Composite Modelling I

In the design of physical model experiments in coastal engineering, it is common that the construction of a foreshore is necessary to obtain the desired wave conditions at a given location, usually close to a structure being tested. Since the construction of foreshores is labour intensive (and thus expensive), it is useful to be able to check a priori whether the target wave conditions - both bulk parameters and wave height exceedance distribution - are met with a given foreshore design. One way to do this is by using a numerical wave model. In this work the ability of the XBeach 2-layer non-hydrostatic model to reproduce wave height exceedance distributions over a sloping foreshore is validated using wave flume data. Preliminary results are promising, showing reasonable to good matches of both spectral wave parameters and wave height distribution.

Among the most vulnerable areas in Europe are the coastal urban areas of the Macaronesia Islands territories, since they are characterized with urban settlements in low land areas, being highly exposed to flooding. Within the scope of sustainable development and at the same time with the aim of increasing resilience in these areas, the development of a new methodological framework for implementing risk reduction and adaptation measures in coastal flood-prone areas is being applied with the framework of the LIFE-Garachico project (Tenerife, Spain). One of proposed adaptation options is the implementation of concrete blocks in the form of a bench to be disposed along the municipality seafront with the aim of reducing the impact of water sheets into building, generated by wave overtopping. This study presents the results obtained by means of a hybrid numerical and experimental technique to define the hydraulic performance of different bench configuration.

A wave flume experiment of wave attenuation through cylinder arrays, mimicking wave damping through a coastal mangrove forest in the Mekong Delta, was performed within a wave flume at Delft University of Technology. A state-of-the-art numerical model mimicking the experiment was constructed in SWASH, and validated using the measured data. Results show that short waves are attenuated very quickly, while infragravity waves. Therefore, long wave attenuation will determine the maximum length scale of the mixing layer's intrusion into the vegetation region. It is suggested that the SWASH model can capture the transformation processes of the wave attenuation observed and measured in the physical model. The wave attenuation rate for a specific mangrove density was presented as a function of the number of wavelengths and the Ursell number. It is suggested that the ratio of incoming and damped wave heights reduces when the Ursell number increases.