The tidal channels in the Eastern Scheldt basin, are out of equilibrium due to the reduced tidal prism as a consequence of the construction of the Storm Surge Barrier in 1986. An estimated 500 million cubic meters of sediment is required in order to reduce the cross-sectional areas of the tidal channels such that the system reaches a new equilibrium. This phenomenon is referred to as sediment starvation. The sediment starvation has been causing severe erosion of the intertidal areas which are the only available sources of sediment to feed the tidal channels because the storm surge barrier practically blocks sediment import into the estuary. The intertidal areas form the habitats for the benthic commu- nity, foraging ground for wader birds, and rest area for aquatic animals. In addition to their ecological value, the intertidal areas are valuable wave dampers and therefore important for flood protection of the hinterland. Their erosion thus harms the ecosystems as well as the flood safety of the hinterland. Mitigation measures have been carried out in the form of directly nourishing the intertidal areas (Roggen- plaat, Galgenplaat, and Oesterdam). These nourishments have had detrimental effects on the ecology that remained for a period of 5 years after the implementation. Nourishing the channels, hence reduc- ing the cross-sectional area of the channels, can feed the intertidal areas gradually, thus preserving or increasing the ecological value of the intertidal area. Nourishing the channels can succeed according to the theory on channel-shoal interaction and the experience from the Western Scheldt; however, this has not been studied yet for the Eastern Scheldt. In this study, the effects of a nourishment in a tidal channel have been evaluated for different nourishing methods, volumes and locations in the Eastern Scheldt Estuary. The objective of this research is to answer the following research question: Is a tidal channel nourishment in the Eastern Scheldt a feasible way of supplying the channel’s surrounding intertidal areas? To answer this question, we applied a 2DH numerical model (ScalOost) that runs in the Delft 3D soft- ware. For this research, the forcing consists out of tidal elevations as well as a wind climate. For reasons of simplicity and to limit larger computational time, wind waves are excluded from the model’s forcing. The numerical model is capable of simulating the hydrodynamic effects and the morphody- namic evolution of a tidal channel nourishment. For four channels, the effect of nourishing on the velocity magnitude is studied for different ways of nourishing (elevating or narrowing the channel). The model results show that the considered nourishments cause a local increase of the velocity magnitude and an additional flow on the surrounding intertidal area during flood. According to the analyses of the computed hydrodynamics, the Krabbenkreek and the Brabantsche Vaarwater channels show the most potential considering the velocity magnitude increases and velocity direction changes. There- fore, these two cases were analysed separately in form of two case studies with an in-depth hydro- and morphodynamic analysis for various nourishment designs. For the Krabbenkreek, a nourishment of 2 million cubic meters increases the maximal flow velocities in the order of 0.15 m/s, such that the critical velocity for sand transport (0.45 m/s) was exceeded over a larger part of the channel; to approximately 750 meters further landwards. The period in which the critical velocity is exceeded, increased by 15 to 60 minutes per tidal cycle. The results of the morphodynamic simulations indicate that 2.5% of the initial nourishment erodes over the first year, of which 80% settles above the MLW-line. Bearing in mind the model’s limitations, it is concluded that a tidal channel nourishment in the Krabbenkreek feeds the intertidal area at a slow pace such that the ecology is not adversely affected. The Brabantsche Vaarwater and its two main bends were used to study the effect of secondary flow on sediment transport and eventually on the behavior of a nourishment. Historic data, as well as theoretical analysis, indicate that in both bends, the centrifugal effect is dominant over the Coriolis effect for gen- erating secondary flow. Model results confirmed this observation, yet the dominance of the centrifugal effect is larger in the second bend. As outer bends tend to erode and inner bends to accrete, the outer bends were nourished (750 & 920 ∗ 103 cubic meters) in order to use the secondary flow to transport sediment towards the inner bend and eventually onto the intertidal area. The simulation results show that for both bends, 3% of the initial nourishment erodes after the first year of which 80% accreted on both the inner and outer bend. The morphodynamic simulation results do not confirm the dominance of the centrifugal forces on sediment transport, as larger accretion rates than those simulated on the inner bends were expected. Although the results were not as expected, the nourishments did increase the velocities which increased the suspended sediment concentration in the channel and as simulation results show, sedimentation in sheltered areas. A tidal channel nourishment in the Eastern Scheldt has been proven to be a potentially successful way of indirectly nourishing the channel’s surrounding intertidal areas. However, the accretion rates were predicted in the order of 2% per year, whereas this would be 100% if directly nourished. Furthermore, the impact of a tidal channel nourishment on the sediment starvation in the whole basin is small con- sidering the proposed volumes in this research only represent 0.4% of the actual sediment demand. Nourishing a tidal channel should be considered in view of maintaining ecological values.

The lower Ems river suffers from hyper-turbid conditions. These conditions are caused by channel deepening over the last 50 years, resulting in an asymmetrical tidal wave. This asymmetry has resulted in an increased
import of sediment into the Ems river. Recently some effort has gone into determining whether or not the local tidal barrier (Emssperrwerk) can be used to alter the asymmetry of the tidal waves propagating through the Ems estuary. Previous modelling studies, using state-of-the-art models, have been able to reproduce prototype tests involving the same tidal barrier but very little effort has thus far gone into determining what the optimal barrier control regime is and what the restriction imposed on the barrier operation mean for the overall
effectiveness of the barrier. The operation of the tidal barrier was schematised and described using two factors: closure percentage and closure duration. The effectiveness of a broad spectrum of combinations determining the tidal barrier operation is modelled using a simple one-dimensional model which takes only into account the (simplified) hydrodynamics in the lower Ems river. The results of the model indicate that only in part of the Lower Ems the tide can be adjusted to become symmetrical or slightly ebb-dominant. This requires a closure duration longer than approximately 240 minutes. The length of this stretch of river is increase further by increasing the closure percentage. Similarly, increasing the closure percentage also leads to a decrease in the tidal volume and the amplitude of the M4 component. For this reason, the closure percentage should be kept as low as possible, as long as the barrier operation is able to reduce the sediment import into the Lower Ems. The required length of the stretch of the Lower Ems with a symmetric tide is estimated to be around 12 km. Applying restrictions to the barrier operations showed that shorter barrier
operations should be preferred, since short operations allow a larger number of
tidal waves to be altered, increasing the effectiveness in a realistic setting. Based on these considerations an optimal barrier operation consists of a closure duration of approximately 300 minutes and a closure percentage of approximately 60%. The results showed that the method used for evaluating the barrier operation is unable to distinguish between water levels signals consisting of altered and unaltered waves. The effectiveness of the barrier operation is
still estimated by considering the whole water level signal. The impact of the barrier operation in the model interfered with the seaward model boundary. This error increases in magnitude with increasing closure percentages. Making the results for those combinations unreliable. In order to make more reliable conclusions about the effect of the tidal barrier operation, subsequent models should encompass a larger domain and include a more detailed schematisation of the channel geometry, river discharge and the tidal barrier itself.

In Chile, the Biobío river separates the cities of Concepción and San Pedro de la Paz. Bridges crossing the Biobío river ensure a fast and dependable connection, which contributes to the transport options in the region. With the Biobío region being the second largest contributor to the country's GDP, an unreliable transport network is highly undesirable. However, this is exactly what happened since 2016. Some of the bridges crossing the river collapsed, excessive local pier scour near the foundation and negative effects of morphological dynamics were deemed to be one of the causes. Furthermore, Chile is prone to earthquakes and the resulting tsunamis, which can also damage the structural integrity of the bridge. The Chilean Railroad Agency (EFE) wants to realise a new railroad bridge crossing the Biobío river in Concepción, replacing the existing century old railway bridge. To prevent the failure of the new railway bridge, which can result in unnecessary economic damages, the morphological influence and damages due to scour, earthquakes and tsunamis, must be thoroughly understood and modelled. This process of modelling the current and future situations of the Biobío river is part of this project, using Delft3D-FLOW and NeoWave as modelling agents. With the outcomes the programme of requirements and the preliminary design for the bridge are updated and presented.

Vietnam is one of the five countries that is severely affected by the consequences of climate change. The extreme weather conditions and the increase of the sea level results in floods in the Mekong Delta, located in the South of Vietnam. Can Tho city, found in the heart of the Mekong Delta, is one of the cities that copes with water related issues on a regular basis. To be prepared for the future, the environmental and infrastructural issues need to be tackled. The resiliency of Can Tho got included of the World Bank program. The objective of this project of the World Bank is to reduce the flood risk in the urban core area and to improve connectivity between the city centre and the low risk urban growth areas. The structural solutions of the polder will be sluice gates, tidal sluice gates, the construction of river embankment, rehabilitation of the drainage system and constructing two regulation and water retention lakes. Additionally, building dykes with new roads and expanding or building new bridges will increase the connectivity of the city. All these measures will contribute on the resiliency of the city. The aim of this report is to identify the impact of the polder on the city, considering the infrastructural and the hydraulic aspects. To measure the impact, the current situation is simulated into two models, an infrastructure model and a hydraulic model. The results of hydraulic model show whether and when locations are flooded, whereas the aim of the infrastructure model is to identify flows on the network, the connectivity of the city and the flow changes after implementation of the new roads.

During construction of breakwaters, adverse weather conditions can result in damage, in the form of reshaping and loss of material to the open work fronts of the structure. Based on literature research, analysis of work methods, analysis of damage to older breakwater projects and interviews, it was deduced that during construction, the open work fronts of the submerged core section, emerged core section and underlayer section are in particular prone to the following damage mechanisms: - Reshaping of the submerged core due to head-on and oblique wave attack - Reshaping of the emerged core due to head-on and oblique wave attack - Reshaping of the underlayer due to head-on and oblique wave attack. - Mixing of rock material of different sections. - Overwash of dislocated material. When a damage event occurs, construction is delayed as repair works are needed. This delay increases the probability of encountering unfavourable conditions in the remaining construction time. Such positive feedback complicates any quantitative risk assessment. The main objective of this thesis was to investigate the feasibility of a computational model with which risks related to the construction phase of rubble mound breakwaters in sea-state conditions can be assessed. By simulating the construction process in time with a fully probabilistic process-based model, the financial risk due to storm-induced damage during construction can be assessed. Due to the stochastic behaviour of the parameters used in the building process simulation, the simulation outcome itself is characterized by a stochastic behaviour. To calculate the financial risk, the simulation is run multiple times like a Monte Carlo simulation. Quantitative damage calculations in the model were performed using methods reported in the relevant literature. However, currently available literature did not cover all damage mechanisms or the full extent of it. For these damage mechanisms, some newly developed methods were introduced. The damage profiles predicted by these methods turned out to be in excellent agreement with data from an older breakwater project. This older breakwater project was used as a reference case to test the model and analyses its performance. Furthermore, a sensitivity analysis on the breakwater parameters showed that the nominal diameter of the core and underlayer material and the start date of construction works have the strongest sensitivity on the financial risk.

Immersed tunnel elements are prefabricated in the construction yard and then transported to the construction site to be integrated into the tunnel. During the transportation and immersion, the floating tunnel element is connected via cables to the immersion barges/pontoons. In this study, the hydrodynamical behavior of a floating tunnel element during construction has been modeled. The motional characteristics and stability of a floating tunnel element and twin barges during the installation are investigated.This study aimed to investigate, how the stability of the system can be improved to make it possible to immerse a large number of tunnel elements in relatively short span of time in offshore conditions. The hydrodynamical behavior of the system and the related forces in different construction stages are analyzed. The focus of the study was on the determination of the influence of the pontoon configuration on the systems stability, the related forces, and operability. For this study, Fehmrnbelt Fixed Link tunnel project has been taken as a case study. The calculations are performed for two different pontoon configurations, namely: - Catamaran (conventionally applied pontoon for the immersion of tunnel elements) - Semi-submersible (platform used in offshore industry)In the analysis, first, the main dimensions of the two pontoons are determined. The pontoons form the main piece of the immersion equipment. Subsequently, during the transport, the forces and moments on the floating element are evaluated. Two main type hydraulic external forces have been taken into consideration in the model, namely current and wave force. For different positions along transport route, the forces and moments are calculated for finite water depth and different values of flow velocity.From the analysis, it appears that the wave-induced motions of a floating tunnel element are negligible. The relatively small waves are not able to bring the massive tunnel element into motions. The lowest natural periods of the floating tunnel element appears for roll degree of freedom, and it is about 8s. The significant current forces and moments occur during the fitting out. The stability of a floating element during transport is primary determined by the towing velocity.During immersion, the systems stability due to waves and current forces is being analyzed. To assess the stability of the system for different current conditions, the vortex shedding periods are calculated. Then the natural frequencies of the system have been evaluated for different pontoon configurations and tunnel element length.It appears that an immersion system with Catamaran pontoons seems to be less sensitive to vortex shedding period in contrast to the Semi-submersible barge. A Semi-submersible barge can only be used in 80% of current conditions in Fehmarnbelt. A Catamaran pontoon can be applied in 95% of the occurring current conditions.Also, during the immersion, the wave-induced motions of the tunnel element can be ignored, provided that the wavelengths and wave periods are not too large. On the other hand, the relatively light pontoons are sensitive to wave loadings. The motions of the barges are prevented by the element, which leads to significant force fluctuations in suspension cables. In the analysis, the coupling between surge, sway, heave, roll, pitch and yaw degrees of freedom are considered. The calculations are performed for the first order responses that are valid in relatively low wave heights. Hydrodynamic effects caused by the nonlinearities are disregarded in the calculations.The pontoons were considered as a hybrid structure. That means, concerning the horizontal degrees of freedom the pontoon structure is regarded as it is compliant and it behaves like a floating structure. While concerning the vertical degrees of freedom, it is stiff and resembles as a fixed structure, and it is not allowed to float freely. The contribution of the mooring lines to the first order response is considered of minor importance, and it is disregarded. Numerical studies are conducted to compare the dynamical behavior of the Catamaran pontoon with that of the Semi-submersible. The results of this study reveal that:  - The contribution of the first order wave force to the pontoons motions in soft degrees (surge, sway, and yaw) is limited - The motions in stiff degrees of freedom (heave, pitch, and roll) are normative for the immersion operation. When the tunnel element is immersed in wave conditions T>5 s and H > 1 m, then there is a significant danger that one of the suspension cables will break when applying a Catamaran pontoon. If a Semi-submersible barge is used, then the tunnel element can be immersed in wave conditions T < 6.5 s and H < 1.8 m. - Semi-submersible pontoon has larger natural frequencies than Catamaran pontoon. The natural periods of the Semi-submersible barge are approximately a factor 1.4 larger than the natural periods of the Catamaran pontoon. - A Semi-submersible pontoon is more sensitive to the force fluctuation in the suspension cables than the Catamaran pontoon concerning the static stability and floating capacity. Especially the floating capacity became problematic if the force fluctuations become large and therefore the pontoon can be pulled under water. - The heave motions mainly affect the force fluctuations in suspension cables, and they can be considered as normative. - Both barges are sensitive to the increasing wave height and period. However, the effect on Catamaran pontoon is larger. In total, a Semi-submersible barge has favorable operability in the waves and current conditions in Fehmarnbelt. Therefore, if the workability is the primary objective, then it is better to apply a Semi-submersible pontoon. Then in 77% of environmental conditions, the tunnel elements can be immersed.

Een schutsluis maakt het mogelijk om schepen van het ene naar het andere waterpeil te brengen. Van belang is hierbij dat de krachten op de schepen in de sluis niet te hoog worden. Het vullen en ledigen van een schutsluis gaat gepaard met golf- en stromingsverschijnselen die krachten op schepen uitoefenen. De langskrachten mogen niet te groot worden om het bezwijken van de scheepstrossen te voorkomen. Voor het bepalen van de langskracht op een schip in een schutsluis wordt in Nederland een methode gebruikt die is gebaseerd op het onderscheiden van vijf krachtscomponenten. Deze schematisatie is opgenomen in het rekenprogramma LOCKFILL, dat in de jaren ’80 is ontwikkeld door het Waterloopkundig Laboratorium. Het gaat om de volgende krachtscomponenten:
1. kracht als gevolg van translatiegolven
2. kracht als gevolg van impulsafname
3. kracht als gevolg van wrijving
4. kracht als gevolg van straalwerking
5. kracht als gevolg van dichtheidsverschillen
De sommatie van de krachtscomponenten levert een totaalkracht op een schip.Een schutsluis maakt het mogelijk om schepen van het ene naar het andere waterpeil te brengen. Van belang is hierbij dat de krachten op de schepen in de sluis niet te hoog worden. Het vullen en ledigen van een schutsluis gaat gepaard met golf- en stromingsverschijnselen die krachten op schepen uitoefenen. De langskrachten mogen niet te groot worden om het bezwijken van de scheepstrossen te voorkomen. Voor het bepalen van de langskracht op een schip in een schutsluis wordt in Nederland een methode gebruikt die is gebaseerd op het onderscheiden van vijf krachtscomponenten. Deze schematisatie is opgenomen in het rekenprogramma LOCKFILL, dat in de jaren ’80 is ontwikkeld door het Waterloopkundig Laboratorium. Het gaat om de volgende krachtscomponenten: 1. kracht als gevolg van translatiegolven 2. kracht als gevolg van impulsafname 3. kracht als gevolg van wrijving 4. kracht als gevolg van straalwerking 5. kracht als gevolg van dichtheidsverschillen De sommatie van de krachtscomponenten levert een totaalkracht op een schip. Onsystematische waarnemingen bij echte sluizen wijzen er op dat schepen vaak in sluizen liggen zonder de trossen vast te maken. Deze schepen hebben dan geen problemen van langskrachten. Dit kan erop wijzen dat huidige rekenmethoden zoals LOCKFILL onnodig conservatief zijn. In dit onderzoek is de wiskundige modellering van LOCKFILL in kaart gebracht. Hieruit blijkt dat de krachtscomponenten als gevolg van impulsafname, wrijving en straalwerking niet onnodig conservatief zijn. Of dit ook geldt voor de krachtscomponenten als gevolg van translatiegolven en dichtheidsverschillen moet in vervolgonderzoek worden onderzocht. Verder is in dit rapport een alternatieve schematisatie ontwikkeld voor het bepalen van de krachtscomponenten als gevolg van impulsafname en wrijving. Door de toegenomen mogelijkheden van numeriek rekenen kan de langskracht nauwkeuriger bepaald worden dan in LOCKFILL. Wat dit betekent voor de ontwerppraktijkmoet middels praktijkmetingen worden gevalideerd.

Onsystematische waarnemingen bij echte sluizen wijzen er op dat schepen vaak in sluizen liggen zonder de trossen vast te maken. Deze schepen hebben dan geen problemen van langskrachten. Dit kan erop wijzen dat huidige rekenmethoden zoals LOCKFILL onnodig conservatief zijn.
In dit onderzoek is de wiskundige modellering van LOCKFILL in kaart gebracht. Hieruit blijkt dat de krachtscomponenten als gevolg van impulsafname, wrijving en straalwerking niet onnodig conservatief zijn. Of dit ook geldt voor de krachtscomponenten als gevolg van translatiegolven en dichtheidsverschillen moet in vervolgonderzoek worden onderzocht.

Verder is in dit rapport een alternatieve schematisatie ontwikkeld voor het bepalen van de krachtscomponenten als gevolg van impulsafname en wrijving. Door de toegenomen mogelijkheden van numeriek rekenen kan de langskracht nauwkeuriger bepaald worden dan in LOCKFILL. Wat dit betekent voor de ontwerppraktijkmoet middels praktijkmetingen worden gevalideerd.

The main goal of this study is to determine 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.