Across the world, the presence of humans in coastal regions is always increasing. Hydraulic forcing from extreme events is a large risk around the global coastlines, the risk being complicated by the increased human presence along the coasts. The knowledge that vegetation can be used as a coastal protection measure is not something new. The benefits of vegetation have been seen throughout history and are being researched on till date. If we know to a certain confidence what the wave heights are at the shoreline, coastal defence structures, used as a hybrid protection measure, can be designed accordingly. Not much research has been done on the wave behaviour on shallow foreshores. Localised studies have been previously done on tropical vegetated coasts, but there is a lack of efficient and accurate analysis on a large scale. As we bring more clarity on how waves transform and attenuate in a typically vegetated coast, some questions get answered, and some more questions arise, which also happened during the research done for this thesis. Observed data, be it laboratory or field, is very crucial in validating numerical models. A laboratory experiment was done in the TU Delft Laboratory of Fluid Mechanics flume, for a complete vegetation-free profile, where the surface elevations were observed for different wavemaker input conditions. A lot of numerical models have been developed that predict wave transformation and dissipation through vegetated foreshores. However, these models lack validation from observed data. This thesis first focuses on understanding the wave transformation for two unique (and mainly theoretical) wave conditions: a regular sinusoidal wave and a bichromatic wave. It was checked if the transformation is reflected in the models – SWAN and SWASH, which they did. The research proceeded on to validating the models by comparing the wave heights observed in the laboratory experiment versus when the models were inputted with the same conditions, including inputting the observed data into the models. When the laboratory conditions were replicated, the SWASH results obtained correlated quite well with what was observed in the laboratory. The same was not true in the case of SWAN. When a spectral analysis was done for the observed data, a presence of very low frequencies (VLF) as well as some minor higher frequencies was noticed. To check its effect, if any, on the model results, they were filtered out. Both the original and filtered data was inputted into the models. The difference in the foreshore region was more distinct in the filtered case, i.e., making a bichromatic elevation input purer resulted in more pronounced undulations in the wave heights than what was predicted in the unfiltered data. This result does not fit well with the existing knowledge on wave dissipation processes. It is widely known that the presence of VLFs and higher frequencies are the driving mechanisms that result in the undulations in the foreshore region, but the predicted results were exactly opposite to this knowledge. What can be thought of from the anomaly is that the presence of various frequencies (that is, waves with different periods) counteract each other’s effects and make the undulating wave heights milder, but when the signal is made purely bichromatic, it leads to more distinct undulations. This proposition is also backed by the similar SWASH results for the laboratory condition-replicating theoretical inputs. This anomaly needs further investigation. Another interesting observation was that the changes happening in the offshore region did not affect the results in the foreshore region, for varying parameters in SWAN. SWASH can be concluded as a better model for predicting wave heights, especially in the foreshore region. SWAN could not predict the fluctuations in the wave heights. Obtaining the wave heights at the shoreline with SWAN, and designing a dike with those results, for example, will lead to disastrous consequences, as SWAN underestimates the wave heights. The study is limited by the consideration of hydrodynamics only, and by the many simplifications made to simulate the conditions. One of the recommendations formulated is to obtain field data and to make a similar comparison with the models to corroborate (or correct) the observations made. This study tried to see the correlation between the models and observed data in the laboratory, for simple (and somewhat purely theoretical) cases. It is, nonetheless, a starting point for more complicated cases, the basis for which can be laid on this study.

Since 2003 there is a cooperation between the Hydraulic Engineering department of Delft University of Technology and Bulgarian universities. The cooperation focusses on exchange of knowledge and the development of the coast in the area of Varna. Dutch and Bulgarian students get the possibility to gain experience in data collecting, processing and interpreting. Repeating this fieldwork every year in the same area will provide an overview of the coastal development in the Varna area. The students will act as consultants for local hotel owners at the Varna coast. Their work consists of measuring hydraulic aspects in the project area and making a rehabilitation plan for the St. Elias Marina. Data collection consist of inventory material near site, beach measurements, wave measurements, profile measurements, quarry analysis and a bathymetric survey. The rehabilitation plan contains the development of sub-areas in the St. Elias Marina like the peninsula, north beach, south beach and the breakwater.

Quidico is a small town, approximately 200 kilometer south of Concepcion. In the bay adjacent to Quidico town, a great number of local fishermen are active. In the current situation, high waves, a strong current and significant sediment transport hamper the effectiveness of the bay as fishing harbour. Also qualitative onshore facilities to support onshore activities of the fishermen, are absent. The Department of Ports of theMinistry of Public Works, developed a preliminary design proposal, to solve these problems. However, after consultation with the fishermen, this proposal was declared unsatisfactory. Therefore, an additional study is performed to develop a new integral design for the bay of Quidico. The desired design consists of onshore buildings, a paved support area, mooring facilities and breakwaters to create shelter for safe mooring of the fishing boats. Furthermore, these breakwaters shouldmitigate the problems related to sediment transport. To develop a new breakwater orientation and design, wave data is analysed. Waves coming from the south to south-west are most common, but not guiding due to the sheltering factor of IslandMocha, positioned in front of the coast. The guiding wave, which is coming from the north-west, is implemented in models of Delft3D to see what the new orientation of the breakwater should be. Based on the wave analysis, sediment transport analysis and modelling results, a new breakwater orientation is determined, that fulfills all requirements prescribed by the DoP. After defining this new orientation, the influence of the breakwater on sediment and waves is analysed. Due to the new orientation, a new design of the breakwater is made. The fishing harbour should offer the possibility for the fisherman to unload their goods and berth safely. The DoP proposed the construction of a mooring facility along the south-west shoreline of Quidico Bay. Two types of quay walls for the mooring facilities are proposed, a sheet pile wall and a concrete mass wall. For both types a preliminary design is developed, by making use of the 2D finite element software PLAXIS and hand calculations. The preferred mooring facility design mainly depends on the soil conditions at the specific location. From the boundary conditions it is concluded the bedrock is found at a depth of 60m, the soil above mainly consists of sand. Therefore the construction a sheet pile wall to serve as mooring facility, is recommended. In the initial design of the Department of Ports, six separate masonry buildings are proposed to accommodate the desired supporting facilities. These buildings cover a large area of the bay and will require a large paved supporting platform. To reduce this paved area, the DoP is interested in a more compact design, that includes all supporting facilities in one multi-storey building. In consultation with the DoP two different designs are developed; a three-storey steel building and a two-storey concrete building. A structural design is developed within the boundaries set by the functional design requirements. Next, a structural analysis is performed by making use of finite element software (ETABS) and a final design is obtained for both buildings. The concrete building is concluded to be the most suitable option for the DoP. Quick offloading of the boats and smooth transshipment of goods is hindered due to the lack of a good support area and access road. The DoP proposed a design for both pavements in the their preliminary study, but it was requested to evaluate different alternatives. Three different pavement technologies are proposed for the access road: surface treatment, asphalt and concrete slabs. For the pavement in the support area concrete slabs are the preferred solution. To achieve an optimal pavement design that fulfills all structural and serviceability requirements throughout the full design life, slab pavements with different dimensions and thicknesses are evaluated. In conclusion, short concrete slabs are the preferred pavement for both areas. Short slab pavement is an upcoming technology that has great advantages in terms of structural performance and costs.

In Sri Lanka, the government and the Liberation Tigers of Tamil Eelam waged a civil war between 1983 and 2009. During this period the social and economic development in the north and east of the country was disrupted. Due to this disruption a development opportunity for this region is the expansion of the fishery industry. In 2016, the Sri Lankan government proposed the Northern Province Sustainable Fisheries Development Project, in which the construction of a harbour at Point Pedro in the Jaffna District is included. This harbour should become the second largest fishery harbour in Sri Lanka. This report covers the design study of the Point Pedro harbour project, the goal of this study is to design a safe, economically efficient and socially accepted harbour at Point Pedro. To achieve this goal, the following research question “How can safety, economic efficiency and environmental impact be combined optimally in a harbour design for Point Pedro in the Jaffna District?” is answered. In figure XX, the final design of the harbour can be seen. This design is focused on the optimal combination between safety, economic efficiency and environmental impact. Because these criteria are conflicting, they are prioritized as follows: (1) safety, (2) economic efficiency and (3) environmental impact. Safety is provided by constructing breakwaters around the harbour, providing sheltered water conditions in the harbour basin. Also, the harbour entrance is constructed in a way that monsoon waves cannot directly intrude into the basin. Economic efficiency is accounted for by constructing the quay wall close to the central located fish processing facilities. This optimizes the supply chain, resulting in a smaller loss in the fish production (compared to the current situation). The costs are optimized by reusing all dredged material inside the breakwater or for land reclamation. Additionally, the location of the harbour entrance is minimizing the sailing routes as much as possible, without creating safety issues due to wave intrusion. Finally, the negative effects of social impact are limited by involving local fishermen and residents during the entire development process. Because these stakeholders are potential blockers of the project, it is important to include their opinions in the design. This can also be done by broadening the scope, in which touristic facilities and accommodations can be included in the project. Other negative impacts of the harbour can be either mitigated or minimized. However, because the environmental impact is determined as the least important criteria, it is not able to solve every issue. This design is considered to be the most optimal combination for the harbour design of Point Pedro, regarding the criteria of safety, economic efficiency and environmental impact. It is recommended to EML Consultants that three characteristics of the proposed design should be implemented in their final design for Point Pedro: (1) apply building on the reef for land reclamation inside the harbour, (2) cluster the fish processing facilities near the unloading quay walls, because it optimizes the fish supply chain and reduces fish loss, and (3) construct the jetties for large boats (in the east of the harbour) as proposed, because it optimizes manoeuverability inside the harbour using minimal space. The final recommendation is to perform additional research to make a more accurate design, as the main limitation of the report is the limited amount of available data. Additional research should be done in the fields of; wave data, ground conditions over the entire harbour basin, cost estimation and sedimentation.

This project was executed for Oceanus Interantional, a company providing integral solutions for coastal erosion and flood control, by International Research Project Delft, a foundation offering innovative and challenging business project in emerging markets around the world. During this two months project, four master students from the Technical University of Delft were brought together. They visited project sites and company offices, interviewed employees and several stakeholders, in Mexico and Colombia, to support Oceanus International with a strategy to expand to the South-American market and Caribbean area.

Downstream of hydraulic structures, the flow is normally of turbulence. This will cause considerable erosions on the gravel bed. To prevent this, block mattress is preferable in many cases. Its effective stabilization and feasibility on construction make it commonly used against scouring problems, protecting underwater pipelines and cables. The currently widely used design formula with dedicated parameters for block mattresses was derived by Pilarczyk. However, it is observed to be partly functioning under non-uniform flow condition, since the turbulence parameter is rather empirical. Therefore the main purpose of this thesis is to optimize the current design formula (Pilarczyk’s) for non-uniform flow condition. In this flow regime, turbulence is of importance for bed material entrainment. Thus this research focused on how to introduce turbulence effect into formula explicitly. To predict the failure of block mattress better, a detailed study on failure mechanism and impact of flow condition over the block mattress edge is necessary.

In the light of the waterframework directive, the dutch organisation of rijkswaterstaat has decided to investigate the application of logs as a biological alternative for the protection and cover of both naturally developing scour holes. In this research a laboratory model was created that was designed to develop a scour hole by gradually contracting flow. Subsequent experiments with a cover of logs show mixed, but promising results where scour rates reduce up to 60% with respect to the baseline experiments.

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.

Nowadays, the use of concrete armour units on rubble mound breakwaters designs has become a common practice. Concrete armour units can be placed in a single layer system or in a double layer system and can its placement can be either random or uniform. Recently, Delta Marine Consultants have designed a new armour unit called Xbloc+. This new block is applied as a one layer system and has a regular placement. As Xbloc+ is still under development, preliminary guidance on the performance of this new armour unit is required. This led this research to investigate how Xbloc+ behaves concerning wave overtopping. To analyse wave overtopping, small scale tests were performed in a 2D wave flume. Wave overtopping was measured at a 3Dn distance from the seaward edge of the crest, which is made of rock. In front of the slope there is a flat transition of 0.3m followed by a sloping foreshore of 1/30. In total, 10 series of tests were conducted. In this research, three wave steepness (Sop) were tested (0.02, 0.04 and 0.06) to see the effect of wind waves and swell conditions on the armour layer and tests were performed in two different slope angles (1/2 and 3/4). Each series is formed by several sub tests conducted with increasing wave heights (and wave period in order to maintain a constant wave steepness). Tests were carried out until the failure of the armour slope was reached. Besides, a smooth slope was tested in a 1/2 slope angle to be able to compare smooth and rough results and determine the roughness coefficient of the armour unit more accurately. The test results showed that wave overtopping rates increase exponentially with wave height (Hm0) and wave period (Tm-1,0). Moreover, waves with lower wave steepness (swell conditions) induce higher overtopping discharges as compared to larger wave steepness. Steeper slopes also lead to higher overtopping rates. Therefore, the larger the breaker parameter is, the larger the overtopping discharge results. The influence of the armour roughness and armour permeability is also analysed and it is observed that swell conditions are less affected by these properties. This can be explained by means of the breaker type. Swell conditions are characterized by large surging waves. These waves have a thicker water tongue as compared with other type of breaking (e.g. spilling or plunging) and therefore, they tend to feel the top layer “smoother”. This fact is supported by the analysis of the influence of the roughness coefficient since higher values are obtained for surging waves. In fact, the roughness coefficient ranges between 0.34 and 0.68 showing that, although empirical prediction consider this parameter as a constant, it is dependent on the wave conditions. Concerning the comparison of dimensionless overtopping rate over Xbloc+ armour between test results and empirical prediction, it was found that the present formulae does not give a good estimation due its simplicity. In order to improve the representation of some parameters such as slope angle and wave steepness, correction factors are introduced in the empirical formulae leading to a better fit between prediction and measured data. 

The formation of scour holes is a vital thread of retaining the water infrastructure of rivers. Nowadays, protective filters are used to prevent washing away of the underlying material. Rijkswaterstaat started the program 'Stroomlijn’, in which trees (logs) are cut from the floodplains and placed in a sheltered zone of the river to test whether this would increase the flora and fauna. After some years, the logs might be re-used as bottom protection. This kind of bottom protection is formed by placing multiple logs next to each other, which together form a log carpet, and placing multiple log carpets on top of each other. This is called a log filter. Until now, no research has been carried out into the use of logs as bottom protection. The main function of a log filter is to reduce the hydraulic load so that the erosive capacity of the grains of the bottom will not be reached. Since a log filter has the same main function as a geometrically open filter, this research focuses whether the hydraulic load reduction of a log filter could be described by the current theory of granular open filter. In granular open filter theory, the hydraulic load is defined as the pore flow velocity and turbulent kinetic energy inside the filter layer. The hydraulic load is caused by the influence of the energy slope and the influence of the flow over the filter structure. The pore flow velocity and turbulent kinetic energy caused by the energy slope is always present, regardless of how thick the layer is. The influence of flow over the filter structure decreases exponentially and depends on the load damping length. In order to provide the hydraulic load reduction of a filter consisting of logs, experiments have been conducted in a flume of The Fluid Mechanics Laboratory at the Delft University of Technology. A filter consisting of logs has been mimicked and tested. The hydraulic load, i.e. increasing the depth average flow velocity and discharge, was increased until erosion occurred. During each increasing step, flow velocities above and inside the filter layer were measured. From the experiments, it is concluded that at least two layers are needed in order to ensure a significant decrease of the pore flow velocity and turbulent kinetic energy. Adding more than two layers will not lead to further reduction of the pore velocity or turbulent kinetic energy. The pore flow and turbulent kinetic energy beneath layer 2 are dominantly caused due to the influence of the energy slope. Hence, the equation describing the influence of the energy slope in a granular open filter is also appropriate in case of a log filter. However, the influence of the flow over the filter structure on the pore flow velocity and turbulent kinetic energy in a log filter does not decrease exponentially over depth, whereas in a granular filter it does. Therefore, we concluded that the current open granular filter models which describes the exponential decay of the pore flow velocity and turbulent kinetic energy due to the influence of the flow over the filter construction could not be applied in a log filter. In addition, we concluded that the flow in a log filter is very anisotropic. The flow characteristics differ in front, halfway and behind the log. In front of the log, stagnation is present, which leads to a vertical jet flow directed downwards. This flow causes erosion in front of the logs in the first layer. The erosion process in case of a log filter differs from granular open filters, which stated that erosion is predominantly caused by the hydraulic load, i.e. pore flow velocity and turbulent kinetic energy, in the filter and the bed pressure fluctuations due to low-frequency vortices. We also concluded that at locations where the porosity is higher, erosion occurred at lower hydraulic load conditions, i.e. discharge and depth-averaged flow velocity. This indicates that the porosity is an important variable when logs are used as bottom protection.

The main objective of this thesis is to assess the effectiveness of Nature-based Solutions in reducing flood risk in the Galveston Bay by means of wave attenuation. The methodology to answer these questions consists of both literature review and numerical modelling. The wave height reducing capabilities of marsh vegetation, seagrass meadows and oyster reefs are described and assessed quantitatively. Their limitations and optimizations strategies are investigated and applied to the Galveston Bay, Texas.

The coastal waters of Nigeria are a difficult environment to build structures to control the local morphology and hydrodynamic conditions to ones desire. This difficulty is a consequence of the persistent high-energy swell wave climate and Longshore Sediment Transport (LST) in the order of one million cubic metres per year. Besides these tough conditions, the costs of conventional coastal mitigation solutions are high because of the lack of suitable material (rock) close by. These characteristics of the Nigerian coast led to the interest, whether it is possible to design and construct a ’Sand Breakwater’ for a planned port on the Nigerian coastline at Badagry. A ’Sand Breakwater’ is the complete construction which functions as the protection of the port and creates shelter from incoming waves for ships inside, consisting out of components (partly) made out of sand and hard structures. Especially the very uni-directional and consistent character of the wave climate creates an opportunity to embrace natural processes in the design. In addition, much sand needs to be dredged for the creation of the approach channel along with the port’s basin. This volume of sand might possibly be re-used for a sand breakwater. This report presents the feasibility of a sand breakwater on the Nigerian coastline at Badagry. This feasibility is determined both morphologically and economically. Long term coastline development was modelled with the one-line coastline evolution model LITPACK. Results show that the persistent uni-directional character of the wave climate prevailing at the coast of Badagry forces an equilibrium coastline orientation of 277.5 degrees with respect to True North (TN). Because of this, all other orientations of coast rather than the equilibrium orientation are vulnerable and will develop to the equilibrium orientation over time. The implementation of this equilibrium orientation in the design along with some hard structures led to multiple long term morphological stable conceptual variants for a sand breakwater. The coastline impacts of these variants west of the sand breakwater were examined on large scale. In 38 years after construction a maximum of 20 meters coastline retreat occurs, which is considered acceptable. After this period, only shoreline accretion takes place. To establish complete conceptual designs, the cross-shore profiles are first determined. The submerged part of the profile up to the top of the intertidal profile is constructed by integration of measured data in the design. The emerged part of the profile concerns the cross-section of a dune and was the critical part for the designing objective. To determine these profiles, first the design crest height is determined by applying maxmimum acceptable overtopping volumes (Tilmans, 1983). Knowing the design crest height, the dune width is determined by modelling storm impact. This width is established by examining storm impact and determine what minimal required width needs to be present for the sand breakwater to live up to its design criteria. Storm impact for the found conceptual variants is examined with the numerical software XBeach to determine cross-shore sediment transport during storm impact. The impact of storms with shorter return periods results to be relatively high in comparison to the storms with longer return periods. This is taken into account by adapting the design conditions. The design storm conditions are based on the impact of a storms with a 1/100 year return period along with an expansion for a consecutive storm with a return period of 1/1 year. With this storm impact known, the required crest width is determined and with that the minimal required cross-shore profiles for the multiple variants are established. Consequently, besides long term morphologically stable, the conceptual designs are capable to design storm impact, confirming the morphological feasibility. In order to define the economical feasibility of a sand breakwater, a comparison between the different conceptual variants and a conventional design is made. This comparison is conducted via a rough cost comparison along with examining future prospects. In order to be able to make this cost comparison, rough volume estimations are done for all conceptual variants and conventional design. These volume estimations combined with unit prices lead to a rough cost comparison. From this rough cost comparison appears that a sand breakwater showed to be in the same price range as a conventional design. Three future prospects of a sand breakwater are determined. First of all the by-pass of sand is compared for the conceptual designs to the conventional design. The characteristic LST is problematic due to the occurrence of sand by-passing causing sedimentation in the approach channel and port. One of the conceptual variants shows that a sand breakwater is proven to be able to provide a period without by-passing of sand in the same order of magnitude as a conventional design. Another future prospect is the required maintenance necessary to execute for the sand breakwater. The XBeach results of lower storm conditions show that maintenance costs are high. However, these results are assumed to be heavily overestimated. Results with more specific ’Nigerian conditions’ create reason to believe that maintenance for lower storm conditions will be much lower and in acceptable range. The last future prospect concerns the accreted land which arises due to the blockage of LST. A sand breakwater creates the possibility of acquiring land for new port space which is not possible with a conventional breakwater. In addition, the value of a Building with Nature component is present in this project and could enhance its economical interest. Not only the morphological but also the economical feasibility of a sand breakwater is confirmed. The ’Sand Breakwater’ succeeded to convert the drivers of the problem to its solution, leading to an innovative and in all likeliness even more cost-effective solution compared to the traditional approach.

When sea-going or inland vessels berth along a mooring location they use their bow thruster to manoeuvre. When the induced propeller jet is directed towards a slope it might affect the stability of the slope material and this can lead to damage when the loads are too large. The objective of this research was to extend and validate a method to determine hydraulic bed loads on slopes induced by bow thrusters and a method to determine the stability of slope material. In order to answer this objective scale model tests are conducted at the test facilities of Deltares. Velocity and stability measurements are performed during multiple test scenarios that contain variations in slope angle, axial distance and pile configuration. From the obtained data of the velocity measurements the time-averaged velocities and the turbulence intensities are determined. For example, the time-averaged slope velocities measured in the scale model that consists of an 1 : 3 slope with an open quay pile configuration and a rough bed (test scenario T10 in the research) are shown in Figure 1. These values are compared to the values according to the Dutch guidelines and a correction factor for the underestimation of the hydraulic bed load on a slope is defined for each test scenario. After that the consequences for a design of a slope protection are evaluated. Furthermore, for the stability tests it is determined what the critical slope velocity is. This is done for multiple criteria of initiation of motion. With these critical slope velocities a stability parameter for the stability relations can be determined that is applicable at situations similar to the scenario tested. These determined stability parameters are compared to the recommended stability parameters and the differences are evaluated. Finally recommendations are formulated for correction factors for the slope velocities induced by bow thrusters and recommendations are formulated for a proposed stability formula by an earlier research.

Block mattresses are widely used bed protection elements under non-uniform flows. Previous studies show that the turbulence of the flow plays a key role on the instability of the mattress. However, in the available design equations, the turbulence intensity is included as a magnification factor roughly and qualitatively defined. Consequently, the design equations are often used as a rule of thumb, where the engineering criteria of the designer is critical and large safety factor are used. In turbulent non-uniform flows, the available design equations were developed for uniforms flow and the turbulent intensity is included as a magnification factor, usually poorly defined. The stability reduction due to turbulence has been proved by several authors. However, there is not any study in previous literature that investigate the role of velocity fluctuations on block mattress failure. Nevertheless, the literature review showed that an innovative approach, which combines the mean velocity and the turbulence intensity to quantify the flow forces, has been largely study for loose rock by several authors. Following this trend, the option of applying this structure (u ̅+α√k) as a flow quantification on Pilarczyk equation was decided to study. For this purpose, a series of test were done under four different configurations. Two weir heights were used (15 and 18.5cm) and the distances corresponding to 3h and 4h were checked. Four failures were recorded for each configuration for a total of 16 failures. Additionally, a data base was recorded for each configuration where the flow discharge was related to mean velocity and the turbulence intensity. An analysis of the failure mechanism was done by synchronizing the velocity time series with the displacement of the blocks. The results showed that an episode of peak streamwise velocity and downwards (sweep) was present at the failure. However, the analysis of the velocity showed that higher combinations of streamwise velocity and shear stress were present before the failure on almost all the records. Therefore, the streamwise velocity and the induced shear stress cannot solely explain the failure of the block mattress. This conclusion is in line with the work done by Hofland (2005). However, the recorded data did not allow to describe completely the failure mechanism. The turbulence magnification factor (α) at the stability equation was derived by two different approaches. The first approach was based on the peaks of velocity associated to failure while the second one was described as a fitting parameter. The analysis concluded that the α values were close to 3 for both cases, in line with the expected value from previous studies. Finally, the new developed equation was compared with the original Pilarczyk equation and the modification proposed by the Rock Manual (2007). The comparison shows that the new developed equation described the required thickness of the block more accurately than the available equations. Thus, the results show that the proposed approach described the effect of turbulence accurately on a design equation. Additionally, all the relevant derived conclusions for design propose were summarized in a design guideline.

In this MSc thesis it is investigated how the first version of concrete armour unit Xbloc+, Xbloc+ v1, acquires its stability. The stability mechanisms are investigated by conducting two type of physical model tests. First, 23 dry pull-out tests are done to obtain insights into the aspects and mechanisms that influence the armour layer stability. At 8 locations per slope, blocks are pulled out to determine the force needed to extract an armour unit. Tests are done on a 3:4 slope with 2 pull-directions; under an angle of 45 degrees with respect to the slope and perpendicular to the slope. Concrete as well as plastic armour units are tested, both having a different surface roughness. The conclusions of the pull-out tests are verified by means of the second type of model tests; small scale physical hydraulic model tests in a 2D wave flume. In total, 10 tests are conducted; 6 tests with plastic armour units and 4 tests with concrete armour units. Each test starts with a run with a small significant wave height which is increased stepwise in each run until failure occurs. All test sections have a 3:4 slope and are subjected to waves with a 4% steepness. Additionally, the influence of the significant wave height step size for successive runs is investigated. The combination of both physical model tests results in recommendations for a change in design which is expected to lead to a higher stability of an armour layer with Xbloc+ armour units.

This report contains a study for the Integral Coastal Defence System for the Malecón in the city of Havana, Cuba. The objective was to develop a sea defence solution that prevents unacceptable flooding of the hinterland and damage of the Malecón seawall. Deriving solutions from earlier reports and using old and new data, a solution is proposed for the entire Malecón. This solution does not meet the strict requirements set by the local governments, but it reduces the overtopping significantly. It is recommended to build a curved seawall along the entire study area, which will be supplemented with artificial berms and breakwaters at specific locations.

The focus of this research is to provide solutions to the city of Campeche to decrease the inundation risks generated by a hurricane with an occurrence of once in fifty years. Campeche is a city located at the Gulf of Mexico on the Yucatan Peninsula. The rapid growth of the city is one of the reasons it is having troubles with the water and flood management of several areas throughout the city. Although the municipality has already executed some improvements to the drainage system during the last years, it is still lacking to cope with heavy rainfall and storm surges due to hurricanes at several areas in the city. In order to gain a better understanding of the location and the way it works in Campeche a location, stakeholder and political analysis have been performed. Boundary conditions, program requirements and preferences have been formulated based on this analysis. By examining hurricanes over the last decades, a hurricane has been simulated with an occurrence of once in the fifty years. In the situation characterisation the city has been divided into several catchment areas to determine their vulnerability (expressed in total amount of water accumulation), taking into account the capacity of the current drainage system in the event of such a hurricane. Four solutions have been chosen to elaborate. In this elaboration, calculations have been performed on the design and construction. For the implementation of the options suitable locations have been determined and the possibilities and risks have been defi ned. In order to test the elaborated solutions on socioeconomic factors in combination with ecology, safety and politics, a multi-criteria analysis has been performed. It can be concluded that all options differ a lot from each other. Every option tackles another side of the problem and therefore they score on totally different aspects. In the discussion, it is further elaborated what the supplementary advantages and disadvantages of the proposed solutions are. Using this, the integral system of water management measures is considered. A few fields can be found on which could be made an improvement in the future. Firstly, the political system requires short term measures to count on enough support. Besides, citizens should be kept informed and have to be made aware of the flooding problem. Drainage expansion needs to take place in order to relief the most crucial parts in the city from their excess of water during extreme weather conditions. Lastly, when expanding the city, the amount of green space and inundation risks of the concerning area should be always kept in mind.