Xu, Z.; Wang, J.; Liang, B., and Chen, Y., 2017. Effects of offshore sand motion on wave runup from reflective beaches by using XBeach model. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No.79, pp. 244–248. Coconut Creek (Florida), ISSN 0749-0208.
The safety of the beachgoers is affected by the high speed swash motion and wave run-up at the beach. As many field studies show, complex of nearshore beach profile and sand offshore motion, such as sandbars and its motion, may influence swash processes by changing break point. But few detailed research was made on the reflective beaches (0.3 < ξ0 < 4.0). In the present work, a series numerical tests were carried to investigate the effects of sand offshore motion by XBeach model. The runup results of XBeach model at different time with sand offshore migration were analyzed, and the 2% runup (R2%) predicted by XBeach model and empirical formula are compared. The effects of sand offshore migration on runup components (wave setup ⟨η⟩ and swash S), and wave energy spectrum were discussed. The milder beach gradient β which induced by the sand offshore motion is not only the reason to make the runup height decrease, but also some other effects induced by sand offshore motion. The magnitude of wave spectrum decreases with sand offshore migration, and the trend wave energy shifts to the infra-gravity band becomes more evident.
