Simulating wave runup on an intermediate–reflective beach using a wave-resolving and a wave-averaged version of XBeach

Simulating wave runup on an intermediate–reflective beach using a wave-resolving and a wave-averaged version of XBeach

de Beer, A. F. (Deltares; Student TU Delft)
McCall, R. T. (Deltares)
Long, J. W. (St. Petersburg Coastal and Marine Science Center; University of North Carolina)
Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics)
Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)

2021

The prediction of wave runup, as well as its components, time-averaged setup and the time-varying swash, is a key element of coastal storm hazard assessments, as wave runup controls the transitions between morphodynamic response types such as dune erosion and overwash, and the potential for flooding by wave overtopping. While theoretically able to simulate the dominant low-frequency swash, previous studies using the infragravity-wave–resolving model XBeach (XBSB) have shown an underestimation of the observed swash variance and wave runup, which was in part related to the absence of incident-band swash motions in the model. Here, we use an incident-band wave-resolving, non-hydrostatic version of the XBeach model (XBNH) to simulate wave runup observed during the SandyDuck '97 experiment on an intermediate–reflective sandy beach. The results show that the XBNH model describes wave runup and the individual setup and swash components well. We subsequently examine differences in wave runup prediction between the XBSB and XBNH models and find that the XBNH model is a better predictor of wave runup than XBSB for this beach, which is due to better predictions of both the incident-band and infragravity-band swash. For a range of beach states from reflective to dissipative it is shown that incident-band swash is underestimated by XBSB relative to XBNH, in particular for reflective conditions. Infragravity-band swash is shown to be lower in XBSB than XBNH for most conditions, including dissipative conditions for which the mean difference is 16% of the deep water wave height. The difference in infragravity-band swash in XBNH relative to XBSB is shown to mainly be the result of processes occurring outside the swash zone, but approximately 15% of the difference is caused by explicitly resolving incident-band wave motions within the swash zone, such as swash-swash interactions, which inherently cannot be simulated by wave-averaged models.

Infragravity waves
Non-hydrostatic modeling
Runup
Swash
XBeach

http://resolver.tudelft.nl/uuid:63c0651d-bbdb-46aa-bbef-ef6deb8aca27

https://doi.org/10.1016/j.coastaleng.2020.103788

2021-03-30

0378-3839

Coastal Engineering, 163, 1-13

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2021 A. F. de Beer, R. T. McCall, J. W. Long, M.F.S. Tissier, A.J.H.M. Reniers