The validity of linear wave theory in determining the efficiency of thin vertical
submerged breakwater located on sloped beaches is analyzed using the Eigenfunction expansion
method. The wave height is calculated shoreward and seaward the breakwater site with and
without the breakwater model. The transmission coefficient and the wave height distribution
around the breakwater were calculated for different beach slopes and incident wave field
conditions. The theoretical results were compared with tlie experimental results carried out in a
tilting wave flume having a variable speed wave generator. It is concluded that; the linear wave
theory is valid only for intermediate waves run over a nearly steep beaches