Abstract
On August 3-4, 2022, torrential rain caused by a linear stationary rainband mid to
downstream of the Arakawa River caused 161 mm/h precipitation at Kamiseki in Sekikawa
Village and 508 mm/6h precipitation at Sakamachi in Murakami City. In the area of Koiwauchi
in Murakami City, debris flow caused by the collapse of solidified weathering granite upstream
of the Osawa River, which runs through the alluvial fan, partly or completely destroyed houses.
However, only one person was injured, likely because all households were evacuated to a public
hall before the destruction. In the region of Yusawa Onsen in Sekikawa Village, debris flowed
into the hot spring resort, and approximately 150 cm floodwaters caused significant damage,
albeit not as much as the 193 cm waters during the Uetsu flood disaster in 1967. Surrounding the
JR Sakamachi Station in Arakawa District of Murakami City, inland waters swollen from
torrential rain and the muddy stream of the Osawa River were flooded, and the maximum
immersion depth at 168 cm.
