The Committee on Disaster Mitigation under Global Changes of Natural and Social Environments, Science Council of Japan (SCJ), issued on May 30, 2007 a report, “Policies for Creation of a Safe and Secure Society against Increasing Natural Disasters around the World”.
The report, which includes an outline of Japan’s past responses to natural disasters of a global scale, provides a comprehensive discussion of a desirable direction for the development of infrastructure and social systems to meet the forthcoming changes in nature and society. Based on the report, the committee reported to the Minister of Land, Infrastructure and Transport, in response to the minister’s former inquiry.
Another report was issued on countermeasures by adaptation to water-related disasters, following the former report and the result of discussions made in the subcommittee on June 26, 2008.
This special issue of JDR is based on the latter report of Science Council of Japan.
In Japan, over the past 30 years, the number of days of heavy rain with a daily rainfall of 200 mm or more have increased to about 1.5 times that of the first 30 years of the 20th century.
It has been pointed out that this is likely to have been caused by global warming. The Fourth report of the IPCC indicates that even low-end predictions implies an unavoidable temperature rise of about 2°C, and, even if the concentration of greenhouse gases is stabilized, the ongoing warming and sea level rise will continue for several centuries.
In terms of social systems, population and assets are increasingly concentrated in metropolitan areas. At the same time, economic recession and aging of the population are accelerating especially in rural areas.
The central parts of small- and medium-size cities have lost vitality, and so-called marginal settlements are increasing in farming, forestry and fishing villages.
These factors make it difficult and complicated to maintain social functions to fight with natural disasters.
Under these circumstances, it is quite important in our country to take an action for adaptation to climate changes, where land is vulnerable to water-related disasters. The need for adaptation has widely been recognized in Europe, and various reports have been issued there. In Japan, initiatives to reduce greenhouse gases emission are being actively discussed, but both the central government and the people still do not fully recognize the importance of adaptation to water-related disasters.
Elsewhere, increases in extreme weather and climate events have caused flood disasters, such as those that have been occurring with larger frequency in the downstream deltas of Asian rivers. The latter type of disaster is exemplified by the unprecedented huge flood disaster that occurred in Myanmar in May in the last year. The increase of population in Asia will induce shortage of water resources in near future. Japan, which is in the Asian Monsoon Region, has a natural and social geography similar to these countries. Japan should implement strong assistance programs based on accumulated knowledge and advanced technologies developed.
To treat the adaptations mentioned in the above, there are many components to be considered such as follows:
(1) Reliable assessment of future climate, economic and social situation such as population.
(2) Developing physical and social infrastructures.
(3) Building disaster awareness and preparation in communities.
(4) Planning for recovery and restoration.
(5) Research and development for adaptation.
(6) International contributions for preventing water-related disasters.
In this special issue of JDR, these subjects are treated in series by introducing 5 papers written by leading researchers and engineer worked in the central government. However, the details of international contributions could not be included in this issue.
Special issue, “Kurile arc subduction zone: View of great earthquake generation and disaster mitigation of related phenomena”