A short report on the 2nd International Workshop on Sediment Bypass
Tunnels-Sharing concepts and techniques among Switzerland, Japan, Taiwan, andother SBT-leading countriesThe 2nd International Workshop on Sediment Bypass Tunnels (SBT) was held May
9th to 12th 2017 at Uji Campus, Kyoto University, Japan (1st workshop: ETH Zurich,
Switzerland, 2015). The workshop was organized by Water Resources ResearchCenter, DPRI, Kyoto University (Chair: Tetsuya Sumi), with VAW ETH Zurich andNational Taiwan University as co-organizer, sponsored by Japanese Ministry of Land,Infrastructure, Transport, and Tourism (MLIT), Nagano Prefecture, Kansai ElectricPower Company, Inc., and financial supported by several companies and foundations.
More than 170 people (31 from outside Japan) from 9 countries (Austria, China,Indonesia, Japan, Switzerland, Sudan, Taiwan, USA, and Vietnam) attended. We had
meeting on 9th and 10th at Obaku Plaza Hall in the Uji campus, and study tour (41participants) visiting 3 dams with SBT in Nagano Prefecture from evening of 10th to
12th. As a pre-workshop tour, core members of SBT committee were visited Kobe Cityand Nunobiki-Gohonmatsu Dam, which is one of the oldest dams with SBT in theworld constructed more than 100 years ago.
In the meeting, we had two keynote lectures (Dr. Gorge W. Annandale from US, Dr.
Chien-Hsin Lai from Taiwan) followed by 27 oral and 12 poster presentations on thetopics of SBTs in the world, upstream aspect, tunnel, downstream aspect, andoperation. In the first keynote, importance of sediment management on the reservoir
sustainability, required developments in techniques and strategies of SBT and othermeasures, and future issues related to climate change and reservoir sedimentation
were shown with an idea of ZEN. In the second keynote, severe sedimentation aspresent reservoir status in Taiwan after earthquake and typhoons, and three new SBT
attractive projects of increasing reservoir storage and discharge capacity were shown.
Presentations included historically initiative SBTs in Kobe, international comparisonsof SBT characteristics, sediment bypass system in Indonesia, prediction methods ofwater and sediment inflow from upstream, sediment dynamic model for the predictionof invert abrasion, developments in monitoring of sediment transport through SBT,
recoveries of downstream geomorphology and ecosystem by sediment supply, DNAmetabarcoding as a new technique for environment evaluation, ongoing projects (plan,operation, monitoring) of visiting SBTs in Nagano.
Exchanges and discussion of idea, experience and techniques were done also forposter presentation and company exhibition during lunch and coffee breaks.
Discussion through this workshop helped deeper understanding of SBT since the lastworkshop, while revealed several issues to be solved including upstream-downstream
linkage and economic evaluation of SBT projects in a long-term dam redevelopment.
After the meeting on 9th we move to Kizakura (famous sake company) in Fushimi areaof Kyoto City and had welcome reception. Participants enjoyed sake brewing systemthat developed in spring-water-rich location of Kyoto and traditional culture of Kyoto,
old capital of Japan.
In the study tour, we stayed two nights in Nagano and visited SBT facilities ofMatsukawa, Koshibu, and Miwa dams and sabo works in the Mibu River upstream. We
took time to see tunnel inlet and outlet of each dam, drove through the 4 km SBT ofKoshibu Dam by bus, devices to transport fine materials in the Matsukawa, lining forabrasion and sediment monitoring system of the Koshibu, upstream stockyard system
to increase sediment bypass ability in the Miwa, and sabo works and check dams thatprevent sediment inflow to the Miwa Dam. An environmental monitoring survey was
also demonstrated in the downstream of Miwa Dam.
Participants interested in variable topics including effects of each facility, evaluationof sediment budget, determination of target grain size for transportation, techniquesof abrasion countermeasures, impact response of downstream environment. Thanks
to a good weather during the tour, participants also enjoyed nature and aspring-season view of mountains. Although SBT is a specific field of investigation,
discussion was expanded to future-promising broader themes. We confirmed ourcontinuous international cooperation and importance of translating our SBT
knowledge to solve sedimentation issues of rivers and dams worldwide. This
workshop was finished with great success, and we will continue to cooperate to havethe 3rd International Workshop on Sediment Bypass Tunnels in Taiwan 2019.

Participants of the meeting

KeynoteCompany exhibition

Discussion

Kyoto culture in reception

Study tour at SBT outlet of Miwa

Miwa upstream with South Japan Alps

Pre-workshop tour (Minatogawa tunnel)

Unlined tunnel of Nunobiki-Gohonmatsu
constructed more than 100 year ago.

SBT cup as asouvenir ofworkshop

Field survey of environment atdownstream site of Miwa.