Sandy beaches play a key role in regional tourism. It is important to understand the principal morphological processes behind preserving attractive beaches. In this study, morphological variation on the Chirihama Coast, Japan, an important local tourism resource, was investigated using two sets of field surveys. The objective was to analyze and document the multi-scale behaviors of the beach. First, long-term shoreline changes were examined based on shoreline surveys over the last two decades. Then, the middle-term behavior of multiple bar systems was analyzed based on the cross-shore profile surveys from 1998 to 2010. An empirical orthogonal function (EOF) analysis was conducted to capture the principal modes of the systematic bar migration. The shoreline analysis indicated a long-term eroding trend and showed that the seasonal variation has recently tended to increase. The profile analysis demonstrated that net offshore migrations of bars have been repeated with a return period of approximately four years. This general behavior of the bar system is similar to the net offshore migration phenomena observed at other sites in the world. EOF analysis revealed a relationship between bar configuration and middle-term variations in shoreline location; when a new bar is generated near the shoreline and a triple bar configuration is established, the shoreline tends to temporarily retreat, whereas the shoreline experiences an advance when the outer bar has most evolved.

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Long-term variations of seabed profiles on Mikawa Coast, Japan, have been investigated using a set of field surveys collected over 46 years. The focus is placed on the migration of nearshore bars under the influence of severe erosion. The variation of the cross-shore bar location is examined in detail. It is shown that the cross-shore periodic movements have been repeated several times with about 10-year cycles. Superimposed on periodical migration, the outer bar position has a clear onshore trend in longer time scale of decades. An attempt has been made to separate the eroding trend and periodic migration of bars by using a time-varying standard profiles. On the basis of the separated results, real type empirical orthogonal function analysis is conducted to effectively capture the characteristics of sand bar migrations.