Backward erosion piping (BEP) is a common failure mechanism of dikes. Dikes are currently assessed on this mechanism with the Sellmeijer 2011 rule, a method based on experiments with homogeneous deposits. However, the presence of tidal fines positively influences the cohesive strength of soils and the embedding of the soil grains in the soil matrix. For analytical assessment of BEP, a strength factor of 1.4 [-] is currently used in Dutch regulations to incorporate the extra strength due to tidal deposits. Tidal deposits also correlate with anisotropy in hydraulic conductivity due to the layering of tidal deposits. This influences flow patterns in the aquifer, thereby affecting the BEP process...

Flood risk management has traditionally been centered around economic damages and casualty assessments, providing a basis for preventive measures like levees. However, with increasing climate change-induced weather extremes, a shift toward flood resilience is necessary. This shift involves accepting some level of flooding while enhancing system recovery and damage mitigation. Existing resilience frameworks offer only qualitative insights or rely on significant assumptions, limiting their applicability in objective assessments.

This research focuses on addressing the challenges of quantifying flood resilience, a concept inherently complex due to its multi-layered nature and reliance on diverse perspectives. By incorporating hydrodynamic conditions such as water depth, flow velocity, and momentum, alongside local topography and land use, this study aims to propose metrics that better capture the temporal and spatial dynamics of flood resilience. This enables objective evaluation of mitigation measures, guides resource allocation, and facilitates informed decision-making for engineers and policymakers alike. This could subsequently enhance flood risk frameworks and increase flood safety in The Netherlands.

A methodology for quantifying flood resilience through hydrodynamic modeling is presented in this study. It identifies functionality variables like temporal water depth, temporal impact, number of flooded buildings, and percentage dry area as central to assessing resilience. From these functionalities, resilience metrics are derived, like shock amplitude, arrival time, and residence time.

The methodology is tested through a case study in the Alblasserwaard. The study uses 3Di modeling software to simulate flooding scenarios and evaluate the applicability of resilience measures. This is done through model variations and interventions such as detention basins, moveable barriers, and enhanced pumping capacity. The chosen case study includes diverse land uses, enabling the assessment of resilience across residential, economic, and ecological perspectives.

The metrics of shock rate, residence time, flood arrival time, and flooded utilities provide promising insights into flood resilience. The derivative shock rate evaluates emergency response service capacity, while residence time assesses damage extent and recovery time. Adding indirect hydrodynamic conditions, like nearby flooded roads and utilities, further enhances system understanding in the provided case study. Different perspectives highlight the variability in suitable metrics as well as suitable interventions.

However, some metrics require further research or modification. The depth integrals show potential during shock and recovery, but they lose information when used as a linear metric between time and water depth. The flooded utilities metric provides valuable insights but needs expansion to accurately reflect flooding consequences. The momentum impact metrics are unsuitable for the current model due to limitations in 3Di’s flow velocity calculations.

While the method proved feasible for identifying and comparing
resilience in a specific system, further research is needed to address uncertainties, refine metrics for indirect effects, and test applicability beyond the presented case study. This framework represents a further development toward a comprehensive, objective approach to flood resilience, supporting effective, adaptable flood
management solutions even under the continuous threat of increased climate extremes.

This thesis aims to find the best way to construct a surrogate model for the inner slope stability of a dike and combine this surrogate model with other (machine learning) models to generate conceptual flood defenses, making it possible to optimize the dike design using an interdisciplinary MCA.

Flood risk management is essential in water resource planning to reduce potential damages and losses in flood-prone areas. Traditional risk assessments often focus on monetary values and ignore equity, leading to unequal distribution of protective measures. The equity weighting method has been implemented in past studies, but at certain administrative levels, it may not capture the income heterogeneity within those areas. This research investigates how accounting for income heterogeneity within administrative areas affects equity-weighted risk and impact estimates and explores practical ways to implement this approach, given privacy-related data limitations.

The study focuses on Charleston County, South Carolina, using disaggregated methods at the household level to integrate detailed socioeconomic data into equity-weighted flood risk assessments. The methodology involves assuming an equal distribution of income within predefined brackets and optimizing upper and lower bounds for open income brackets. Additionally, a linear relationship is assumed between the structure value and household income, allowing for the spatial allocation of income within census block groups.

The results demonstrate that the disaggregated method identifies more vulnerable households and shows significant differences in equity-weighted damage (EWD) and equity-weighted expected annual damage (EWEAD) metrics compared to the aggregated method. These findings suggest that the disaggregated method provides useful evidence for considering the importance of taking into account income heterogeneity when assessing flood risks, particularly in areas with significant income inequality.

Sensitivity and uncertainty analyses indicate that the income distribution parameters show both low sensitivity and low uncertainty when using a fitted log-normal distribution, suggesting that this distribution is a good fit for the data and provides stable results. In contrast, in the spatial allocation of income with structural values, the analysis results show high sensitivity and significant uncertainty, which means small changes in structure values lead to substantial variations in equity weight estimates.

The study concludes with recommendations for stakeholders to adopt household-level analysis and incorporate equity weights in cost-benefit analyses. Future research should explore additional socioeconomic factors, develop dynamic risk assessment models, and apply the methodology to diverse geographic and economic contexts.

Known for its low-lying and flood-prone geography, the Netherlands has a long history of flooding. Flood events in the 1990s, which led to large-scale evacuations, shifted the country's focus from simply strengthening dikes to creating more space for rivers to flow and storing water to prevent similar disasters. With changing climate conditions, rising water levels, land subsidence and sediment supply issues, the safety of primary flood defences needs to be regularly reassessed. The latest safety assessment, using a new methodology that assesses dikes based on the probability of flooding, found that many dikes do not meet the required safety standards. These dikes will need to be redesigned and reinforced, and there are opportunities for innovative and environmentally friendly solutions.
Previous research has extensively investigated the potential of different ecosystems, such as salt marshes, mangroves and willow forests, to reduce the impact of waves on coastal and riverine structures. Studies have shown that vegetation can significantly dissipate wave energy, thereby reducing the load on flood defences. However, the dynamic and unpredictable nature of vegetation has made it difficult to incorporate it reliably into defences. While there is general agreement on the benefits of vegetation for wave attenuation, its reliability in reducing failure probabilities requires further investigation.
This thesis tests the potential of riparian forests for wave attenuation and dike design optimization. The main objective is to investigate how wave attenuation by riparian forests can improve dike safety and to identify the critical variables that most significantly affect the probability of flooding. Key research questions include how wave attenuation can contribute to dike design and safety assessment, and which variables most influence the probability of flooding.
Vegetated foreshores can reduce the height of incoming waves, with positive implications for dike design and safety assessment. A model was developed to test this by combining current wave impact and run-up models with a wave energy balance that includes energy dissipation by vegetation. The model was subjected to a Monte Carlo simulation to determine the probability of dike failure due to erosion of the outer slope by wave impact and run-up. The model analyzed a dike section near Kampen and showed that riparian forests can significantly reduce the impact of waves on dikes. The results showed that the forest length, frontal-surface area and stiffness of the forest must be large enough to be effective. Strategically placing trees with the largest frontal-surface area at critical points can significantly reduce the probability of dike failure.
In conclusion, this thesis highlights the potential of riparian forests to improve dike safety and contribute to a more resilient and environmentally friendly flood protection strategy in the Netherlands.

The integration of biological and (bio-)geochemical processes in soils is posed to become the next transformative practice in geotechnical engineering. Soil Sealing by Enhanced Aluminium and dissolved organic matter Leaching, also known as SoSEAL, is inspired by a natural soil formation process, called Podzolization. This process results in the formation of a nearly impermeable spodic B-horizon. A similar low-permeable layer is made by SoSEAL. The products of the chemical reaction between aluminium and organic matter generates organic precipitation, clogging the pore throats between sand grains. Past research on SoSEAL has primarily centered on its application as a low-permeable water retaining barrier used for dyke improvement. However, the broader impact of SoSEAL on the mechanical properties of soils beyond permeability remains largely unexplored.

Despite progress, gaps persist in understanding SoSEAL’s influence on sand’s mechanical properties, particularly on the shear strength. The primary objective in this research was to investigate the impact of different concentrations of Al-OM (Aluminum and Organic Matter) flocs on sand’s mechanical characteristics through ex-situ mixing. This included the development of a testing procedure using a triaxial test apparatus, incorporating results from permeability tests and utilizing microscopy to analyze micro structural changes and the underlying mechanisms. The study aimed to deliver valuable insights into SoSEAL’s potential as a nature-inspired geo-engineering solution for soil improvement.

Undrained triaxial tests were conducted on ex-situ mixed sand with different concentrations of Al-OM flocs, namely 0, 0.1, 0.5 and 1%. These concentrations were defined as dry mass of flocs based on a metal/carbon ratio of 0.06. Through a carefully executed test procedure, involving Proctor’s test, permeability measurements and triaxial testing, the mechanical properties of the treated sand were investigated. Proctor’s tests were utilized to determine the maximum dry density and its corresponding moisture content of the (un)treated sand. These parameters were used for molding the sand samples for the triaxial test series. The untreated sand did not show a clear peak in its Proctor curve, which is typical for uniform graded fine/medium sands. The porosities, derived from the optimum dry density and corresponding water content, were found to be ≈ 0.4 (-) for all samples. Indicating the minor impact of the Al-OM flocs to the porosity of the sand samples.

The undrained consolidated triaxial test procedure, consisting of saturation, consolidation, and shearing, provided insights into the mechanical properties of SoSEAL. Although the consolidation phase did not reveal significant differences
in the presence of Al-OM flocs, elastic parameters, derived from the shearing phase, generally increased with higher Al-OM floc concentrations in sand. Young’s Modulus, E , increased by a magnitude between 2.11-2.62 times the untreated sand, while the shear Modulus, G, increased by a magnitude between 2.09-2.18. Nonetheless, exceptions such as test CU05-1 and CU10-2 were observed. Strength parameters, measured by maximum deviatoric stress at failure, exhibited an overall increase with higher floc concentrations. Finally, the results show that an alteration in floc concentration in sand did not have a significant impact on its permeability, contrary to previous measurements obtained in the absence of confinement.

The results from the Proctor’s test, permeability measurements and the triaxial tests highlighted differences and improved general knowledge of the impact of Al-OM flocs to the mechanical properties of sand. Variations in test results, seen
when comparing test CU05-1 to CU05-2 and test CU10-1 to CU10-2, underscored the complexity of factors such as compaction challenges and localized failures. From microscale examination using scanning electron miscroscopy (SEM), the increase in strength properties can be attributed to the cohesion between sand grains, evident in the formation of grain clusters. As the concentration of Al-OM flocs in sands increased, so did the quantity of grain clusters. The potential of Al-OM flocs in sand for dyke improvement is found in the observed increase in elastic and strength properties, providing enhanced resistance against erosion.

The frequent occurrence of catastrophic tailings dam failures underscores the urgent need to improve safety practices and minimise associated risks. This study introduces an advanced tool to evaluate the total Probability of Failure (PoF) of existing tailings dams systematically and effectively, supporting the rational prioritisation of mitigation efforts and minimise risk within the 'As Low As Reasonably Practicable' (ALARP) principle.

The tool utilises a semi-quantitative approach, combining observation frequency and expert judgment. A baseline PoF for each dam construction method and failure category is established using a database of 450 tailings dam incidents and accidents developed in this study. This baseline PoF is subsequently modified based on site-specific factors influencing failure prevalence. A total of 255 key contributing factors are identified based on a fault tree analysis, the Global Industry Standard on Tailings Management (GISTM), and experts in the field. The factors encompass site conditions, design elements, and the level of practise, which address all major credible failure modes and mechanisms. The factors are linked to the failure categories they influence and assigned relative weights through the analytical hierarchy processing method for each dam construction method and failure category. Subsequently, the weights are multiplied by modifiers to account for the effects of site-specific conditions (favourable: 0.2, neutral: 1, adverse: 5, and unknown: 2). Within the tool, users can choose fulfilment conditions for each factor from drop-down menus and the selected inputs are connected to the modifiers. The adjusted weights are multiplied by the baseline PoF of each failure category, given the dam construction method. The summation of these products yields the total PoF of the investigated dam.

The results provide preliminary insight into factors significantly affecting the total PoF for the dam under investigation, aiding in evaluating whether the PoF reduction justifies costs. It facilitates preliminary, rational prioritisation of mitigation measures in accordance with the ALARP principle, contributing to ongoing efforts to improve tailings dam safety.

To validate the tool’s capabilities, two case studies with available data are analysed: the Aznalcóllar failure to examine the ability to identify high-risk factors and a recently improved dam to evaluate if the mitigation efforts are adequately reflected. The studies demonstrate the tool’s potential but also reveal uncertainties, inaccuracies, and limitations. These stem from discrepancies in the baseline PoF, weightings, modifiers, and unaccounted factors. Therefore, caution is warranted in the tool’s utilisation. Recommendations include various improvements and further verification and validation across a broader range of case studies. Value can be added by incorporating additional components and adapting the tool for new dams.

In many places in Uganda, people do not have a connection to the drinking water supply system and there is a lack of treated water supply, meaning that people only have access to water a certain part of the day. As a result many people rely on springs, handpumps, rivers or lakes, of which the quality cannot be monitored or controlled.

During this multi-disciplinary project, we worked together with the National Water & Sewerage Corporation (NWSC) and the Ministry of Water and Environment (MWE) to research the possibilities of extending the water supply system of two project areas, Bugiri District and Hoima City. The current water supply in both areas use groundwater as a source and the possibilities for the extension also consider using surface water besides groundwater.

The different alternatives for the extension of the water supply in Hoima City and Bugiri District are evaluated using a multi-criteria analysis (MCA), consisting of a financial analysis, a performance analysis and a risk analysis. By evaluating the different options using an MCA, the decision-making process can become less complicated.

The MCA-tool that is set up in this research can be used by engineers to study different areas in Uganda and make it easier to compare different options for the extension of a drinking water supply system in an early design stage. The tool is for the two project areas as examples, after which it is also tested during a case study with engineers from both NWSC and MWE. Useful feedback came out of this session which will be used to finalize the tool and elaborate on it.

To design the different alternatives for the project areas and to get insight into the drinking water supply of Uganda, Hoima and Bugiri are visited at the beginning of the project.

For both project areas, it is recommended to improve the operational performance of the already existing groundwater supply system as a short-term (5 years) solution. The long-term (25 years) solutions consider groundwater options as well as surface water options, using for example Lake Victoria, Lake Albert and River Nile as water sources.

Under the current climate change projections, droughts and extreme rainfall events are becoming more common and intense. During sustained droughts, soil cracks can develop in the topsoil of a dike. These soil cracks can enhance the infiltration and drainage of the dike, affecting the dike stability. This study’s main objective is to better understand the potential influence of cracks on the hydrology and dike stability of canal dikes. A finite element model (FEM) was built to study the hydrological response and stability of a canal dike due to rainfall infiltration through a uniformly distributed cracked top layer. This model included the fast hydrological response of the fractures and their exchange with the soil. A surrogate model (a simplified data-driven machine learning model) was built using training data generated by the FEM to reduce the computational burden and allow for a sensitivity and stochastic reliability assessment. An evaluation of important model features, such as the connectivity among cracks and soil swelling, revealed that the cracks have a very localized influence on the infiltration and drainage of water through the dike. Water drainage in the toe of the dike is restricted by soil swelling resulting in a larger decline in dike stability. The sensitivity analysis found that the cracks facilitate more infiltration than drainage before the crack parameters, such as the crack aperture and the amount of cracking, reached a threshold. Above this threshold, drainage provided by the cracks is greater than the infiltration. The failure probability was calculated for a variety of different rainfall patterns. A pattern where the rainfall intensity incrementally increases over time results in the highest failure probability. The main conclusion from this study is that soil cracks influence the stability of the dike by enhancing infiltration and drainage under rainfall. Under low-intensity rainfall, the cracks in the toe facilitate more water to drain out of the dike than rainfall to infiltrate, stabilizing the dike. However, in the absence of cracks in the toe, the cracks provide more infiltration than drainage resulting in a lower dike stability. Under high-intensity rainfall, cracks in the crest and the inner slope of a dike advance the wetting front resulting in a larger decline in dike stability than a dike without soil cracks. Rainfall infiltration and drainage in a cracked dike depend on both rainfall characteristics, such as the average rainfall intensity, duration, and pattern, and the crack features, such as the crack width, amount of cracking, and the connectivity of the cracks. Since this study was not validated with observations, it is recommended that further studies aim to validate the observed influence of the cracks by conducting field experiments.

Dunes are the primary sea defence along the Dutch coast. This research investigated the development between 1965 and 2021 of the beaches and dunes of the Hoogheemraadschap Hollands Noorderkwartier (HHNK) area which stretches from IJmuiden to northern Texel. This research used an advanced data analysis on the annual coastal elevation data. The coastline of the HHNK area is maintained by several different measures including nourishments, planting and removal of grass, placing reed fences and building regulations. The aim of this research was to relate the investigated developments of the beaches and dunes to these measures and natural processes.
A literature study was performed first, to get acquainted with the research area and the processes that drive the beach and dune development in the area. In four phases, the developments and their relationships with the drivers were investigated for several subsections of the research area that showed similar behaviour. In phase 1, the coastal profile data was collected for multiple transects spanning the research area. Characteristic parameters describing features of the dune and beach were derived from the coastal profile data. In phase 2, the collected profile data was decomposed into spatial and temporal patterns by a principal component analysis. In phase 3, the transects of the research area were categorised on the temporal development of their coastal profile using the results of the spatial and temporal decomposition. This created subsections of the coast that showed a similar morphological behaviour. In phase 4, the morphological behaviour of several subsections was investigated and related to the natural and human drivers. The relationships between the drivers and the developments were investigated for several subsections, varying in morphological behaviour and drivers, to gain insight into these relationships for the entire research area.
The coastal categorisation resulted in 36 subsections which were mainly continuous in space with the exception of four clusters. Seven subsections were studied in more detail, by investigating the development of several characteristic parameters derived from the coastal profiles, like dune volume, beach slope and shoreline location among others. The shoreline location and beach width showed a strong correlation with the nourishments. The beach slope and width were expected to influence the dune volume changes, which was not supported by the results. The beach width is assumed to be larger than the critical fetch length and the variations in beach slope had a marginal effect on the transport capacity. The presence of beach pavilions limited the dune growth in both height and volume, but regularly moving the pavilions did allow for a seaward migration of the dune front. The effect of small beach houses on the dune volume change was found negligible. Maintenance works of HHNK influenced the dune development locally. The placement of reed fences caused seaward migration of the dune front and the creation of blow-outs increased the dune volume behind the most seaward dune. The strongest dune volume increase was found at coastal areas behind shoals that reduced the incoming wave energy.
The coastal categorisation succeeded in grouping transects with a similar development of their modified coastal profiles. Several modifications were proposed to improve the categorisation of the original profiles and to take into account smaller scale processes. Nourishment was distinguished as most important driver for the development of the coastal area, which has maintained the shoreline location and caused a trend break in several other characteristic parameters. Human influences like buildings, coastal structures and reed fences have a strong local effect on the development of the beaches and dunes. Further research could take into account wave and wind climate, water level variations and grain size quantitatively to get a more comprehensive study of the relationships between the development and the drivers.

Anticipatory action requires models that can accurately and reliably predict the impact of natural hazards. However, impact forecasts are often underestimated when consecutive hazards are not considered. In the Bicol region in the Philippines, typhoons trigger 90% of landslides, causing a lot of fatalities and damage to infrastructure and agriculture. The lack of information on past landslide events has hampered the construction of landslide forecasting models. Currently, a machine learning (ML) impact-based forecasting (IBF) model for typhoons is operational in the Philippines. The model was developed by 510, an initiative of the Netherlands Red Cross. The model predicts impact due to the high wind speeds associated with typhoons and includes the possible impact due to landslides only via a static landslide susceptibility map. Hence, this study focused on extending the 510 typhoon model via hybrid modeling into a multi-hazard forecasting model for both typhoons and landslides to improve the forecast by considering impact from typhoon-induced landslides. The implementation of the hybrid multi-hazard impact-based forecasting model was tested on two typhoon events in the Bicol region.

A hydrometeorological landslide IBF model was successfully created, even with the limited data on landslide occurrences and rainfall available. The newly established regional event duration threshold for Bicol was applied on the case study events with an increased impact boundary of 300 km compared to the typhoon impact boundary of 100 km. The results of the hybrid multi-hazard model showed an improved impact forecast -compared to the model considering solely static input of landslides, which underestimated impact- in both location extent of the impact forecast and in accuracy: the True Positives doubled, whereas the False Negatives reduced by half. The separate landslide IBF model as an extension of the existing ML typhoon model provided additional benefits as these models can be decoupled to optimize the performance and reliability of both. This study resulted in the prototype of an impact-based multi-hazard model for typhoons and landslides for the Philippines and demonstrated the importance of considering impact from consecutive hazards.

Hydrokinetic energy is an environmentally friendly source of electricity and it has the advantage to be more predictable compared to other renewables. According to IRENA (2020), the capacity of converting hydrokinetic energy into electricity is expected to increase in the coming decades as many concepts are in the pipeline. One of these hydrokinetic energy concepts is the patented Van Rompay Turbine. The Van Rompay Turbine consists of a duct, an air chamber and a paddlewheel. The duct, which is based on a Venturi working principle, consists of a converging inlet, a throat and a diverging outlet. Above the throat, an air chamber is present to provide an air environment to reduce resistance for the paddlewheel. The goal of this research was to experimentally and numerically test a prototype (L:4.05m x W:1.17m x H:1.17m) of the ducted system.Three inclination angles: 21°, 26° & 31°, for the converging inflow and diverging outflow segment were tested, referred to as the small, medium and large ramp size, respectively, to determine which size represents the lowest energy losses in the system. The small in -and outflow ramp represents the lowest energy losses compared to the medium and large ramp. Subsequently, on the small inflow ramp, five designs were tested, referred to as the straight, curved and the high, mid & low frequency waved designs; to again determine which design represents the lowest energy losses. Roughed waved wall designs are streamwise wavy walls with each a different wavelength and amplitude. The small ramp with a high, mid & low frequency waved design results in the lowest energy losses in comparison to the straight and curved designs for inlet velocities between 0 m/s and 0.4 m/s. For inlet velocities between 0.4 m/s and 0.5 m/s, the small ramp with a curved design represents the lowest energy losses in comparison to the straight and high, mid & low frequency waved designs.The data points acquired during the experiments were scattered due to external factors increasing the uncertainty of the measurements. Besides this, the experimental investigations were tested over an inlet velocity between 0 m/s and 0.5 m/s, limiting the data analysis. For this reason, several CFD simulations were carried out to acquire data with no influence of external factors and to investigate the system for higher velocities. The CFD simulations were executed for the five different inflow ramp designs with an in -and outflow inclination angle of 21°. The CFD model solves the Reynolds-averaged Navier–Stokes (RANS) equations with a k-epsilon turbulence closure model. Based on these CFD simulations, the best performing design for the inflow ramp in terms of the lowest energy losses for an inlet flow velocity between 0 m/s and 0.75 m/s is the high frequency waved design. Regarding velocities between 0.75 m/s and 3 m/s, the curved design represents thelowest energy losses compared to the straight and high, mid & low frequency waved designs. After scaling up the ducted system in CFD simulations with a factor 2 and 10, the flow velocity reduces as there are more energy losses in the system. However, as larger systems have a marginal lower specific surface of contact between the water and the duct, an increase in available flow power could be found. The extent to which the ducted system can be scaled up depends on the space restrictions at the specific location. Besides, the minimal required inflow area of the free water flow should be met. It can therefore be concluded that the potentially available energy for generation also depends the location where the Van Rompay will be deployed.Experiments need to be performed to study the hydrodynamic impact and the hydrodynamic efficiency of the paddlewheel to determine the power performance output and thus its potential value for the hydrokinetic energy market. It is recommended for future research to test the prototype at higher velocities and to test the prototype in a laboratory facility as these offer the benefits of controlled testing.

Large areas of the world are protected by flood defence systems. A common part of flood defence systems is a levee with grass cover, with the primary function to protect hinterland against floods. Waveovertopping might lead to erosion of the grass cover, followed by erosion of the inner slope and potentially levee breaching. The wave overtopping simulator (WOS) was developed for full-scale and insitu testing of the erosional resistance of levees against wave overtopping. The first experiment with this simulator was carried out in 2007 and more followed. However, the data gathered during these overtopping experiments has always been considered on individual experiment scale or in small subsets, exception being the Cumulative Overload method. The experiments proved to be difficult to reproduce, seemingly identical experiments gave different results. The objective of this thesis is to combine WOS data and multiple grass erosion models to make a prediction for the failure of the grass cover. Key features that determine the prediction of failure are the location and moment of failure. Therefore, these are included in the main research question, which is identified as: How can grass erosion models and WOS experiment data be combined in a new method to generate a prediction of the moment and location of the grass cover failure due to wave overtopping? A literature study on grass erosion and grass erosion provides the basis for modelling grass erosion, a review of combination techniques gives insight in combining results for a prediction. A selection of models is discussed and used for setting up a prediction method. These include three flow-based models which are semi-realistic simplified representations and time-independent over a single overtopping event: Cumulative Overload Method, Analytical Grass Erosion Model and Dean Stream Power. These models are, where required, adjusted to model grass cover failure and to comply with identical hydrodynamic input. A fourth model, the Wave Impact Approach, is an impact-based approach. Each model is calibrated on each WOS experiment, creating a set of calibrated models, which function as the set of predictors. The number of predictors equals the number of models times the number of experiments. During calibration, the moment of failure has been traced back using the control list of the WOS, and vice-versa, resulting in a moment during the experiment at which the grass cover failed. Detailed review of all factual reports on WOS experiments and the nature of the grass erosion models highlighted the need for a locationdependent resistance parameter to determine the location of failure. Therefore, calibration was based on a location-depended resistance parameter; critical flow velocity for the flow-based models and critical pressure for the impact based model. This set of predictors has been used to create a set of predictions for each of the five validation experiments, input being the geometry, loading and initial condition of the slope. The initial condition given by a registration of anomalies to the average grass cover. Failure is determined by vote and averaging. After validation, none of the final predictions proved to be fully correct. Meaning that none of the final predictions correctly indicated the location and moment of the first grass cover failure. Despite this, in four of the five validations at least one correct failure location was indicated when considering the specific anomalies. The main shortcoming is concluded to be the prediction of number of waves until grass cover failure. Based on this research and given a certain average grass cover quality, it is concluded that the resistance against grass erosion by wave overtopping is described by resistance against erosion of anomalies. For at least 22 of 28 sections in the dataset, grass cover failure occurred at an anomaly of the average grass cover. No grass cover failures occurred related to the average grass quality. Especially mole activity showed a significant 46% decrease in the averaged calibrated critical flow velocity with relative to that for the average grass cover. This leads to the conclusion that design and safety assessments should include conditions other than the average grass quality. For future research a method is recommended that divides mole activity into classes, based on certain characteristics. Each class distinguishable by unique combination of properties and assigned a resistance against erosion. For design, the probability of occurrence of each class must be determined and combined with the corresponding influence on the resistance against erosion. For assessment, an inventory or representative sample of animal activity must be available to asses if the occurrences of animal activity are within the design requirements.

Geogrids are commonly used for reinforcement of soils in construction of railway and road embankments and bridge abutments. A relatively new application of geogrids is the anchorage of sheet pile walls, in which one or more layers of geogrid are attached to the sheet pile wall. This type of anchorage is particularly suitable for projects with sufficient space behind the sheet pile wall. This anchorage system has some mayor advantages in comparison to conventional sheet pile wall anchors as it is cost-effective and requires less steel. Moreover, prestressing is possible during construction and pile foundations can be installed through the geogrids. An analytical design calculation method for this type of anchorage is not yet available in the Dutch design guideline for the design of sheet pile walls (CUR166). The demand for short anchorage systems because of the commonly limited space behind sheet pile walls, shifts the focus of the design to the minimum required length of the geogrid-anchorage.
This report makes a first step into the formulation of a design-calculation for the mobilised anchor resistance as a function of the length of the geogrid(s) at ultimate limit state. By means of a 1g small-scale physical model and a 2D finite element model (PLAXIS) of the small-scale physical model, the global failure mechanism and soil-geogrid interaction have been analysed. In a series of these experiments, an 18 cm long geogrid anchor was connected to a 30 cm high sheet pile wall and installed in sand in a small transparent test box and loaded with a strip footing load. In addition, experiments were conducted while varying several features, among which the number and length of the geogrid anchors and the location of the slip footing load.

This research focuses on the estimation the failure probability of Shanghai sea-dikes system, taking into account several failure mechanisms. This method follows fully probabilistic approach, in which all relevant parameters for the resistances and the hydraulic loads vary according to specific distributions.

Flooding currently affects 100 million people on average per year globally, and the number is increasing. The performance of dikes under extreme conditions is crucial to societal flood protection. By deploying measurement instruments in and around the embankment, more accurate insights into the actual status of the dike can be achieved that can be used to prevent the failure of a dike.
Despite growing awareness of the potential of dike monitoring techniques and effort put into the development and testing of instruments, implementation of instrumental dike monitoring into regular practice remains scarce. The objective of this thesis is therefore to shed light on the factors that influence the implementation of innovation in dike monitoring practice by: (1) assessing and analysing the barriers and drivers for implementation of innovation in dike monitoring, by studying a case study of novel optic fibre pressure sensors and trying to influence this practice by (2) designing a communication oriented intervention for the development phase that enhances the implementation process.