Asakegawa River Sabo Dam (T11-2)

Asake River Sabo Dam (T11-2): A Taisho-Era Masterpiece of Dry Stone Engineering

Nestled in the upper reaches of the Asake River within the scenic Asake Valley of Komono Town, Mie Prefecture, the Asake River Sabo Dam (T11-2) stands as a remarkable testament to early 20th-century Japanese civil engineering. Built in 1922 (Taisho 11), this dry stone check dam — formally known as the Ichinose Karaishi-zumi Entei — was constructed using massive natural boulders gathered from the surrounding mountainside, assembled without mortar in a technique that rivals the legendary stonework of the Anō masons of Ōmi Province. Registered as a National Tangible Cultural Property in 1998, this dam continues to protect the valley from sediment disasters while enhancing the breathtaking beauty of the Asake Gorge.

Historical Background: Erosion Control on the Asake River

The Asake River originates at Mount Shaka in the Suzuka Mountains and carves through the Asake Valley before flowing northeast through Komono Town and Yokkaichi City to reach Ise Bay. The upper reaches of the river are composed of biotite granite that has undergone deep weathering over millennia, making the steep terrain highly susceptible to large-scale slope failures. For centuries, the region suffered from devastating sediment runoff that threatened downstream communities.

In 1897, Japan enacted the Sabo Act (Erosion Control Act) and the Forest Act, establishing a legal framework for systematic erosion control. The following year, the national government launched subsidized sabo projects, and in 1899, the villages of Chigusa, Asakami, and Komono in Mie Prefecture's Mie District became the first areas in the prefecture to be designated as sabo protection zones. This marked the beginning of an extensive campaign to tame the Asake River's destructive sediment flows.

The broader context of Japan's sabo engineering tradition owes much to the influence of Johannis de Rijke (1842–1913), a Dutch civil engineer who spent 30 years advising the Japanese government on river management and erosion control. The nearby Nekodani Dams (Cat Valley Dams), also located in the Asake watershed, are known as "Holland Dams" in recognition of the influence of de Rijke's methods. The T11-2 dam, built during the Taisho era, represents the next generation of these erosion control efforts, blending traditional Japanese stone masonry with modern engineering principles.

Why It Was Designated a Registered Tangible Cultural Property

The Asake River Sabo Dam (T11-2) was registered as a National Tangible Cultural Property (Building) on September 2, 1998. Its designation reflects several factors of outstanding value.

The dam is constructed entirely in the karaishi-zumi (dry stone stacking) technique — a method in which massive boulders weighing several tons each are fitted together without the use of mortar or concrete. Each stone, measuring one to two meters in size, was carefully selected from boulders scattered naturally across the riverbed and mountainside. The masons displayed each stone's natural face outward, creating a facade of extraordinary power and character that stands in striking contrast to the more uniform appearance of cut-stone (kenchi-ishi) construction.

What makes this dam exceptional is the precision with which these irregularly shaped boulders were assembled. The builders employed a tani-zumi (valley stacking) pattern, skillfully adapting to the unique contours of each stone while maintaining structural integrity. This combination of raw natural beauty and exacting craftsmanship demonstrates a level of masonry skill that experts have compared to the renowned Anō stonemasons of Ōmi Province (present-day Shiga Prefecture), who were famous for building the stone walls of Japan's great castles.

Beyond its engineering significance, the dam plays a vital role in preserving the scenic beauty of the Asake Valley. Its dry stone construction allows water to permeate through the structure, maintaining the natural flow of the river while preventing destructive sediment surges — a harmonious balance of function and aesthetics that embodies the finest traditions of Japanese sabo engineering.

Architectural and Engineering Highlights

The T11-2 dam is located approximately 100 meters upstream from a small shrine dedicated to the mountain deity (Yama-no-Kami) that has long been revered as the guardian spirit of the Asake Valley. The dam measures 29.1 meters in width and 3.6 meters in height, serving as the main sediment retention structure on the Asake River's primary channel.

Several features distinguish this structure from other sabo dams of the era. The use of dry stone construction (karaishi-zumi) gives the dam excellent permeability, allowing water to filter through while trapping sediment — a technique that proves surprisingly effective even against major flood events. The dam has survived numerous typhoons and heavy rainstorms over its century-long existence without significant damage, a testament to the skill of its builders.

The visual impact of the dam is equally remarkable. The massive, rough-hewn boulders create a facade of tremendous power and dignity. Unlike dams built with uniform cut stones, every stone in this structure has a unique shape and character, giving the overall composition an organic quality that blends seamlessly with the surrounding granite gorge landscape.

The T11-2 dam should be appreciated alongside its companion structure, the T11-1 dam (Ichinose Neriishi-zumi Entei), located downstream. The T11-1 dam, measuring 58.1 meters wide and 3.6 meters high, was built using mortared stone construction (neriishi-zumi) — the first such technique used in Mie Prefecture. It features a decorative inscribed stone reading "Taisho 11th Year Sabo Construction" and originally included a horseshoe-shaped spillway. Together, these two dams represent contrasting masonry traditions from the same era, offering visitors a fascinating comparison of construction methods.

Visiting the Asake River Sabo Dam

The dam is situated in the Asake Valley (Asake Keikoku), one of the most beautiful gorges in Mie Prefecture. The valley lies within the Suzuka Quasi-National Park and serves as a popular destination for hiking, camping, and nature appreciation throughout the year. In autumn, the valley is famous for its vibrant foliage, with peak colors typically appearing from early to mid-November.

The area around the dam is part of the Asake Sabo Learning Zone, an educational trail that allows visitors to observe various types of historic sabo structures while enjoying the pristine natural environment. Crystal-clear waters flow over granite bedrock, creating a landscape of remarkable beauty that the dam has helped preserve for over a century.

To reach the Asake Valley, take the Tomei-Hanshin Expressway to the Yokkaichi Interchange, then follow National Route 477 toward Komono and continue along the Yokkaichi-Komono-Daian Prefectural Road through Chigusa to the Asake Valley road. From Kintetsu Komono Station, the valley is approximately 15 minutes by taxi. There is parking available at the valley entrance.

Nearby Attractions

The Asake Valley area offers a wealth of experiences beyond the historic sabo dams. The nearby Nekodani (Cat Valley) First and Second Dams, also registered as National Tangible Cultural Properties, are known as the "Holland Dams" or "Nawadurumi Dams" and were built using dry stone techniques influenced by Dutch engineer Johannis de Rijke's methods. These dams, among the oldest sabo structures in Mie Prefecture, can be accessed via a hiking trail from the Hatomine trailhead.

Yunoyama Onsen, one of Mie Prefecture's most celebrated hot spring resorts, is located just a short drive south of the Asake Valley. With a history dating back to the year 718, this atmospheric hot spring town offers traditional ryokan inns nestled along a mountain stream. From Yunoyama, visitors can ride the Gozaisho Ropeway to the summit of Mount Gozaisho (1,212 m), the highest peak in the Suzuka Range and one of Japan's 200 Famous Mountains.

The Asake Valley itself is home to several campgrounds and outdoor recreation facilities, including the Asake Lodge, Asake Camp Site, and Asake Keigyoen trout fishing pond, making it an ideal base for an extended stay in the Suzuka Mountains.