Urban Flood Runoff Modeling in Japan: Recent Developments and Future Prospects

Abstract

Since the 20th century, Japan has experienced a period of very rapid urbanization. Cities have experienced substantial densification and expansion, resulting in gradually elevated flood risk. Urban flooding has also occurred in most large cities in Japan, particularly in Tokyo. In response to this growing problem, much effort and resources have been spent on research and development aimed at understanding, simulating, and managing urban flood risk in Japan. The objective of this review is to summarize, discuss, and share key outputs from some of the main research directions in this field, significant parts of which have been uniquely developed in Japan and only published in Japanese. After a general introduction to urban runoff modeling, in the next section, key historical works in Japan are summarized, followed by a description of the situation in Japan with respect to observations of precipitation and water level. Then, the storage function model approach is reviewed, including an extension to urban basins, as well as recent experiments with AI-based emulation in Japanese basins. Subsequently, we review the prospects of detailed hydrodynamic modeling involving high-resolution, vector-based Geographical Information System (GIS) data for the optimal description of the urban environment with applications in Tokyo. We conclude the paper with some future prospects related to urban flood risk modeling and assessment in Japan.

Urban Water-Related Problems

“…The review paper "Urban Flood Runoff Modeling in Japan: Recent Developments and Future Prospects" [1] summarizes, discusses, and shares key outputs from some of the main research directions in urban flood runoff modeling, significant parts of which have been uniquely developed in Japan and only published in Japanese. In the paper, after a general introduction to urban runoff modeling, the authors present key historical works in Japan, followed by a description of the situation in Japan with respect to observations of precipitation and water level.…”

“…This Special Issue comprises four review papers and nine research articles, with contributions from 55 authors of six countries. All four of the review papers are related to the problems associated with flash flood phenomena, among the many broad topics mentioned above, but they focus on very different aspects of the phenomena, such as urban runoff modeling in Japan [1], real-time urban flood forecasting systems for Southeast Asia [2], frequency analysis of urban floods [3], and the reduction of non-point pollution as well as flood runoff by porous concrete infiltration [4].…”