A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand

Thesis (M.Eng.) - Asian Institute of Technology, 1979

The circulation of the net movement of water particles on a plane, immobile beach, is investigated experimentally in the absence and presence of a pair of breakwaters used to attenuate an oblique incoming wave train. The main causes for this circulation are firstly the rip currents developed behind the breakwaters due to the variation of breaker height along the breadline in particular, at some point behind the breakwater where the breaker height is minimum, This is the starting point of the rip current. Secondly, the tips of breakwaters act as sources of wave energy in producing currents and the breakwater modifies the incident wave to diffracted wave. The combined effect of the littoral current together with the effects of the breakwater gives rise to the circulation behind the breakwaters. For different wave heights and periods circulations are measured for two different pairs of breakwater, with the constant depth of water, the breakwater gap and the distance to the breakwater from the shoreline. The magnitudes of the measured currents and the computed mean currents which are predictable using the measured wave heights are of compatible order of magnitudes. The circulation pattern and the variation of the current along the circulation cell provide a useful vision for explaining the development of the tombolo behind the breakwater.