Print Email Facebook Twitter The influence of infragravity waves on the safety of coastal defences: a case study of the Dutch Wadden Sea Title The influence of infragravity waves on the safety of coastal defences: a case study of the Dutch Wadden Sea Author Lashley, Christopher H. (TU Delft Hydraulic Structures and Flood Risk; University of Delaware) Jonkman, Sebastiaan N. (TU Delft Hydraulic Structures and Flood Risk) van der Meer, J.W. (TU Delft Hydraulic Structures and Flood Risk; Van der Meer Consulting Bv; IHE Delft Institute for Water Education) Bricker, J.D. (TU Delft Hydraulic Structures and Flood Risk; University of Michigan) Vuik, V. (TU Delft Coastal Engineering) Date 2022 Abstract Many coastlines around the world are protected by dikes with shallow foreshores (e.g. salt marshes and mudflats) that attenuate storm waves and are expected to reduce the likelihood and volume of waves overtopping the dikes behind them. However, most of the studies to date that assessed their effectiveness have excluded the influence of infragravity (IG) waves, which often dominate in shallow water. Here, we propose a modular and adaptable framework to estimate the probability of coastal dike failure by overtopping waves (Pf). The influence of IG waves on overtopping is included using an empirical approach, which is first validated against observations made during two recent storms (2015 and 2017). The framework is then applied to compare the Pf values of the dikes along the Dutch Wadden Sea coast with and without the influence of IG waves. Findings show that including IG waves results in 1.1 to 1.6 times higher Pf values, suggesting that safety is overestimated when they are neglected. This increase is attributed to the influence of the IG waves on the design wave period and, to a lesser extent, the wave height at the dike toe. The spatial variation in this effect, observed for the case considered, highlights its dependence on local conditions – with IG waves showing greater influence at locations with larger offshore waves, such as those behind tidal inlets, and shallower water depths. Finally, the change in Pf due to the IG waves varied significantly depending on the empirical wave overtopping model selected, emphasizing the importance of tools developed specifically for shallow foreshore environments. To reference this document use: http://resolver.tudelft.nl/uuid:39e8717c-963d-4fe7-8706-108c1e4655e1 DOI https://doi.org/10.5194/nhess-22-1-2022 ISSN 1561-8633 Source Natural Hazards and Earth System Sciences, 22 (1), 1-22 Part of collection Institutional Repository Document type journal article Rights © 2022 Christopher H. Lashley, Sebastiaan N. Jonkman, J.W. van der Meer, J.D. Bricker, V. Vuik Files PDF nhess_22_1_2022.pdf 1.9 MB Close viewer /islandora/object/uuid:39e8717c-963d-4fe7-8706-108c1e4655e1/datastream/OBJ/view