The devastating Himalayan floods in August exposed an uncomfortable reality for Asia: Infrastructure built in the world’s most fragile mountain systems can threaten security far beyond national borders.

A destructive high-altitude event in Nepal reportedly carried debris more than 100 kilometers downstream, damaging infrastructure and demonstrating how quickly a localized geological disturbance can become a regional emergency.

Against this backdrop, China’s construction of the enormous Medog hydropower project on the Yarlung Tsangpo River in Tibet demands international attention. For Japan, whose infrastructure investments and strategic partnership with India increasingly extend into the country’s northeastern region, Medog presents a growing geopolitical, environmental and economic challenge.

With a planned generating capacity of approximately 60 gigawatts, Medog is expected to become one of the world’s largest hydropower developments. Located near the Namcha Barwa massif in the Eastern Himalayan Syntaxis, the project sits in a geologically complex landscape marked by active faults, steep slopes, glaciers, landslides and powerful river gradients.

The Yarlung Tsangpo enters India’s Arunachal Pradesh as the Siang, joins the Brahmaputra system and eventually flows into Bangladesh. What Beijing presents as a domestic energy project could therefore have significant transboundary consequences for India, Bangladesh and Japan’s expanding strategic interests in South Asia.

The central concern is not simply whether Chinese engineers can build a technically sophisticated dam, but whether the surrounding mountain, glacier, reservoir and river systems can withstand multiple disasters. The 2017 Nyingchi earthquake reportedly triggered more than 1,800 landslides and created temporary dammed lakes, demonstrating the region’s vulnerability to cascading geological hazards.

An earthquake near Medog could destabilize slopes, obstruct river channels or displace large volumes of water. The 1963 Vajont disaster in Italy demonstrated that catastrophic flooding can occur even without........

© The Japan Times