Time-frequency analysis and digital signal processing are important tools in the field of coastal engineering. Both can be done using techniques like Fourier or wavelet analysis, however, analysts from this field experience a threshold to use wavelet analysis instead of their current methods, often Fourier-based. This is due to the lack of guidelines in the many choices accompanied by applying wavelets. This thesis investigates the added value of wavelet analysis in the field of coastal engineering. There are two wavelet transform types: continuous and discrete. The first one is most often used for time-frequency analysis. The range of signals that can be analysed more accurately has been increased by adding different signal extension methods and a method to quantify the effect of missing data points, based on the wavelets energy distribution. This allows a more accurate time-frequency analysis of time-series that cannot be assessed in the Fourier domain. The continuous wavelet coefficients can also be used for separating incident and reflected waves. Because the wave number of a wave is dependent on its frequency, the wavelet-based method performs equally well or worse for stationary signals than the current Fourier coefficient based method. For coastal engineering time-series with a changing mean water level, the time-dependency of the wavelet transform results in better separation than the Fourier coefficient based case. The discrete wavelet transform is mostly deployed in digital signal processing. Filtering in the discrete wavelet domain allows for better justification of the filtering of different signal elements such as noise and transients for signals that behave non-stationary, like measurements of impacts. The difference with the standard time or frequency domain methods lies within this justification, instead of a 'gut feeling' often used. Different algorithms to determine thresholds for use in noise filters have been tested. The soft applied universal threshold was the most effective of the compared algorithms in filtering noise from a non-stationary signal. In stationary signal cases, the low-pass filter showed better performance. The discrete wavelet decomposition offers many signal processing opportunities due to the wide range of wavelets that can be chosen.

Seaports across the globe form a critical lifeline for 90% of the international trade of goods. To ensure the safe and efficient handling of these goods and protect the hinterland from floods, seaports often construct and maintain a large array of hydraulic structures. Revetments and quay walls are a critical part of this infrastructure. Unfortunately, climate change poses a threat to their structural reliability as extreme sea conditions are expected to become more severe and frequent in the near future. Phenomena such as sea level rise, rising storm surges and wave heights can each result in a decreasing structural reliability for revetments and quay walls along seaports. This thesis describes how a reliability based analysis has been developed to adapt port infrastructure against the impact of climate change in an effective manner. With the creation of computational reliability models, reliability assessments of embankments and quay walls along the Port of Merak and Port of Houston have been performed. Based on findings from these reliability assessments, structural adaptations have been conceptualized and a method has been developed to trial them on cost and efficacy. Next, as to enable the evaluation of structural adaptation on various criteria such as cost – efficacy – and value, adaptation pathway maps and scorecards have been developed. These are consecutively used to set up investment guidelines aimed at providing guidance on which adaptation pathway is advised.

In this thesis, it is studied if the stability of a stone in a granular bed protection, can be predicted by the local output of a three-dimensional (3D) eddy resolving simulation technique. In earlier studies regarding stone stability, Reynolds-Averaged Navier-Stokes (RANS) models are used to determine the loads on the bed. In the resulting stability formulas, depth-averaged flow parameters are used, and the loads caused by turbulent fluctuations are taken into account by the modelled turbulent kinetic energy k. A load caused by turbulent wall pressures is never explicitly taken into account before. With the use of a 3D eddy resolving modelling technique, turbulence can be resolved to a certain extent, by which local parameters can be used to determine the load on the bed. This may result in a more accurate prediction of stone stability, and a more economical design method for granular bed protections. Due to the computational requirements needed for the most detailed eddy resolving modelling techniques, it is concluded that for the aim of assessing stone stability, Improved Delayed Detached Eddy Simulation (IDDES) is the most appropriate 3D eddy resolving modelling technique for now and the nearby future. This modelling technique is also applied in a study regarding the influence of tidal energy turbines in one of the gates of the Eastern Scheldt barrier. In this thesis, special attention is paid to develop a stability formula, which can be used to assess the stone stability in the highly turbulent flow region behind the Eastern Scheldt barrier, based on the output of these simulations (hereafter ”Eastern Scheldt case”). In order to derive a new stability formula, IDDESs are made of the two long sill experiments of Jongeling et al. (2003). In these experiments, an accelerating flow region is present above the sill. At its downstream end, the flow is separating, causing a highly turbulent flow region behind the sill. Thereby, the dominant flow characteristics are similar to those at the Eastern Scheldt barrier. In both regions of the experiments, on top of the sill and in the area downstream of the sill, damages to the granular bed protection are measured. A new stability formula is proposed. To avoid the new stability formula to be grid dependent, the wall shear stress and the pressure gradient are used to represent the loads by drag and inertia respectively. It appeared, that the proposed stability formula does not predict the number of measured stone movements well, for the entire modelled domain of the long sill experiments. Nevertheless, it is hypothesised, that the assumed pre-dominant load terms are right, but that the ratio between those load terms on top of the sill differs from the ratio between the load terms in the downstream area. Two different entrainment mechanisms are described, that may not be predicted accurately by the same stability formula. With regard to the Eastern Scheldt case, the choice is made to derive a stability formula that is only valid for the entrainment mechanism in a highly turbulent flow region behind a sill of backward-facing step. The data, behind the point of separation in the long sill simulations, is used to derive this stability relation. It appeared that the best results are obtained for a stability formula that is similar to the stability relation proposed earlier, with a Cm:b-value of 1. This is in agreement with the hypothesised entrainment mechanisms for this region. Finally, the proposed stability formula is applied to the Eastern Scheldt case. A firm conclusion about the exact influence of the tidal energy turbines on the granular bed protection, cannot be drawn based on this study. However, it can be concluded, that the influence on the stability of the stones seems to be insignificant. At the analysed locations, the loads on the bed even seem to be slightly reduced in the simulation with turbines, compared to the simulation without turbines. At least as important, is the conclusion that IDDES potentially is an appropriate modelling technique to assess the stability of stones in a granular bed protection. For the long sill experiments, the measured flow characteristics are clearly reproduced more accurately when using IDDES, than by applying a RANS model with the same boundary conditions. The computational effort needed for the Eastern Scheldt case is comparable to the computational requirements of the long sill simulations. Nevertheless, in both cases, the effective grid resolution was not yet sufficient to resolve all fluctuations towards the size of 1dn50. Despite the given that the desired resolution is not yet reached in this thesis, the simulated velocity signals of the long sill experiments are in good agreement with the measured ones. The choice between the use of IDDES or a RANS model should depend on the available computational power, time and required accuracy.

“During the last safety assessment of Rijkswaterstaat in 2006 the Afsluitdijk failed on the current safety standards regarding flood protection. A new design was needed which ensured continuous protection against flooding in the future. Large scale and small scale tests are performed to optimize the design. Clear differences in the average wave overtopping discharge are observed between large and small scale. The new design of the Afsluitdijk has a complex geometry and consists of new types of elements of which not much information about the roughness of these elements is available. Also, the combined effect of roughness elements and berm has not been fully investigated yet. This asks for a more accurate method to predict the average wave overtopping discharge for composite slope. Various adjustments to current theories are proposed for this type of structure. “