RUN-UP SPECTRA OF RANDOM WAVES ON SLOPING BEACHES

Run-up variations due to random waves have been measured on beaches having 1/5 to 1/30 slopes and the run-up spectra have been examined. The main characteristics of run-up spectra obtained from experiments are as follows: (1) The energy saturation is seen in a high frequency region. The run-up spectra in the saturation region show a f-4 and tan4 θ dependence (f: frequency, tan θ: beach slope) and the energy densities are independent of incident wave energy. (2) Only in a low frequency region, spectral energy densities increase with increase in the incident wave energy.These chracteristics of run-up spectra are discussed from a new standpoint that a run-up wave profile consists of parabolas.