Science Council of Japan proposes effectively linking risk assessment with preventive investment to strengthen disaster resilience in megacities

There are 42 megacities, i.e., urban areas with populations exceeding 10 million, in the world. Tokyo, (30 million people), Osaka (approximately 15 million people), and candidate megacity Nagoya, (9.5 million people), all have coastal areas and a high concentration of people and assets. As large-scale disasters such as an earthquake directly beneath the capital or a Nankai Trough earthquake are anticipated, how must we prepare?

The Science Council of Japan has released a proposal titled "Science, Technology, and Innovation to Strengthen Disaster Resilience in Megacities Facing Catastrophic Disaster Risks." Chair Kaoru Takara of the IRDR Subcommittee of the Committee on Civil Engineering and Architecture (President of the National Research Institute for Earth Science and Disaster Resilience), said, "How can we overcome urban vulnerability and effectively respond to large-scale disasters? As researchers, we have proposed items that should be practiced immediately, items that the national and local governments should carry out, and items that residents and private companies should tackle as self-help, public assistance, and mutual aid. We will also disseminate this internationally."

In the damage estimation for a Nankai Trough earthquake, assuming a maximum-class earthquake and tsunami, the number of deaths nationwide is 298,000. The breakdown is as follows: 215,000 people die from the tsunami, 73,000 from collapsed buildings, and 9,000 from earthquake fires, and an estimated 52,000 other disaster-related deaths.

A large-scale disaster in a megacity could result in a critical situation for the whole of Japan. The vulnerability of megacities is closely related to social and economic factors. Urban vulnerable populations often live in unstable living environments and in buildings with low earthquake resistance and are at risk of suffering tremendous damage in the event of a disaster. In addition, urban-specific problems such as traffic congestion and underdeveloped evacuation routes make prompt evacuation and rescue operations difficult in the event of a disaster.

Furthermore, the aging of urban infrastructure such as roads, water and sewage systems, and bridges, as well as the instability of the energy supply, contribute to confusion when a disaster occurs. Revolutionary and explosive changes in the means of information collection and transmission in recent years are also forcing fundamental transformations in how disaster information is disseminated and distributed. Although the government, local municipalities, and residents are aware of these situations, preventive investments are being postponed for disasters that could happen at any time because the damage-deterrence effect of such investments has not been quantitatively understood.

This proposal was created with the aim of strengthening the disaster resilience of the world's megacities, where catastrophic disasters are expected to have a significant global impact. In addition to conventional infrastructure-centered disaster measures, the proposal suggests a comprehensive approach that has become increasingly important in recent years, including: risk-considered urban planning and development; medical care, welfare and public health during disasters; quantification of disaster risks and investment effects; utilization of disaster information; strengthening of international cooperation; and the use of science and technology.

For example, it states that standardization of risk assessment, which is an important factor in judging the validity and priority of public and private project investments in areas with disaster risks, is necessary. It is desirable to promote international standardization such as ISO and various standards for disaster risk assessment through cooperation with various countries and international organizations, and collaboration between industry, government, and academia, utilizing Japan's science and technology.

In megacities, disaster assessments that also consider the impact on central functions are essential. By sharing data that ensures a certain level of quality, including not only hazards but also exposure and vulnerability, and standardizing that data, it is possible to effectively link risk assessment with disaster prevention investment.

Furthermore, as a problem unique to megacities, the proposal points out that while the Tokyo area, for example, is a coalition of multiple administrative organizations such as Chiba, Saitama, and Kanagawa Prefectures in addition to Tokyo Prefecture, it lacks a function to supervise them.

Currently, under the Basic Act on Disaster Management, municipal governments are responsible for pre- and post-disaster responses, while under the Disaster Relief Act, prefectural and national governments handle post-disaster measures.

If administrative organizations respond individually and separately based on these laws, pre-disaster measures will be insufficient, and emergency responses at the time of a disaster, as well as subsequent recovery and reconstruction, will be carried out in a disorderly manner. Therefore, it is necessary to consider how to tackle catastrophic disasters as a whole megacity. The proposal suggests that a Disaster Basic Law at a higher level than currently set may be necessary.

Takara commented, "In pre-disaster prevention so far, infrastructure development has been the center, but it is necessary to increase investment in soft aspects such as human resource development and the construction of digital twins utilizing SNS. Also, by utilizing AI, it becomes possible to aggregate necessary data from a vast amount of information to support judgment and to advance disaster relief robots. It is also important for many stakeholders to build networks on a daily basis and promote information exchange and preliminary drills."