抄録
Beach changes due to wind waves in a lake have been observed at Ukishima region in the Kasumiga-ura Lake. Topographic surveys have been conducted 13 times since 1983 to study the beach changes around three drainage channels. Temporal and spatial changes of the offshore distances to some contours are investigated. It is concluded that the beach changes at Ukishima region are separated into two categories. In one category the beach changes take place around a structure built at the coast, where littoral drift into one direction is dominant. The other is the case of the beach changes under the condition of periodically varying wave direction due to the seasonal change of wind. It is found that these beach changes can be explained through the theoretical solutions of the one-line model. Finally the ergodic concept is introduced to show the applicability of substituting space for time to the analysis of the beach changes.
