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PhD Defence Weiqiu Chen | The influence of berms, roughness and oblique waves on wave overtopping at dikes

The influence of berms, roughness and oblique waves on wave overtopping at dikes

Due to the COVID-19 crisis the PhD defence of Weiqiu Chen will take place (partly) online.

The PhD defence can be followed by a live stream.

Weiqiu Chen is a PhD student in the research group Marine and Fluvial Systems (MFS). Her supervisor is prof.dr. S.J.M.H. Hulscher from the Faculty of Engineering Technology (ET).

Dikes are important coastal structures to protect infrastructures, land and people in coastal areas from wave attack. Dike breaching can cause extensive damage and loss of lives. Wave overtopping is one of the failure mechanisms of dikes, which must be taken into account when designing a dike. The average overtopping discharge and flow parameters like flow velocity and layer thickness are often used to describe the wave overtopping. The average overtopping discharge is a key parameter to determine the crest level of coastal structures by ensuring the average overtopping discharge is below the permissible rate. The flow parameters related to individual overtopping events play an important role in eroding dike cover layers, possibly initiating dike breaching in a later stage. Thus, a reliable prediction of wave overtopping is essential for dike design and safety assessment of existing dikes. In practice, berms and roughness elements at the waterside slope are widely applied to reduce the wave overtopping. Additionally, the direction of incident waves is often oblique relative to the coastal structures. Existing guidelines have shown that roughness, berms and oblique waves can have significant influence on the wave overtopping at dikes. However, these effects have not been fully understood. Better estimates of these influence factors will help improve the prediction of wave overtopping and lead to more suitable estimates of the risk of coastal flooding events. Therefore, the aim of this thesis is to determine the effects of roughness, a berm and oblique waves on wave overtopping processes. To achieve this aim, both physical model tests and numerical simulations were performed and described in this thesis. The performed research has provided new insights into the effects of roughness, berms and oblique waves on wave overtopping. New expressions to account for these effects have been developed based on physical and numerical modelling. The design and safety assessment of dikes can be improved based on the outcome of this research.