Limits of Wave Runup and Corresponding Beach-Profile Change from Large-Scale Laboratory Data

The dataset from the SUPERTANK laboratory experiment was analyzed to examine wave runup and the corresponding upper limit of beach-profile change. Thirty SUPERTANK runs were investigated that included both erosional and accretionary wave conditions with random and monochromatic waves. The upper limit of beach change U-L was found to approximately equal the vertical excursion of total wave runup, R-tw. An exception was runs where beach or dune scarps were produced, which substantially limit the uprush of swash motion to produce a much reduced total runup. Based on the SUPERTANK dataset, the vertical extent of wave runup above mean water level on a beach without scarp formation was found to approximately equal the significant breaking wave height, H-bs. Therefore, a new and simple relation R-tw = H-bs is proposed. The linear relationship between total runup and breaking wave height is supported by a conceptual derivation. In addition, the relation is extended to U-L = R-tw = H-bs to approximate the upper limit of beach change. This formula accurately reproduced the measured upper limit of beach change from the three-dimensional experiments in the Corps' large-scale sediment transport facility. For the studied laboratory cases, predictions of wave runup were not improved by including a slope-dependent surf-similarity parameter. The limit of wave runup was substantially less for monochromatic waves than for random waves, attributed to absence of low-frequency motion.