Vegetarian's Japan Guide

The Best Guide to Yamba Dam and the Surrounding Attractions

Yamba Dam (八ッ場ダム) at the south end of the Agatsuma Gorge is undoubtedly the most prominent landmark of Kawarayu Onsen. It can even be said that the construction of Yamba Dam made the hot spring town famous. While the dam has caused much controversy, its completion is definitely an asset to not only Naganohara Town (長野原町), but also the wider Kantō region.

A Table of Contents

What to Do at Yamba Dam

Like many dams in the world, walking on top of the dam is possible. But if you are afraid of heights, it can be scary to walk across the Yamba Dam at its height of 116 meters! The dam has a sightseeing elevator that takes you down from the top to the river’s left bank. It is where you can get a close-up view of the dam’s water outlet. If you want to cross the river, there is no need to head back up. The red Yamba Momiji Bridge (八ッ場もみじ橋) crossing the Agatsuma River, in front of the Yamba Dam allows you to do so. When the timing is right, you can see the impressive water discharging from the dam. In fact, the water pouring down will be within meters of your view!

During the non-flooding period, Yamba Dam’s full water level is kept. But from July to the 15th of October, the reservoir water level is lowered to 555.2m. So if you are after the spectacular view of the massive amount of water being released from the dam, visit Yamba Dam from around the end of May to mid-October.

Using the water from Yamba Dam, electricity is generated at Yamba Power Station (八ッ場発電所). If you are interested, it is located close to the escalator entrance at the bottom of the dam. The amount of electricity is shown on the notice board. You can also join the Free 30-minute Power Station Tours held from Friday to Monday and on public holidays for a closer look at the power generator.

While the trees are still young, cherry trees are planted at the lakeshore around Yamba Dam. The dam should turn into a new cherry blossom spot in Gunma Prefecture in a few decades!

Yamba Dam’s History

The need for the concrete gravity dam first emerged in 1947, when the Kantō region suffered from a great flood caused by a typhoon. In response to this flood, in 1952, a plan was made to construct a dam on the Agatsuma River (吾妻川) in order to reduce flood damage downstream.

© 長野原町役場

Overcoming various obstacles, the Yamba Dam was completed at the end of March 2020. It is a multipurpose dam built for flood control, securing of water supply, and electricity generation.

As Kusatsu Onsen‘s strong acidic hot spring water flows into Agatsuma River, the dam also plays a role in neutralizing the acidic water. Thanks to Yamba Dam, water coming out of the dam can be used for a range of purposes.

Although the construction of the Yamba Dam had a big impact on the locals, it proved its usefulness during the testing stage. Yamba Dam’s flood testing started on the 1st of October 2019. The plan was to fill the dam up to the full water level (583 meters) across a three to four-month period before draining the water to the lowest water level (536.3 meters). However, a typhoon hit on the 4th of October, and the dam was filled fully in just a few days. Without the dam, a great flood at Agatsuma River’s downstream surely couldn’t have been avoided.

Yamba Museum (なるほど!やんば資料館)

For those interested in Yamba Dam’s construction, the Yamba Museum at the dam’s north end is a great facility to stop by. With images, three-dimensional models, and the topography nearby, you will have a clear idea of the dam and the Agatsuma’s landscape.

You can learn about the construction process and mechanism of Yamba Dam through panels and videos. There is also a large model that recreates the area submerged in the dam lake, and a corner that provides easy-to-understand information about the Yamba area.

© 長野原町役場

Don’t worry if you don’t understand Japanese. English notation is usually underneath the Japanese explanation.

Moreover, You can enjoy a panoramic view of the Yamba Dam area from the observation balcony on the 2nd floor.

  • Yamba Museum is open from 9:30 am to 5 pm.
    • The museum is closed from the end of December to the beginning of January.
  • Yamba Dam is around a 30 to 40-minute walk from the JR Kawarayu-Onsen Station.

Tip: Yamba Museum is another place to get Yamba Dam’s dam card. If you are collecting them, there is a machine on the 1st floor labeled with “八ッ場ダムカード” that distributes the cards. If you are unsure where the machine is, check with staff.

Yamba Viewing Platform (やんば見放台)


To overlook the Yamba Dam and the beautiful emerald green-colored Yamba Agatsuma Lake (八ツ場あがつま湖) from high ground, head to the Yamba Viewing Platform. It is the best observation deck to adore the magnificent views. While you need to hike up the gentle slope, the scenery awaiting at the viewing platform is worth the effort.

In addition, you can ring the Yamba Suijin no Kane Bell (やんば水神の鐘). There is also a free parking lot and toilet facility.

Note that the Yamba Viewing Platform might be closed in winter from December to March for your safety.

Yamba Dam Right Bank Observation Deck (八ッ場ダム右岸展望台)

Yamba Dam Right Bank Observation Deck is the closest lookout from Kawara Onsen Station. The platform is built on top of a small hill, and there is a binocular telescope installed at the observation deck.

If you plan to drive, park at the observation deck’s car park and walk across Yamba Dam for more dam-related attractions on the left bank.

Discover Other Attractions in Kawarayu Onsen

Click the photo for more tourist spots in Kawarayu Onsen!

As you might know already, Yamba Dam isn’t the only attraction in Kawarayu Onsen. The hot spring town has more to offer. The onsen town tucked in Gunma Prefecture‘s beautiful mountain is a great destination to enjoy a range of outdoor activities besides the hot spring. In addition to hiking, there is even a rail bicycle track that allows you to cycle on the abandoned rail line!

For more information, refer to our article on Kawarayu Onsen!