ORCID
- Borthwick, Alistair: 0000-0001-6053-7764
- Raby, Alison: 0000-0002-8959-0080
Abstract
Efficient absorption of reflected waves at the offshore boundary is a prerequisite for the accurate physical or theoretical modelling of long-duration irregular wave runup statistics at uniform, gently sloped beaches. This paper presents an implementation of the method suggested by Zhang et al. (2014) to achieve reflected wave absorption and simultaneous generation and propagation of incident waves in an existing numerical wave flume incorporating a moving boundary wavemaker. A generating–absorbing layer is incorporated within this 1DH hybrid Boussinesq-nonlinear shallow water equation model such that inshore-travelling incident waves, encompassing bound-wave structure approximately correct to second order, propagate unhindered while offshore-travelling reflected waves are absorbed. Once validated, the method is used to compile random wave runup statistics on uniform beach slopes broadly representative of dissipative, intermediate, and reflective beaches. Analyses of the individual runup time series, ensemble statistics and comparison to an empirical formula based on experimental runup data suggest that the main aspects of runup observed in the field are properly represented by the model. Existence of an upper limit on maximum runup is investigated using a simple extreme-value statistical analysis. Spectral saturation is examined by considering ensemble-averaged swash spectra for three representative beach slopes subject to incident waves with two different offshore significant wave heights. All spectra show f^−4 roll-off at high frequencies in agreement with many previous field studies. The effect is also investigated of the swash motions preceding one particular extreme runup event on the eventual maximum runup elevation.
DOI
10.1016/j.coastaleng.2016.04.019
Publication Date
2016-08-01
Publication Title
Coastal Engineering
Volume
114
ISSN
0378-3839
Embargo Period
2017-08-01
Organisational Unit
School of Engineering, Computing and Mathematics
Keywords
Wave runup, Beaches, Irregular waves, Computational methods, Boussinesq equations
First Page
309
Last Page
324
Recommended Citation
Fitzgerald, C. J., Taylor, P., Orszaghova, J., Borthwick, A., Whittaker, C., & Raby, A. (2016) 'Irregular wave runup statistics on plane beaches: application of a Boussinesq-type model incorporating a generating-absorbing sponge layer and second-order wave generation', Coastal Engineering, 114, pp. 309-324. Available at: https://doi.org/10.1016/j.coastaleng.2016.04.019
