Many examples of the extent of damages done to breakwaters by severe wave action were studied and shown herein by means of figures. Details of cross section in reinforcement and repair works being illastrated, it can be traced back to the original design.
　A total of 68 cases of breakwater disasters were studied out of the following harbours, OTARU, IWANAI, ABASHIRI, RUMOI, TODOHOKKE, WAKKANAI, AKITA, SAKATA, NIIGATA, TOYAMA,ONAHAMA, SHIMIZU, KOBE, WAKAYAMA, HIMEJI, KOMATSUJIMA, KOCHI, HAKATA, KANDA, KAGOSHIMA. Most of these examples were chosen exclusively from The Annual Report of Port and Harbour Construction Works (1946～1964, Bureau for Ports and Harbours, Ministrry of Transport). The results of investigation and classification of these examples are briefly stated in the last part of this report.