During the calibration of SWAN for shallow water lakes in the Netherlands, problems have been encountered. Especially the emergence of an unnatural, secondary peak in the low frequency part of the energy density spectrum poses problems. Therefore, this investigation aims to address the nonlinear shallow water source terms in SWAN that may introduce this artefact.

Firstly, the basics of linear wave theory and spectral modelling are introduced. Hereafter, these basics are extended to the modelling on nonlinear wave behaviour, as these phenomena form the basis of the relevant shallow water source terms.

The shallow water lake problem is reduced to a stationary, one dimensional problem, for which several model results are produced using varying parameters. Three main subjects can be identified: 1) the influence of depth-induced wave breaking using the BJ78-model or the $\beta-kd$-model, 2) the proportionality factor of the triad source term using the CCA-formulation, and 3) numerical properties such as frequency resolution and the magnitude of the flux limiter.

The results demonstrate that, for strong winds ($U_{10} = 40$ m/s) in shallow water ($d = 2.5$ m), source term interactions become complex as they are all of similar order of magnitude. Especially the interactions between triad wave-wave interactions and depth-induced wave breaking, and triads and quadruplets are important for determining the resulting wave spectrum. Increased wave breaking reduces the secondary peak but underestimates significant wave heights and dampens the spectrum. A more elaborate wave breaking formulation (the $\beta-kd$-model) showed improved performance, especially when it was set to allow younger wind waves (high $kd$) to develop.

Lowering the effect of the triad source term also removes the secondary peak, but may not be desirable as it is by definition a relevant shallow water source term. Reducing source term interactions by means of a stricter action limiter resulted in instabilities for the quadruplet source term and thus no convergence of the results.

A possible solution may be to investigate the possibility of reducing the effect of quadruplets for shallow water, as this term (together with the triad source term) contributes to the formation of the secondary peak. However, this has not been included in the scope of this investigation. Furthermore, improving the frequency resolution resulted in smoother spectra and less wiggles in the sum of the triad and quadruplet source terms. However, this may affect the performance of the quadruplet source term as this term has been calibrated for a fixed relative frequency resolution.

Recent analysis on measurements in the North Sea has shown a large amount of wave energy ranging in infragravity bands in the North Sea during storm events. To better understand the generation and propagation of free infragravity waves, the SWAN model is used to inspect the infragravity wave pattern, the infragravity wave origins, and the corresponding contribution from different coastlines in the North Sea. The local equilibrium between sea swell wave and infragravity wavebands is applied to parameterize the source infragravity wave along the coastlines bordering the North Sea following the approach of Arduin et. al. (2014). The empirical parameter α1 representing the radiating energy level from each coastline and bottom friction coefficient χ representing the dissipation strength are combined to calibrate the model. 10 storm events with an observed infragravity wave height over 10cm are chosen to gain detailed insight into the evolution of free infragravity waves under extreme conditions in SWAN. A correlation between α1 and χ is found. A relatively good explanation between measured and predicted infragravity wave height can be obtained as long as a large α1 and a large χ are implemented in the model or vice versa, showing an accuracy of up to 75% in the open sea. Based on a proper combination of two variables, the contribution of infragravity energy from each coastline varies spatially in predicted results. The Danish coastline is the dominant region radiating infragravity waves to the open sea and the reflected free infragravity waves could reach the adjacent coastlines such as Netherlands and UK. Behind the peak of an extreme storm event, the excitation of free infragravity energy is observed along the south of the UK coast originating from Denmark. The north of Holland coasts also radiate large amounts of free IG energy but are unable to have a prominent impact in the center of the North Sea due to energy dissipation. These results imply that the radiated infragravity waves can be influential in distant coastlines in the North Sea during storm events and the changes of local coastal dynamics can be attributed to a different generation region due to the storm characteristics.

For the design of coastal structures, the hydraulic loads that act on the coast should be known. These are often based on extrapolation of measurements. However, if the physical relation is unknown, large errors could be made. Therefore, a numerical model can be set up to take the most important processes into account.Yet, uncertainties are present in these numerical models as well. Taking for example the spectral wave model SWAN, it is hypothesised that the wave bottom refraction is not always properly modelled. Previous studies concluded that SWAN overestimates this refraction process near tidal channels, leading to an underestimation of waves entering the channel.This study uses the model SWAN in which different sensitivities are tested to assess the effect on refraction. The focus will be on the spatial and directional resolution as well as the wave propagation scheme that SWAN uses to discretise the propagation terms, which are the default SORDUP scheme and the optional BSBT scheme. From previous studies it is known that also physical processes could impact the bottom refraction, however these are only addressed shortly in this study. The aim of this study is to analyse the current performance of SWAN with respect to refraction and to assess how this performance can be improved.First, an analysis of a simple schematic channel case is made in SWAN, where waves propagate from shallow to deeper water. Physical source terms and wind wave-growth were deactivated in this part. It is found that a coarser spatial resolution can lead to a weaker wave refraction. This is caused by the way SWAN determines the turning rate, which is underestimated by SWAN compared to the theory of Snellius. On the other hand, an overestimation of wave refraction was observed for cases were waves should enter the channel. This is partly caused by the increased diffusion. These findings were taken into practice in a study of the Eastern Wadden Sea, specifically along the Ems channel, where waves propagated from deeper to shallower water. A coarser spatial resolution and the BSBT scheme showed less wave penetration from offshore into the Ems channel. The storm of January 2017 was simulated in SWAN after which a comparison was made to measurements. It was found that SWAN underestimated the wave energy for frequencies<0.15Hz. However, this did not improve by refining the resolution in both spatial and directional domain or by applying a different propagation scheme. SWAN thus overestimates the wave refraction due to bottom gradients if waves propagate to shallower water. In case waves travel to deeper water, refraction can be underestimated. If all physical source terms are deactivated, the effects of resolution on refraction are clearly visible. Including the source terms diminishes this effect. Along the channel edges, effects of increased spatial resolution are notable giving a significant wave height of 12-14cm (6-9%) closer to the measured condition. However, the effects at the coast near Uithuizerwad are negligible.

Combined wave-current flow is defined as flow in which waves and currents are present together. One of its occurrences in nature is at a tidal inlet system, where incoming waves meet either a current in the same (following) or opposite (opposing) direction. This type of flow is different when compared to wave- or current-only flows. As a result, different effects are expected on, amongst others, the (suspended) sediment transport. In this study, we are modelling combined wave-current flow with the non-hydrostatic wave-flow model SWASH. The goal was to extend the present SWASH model to facilitate the modelling of combined wave-current flow, validate model results with experimental data and use the new model to analyse waveforms in combined wave-current flow. Model results for spatially uniform and non-uniform currents showed that the evolution of the wave height over the domain was approximately constant. Validation results of the vertical structure of the flow were in general poor except at the boundary. However, the model is capable of producing qualitatively the same trends as observed in measurements of the horizontal structure of the flow. In particular, the spatial evolution of the skewness and asymmetry was captured fairly accurate by the model. It is recommended to expand the newly developed methods to 3D domains for further validation and analysis.

Een groot deel van het dijktraject tussen Koehool-Lauwersmeer (KL) aan de Waddenzee voldoet nog niet aan de normering. Zo ook de zogenaamde ‘groene dijk’, welke volledig uit grasbekleding bestaat. Dit dijktraject voldoet niet voor het faalmechanisme Gras Erosie Buitentalud (GEBU), mede door een te hoge hydraulische belasting. Momenteel is Wetterskip Fryslân in de verkenningsfase voor dijkversterking van het traject KL, met een totale lengte van ongeveer 50 km. Door de grote omvang van het project geeft dit een uitdagende opgave voor Wetterskip Fryslân. Voor de groene dijk en omliggende dijkvakken is het voorland ‘Noarderleech’ aanwezig, waarvan in de huidige methodes enkel de verhoogde ligging wordt meegenomen. Uit onderzoek uitgevoerd in de ‘POV Waddenzeedijken: Effectiviteit voorlanden’ is gebleken dat ook de aanwezige vegetatie op voorlanden significante golfdempende werking kan hebben. In dit onderzoek is de opgedane kennis in de POV toegepast voor het voorland Noarderleech. Doordat de hydraulische belasting op de achterliggende dijk wordt gereduceerd, bestaat de kans dat dijkversterking op bepaalde delen kan worden versimpeld of zelfs onnodig blijkt. Dit leidt tot de volgende onderzoeksvraag: “Wat is het effect van de vegetatie op voorlanden op de golfcondities?”. Hierbij wordt specifiek naar het voorland Noarderleech gekeken, met de aanwezige vegetatie tijdens de wintermaanden. Voor het bepalen van het effect van vegetatie is gebruik gemaakt van SWAN versie 41.20AB, waarin een 1D model is opgesteld voor verschillende doorsnedes. Hierbij is de bodemruwheid gevarieerd om de vegetatie te simuleren. Initieel is gekeken naar de gevoeligheid van het model voor de ruwheid. Vervolgens is voor verschillende doorsnedes het profiel opgedeeld in verschillende oppervlaktetypes, waarvoor een representatieve bodemruwheid is bepaald. Hieruit volgt de grootte van de golfhoogte-reductie. Tot slot is met de gereduceerde golfhoogte de benodigde dijkhoogte bepaald voor één locatie en voor de totale groene dijk de klei-erosie voor het faalmechanisme GEBU. Uit de gevoeligheidsanalyse volgt dat het golfdempende effect afvlakt voor hoge ruwheden. Daarnaast zijn de golven over het algemeen diepte-gelimiteerd, waardoor de golfhoogte wordt bepaald door de waterdiepte. De lengte van het voorland is een belangrijke parameter, doordat het bepaald hoelang de golf wordt blootgesteld aan de hogere bodemruwheid. Daarnaast zijn de verlopen voor een kort en lang voorland nagenoeg identiek, waardoor met één profiel een goede inschatting voor de omliggende profielen gemaakt kan worden op basis van de lengte. Voor de groene dijk geldt dat de golfhoogtereductie door vegetatie in de orde van 8% ±2% valt. Een reductie van 8% leidt tot 10 cm minder kleilaagerosie. Ondanks dit voldoet de dijk met de huidige methodiek nog niet aan de normering voor GEBU. Tot slot is ook de op het voorland aanwezige zomerkade in beschouwing genomen. Uit de analyse blijkt dat de golfhoogte bij de achterliggende dijkteen niet meer dan 2% reduceert ten gevolge van de kade. Door de extreme windcondities en een strijklengte van 500-600 m is de golfgroei dusdanig dat het effect van de zomerkade teniet wordt gedaan ter hoogte van de achterliggende dijkteen. Voor een effectieve golfreductie is het dus van belang dat de afstand tot de dijkteen klein is en de kruinhoogte zo groot mogelijk. Volgend uit dit onderzoek wordt aanbevolen om de invloed van vegetatie op voorlanden, in de vorm van bodemruwheid, mee te nemen in de beoordeling in het geval de primaire kering initieel niet voldoet. Voor het toepassen in de ontwerpfase zijn de mogelijkheden en beperkingen vanuit omgeving en beheer essentieel, waarvoor verder onderzoek wordt aangeraden. Daarnaast wordt onderzoek naar het effect van bodemruwheid op de spectrale periode aanbevolen.

In the past years, climate change has caused an increasing number of extreme weather events. In the Netherlands this is, for instance, reflected by the growing amount of extreme rainfall events. This creates big issues for water management authorities like water boards. Water boards are often responsible for local streams, that cannot handle the peak discharges caused by extreme rainfall. This raises the question whether measures have to be taken, for instance by creating additional storage areas to decrease discharge peaks. For questions like these computational model studies can be used to gain insight in the distribution of discharges and water levels.

During these model studies often one-dimensional models are used. Recent developments made two-dimensional modelling, including for instance the simulation of inundation, possible for regular users like water boards. Two-dimensional modelling is proved to be more accurate for rivers, compared to one-dimensional modelling. Water boards, however, often deal with water systems of smaller scale. This raises the question whether it is worth for authorities like water boards to invest their resources in this new modelling approach. Several physical system properties are of influence on the answer to this question. Therefore, the main question of this research is:

Which physical processes are of influence to the choice of a modelling approach, one or two dimensional, for the modelling of stream systems in particular situations?

The methodology of answering this question consists of three major parts:

1) identify possible differences in the model properties of 1D versus 2D modelling;
2) analyze the output of test models to see whether the differences in model properties actually influence the effects of physical processes; and
3) analyze a case area to see whether these processes are important in practice.

The research scope consists of the hydrodynamics of systems with a length scale of 10^3 – 10^5 m and a temporal scale of hours to a few days. This range corresponds with a range in discharges of a few cubic meters per second up to a few thousands of cubic meters per second. The choice for this range has been made to be able to analyze the effects between the scales of streams and rivers, as until now mostly rivers have been modelled using 2D modelling approaches.

The starting point of this research has been the analysis of differences in model properties. The used flow equations, numerical methods, computational grids and bathymetry implementation are analyzed and the differences are discussed. Concluding, it can be stated that there are differences, which may be of influence to the model output. The main differences are the number of dimensions on which the flow equations are calculated and the way the bathymetry is schematized by the computational grid.

Using these differences, physical parameters have been specified that were varied in a range of test models. These are mainly the parameters that cause 2D effects, like meandering and varying roughness coefficients. The modelling of flood waves could also cause differences due to the fact that the 1D model is not able to model storage with the used default settings. Lastly, the way the bathymetry is used in the simulations is of great importance, due to the way the bathymetry is discretized in 2D models. The goal of varying these physical properties is to analyze whether these variations would influence the quantity of the effects the differences in model properties are causing. Comparing the output of both a 1D and 2D model, it appeared that there are significant differences in the observed water levels. Generally speaking, the following observations were made:

1. The smaller the simulated spatial scale, the larger the 1D-2D differences are
2. The higher the meandering intensity, the larger the 1D-2D differences are
3. The lower the summer bed roughness, the larger the 1D-2D differences are
4. The larger the 2D grid cell size, the larger the 1D-2D differences are
5. The smaller the flood wave duration, the larger the 1D-2D differences are

The underlying physical processes have been analyzed to see how their influence varies in different situations and for different spatial scales. In the end, six processes were found to be influencing the 1D-2D differences:

1. The effects of grid size on bathymetry discretization
2. The water level and velocity difference in cross-sectional direction for varying roughness
3. The water level and velocity difference in cross-sectional direction for varying meandering intensities
4. The interaction between summer bed and floodplains
5. The Boussinesq approach and consequences for the summer bed – floodplain flow area ratio
6. The effects of storage

When combining the findings of the test models and the analysis of a small scale stream system, it was found that the above processes are of the most influence on the following situations:

1. In situations with a complex bathymetry the process of grid discretization is having the most influence.
2. In situations with a high meandering intensity two physical processes are playing a role: high water level and velocity gradients in lateral direction, and a high summer bed – floodplain interaction.
3. In situations with a very low roughness compared to the surrounding area two physical processes are playing a role: high water level and velocity gradients in lateral direction, and a high summer bed – floodplain interaction.
4. In situations with a lot of elevation changes and open water bodies, a lot of potential storage is present.

In these four situations a 2D approach is preferred, as the physical processes that are present in these situations are all processes that are poorly implemented or represented by a 1D model. Of course, there are also some more practical considerations to be made about the modelling choice. The most important one is the research goal; whether inundation modelling is desired and what the required model output is. Another important consideration is the available time for running the simulations; 2D models have a significantly longer simulation time compared to 1D models.

All things considered, this research provides an overview of the differences in model properties between 1D and 2D modelling approaches, an analysis of the important physical processes that determine the choice of a modelling approach and some recommendations about practical issues one could encounter when performing a modelling study.

The growth of the offshore wind industry results in intensive usage of the sandy seabed in the North Sea, currently and in the coming decades. Large-scale bed forms are present in shallow seas with sandy beds such as the North Sea. The most dynamic bed forms are sand waves. Due to their dynamic behaviour, sand waves can interact within offshore human developments and together with their dimensions pose a threat; e.g. decrease in navigation depth, exposure of submarine cables, interaction with foundations of offshore wind turbines and destabilization of bed protections. A thorough understanding of the dynamics can result in less risks for the offshore wind sector and therefore bring down the levelized cost of electricity from offshore wind.
Currently, sand wave field dynamics are investigated by data-driven analyses. These analyses are based on seabed surveys over preferable more than 10 years and are considered most reliable at the moment. However, these surveys are very costly and/or often not available. Complex numerical models may provide an approach to analyse sand wave dynamics in a cost and time efficient way, though two aspects have to be considered. Not all relevant processes regarding sand wave dynamics are yet understood. Furthermore, due to the large scale of sand wave fields in combination with the fine grid resolution required to model sand waves, large computational efforts form a difficulty for numerical modelling of sand wave fields. Previous numerical studies focused on reproducing the length and height of sand waves. The migration direction is the next step towards the full prediction of sand wave fields and the subject of this research.
Recent data-driven analyses showed migration directions of sand waves in opposite direction over small spatial scale, possibly related to underlying seabed topography. Understanding the governing processes of the migration direction of sand waves including underlying seabed topography is the focus of this research using the numerical process-based model Delft3D.
To this end, an idealized model is used in which underlying seabed topography (tidal sand bank) is included. For a symmetrical tidal velocity signal, it is shown that the presence of the tidal sand bank influences the hydrodynamics on the scale of sand waves. Horizontal tide-averaged flow towards the top of the tidal sand bank on both flanks is observed. This results in sediment transports and migration directions on both flanks of the tidal sand bank towards the top of the tidal sand bank. The horizontal tide-averaged flow pattern around the tidal sand bank is disturbed by the inclusion of a residual current. Sand wave migration on both flanks in the direction of the residual current is the result. Including the S4-tide constituent does not disturb the tide-averaged horizontal flow pattern around the tidal sand bank. However, the asymmetry of the tidal velocity signal enhances migration in the direction of the asymmetry.
Finally, it is shown that also for a more realistic model the transition in migration direction can be explained due to the presence of the tidal sand bank. The tidal sand bank influences the hydrodynamics by creating areas in which the tide-averaged sediment transport in the ebb direction are enhanced and areas in which the tide-averaged sediment transports in the flood direction are enhanced. In this way a transition in the migration direction over the tidal sand bank is observed. The migration directions from the model results and migration direction from data-driven analyses show a comparable transition over the tidal sand bank.

To counteract the effect of climate change, a global agreement was put into force in 2016, aiming to limit the increase in average global warming and reduce greenhouse gas emissions. In that respect, European countries are investing in cleaner sources of energy and predominantly offshore wind, which has seen a rapid growth over the last years. The North Sea is a region suitable for developing offshore wind energy, given its strong wind climate and the relatively shallow waters. Many large-scale offshore wind farm (OWF) developments are currently ongoing in that region, while many more are planned and consented for the coming decades. The concept of large-scale OWF developments has spurred many discussions addressing its potential effect on the greater North Sea region. However, the long-term effect on the surrounding coastal areas has never been studied in detail. Especially for a low-lying country as the Netherlands, assessing the impact of large-scale OWFs is of great importance. This study aims at exploring the effect of future large-scale OWFs in the North Sea, focusing on the wave climate and the coastline response of the Dutch coast. Based on the roadmap for developing offshore wind energy until 2050, existing and future designated OWF areas are accounted in the North Sea region. The effect of OWFs on wind is introduced in a schematized way, with a constant decrease in wind speed of 20% inside the OWF areas, based on literature knowledge. Supplementary, based on the vision of creating an artificial energy island for storing and redistributing the wind farm generated electricity, a 5 km² island is introduced, approximately 30 km away from the Dutch coast. The effect on the nearshore wave climate is studied using the numerical model SWAN, while the resulting effect on the alongshore morphology is assessed using coastline model Unibest-CL+. The impact of future OWFs on the nearshore wave climate is found to be dependent on the size, shape, orientation and distance from the coast of the individual wind farms. Results show a mean decrease in significant wave height in the order of 1 – 2%. In addition, slight changes in wave direction are observed. The effect on wave climate reduces the alongshore sediment transport at the Dutch coast, by an order of 10% with respect to present values. This results in net-induced erosion, which requires nourishment. The study shows that the areas north of Zandvoort and Petten need the greatest nourishment volumes, in the range of 1.5 – 2.5 m³/m/year. This is an additional 1% on the current annual nourishment volumes supplied along the Dutch coast. The underlying study has proved to be effective in quantifying the chain of effects of OWFs and identifying potential hot-spots along the Dutch coast. The knowledge acquired from these effects can be used to optimize future OWF planning in relation to coastline maintenance policies.

This research describes a new method called SWDD (Klopman, Witteveen+Bos, 2018b), which can obtain information on wave propagation directions from the surface elevations at a set of positions. The primary intention of the method is to separate multiple incoming wave components, i.e. wave heights, phases and directions. The goal is to obtain the incoming wave conditions, that can among others be used in the design of (coastal) structures and assessment of moored ship response.

The novelty of this method is that a large number of incoming wave directions is prescribed, equally distributed around a circle. For each of these many incoming wave conditions, the wave amplitude and phase are the unknowns (while the directions are known). The main advantage is that this makes the problem linear and in that aspect easier to solve. The disadvantage is that, most often, the resulting system becomes ill-posed (having more unknowns than equations). This problem is solved by using Tikhonov regularization (Tikhonov and Arsenin, 1977) together with the L-curve method (Hansen, 1992; 2000). The main differences with other common deterministic directional wave-analysis methods are: the SWDD method is free of user-checks after each analysis, the directional resolution is higher, the computation time is faster and a wave field reconstruction after the directional wave-analysis is possible.

The applicability of the SWDD method has been tested using synthetic wave signals for (the sum of) monochromatic long-crested waves, prescribed wave patterns – containing wave-crest curvature and wave amplitude variation – and model results of a mild-slope wave model (WIHA). Multiple sensitivity analyses have been applied to check the sensitivity of the SWDD method to: various physical phenomena (e.g. diffraction and wave amplitude variation), domain variations (e.g. slopes) and input parameter variation. The study shows that the SWDD method is able to analyse irregular wave-fields using an array configuration containing a low number of gauges and a dense grid containing many gauges. Based on the findings an advisory flowchart is presented on how to determine the optimum radius of the array setup for using the SWDD method in practice, both for the analysis of data from phase-resolving numerical wave models and from measurements.

The study shows that the SWDD method is a robust and reliable method to analyse (complex) wave fields on a (near) homogeneous bathymetry. The incoming wave direction(s) and associated wave height(s) are graphically depicted in a polar plot or a directional spectrum.

The United States of America have a safety standard for flood protection of 1/100 year. However the flood protections in the Washington D.C. do not comply with this requirement. During this study the levees in Washington D.C. area were analysed and it was found, that in order to comply with the 1/100 safety standard the levees in the NationalMall needs to be heighten by 0.5mand those near the Anacostia river by 1.5m. The safety standard of 1/100 imposed in the United States of America is not based on exact calculation, therefore another design method was applied, which uses an optimal safety level based on the damage cost of floods and investment cost of flood protections.

The calculation of the optimal return period was based on the ’Standaardmethode 2017’ and it was found that the optimal return period at the NationalMall levee is 1/263 years. At the southern bank of the Anacostia river this optimal return period is 1/373 year. With these return periods new levees were designed in order to ensure the safety of the area of Washington D.C. There were two new levees needed around the National mall. The first was situated north of the Lincolnmemory along the Potomac river and the second replaces the temporary flood defence by the 2nd street SW and had an L-shape facing the Potomac river. The Anacostia levee was stretched on the East side in order to comply with the new 1/373 year safety standard. The old and new National mall levees needed a height of 3.5 m and those by the Anacostia needed a height of 8.5 m. It is important to take cautionwith these new levees as some houses needed to be removed. An attempt was made at modelling the above mentioned floods in ADCIRC to improve the accuracy of the design water levels and to verify the final design. However, the model showed instabilities, preventing the results from being used.
Explanations for these instabilities are the incoming water not being properly ramped up, the large vertical gradients in shallow areas and the upstream and downstream boundaries being too close to each other.

Tropical Cyclones (TCs) are in many regions responsible for severe damages and a great number of casualties, resulting from the severe wind speeds, rainfall, wave heights and storm surges. The recent hurricanes Harvey and Irma are examples of the great devastation that can be caused by a single event, and of the insufficient level of preparedness that is currently present to withstand the adverse effects of such an event. Even in the U.S., which suffers relatively frequently from TCs, and has an extensive track record of historical events, the consequences of Harvey were unforeseen and destructive. Difficulties in determining extreme TC conditions, whether these are rain, wind, wave or storm surge conditions, mostly come from the fact that severe adverse effects caused by TCs are very local. This is the case because the exact track, intensity and size of the storm determine to a large extent which area is affected the most, and what the consequences are for the hydraulic conditions. Small variations in any of these parameters can greatly influence the conditions at any location. This is already the case in regions which suffer relatively often from TCs. In regions that do not suffer as regularly from TCs, data scarcity makes it even more difficult to anticipate adverse consequences. In these regions TCs are nevertheless often responsible for the most severe conditions, and the effects of such events should therefore be quantified in order be able to prepare for such conditions. For extreme cyclone wave conditions specifically, there is an additional problem of feasibly determining extreme wave conditions from cyclone wind conditions. This research presents the Tropical Cyclone Wind Statistical Estimation Tool (TCWiSE) to determine extreme TC wind speeds and focuses on the determination of its accuracy in data scarce regions. The tool was developed by applying it in a case study in the Gulf of Mexico. Moreover a brief qualitative assessment of the available TC wave models has been performed in order to identify an adequate method to determine extreme TC wave conditions from TC wind conditions.

Numerieke modellen worden alsmaar belangrijker om voorspellingen te doen in de waterbouwkunde. Het is namelijk veel eenvoudiger en goedkoper om proeven numeriek te simuleren dan om deze uit te voeren in een laboratoriumopstelling. De numerieke modellen moeten echter wel worden gevalideerd aan de hand van metingen. In dit rapport wordt de bruikbaarheid van het model SWASH getest voor simulaties van golfoverslag op dijken met een keermuur. Hierin worden zowel monochromatische regelmatige golven als onregelmatige golven beschouwd.

Numerical models are incresingly important for predictions in Hydraulic Engineering. They are easier and cheaper to employ than physical scale models. However, these numerical models need to be validated to measurements. In this report the usability of the SWASH model is investigated for dikes with crown walls. Both monochromatic regular waves and irregular waves are taken into account.