2022 Volume 78 Issue 2 Pages I_131-I_139
Typhoon No. 19, which occurred on October 6 in 2019, caused 14 overflows and flood overflows and one levee breach on the Chikuma River in the Shinano River. Although there have been reports of damage surveys of bridges over the Chikuma River, such as Chikuma River Bridge on Bessho Line, Tanaka Bridge, and Unnojuku Bridge, damage surveys focusing on the Chikuma River basin, including its branch rivers, have not been conducted. Therefore, in this study, we conducted a wide-area damage survey of bridges in the Chikuma River basin and organized the damage situation on a map in order to clarify the characteristics of bridge damages. In addition, damage factors of bridges were discussed from the structural (bridging year, total span, width, structural type) and the geographical (river bed gradient, river width, and degree of bends) perspectives. As a result, damage to 6 bridges in the Chikuma River and 14 bridges in the branch rivers were identified. Most of the bridge damage was influenced by bank damage, but 6 cases of bridge damage were found in the branch rivers, 3 of which were wooden bridges.
