Estimation of Irregular Wave Runup on Intermediate and Reflective Beaches Using a Phase-Resolving Numerical Model

Abstract

Accurate wave runup estimations are of great interest for coastal risk assessment and engineering design. Phase-resolving depth-integrated numerical models offer a promising alternative to commonly used empirical formulae at relatively low computational cost. Several operational models are currently freely available and have been extensively used in recent years for the computation of nearshore wave transformations and runup. However, recommendations for best practices on how to correctly utilize these models in computations of runup processes are still sparse. In this work, the Boussinesq-type model BOSZ is applied to calculate runup from irregular waves on intermediate and reflective beaches. The results are compared to an extensive laboratory data set of LiDAR measurements from wave transformation and shoreline elevation oscillations. The physical processes within the surf and swash zones such as the transfer from gravity to infragravity energy and dissipation are accurately accounted for. In addition, time series of the shoreline oscillations are well captured by the model. Comparisons of statistical values such as R2% show relative errors of less than 6%. The sensitivity of the results to various model parameters is investigated to allow for recommendations of best practices for modeling runup with phase-resolving depth-integrated models. While the breaking index is not found to be a key parameter for the examined cases, the grid size and the threshold depth, at which the runup is computed, are found to have significant influence on the results. The use of a time series, which includes both amplitude and phase information, is required for an accurate modeling of swash processes, as shown by computations with different sets of random waves, displaying a high variability and decreasing the agreement between the experiment and the model results substantially. The infragravity swash SIG is found to be sensitive to the initial phase distribution, likely because it is related to the short wave envelope.

Wave‐ and Tide‐Induced Infragravity Dynamics at an Intermediate‐To‐Dissipative Microtidal Beach

“…As expected, friction is shown to have a major influence on improving average model performance (Conde‐Frias et al., 2017), with higher Manning coefficients reducing modeled R 2% . Although the default value for the run‐up gauge depth is 0.005 m, a larger value of 0.1 m has been fixed during calibration, consistently with other studies (Fiedler et al., 2015; Pinault et al., 2020; Stockdon et al., 2014) which used the same value to extract run‐up from lidar timestacks and numerically modeled swash.…”

A Numerical Modeling Approach for Better Differentiation of Boulders Transported by a Tsunami, Storm, and Storm‐Induced Energetic Infragravity Waves

“…The BOSZ model is a self‐contained collection of subroutines for modeling free surface flows, surf, and swash‐zone dynamics (Roeber & Cheung, 2012). The model accuracy has been validated extensively using laboratory benchmarking tests (Lashley et al., 2020; Pinault et al., 2020; Roeber & Cheung, 2012; Roeber et al., 2010). The BOSZ model can successfully reproduce extreme IGs generated by storm waves, such as those reported during 2013 Typhoon Haiyan (Roeber & Bricker, 2015).…”

Identification of Coastal Sand Deposits From Tsunamis and Storm Waves Based on Numerical Computations

“…The BOSZ model is a self‐contained collection of subroutines for modeling free surface flows, surf, and swash‐zone dynamics (Roeber & Cheung, 2012). The model accuracy has been validated extensively using laboratory benchmarking tests (Lashley et al., 2020; Roeber & Cheung, 2012; Roeber et al., 2010; Pinault et al., 2020). The BOSZ model is able to successfully reproduce extreme infragravity waves generated by storm waves such as reported during the 2013 Typhoon Haiyan (Roeber & Bricker, 2015).…”