Model tests on beach movement under wave action have shown that for small angles of wave incidence the transport is proportional to this angle. Under these conditions it is possible to determine analytically how the shape of the beach will alter in case when, on a straight coastline, a long structure has been built which completely eliminates beach movement for a certain length of time. Some model tests have well confirmed this theory, which does not, however, apply to the "shadow zone"of the structure, not to the case of short structures