2018 July: Hiroshima Was Overwhelmed by the “Unexpected”

271 dead or missing, 6,758 houses completely destroyed—these figures from the July 2018 Western Japan floods still weigh heavily. In Hiroshima Prefecture alone, there were 114 fatalities. Landslides swept through residential areas, rivers overflowed, and water flowed into underground spaces. On that day, many people uttered, “I never thought it would come to this.”

Seven years later, Hiroshima has initiated various systems to prepare for the “next heavy rain,” including joint flood training in underground parking lots, the development of an app that delivers disaster information in real-time, and disaster education in elementary schools. Individually, these initiatives may seem modest. However, when viewed together, a common question arises—”Who was left behind back then?” Each of these efforts aims to address that question through their respective frameworks.

—

Joint Flood Training in Underground Parking Lots—Visualizing “Places from Which One Cannot Escape”

In October 2023, the first joint disaster training was conducted at the Kamiyacho underground parking lot in Hiroshima City. Organized by Hiroshima City, approximately ten related organizations participated, including the Chugoku Regional Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism, JAF Hiroshima Branch, and the management of the underground shopping area.

The impetus for this training was the flooding incident that occurred in June 2023 at an underground parking lot in Tsu City, Mie Prefecture. Heavy rainfall caused water to flow into the underground area, submerging 274 vehicles. The reported damage amounted to several hundred million yen. The Kamiyacho underground parking lot is a large facility in the center of Hiroshima, accommodating around 500 vehicles, making the assumption that a similar incident could happen there not unrealistic.

During the training, procedures for evacuation guidance in the event of flooding, the installation of flood barriers, and methods for escaping submerged vehicles were confirmed. A JAF representative demonstrated that once the water depth exceeds 30 centimeters, doors become impossible to open, and emphasized the need to be aware of the location of specialized hammers for breaking windows.

Notably, this training was conducted not by a single facility manager but as a “joint” effort involving multiple organizations. Flooding in underground parking lots is an issue that spans various jurisdictions, including surface drainage capacity, structural connections to underground shopping areas, information dissemination to users, and rescue systems. It cannot be addressed by one organization alone. By having related organizations stand in the same location and envision the same water level while confirming procedures, the establishment of such a “collaborative” space itself is one of the systems that did not exist seven years ago.

Of course, there is a gap between training and actual disasters. The Kamiyacho underground parking lot sees about 1,000 vehicles per day, most of which are driven by the general public who did not participate in the training. The next challenge will be how to convey the insights gained from the training to the everyday users of the parking lot—through the placement of informational materials, announcements upon entry, and video guides via QR codes, designing a system to “leave information available” will be essential.

—

Instant Sharing of Disaster Information Apps—Delivering “Information That Did Not Reach” Through Systems

Since the fiscal year 2019, Hiroshima Prefecture has been gradually advancing the digitalization of disaster information. In addition to the prefectural disaster web portal, the “Hiroshima Prefecture Disaster” app was enhanced in 2022 to include a system for delivering push notifications about landslide warning information, river water levels, and evacuation orders.

The background of this initiative lies in the bitter lesson learned in 2018. During the Western Japan floods, evacuation advisories and orders were issued late at night in Hiroshima Prefecture. However, residents who were not watching TV or listening to the radio, or who could not hear the disaster radio broadcasts, did not receive real-time information. According to a Cabinet Office survey, only about 4.6% of residents in the affected areas took evacuation actions during the Western Japan floods. The information was available, but it did not reach them.

The app is a system designed to fill that gap of “information that did not reach.” It automatically notifies users of warning information based on their location. The design allows users to intuitively understand “how dangerous the area they are currently in is” through an overlay display of hazard maps.

However, there is a structural challenge here. According to the Ministry of Internal Affairs and Communications’ 2024 survey on communication usage trends, the smartphone ownership rate among those aged 70 and over is about 65%. Even among those who own smartphones, the number of individuals who can install apps and set notifications independently is even more limited. This means that the tool may become the least accessible for the demographic that takes the longest to evacuate.

Some municipalities in Hiroshima Prefecture have begun addressing this challenge through a “dual approach of digital and analog.” Community welfare commissioners and voluntary disaster prevention organizations convey app information via phone calls or home visits—essentially creating a system where “people become the output devices for the app.” In Fuchu Town, Aki District, they are trialing a system where the app’s warning levels are incorporated into the communication network of voluntary disaster prevention organizations, initiating outreach to elderly households at level 3.

The app itself is merely a tool. It is only when one considers “who delivers it, to whom, and at what stage” that it can be truly called a system. How to design the connection point between technology and people—this encapsulates seven years of trial and error.

—

Disaster Education in Kumano Town—What to Pass On to the “Generation Without Memory”

Kumano Town in Aki District, Hiroshima Prefecture. In the 2018 Western Japan floods, 12 people lost their lives due to landslides in this town. For a small town with a population of about 23,000, the weight of that number is immeasurable.

At Kumano Town’s Fourth Elementary School, disaster education based on the lessons learned from the Western Japan floods is conducted every year. In the 2024 school year, fifth graders conducted fieldwork using the local hazard map to investigate potential danger spots along their route from home to school. The students identified and mapped locations such as clogged ditches near cliffs and intersections that had previously flooded.

One student’s words were particularly striking: “I heard that the mountain behind my grandmother’s house collapsed, but now it looks nice, and I couldn’t tell where it had collapsed.” In the landscape where recovery has progressed, traces of the disaster become less visible. In 2018, the current fifth graders were only three or four years old. How to convey “what happened back then” to a generation without memory is both an educational issue and a question of how to preserve the community’s memory.

In Kumano Town, in addition to school disaster education, disaster courses involving local residents and parents are held two to three times a year. In the 2024 school year, workshops using the evacuation shelter management game (HUG) and storytelling activities by residents with disaster experience were conducted. By having the school and community learn together on the same theme, a pathway is created for “children to bring back knowledge to their families.” This ensures that disaster education does not remain confined to the classroom but connects to family conversations—this design reflects Kumano Town’s seven years of accumulation.

—

Common Threads in the Three Initiatives

The training in underground parking lots visualized “places from which one cannot escape.” The disaster app aims to deliver “information that did not reach.” Disaster education in Kumano seeks to pass experiences to the “generation without memory.”

Each angle is different. However, what unites all three is that they start from the perspective of “those who were left behind in 2018.” Those who were underground and delayed in escaping, those who did not receive information, and those who were too young to understand what happened—each of these “ways of being left behind” is being addressed not through individual efforts but through systems.

What has changed in the last seven years? Simply put, the subject of “preparedness” has changed. In the past, the emphasis was repeatedly placed on self-help, with the mantra of “protecting oneself.” While that is still true, the fact that lives could not be saved through self-help alone has led to a movement to design systems that ensure “no one is left behind”—connecting mutual assistance and public assistance.

Of course, challenges remain. How to reach the vast majority of users who do not participate in training. To what extent can the dual approach for those who cannot use the app be maintained? How to distribute the burden on teachers responsible for disaster education? Systems begin to degrade the moment they are created. Maintaining and continuously updating them becomes the next challenge.

Even so—what Hiroshima experienced seven years ago as “unexpected” is gradually being rewritten as “expected.” Flood barriers are placed in underground parking lots, warning information reaches smartphones, and elementary school students walk to school with hazard maps in hand. Each of these steps is small. However, that is what systems are fundamentally about. They may lack flashiness, but they can make someone’s decision a few minutes earlier on the night of the next heavy rain. Those few minutes can be the difference between life and death.