Abstract
Beach erosion of a reef coast was investigated, taking the Yagaji coast in Okinawa as an example. On this coast, a very shallow flat reef develops with natural shoreward sand transport. Recently, a long groin as well as beach nourishment was constructed as a measure against beach erosion. However, this groin obstructed natural sand movement, resulting in downcoast erosion. A typical, natural coast with coastal characteristics in Okinawa was altered to the artificial coast as the one in Honshu. In the shore protection in Okinawa, the characteristics of reef coasts should be more deeply taken into account to avoid these situations.
