ANALYSIS OF TOPOGRAPHIC CHANGE IN THE VICINITY OF COASTAL STRUCTURE USING EMPIRICAL ORTHOGONAL FUNCTION

摘要

The construction of 2 km breakwater at Sendai Port in 1968 caused topographic noticeably change since then. The dominant waves cause northward longshore sediment transport along Sendai Coast; as the matter of fact, this area should be advanced owing to the sand trapping at breakwater. On the other hand, the severe erosion has progressed due largely to the oblique wave confront with breakwater result in wave reflection then interact in beach change. This study aim to analyze topographic change on Sendai Coast using Empirical Orthogonal Function (EOF) technique in order to clarify the evolution. The pattern of the 1 st dominant temporal component which has a contribution as 50.2% correspond to bed elevation change. Moreover, this evolution also conforms to the pattern of the 1 st dominant temporal component from the analysis of shoreline. It can be seen the delayed change from the shallow to the deeper area, which caused by wave reflection from breakwater at Sendai Port. It can be obviously noticed that pattern of the 1 st dominant temporal component are in fact related to physical mechanisms of man-made works. Furthermore, this pattern corresponds with rate of bottom elevation change that mean the 1 st component can explain long-term topographic change in this area.