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Wedstrijdzeilen is een sport waarbij taktiek een grote rol speelt. Dit komt onder andere tot uiting door de wijze waarop de wedstrijdzeiler gebruik maakt van winddraaiingen en de positie van zijn tegenstanders. In een aantal gevallen kan daarbij kennis van de lokale stroomsituatie een voordeel zijn. In september 1988 vonden de Olympische zeilwedstrijden plaats in de baai van Pusan, een havenstad in Zuid-Korea. Voor een optimale voorbereiding op deze zeilwedstrijden is de Nederlandse zeilploeg reeds drie jaar tevoren begonnen met verkenning van de lokale weers- en stromingssituatie. Bestudering door de zeilploeg van deze vergaarde gegevens leidde niet tot herkenning van een vast patroon in de stroming, ook niet in relatie met de gemeten windsnelheden en -richtingen. Dit is de reden dat aan vertegenwoordigers van het Waterloopkundig Laboratorium en Meteo Consult is gevraagd deze gegevens ook eens te analyseren. Uit deze analyse bleek dat het mogelijk moest zijn aan de hand van getij- en windgegevens de stroming nabij Pusan te berekenen. Voorjaar 1988 is besloten tijdens de Olympische zeilwedstrijden dagelijks een weers- en stromingsverwachting te leveren. De weersverwachting zou daarbij door Meteo Consult geleverd worden. Het Waterloopkundig Laboratorium voerde vervolgens, mede op basis van deze windvoorspelling, een stroomberekening uit. In dit verslag wordt ingegaan op de inhoudelijke aspecten van deze stroomberekeningen.

Fort Bay harbour is a small harbour, located at the South of the island of Saba. This island is part of the Netherlands Antilles and it is situated in the Caribbean Sea where hurricanes may occur several times a year. Since its construction in 1972, Fort Bay harbour has experienced several hurricanes. Unfortunately some of these hurricanes were responsible for damage to the harbour structures (mostly to the breakwaters). The damages caused by the most recent hurricane Lenny are still present. To improve this situation, local authorities of Saba have commissioned CEC (subsidiary company of Witteveen+ Bos) to produce a plan focused on a full restoration of the original harbour facilities in combination with an economically feasible protection against hurricane conditions. A basic element in this restoration plan is to identify what has caused the apparent damage to the Fort Bay harbour structures. The first part of the present study is meant to contribute to such an identification. From an overview of the history of Fort Bay harbour, an inventory is made of possible reasons why the harbour structures have not been able to withstand the conditions they have been exposed to. This analysis has a qualitative character. One of the items that have come forward in this analysis is a worsening of atmospheric and hydraulic conditions in the area around Saba. Looking at the damage caused by hurricanes that have occurred in the past few decades, there is a possibility that such adverse conditions show an increase in both frequency and intensity. Verification of this potential increase is the subject of the second (and also the last) part of the present study.

Door de jaren heen is er veel onderzoek gedaan naar golfbrekers en de stabiliteit van de 'armour layer'. Hieruit is gebleken dat de plaatsingsdichtheid van de 'armour layer' elementen een belangrijke parameter is. De doelstelling van dit onderzoek is om inzicht te verkrijgen in de invloed van de plaatsingsdichtheid op de stabiliteit van kubussen in een dubbele 'armour layer' en tetrapoden en breuksteen in een enkele 'armour layer' van een 'rubble mound' golfbreker. Er is in dit onderzoek gekozen voor het onderzoeken van deze specifieke elementen, omdat deze het meeste worden toegepast. Tevens wordt hiermee aangesloten op voorgaande onderzoeken. Omdat er al relatief veel onderzoek is gedaan naar kubussen in een enkele 'armour layer' is er voor gekozen om voor kubussen een dubbele 'armour layer' toe te passen. De experimenten werden uitgevoerd in de Sedimenttransportgoot in het Laboratorium voor Vloeistofmechanica van de Faculteit Civiele Techniek en Geowetenschappen van de Technische Universiteit Delft. In deze golfgoot werd een schaalmodel van een golfbreker geconstrueerd. De plaatsingsdichtheid werd bij kubussen en tetrapoden gevarieerd door het wijzigen van de volumieke porositeit van de 'armour layer' en bij breuksteen door het wijzigen van de laagdikte. Bij breuksteen werd bovendien de taludhelling gevarieerd en de gradering. Na het aanbrengen van de 'armour layer' werd een onregelmatig golfveld van 1000 golven op de golfbreker losgelaten met een bepaalde significante golfhoogte. Hierbij werd gebruik gemaakt van een JONSWAPspectrum. De significante golfhoogte werd telkens opgevoerd totdat de constructie bezweek of de golfmachine de maximale op te wekken golfhoogte had bereikt. Kenmerkend faalmechanisme bij alle elementen is het 'rocken' van een element, dat uiteindelijk leidt tot het wegspoelen ervan. Onder 'rocken' wordt verstaan het bewegen van een element zonder van positie te veranderen. Dit verschijnsel vindt plaats rond de waterlijn. De toegepaste plaatsingsdichtheden bij kubussen blijken alle stabielere constructies op te leveren dan bij een in de praktijk toegepaste plaatsingsdichtheid. Hieronder wordt de plaatsingsdichtheid verstaan, welke in prototype golfbrekers wordt toegepast. Het blijkt echter dat bij een toename van de plaatsingsdichtheid de 'armour layer' zich steeds meer gaat gedragen als een zetsteenbekleding. De stabiliteit neemt als gevolg hiervan af bij toenemende plaatsingsdichtheid. Typerende faalmechanismen van een bekleding als afschuiven en oplichten beginnen dan op te treden in het schaalmodel. Berekeningen lijken aan te tonen dat de faalmechanismen in het model overeenkomen met de werkelijkheid. Tetrapoden leveren bij verhoging van de plaatsingsdichtheid steeds stabielere constructies op. Desondanks lijken ze ongeschikt voor gebruik in een enkele 'armour layer', omdat door de vorm van de elementen het filter al aangetast kan worden zonder dat er elementen zijn verdwenen. AIs gevolg van de haakweerstand is er een rotatie van een element nodig om dit te verwijderen. Met behulp van een rekenmethode is de hiervoor benodigde belasting versus de sterkte bepaald. Het blijkt dat de stabiliteit toeneemt bij toename van de plaatsingsdichtheid. Bovendien volgt uit de rekenmethode dat de elementen zich in de werkeIijkheid op dezelfde wijze zullen gedragen als in het schaalmodeL De laagste plaatsingsdichtheid wordt gekenmerkt door een progressief bezwijkgedrag. De meeste schade veroorzakende 'collapsing' golven blijken dan minder vaak op te treden. Kenmerkend voor breuksteen is de opstuwing van elementen onder de waterIijn als gevolg van 'collapsing' golven met als resuItaat een ruimere pakking rond de waterIijn. Breuksteen met een wijde gradering blijkt minder stabiel dan breuksteen met een nauwe gradering.

The main goal of this study is to determe the relation between very oblique wave attack and overtopping, and to accordingly adjust the formulae for oblique wave attack. The required knowledge to be able to read and understand this report is of a Bachelor in civil engineering level. All around the world different types of structures are built to protect adjacent areas from river or coastal flooding during high water levels. Only limited research is available on the influence of oblique wave attack (for angles over 45 degrees) on wave overtopping. Hydralab is an EU-project, which gives researchers in the European Union the possibility to carry out research in large hydraulic facilities. Cornerdike is a part of the Hydralab IV program. The Cornerdike research project was performed at the shallow-water basin at DHI in Hørsholm, Denmark. To achieve the goal of this research, tests, data processing and analysis were done.

Along the majority of the worlds shoreline, tidal inlet systems represent a common morphological feature. Like in the Wadden Sea, which forms one of the major intertidal areas on the Earth, they are found along barrier islands coasts and they play a significant role in the sediment budget of the coastal zone. Tidal inlets are highly dynamic systems that evolve under a constant interaction of forcing and morphological adjustment. In order to model and predict their long-term morphological evolution, the analysis is carried out at high level of aggregation. In this aggregated scale perspective, three morphological elements can be distinguished within a tidal inlet system, namely the ebb-tidal delta, the channel and the flat. Field observations reveal that a relationship exists between the elements state (viz. wet/dry volume) and the hydrodynamic conditions (tidal prism). ASMITA (Aggregated Scale Morphological interaction between a Tidal inlet and the Adjacent coast) concept is built on the existence of an equilibrium state. This behaviour oriented model, describes the evolution of tidal inlet systems towards the equilibrium in terms of exchange of sediment, which depends on the need and the availability of sediment. In the present study, ASMITA is used to simulate the long-term morphological evolution of tidal systems in response to changes in basin area. The size and the shape of the basin area plays an important role in the morphological development of tidal inlet systems as it determines largely the propagation of the tidal wave and, hence, it influences the tide-residual sediment transport. In the original formulation of ASMITA the basin area is considered time-invariant and therefore acting as a fixed morphometric condition on the morphological development of tidal inlet system. To evaluate the influence of a temporal change in basin area, the model implementation has been extended with the area varying as function of time. Three different scenarios are chosen in this report in order to assess the morphological evolution of tidal inlet systems: -asymptotic increase/decrease of basin area -periodic area change -abrupt change Since the basin area is the sum of the channel and the flat area, the change in the area can be ascribed to a combination of relative change in the flat area and in the channel area. Only two possible combinations are considered in the present study: an immediate response of the channel area (Ac/Af=const.), and no response of the channel area (Ac=const.). The analysis of the long-term morphological response to changes in basin areas is carried out on two adjacent basins of the Dutch Wadden Sea, viz. Vlie and Borndiep. The two basins respond to the required characteristics for this study, as they have wide different initial size of the basin area, and as their intertidal area has a rather different extension. This provides to draw insight into the dependence of the morphological behaviour on the size of the basin and on the influence of the channel area. The morphological evolution of Vlie and Borndiep is then simulated in response to the defined scenarios. The tidal system are seen to follow the imposed disturbance even in the case of a sudden increase of the basin area with 50% A sensitivity analysis on the system time scale is carried out on the basis of the analysis of the morphological behaviour of the systems under abrupt changes of the area. From this analysis, the time-scale appears to be influenced mainly by the size of the basin (the bigger being the slower), and by the imposed disturbance. The channel area was observed to play a significant role only on the response of Vlie, whereas Borndiep was observed to be flat dominated.

Many practical simulation and prediction of coastal morphology involves so-called process-based modelling. This type of modelling is built around quantitative knowledge and understanding of physical processes that act on time-scales of seconds to days and on length-scales of meters to kilometres. Present day coastal zone management is supported intensely by process-based modelling, but it requires modelling tools for larger scales as well. This need may be satisfied by fairly recently developed behaviour-oriented modelling techniques, which combine mathematical extrapolation of observed behaviour with empiricism and qualitative insight into physics. One example of a behaviour-oriented approach is the model for cross-shore profile evolution developed by Niedoroda et al (1995). This approach is based on the assumption that cross-shore profile evolution revolves towards or around an equilibrium shape that is determined basically by the mean sea level, local hydrodynamics and sediment properties. Field observations indicate that cross-shore profiles of the central part of the Dutch coast exhibit on the long run a tendency towards an equilibrium shape. This means that at least in principle, the model presented by Niedoroda (1995) should be applicable to the central Dutch coast and that it can be used to predict this coast's long-term evolution. This requires that the information needed to complete the empirical basis of the model can be distilled effectively and accurately from available field observations. A preliminary assessment of whether this is feasible has been carried out in the present study. Prompted by availability of field data, this assessment has been focused on the upper shoreface of the central Dutch coast, extending from the beach to about 800 m seaward of the shoreline. It is not evident beforehand that at this distance from the shoreline, the character of the long-term net sediment transport complied with what has been assumed in formulating the applied model. As the results of the present study are not conclusive in this respect, it is recommended (for future research) to consider also field observations that reach further seaward and evaluate whether this leads to a better model performance. Inherent to behaviour-oriented large-scale morphological modelling of the cross-shore profile is that relatively small-scale features in bottom topography are disregarded. In view of this, we have used in the present study a rather smooth curve as a schematisation of the cross-shore profile. This curve reflects the main features of the shape of the profile, but not all the details. During the study, it appeared that the applied mathematical formulation of this schematisation was not chosen very sensibly, as it hampered proper estimation of model coefficients more than expected. In this respect, there is room for improvement. The above two recommendations form the main results of the present study. Actually, these recommendations should be followed in some way before any statement can be made on the significance of the considered model with respect to simulating and predicting the large-scale evolution of the central Dutch coast.

Weir is the construction widely used in hydraulic engineering. It is very important to investigate the behaviors of the flows over a weir. In general when water streams over a weir it behaves various flow patterns according to different flow conditions. Different flow patterns results in different inference on the water level profile and the distribution of recirculation zones at downstream of the weir. The simulation of these flows is of general practical interest to the design of hydraulic structures and the management of water resources. In this report, a view of how to simulation hydraulic jump over a weir is presented, from 1-D model, 2DV hydrostatic model, 2DV non-hydrostatic model using pressure gradients as unknowns, 2DV non-hydrostatic model using pressures as unknowns, to 2DV implicit non-hydrostatic model. A 2DV implicit non-hydrostatic numerical scheme is presented, which can simulate flows with steep water and bed level gradients. The numerical algorithm solve the Reynolds equations and The integrated continuity equation simultaneously, so that the water surface level is integrated into the system, and solved together with the pressure fields. The resulting algorithm is locally and globally mass conservative. Several numerical experiments illustrate the potential of the model, namely: the simulation of the water level and velocity fields of free, undular and submerged hydraulic jumps downstream of a weir. This model is proved to fairly accurately represent discontinuities in bottom topography and water surface profiles. The numerical model also has the ability to describe different flow regimes downstream of a weir, namely free flow, undulation, and fully submerged flow. The results from the numerical model show a fair agreement with the experimental data. The implicit non-hydrostatic model, provides correct wave heights, wave lengths, and predicts the upper and lower limit for the occurrence of undulations in a good manner.

The wave growth experiment in the Australian Lake George (Young and Verhagen, 1996a) is the first multiple-station depth-limited wave growth experiment and the dataset is probably the best that is available. The lake has a horizontal flat bottom with a depth of about 2 meters and is orientated north-south. There are however some discrepancies in the wave growth data that were observed. The development of the waves differed significantly between northern- and southern-wind cases and to a lesser extent between day and night. In addition, the significant wave height decreases with an increasing fetch after a certain distance. These anomalies may have a significant influence on the coefficients of the wave growth expressions that were determined by Young and Verhagen (1996a). Therefore, the objective of the present study is to determine the cause of these anomalies and to investigate their influence on the wave growth expressions. Simulations with the SWAN wave model, in a version that uses the RIAM technique to solve the quadruplet wave-wave interactions show that the differences in the wave growth between northern and southern are caused by the lateral coastline over the first half of the lake. The observed wave growth during northern-wind is very much comparable to the idealized situation of wave growth in a one-dimensional situation with a straight coastline perpendicular to the wind direction. In southern-wind conditions, the wave growth over the first half of the lake is significantly slower. In addition, the recorded spectra in the first stations during southern-wind are anomalous. It was found that the decrease of the wave height in the second part of the lake is greater during northern-wind than during southern-wind. The decrease during northern-wind is much stronger during the night than during the day. The cause for this decrease of the wave height had not been found in the present study. There are however some indications that the shape of the lateral coastline are (at least partly) responsible, but that whitecapping and quadruplet wave-wave interactions mask this behavior. There may also be some secondary influences of atmospheric stability (stronger decrease in unstable conditions). The shape and location of the coastline in Lake George have a strong influence on the directional properties of the two-dimensional wave spectra. The wave model shows two peaks in the directional wave spectra at some measurement stations and in case of slanting wind conditions, the model shows that the waves tend to align to the main direction of the lake, rather than to the wind direction. New coefficients for the wave growth expressions are proposed here, based on the northern-wind cases as these cases seem to be fairly free from the influence of the lateral coastline. In addition, the influence of the decrease in the significant wave height is ignored explicitly

Het sluizencomplex Vlissingen is opgebouwd uit stalen damwandconstructies. In de afgelopen 45 jaar is er minimaal onderhoud gepleegd aan deze constructies. De provincie Zeeland was benieuwd naar de huidige staat en de te verwachten restlevensduur van het complex. Witteveen+Bos heeft vervolgens een uitgebreid onderzoek uitgevoerd, waarbij een groot aantal metingen van staaldiktes en waterstanden zijn gedaan. Met de verworven datasets is de restlevensduur bepaald. Aanleiding voor dit afstudeeronderzoek is de vraag of het mogelijk is met dezelfde gegevens een volledig probabilistische berekening te maken en of een dergelijke berekening zal leiden tot andere inzichten in de restlevensduur. Op basis van de staaldiktemetingen is een, fysisch verklaarbare, corrosiezonering opgesteld. Aangenomen is dat er in iedere zone een homogeen, gelijkmatig corrosieproces optreedt met een natuurlijke spreiding. De mate van spreiding is gebaseerd op de metingen. Bepalend voor de grootte van het buigend moment zijn vooral de grondparameters phi en c, het bodemniveau voor de wand en de waterstandsverschillen. De onzekerheid omtrent de waarde van deze parameters is in de berekening meegenomen als een spreiding rond het buigend moment. In dit afstudeeronderzoek zijn twee modellen opgesteld. Het eerste model berekent per jaar de kans dat de wand bezwijkt door toedoen van het buigend moment. Het model verondersteld een lineaire afname van de staaldikte als gevolg van corrosie, maar bovendien een Iineaire toename van de mate van onzekerheid omtrent de corrosie. Het buigend moment wordt opgenomen door een systeem van samenwerkende damwandprofielen. Het tweede model berekent per jaar de kans op verlies van de kerende functie door het ontstaan van gaten in de wand. Het model verondersteld een constante groei van een corrosieput. De verdeling van de maximale corrosie wordt benaderd met een extreme waarde verdeling voor maxima van de gelijkmatige corrosie. Conclusie is dat een probabilistische berekening mogelijk is en dat de resultaten duidelijk afwijken van een traditionele berekening. Nader onderzoek zou zich moeten richten op het aantal meewerkende damwandprofielen, de correlatieafstand van corrosie en het verdisconteren van reeds bewezen sterkte in de rekenwaarde van de grondparameters.

The North Sea is a shallow sea on the Eurasian continental shelf. This study focuses on the temporal development of the tidal range in the southern part of the North Sea. Records of annual tidal range data from gauging stations along the Dutch coast show in general an increasing trend perturbed by random fluctuations. Changes in tidal ranges are caused by natural (periodic) processes and anthropogenic effects. To examine the impact of human measures on the tidal range, the natural components are separated from the recorded tidal range. The only natural cycle significantly present in annual mean tidal range records is the nodal tide with a period of 18.6 yr and amplitudes of 0.2-2.0%. The short-term (few years) fluctuations are qualitatively similar for different stations with individual peaks occurring at the same time. This indicates that the noisy signal is caused by regional processes and not by measurement errors (as is not expected using annual mean values). The residual tidal range shows that apart from noise the tidal range remained constant form the early 19th century till circa 1955. During the period 1955-1980 a gradual increase in tidal range is observed at all stations. Although differences exist between the stations, their trends are very similar. Because the short-term and the long-term developments are similar, it is meaningful to construct an artificial average of the tidal range records from different stations. In this study the average of the Dutch stations and the average of the German stations are compared. The analysis shows that a similar gradually increasing trend is observed at the Dutch and German coast. The hypothesis that this trend is caused by coastal engineering in the River Rhine delta, is tested. A conceptual model is applied in which the North Sea is schematised to a rectangular basin. Estuaries with tidal prisms corresponding to Zeeland estuaries are included in this model. The model shows that the tidal range increases at the mouth of the estuary when it is closed. This increase decays along the Dutch coast with a typical length with an order of magnitude of 150 km. The results of the conceptual model are supported by a detailed model study incorporating the shape of the coast line and the bathymetry [LANGENDOEN, E. J. (1987) Onderzoek naar de vergroting van het tijverschil te Vlissingen. Faculteit der Civiele Techniek. Delft, TU Delft]. Both analyses suggest strong evidence that the tidal range is not significantly affected north of Den Helder after a closure of an estuary in the Zeeland delta. This implies that the observed trend at the Dutch and German coast does not have as common cause coastal engineering in the River Rhine delta. A satisfactory explanation for the trend since 1955 is not given in this report. However, our results suggest that the most likely cause is complex changes in the oceanic and the shelf sea system due to meteorological and astronomic changes. Analyses of tidal spectra based on hourly observations can give more insight into the processes involved.

Eerdere onderzoeken naar de bodembewegingen van de diepe vooroever van de Hollandse kust hebben aangetoond, dat er zodanige zandverliezen optreden, dat er sprake is van versteiling. Versteiling is het fenomeen, waarbij het profiel zich niet gedraagt als een vormvast evenwichtsprofiel, maar zich ontwikkelt naar een steiler profiel. Dit kenmerkt zich voor de diepe vooroever van de Hollandse kust in dieptelijnen die zich richting de kust begeven, waarbij de dieper gelegen dieptelijnen sneller verschuiven dan de minder diep gelegen dieptelijnen. Voor het onderzoek is er gebruik gemaakt van de doorlodingsgegevens afkomstig van het Rijksinstituut voor Kust en Zee. Deze basisgegevens zijn als kilometer raai beschikbaar voor 8 meetjaren tussen '65 en '97. Allereerst zijn 118 raaien (van Den Helder tot Hoek van Holland), waar tot 3000 meter uit de kust doorlodingen zijn verricht, beschouwd (zie figuur 1.1). Deze doorlodingen beslaan het meest kustwaarts gelegen gedeelte van de diepe vooroever, die loopt van de NAP-8m tot de NAP-20m. Het onderzoek spitst zich vooral toe op de bewegingen van de NAP-8m, NAP-lOm en NAP-l2m dieptelijnen. Eerst wordt er begonnen met het ordenen van de gegevens. Vervolgens worden deze geanalyseerd. Deze analyse gebeurt met behulp van de kleinste kwadraten-methode. Er wordt van uit gegaan dat de ontwikkeling van de diepte van een bepaald punt van de diepe vooroever, kan worden omschreven door een lineaire trendlijn. Per raai wordt er geprobeerd, door middel van het fitten van een rechte lijn door de maximaal 8 geregistreerde diepten van een bepaald punt, de bodembeweging van dat punt, gelegen rond een bepaalde dieptelijn, te beschrijven. De hellingshoek van deze lijn, de trend, geeft de morfologische eigenschappen van het punt weer. Einddoel van dit onderzoek is, om de betrouwbaarheidsintervallen van de gevonden trends aan te geven, zodat de zekerheid van een bepaalde trend bekend is of zodat men weet wanneer een bepaalde zekerheid bereikt gaat worden. Een hogere zekerheid omtrent deze trend is nuttig, om zo afdoende maatregelen te kunnen nemen in het kader van het beleid van 'dynamisch handhaven'. Met het bepalen van de trends en de standaardafwijkingen van de trends is de basis gelegd voor de rest van het onderzoek. Hiema wordt namelijk de afname van de afwijkingen ten opzichte van de trendlijn per meetjaar getoetst. De verwachting is, dat de afwijkingen af zullen nemen met het voortschrijden van de meettechniek in de tijd. Vervolgens is er onderzocht, of het nuttig is de geanalyseerde meetpunten te corrigeren naar de gemiddelen van een hele reeks doorlodingspunten in een strook van 200 meter rond een dieptelijn. Dit zal een afvlakkend effect kunnen hebben op eventuele aanwezige uitschieters.

Barrier island coasts are a common feature in many parts of the world. An example is the Wadden coast of The Netherlands, Germany and Denmark. These coasts consist of barrier islands separated by tidal inlets with at the landward side tidal basins.Characteristic for the Wadden Sea is that the tidal basins are not completely separated,but are connected via topographic highs allowing exchange of water between the basins. As a result the tidal inlets that connect the basins to the North Sea will interact. The focus in this thesis is on the effect of this interaction on the cross-sectional equilibrium and stability of tidal inlets that are part of a double inlet system. The knowledge gained in this study will help to develop rational management plans for this kind of system. In determining the equilibrium values and stability of cross-sectional areas of the inlets use is made of flow diagrams. A flow diagram consists of the equilibrium flow curves of each inlet and a flow field showing the adaptation of the inlet cross-sections after the system has been removed from equilibrium. Each intersection of the equilibrium flow curves represents a stable or unstable equilibrium. The equilibrium flow curve for each inlet is the locus of the values of the cross-sectional areas for which the velocity amplitude in the inlet equals the equilibrium velocity i.e. approximately 1 m/s according to ESCOFFIER [1940]. As a start the double inlet system is schematized as a basin connected to the ocean by two channels. The water surface area of the basin is assumed constant and water levels are assumed to fluctuate uniformly. On the seaward side a simple harmonic, semidiurnal tide is used to force the system. Analyzing the double inlet system under these conditions by means of the flow diagrams leads to the conclusion that a stable equilibrium of the two inlets does not exist. Ultimately only one inlet remains open and the other will close. This confirms the earlier conclusions of VAN DE KREEKE [1990] and BORSJE [2003] concerning the cross-sectional stability of multiple inlet systems.

Part I: On the time scales of wave processes. To systematically improve the SWAN model a study on the wave physics in a tidal inlet was carried out. The third-generation SWAN model was used to compute the wave processes in a tidal inlet for storm conditions. The computed wave processes are propagation (shoaling, refraction and frequency shifting), generation (wind input), non-linear wave-wave interactions (quadruplet wave-wave interactions and triad wave-wave interactions), dissipation (white capping, depth induced breaking and bottom friction), and the work done by the currents against the radiation stresses. The results were normalised, which resulted in the time scales of all wave processes. The time scales were of the order 100s – 1,000s, except for the work done by the currents against the radiation stresses, which is of the order of 1,000s – 10,000s. Part II: Depth-induced breaking: A comparison of the performance of three models. Depth-induced breaking is a subject that has been widely studied, resulting in many scalings on the Battjes and Janssen model. The Battjes and Janssen model, the biphase scaling and the Nelson scaling were selected to compare results in terms of significant wave height. The parameter of interest is the model coefficient . The models were tested with the SWAN model on three different test cases; two reef cases and one sloping bottom profile. The wave period appeared to have a strong influence on the prediction of the significant wave height, in particular on the biphase scaling. The best model over the three test cases statistically is the Nelson scaling.

This study focuses on the consequences of sea level rise on the tidal inlet of Norderneyer Seegat, which is located in the East Frisan Wadden Sea. The Norderneyer Seegat is located between the islands of Juist and Norderney in the North and the East Frisian mainland coast in the South. The Wadden Sea landscape is mainly shaped by the tides. The tides constantly transport huge amounts of water and within sediments, which are gradually deposited, forming both sublitoral and intertidal shoals. The shoals performing intertidal flats are only visible during low tide. At low tide, the water recedes in narrow channels. These tidal channels work as a distribution system for water and sediment. The volumes of channels (water) and flats (sediment) are assumed to tend to a dynamically equilibrium state. A rising sea level disturbs this equilibrium. Due to the sediment import into the basin, the flats are continuously growing following the sea level rise. For most of the tidal basins of the Wadden Sea, the net amount of sediment transport into the basin is adequate to compensate the effects of the present rate of sea level rise (1,5 mm/year). If this would not be the case, the whole landscape of the Wadden Sea would change. This would have serious consequences for the safety of the coastline against the sea, because the intertidal flats effects a significant attenuation on incoming waves. To investigate if the system is capable to adapt to the changes with a sea level rise being significant accelerated compared to present conditions, the numerical model ASMITA (Aggregated Scale Morphological Interaction between a Tidal inlet and the Adjacent coast, Stive and Wang, 1996) is applied. The ASMITA modeling concept is based on empirical equilibrium relations between intertidal flats, tidal channels and the ebb-tidal delta performing the morphodynamic elements of the Wadden Sea area. The empirical equations implemented in ASMITA contain of empirical parameters. These parameters depend on regional properties. A part of the study is spent to the determination of these empirical parameters for the Norderneyer Seegat. To determine these parameters, topographic and hydrodynamic datasets are used provided by the Coastal Research Station on the East Frisian Island of Norderney (Germany). After calibrating the ASMITA model it is possible to calculate the development of the intertidal flats and the channels of the Norderneyer Seegat, due to an observed averaged sea level rise of about 1,5 mm/year. The calculations are limited to the volumes of the elements of intertidal flats and tidal channels. Using reconstructions of historical morphological states of this area for the years 1650, 1750 and 1860, which have been developed at the Coastal Research Station, the results of the ASMITA model, are validated. After reproducing the trends of the evolution in this area over the past 350 years, predictions can be made about the consequences of scenarios with an accelerated sea level rise. This aims to contribute to an estimate of the consequences of global climate change or land subsidence. At the end of the study, conclusions are drawn, about the consequences of a increase in sea level rise for the tidal inlet of Norderneyer Seegat. Therefore, different scenarios of sea level rise are simulated. Besides this, data analysis and modeling long-term developments of large-scale morphologies is discussed. The report is finalized with some recommendations and aspects to be studied in future.