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In coastal engineering waves often play a dominant role. To predict the wave behaviour in coastal regions numerical wave propagation models have been developed. This study deals with the verification of two models against measurements in the field, namely HISWA and SWAN. The second generation model HISWA has already proven to perform well for both engineering and research purposes. The third generation model SWAN is a new model, still under development. Also made by Delft University of Technology, SWAN is more or less the improved sequel to HISWA. Both models are based on the action density balance, which is made stationary to reduce the required computer capacity. They simulate wave growth and decay accounting for wind input, bottom friction, depth limited wave breaking, and whitecapping. The main differences between the models are the fact that SW AN is spectral both in frequencies and in directions, whilst in HISWA the frequencies are parametric. Secondly, the numerical scheme in SWAN for the wave propagation is unconditionally stable and encompasses waves from aU directions (360°). In HISWA the directional sector wherein wave propagation is considered is limited to a maximum of 1200 to obtain stability. Furthermore - being third generation - SWAN allows the spectrum to develop without any a priori constraints. During the measuring campaign, which was carried out by the Coastal Research Station Norderney, in the winter of 1995-1996, nine Waverider buoys recorded wave data. These buoys were located in the Norderneyer Seegat, a Wadden Sea area. Two cases have been simulated with SW AN and HISWA: one during high tide and one during low tide. I varied several parameters to examine the influence on the wave heights. These variations concern wind input formulation, wind speed, nonlinear wave wave interactions, friction, breaking, whitecapping, water level and incoming wave height. With reference to these research runs a set of input parameters is composed with which the models perform best in the area of this research. Both models tum out to have a good performance indicator (>90%). It has been found that the wave heights are to a large extent determined by the wind and by breaking. The wave height of the incoming wave at the seaward boundary of the computational domain is of minor importance. In equal circumstances, SWAN tends to calculate higher wave heights than HISWA. It appeared from this study that SWAN performs slightly better than HISWA and is therefore a suitable tool for wave prediction in a Wadden Sea area.

Waves that approach the coast and encounter obstacles such as small islands, rocks or breakwaters may be reflected backwards and in lateral directions, but the wave crest may also bend around the obstacle. This phenomenon can be described with refraction-diffraction models based on the Boussinesq equation or the mild-slope equation of Berkhoff. However, these models are computationally very demanding since they require a high spatial resolution. Moreover, physical phenomena such as wind generation or depth induced breaking are not readily accounted for. Inclusion of diffraction in a spectral wave model would eliminate these drawbacks. Similar to refraction the effect of diffraction can be represented as a transport of wave energy through spectral space (in the directional domain). Two ad hoc proposals are made to include diffraction in the model SWAN, which is a fully spectral model based on the action balance equation. The first proposal to describe this diffraction-induced turning rate is derived from the mild-slope equation for monochromatic, long-crested waves. It depends on the second order spatial derivative of the wave amplitude. Adding the diffraction term made the model unstable. The second proposal to describe the diffraction-induced turning rate is based on the first-order spatial gradient of the wave field. The transport of wave energy along the wave crests is proportional to the first-order derivative of the energy along the crest. The model is tested for three different cases: the academic case of monochromatic, unidirectional waves near a semi-infinite breakwater, a realistic harbour and the Bay of Viano do Castelo (Portugal). In areas with considerable wave motion the influence of diffraction is relatively unimportant. In other regions the gradientapproach for diffraction seems to give a realistic estimate for the wave field.

HISWA is een tweedimensionaal golvenmodel, dat de gebruiker in staat stelt diverse golfgegevens, zoals significante golfhoogte, periode en golfrichting, voor een bepaald modelgebied te bepalen. Op dit moment biedt HISWA al faciliteiten om pre- en postprocessing uit te voeren (zij het in beperkte mate). Onder de gebruikers echter is er behoefte aan meer en uitgebreidere mogelijkheden. Door de functionaliteiten op het gebied van weergave en analyse van gegevens, leent een GIS (Geografisch Informatie Systeem) zich uitstekend voor pre- en post-processing doeleinden. Het doel van het project is het koppelen van HISWA aan een GIS-pakket, en wel op een dusdanige manier dat een gebruikersvriendelijke schil ontstaat, waarbinnen een HISWA berekening kan worden uitgevoerd en tevens van de functionaliteiten van het GIS-pakket gebruik kan worden gemaakt voor pre- en post-processing doeleinden. Aan de hand van de resultaten van een vragenformulier zijn de eisen en wensen van de huidige HISWA-gebruiker, met betrekking tot bovengenoemde koppeling, geïnventariseerd. Tevens zijn uit deze resultaten conclusies getrokken wat betreft de benodigde functionaliteiten van het te gebruiken GIS-pakket. Er is, voorafgaand aan het afstudeerproject, gekozen voor 's werelds meest gebruikte en veruit bekendste GIS-pakket, ARC/INFO. Uit onderzoek, uitgevoerd tijdens het afstudeerproject, blijkt, dat het pakket over vrijwel alle benodigde functionaliteiten beschikt. In ARC/INFO's macrotaai AML (ARC/INFO Macro Language) is een volledig menugestuurde applicatie ontwikkeld, genaamd HISGIS. De applicatie HISGIS bestaat uit een viertal delen, te weten het hoofdprogramma, een 'Pre-processing module', een 'Calculation module' en een 'Post-processing module'. In het hoofdprogramma kunnen de drie modules met behulp van een menu worden aangeroepen.

In the past years the SWAN wave model was developed. SWAN is a third-generation spectral wave model for applications in coastal areas. The verification of the model has been carried out for a few laboratory and field experiments. In this thesis the DELILAH field experiment held at the property of the Field Research Facility in Duck, North Carolina, was applied. The aim was to implement SWAN for DELILAH and to obtain further improvements of the SWAN model. The bathymetry with an average slope of I: 150 is characterised by a constantly changing sandbar in the near-shore area at the Field Research Facility. At 13m depth an array of wave gauges is located (SAMSON). The boundary condition was taken from the spectra obtained at this location and was uniformly applied along a straight line through this location and parallel to the beach. The research was restricted to nine crossshore gauge locations in the near-shore zone. The I-dimensional spectral- and wave heightobservations in this area were compared to the SWAN results and interpreted. The results of the tests showed that SWAN underpredicted the dissipation of wave energy and overestimated the non-linear triad wave interactions. The first discrepancy was improved by adapting the tuning parameter in the wave breaking formulation (gamma) according to Battjes & Stive. The second discrepancy was improved by adapting the tuning parameter in the Source term for the triad interactions (a(EB)) of the action balance equation. Conclusions were that a y value based on the deep-water steepness according to Battjes & Stive improved the results of the significant wave heights significantly at the gauges where wave breaking was relevant. Secondly, small improvements in the cross-spectral distribution were obtained by increasing the value of the proportionality parameter a(EB)=0.25 to a(EB) =0.5. Interesting was that the parameter of a(EB)=O.5 gave the best results for both a case with the barred bathymetry and for a case without the bar. The final results are acceptable, but further investigation of the non-linear triad interactions is advisable to improve the approximation of the cross-spectral energy distribution.

Introduction Dong Lam Cement Factory is developing a new clinker plant in Thua Thien-Hue Province, Vietnam. The clinker has to be exported towards Ho Chi Minh City, where it is grinded into cement and used for the construction industry. For the clinker production coal is needed and has to be imported. To make the in- and export possible a new dedicated seaport is required to allow for 15,000 dwt clinker vessels and 7,000 dwt coal vessels. Objective The objective is to design a port with sufficient capacity to handle the predicted cargo flow and which offers acceptable conditions for the ships to enter. The effective berth and hinterland capacity have to be determined such, that turnaround times are within limits. To create safe conditions, the vessels need to have enough space for manouevring in the wet port area. These manoeuvres can be seriously disturbed by wind, wave, currents and siltation on the long term. To ensure the workability of the port these effects have to be limited. Analysis To determine the effective berth capacity the queuing theory is applied. In phase 1 and 2 one clinker and one coal berth satisfy with effective capacities of respectively 700 and 175 t/h respectively. In phase 3 two clinker and two coal berths are needed with the same loading/unloading rates. To get insight in the environmental boundary conditions, field data is collected and analysed thoroughly. In Vietnam the wind climate is governed by the South-East Asian monsoon system, with a dominant SE direction and strong NNE winds. The wave climate is directly influenced by the wind climate and shows a similar pattern. With regard to extreme conditions, once a year a tropical storm lands in the vicinity of the port site. These storms are accompanied by strong wave conditions, coming from E to SE direction. Having frequent waves from the NNE and SE, littoral transport is generated in north- and southward direction. Nevertheless, the northward transport is clearly dominant. Currents are heading SE for most of the time. Synthesis Four different layouts are developed for phase 3 of the project. Two of them are dismissed in an early stage, because of unfavourable conditions. The other two layouts – the 'coastal' and 'offshore' alternative, are evaluated with a cost-value approach. In this approach the value of each design is assessed by means of a MCA. Evaluation The following criteria are taken into consideration: navigation, tranquillity at berth, coastal impact, sedimentation, ease of cargo handling, safety and flexibility. Regarding navigation and wind, wave and current hindrance, no significant differences are found. It turns out that the most important difference is found in the coastal impact. The coastal alternative will cause erosion along 7.5 km of coastline with a maximum retreat of 100 m. Instead, the offshore alternative affects 'only' 3 km with maximum retreat of 70 m. The other element of the cost-value approach is the costs. The investment costs for the coastal alternative are 64.1 M$, which include the dredging works, breakwater and quay construction. The costs for the offshore port amount 77.5 M$, which entails the dredging works, breakwater, jetty quay and trestle construction. The relative low costs for the coastal alternative are achieved by applying the cut-and-fill balance; the dredged sand is used as breakwater foundation. Maintenance dredging costs are 1.75 M$ and 0.9 M$ for respectively the coastal and offshore alternative. To finish the cost-value approach the value/costs ratio is taken for both port layouts. The coastal alternative (0.9) turns out to be a better port layout than the offshore alternative (0.77).

The purpose of this study is to develop a novel approach to offshore wave load analysis and apply it to the problem of ringing of gravity base structures. Ringing is a transient structural response at the natural frequency of the structure, that has been observed in model tests of gravity base structures. The observed response has relatively high frequencies compared to the dominant frequency of the wave field, indicating that non-linearity in the load process might determine its occurrence. In this study, Newman's long wave-length force-model is used for calculating the wave loads up to third order. We have re-formulated Newman's results in terms of the frequency components of the ocean surface elevation process and their Hilbert transforms. This allows us to generate response surfaces for both static and dynamic responses as functions of the spectral components of the ocean surface. As the spectral components are uncorrelated, linear processes, it is straightforward to treat the response surfaces as limit states in a FORM (first-order reliability method) type of analysis. This provides a very efficient means of calculating: - the ocean surface history most likely to generate an extreme ringing response: the designer wave for ringing; - the complicated relationship between ringing and the waves that generate ringing; and - statistics of ringing response within a sea state. We have demonstrated the capability of the method to predict ringing of a single vertical column and, thereby, to clarify the process leading to ringing. Some ringing response has been observed even by including only the second-order excitation. However, the effects of the third-order one are very significant. Omitting the thirdorder excitation leads to a large underestimate of extreme response. In particular, the third-order terms lead to an impulsive loading that excites a strong ringing response. A number of extreme responses have been calculated for different exceedance probabilities of individual maxima for sea states of different durations. The method has proved to be very efficient and straightforward.

Refraction of narrow-band surface waves in coastal areas can result in wave-focal zones where due to interference, wave statistics vary rapidly and on similar length scales as those of individual waves. However such interference patterns, or wave coherence, are not accounted for in conventional stochastic wave models that are based on the energy balance equation or radiative transfer equation. In this work we present a quasi-coherent theory, which is an extension of the radiative transfer equation and quasi-homogeneous theory. We show that this new stochastic modelling approach can resolve rapid variations in wave statistics that occur in the vicinity of a wave caustic. The results compare favourably to those obtained from ensemble averages calculated with a deterministic phase resolving model (SWASH) and, in a focal zone, constitute a significant improvement over those obtained with a conventional stochastic wave model based on an energy balance equation (SWAN).

Refraction of narrow-band surface waves in coastal areas can result in wave-focal zones where due to interference, wave statistics vary rapidly and on similar length scales as those of individual waves. However such interference patterns, or wave coherence, are not accounted for in conventional stochastic wave models that are based on the energy balance equation or radiative transfer equation. In this work we present a quasi-coherent theory, which is an extension of the radiative transfer equation and quasi-homogeneous theory. We show that this new stochastic modelling approach can resolve rapid variations in wave statistics that occur in the vicinity of a wave caustic. The results compare favourably to those obtained from ensemble averages calculated with a deterministic phase resolving model (SWASH) and, in a focal zone, constitute a significant improvement over those obtained with a conventional stochastic wave model based on an energy balance equation (SWAN).

As ocean surface waves radiate into shallow coastal areas and onto beaches, their lengths shorten, wave heights increase, and the wave shape transforms from nearsinusoidal to the characteristic saw-tooth shapes at the onset of breaking; in the ensuing breaking process the wave energy is cascaded to small-scale turbulent motions in the surf zone. This nearshore transformation of ocean waves, and the modeling thereof, is the subject of this thesis. In particular, the integral objective of the present work is to develop and verify a stochastic model for directionally spread random wave fields over topography in the nearshore.