as water, food, and energy shortages in the future, especially if proper planning, development, and management strategies are not adopted. In our previous study, we have argued that construction of additional large dams will be considered as one of the best available options to meet future increases in water, food, and energy demands, which are all crucial to sustain economic development. In the present study, firstly, we will emphasize the vital role of dams in promoting economic growth through analyzing the relationship between large dam development and GDP growth at both global and national scales. Secondly, based on the projection results of future large dam development, we will preliminarily predict the future economic development represented by GDP. The results show that the impacts of large dams upon GDP are more significant in countries with higher levels of socioeconomic development, which generally supports large dams as the vital factor to promote economic development.