Saitama Prefecture Dam

0640-arima dam

3.0
0640-arima dam Saitama Prefecture Dam
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Date of interview: Monday, July 15, 2013

I stayed two nights in Tachikawa, Tokyo due to a dam mania exhibition at the Sagami Lake Exchange Center, and decided that it would be a waste to return home via the Chuo Highway, so I stopped by this Arima Dam to drive home via Chichibu. Lake Naguri is probably better known to the locals.

Aiming at the downstream face of the dike...

We went upstream along the river to look up at the embankment from below, but it was off-limits. Too bad. There is a day-trip hot spring facility called "Sawarabi-no-yu" near the dam, so it would be a good idea to soak in the hot spring while visiting the dam.

Aiming at the downstream face of the dike...
Aiming at the downstream face of the dike...

Looking upstream from the bridge near the off-limits chain

I had no choice but to photograph the situation downstream. This is the Arima River, a tributary of the Iruma River. The "Sawarabi no Yu" is glimpsed at the upper right.

Looking upstream from the bridge near the off-limits chain
Looking upstream from the bridge near the off-limits chain

Looking downstream from the bridge near the off-limits chain

Looking downstream on the other side. The river joins the Iruma River just there. Further downstream, families can be seen enjoying themselves on the riverbank. It seems to be a place of relaxation for the citizens of Hanno.

Looking downstream from the bridge near the off-limits chain
Looking downstream from the bridge near the off-limits chain

Arima Dam monument on the left bank

We came to the top level. It was crowded with visitors, probably because it was a holiday. The plantings seem to have been carefully managed.

Arima Dam monument on the left bank
Arima Dam monument on the left bank

View of the top edge from the left bank

The top end of the dam is also open to vehicles, except large vehicles. (Incidentally, the roads around the dam lake are closed to traffic from 9:00 p.m. to 6:00 a.m. the following day.)

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

Downstream view of the levee from the left bank

The Arima Dam is managed by Saitama Prefecture and was the first prefectural dam built. It is the only rockfill dam in Saitama Prefecture. The dam site was clean, but the embankment was a bit grassy.

Downstream view of the levee from the left bank
Downstream view of the levee from the left bank

View of the upstream face of the embankment from the left bank

The Arima Dam serves the purposes of flood control, maintaining the normal function of running water, and supplying water to the Hanno City Waterworks and the Prefectural Wide-area No. 1 Waterworks. The blue structure on the right bank is a selective intake facility consisting of seven high-pressure slide gates.

View of the upstream face of the embankment from the left bank
View of the upstream face of the embankment from the left bank

Water taken from the selective intake system is discharged from the water diversion system or the emergency discharge system, and there is a free overflow flood discharge over the selective intake system.

The flood discharge was not a chute type, but a tunnel type, and the NATM method was adopted for the tunnel construction. The tunnel was constructed using the NATM method for safety reasons due to the poor characteristics of the ground. Incidentally, this is the first tunnel-type flood discharge constructed by the NATM method in Japan.

There is no photo of the flood discharge...I visited the site that day without doing any preliminary research, so I did not know that there was a flood discharge and did not go through it. I would like to see it with my own eyes when I visit again someday.

View of the dam lake from the top

The water level is low on this day, but we assume this is because the water level has been lowered to the flood stage limit. The white building on the right is the administration office.

View of the dam lake from the top
View of the dam lake from the top

View downstream from the top

From the top end, the riprap grass looks more and more overgrown. Still, what does it look like from downstream?

View downstream from the top
View downstream from the top

View of the upstream face of the embankment from the right bank

Both upstream and downstream surfaces are neatly laid out with riprap by tension stone work, but it seems a shame that the grass has grown over it.

View of the upstream face of the embankment from the right bank
View of the upstream face of the embankment from the right bank

View of the top edge from the right bank

I was so sorry to have come all the way to the right bank and not seen the selective intake system and the flood discharge, as I write this article.

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

Downstream view of the levee from the right bank

The most distinctive feature is that it is a tunnel-type flood discharge dug by the NATM method, but apart from this, the embankment is a perfectly ordinary rockfill dam.

Downstream view of the levee from the right bank
Downstream view of the levee from the right bank

Arima Dam Management Station

Lastly, the Arima Dam control center, where I regret that I failed to photograph its greatest feature, the tunnel-type flood discharge dug by the NATM method, but I will close by saying that I now have a good reason to visit again.

Arima Dam Management Station
Arima Dam Management Station

Arima Dam Specifications

LocationAza-Nukusa, Oaza-Shimonaguri, Hanno City, Saitama Prefecture
River NameArakawa River System Arima River
ObjectiveF (flood control, agricultural disaster prevention)
N (unspecified water, water for river maintenance)
W(Water for water supply)
ModelR (Rock-fill dam)
Bank height83.5m
Bank length260m
Dam volume1,690,000 m3
Watershed Area16.9 km2
Reservoir area34 ha
Total storage capacity7,600,000 m3
Effective water storage capacity7,250,000 m3
Dam operatorSaitama prefecture (Kantou area)
Main body constructorTobishima Corporation, Fujita Corporation
Year of launch1969.
Year Completed1985
Name of Dam LakeLake Nagurisailfin sandfish (Arctoscopus japonicus)

Other facilities/observations

Parking lot
Toilet
Park×
PR Exhibition Hall×
Fishing○○ (excluding no-take zones)

Map around Arima Dam

Weather around Arima Dam

Accommodations that may be close to Arima Dam

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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