Assessment of Aqueduct Bridge Failure in Wakayama City, Japan, Based on Uav Surveying Flights and High-Resolution Sar Data

One span of an aqueduct bridge suddenly collapsed in Wakayama City in western Japan on October 3, 2021. This study investigates the use of remote sensing data for the assessment of bridge situations in the normal time and in accidents/disasters. A field survey was conducted by the authors with the aid of a small UA V. Google Street View photos taken before the accident were also used. Based on these data, it is estimated that more than 5 hangers out of 18 might have failed for the collapsed span when the bridge collapse occurred. The failure of 4 hangers was also confirmed in the adjacent surviving span from the UAV images. The pre- and post-event high-resolution TerraSAR- X intensity images were also introduced to extract the collapsed span from the SAR data.