A series of experiments was conducted to investigate the processes involved in the formation of beach scour, caused by wave action, on a natural beach and a seawall beach. The studies also took into account the determination of the reflection coefficient which characterized the wave reflected from both the seawall and the deformed beach profile. The standing wave, formed by the reflection of the waves, was found to be important in the analysis of beach scour phenomena. For the calculation of the reflection coefficient, two methods were used: the envelope method and the Coastal Engineering Research Center (CERC) method. The results given by the two methods showed excellent agreement. The linear standing wave theory was compared with the second order standing wave theory. The wave surface profile and the corresponding horizontal and vertical velocity components of the water particles at the designated points on the free water surface were calculated on the basis of the two theories. The results of the comparisons indicate that the linear standing wave theory gives good results as a first approximation; therefore, it was used in this study. To predict the scour depth on the natural beach and the seawall beach, regression analyses were performed. The results gave excellent correlation.

Technical Report

Funding: NOAA Sea Grant Program; grant number: 2-35213 (1971-72) ;; grant number: 04-3-158-18 (1972-73);