Asakegawa River Sabo Dam (T11-1)

Asake River Sabo Dam (T11-1): A Taisho-Era Masterpiece of Erosion Control Engineering

Nestled in the verdant Asake Valley at the foot of the Suzuka Mountains in Komono Town, Mie Prefecture, the Asake River Sabo Dam (T11-1) stands as a remarkable testament to Japan's early modern efforts in erosion control and civil engineering. Constructed in 1922 (Taisho 11), this stone dam was the first structure in Mie Prefecture to employ the mortared stone masonry technique known as neri-ishizumi, marking a significant milestone in the region's history of disaster prevention infrastructure.

Registered as a Tangible Cultural Property of Japan in 1998, the dam continues to fulfill its original purpose of protecting downstream communities from sediment disasters while simultaneously contributing to the breathtaking natural beauty of the Asake Valley — a beloved destination within the Suzuka Quasi-National Park.

Historical Background: Taming the Asake River

The upper reaches of the Asake River flow through terrain composed of biotite granite that has undergone deep weathering over millennia. Combined with extremely steep topography, the region was historically prone to frequent and severe slope failures, releasing enormous volumes of sediment into the river and causing devastating floods in downstream communities. The Asake River basin was recognized as one of the most severely degraded watersheds in all of Mie Prefecture.

In response to these dangers, formal erosion control (sabo) work in the Asake River basin began in 1888 (Meiji 21), making it one of the earliest such initiatives in the prefecture. In 1897, the national Erosion Control Law and Forest Law were enacted, and the following year the national government began subsidizing erosion control projects. In 1899, the villages of Chigusa, Asakami, and Komono in Mie District became the first areas in the prefecture to receive official erosion control designations.

Among the many dams constructed throughout the watershed, the T11-1 dam holds a special place as the first in Mie Prefecture to use the mortared stone masonry method. The inscription stone embedded in the dam's center face proudly records "Taisho 11th Year Erosion Control Works," commemorating this engineering achievement for posterity.

Why It Was Designated a Registered Tangible Cultural Property

The Asake River Sabo Dam (T11-1) was registered as a national Tangible Cultural Property on September 2, 1998, in recognition of several key attributes. As Mie Prefecture's first mortared stone masonry dam, it represents a pivotal advance in the region's civil engineering history, documenting the transition from earlier dry-stone techniques to more durable mortared construction.

The dam also possesses notable design features that elevate it beyond a purely utilitarian structure. Its central arch-shaped opening — originally a spillway for excess water, now filled in — and the commemorative inscription stone above it give the dam a distinctive architectural character. These design elements reflect the Taisho-era sensibility that even functional infrastructure could embody aesthetic considerations.

Furthermore, the dam's remarkable durability is itself a testament to the quality of its construction. Built upon the exposed granite bedrock of the Asake Valley, with its foundation cut directly into solid rock, the dam has withstood over a century of floods and storms without sustaining any significant damage — a powerful demonstration of the engineering skill of its builders.

Architectural and Engineering Highlights

The Asake River Sabo Dam (T11-1) is located just west of the Ichinose Bridge, which spans the river above the Chigusa Hydroelectric Power Station near the entrance to the Asake Valley. The dam measures 58.1 meters in width and 3.6 meters in height, making it an imposing presence across the river channel.

The construction technique employed — neri-ishizumi (mortared stone masonry) — involves stacking stones and bonding them together with morite (cement-based mortar) between the joints. This method provides significantly greater structural integrity compared to the dry-stone (kara-ishizumi) technique used in earlier dams. The choice of this method for the T11-1 dam in 1922 was pioneering for the prefecture and represented the adoption of more advanced national engineering standards.

One of the dam's most distinctive visual features is the tablet-shaped inscription stone (hengaku) set into the center of its downstream face, which reads "Taisho 11th Year Erosion Control Works." Below this inscription, a horseshoe-shaped spillway was originally installed to discharge excess water, though it has since been filled in. The combination of these elements gives the dam an almost monumental quality, as if the engineers intended it to stand not only as a functional barrier but also as a permanent record of their achievement.

Directly beneath the dam, the thick granite bedrock that forms the foundation of the Asake Valley is exposed. The dam's base was carefully cut into this solid rock, anchoring it immovably in place. This exceptional foundation work is a key reason why the dam has remained completely intact through more than a century of use, showing no signs of flood damage or structural deterioration.

The Asake Valley and Its Dam Heritage

The Asake River Sabo Dam (T11-1) is not an isolated monument but part of a broader network of erosion control structures that together tell the story of over a century of human effort to live in harmony with the powerful natural forces of the Suzuka Mountains. Just upstream, the T11-2 dam — also registered as a Tangible Cultural Property — was built in the same year using the contrasting dry-stone masonry technique, employing massive boulders gathered from the surrounding area with remarkable skill.

Further upstream in the Nekodani (Cat Valley) tributary, the Nekodani First and Second Dams date back even earlier, to the late Meiji period. These structures, known locally as the "Dutch Dams" (Oranda Entei) or "Rope Sag Dams" (Nawadarumi Entei), are said to have been designed under the guidance of the Dutch engineer Johannis de Rijke, who played a pivotal role in modernizing Japan's river management systems. Together with the T11-1 and T11-2 dams, they form a fascinating open-air museum of erosion control engineering spanning the Meiji and Taisho periods.

Visitor Information

The Asake River Sabo Dam (T11-1) is accessible via the road leading into the Asake Valley from the village of Chigusa in Komono Town. The dam is located near the Ichinose Bridge, close to the Chigusa Hydroelectric Power Station — itself a notable heritage site as the oldest power station in Mie Prefecture, established in 1907.

The surrounding Asake Valley is part of the Suzuka Quasi-National Park and offers spectacular natural scenery throughout the year. The valley is particularly popular during summer, when visitors flock to the crystal-clear waters for camping and river recreation, and in autumn, when the hillsides blaze with seasonal foliage typically peaking in early to mid-November.

Access by car is via the Higashi-Meihan Expressway: exit at Yokkaichi IC, follow Route 477 toward Komono, then take the Yokkaichi-Komono-Daian Prefectural Road to Chigusa and continue along the Asake Valley road. From Komono Station on the Kintetsu Yunoyama Line, the valley entrance is approximately 15 minutes by taxi.

Nearby Attractions

Komono Town and the surrounding area offer numerous attractions that complement a visit to the Asake River dams. The famed Yunoyama Onsen hot spring resort, with a history dating back to the year 718, lies just to the south and offers both day-trip bathing and overnight accommodations. From Yunoyama, the Gozaisho Ropeway ascends to the summit of Mount Gozaisho (1,212 m), one of the principal peaks of the Suzuka range, offering panoramic views of Ise Bay and the surrounding mountains.

Aqua Ignis, a popular complex featuring natural hot spring baths, restaurants by renowned chefs, and strawberry picking, is located nearby along Route 477. For nature enthusiasts, the Mie Prefectural Forest (Mie Kenmin no Mori) provides extensive hiking trails, nature education programs, and peaceful forest walks just a short distance from the Asake Valley.

The valley itself is a gateway to several major hiking routes in the Suzuka Mountains, including trails to Mount Shaka (Shakagatake), Mount Kuni (Kunimidake), Mount Gozaisho, and Mount Amagoi (Amagoidake), making it a natural base camp for outdoor recreation in all seasons.