دانلود رایگان مقاله پارامتریکی جدید برای runup در سواحل ماسه

Abstract

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.

4. Discussion and conclusions The development of any empirical equation is strongly dependent on the quality of the data upon which it is based. The field dataset from a range of sites presented here includes information on beach morphology and sedimentology, wave conditions and extreme runup, and all parameters extracted from these measurements are subject to a natural variability, as well as measurement error. Not surprisingly, therefore, considerable scatter remains in the data, even when fitted to the ‘best’ equation or the XBeach-G model. The largest cause of scatter in the data is considered to be the estimation of the runup elevation from the video data. Apart from pixel resolution and issues with appropriate identification of the leading edge, there is also the assumption that the beach is planar, two-dimensional and stable during the experiment. Additionally, considering the relatively short time series (17 min) and the long wave periods generally encountered under the more energetic wave conditions (Tp N 10 s), the 2% runup statistic is often based on only a handful of runup events. Nevertheless, the methodology used is identical to that deployed in the more recent previous runup studies (Aagard and Holm, 1989; Holland and Holman, 1993; Ruessink et al., 1998; Ruggiero et al., 2001; Stockdon et al., 2006).