Four years have passed since the July 2018 torrential rains as of 2022.
A major project to relocate the confluence of the Oda River and Takahashi River from present-day Mabi to Funao, about 4.6 kilometers downstream, is progressing at a rapid pace, with completion targeted for the end of fiscal 2023.
The project is expected to reduce the effects of backwater from the Takahashi River during floods, lower the water level of the Oda River, and improve safety.
A site briefing was held on November 12, 2022, and here we report on how it went.
The information presented was accurate at the time this article was published in November 2022. Please note that it may differ from current information.
What is the Oda River Confluence Relocation Project?
The site briefing was held as part of a citizens’ lecture series. Staff from the Takahashi River and Oda River Emergency Flood Control Measures Office, Chugoku Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism, which is responsible for the project, provided the explanations.
The project was originally underway with completion targeted for fiscal 2028.
However, following the July 2018 torrential rains, the urgency of the project was reassessed, and under the “Special Emergency River Disaster Prevention Project,” the construction period has been shortened, with completion now scheduled by fiscal 2023.
The current confluence of the Oda River and Takahashi River
First, take a look at the upper right of the photo above.
▼ The water on the right is the Takahashi River, flowing from the far side toward the foreground. The Oda River joins it from the left.
▼ This is the Oda River just before the confluence.
The white structure extending into view is the closure levee, which will be extended further to separate the Takahashi River from the Oda River.
Excavation of Minamiyama and construction of a new Oda River channel
Next, let’s look at Minamiyama, in the center of the photo above.
▼ Minamiyama, where a mountain castle is believed to have been built during the Sengoku period, was excavated after archaeological investigations were completed.
After excavation, a new channel for the Oda River will be constructed, directing it to the new confluence.
Work is still underway, and the excavated soil is being used as levee material.
▼ Large machinery is transporting earth and sand.
The embankment in the center is a temporary stockpile of levee material.
All of it will eventually be removed, and the site will become the Oda River channel.
The white wall on the left is planned to become the left-bank levee of the Oda River.
Yanaihara Reservoir and the new confluence
The new Oda River will pass through Yanaihara Reservoir on its way to the new confluence.
The photo above shows the reservoir viewed from downstream.
The facilities installed to treat water during construction will be removed once the work is complete.
▼ Shin-Yanaihara Bridge was newly built over the Oda River just before the new confluence and was completed in August 2022.
It was built as a replacement for the municipal road on the existing levee, which will be removed to create the new channel.
The title lettering was written by Kaori Ito, Mayor of Kurashiki City.
The new confluence has yet to take shape.
The new confluence will be just downstream of Kurashiki Ohashi Bridge, seen on the left (the Takahashi River flows beneath it from left to right).
From the Writer
The photo above was taken in 2020 from the Takahashi River side, showing the closure embankment blocking the Oda River and Takahashi River.
The improvement work, originally planned to take 10 years, was shortened to 5 years, and with early completion anticipated, the project was made visible to local residents by showing them “what” would be done and “by when.” The project is progressing toward completion within the construction period.
Rerouting the confluence will not only reduce the “backwater effect,” in which the Takahashi River blocks the flow of the Oda River, but will also lower the water level at the Sakazu point on the Takahashi River, improving safety.
As of November 2022, the work was progressing smoothly, and completion as planned was expected.
I would like to express my gratitude to everyone involved in the construction work.
With just over a year remaining until completion in March 2024, let’s look forward to its completion.
Kurashiki Civic Lecture: “Toward Recovery: Mabi’s Embankment Improvements and the Rerouting of the Oda River Confluence” Information
| Name | Kurashiki Civic Lecture: “Toward Recovery: Mabi’s Embankment Improvements and the Rerouting of the Oda River Confluence” |
|---|---|
| Date | November 12, 2022 |
| Location | 1141-1 Yata, Mabi, Kurashiki City, Kurashiki City Mabi Branch Office (formerly the Mabi Health and Welfare Center, 1st floor) |
| Participation fee (tax included) | Free |
| Website | Takahashi River and Oda River Emergency Flood Control Measures River Office |
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