Physical and numerical modelling on wave-dune interaction processes and beach resilience

Dr Felice D'Alessandro (Università del Salento)

Thursday 1st December, 2016 14:00-15:00 Maths 522


Sandy dunes constitute the natural barrier protecting coastal areas against flooding due to storm surge and wave impacts for millions of people living in close proximity to coastlines all over the world. However, under storm-driven surges, the action of wind and waves can cause severe dune erosion with rapid large-scale morphological changes and possible damages to the nearby infrastructures. Therefore, the behaviour of a dune system subject to incident hydraulic loads in a storm surge condition needs to be predicted within a valuable range of certainty.

In the recent years different numerical models, of time-dependent and time-averaged type, have been developed in order to simulate the wave beach–dune interaction phenomena. As an alternative to numerical models, analytical models typically require marked simplifications in the description of the governing processes, forcing, initial and boundary conditions, whereas numerical models can deal with these aspects with less restrictions. However, analytical models offer advantages since the simplicity make them easy to apply, which is valuable at the initial stage of a project when more qualitative than quantitative estimates are required. Despite the progress advanced in the analytical and numerical modelling, large-scale physical model experiments are still fundamental for the investigation of wave–dune interaction phenomena.

The talk will present large-scale laboratory experiments focusing on the main physical processes driving dune erosion performed in a wave flume with a sandy dune exposed to a combination of water levels and wave conditions, providing observations of different interaction regimes: collapsing, overwash and breaching.

The large set of data has been considered to obtain measurements of beach–dune cross-shore profile evolution, hydrodynamic properties and suspended sediment concentration.

The laboratory data sets have been adopted to calibrate and verify the analytical model proposed by Larson et al. (2004). Furthermore, the profile measurements have been used to calibrate and verify a numerical model predicting the beach-dune profile modifications over the near-shore region.

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