This thesis describes an investigation of the performance of vertical single and double wave barriers. An experimental investigation of the reflection and transmission of regular and irregular waves was carried out. Measurements from three wave probes were used to analyze the reflection coefficient using a least squares method. In the tests, the wave period, wave height, barrier immersion depth, and barrier porosity were varied in order to determine the relationship between the reflection and

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... ansmission coefficients and parameters describing incident wave and barrier characteristics, such as the immersion depth, the distance between barriers and the barrier porosity. The results show that the reflection and transmission coefficients are functions of wave length, immersion depth, distance between barriers and porosity. The frequency dependent transmission coefficient obtained from irregular wave tests was compared with those obtained in regular wave tests. Single barrier and double barrier results have also been compared with predictions based on available theoretical methods. The performance characteristics of single and double barriers have been compared, and it is found that there is a significant reduction in wave transmission in the case of double barrier, without a corresponding increase in wave reflection.