Hidaka-mura, Takaoka-gun, Kochi

Kusaka River New Spillway

Japan’s longest tunnel spillway

Because the Kusaka River has an extremely gentle gradient of about 1/3000, it is difficult for the river to drain into the Niyodo River during floods, causing frequent damage. So far, two spillway tunnels have been constructed to mitigate this.
However, a series of typhoons in August 2014 caused extensive flooding damage, so a new spillway for the Kusaka River was planned in 2015, and is scheduled for completion in FY 2022.
This will be the longest tunnel spillway in Japan, with a total length of 5,130 m, an inlet of 200 m, and an outlet of 38 m.

The longest in Japan
This spillway will eliminate floor-level inundation for the scale of flooding caused by the typhoons in August 2014.
When completed, the spillway tunnel will be the sixth tunnel in the Niyodo River basin, making a total length of approximately 19.0 km.
In terms of natural-flow spillways (i.e., those that let the water flow naturally without the use of pumping facilities), the total length of the spillway will be the longest in Japan.
Tunnel construction machines and equipment
A drill jumbo equipped with a rock drill to drill holes in the bedrock at the ends of tunnels.
An erector-equipped spraying machine for installing tunnel-shaped H beams
and spraying concrete to solidify them
Various types of machinery and equipment are in use,
including wheel loaders that can scoop up blasting debris
and load it onto neighboring dump trucks by rotating horizontally.
Taking on the challenge of next-generation
infrastructure tourism
In concert with Niyodo River basin tourism resources like “Niyodo Blue,”
we are planning a tour that will use visits to the construction site of one of Japan’s largest waterway tunnels to
present and teach about the process of transition from the construction stage to the management stage,
including the relationship between flooding damage and infrastructure facilities such as spillways and overflow ponds.

Kusaka River
New Spillway
Facility information

Name Kusaka River New Spillway
Location Kochi Prefecture
Purpose Flood control (measures against flooding above floor level)
Size Total length: 5,130 m ; Inlet: 200 m ; Outlet: 38 m
Year construction started FY 2017
Year of completion FY 2022
Management Kochi River and National Highway Office, Shikoku Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism

Wait!
There’s so much more!

Niyodo River

This is a class 1 river that flows from Ehime Prefecture to Kochi Prefecture. Originating from Mt. Ishizuchi, the highest mountain in western Japan, it is known as the Omogo River in Ehime Prefecture and the Niyodo River in Kochi Prefecture. The river is often ranked first in Japan in terms of water quality and river utilization rate, and because of its beauty and mysterious blue color, it is often known as the “miracle river” or “Niyodo Blue”. In recent years, in addition to ayu fishing and camping, water activities such as canoeing, SUP and rafting have become popular. Hidaka Village is the only place on the Niyodo River where you can enjoy houseboats.

Kusaka River Overflow Pond

The Kusaka River overflow pond is one of the largest wetlands in Kochi Prefecture. You can observe seasonal flowers and wild birds in the marsh and by the water’s edge. Winter walks are especially recommended as many birds visit in winter here between November and March. Guided tours of the pond are also available. For details, please contact Hidakamura Tourism Asssociation.

Contact
Address: 2646-2 Hongo, Hidaka-mura, Takaoka-gun, Kochi (the Medaka House)
TEL: 0889-24-5888 (Hidakamura Tourism Asssociation)

Nagoya Submersible Bridge

The bridge between Hidaka Village and Ino Town is an essential everyday route for the local community. It is called a “submersible bridge” because it sinks under the water when the river is flooded during a typhoon. At 191 meters, it is the longest of the Niyodo River’s submerged bridges, and as the furthest downstream, it is also popular as a photo spot.

Contact
Address: Nagoya, Hidaka-mura, Takaoka-gun, Kochi
TEL: 0889-24-4647 (Industry and Environment Division, Hidaka Village)

Guide to the area and sightseeing

The area around the Kusaka River New Spillway has many must-see sightseeing spots.
All kinds of tourist activities are available.

  • Sarudado Cave

    This is a 1,420-meter-long limestone cave that has been passed down as the training ground of the ninja Kusaka Mohei. About 200 meters of it is open for exploration, and guided tours are available. It is a real thrill to walk through the cool cave and see the natural features of the rock intact. For more information on guided tours, please contact the Hidakamura Tourism Asssociation.

    Contact

    • Address: 1619 Okina, Hidaka-mura, Takaoka-gun, Kochi
    • TEL: 0889-24-5115 (Hidaka Village Board of Education), 0889-24-5888 (Hidakamura Tourism Asssociation)

  • Village Station Hidaka

    Here’s where to buy souvenirs! You will find many locally-grown fruit and vegetables from Hidaka Village and Kochi Prefecture. In addition, a wide range of other products such as lunch boxes, prepared foods, souvenirs, sweets, and miscellaneous goods are all on display. From around November to June, specialty fruit tomatoes and mini tomatoes are available.
    [Opening hours] 8:00 a.m. - 6:00 p.m.　[Closed] December 31 (afternoon)-January 2　　Parking lot available (large bus parking available)

    Contact

    • Address: 1478-9 Hongo, Hidaka-mura, Takaoka-gun, Kochi
    • TEL: 0889-24-5199

  • Hidaka Village Omelet Rice Road

    Nine restaurants in Hidaka village serve delicious omelets made with the local specialty of tomatoes.
    A stamp rally with luxury prizes is also underway! (held every year from June to March of the following year) Why not join in and find your favorite dish?
    For more information, please visit the Omelet Rice Road website.
    https://www.hidaka-omuraisu.info/

  • Omura Shrine

    After the Tosa Shrine in Ichinomiya, Kochi City, this is designated as the second shrine of old Tosa province.
    Built in 587, the shrine has a history of over 1,400 years. It is also home to a National Treasure called “Kondoso-kanto-tachi,” (a gilded bronze sword), which goes on display only during the Grand Festival on November 15 every year. Senbon-sugi (“a thousand cedars”) stand along the approach to the shrine. Surrounded by these sacred trees, the whole area is known as a place of spiritual energy.

    Contact

    • Address: 1794 Shimobun, Hidaka-mura, Takaoka-gun, Kochi
    • TEL: 0889-24-7466

  • Imoya Kinjiro Hidaka Main Store

    This is the main store of a confectionery chain specializing in sweet potatoes, with directly managed stores all over Japan.
    The group’s sweet potato chips account for about 50% of the national market share. Freshly fried sweet potato chips, freshly baked sweet potato desserts, and many other unique sweet potato sweets are available only at the store.

    Contact

    • Address: 573-1 Hongo, Hidaka-mura, Takaoka-gun, Kochi
    • TEL: 0889-24-7476

  • Eat & Stay Tomatoto

    Eat & Stay Tomatoto is a guest house with all private rooms, located within an 8-minute walk from Kochi Prefecture’s Niyodo River.
    Four rooms for up to six people, rates from 3,800 yen/person (excluding tax). It might be a good idea to reserve the whole place for friends or family. There is a café on the first floor that offers a menu full of tomatoes from Hidaka Village.

    Contact

  • Kanpo-no-Yado Ino

    The hotel is located on a hill in Ino Town, the birthplace of Tosa washi paper and the very center of Kochi Prefecture, with a beautiful view of the Niyodo River from every room. There are also a variety of baths, including bubble baths, open-air baths, reclining baths, and waterfall baths. Hearing the sound of trains from the open-air bath really gives you a sense of travel. Enjoy the gentle murmuring of the stream and relax.

    Contact

    • Address: 1569 Hakawa, Ino-cho, Agawa-gun, Kochi
    • TEL: 088-892-1580

Access

Contact

Kochi River and National Highway Office, Shikoku Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism
96-7 Rokusenjicho, Kochi, Kochi 780-8023
TEL: 088-833-7631　FAX: 088-833-9309
http://www.skr.mlit.go.jp/kochi/
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