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

Abstract

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

Uncertainty Analysis Related to Beach Morphology and Storm Duration for More Reliable Early Warning Systems for Coastal Hazards

“…If the profiles maintain approximately the same sand volume, even for different morphologies, the post-storm profile is very similar, especially for very high energetic events, as stated by J. L. Garzon et al (2022a). On the other hand, the LBT and LTT morphology did not alter the erosion indicators notably for any of the events, and minimal changes were only observed in sand eroded volume, with larger eroded volume found in the LBT profiles in relation to the LTT profiles.…”

“…Also, Garzon et al. (2022a) found that the scheme selected to simulate the propagation of the directionally spread short wave groups in XBeach can impact the dune erosion. Here the option considering wave refraction (multi_dir) was implemented.…”

“…Because wave measurements in the surf and swash zone were not available, wave breaker parameters were inspired by values found in the literature (Do et al, 2018;Plomaritis et al, 2018) as displayed in Table 4. Also, Garzon et al (2022a) found that the scheme selected to simulate the propagation of the directionally spread short wave groups in XBeach can impact the dune erosion. Here the option considering wave refraction (multi_dir) was implemented.…”

“…Here the option considering wave refraction (multi_dir) was implemented. The model was calibrated by using variations in three model parameters: facua (parameterized wave asymmetry and skewness sediment transport component), bermslope (upslope transport term for semi-reflective beaches), and wetslope (critical avalanching submerged slope) because they have been found to largely impact the erosion of the steep profiles similar to those assessed here (Cho et al, 2019;J. L. Garzon et al, 2022aJ.…”