Scattering of regular surface waves by irregular bottom topography in the presence of beach reflection

Submerged breakwaters in the forms of a single bar or a series of bars can provide economical shore protection and avoid the adverse impacts on the coastal water environments. A theoretical model, based on the full potential wave theory, is developed to investigate the scattering of regular surface waves by submerged breakwaters built in front of a reflective beach. The beach reflection is described by a simple theoretical model and permeable breakwaters are studied. The model is tested by available experimental and other theoretical results. The theory is applied to study the effects of beach reflection and the geometrical configuration ( including the porosity, bar dimensions and location) of the breakwaters on the performance (reflection, transmission and energy loss coefficients) of the submerged breakwaters in the form of a single bar, a cluster of periodic bars and a cluster of irregularly arranged bars. The investigation shows that for relative large transmission coefficients, the beach reflection has a significant influence on the shore protection. The existence of beach reflection can either provide shelter for the beach or worsen the beach erosion. Studies on irregular porous bars indicate that the irregularity of bar height plays a more important role than other parameters. For specified separated irregular porous bars considered in this thesis, porous bars with irregular height show better shore protection than periodic porous bars, which have the same mean characteristics as the irregular ones