Predicting flooding events on gravel coasts

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Robert McCall, Gerd Masselink, Timothy Poate, Dano Roelvink

Tuesday 30 june 2015

9:30 - 9:45h at South America (level 0)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 4J. Floodrisk – Flooding

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Gravel beaches and barriers occur on many high-latitude, wave-dominated coasts across the world. Due to their natural ability to dissipate large amounts of wave energy, gravel coasts are widely regarded as an effective and sustainable form of coastal defense. However, despite their usefulness as a form of coastal defense, relatively little research has been directed towards understanding the response of gravel beaches to storms, leading to a lack of understanding of the physical processes on gravel beaches. At present, coastal managers have very limited guidance in choosing coastal management strategies to prevent flooding during storms. In this paper we address this issue by investigating typical flood defence strategies at two natural gravel beaches in the UK using a newly-developed a process-based morphodynamic model called XBeach-G, which has previously been shown to have good skill in simulating hydrodynamics and morphodynamics on gravel beaches during storms. Application of the process-based model warns of an overestimation of coastal flooding resilience in swell-dominated conditions along the southern UK coastline and highlights current beach reprofiling schemes as unsustainable, in particular with respect to extreme storm events.