12th East Asian Dam Conference (EADC)

Technical Tour (Optional)

A two-days technical tour is planned to visit Koshibu Dam (concrete arch dam, sediment bypass tunnel) and Shin Maruyama Dam (upgrading of concrete gravity Dam, under construction).
①Number of participants: 80 (estimated)
②Tour guides: Several host committee staff members and a English interpreter per bus
③ Means of transportation: Two buses(G
roup A and Group B)
④ Date and time:
          Day 1: June 6, 7:30-19:00
          Day 2: June 7, 7:30-19:00

Day 1: (A)Nagoya City➡Koshibu Dam Tour➡(Magomejuku)➡Nagoya City
Nagoya City➡(Magomejuku)➡Koshibu Dam TourNagoya City
Day 2:(A)Nagoya City➡New Maruyama Dam and Power Plant➡Ena Gorge➡Origawa Dam➡Roadside Station Obaachan-Ichi/Yamaoka➡Nagoya City
Nagoya City➡Origawa DamRoadside Station Obaachan-Ichi/Yamaoka➡Ena Gorge➡New Maruyama Dam and Power Plant➡Nagoya City

Tour Day 1: Koshibu Dam and Sediment Bypass Tunnel

Koshibu Dam is a Concrete Arch Dam constructed in 1969 on the Koshibu River, a branch of the Tenryu River system.
It is a multi-purpose dam for flood control, irrigation, environmental flow, and power generation, and managed by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT).


The Tenryu River system is a watershed with extremely high sediment production, and the rapid increase in sedimentation after dam construction, which exceeded expectations, was causing a decline in dam functions.
As a drastic measure against this sedimentation, the Koshibu Dam has installed a sediment bypass tunnel. The sediment such as sand, gravels, and wash-load into the reservoir are bypassed to the downstream of the dam. The sediment bypass tunnel was completed in 2016.


Tour Day 2; Shin Maruyama Dam
(One of the Largest Dam Upgrade Project in Japan)
Maruyama Dam, for which dam rehabilitation of the dam body is currently underway, is a concrete gravity dam completed in 1956 with a dam height of 98.2 m. The purpose of the dam is flood control and power generation.
Shin Maruyama Dam Project was started in 1986. The height of Maruyama Dam rises by 20.2 m. Shin Maruyama Dam will be able to store 3.6 times more water than the Maruyama Dam during a flood event. Of the 72 million m3 flood control capacity, 15 million m3 will be effectively utilized through preliminary releases of unspecified capacity which is set for environmental flow and low flow augmentation.

The axis of the new dam was moved 47.5 m downstream from the existing dam axis, and a special structure was adopted in which the new dam body sits on the downstream face of the existing dam body.