Abstract
The Kaetsu region, Niigata Prefecture, experienced record-breaking heavy rainfall between
the 3rd to 4th August 2022 that originated from stagnated linear rainbands. Intense rainfall up to
150 mm h-1 resulted in numerous shallow landslides on mountain slopes, with a landslide area
rate（ normalized cumulative area of landslides per unit area of landform） of 8.3%. In addition,
hyperconcentrated flow with large woody debris in the Osawa River reached the hamlet of
Koiwauchi, Murakami city, late at night. Fortunately, there were no fatalities caused by the
event. However, damming of the channel by large woody debris resulted in the destruction of
several houses along the river and inundation of the surrounding area. Evacuation of residents
in Koiwauchi was initiated by the local government, based on flood alert information rather than
landslide alert information. This was key to obtaining sufficient lead time for a successful
evacuation. In Koiwauchi, the lessons learned from the 1967 Uetsu flood disaster and the
training program for disaster prevention expert facilitated by Murakami city were instrumental
in bringing about effective and appropriate evacuation behavior.
