OPTIMAL DESIGN OF ARTIFICIAL REEFS IN A POCKET BEACH AT NAGASAKIBANA, JAPAN

摘要

A pocket beach is known to be a relatively stable system in terms of longshore sediment transport and shows only a seasonal variation (swing) of a shoreline configuration depending on the dominant wave. Kagoshima Prefecture Government Office has conducted studies on an artificial (submerged) reef project in a pocket beach of Nagasakibana Coast since 1996. Coastal structures that affect a longshore sediment transport system are supposed to be constructed from the down-drift side. However, a field study and a theoretical analysis on optimal set-up of artificial reefs in the pocket beach revealed that artificial reef and also detached breakwater should be installed in the middle of the pocket beach first to minimize the maximum shoreline recession at a terminal beach.