"Nearly 20% of Japan's solar farms face landslide risk" 24 July 2023

Nearly a fifth of solar farms built in Japan are located in areas deemed to be at risk for landslides, a Nikkei study shows, underscoring the need for rigorous monitoring and disaster-prevention measures as climate change raises the frequency of torrential downpours.

Nikkei reviewed the data of 9,250 solar stations collected by the Tokyo-based National Institute for Environmental Studies (NIES). By comparing the locations to government data showing areas prone to landslides, the study found that 1,658 power stations, or 18%, were within hazard zones.

The NIES data is current as of 2020 and includes solar power stations that produce 500 kilowatts of power or more. The data on hazard zones comes from the Ministry of Land, Infrastructure, Transport and Tourism.

Building solar farms often involves cutting trees, decreasing the water-retention capabilities of the ground, according to the agriculture ministry. Furthermore, the rainwater from panels would seep into the ground, which could make inclined surfaces less safe.

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Climate change is compounding the risk of landslides. During the past decade, each year has averaged 4.4 torrential downpours that produced 100 millimeters of precipitation in an hour, a 50% jump from the average seen in the 1980s. Landslides have claimed lives in places such as Atami in Shizuoka Prefecture and Okaya in Nagano Prefecture in recent years.

There have been at least 230 accidents involving solar stations that occurred in forested areas since the feed-in tariff scheme began in 2012. Because local government authorities lack manpower, it has become difficult to check for noncompliance in tree plantings and drainage systems by solar operators.

New technology has become essential for monitoring and enforcement. Last year, the government's Forest Research and Management Organization started providing nationwide data on tree cutting based on satellite imagery.

The growing demand for solar power explains in part how a large number of solar farms were built on inclined land. The power shortage following 2011's earthquake and tsunami disaster in northeastern Japan led to the feed-in tariff system that has spurred the development of the solar power infrastructure.

Solar capacity last year stood at 78.83 gigawatts, or about 12 times the 2012 figure.

Two-thirds of Japan is covered by forests, and the development of solar farms has naturally expanded to hilly areas.