Limits of Beach and Dune Erosion in Response to Wave Runup Elucidated from SUPERTANK

The unique dataset from SUPERTANK is analyzed to examine the upper limit of beach change in response to elevated water level caused by wave runup. Thirty SUPERTANK runs are investigated, including both erosional and accretionary wave conditions under random and monochromatic waves. The upper limit of beach change approximately equals the maximum vertical excursion of swash runup. Exceptions to this direct relationship are those with beach or dune scarps. The vertical extent of wave runup above mean water level on a non-scarped beach is approximately equal to the significant breaking wave height. Scarps substantially limit the uprush of swash motion, resulting in a much reduced maximum runup. Predictions of wave runup are not improved by including a slope-dependent surf-similarity parameter. The limit of wave runup is substantially less for monochromatic waves than for random waves, attributed to absence of low-frequency motion for monochromatic waves.