Dam in Kochi Prefecture

2309-Nagase Dam

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2309-Nagase Dam Dam in Kochi Prefecture
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Date of interview: Sunday, 3/2/2014

Following the Yoshino Dam, we went up the national highway along the Monobe River and came to the Nagase Dam.

Sign standing on the right bank

The unique characters depicted on the signs that guide visitors to the area are the work of the late Yanase Takashi, a cartoonist and picture book author with local connections.

Sign standing on the right bank
Sign standing on the right bank

Looking downstream from the left bank

The Nagase Dam, like the Sugita and Yoshino dams, is operated by Kochi Prefecture, but the color orange is used instead of green or yellow, probably because the department that manages the dam is different from that of the Sugita and Yoshino dams. The difference is that the Sugita and Yoshino dams are managed by the Corporate Affairs Bureau, while the Nagase Dam is managed by the Public Works Department.

And the season was early March. Plum blossoms were still in bloom. (...hmm? Plum blossoms, right?)

Looking downstream from the left bank
Looking downstream from the left bank

Nagase Dam Management Office, Kochi Prefecture

It is a relatively large three-story control center. By the way, I was touring with a fellow dam enthusiast, Mr. Kao3541, from Yoshino Dam, although we did not meet by chance.

Nagase Dam Management Office, Kochi Prefecture
Nagase Dam Management Office, Kochi Prefecture

Explanatory sign by the administration office

An explanatory signboard is posted beside the control center, giving an overview of the Nagase Dam. Originally, the Monobe River was a raging river and the upper reaches of the river were a high rainfall area, but the rainfall was not always high, and the area was plagued by drought.

This led to the construction of the Nagase Dam to control floods and maintain the normal functioning of the river, as well as to generate electricity using the abundant water volume of the Monobe River. The downstream Sugita and Yoshino dams were constructed by the Kochi Prefectural Bureau of Public Enterprises for the sole purpose of power generation, but the Nagase Dam and other dams were developed as Kochi Prefecture's first comprehensive river development project under the National Land Development Law as a public works project funded by the national government.

Explanatory sign by the administration office
Explanatory sign by the administration office

The comprehensive river development project itself is led by the national government, but after the Nagase Dam is constructed, the management of the project is taken over by Kochi Prefecture.

Nameplate on top edge railing

Therefore, the nameplate on the top rail of the embankment is the name of the Chugoku and Shikoku Regional Construction Bureau of the Ministry of Construction at that time.

Nameplate on top edge railing
Nameplate on top edge railing

View of the top edge from the left bank

The top end is open to automobile traffic.

View of the top edge from the left bank
View of the top edge from the left bank

Looking downstream from the left bank

It was completed in 1956 and has a stately appearance similar to the Maruyama Dam in Gifu, which was completed in 1955. The "Construction Hazama-gumi" on the main pillar is also austere. It is a mystery to me that I did not take a picture of this nameplate while writing this. Incidentally, the Maruyama Dam was also constructed by Hazama.

What is the building below? It looks like a building leading to an audit corridor. The green roof is probably for waterproofing, but it reminds me of the Sugita Dam and Yoshino Dam.

Looking downstream from the left bank
Looking downstream from the left bank

Nameplate on the left bank

A nameplate is embedded in the slope on the left bank. The sentence is more important than any specification: "The 792 people who left their longtime homes or donated land to build this dam must never be forgotten for a long time.

Nameplate on the left bank
Nameplate on the left bank

Looking upstream from the left bank

The levee is seen from behind the control center. The vertical embankment is white in color but has a stately appearance.

Looking upstream from the left bank
Looking upstream from the left bank

View of the dam lake from the left bank

The water level is a little low, probably because it is early spring.

View of the dam lake from the left bank
View of the dam lake from the left bank

Rim tunnel?

Most rim tunnels are located straight from the top, but the Nagase Dam was in the wrong direction. Whether it was really a rim tunnel in the first place is a mystery...

Rim tunnel?
Rim tunnel?

Nagase Dam discharge facility renewal work sign

It is a construction sign, but it was easy to understand what kind of construction work was being done. Aiki Kogyo is a company in Kochi that is responsible for the construction of sluice gates and pumping facilities.

Nagase Dam discharge facility renewal work sign
Nagase Dam discharge facility renewal work sign

View of the gate pier and gate operation room from the top

It was a Sunday and the construction was closed. The gate pier and operation room are very large.

View of the gate pier and gate operation room from the top
View of the gate pier and gate operation room from the top

Looking downstream from the top through the crest gate

A control bridge is located downstream of the crest gate. The Maruyama Dam has a circular terrace, while the Nagase Dam is made up of straight lines. Even though they are similar dams of the same age, there is a slight difference between them.

Looking downstream from the top through the crest gate
Looking downstream from the top through the crest gate

I can't.

For some reason, I failed to capture this photo with my SLR camera at the time and uploaded it to Instagram. It is a signboard written in the local language that indicates "No Trespassing" in a very Kochi-like manner.

View of the top edge from the right bank

The cranked top edge is also typical of dams of this era.

View of the top edge from the right bank
View of the top edge from the right bank

Looking upstream from the right bank

The curve from the bottom to the top of the upstream face of the embankment is also nice.

Looking upstream from the right bank
Looking upstream from the right bank

Looking downstream from the right bank

It is a very well-proportioned dike. It is also wonderful that it has an austere appearance. Incidentally, there is a concrete structure in the downstream direction of the left bank, which is the foundation of a cement silo, a relic from the time of the Nagase Dam construction. There was a plant on top of the mountain, so the atmosphere at the time of construction and immediately after must have been quite different from that of today.

Looking downstream from the right bank
Looking downstream from the right bank

View of the downstream face of the embankment from further downstream on the right bank

I moved to a place where I could see the downstream face of the levee right in front of me. The well-balanced embankment is a sight to behold from any angle. There are five radial gates on the crest of Nagase Dam, and the three gates in the middle arecrest gate(12.0m wide by 9.37m high), with one gate of different widths on each side of the bank.orifice gate(9.0m wide by 9.37m high).

It seems unusual that a narrow gate with the same bed height as the crest gate has an orifice, but I guess such a combination is possible. In addition, there are two high-pressure valves for low water level discharge in the middle of the embankment, and for some reason the diameters are different: Φ1.0m on the right bank and Φ0.7m on the left bank. We would like to ask questions about this area on our next visit.

View of the downstream face of the embankment from further downstream on the right bank
View of the downstream face of the embankment from further downstream on the right bank

The Nagase Dam was completed in 1956 and has a long history, yet it has a wonderful, well-balanced embankment of smoked silver. The Nagase Dam also holds several mysteries.

Nagase Dam Specifications

LocationNagase, Kakita-cho, Kami City, Kochi Prefecture
River NameMonobe River System Monobe River
ObjectiveF (flood control, agricultural disaster prevention)
N (unspecified water, water for river maintenance)
P(Power generation)
ModelG(gravity-fed concrete dam)
Bank height87m
Bank length207m
Dam volume380,000 m3
Watershed Area295.2 km2
Reservoir area208ha
Total storage capacity49,090,000 m3
Effective water storage capacity41,470,000 m3
Dam operatorShikoku Regional Construction Bureau → Kochi Prefecture
Main body constructorset of staggered shelves
Year of launch1949
Year Completed1956
Name of Dam LakeOkumonobe Lake

Other Equipment/Specifications

Parking lot
Toilet
Park×
PR Exhibition Hall×
Fishing

Map around Nagase Dam

Weather around Nagase Dam

Accommodations that may be close to Nagase Dam

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This article was written by.
Shin Jinma

Dam enthusiast who loves Momosuke Fukuzawa / Dampedia and Dam News administrator / Certified Dammeister (01-018) by the Japan Dam Foundation / Started selling discharge caution goods.https://shop.dampedia.com

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