Verification of the numerical wave model SWAN in the Petten coastal area

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Abstract

Due to the new act on the water defense the Directorate-General of Public Works and Water Management of the Netherlands is required to evaluate the design conditions for the coastal defenses every five years. To do this evaluation a model is needed to translate offshore wave conditions to nearshore design conditions. For such transformations numerical wave models SWAN and HISWA are available. These models take the relevant processes of wave propagation, generation and dissipation into account. During the storms of January of 1995 a measurement campaign was conducted. From this campaign wave data was obtained to verify the numerical wave models. The wave measurements were taken on a 8.3 km long transect perpendicular to the coastline. Placed 8.3 km offshore there is 1 wave rider buoy to register the incoming waves. Further 2 buoys, 1 pressure transducer and 1 wave staff are used. Three storm situations with waterlevels of 2 m (+ NAP), incoming significant wave heights between 4.5 m and 5.1 m and peak periods between 10.0 sand 14.3 s are used. These situations are modeled with SWAN and HISWA and wave parameters as well as spectra are compared to the wave parameters and spectra. It shows that the results of the SWAN computations for significant wave height are within 6% accuracy. The results of HISWA computations are with 10 % accuracy. The mean zero crossing periods in SWAN are within 10 % of the observed. Spectra reproduced in SWAN resemble well with the observed spectra.