A thesis submitted in partial fulfilment of the requirement for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1988

Construction of offshore breakwater and groin will modify the shoreline and finally it will reach an equilibrium state for a given wave characteristics. Offshore breakwater is very effective in stabilizing the shoreline when incoming wave steepness is rather small, but it is not functioning well when the storm attack the beach. Most of the earlier tests are for small wave steepness. Stabilitation of beaches under the oblique wave attack has been studied in a small wave basin in which wavelengths, periods and positions of t he breakwater are variable . Groins and breakwaters used as coastal structures are tested for severe incoming waves. Throughout the experiment the water depth, beach slope, wave direction and sediment size of beach are kept constant. It is found on the study that the changes of bottom topography in the presence of coastal structures very high near to t he shoreline and less in the deeper water. Further it was observed that the development of tombola largely influenced by the position of breakwater. Extensive scouring occurred between the breakwater gaps and the size of tombolo increased with the increase in wave height. The comparison of experimental results with numerical results show good agreement for the beach deformation in the presence of groins.