Energy transfer and dissipation during surf beat conditions

New experimental data on energy transfer and energy dissipation during surf beat conditions are presented. Long wave-short wave interaction inside the surf zone leads to broadening of a monochromatic sea state and a net reduction in short wave height. The amplitude decay of bound sub- and superharmonics in the nearshore region is also investigated, and found to commence with the onset of short wave breaking. The sub-and superharmonic decay can be modelled using the local 2(nd) order solution for the bound harmonics. It is suggested that this mechanism occurs for steep wave conditions on mild slopes and where the short waves are not in shallow water at the breakpoint. A wave steepness criterion is given to describe the latter.