Abstract
From late in the evening of September 23 to early morning of September 24, 2022, the
central part of Shizuoka Prefecture experienced heavy rainfall, and the Shizuoka (Regional
Meteorological Observatory) recorded the highest 12-hour precipitation of 404.5 mm in its
observation history. The maximum 24-hour rainfall was also the second highest (416.5 mm)
after the 508.0 mm observed due to the “ Tanabata heavy rainfall ” in 1974. The heavy rainfall
caused outside and inland water flooding in the Tomoe River and its tributaries in Shimizu Ward
of Shizuoka City, resulting in almost 5,000 houses being flooded in the city. Based on the
inundation depth maps prepared by the authors based on their survey of inundation depths at
approximately 1,150 locations, the flood inundation assumption area map (planned scale) and
the inundation area were almost identical. The Torisaka, Ouchi and Shibukawa areas recorded a
maximum inundation depth of just under 250 cm, but this was less than the depth in 1974. On
the other hand, Ouchi, Horigome, Kami areas were flooded with a difference of around 10 cm,
which is close to the depth of the “ Tanabata heavy rainfall ”.
