The (low-lying) coastal zones of the world are facing increased pressure due to climate change and response to human interventions. Sea level rise, intensified storms, and the grey engineered interventions such as seawalls and dykes are contributing to degradation of natural coastal protection systems like mangrove ecosystems. Despite the well-known values of mangrove ecosystems offering natural coastal protection by trapping sediment, storing carbon, and provide many ecosystem services, global mangrove cover has remarkably declined in the recent decades. While many mangrove rehabilitation efforts have been implemented worldwide, many attempts show negative results. These efforts often fail because the lack of understanding the local natural system.

One example of a mangrove-mud coastal system undergoing such mangrove degradation is the highly dynamic system of the Guyana Shield in the northern coast of South America. This dynamic system is known for its offshore migrating mudbanks that play a crucial role in facilitating natural cycles of shoreline expansion and mangrove colonisation. Due to among others the construction of grey-engineering coastal protection and land-use for aquaculture, mangrove degradation accelerates in this area. In order to apply appropriate mangrove rehabilitation methods, the natural system of the Guyana Shield needs to be understood well. Existing studies mainly focussed on site specific problems, leaving a knowledge gap on how to efficiently coordinate mangrove restoration efforts within the larger scale influenced mud dynamics.

This research, therefore, seeks to connect that knowledge gap by exploring how the mudbank morphology and related hydrodynamics influence the effectiveness of sediment-based mangrove rehabilitation methods in the Guyana Shield. The main objective is to identify which type of restoration measure are the most appropriate at the different stages of the mudbank-migration-cycle and to develop a framework that can guide the timing and spatial planning of these sediment-based interventions. To reach this goal, the study combines a extensive literature study, a case study, a conceptual model, and a process-based numerical model.

The study starts with an extensive review of the current state of knowledge on mud dynamics, mangrove ecology, and mangrove rehabilitation techniques. The review highlights the importance of understanding the influence of hydrodynamic forcing as waves and tidal dynamics on sediment transport, the species-specific thresholds for establishment for mangroves, and the importance of applying system-specific approaches for successful mangrove restoration. The insights gained from this review were then applied on the case study, the Guyana Shield. The area experiences a semi-diurnal tidal regime, and is mostly influence by the north-eastern trade winds. Together with the high sediment transport rates originating from the Amazon River there is a net-transport direction westward. This sediment transport is characterised by the movement of offshore migrating mudbanks, creating alternating phases of coastal accretion and erosion along the coast of the Guyana Shield.

Using information from both the literature study and existing pilot projects in the region, a conceptual model is constructed to identify the most relevant variables in the system. These include the hydrodynamic variables, morphological variables, biological and social variables, and lastly the intervention design variables. This conceptual framework serves as a basis for the input for the process-based numerical model using Delft3D, which is used to simulate the different stages of the phases representing the mudbank-migration cycle. From this conceptual framework it becomes clear that the entire system is influenced by the phases related to the offshore mudbank movement and the associated wave conditions. It is assumed that the peak sediment supply and the maximum wave conditions are out of phase, and that the response of the bed level, and therefore also of the mangroves, lags behind the influence of the mudbanks. The presence of a mudbank results in high sediment input and offshore wave dampening, creating favourable conditions for sediment deposition and shoreline expansion, allowing mangroves to colonise.

The Delft3D modelling research was used to test two sediment-based interventions meant for mangrove rehabilitation: by constructing an artificial chenier, and by implementing a mud motor. Both interventions were placed at a different stage in the mudbank-cycle, both intended to stabilise the nearshore zones, either by keeping the sediment there or by promoting sediment transport to the coast. The modelling results show that the effectiveness of these restoration strategies are closely tied to the phase of the mudbank cycle. During the transition from a mudbank to an interbank phase, cheniers can create sheltered conditions that promote sediment accumulation in the nearshore and allow the cheniers to migrate landwards, assuming it proves mangroves a stable substrate for mangrove establishment. For chenier placement, results prove that placing the chenier in the intermediate zone (in this research placed at 2600 m from shore) provides the best outcome in stabilising the nearshore zone. In contrast, in the transition phase from interbank to mudbank, the mud motor proves to be effective by delivering the sediment to the shore and accelerating the bed level growth. For the mud motor results show that the closer the mud is placed to the coast, the more effective the outcome.

The findings in this research confirm that mangrove restoration cannot be approached with a one-fits-all strategy. Instead, the method, timing, and location of the intervention must be carefully aligned with the natural cycle of the mudbank dynamics of the coastal system. By combining the conceptual system understanding with numerical simulation, this research provides a basis for a practical approach for nature-based solution as coastal protection within the Guyana Shield.

The Eastern Scheldt region in the southwestern Netherlands depends on various dams and dikes for coastal protection, including the storm surge barrier (OSK) at the seaside. The OSK was built for both coastal protection and ecological preservation. Initially constructed as a compromise to avoid completely closing off the Eastern Scheldt, the OSK allows tidal exchange flows in normal conditions while it closes during storms. However, the barrier has disrupted the natural dynamics that normally govern a tidal basin, causing erosion of tidal flats as the channels ’demand’ sediment from the flats. These flats are critical for the ecosystem, supporting migratory birds that forage there and playing a crucial role in wave attenuation, which reduces the wave load on dikes. Preserving these tidal flats is therefore beneficial for both flood risk reduction and ecology. Currently, this is achieved by carrying out sediment nourishments on the flats of the Eastern Scheldt to maintain them.

With rising sea levels, the OSK will need to close more frequently, potentially up to 66% of the time with a 2-meter sea level rise. This would disrupt water exchange, threatening food availability for ecosystems and mussel farming while increasing the demand for sediment nourishments on the flats. Frequent closures and ecological pressures raise concerns about the long-term viability of the OSK. Exploring alternatives, such as removing the OSK, could restore sediment exchange, reduce channel sediment demand, and promote tidal flat recovery.

However, uncertainties about the long-term morphological effects of OSK removal persist, making further research essential to evaluate its potential as a sustainable solution for both ecological preservation and coastal protection. This study aims to investigate the long-term morphological development of the Eastern Scheldt following the potential removal of the OSK. To achieve this objective, the following research question will be addressed: What is the long-term morphological development of the Eastern Scheldt, focusing on the tidal flats, when removing the storm surge barrier and under the influence of sea level rise?

To investigate the long-term morphological development of the Eastern Scheldt without the OSK, this study adopts the equilibrium concept for tidal basins. This approach was chosen because it avoids the complexities of process-based models, in which it remains challenging to balance wave erosion and tidal sedimentation over the long term in the Eastern Scheldt. The equilibrium approach predicts aggregated volumes of the flats, channels, and ebb-tidal delta without providing spatial or depth-specific details. The methodology consists of two parts:
1. Data Analysis: Measured volumes of flats, channels, and the ebb-tidal delta are compared with equilibrium volumes derived from empirical equations to assess their alignment. Equilibrium volumes for the scenario without the OSK are then calculated to predict the likely morphological state of these elements.
2. ASMITA Model: To predict dynamic changes influenced by factors such as sea-level rise, the ASMITA numerical model is used. ASMITA simulates sediment exchange among flats, channels, and the ebb-tidal delta by also using the equilibrium concept and estimates morphological trends over time.

The results from the data analysis show that the channels will be closer to their theoretical equilibrium if the OSK is removed, which will reduce the sand demand of the channels and is expected to result in less sediment being drawn from the flats. It is also expected that, due to the removal of the OSK, sediment blockage will disappear between the channels and ebb-tidal delta. Furthermore, from the large deviations between equilibrium volumes and measured volumes of the flats and ebb-tidal delta suggest that the relations used in this research to
calculate the equilibrium volumes should be refined. A good comparison should first be made between the basin on which the empirical equilibrium volumes are based and the Eastern Scheldt. Identifying these differences could lead to more specific equilibrium relations for the Eastern Scheldt.

Results modeled with ASMITA indicate that the flats will import sediment in all scenarios. Sensitivity analysis on these results show that the rate and magnitude of this sediment import largely depend on the sediment concentration entering the basin without the OSK. A reliable estimation of this sediment concentration requires further research (see Recommendations). The ASMITA results also show that the increase in flat volume depends on the balance between sediment import and sea-level rise. Most scenarios indicate an increase in total flat volume. However, for scenarios with extreme SLR rates, the flats in the Eastern Scheldt may eventually
drown, even with the OSK removed.

The expected long-term morphological response of the Eastern Scheldt to removing the OSK is sediment importation to the flats. This can explained by the disappearance of the sediment blockage and the current volume of the channels matching the new equilibrium volume, therefore demanding significantly less sediment of the flats.
The total increase in the volume of the flats depends on the balance between sediment import and sea-level rise. Further research is required to provide an absolute estimate of the total increase in the volume of the flats.

This work seeks to expand on the research done previously by the WOODY group on the ability of vegetation as a form of wave damping. Specifically in this work, we are looking at pollard willow trees (Salix Alba) and the relationship between the motion of the object and the forces it can induce on the wave flow. This was done by testing a range of stiff and flexible conical mimics of three different sizes and varying moduli of elasticity across multiple water levels. The results were compared to commonly used relationships for predicting object motion such as Cauchy, KC, and CAL/KC (Jacobson). Due to the non-constant cross-sectional area of a conical object. However, the relationships could not fully capture the motion. As such a new equation was fitted and derived from the relationships that better captured the motion of the mimics under wave flow. This equation relates the peak forces felt by the objects to the peak deflection. Which can be used as an indicator of wave damping. Along with this number thresholds for motion were also derived from the data. It was found that when an object tip has deflected 2 degrees or less it can be considered completely stiff. If deflecting between 2 and 5 degrees it can be considered relatively stiff, however, high-frequency flow effects can cause discrepancies in the forces between tests.

Mangroves are productive ecosystems. Degradation of mangroves has been observed since the 1970s, due to a variety of reasons. Successful rehabilitation focuses on restoring conditions suitable for mangroves. Sediment availability has been shown to positively impact mangrove growth. Therefore, it can likely play a role in mangrove rehabilitation. This research aims to explore if the rehabilitation of coastal mangroves is possible using a sediment nourishment.

A process analysis is performed, to identify the processes driving sedimentation on a mangrove coast. This analysis uses a schematised, cross-shore, one-dimensional model, based on global data of mangrove coasts. Convex, linear and concave bottom profiles are used. The forcing on the coasts consists of three different wave heights, tidal ranges, and sea level rise rates. A homogeneous mangrove forest is present above mean sea level.

Sedimentation within the mangrove forest is caused by a combination of processes. Waves pick up the sediment, which is transported by the tide. Tidal asymmetry then drives the actual sedimentation in the forest. An increase in asymmetry results in increased sedimentation. Mangroves increase the flood dominance of slack water asymmetry, but also cause an ebb dominant peak flow velocity and duration asymmetry.
Dependent on the tidal range, the influence of mangroves on net sedimentation can either be null, negative or positive.
Sea level rise increases sedimentation within the mangrove, by enhancing slack water asymmetry.

The main tipping point identified is the gradient of the bed slope in cross-shore direction. If the slope becomes milder towards the shore, i.e. a convex coast, this value is negative. If the slope becomes steeper, which is the case for concave coasts, it is positive. The tipping point is when the slope does not change towards the shore. The gradient of the slope then is zero. The net sedimentation is considerably less for concave coasts than for convex coasts.

Sediment nourishments can increase sedimentation in the mangrove forest. Four nourishment designs were simulated, using the same model as for the process analysis. The designs varied in location and achieved depth across the coast.
Three design considerations for a successful sediment nourishment have been identified, which are firstly the obtained bed level by the nourishment, secondly the slope of the original bed, and thirdly the location of the nourishment.
First, the obtained bed level by the nourishment influences the quantity of sediment pick-up. Higher bed levels increase the sedimentation within the mangrove, by increasing sediment mobilisation rates.
Second, the slope of the original bed largely influences the feasibility of a nourishment. Due to mild bed slopes, the construction of a nourishment is difficult and large volumes for a nourishment are required.
Finally, the location of the suppletion should be close to the mangrove. If the nourishment is located far offshore, the sediment is not transported towards the mangrove. Rather, it then is transported away from the coast.
This thesis has shown the rehabilitation of mangroves using a sediment nourishment is possible.

Mudflats are coastal features present in numerous locations around the planet. Depending on the latitude and local conditions, mudflats can be vegetated by salt marshes or by mangroves and play an important role in coastal evolution. Vegetated mudflats can create a remarkable sea defense and their high ecosystem value has been proven by various studies worldwide. In this study, the response of a vegetated mudflat under extreme hydrodynamic forcing is analysed using, as case study, a specific part of the Guyana coast at South America. The sediment dynamics of the Guyana coast are dominated by Amazon River plume that shifts northwards and travels along the coast of South America till the Orinoco River delta in Venezuela. Mudflats are quite wide reaching tens of kilometres in width because of the high supply of sediment by Amazon and the formation of mudbanks along the coast travelling northwards and then westwards. The hydrodynamic environment is relatively mild as Guyana is located far from the track of tropical hurricanes; however swell events can occur caused by the North Atlantic cyclones. Despite of its mild hydrodynamic environment, there are often cases of overtopping of the seawall along Guyana coast every year with a severe and characteristic one been held on October 2005. This was the motive for the mangrove restoration project of the study area in 2011 and for the initiation of this study. The purpose of this study is to analyze the response of a vegetated mudflat under extreme swell and storm events and investigate the impact of vegetation on this response. Furthermore, the impact of the extreme hydrodynamic event on probable damage of vegetation is tested presenting the complete interaction between hydrodynamics and vegetation. The study area is the area of Chateau Margot, southern of Georgetown, where a mangrove restoration project took place in 2011 by planting Avicennia Germinans mangroves and field measurements were applied in the end of 2019 by the researcher Üwe Best. Using the 1-D process based model Mflat, based on an open source Matlab code, a 3.5km portion of the mudflat extending offshore is modelled. Vegetation dynamics and its influence on the flow is part of the model, so a full interaction between hydrodynamics, sediment dynamics, vegetation and morphological evolution can be simulated, establishing a complete bio-geomorphological model. Using field measurements and literature data, the model is calibrated for hydrodynamic conditions and for the vegetation parameters giving a profile in equilibrium. A sensitivity analysis is applied to understand the behaviour of the model and the interaction between various hydrodynamic and sediment parameters and morphodynamics. After calibration, two extreme cases are tested in the model: an extreme storm that could be expected in Guyana coast and an extreme swell event based on the real case occured in October 2005. The Mflat model, after calibration, is able to reproduce a stable profile with mangrove vegetation similar to the observations. Vegetation appears to be quite effective in reducing the wave energy and thereby protecting the coast behind it during the extreme events, while in long term results in accretion of the landward part of the mudflat. The impact of the extreme hydrodynamic conditions on vegetation is difficult to be quantified, but for the extreme cases corresponding to the hydrodynamics of Guyana coast, vegetation is expected to be resilient enough having minor damages that could be restored in a short time period. The very mild slope of the coast is a factor that prevents the bed level of being highly dynamic contributing to the stability of the profile.

Conventional dike reinforcement measures do not take vegetation into account, while vegetation contains wave damping properties. Reasoning for this is that vegetation in general is seen as temporary and hence may be removed in the future. In this case study for the Dutch waterboard WDOD, the wave damping properties of vegetation in a floodplain along the river IJssel (Duursche Waarden) are studied. Duursche Waarden consists of mostly willow species and is adjacent to a dike. It is part of Natura2000 and hence it is a protected vegetation area and not considered to be temporal. A general approach is developed for similar sized (riparian) forests as Duursche Waarden (1.1 km2) to map the vegetation and obtain the vegetation parameters. This approach is also applied to Duursche Waarden. First of all the different vegetation areas within the riparian forest are identified with the help of aerial photos and field observations after which they are prioritised with the help of a Multi Criteria Analysis. The prioritised vegetation areas are divided into uniform and non-uniform areas and studied in detail. Uniform and non-uniform areas are distinguished based on tree species, structure, height and density with the help of field observations, aerial photos and airborne Light Detection and Ranging (LiDAR) data. A representative distribution of the vegetation parameters over the different vegetation areas is obtained with the help of one method. The vegetation parameters interesting for wave damping are the frontal area per volume and the bulk drag coefficient of leafless vegetation. Leafless vegetation is of interest since most extreme storms occur in winter. On top of that leaves seem to have insignificant contribution to wave damping in the full scale physical experiments of white willow trees conducted in the Delta Flume at Deltares. These experiments were performed in 2018. A new definition is introduced for the frontal area per volume. The frontal area density distribution over the height is estimated with the help of point clouds retrieved from TLS measurements and validated with hand measurements and studies of similar vegetation. Two methods are used in estimating the frontal area with the help of literature: the alpha shape and grid method. These methods are used for merged point clouds from Multiple Scanning Stations (MSS) and a point cloud from a Single Scanning Station (SSS). The SSS method includes a shadowing correction factor. Finally, the values of the frontal area per volume are chosen based on assessing the outcomes of the MSS method, SSS method and hand measurements. The bulk drag coefficient is estimated using selected values from literature. Dense vegetation contains relatively higher values for the vegetation parameters than sparse vegetation. This will result in more wave energy dissipation and hence more wave damping for dense vegetation. The frontal area per volume of sparse to moderate dense woody vegetation (values on average of about 0.01-0.20 m-1) in uniform areas is believed to estimated best and most efficiently with the MSS method. In non-uniform areas hand measurements are believed to be estimated best and most efficiently by hand measurements. The frontal area per volume of dense woody vegetation (values on average greater than 0.20 m-1) is most uncertain. Therefore, both hand and TLS measurements (with the SSS method) should be used to estimate the frontal area per volume. The wave attenuation by vegetation is estimated using the numerical wave model SWAN 1D and 2D computations including and excluding vegetation using the obtained vegetation parameters. No currents are included. Hydraulic conditions of Hydra-NL calculations using Bretschneider are used for both SWAN 1D and 2D computations. A comparison between Hydra-NL and SWAN 1D computations including model uncertainty for exactly the same conditions show similar outcomes for SWAN. SWAN 1D computations showed wave attenuation due to vegetation with a magnitude of 0 to about 44 cm for all dike locations adjacent to Duursche Waarden. SWAN 2D computations without vegetation show significantly lower outcomes than 1D computations without vegetation: on average about 12 cm. This difference is explained by refraction and directional spreading resulting from the spatial variability in water depth and fetch of the studied area. Therefore the studied area is believed to be better described by 2D computations. One combination of the wind direction and water level is proven to be governing for all dike locations. Following 2D computations, the failure mechanism ‘erosion of the outer slope’ with a return period of 66666 year results in an estimated maximum wave height of 77 cm for dike locations adjacent to Duursche Waarden. This is a reduction of about 23 cm compared to the results of Hydra-NL. Indicative calculations suggest that dike reinforcements are still needed at Duursche Waarden. The wave damping is estimated to be 16 to 24 cm at dike locations adjacent to relatively large vegetation areas of sparse to dense vegetation. Dike locations at which the significant wave height is the greatest are called critical dike locations. The wave damping for these critical dike points is estimated to vary between 4 to 7 cm. In a report by Deltares an overview is made of promising wave damping foreshores in the Netherlands. Rough estimations show possible wave damping at Duursche Waarden of about the same order of magnitude as found in this study. Also studies on similar vegetation show significant greater values for the wave damping, suggesting rather conservative than optimistic outcomes in this study.

Degrading mangrove forests and coinciding erosive coastlines is an urgent global concern. Mangroves are essential for their interaction with hydrodynamic and sediment processes at mangrove-mud coasts. Earlier on, solutions were sought in building ’hard’ structures, such as concrete sea walls, to lower incoming wave energy and enhance sedimentation to restabilize erosive coastlines and bring back mangroves. As these approaches proved to be counterproductive and even accelerate destabilization of the coastline, nature-based solutions might provide a new path to a durable solution. A pilot project was initiated in Demak, Indonesia, where several permeable brushwood and bamboo dams were constructed near the receding coastline. The open structure of the dams allows sediment to flow through, while they decrease wave heights by dissipation. This creates calmer conditions behind the dams and allows mud to settle. The deposition of fine sediments enhances a rise in nearshore bedlevel and provides nursery ground for mangroves to reestablish, realizing a first step towards rehabilitation of the mangrove ecosystem and restabilizing the coastline. A conceptual 2DH process-based model, using Delft3D FM, was created to analyse the effect of permeable structures under changing boundary conditions at various shorelines. Three boundary conditions were varied to see the influence on dam performance: wave height, wave direction and suspended sediment concentration. A decrease or increase in wave height resulted in similar rise in bedlevel elevation behind the dams. Without the dams, an increase in wave height increased the tidal flat elevation and steepened the foreshore, inducing a concave profile shape. Placing the dams on the tidal flat induces extra rise in elevation, but won’t mitigate the erosion of the foreshore. Smaller wave heights tend to reshape the profile towards a more convex profile. When dams are implemented on, an increase in bedlevel behind the dams occurs. The waves stir up sediment at the tidal flat boundary which are redistributed by the tidal currents forming a more convex profile. The dams could be placed best close to the shoreline to allow for the natural redistribution of the sediment when at the same time induce a rise in bedlevel for mangroves to reestablish. Altering the nearshore sediment supply affects the dam performance significantly. The dam performance increases for lower sediment supplies. Dams reduce erosion due to decreased sediment input, but it is likely a short-term solution. For higher sediment supplies, the coastline can more effectively restore by itself and the dams reduce in efficacy. The model results show an increase in dam performance for increasing wave angles (shore-normal to shore-parallel). The bed shear stress is decreased more effectively for smaller wave angles, but also reduce the sediment concentration behind the dams. With the many distinctive boundary conditions at mangrove-mud coasts in mind, the simplified model setup is made easily adaptable to enable future use of the model. Based on the model setup for Demak and the model results in this research, an improvement on the computational grid is suggested before applying the model to other coastal sites.

The increasing frequency and intensity of extreme events due to global warming and climate change is increasing flood risk. To act, rather than react, nature-based solutions (NBS) involving vegetation and wetlands are being explored on top of conventional solutions like dikes. WHY? There was a dire need for global study quantifying the potential of vegetation in reducing flood risk and eventually make a decision support tool which enables quick assessments about flood risk reduction in a vegetated hydrodynamic system. WHAT? The developed tool can predict flood risk anywhere in the world without rigorous modeling through user defined conditionalization of in-situ hydrodynamic or vegetation characteristics. HOW? Multivariate dependence among parameters of schematized system can exhibit characteristics of vegetated hydrodynamics. To ensure global representation of vegetated hydrodynamics a copula-based multivariate stochastic model has been developed which caters global ranges of each parameter, their probability distributions and the inter-parameter dependencies through ranked correlations. Numerical modeling has been carried out through XBeach non-hydrostatic model by resolving full spectrum of high and low frequency waves. A non-parametric Bayesian network-based flood risk prediction tool has been developed from the synthetic dataset developed from the simulations. SO? Bulk results conclude that saltmarshes attenuates waves by 87% and mangroves by 94% as a mean value. Wave attenuation, flood risk reduction and wave run-up manifests maximum dependence on offshore wave height, water depth, drag coefficient, vegetation height, frontal width, and forest length and least on offshore slope and vegetation density. NOW? The flood risk prediction tool would help decision makers in implementing NBS, in making better informed decisions about early warnings and policy making related to flood risk reduction and climate change adaptation by incorporating vegetation. NOVELTY? To the author's knowledge no such study exists which captures natural variability of hydrodynamics and vegetation together in a probabilistic model over global scales. Additionally, no such study exist which applies non-parametric Bayesian networks to predict flood risk. The dependence modeling of global vegetated hydrodynamic environments is also unique which skims out the most critical parameters.

Global flood exposure simulations show that about 600 million people, of which 320 million in urban areas, are at risk to the impacts of global sea-level rise and changing storm intensity and frequency. Increasing availability of data and computational efficiency enables to assess flood hazard on a global scale. Implementation of salt marshes and mangroves as nature based flood defences has gained strong interest in the field of hydraulic engineering during the last decade, because these ecosystems can be an innovative, sustainable and cost-effective supplement to manmade traditional coastal protection measures. This thesis focuses on wave damping by salt marshes and mangroves and aims to map flood hazard reduction by foreshore vegetation on a global scale.

Wave attenuation by foreshore vegetation is accessed using transects which are aligned perpendicular to the Open Street Map (OSM) coastline. The study area contains in total 495361 transects, which have an intermediate distance of roughly 1 km and are individually assessed. The assessment of each transect involves construction of the foreshore profile, derivation of vegetation presence and the corresponding vegetation type, determination of the governing hydrodynamic conditions and computation of wave propagation over the foreshore. Wave damping by foreshore vegetation is determined by comparing the wave height at the end of the vegetated zone with a bare foreshore situation. The analysis is based on topobathymetric data from the Global Interidal Elevation map (20 – 30 m resolution, 1 m vertical accuracy) and a merged set of MERIT elevation data (3 arc-seconds resolution, 2 m vertical accuracy) and GEBCO bathymetry data (30 arc-seconds resolution, 10 m vertical accuracy). Vegetation presence is based on the VegGEE map (resolution 10 -30 m) and the cover type is based on the Salt marsh map, Mangroves, GlobCover or CLC. Wave characteristics are derived from ERA-Interim reanalysis and extreme levels from the Global Tide and Surge Model (GTSM). The nearshore wave height is based on a depth limited criterion and wave propagation over the derived foreshore is determined using a dataset of XBeach pre-runs.

The results of the global assessment show that 31% of the coastline in the study area (between the Arctic circle and -60 degrees South), is vegetated, of which more than half has a vegetation width that is larger than 100 m and 5% has a vegetation width exceeding 1000 m. Along 5% (15%) of the studied (vegetated) coastline is a significant wave height reduction observed of at least 30 centimetres. The performed global flood hazard reduction assessment is unique, as it uses global open source data to express quantitatively wave damping by salt marshes and mangroves on a global scale. The results show the effect of foreshore vegetation in terms of wave attenuation, reduced dike height and the potential social impact. Based on the performed analysis can be concluded that foreshore vegetation has a high potential to mitigate flood hazard at various areas around the globe.

The aim of the Building with Nature (BwN) design philosophy is to improve on a traditional approach for infrastructural projects by utilising natural processes to create benefits for society and nature. In a fast-changing world where climate action is becoming increasingly important, there is need for an innovative approach in large infrastructural projects where nature is not considered as an obstacle, but stimulated and used in a sustainable way. The BwN design philosophy offers the opportunity to realize this improvement. This research first aimed to create an evaluation framework of (international) standards and goals to identify opportunities for improvement of a port masterplan and to get a better understanding of the need for sustainable port development. Included in this evaluation framework are, amongst others, the Port Vision2030, the Corporate Social Responsibility statement and the international strategy of the Port of Rotterdam (PoR). On the basis of these visions and standards, the corporate governance of the PoR was tested by conducting an informal opinion poll amongst twenty colleagues at the PoR (International, Environmental Management and Port Development). A practical example of a traditional port development project that can be improved by applying BwN is the Kuala Tanjung (KT) Port-Industrial complex at Sumatra, in Indonesia. This port development project is still in its initiation phase where a first master plan is proposed. Since the goal of the Indonesian government is to build a world-class port, international and sustainable standards apply. This project was used as a case to identify opportunities to improve a traditional master plan by applying a BwN approach. The evaluation framework was applied to the current master plan of KT to check whether this project meets the requirements for international port development, in particular from a nature/social point of view. It is concluded that the current design mainly focuses on the functional requirements of the port, proposing mitigation and compensation measures against the negative social and environmental impact of the port development. The BwN philosophy, on the other hand, prescribes a thorough understanding of the natural system emphasizing on the positive effects of the project for stakeholders and nature, to create a win-win solution. After applying the general evaluation framework, it became clear what aspects in the current master plan should be improved. A literature study of applied BwN solutions resulted in an onshore and offshore alternative for the port development including several BwN solutions. Together with experts involved in the KT project, it is concluded that the onshore alternative is more realistic (from a functional point of view), while still offering opportunities for applying the BwN philosophy. In the current natural system of KT the mangroves offer various important ecosystem services. In addition, it is concluded that the breakwaters proposed by the current master plan form a large part of the CAPEX. Consequently, a solution is proposed where mangroves are integrated in the design to attenuate waves and enhance nature at the same time. To test whether this BwN solution is realistic, a preliminary feasibility study has been executed. The results of a mangrove coastal protection program at Demak (Java, Indonesia) and various scientific articles (Ecoshape BwN Guidelines, 2018) about rehabilitation programs for mangroves have been used to set up a general checklist with habitat requirements for mangroves. These requirements were compared with the local conditions at KT and recommendations for creating these conditions at the breakwater location were given. According to the checklist, the site at KT appeared to be suitable for mangrove establishment. This resulted in preliminary mangrove breakwater designs for various depths. In addition, the effect of the BwN solution on the phasing of the adapted master plan was determined, rough cost estimates were made and the implementation risks were identified. According to these conditions, the mangrove-based breakwater appeared to be technically feasible for the first 2000 m of the shallow part of the south-eastern breakwater at KT. Finally, the evaluation framework was applied again to check if the current master plan of KT has been improved (read: less dilemmas occurring from deviating standards in Indonesia) and a general advice is given on the applicability of the selected BwN solution to other ports in Indonesia and (sub)tropical zones of the Asia Pacific region.

Om aan de woningvraag te voldoen werd in 2000 de bouw van eilandengroep IJburg gestart in het IJmeer-Markermeer. IJburg bestaat uit twee fases die achtereenvolgend aan elkaar zouden worden aangelegd. In 2002 betrokken de eerste bewoners hun huizen op de eerste fase van IJburg. Momenteel is het laatste eiland van fase 1 nog onbebouwd en is gepland dat in 2023 wordt gestart met extra bebouwing van huizen op de tweede fase. Echter, verdere beslissingen met betrekking tot de gehele aanleg van IJburg in de tweede fase is op dit moment nog uiterst onzeker. Omdat het huidig waterbouwkundig ontwerp nog steeds uit gaat van de definitieve situatie van fase 1 en fase 2, is onderzoek naar het effect van het uitblijven van het Buiteneiland op de waterveiligheidsstatus nodig. Daarnaast is vanaf januari 2017 een nieuwe waterkeringsnormering en veiligheidsfilosofie voor dijken, dammen en duinen in Nederland wettelijk van kracht. Hieruit is de volgende hoofdvraag ontstaan voor het onderzoek: “Wat is het effect van de implementatie van de nieuwe normering voor primaire waterkeringen en het uitgestelde besluit van B&W voor het eiland Buiteneiland op de waterveiligheidsstatus in IJburg, welke BwN alternatieven bestaan er om de waterveiligheid in IJburg te garanderen, en welk alternatief wordt geadviseerd voor Gemeente Amsterdam?” Om de waterveiligheidsstatus van IJburg te beoordelen worden scenario’s opgesteld waarbij de twee ontwikkelingen in acht worden genomen: uitgesteld besluit met betrekking tot het aanleggen van Buiteneiland en de implementatie van de nieuwe normering voor primaire keringen in Nederland. De waterveiligheidsstatus wordt beoordeeld aan de hand van het berekenen met een vereiste kruinhoogte volgens Ontwerp Instrument 2014. De berekeningen worden uitgevoerd aan de door Rijksoverheid beschikbaar gestelde programma’s als Hydra Modellen en PC Overslag. Geconcludeerd kan worden dat de waterveiligheidsstatus onveilig en ‘worst case’ scenario als 0-alternatief wordt gesteld bij het ontwerpen van de BwN alternatieven. Om de eisen, randvoorwaarden en wensen, oftewel oplossingsrichtingen, voor de alternatieven vast te stellen wordt er een gebiedsanalyse, ecologische analyse en een stakeholderanalyse uitgevoerd. Hierbij wordt onderscheid gemaakt tussen de primaire functie waterveiligheid en de secundaire functies ecologie en recreatie. Uit de oplossingsrichtingen ontstaan een vijftal oplossingen, genoemd: IJmeer Wadden, Zanddam, Zandeiland, Groenstrand en Natuureiland. In de waterbouwkundig ontwerpen van de BwN alternatieven voor dijkverhoging wordt uitgegaan van natuurlijke elementen zoals wind, stroming, flora en fauna waardoor voordelen kunnen worden geboden voor zowel natuur, recreatie als kostenreductie. De alternatieven berusten op twee verschillende principes om de waterveiligheid te waarborgen zonder dat de kruinhoogte van de primaire waterkering moet worden verhoogd: dempen van golfslag door infrastructuur waarbij een schaduwzone in de IJburgbaai wordt gecreëerd en aanleggen van een zandige vooroever voor de huidige kering. De dagelijkse windcondities spelen een belangrijke rol in de ontwerpen betreffende onverdedigde zandige taluds. De zandige taluds bieden zowel voordelen voor natuur (land-waterovergangen en rust- en ruiplaatsen voor watervogels) als recreatie (windsurf-, kitesurf-, zwemmogelijkheden en creatie van stadsstrand). Daarnaast is het gebruik van zand in de ontwerpen gewenst doordat zand beschikbaar komt uit een ander project binnen IJburg. Hierdoor worden kosten gereduceerd en werk met werk gemaakt. Naast zand is er ook nagedacht om met slibmateriaal te werken. Het slibmateriaal is aanwezig in het systeemgebied en overmatig slib is ongewenst door het negatieve effect op de waterkwaliteit. Door het opnemen en verwerken van slibachtig materiaal wordt de waterkwaliteit verbeterd, natuurgebied ontwikkeld en een oplossing geboden op de waterveiligheidsproblematiek. Een laatste belangrijk aspect om voordelen te behalen in tegenstelling tot traditionele dijkverhoging, is het inspelen met het ontwerp op mogelijke beleidsplannen betreft de configuratie van eilanden. Dit wordt gedaan door het creëren van tijdelijke ontwerpen met een mogelijkheid tot permanent karakter.