Wave Transformation and Runup on Dikes and Gentle Slopes

ABSTRACT Kobayashi, N.; Pietropaolo, J.A., and Melby, J.A., 2013. Wave transformation and runup on dikes and gentle slopes. Coastal flood-risk mapping requires the prediction of wave runup and overtopping of dikes and beaches. The cross-shore numerical model CSHORE is adjusted to predict irregular wave runup on impermeable dikes. The model is compared with 137 wave runup tests and 97 wave overtopping tests. The seaward boundary of the computation is taken at the location where wave setup is negligible. The spectral period and peak period at this boundary location are specified as input. The model predicts the measured cross-shore variation of the spectral significant wave height on the barred and sloping beaches in front of the dikes. The measured 2% and 1% exceedence runup heights are predicted within errors of about 20% for the spectral period used as input to CSHORE. The model predicts the threshold of wave overtopping, but the minor wave overtopping rates can be predicted only within a factor of 10. The model is also compared with 120 tests for wave runup on gentle uniform slopes as well as wave runup data on natural beaches in order to assess the utility of the numerical model for coastal flood-risk mapping on sand beaches.

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