Recently, there have been a high demand for new ways of coastal protection works which enable the coasts to hold safety for the people and natural beauty and to be utilized for various purposes including recreational activities. This diversified demand cannot be fulfilled with only the construction of 'hard' structures for beach erosion control but the auxiliary use of some 'soft' controlling devices such as artificial seaweed might bring about much improvement if they are effective. The effects of artiticial seaweed of various kind are examined experimentally to see its usefulness for protecting beach erosion and sea bed scour resulting from the installation of 'hard' caostal structures.
　Five materials are chosen as the seaweed materials of favorable effectiveness, and those are tested in a wave channel having a quasimovable bed. During the experiemnts, the behaviour of the sandy sea bed with and without artificial seaweed, the effect of the seaweed on the wave induced movement of the sand and on teh velocity field around the seaweed were carefully observed. It is concluded that the installation of the artificial seaweed of some kind has a remarkable effect ot help the sand to move onshoreward and also to accumulate on the planted areas.