Nonhydrostatic and surfbeat model predictions of extreme wave run-up in fringing reef environments

Nonhydrostatic and surfbeat model predictions of extreme wave run-up in fringing reef environments

Lashley, Christopher H. (TU Delft Hydraulic Structures and Flood Risk; UNESCO-IHE)
Roelvink, D. (UNESCO-IHE; Deltares)
Van Dongeren, Ap R. (Deltares)
Buckley, Mark (US Geological Survey Wisconsin Water Science Center)
Lowe, Ryan J. (University of Western Australia)

2018-03-18

The accurate prediction of extreme wave run-up is important for effective coastal engineering design and coastal hazard management. While run-up processes on open sandy coasts have been reasonably well-studied, very few studies have focused on understanding and predicting wave run-up at coral reef-fronted coastlines. This paper applies the short-wave resolving, Nonhydrostatic (XB-NH) and short-wave averaged, Surfbeat (XB-SB) modes of the XBeach numerical model to validate run-up using data from two 1D (alongshore uniform) fringing-reef profiles without roughness elements, with two objectives: i) to provide insight into the physical processes governing run-up in such environments; and ii) to evaluate the performance of both modes in accurately predicting run-up over a wide range of conditions. XBeach was calibrated by optimizing the maximum wave steepness parameter (maxbrsteep) in XB-NH and the dissipation coefficient (alpha) in XB-SB) using the first dataset; and then applied to the second dataset for validation. XB-NH and XB-SB predictions of extreme wave run-up (Rmax and R2%) and its components, infragravity- and sea-swell band swash (SIG and SSS) and shoreline setup (<η>), were compared to observations. XB-NH more accurately simulated wave transformation but under-predicted shoreline setup due to its exclusion of parameterized wave-roller dynamics. XB-SB under-predicted sea-swell band swash but overestimated shoreline setup due to an over-prediction of wave heights on the reef flat. Run-up (swash) spectra were dominated by infragravity motions, allowing the short-wave (but not wave group) averaged model (XB-SB) to perform comparably well to its more complete, short-wave resolving (XB-NH) counterpart. Despite their respective limitations, both modes were able to accurately predict Rmax and R2%.

Wave run-up
Coral reefs
XBeach
infragravity waves
Numerical modelling
coastal flooding

http://resolver.tudelft.nl/uuid:20f2877d-7524-4608-af7d-ff587abf5f53

https://doi.org/10.1016/j.coastaleng.2018.03.007

2020-03-22

0378-3839

Coastal Engineering, 137, 11-27

Institutional Repository

journal article

© 2018 Christopher H. Lashley, D. Roelvink, Ap R. Van Dongeren, Mark Buckley, Ryan J. Lowe