Modeling of Coastal Erosion in Exposed and Groin-Protected Steep Beaches

10 Process-based models are suitable tools for reproducing storm-driven erosion. However, their performance has been mainly 11 examined on mild-slope sandy beaches and their use on steep beaches represents still a challenge. Here, XBeach experiments were 12 combined with topographical measurements collected for two storms (16-yr and 5-yr return period) to obtain a reliable model. The model 13 parameters “facua” (parameterized wave asymmetry and skewness sediment transport component), “bermslope” (upslope transport term 14 for semi-reflective beaches), and “wetslope” (critical avalanching submerged slope) were utilized for calibration and validation. The 16-yr 15 storm simulations on an exposed beach revealed that whether “bermslope” increased, “facua” must be reduced, and vice versa, to properly 16 simulate erosion. Adding “bermslope” provided excellent results for these storms when using “facua” and “wetslope” values close to the 17 recommended values. In a groin-protected site, XBeach was successfully calibrated and validated for the tested storms using these 18 parameters, although with different values. These experiments demonstrated that the appropriate use of these parameters can satisfactorily 19 simulate morphological changes on steep beaches for different hydrodynamic conditions and coastal settings (exposed and groin-20 protected