Aging retaining walls across Japan are increasingly prone to collapse during heavy rain and earthquakes, posing significant risks to public safety [1, 2, 3].
This infrastructure crisis creates a dual threat of physical danger to residents and severe financial liability for property owners who may be held responsible for damages [1, 2, 3].
Many of these structures were built during Japan's period of rapid economic growth and are now suffering from systemic weathering [5]. In September 2025, a retaining wall in Tokyo's Suginami Ward collapsed, resulting in the total destruction of a single-family home [2, 4]. The failed structure was approximately 60 years old [2].
Reports indicate the Suginami incident involved the collapse of a five-meter foundation [3]. Similar failures have occurred elsewhere, including a road wall collapse in Isehara City, Kanagawa Prefecture, in 2024 [1].
Experts warn that the materials used in these older walls vary widely in durability. Ryo Sakamoto said, "This retaining wall itself is made of various stones, and some stones are prone to weathering" [1].
When heavy rains or seismic activity increase soil pressure, these weathered walls are more likely to fail [5]. Because these structures are often located on private property, the responsibility for maintenance, and the subsequent costs of failure, typically fall on the owner [1, 2].
Property managers and owners are now being urged to inspect walls in areas with significant elevation changes to prevent future accidents [1, 2, 3].
“Aging retaining walls across Japan are increasingly prone to collapse during heavy rain and earthquakes.”
The prevalence of 60-year-old infrastructure reflects a systemic vulnerability in Japan's urban planning from the mid-20th century. As climate change increases the frequency of extreme weather events, the intersection of aging materials and higher soil pressure transforms private property maintenance into a critical public safety issue.
