A new parameterisation for runup on gravel beaches

Video derived runup statistics from ten separate deployments at six field sites have been used to develop a new parameterisation for the prediction of runup of runup on gravel beaches. These data were collected over a 2-year period under energetic storm conditions with significant wave heights of Hs = 1-8 m from gravel beaches and barriers composed of fine gravel (D50 = 2 mm) to large pebbles (D50 = 160 mm). An additional data set was generated using the numerical model XBeach-G, developed specifically for gravel beaches, and this synthetic dataset was used to further explore the role of hydrodynamic and morphological parameters on wave runup. A runup equation was developed using the synthetic data set and validated using the field data. The four parameters in this equation are, in decreasing order of importance, significant deep water wave height (Hs), spectral mean period (Tm − 1,0), beach slope (tanβ) and grain size (D50). The new gravel beach runup equation was found to fit the synthetic data set and the field data extremely well (r2 = 0.97 and 0.89, respectively) and the new equation performs significantly better than existing runup equations, even those specifically developed for gravel beaches.