From July 7 to 10, 2023, the activity of a stationary front intensified, prompting the issuance of the emergency warning for heavy rains in Fukuoka and Oita prefectures. In some observation points in northern Kyushu, the recorded rainfall reached the highest levels in history. As a result, the water levels of the Kose River, a primary tributary of the Chikugo River, rose significantly, causing flooding and inundation damage in surrounding areas due to overtopping and overflow. The authors conducted a comprehensive field survey around the affected river levees near the Kose River starting on July 16, 2023, approximately nine days after the disaster. The survey methods included meticulous on-site inspections and detailed aerial photography using UAVs. From the field survey, although the maximum river water level was observed, the damage to the levee was limited. This result suggests that rising water levels on the landside may affect the levee.
