Estimation of Damage Length of Maritime Structures Caused by Typhoon 9918 Based on iEWE Method

In 1999, Typhoon 9918 struck Kyushu Island, which is located in Western Japan. During the strongest stage of the typhoon, the central pressure was 930 hPa and the maximum wind speed was 45 m/s near the center of the typhoon. The maximum storm tide was over 2 m along the coast of Kumamoto Prefecture on Kyushu Island. Due to the storm surges and wind waves, the typhoon caused enormous damage to maritime structures, including breakwaters, sea walls, sea dikes, jetties, wharves etc. In this paper, the EWE (Equivalent Wave Energy) Method is used to estimate the damage length of maritime structures along the coast caused by Typhoon 9918. Based on 75 previous typhoons, the iEWE Method creates an index that determines the vulnerability of the coast to a typhoon with a specified path. This index is estimated using the path of Typhoon 9918 as determined from the location and the direction of the typhoon at a latitude of 30° N. The vulnerability index of maritime structures is calculated based on the path of the typhoon and coastline. The damage length is estimated using the vulnerability index and the EWE of the typhoon at a latitude of 30° N. Based on the results, the iEWE Method can estimate the damage level of maritime structures that will occur along the coast before a typhoon strikes. Keywords— Damage Length, Equivalent wave energy, Sensitivity, Smoothed damage length, Storm surge, Typhoon, Vulnerability.