Laboratory Observations and Numerical Simulations of Wave Height Attenuation in Heterogeneous Vegetation

Abstract

Quarter-scalephysicalmodelexperimentsandaphase-resolvingnumericalmodel(FUNWAVE)wereusedtoevaluaterandomwave attenuation through two types of synthetic vegetation. The experiment was performed with two peak periods, three water depths, and two stem densities.Foreachcombinationofparameters,freesurfacetimeserieswerecollectedatsevenlocationsthroughoutthevegetation fieldandone location seaward of the vegetation. Each combination of wave conditions was evaluated for the following four different cases: Case A with no vegetation;CasesBandCwithshortandlongspecimens,respectively;andCaseDwithmixedvegetation.Thewaveheightdecayforeachcase was fit to two existing wave height attenuation prediction equations. The decay equations provided reasonable predictions for the normalized waveheightattenuation,withanaverageroot-mean-square error(RMSE)of0.015.Thelinearcombinationofattenuationcoefficientsobtained forthecasesoftheindividualplantsprovidedareasonablepredictionoftheattenuationcoefficientforthecasesofthecombined,heterogeneous vegetation.FUNWAVEwas used to model wave attenuation for these tests using a bottom friction factor calibrated for each run.The numerical attenuation followed the same trends as the measured data, with an average RMSE of 0.017. Similar to the physical model study, it was found thatsumming thecalibrated modelfrictionfactors for thecasesof theindividualplantsreasonablypredicted thewaveheightattenuation forthe casesofthecombinedvegetationwithanaverageRMSEof0.032.DOI:10.1061/(ASCE)WW.1943-5460.0000215.©2014AmericanSociety of Civil Engineers. Author keywords: Wave attenuation; Vegetation damping; Bottom friction; Wetlands; Estuaries; Physical model; Numerical model; FUNWAVE.