Interview with Yasuhiko Hamada, Director of the Takahashi River and Oda River Emergency Flood Control Project Office
We spoke with Yasuhiko Hamada, Director of the Takahashi River and Oda River Emergency Flood Control Project Office of the Chugoku Regional Development Bureau, about the status of the construction work and other matters.
About the Takahashi River and Oda River Emergency Flood Control Project Office
Please tell us about the Takahashi River and Oda River Emergency Flood Control Project Office.
Hamada (honorifics omitted)
Our office did not originally exist.
Following the damage caused by the July 2018 Heavy Rain, a “Disaster Recovery Measures Field Office” was first established at the Takahashi River Field Office of the Okayama River Office to oversee disaster recovery sites.
The initial response involved drainage work, removing sediment, and tree clearing, as well as emergency measures to first fill in the breached embankments and build temporary embankments.
After that, to carry out permanent repairs to the embankments and the intensive disaster recovery project, we set up an office at the Mabi Branch Office of Kurashiki City in April 2019 and began operating as a new organization.
The term “intensive disaster recovery project” is not one we hear very often, and it gives the impression of something “major.” What exactly does it involve?
Hamada
There are many national projects, and this is one of them. When damage is severe, emergency measures to prevent a recurrence of disasters are implemented based on a set plan. This is called an “intensive disaster recovery project,” and it is generally expected to be completed in about five years.
Around 4,600 buildings in Mabi were damaged in the July 2018 Heavy Rain. Because the damage was extensive and urgent action was needed, the project was adopted and implemented by the national and prefectural governments as an “intensive disaster recovery project.”
Did the river-related construction work mainly begin with repairing the breached embankments?
Hamada
That’s right.
Two sections of the embankment had been breached. After investigating the cause, we first built up the soil around the clock, completing temporary embankments on July 21, 2018.
Since it might rain again, we cleared trees along the river to improve the flow as much as possible and reduce the load on the temporary embankments.
After the flood season ended, we removed the temporary embankments and rebuilt them.
They had only been temporary, and the soil had not been properly compacted.
Then, in September after the disaster, we drew up and began implementing a plan to complete both structural measures, such as the Oda River Confluence Relocation project, and non-structural measures in about five years. That work continues today.
Structural measures are easy to understand as projects of the Ministry of Land, Infrastructure, Transport and Tourism. I was a little surprised that you are also putting effort into “non-structural measures,” which I imagine includes responding to this interview.
Hamada
We are currently improving structural measures, such as embankments, but in the end, we cannot say that this makes things “safe.”
That is frustrating for us, because the rainfall during the July 2018 Heavy Rain was not the maximum possible.
We are working to ensure that rainfall on the scale of the July 2018 Heavy Rain can be safely carried away, but if even heavier rain were to fall, the river might overflow again.
In that sense, we need to do more than just structural work; we also need activities that encourage people to be prepared to evacuate. That is why we are working hard to promote the “My Timeline” program, one of our non-structural measures.
The residents of Mabi are looking ahead and thinking about how to recover and rebuild. In that process, people in every district say, “We have to evacuate, don’t we?”
- So, how do we evacuate?
- When do we evacuate?
We provide support on questions like these, and as an office of the Ministry of Land, Infrastructure, Transport and Tourism, we may be taking a more hands-on approach than usual.
Please tell us about the office.
Hamada
As of February 2022, there are 24 staff members at the office.
Our work first includes structural measures.
We issue construction contracts, supervise work sites, and handle design work carried out by our technical staff. We also coordinate with local residents in response to their requests.
The rest of the staff are administrative employees.
Their main work is general administration, but what sets us apart from other offices is that we have “Nige Kid,” a tool for creating a “My Timeline,” and we also give outreach lectures about it.
This is not limited to Mabi; we provide instruction whenever we receive a request from anywhere in Kurashiki City. It is something our staff would rarely get to experience at other offices.
So, just let us know and we’ll come by.
About the “Oda River Confluence Relocation”
I imagine the main structural measure is the “Oda River Confluence Relocation.” Could you tell us what makes it distinctive?
Hamada
The confluence with the Takahashi River is being moved about 4.6 kilometers downstream. The biggest benefit is that it makes the so-called “backwater effect” less likely to occur.
The Oda River flows east to west, so its gradient is gentler than that of the Takahashi River, which flows north to south. As a result, it is more susceptible to the Takahashi River’s influence, making the “backwater effect” more likely.
Relocating the confluence makes it possible to steepen the gradient, making backwater less likely.
It is a huge project, but I have heard that it was not planned in response to the July 2018 Heavy Rain.
Hamada
That’s right.
In fact, it was launched in 2014 as a “large-scale general improvement project.” We conducted on-site surveys, environmental impact assessments, and buried cultural property surveys, and were about to begin temporary construction in fiscal 2018.
Then the July 2018 Heavy Rain occurred.
Because work had begun in 2014, construction could start right away. Without that, we might only just be getting started now (in 2022).
The work, originally planned to take 10 years, is being completed in five. I think a major reason this was possible is that the design was already complete (meaning the work had already been decided).
Photo courtesy of the Takahashi River and Oda River Emergency Flood Control Project Office
I got the impression that the survey of buried cultural properties at Minamiyama became a topic of discussion after construction began. It had already been underway, right?
Hamada
It had already been underway since 2017.
Excavation surveys take time, but they need to be completed before a project begins, so we had started the work.
In Kurashiki, the East Takahashi River was abandoned about 100 years ago and the river was consolidated into one channel, and the Takahashi River East-West Water Intake and Distribution Facilities were built. I hear that was also a major undertaking of its time. Is this kind of construction unusual?
Hamada
There are projects that create shortcuts, but I think relocating a confluence is unusual nationwide.
The project has faced challenges in handling “soil”
This is an unusual and large-scale project that was originally scheduled to take 10 years but is now being completed in five. Has that created any challenges?
Hamada
There are various challenges, but when it comes to the construction work, handling the “soil” has been difficult.
We are cutting into Minamiyama and excavating the river, which produces an enormous amount of soil. The question is what to do with it.
It would be easy if we could use the excavated soil directly for the embankments, but the soil from the Oda River is clayey and difficult to use on its own, so we mix it with the sandy soil from the Takahashi River.
That means we need to coordinate the work with the Takahashi River side.
We also need to gather the soil somewhere in order to mix it. With more time, we could consider things at a leisurely pace, but we are expected to efficiently “excavate, mix, and build up” the soil, which makes this challenging.
At first, there is plenty of land and many places to store the soil, but as construction progresses and the area is developed, storage space decreases.
We could take it farther away, but that would take time and money, as well as requiring a suitable location.
The work site is expected to operate as efficiently as possible nearby, so it has been challenging.
Could you tell us about the progress of the construction as of February 2022?
Hamada
The project is 52% complete and is progressing as planned.
There are two years left until the scheduled completion. We can gradually see what it will look like when finished.
Strengthening the Takahashi River embankment is being carried out as part of the “Three-Year Emergency Measures for Disaster Prevention and Mitigation and National Resilience”
The work on the Oda River is progressing smoothly. By the way, I believe embankment reinforcement work is also being carried out on the Takahashi River. Is it being done in parallel?
Hamada
As I mentioned earlier, the work is related because we use the soil, but in terms of the projects, they are separate.
The work on the Takahashi River is being carried out by the Okayama River Office as part of the “Three-Year Emergency Measures for Disaster Prevention and Mitigation and National Resilience”. It is a separate project, but it is not entirely unrelated; this work is also necessary for flood control.
The July 2018 Heavy Rain and Typhoon Hagibis in 2019 are examples of the increasing number of disasters nationwide.
The thinking is that “we need to make sure flood control is done properly,” so funding has been secured and the work is underway.
There is no such thing as absolute safety, so please remember to “get to safety first”
Finally, could you share a message for the people of Mabi and Kurashiki City?
Hamada
The national, prefectural, and city governments have all been carrying out improvements for a long time, so the level of flood safety is gradually increasing.
This is my personal view, but I would like to reach a point where “rivers flowing normally” is simply taken for granted.
I had hoped that instead of saying, “The rain was scary,” it would become natural to say, “It rained a lot.” But things are no longer that simple.
So, I hope people will remember to “get to safety first”.
Local residents often tell us, “You’ve done so much construction, so it’s safe now, right?”
But, as I’ve said, we cannot say it is “absolutely safe,” so we tell them, “It will be safer than it was in 2018”.
Even after this project is completed, the danger will not be eliminated. Please remember that you are responsible for protecting yourself.
Also, even those currently living in Kurashiki do not know where they may end up in the future for school, work, or a transfer.
If you create a “My Timeline” and learn about it once, I think you will become more aware of the need to stay alert wherever you go.
And even if you are well today, you do not know what next year will bring. Wouldn’t it be important for everyone to review their plans together?
I would be glad if more people developed that kind of awareness.
- Download the “My Timeline Creation Support Tool: Nige Kid”
- Nige Kid User Guide (YouTube)
From the Writer
I have lived for 42 years, about 30 of them in Kurashiki, but until the July 2018 torrential rains, I thought disasters were something that happened somewhere far away.
Since then, I have checked hazard maps and evacuation shelters and prepared emergency supplies, getting ready to evacuate in an emergency. But I cannot deny that my awareness has faded over time.
I think part of the reason was that I had the thought, “They’re carrying out such a large-scale construction project, so once it’s finished, we’ll be safe.”
However, what left an impression on me was that, even during the interview, they repeatedly said, “We can’t say it’s absolutely safe. We want you to evacuate when it’s dangerous, and to always be prepared to do so.”
Construction is still underway, with completion planned for March 2024 (the end of fiscal year 2023), and the area will be safer than before once it is finished.
However, I realized that it is necessary to always be aware of the risks of living there.
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