NUMERICAL MODELLING OF 2D WAVE TRANSFORMATION PROCESSES FROM NEARSHORE TO A SHALLOW FORESHORE: COMPARISON BETWEEN THE MIKE21, SWASH AND XBEACH MODELS

摘要

Coastal protection measures against storm surges and sea level rise are designed using extreme hydraulic boundary conditions for the normative storm return period. To obtain these conditions at the shallow foreshore, wave transformation processes from nearshore to foreshore need to be accounted for accurately. For that purpose, three numerical wave models were quantitatively evaluated with field measurement data of a storm event: SWASH, a phase-resolving nonlinear shallow water wave model, MIKE21 BW: a phase-resolving Boussinesq wave model and XBeach: a coupled phase-averaged spectral wave model (for sea-swell) and nonlinear shallow water model (for infragravity waves). Their performance was assessed in predicting the wave conditions at the toe of the dike and in computational demand. SWASH appeared to be the preferential model for the stated purpose. Although MIKE21 BW results were similar to SWASH's, the latter model is numerically more robust and hence, easier to use. An important added value for selection is SWASH being open source. XBeach's wave characteristics output is less straightforward to use.