The functionality of existing coastal defence structures designed for depth limited wave conditions are at risk due to climate change. Sea level rise could result in stronger wave loads acting on the shore thus reducing the effectiveness of existing coastal structures. Therefore climate adaptation measures are required to ensure that interventions to protect the coastline do not become obsolete. A viable option is to reduce the wave loads before they arrive to the shore. This can be achieved through either increasing the foreshore via sand nourishments or through the construction of offshore breakwaters to attenuate wave energy. In recent times, sand nourishment has become increasing popular as a soft engineering solution to preserve coastlines. However sand nourishments are not permanent and more sediment has to be deposited at regular intervals depending on the rate of erosion at the coasts. Costs of sand nourishments may also rise to unsustainable levels if sea level rise result in elevated rates of erosion. The construction of artificial reefs in front of nourished beaches brings a twofold benefit: they promote marine life and biodiversity whilst simultaneously acting as submerged breakwaters to dissipate wave energy before it reaches the coast. The effective design of a dual nature based system consisting of a nourished beach and artificial reefs require proper and accurate understanding of the hydrodynamic processes that occur at the beach and in the coastal waters. It would then be critical to know how the waves would interact with the artificial reefs and subsequently the beach. This study built on previous research to expand the knowledge of the behaviour of waves and their interaction with artificial reefs. Through physical modelling tests, the study investigated whether the distance between the artificial reef and the beach would affect the extent of wave energy dissipation by such structures. This would be quantified by the wave transmission coefficient. The influence of this same distance on structure induced wave setup between the reef and beach will also be studied. Physical modelling tests were conducted in a wave flume , with a submerged artificial reef tested at three positions relative to a nourished beach, located at distances of 4.80 m, 9.20 m, and 13.70 m from the shoreline. A total of 132 test cases were carried out, varying the significant wave height (𝐻𝑚0 = 8– 20 cm), wave steepness (0.015 ≤ 𝑠𝑚−1,0 ≤ 0.040), and relative freeboard (−1.875 ≤ 𝑅𝑐/𝐻𝑚0 ≤ 0.625). Wave transmission and structure-induced wave setup were analysed and compared with existing empirical formulas. The combined use of a permeable low crested structure with the distance between the structure and the beach as a variable, to study wave transmission and structure-induced wave setup, represents a configuration which has not been clearly addressed in existing literature. This study has thus provided novel insights into this area. The results indicate that, within the tested range of conditions, the distance between the artificial reef and the beach does not have a significant influence on the wave transmission coefficient 𝐾𝑡 nor on the structure-induced wave setup 𝛿/𝐻𝑚0. The relative freeboard 𝑅𝑐/𝐻𝑚0 was identified as the dominant parameter governing wave transmission. It was concluded that within the tested conditions, designers of artificial reefs placed in front of nourished beaches need not place significant attention on the reef-to-shore distance as a primary design parameter. Instead, greater focus should be placed on the local freeboard, wave climate, and reef geometry, which are the parameters shown to govern the hydrodynamic effectiveness of such structures. ... Read more

Temporary flood protection measures are sometimes considered when flood defence structures fail to meet safety standards and full reinforcement is planned but not yet implemented. This thesis develops and applies a probabilistic decision framework to evaluate under which conditions such temporary measures are economically justified or required from a safety perspective during the interim period before reinforcement.

The framework combines a time-dependent cost–benefit analysis with a Loss of Life (LoL) safety threshold. Cost benefit ratio is calculated as a function of failure probability, potential damage, and the remaining time until reinforcement. The economic feasibility of temporary measures is evaluated by comparing their intervention cost with the accumulated avoided expected damage over the planning horizon. In addition, a Loss of Life criterion is included as an override condition to ensure that temporary measures are required whenever individual safety levels become unacceptable within ALARP principle, regardless of economic performance.

Application of the framework to the dike segment between the Maeslantkering and Rozenburg demonstrate how the proposed decision framework can be applied to a real-world case with a planned reinforcement horizon. The case study is used to illustrate the operational use of the framework rather than to derive generalised conclusions. The results show how the relative importance of economic and safety-based criteria can be explored within a single case through sensitivity analysis, without implying general dominance across different systems.

Extension of the analysis to a set of generalised polder archetypes in Chapter 5 explores how decision outcomes change across different combinations of system characteristics, including damage levels, baseline flood probabilities, and planning horizons. Uncertainty in key parameters, such as flood probability, damage magnitude, and probability reduction, can significantly shift decision boundaries. Decision maps and related visualisations prove useful for identifying regions where temporary measures are clearly justified, clearly unjustified, or sensitive to assumptions. These tools support transparent reasoning about trade-offs rather than prescribing a single optimal decision.

Overall, this thesis shows that temporary flood protection decisions can be evaluated in a structured and transparent way by explicitly linking cost, risk reduction, and time until reinforcement. The proposed framework supports consistent interim decision-making under uncertainty and is particularly relevant for managing non-compliant flood defences during transitional periods. ... Read more

This study investigates how hydraulic and meteorological variables act together to affect dike stability, with emphasis on inner-slope failure during extreme hydrometeorological events. The variables influencing dike stability are first identified through a literature review, after which their correlations are examined and analysed using copula theory. The effect of these correlations is then assessed in more detail by applying a groundwater model developed with Pastas and performing slope stability calculations using the Bishop method.
The analysis focuses on the period from December 2023 to January 2024, when the Netherlands experienced high cumulative rainfall, elevated river discharges, and restricted outflow due to sea storm surges, leading to prolonged high water levels in the IJsselmeer–Markermeer system. The case study is a lakeside dike along Markermeer between Hoorn and Enkhuizen (about 17.8 km), where data availability enables detailed hydrological and geotechnical modelling. Two cross-sections (raai_2 and raai_3) are instrumented with multiple observation wells from phreatic to deep sand layers. Inputs combine hourly lake levels from Krabbersgat Zuid and the nearby Drieban pumping station, hourly precipitation and daily evapotranspiration from Berkhout station, and local groundwater measurements from 10 Nov 2023 to 25 Feb 2025. These data are used to calibrate and validate Pastas groundwater models and to evaluate slope stability for representative hydraulic loading conditions.
The literature indicates that phreatic levels around Markermeer and IJsselmeer are governed by external hydraulic loads, climate, internal soil properties, dike geometry, and local lake dynamics. Using statistical analysis, copula modelling, and time-series groundwater simulations, this study examines how precipitation and lake level jointly influence the phreatic surface within the dike. Results show a moderate positive correlation between cumulative local precipitation and lake water levels. Copula models, particularly the BB8 family, capture asymmetric dependence between rainfall and water level, highlighting an increased likelihood of joint extremes.
For stability evaluation, observed groundwater data were first used as input to D-Stability to compute the factor of safety (FoS) over selected periods. This “dependent” case reflects the real, correlated relationship between precipitation and water level and shows a moderate negative correlation with FoS, meaning increases in either driver reduce stability. An “independent” case is then constructed by generating a new water-level series from the fitted bivariate copula using conditional sampling with rank-exact back-mapping, so that water level is statistically independent of precipitation while preserving the marginal (univariate) distributions. The Pastas model is re-fitted with this synthetic water-level series to produce new groundwater heads, and FoS is recomputed. Under the observed (dependent) case, peak external water levels coincided with prolonged high precipitation, producing higher phreatic levels and a lower minimum FoS (1.745). When the same marginals were used but the drivers were made independent, peak water levels were lower and the minimum FoS improved (1.768). By evaluating the correlation, the dependent case shows stronger negative correlation for both precipitation (-0.67) and water level (-0.49) versus FoS. In the case of independent variable, the correlation between water level and FoS strengthened to −0.85, while the correlation between precipitation and FoS weakened to −0.18.
Based on the previous results, it can be concluded that during the wet season, the correlation between precipitation and water level leads to a more conservative outcome, expressed as a lower factor of safety (FoS) for dike stability. This finding is consistent with real-world conditions, where periods of higher rainfall typically occur together with higher local lake water levels caused by runoff from around the lake, direct rainfall itself, and polder drainage pumping into the lake. This conclusion is based on the assumption that the water level dataset used in this study represents local water level observations, where in reality the actual local water level at this specific dike section may differ slightly depending on wind magnitude and direction. The main recommendation for dike assessment based on this study is that the correlation between precipitation and water level should be explicitly considered in stability analyses, since neglecting this dependence may underestimate phreatic levels within the dike and result in a less conservative estimate of the factor of safety.
... Read more

Mangrove ecosystems play an important role in (sub)tropical coastal zones by providing services such as carbon storage, biodiversity support, and natural protection against erosion and flooding. Their dense root systems trap sediment and reduce wave energy, contributing to shoreline stability. Despite these benefits, global mangrove areas have declined rapidly in recent decades, mainly due to deforestation and coastal retreat. In response, various restoration measures have been implemented, including the construction of permeable structures along eroding coastlines. These structures aim to reduce hydrodynamic energy and promote sediment deposition, creating conditions suitable for mangrove re-establishment. However, they do not always succeed in providing the required sediment accumulation.

This study focuses on a breakwater in the study area, located along the coast of Bạc Liêu, Vietnam. The area has a concave bed profile with limited wave energy dissipation and short inundation-free periods, which, together with net erosion, hinder both mature mangrove stability and seedling establishment. Hydrodynamic forces such as longshore currents, tidal flows, and waves generate bed shear stresses that resuspend sediment and limit sediment deposition near the shore. The existing permeable breakwater fails to provide the sheltered conditions needed for mangrove survival and recovery. As part of the Mangrove Living Lab project, this study investigates how the spatial design of the existing Pile-Rock Breakwater (PRBW) influences hydrodynamic processes relevant to sediment transport and deposition, focusing on minimising the maximum bed shear stress near the mangrove fringe. The considered spatial design parameters of the permeable breakwater are the gap width and the distance to shore. Field measurements and numerical modelling using Delft3D are combined to assess current conditions, evaluate the effectiveness of the existing design, and explore potential improvements.

Results show that narrower gaps reduce wave energy in the sheltered area but concentrate flow through the gaps, locally increasing velocities. Placing the breakwater further offshore allows more space for dissipation and reduces bed shear stress at more exposed areas behind the gaps, but also increases the incoming energy near the mangroves in more sheltered zones. The recommended spatial design requires a balance of these effects, with the breakwater placed approximately 70 metres further offshore and featuring narrower gaps to enhance shelter and reduce resuspension. Recommendations for future work include more detailed modelling including diffraction, long waves, and morphodynamics, as well as gathering more data from the area to improve understanding. Further research should also investigate simultaneous adjustments of the spatial design parameters and explore alternative breakwater types.

Overall, this research shows the complexity and importance of a site-specific breakwater design. Optimising the spatial layout offers potential to improve the breakwater’s effectiveness, but further research is needed to improve the design and develop a more thorough understanding of the local conditions and ongoing coastal processes. These improvements are essential to support sedimentation and establish stable conditions for mangrove survival and long-term restoration along the coast of Bạc Liêu. ... Read more

Tokyo Bay likely faces increasing risks of typhoon-induced flooding as sea level rises and typhoons intensify under climate change. A storm surge barrier (SSB) has been proposed to mitigate this risk, yet little investigated. This study presents initial considerations regarding a potential configuration for a SSB protecting Tokyo. The barrier’s requirements and location are identified through boundary conditions and a criteria analysis, respectively. For dimensioning, typhoon parameters (wind speed, atmospheric pressure, wind direction, and precipitation) are derived through probabilistic analysis. A one-dimensional model evaluates water levels during a typhoon to assess the potential SSB location and dimensions. Finally, key SSB dimensions are derived using rules of thumb. Preliminary results suggest that an effective SSB could be located between Haneda Airport and Disneyland. The concept comprises ungated caisson sections separated by a navigational gate and flow inlets equipped with flap gates, offering both storm surge protection and runoff storage capacity. However, this study represents an initial, system-wide assessment at a relatively coarse level. Despite simplifications, the study finds river-ocean interaction crucial for Tokyo, as the surge could induce river flooding during typhoons. ... Read more

The completion of a fourth sea dike (Binh Minh 4) in Kim Đông, Ninh Bính, in Vietnam will reshape local hydrodynamics and will result in land reclamation. Thus, the balance between mangrove forest health, flood protection, local livelihoods and development goals will be changed. This report addresses the impacts and fills knowledge gaps regarding the completion of this fourth dike on hydrodynamics in Kim Đông, and examines hydrodynamic, ecological, governance, and social factors in relation to the mangrove ecosystems in the region.

To achieve this, a governance analysis and system analysis are combined with a hydraulic analysis and a conceptual hydrodynamic model in Delft3D. This approach is supported by literature and institutional reviews, expert interviews, a community survey, and hydraulic data, including satellite-derived wave and wind records, as well as field measurements. Together, these elements shape the model set-up, boundary conditions and interpretation. The modelling framework compares a baseline situation without a dike with two with-dike scenarios, simulating both storm and regular weather conditions. Physical changes in the model are linked to drivers of ecological change, allowing an assessment of their impact on mangrove forests and socio-economic conditions in the area.

Findings from the conceptual Delft3D model indicate that the completion of a fourth dike is likely to reduce tidal connectivity and sediment supply to the enclosed area, leading to longer inundation times and lower water levels. These change in conditions drive mangrove squeeze, reducing habitat, shelter and carbon storage potential. At the same time, land reclamation creates development opportunities for aquaculture. Interventions to mitigate the effects of the fourth dike are presented using a COCD box, and evaluated via a multi-criteria analysis. Suitable interventions are further elaborated on their trade-offs and implementation process.

Decision-making in Vietnam, and in Kim Ðông especially, is highly hierarchical, which limits involvement of local authorities and residents even though they are most affected. Conflicting priorities among sustainability, economic growth and climate adaptation further complicate this involvement in decision making. Additionally, limited data availability and experience with nature-based solutions also constrain adaptive management and long-term monitoring. With this in mind, four potential interventions are assessed: adaptive gate management, mangrove co-management with incentives, sustainable aquaculture \\certification, and a digital monitoring platform. No single measure resolves all challenges. However, co-management with incentives and sustainable aquaculture emerge as promising options that couple ecological restoration with socio-economic benefits, supported by adaptive gate operations and a digital platform to improve coordination and transparency. ... Read more

Under the Dutch Flood Protection Programme (HWBP), extensive reinforcement of primary flood defences is planned by 2050. However, progress is slow and costs are exceeding expectations. Current reinforcement strategies face significant challenges: inward reinforcement is constrained by spatial limitations, while construction-based solutions are costly and lack flexibility in light of climate policy uncertainty. Outward dike reinforcement (ODR) offers an alternative, but its application is currently restricted by regulations under the Rivierkundig Beoordelingskader (RBK). In particular, the ‘1-mm rule’ requires that any hydraulic impact be mitigated to within 1 mm, often necessitating substantial mitigation works that render ODR disproportionately complex and expensive, and thus rarely applied despite its promise.

This thesis investigates whether ODR can be considered a technically feasible and cost-effective alternative under a relaxed RBK framework, in which its hydraulic impact is absorbed by the flood defence system, eliminating the need for mitigation measures. In doing so, it aims to support engineering practice through preliminary design insights, while also identifying regulatory elements that may warrant reconsideration to facilitate broader applicability of ODR.

Four self-designed conceptual dike variants are created to assess the hydraulic impact, technical feasibility, and cost-effectiveness of ODR under varying conditions. The designs are developed at a preliminary level and represent inward, construction-based, and two outward variants with 5-metre (Tuimeldijk) and 20-metre expansions, applied to a hypothetical reinforcement of the southern Waal banks. The outward variants define a bandwidth for evaluating the effects of expansion, providing a framework for generalising ODR performance. The hydraulic impact is analysed using a simplified 1D compound channel model to identify influential parameters and general trends, complemented by detailed D-Hydro Suite simulations for site-specific effects. These results inform the feasibility assessment, which uses exceedance-based limit-state formulations of the main failure mechanisms to evaluate dike performance and potential functional lifetime reduction (FLR). Cost-effectiveness is assessed through short-term design comparison and long-term net present value (NPV), using a life cycle cost (LCC) analysis that incorporates adaptability and feasibility outcomes.

The expected water level difference (WLD) due to ODR in the Waal River ranges from 0 to 4 cm, depending on the application and floodplain characteristics. Two design graphs are presented, offering first-order estimates of WLD for 5-metre and 20-metre expansions. The relationship between expansion and WLD is observed to be approximately linear, enabling interpolation across the design graphs. Bottlenecks in the river system show the highest WLD sensitivity, as narrow and smooth floodplains amplify hydraulic impact. Continuous reinforcement results in higher WLD than discrete interventions, although short interventions are penalised by steep local water level gradients and cause larger WLD per unit of intervention length. Adaptation lengths required to absorb WLD effects span several tens of kilometres, but depend strongly on endpoint definition.

ODR is technically feasible considering the performance of affected dikes. Of the main failure mechanisms, only overflow and piping are influenced by the hydraulic impact of ODR, resulting in an estimated FLR of approximately two years if applied in the Waal. Dike stability is never compromised while WLD remains below 10 centimetres, and effects on overtopping can be neglected. FLR is primarily governed by the annual climate-change-induced increase in hydraulic load, the magnitude of WLD, dike subsidence (for overflow), and the additional robustness provided by the blanket layer or sheet pile (for piping). If these structural elements include a buffer equal to or half the WLD, respectively, FLR due to piping is unlikely. Two strategies are considered to address FLR: adding an asphalt layer to all affected dikes or accepting the reduced lifetime.

The cost-effectiveness of an optimised ODR design is comparable to, and under certain scenarios, proves more cost-effective than construction-based reinforcement over a 100-year horizon, while offering greater adaptability where inward reinforcement is either unfeasible or prohibitively expensive. This is particularly true when recycled soil is used and in light of uncertainties regarding spatial constraints on the inner slope, sheet pile prices, and functional lifetime. The optimised design should minimise outward extent and material use, in line with minimal designs such as the Tuimeldijk variant, while ensuring sufficient resistance against piping without requiring sheet piles. It should be applied over stretches exceeding 10 kilometres, as cost-effectiveness increases with length. Choosing FLR proves to be the more cost-effective strategy of the two, as uncertainties associated with FLR have limited impact on overall cost-effectiveness. In short-term cost comparisons, ODR is only cost-effective if the design closely resembles the Tuimeldijk variant or incorporates recycled soil. Otherwise, the excessive soil volumes make it less competitive than non-outward alternatives.

These findings demonstrate that ODR, where the flood defence system absorbs the hydraulic impact, can be a technically feasible and cost-effective alternative to conventional reinforcement strategies, provided that RBK regulations are relaxed. It is therefore recommended to integrate this variant of ODR as the final step in the current line of reasoning for riverward reinforcement upheld by the HWBP.
To enable practical application, it is proposed to relax the hydraulic limit in the RBK to 2 centimetres. This adjustment would allow a broader range of ODR configurations to be assessed using the presented design graphs, while maintaining cost-effectiveness and feasibility.
Additionally, the 1-mm rule should serve as a threshold for defining adaptation length, provided a clear backwater formulation is integrated into the RBK. Further research is required to confirm that other regulatory conditions within the RBK are upheld under this revised hydraulic limit. This would allow ODR to serve as an additional alternative in complex situations, helping to reduce project complexity today while preserving flexibility for future challenges.
... Read more

This report studies the ability of flood defences to reduce the risk of flooding. Storm surge barriers are a specific type of flood defence. Their function is to reduce the hydraulic loads, the water levels and the wave conditions on the dikes located behind the storm surge barrier. Safety standards for flood defences are established to ensure a minimum level of safety, accounting for the performance of flood defences, which is determined by their probability of failure.
The applicable requirements for storm surge barriers have developed over time. Various assumptions have been made in deriving these requirements, because the applicable standards for flood defences and the corresponding methods to assess their safety have developed. Specifically, assumptions have been made regarding the influence of storm surge barrier performance on the failure probability of dikes. The objective of this study is to build a framework that includes this relationship in a requirement for storm surge barriers.
The framework is built by analysing the relationships that define the flood protection system. It is considered that a reduction in storm surge barrier performance increases the water levels in front of dikes, which increases the dike failure probability and the risk of flooding. The framework built in this study calculates a requirement for structural failure of storm surge barriers based on an economic optimisation at flood protection system level. The dike failure probability is calculated by expressing storm surge barrier performance in terms of water levels in front of the dike and by representing the resistance of a dike to a certain water level using fragility curves. In the next step, investment functions are used to translate failure probabilities into costs to determine the minimum, and therefore optimum, costs at flood protection system level.
The framework is first applied in a generic context to outline the steps and potential applications of the framework. Second, the framework is applied to a schematised representation of the Eastern Scheldt, focusing on the case-specific aspects. The framework is applied to identify the criteria that should be considered in safety standards for storm surge barriers. A requirement for storm surge barriers considers the dike failure probability as a function of storm surge barrier performance. The maximum allowed dike failure probability relates to the maximum allowed consequences of flooding. Furthermore, the variation in dike investment costs compared to the variation in storm surge barrier investment costs is important to derive a requirement that corresponds to an economically optimum flood protection system.


... Read more

In dike safety assessment, failure probabilities are scaled up from the cross-sectional level to the trajectory level. The current Dutch guidelines simplify the upscaling process by relying on rules of thumb. This research introduces a new probabilistic assessment method, named the fragility curve method, which more accurately accounts for the correlation between dike sections and failure mechanisms. The fragility curve method combines fragility curves to transition from the cross-sectional level to the trajectory level. The application of fragility curves allows the water level to be separated from the other variables. Consequently, the correlation of the water level can be regarded independently of the correlation of the remaining variables. In the fragility curve method, the water level is fully positively correlated in space and between failure mechanisms, while the remaining variables are assumed to be independent.
The main objective of this research is to compare the fragility curve method with the current Dutch guidelines for dike safety assessment. To achieve this, both methods are applied to two hypothetical sea dike trajectories. The first trajectory is relatively uniform, comprising dike sections that differ only slightly from one another. The second trajectory contains one dominant dike section. Three failure mechanisms are considered in the assessment, namely: inner slope stability, piping and overtopping. The conclusion of this research is that the fragility curve method is recommended over the current Dutch guidelines to compute the trajectory failure probability of the geotechnical failure mechanisms inner slope stability and piping. The current Dutch guidelines are recommended for computing the trajectory failure probability of the overtopping failure mechanism. Finally, when the failure mechanisms have comparable trajectory failure probabilities, the fragility curve method is recommended for calculating the total trajectory failure probability. ... Read more

Coastal lagoons, encompassing nearly 13% of the world's coastline, represent a vital ecosystem for a considerable variety of flora and fauna. The appealing environment of coastal lagoons has resulted in the establishment of numerous communities around them. The intensification of extreme events due to climate change, the expansion of urban systems, and the release of more pollutants into surface water have altered the natural dynamics of the system. These alterations increase the challenges regarding water safety and quality. Therefore, it is genuinely important to ensure the long-term survival of coastal lagoons. Coastal lagoons are shallow waterbodies parallel to the coast, separated by a small barrier and connected to the sea or ocean by one or multiple inlets. Their behaviour is influenced by the tides, freshwater discharges, wind, geometry, and bathymetry. In a well-functioning lagoon, the water is of sufficient quality, and the surrounding area lives harmoniously with the lagoons, meaning fishing activities are balanced with the lagoon, and the surroundings can cope with floods and droughts.

The Ciénaga de la Virgen in Cartagena, Colombia, is a prime example of a coastal lagoon that faces problems such as pollution, contamination, floods, and droughts, which are common in the area. The consortium ConAgua had proposed multiple measures to enhance the natural dynamics of the Ciénaga, commissioned by the Dutch governmental organisation Rijksdienst voor Ondernemend Nederland.

This report analysed the influence of those measures on the water safety and quality of the Ciénaga.
As part of this, the lagoon and its behaviour were simulated using the numerical hydrodynamic model Delft3D. The measures were implemented in this program, and by altering the boundary conditions, the effects of each measure under different circumstances were evaluated.
The implemented baseline model represents a dry month, normal tides and current bathymetry. Modifications were adapted to evaluate the effect of the limited data and observe the impact of extreme rainfall, sea level rise and wind forcing. Combinations of measures and their behaviour were also simulated.
For the water quality, the flushing time was considered by means of a tracer. Inserting a passive tracer, which either indicated polluted water (1) or clean water (0) into the model, made it possible to analyse the reduction and/or mixing of the pollution. For water safety, the rise in water level at any observation point within the Ciénaga was compared to the baseline model without measures, and the maximum water levels within the month were considered.

The simulations showed a significant impact of tides, wind, and sea level rise on the behaviour of the lagoon. Incorporating wind showed an improved refreshment rate due to the enhanced mixing and altered the plume formation into the Caribbean Sea. However, there are windless days on which the advantage of wind may not be taken into account.
Other simulations, such as the simulation of the combined measures, showed that combinations are not merely the sum of the individual measures and their effect, but the total hydraulic behaviour is altered.
Furthermore, the importance of a clean discharge from the urban and rural side into the Ciénaga was demonstrated. Due to the low refreshment rate, polluted water lingers inside the Ciénaga for a long time, affecting the ecology and the health of the surrounding residents.

In short, the rate of improvement of the water quality by the measures is limited, because the effects remain local. Therefore, achieving water of proper quality is a challenge. The measures did not negatively influence the water levels inside the Ciénaga. For flood risk, it is important to prioritise other effects since it remains a problem in the area.


The report shows that preserving healthy lagoons worldwide is important. To maintain proper water quality, the input of clean freshwater and sufficient mixing due to tidal (ensured by inlets) and/or wind forcing is important. Likewise, the effect of floods and droughts should be limited since many people live near the lagoon. However, water safety cannot be assessed solely by the water levels inside the lagoon. Models can help to assess challenging problems regarding water quality and safety in complex lagoon systems. In future steps, it is recommended that more data be gathered through measurements and observations to assess the quality of the lagoon with more certainty.
... Read more

The sea level is rising, possibly by one meter, by the end of this century. The Netherlands is preparing for this scenario through Kennisprogramma Zeespiegelstijging (KP-ZSS). One of the goals is to determine the hydraulic effects of sea level rise (SLR) on the current system. For the flood risk analysis within
KP-ZSS, the current strength of the flood defences needs to be described. A set of typology-defined fragility curves based on river dikes in river areas describes the current strength of all the primary flood defences in the Netherlands. However, it is unknown if these fragility curves are applicable to sea dikes
due to shorter high water and differences in soil parameters in sea/tidal areas. The research described in this thesis aims to evaluate if site-specific fragility curves for sea dikes result in significantly different predictions of future reinforcement cost for sea dikes compared to the typology-defined fragility curves. The analysis is centred around three dike sections in trajectories 29-3, 30-3 and 32-4 in the Western Scheldt. Initially, an evaluation is conducted on the fragility curves related to the geotechnical failure mechanisms of macro-instability and backward erosion piping. Subsequently, the height requirement is taken into account during the cost calculation. The typology-defined fragility curves underestimate the strength of macro-stability in two out of three
cases with a factor 104 and factor 102, while underestimating it for one section with a factor 105. For the piping failure mechanism the typology-definde fragility curves overestimate the strength in two out of the three cases with a factor 103 and factor 102, but underestimates it for one section with a factor 103.
The pre-overburden pressure appeared to be the most important factor influencing the failure probability of the macro-stability failure mechanism, with higher occurring values for the sections in the Western
Scheldt. The failure mechanism of piping was influenced most by the hydraulic conductivity, where the
encountered soil in the Western Scheldt consisted of finer soils with lower hydraulic conductivity.
From the results, it can be concluded that the use of site-specific fragility curves resulted in a decrease of 13% in net present value, averaging over all SLR scenarios for an analysis until 2200. Considering the most probable SLR scenario resulted in a 12% decrease. If the height requirement is included in the cost calculation, the use of site-specific fragility curves results in a 7% decrease in net present value on average and a 12% decrease for SLR scenario low. For the low SLR scenario, the cost of relocating the road infrastructure in and around the expansion zone of the dike is dominant. With increasing SLR scenarios, the increase in crest height becomes the most important factor, with the revetment the dominating factor cost-wise, leading to minimal differences in reinforcement cost between the fragility
curve approaches. ... Read more

The study of water is without question an important one. We can learn a lot by studying the theory but in the end, it is essential to actually go out into the field and see the hydrological processes in practice for ourselves. The educational value of fieldwork lies not only in seeing theory become reality but also in experiencing the difficulties and limitations of gathering data first-hand.

The water resources department of the Hanoi University of Natural Resources and Environment (HUNRE) wanted to expand its curriculum with a fieldwork excursion that will be part of three courses related to surface water, groundwater, and water quality. During our ten weeks in Vietnam, we assisted the teaching staff of the Water Management faculty in the development of these courses. We selected multiple experiments and found suitable locations for their execution, about a three-hour drive from the university. Several times we visited the fieldwork site together with students and teachers to explore the catchment, perform experiments, and gather data. For every experiment, a comprehensive manual was written with accompanying assignments and sheets tailor-made for the fieldwork excursion. All manuals are combined into a practical document that can be brought into the field.

The experiments require a wide variety of specific pieces of equipment. Most but not all of these were present at the university. With financial support from the Orange Knowledge Project (OKP), we were able to repair existing equipment and acquire new equipment that was lacking in order to facilitate the experiments that were deemed essential. We also re-organized part of the water lab where all equipment is stored to improve the equipment’s maintenance and organization.
With the completion of this project, we believe to have made a contribution to the improvement of the quality of education at HUNRE. We hope that a lot of students can benefit from our efforts as they go on the fieldwork excursion in the coming years. ... Read more

The Hai Phong region is undergoing transformative changes through a Masterplan aimed at enhancing financial stability and improving the quality of life for the local community. A significant component of this Masterplan involves the construction of two new port terminals close to the mangroves of Do Son, a small town southeast of Hai Phong. Mangroves are beneficial in multiple facets. They act as a natural barrier, protecting coastlines from erosion, storm surges, and tsunamis. Additionally, mangroves contribute to water quality by filtering pollutants and trapping sediments, improving overall aquatic ecosystems. Furthermore, they provide crucial habitat for various species, supporting biodiversity and serving as nurseries for many marine organisms that benefit the local community. This research investigates the potential implications of the Masterplan using the following research question: What are the potential effects of the Hai Phong Masterplan on the mangrove ecosystems and the local community? Conducted by a multidisciplinary team of six students, this research involved interviews with professionals, locals, and governmental organisations, extensive literature review, and field trips. It was concluded from this research that the construction of the port terminals have far-reaching consequences. In the mangrove area in Bang La (area A), the port terminal will have a sheltering effect over the mangrove area. This will cause sedimentation to occur and thus accretion. Also, it is also expected that the water quality will degrade further due to increased anthropogenic activity in combination with the poor sewage system present. The mangrove area in Ngoc Hai (area B) is expected to have little direct changes. The local community in Do Son shows varied awareness and support for the Masterplan, with stronger support in mangrove area A. Economic benefits, such as increased tourism, drive positive attitudes. However, there is a notable lack of awareness in area B. The willingness to participate is influenced by economic incentives, and effective communication is crucial for shaping community perspectives. With regards to the further execution of the Masterplan it is recommended to incorporate effective waste management, revise reafforestation plans to meet legal obligations, and engage key environmental stakeholders. For further research, it is recommended to conduct measurements over a more extended period of time to better understand the dynamics of the area. Additionally, more detailed research is needed to substantiate assumptions. ... Read more

In Vietnam, the fishery sector is vital for the economy. The government strives towards an increase in fishing activities in the coming years. The Quy Nhơn port, a key hub in central Vietnam, is set to accommodate more international vessels. This means local fishermen must rely on other ports like Đề Gi, which also needs upgrading to meet aquaculture production goals. To support the fishing sector's growth in Bình Định province, the Khu neo đậu đầm Đề Gi (KND) project is initiated by the local authorities and will contribute to upgrading the Đề Gi port and construct a new storm shelter. However, this project has potential issues: (1) it focuses mainly on storm shelter capacity and does not address the increase of traffic in the current network capacity, (2) the estuary suffers from sedimentation issues, limiting the nautical accessibility of the access channel, resulting in a decrease of port and storm shelter functionality. To tackle these problems the following main question is investigated:

What is the current performance of the Đề Gi port and storm shelter system, and how can engineering methods be used to assess its potential for future growth within the broader context of sustainable socio-economic development?

The main research question is going to be supported by the following sub-questions:

How will the current logistic service network perform in the future vision as foreseen by the responsible authorities and how to verify it with an engineering responsible approach?

How to examine the accessibility of the port and storm shelter in the KND project, while ensuring a safe, robust, durable and effective system?

What are the consequences of the port and storm shelter upgrade on the logistical system and on the conditions in the waterway and what impact does this have on the Đề Gi area?

The main aim of this research is apply engineering methods to understand the system in order to assess its performance and put this in the context of the socio-economic development of the Đề Gi area and the Bình Định province. To achieve this, various research methods are used to analyse the current state of logistic service and nautical accessibility, to identify the bottlenecks in the systems. To include the aspect of incorporating the socio-economics in a broader context of the area, a stakeholder analysis is introduced. For the inland logistic services of the port, a qualitative 4(+1)-transport modelling model is established. For investigating the nautical accessibility, a comprehensive system analysis, including the topics of (1) climate, (2) hydrodynamics, (3) morphodynamics and (4) current and future conditions of the access channel, is conducted to provide insights into nautical accessibility challenges to enhance the safety, robustness, durable and effectiveness of the access channel.

To analyse the logistic service system in the area, field observation in combination with interviews are performed to have a concrete insight into the characteristic harbour patterns, traffic and transportation system and the current transportation network for the goods originating from the harbour. Additionally, various development plans and visions outlined by local authorities are reviewed to gain a comprehensive understanding of the area's future development. By evaluating the current state of the logistic service network alongside the region's development plans, the limitations within the network are identified. The primary bottlenecks in the logistic services system predominantly revolve around capacity and quality issues in the existing road network. Many of these limitations are expected to be addressed through the implementation of the local authorities' development visions. However, for a reliable conclusion, an engineering approach is necessary. To achieve this, a 4(+1)-step transport modelling, coupled with an All-Or-Nothing traffic assignment, is recommended. For the examination of the Đề Gi road network and traffic assignment, this approach provided an initial assessment of the intensity of each link within the study area relative to its corresponding capacity.

The second sub-question is addressed through an analysis and depth assessment, uncovering critical nautical accessibility bottlenecks. These include draught limitations and climate change impacts, potentially compromising safety, robustness, durability, and effectiveness. A depth assessment, considering different vessel types and water levels, provides insights into the current channel status. Safety is a major concern, especially for larger vessels during low water conditions, heightened by climate change. Robustness faces challenges due to sedimentation and storm vulnerabilities. Durability is threatened by changing climate conditions affecting sediment dynamics and storms. Effectiveness remains relatively stable, with 90\% accessibility for the expected future vessel fleet. These findings particularly point to the need for safety and durability measures, especially in light of future climate change predictions, necessitating climate-resilient design.

The third sub-question explores the port and storm shelter upgrade's impact on Đề Gi. Consequences include increased traffic and vessel intensity, on land and through the access channel, and a shift in vessel fleet mix, requiring improved infrastructure and access channel design. This enhances safety and, ultimately, drives socio-economic growth, education, and investment appeal in the Đề Gi area.

In the Đề Gi area, current transportation capacity falls short of future growth needs. Local authorities' development plans aim to resolve logistic service bottlenecks. Nautical accessibility is currently 90\% effective but not consistently safe. Climate change threatens its durability. Engineering models, like the 4(+1) step methodology and comprehensive system analysis in combination with a depth assessment, uncover transport and nautical accessibility challenges. These methods assess future impacts of the port and storm shelter upgrade, benefiting the Đề Gi area with socio-economic development, improved safety and new opportunities for the local community. ... Read more

Large parts of the Netherlands lay below mean sea level. An extensive network of flood protection measures is in place to prevent flooding. Periodic safety assessment and reinforcement are required to guarantee a resilient system. Currently, in the Netherlands, an extensive sea dike reinforcement program is underway to meet the safety standards mandated by the Dutch government. A dike reinforcement project encompasses several components, often interacting with each other. This study focuses on the outer dike revetment. Traditionally, the revetment design is optimised for financial costs. This study aims to optimise the dike revetment design for the lowest Environmental Cost Indicator (ECI). This quantifies the carbon dioxide equivalent emissions generated throughout the entire life cycle of a construction project or its constituent parts. This is pertinent in the current context as the Dutch Government harbors ambitions of achieving a fully circular economy by 2050, with an interim goal of a 50% circular economy by 2030. This ambition is to be implemented by companies within their organization. The revetment is optimised as a whole by assessing the entire outer revetment and applying different types of revetment based on their probability of failure. The primary objective of this study is to acquire knowledge on designing a dike revetment that fulfils technical requirements and has the lowest environmental cost indicator possible. The revetment types to study are loose rock, concrete elements (Basalton), interlocking elements (Verkalit), hydraulic asphalt concrete and grass. The following main research question is defined:

"What sea dike revetment design fulfils safety requirements and has the lowest environmental impact for the Lauwersmeerdijk-Vierhuizergat dike reinforcement project?"

To answer this question, a Python-based model was made. The model evaluates the probability of failure of each design option and calculates the corresponding ECI and financial costs. The LauwersmeerdijkVierhuizergat project, a Waddenzee dike reinforcement, is used as a case study. The required safety level for the Lauwersmeerdijk-Vierhuizergat outer revetment is 1/60.000 years. The model requires input for the design equations. The input consists of decision variables, control variables and hydraulic boundary conditions. The decision variables are the variables in the design equations that the designer can alter. The control
variables are the variables to which the designer has no influence. The hydraulic boundary conditions are determined for each water level discretised in steps of 0.2m. Next to the input for the probabilistic calculation, the input for the ECI and financial costs are required. The ECI data is obtained from the ’Milieudatabase’
(Schipper et al., 2022). The financial cost data is obtained from cost experts from Arcadis.

For loose rock, the probability of failure is calculated with the equations as defined by van der Meer (1988a). For the placed elements, the probability of failure is calculated with the equation defined by Klein Breteler and Mourik (2014). The asphalt revetment is designed with the uplift and wave impact equations as defined in TAW (2002). The grass revetment is designed with the use of the ’Gras erosie buitentalud’ (GEBU) tool. The equations for erosion according to Klein Breteler (2022a) are included in this tool. The design equations are evaluated using crude Monte Carlo analysis for each water level with corresponding hydraulic boundary conditions, decision parameters, and control parameters.

More than 2,000 designs, each meeting safety requirements, are made with varying transition heights. The optimal sea dike revetment design for environmental impact is the design with the lowest ECI score. When the
probabilistic approach is applied, this design has loose rock revetment at the lower section, Basalton for the middle section, and grass for the upper section. In general, it is concluded that loose rock contributes most to the ECI and should be limited as much as possible. The middle section is traditionally made of hydraulic asphalt concrete. However, when replacing this with placed elements, a lower ECI is achieved. The grass revetment often requires large volumes of high-quality clay from external locations, requiring long transport distances. This results in high ECI costs for thick clay layers. When comparing the revetment with the lowest ECI to the revetment design with the lowest financial costs, it is concluded that the design with the lowest financial costs has a large section with hydraulic asphalt concrete instead of placed elements. The study design costs €1890 per meter, with an ECI of €373 per meter. The financially most attractive design costs €1439 per meter, with an ECI of €458 per meter. The difference in financial costs is €451 per meter (24%) and €85 per meter ECI costs (23%). For the revetment design made by Arcadis, deterministic and semi-probabilistic
calculation methods are applied. The asphalt layer thickness is reduced by 50% when applying this method due to the large uncertainty in the probabilistic design. This results in a €12 per meter dike width lower ECI than the design with the lowest ECI made with the probabilistic approach.

Thus, when designing a sea dike revetment probabilistically, aiming to reduce the ECI as much as possible,
apply as little and the smallest possible loose rock grading, and replace the hydraulic asphalt concrete layer for placed elements. ... Read more

In response to Amsterdam’s housing shortage, IJburg on the east side of Amsterdam, is being devel- oped. IJburg consists of six artificial islands in total on which about 20,000 homes for 50,000 residents are being built. Strandeiland (Beach island in English), located in the lake called IJmeer, is one of these artificial islands which is currently being developed to accommodate approximately 20,000 residents. This project aims to introduce approximately 8,000 homes. However, the establishment of Strandei- land presents hydraulic safety concerns, especially with the presence of extreme low water levels and fluctuations due to wind set-up and set-down.
Strandeiland will feature an inland water with high recreational value for residents. This inland water will also provide access for recreational boating. Wind set-down and set-up can create extreme water level differences in this inner water. These water level differences are unfavorable and create danger to the stability of the island. These fluctuations pose a severe challenge to the stability and functionality of the island’s water infrastructure. Two primary solutions were evaluated: the adaptation of the inner quay wall or the implementation of a guard lock. Making the inner quay wall suitable for the water level differences brings several implications:
• Restrictions on utilities: Because the inner quay wall would be marked as primary flood defence, no pipes and cables would be allowed inside the wall.
• Design constraints: When the quay wall serves as the primary flood defence, construction on its inner slope and tree planting is prohibited. This would negatively impact the aesthetics of the waterfront and limit the housing construction space.
• Increased height requirements: The inner wall has to be higher according to primary flood defence regulations, this would escalate construction costs.
• Higher strength sheet piles: A higher strength of sheet piles has to be used to withstand ex- tremely low water levels which would also lead to escalating construction costs.
Adapting the Inner Quay Wall, while feasible, introduces significant design and functional constraints. Because of these constraints, this option is less desirable and implementing a guard lock is the favor- able solution to solve the water level fluctuations.
The guard lock as part of the primary flood defence controls extreme water level variations, ensuring Strandeiland’s water infrastructure’s integrity. The Guard Lock not only modifies the primary flood de- fence location, reducing its length considerably but also mitigates the constraints associated with an adapted inner quay wall. The water level spread is set from the program of requirements at NAP -0.6 meters and NAP +0.1. The current estimate is that this will require the lock to close 10 times a year, which is considered acceptable. A movable bridge is integrated which functions both as a neighbor- hood connector and a part of the beachside boulevard.
The main objective during the design phase is to develop a Guard Lock concept for Strandeiland that facilitates the management of water level fluctuations while accounting for potential failure mechanisms. Dimensions for the Guard Lock were determined based on the standard vessel, leading to lock cham- bers measuring 22 meters in length and 7.6 meters in width. Anticipating approximately ten annual guard lock closures in extreme scenarios, the F/E system is not included initially. To facilitate a possi- ble future inclusion of a F/E system, the core dimensions are based on two lock chambers resulting in an overall structural length of 36.46 meters.
Different gate designs were evaluated for the guard lock design: Mitre Gates, Rolling/Sliding gates, Lift gate (submersible), Lift gate (upward direction), Radial gates and Single-leaf gates. The first step was to check whether the different gate types were suitable for the situation in which Strandeiland is, looking at space and and vertical clearance. The lift gate in upward direction and the rolling sliding gate were considered unsuitable for this purpose. The elevator gate limits vertical clearance and the rolling sliding gates takes to much space besides to the lock. The remaining gate types were measured in a multi-criteria analysis, which resulted in a double set of mitre gates ensuring both-way retention. Because of safety and energy efficiency, but especially because of local knowledge and possibilities for maintenance, electromechanical driving mechanisms were chosen for the gates instead of an hydraulic driving mechanism.
Key design elements of the core construction of the guard lock consist of the concrete structure con- sisting of the walls and the floor slab. After performing the stability checks for the bearing capacity, overturning and piping the strength calculations are done for the floor slab and the walls of the con- crete structure. The reinforcement calculations are providing detailed reinforcements for the floor slab and walls.
The pile foundation is another main component of the structure. The vertical bearing capacity check indicates that no pile foundation is needed, but because non uniform settlement is expected a pile foun- dation will be included. Three different layers were evaluated to check which one was the best fit for the guard lock of Strandeiland. As the first layer is determined to be suitable to bear the load of the structure, this layer has been used. This is the most cost effective for the pile foundation design, as there is less material needed for the pile foundation design. The calculations show that 45 piles with an diameter of 0.8 m each satisfies the need to prevent non-uniform settlements under the structure.
The last component which has been determined is the gate height. The process for determining gate height utilized Reliability-Based Design (RBD) principles. Reliability-Based Design (RBD) ensures the gate height is optimal in terms of cost and safety. In this way an effective design for the gate height is obtained. A comprehensive fault tree analysis, combined with a Monte Carlo analysis, established the final gate height at 5.05 meters corresponding to NAP + 1.55 m, as shown in Figure 1. ... Read more

The Mekong Delta in Vietnam is facing several challenges as a result of climate change. Among others, the effects include an increase in river discharge during the wet season, leading to river floods, and a decrease in river discharge during the dry season. The decrease in discharge results in a shortage of fresh water required for irrigation and drinking water. Besides that, the combination of sea-level rise, land subsidence, and decreased river discharge during the dry season results in saltwater intrusion. This threatens freshwater supply even more. Furthermore, there is an increasing risk of floods from the sea due to low land elevation and the rising sea level in combination with the occurrence of storm surges. The scope of this research is the area around the Ham Luong estuary, which is a branch of the Mekong River. The partial closure of this river branch is considered by the Vietnamese government as a measure to reduce the effect of the above-mentioned effects of climate change. However, not enough research has been conducted yet on the impact of a partial closure on the Ham Luong estuary. This has lead to the following research question: “What is the impact of various closure scenarios on the hydraulic characteristics and social activities in the Ham Luong estuary, considering a 75-year forecast?” The region of the Ham Luong estuary is characterised by its intensive agri- and aquaculture. More than 60% of the inhabitants is directly active within the agri- or aquaculture. As these activities are strongly dependent on the salinity of the estuary, they are highly affected by the effects of climate change. The region is densely populated with more than 125,000 inhabitants living near the Ham Luong estuary. It is clear that the effects of climate change are threatening the region in hydraulic aspects, as well as socio-economic aspects. A partial closure could reduce these effects, but will influence the region in several ways. In order to estimate the impact, a combination of hydraulic and socio-economic aspects is assessed based on a criteria set. This criteria set contains the criteria of freshwater supply, agricultural and aquaculture adaptation, biodiversity, stable riverbanks, and navigability. These criteria will be tested on a total of four alternative interventions in the Ham Luong estuary. Three alternatives with a storm surge barrier and one alternative without a storm surge barrier. All alternatives include heightening of the existing dyke system, as this seems to be inevitable when aiming for long-term development in the region. The extend of dyke heightening is subject to the choice of alternative. As a part of the impact analysis, a Delft3D model was built to analyse the hydrodynamic and morphodynamic processes in the Ham Luong estuary. The model was restricted to the chosen spatial scope, which only covers the Ham Luong estuary, without any upstream bifurcations. The model gave insights in processes like salt intrusion, sedimentation rates, and water levels. However, due to model simplifications and assumptions, the outcomes of the model where not useful for quantitative assessments. Still, the results are used to compare the impact of the different alternatives to each other. As expected, the alternatives that include a storm surge barrier will provide more possibilities to retain fresh water than the alternative without a barrier. From the results, it followed that the limited spatial scope excludes the redistribution of upstream discharge. It is recommended to look at a larger scale of the Mekong Delta when assessing hydro- and morphodynamic processes. Forming a flood protection system, the structural design of such a storm surge barrier, together with a quick estimation of a dyke system. The dyke system is different for each alternative, depending on the presence and the location of a barrier. The barrier design includes a thorough analysis on feasibility of gate types, technical requirements, load combinations, design of dimensions, and the operation. The load combinations take hydrostatic, hydrodynamic, wind, and soil loads into account. The design of the dimensions is done for the gates, sill, lifting structure, pier, foundation, and the bed protection. By assessing the above-mentioned criteria, a preferred solution is identified. This preference is based on a Multi-Criteria Analysis, which includes weighted scores for all alternatives. The outcome of the Multi-Criteria Analysis appears to be very sensitive to the rating and weights of the criteria, which makes it difficult to identify one of the alternatives as the preferred solution based on only the score on the different criteria. For this reason more research is needed. However, when including a cost estimation of the four alternatives, it can be stated that the alternative of no storm surge barrier and only the corresponding extensive dyke heightening could be considered as most cost-beneficial alternative and therefore as the preferred solution. It is expected that with or without closure of the Ham Luong estuary the system will change. The availability of fresh water will be improved by the presence of a closure, although more research is needed to specify this further. The increasing salt intrusion, as a result of Relative Sea-Level Rise (RSLR) will lead to agricultural and aquaculture adaptation in all alternatives. Either due to the construction of the barrier, or due to the gradual RSLR. A closure also has effect on the biodiversity, stability of the river banks, and navigability in the river. When implementing a closure these effects should be further investigated to assess the effect quantitatively. ... Read more

This research aims to improve the current knowledge and insight into the construction process, logistics, and construction costs associated with the offshore pumped storage hydropower plant. The main objective is to enhance the construction costs by optimizing the work method based on these sheltering effects.

The diffraction and sheltering effects due to the caisson dam will be determined using the Goda diffraction tables. Additionally, the Levelised Cost of Storage (LCOS) will be used to assess the cost-effectiveness of this bulk energy storage technology and enables the comparison with alternatives, such as lithium-ion and hydrogen storage.

In summary, this research addresses the promising potentials of work method optimization for offshore caisson projects regarding the local wave climate. For a case study in the North Sea, it has not only highlighted the relevance and importance of including wave sheltering. Moreover, with a LCOS of € 140-260/MWh it also shows the competitiveness of the offshore pumped storage hydropower concept once again. Alternative energy storage methods such as lithium-ion or hydrogen are in the range of € 200-400/MWh for lithium-ion and € 200-1900/MWh for hydrogen storage. Therefore, offshore pumped storage hydropower (PSH) can be a favorable solution enhancing the energy transition. ... Read more

The Mekong Delta is facing some complicated challenges in the near future. Its geographical location and the fact that it is a delta result in low elevation levels which makes it vulnerable to inundation. This problem will only become bigger in the future due to the effects of climate change. To get funding from organisations like the world bank it is important to propose multiple solutions that are beneficial to multiple parts of society. It is favourable to split
a complex system like the Mekong Delta into subsystems to make it more feasible to build realistic models. The subsystem defined in this report is the Hau River estuary. This area mainly suffers from riverine inundation caused by tidal variation in the South Chinese Sea. The biggest city in the region is Can Tho with 1.3 million inhabitants.

The research question is: Which integrated solutions reduce riverine inundation problems in the Hau River estuary while also considering socio-economical aspects? To answer this research question the following four solutions are proposed and designed.

• Discharge sluice in the mouth of the Hau River to reduce the tidal influence

• Wetland with a double levee system and buffer zones to reduce peak discharge

• Bypass channel to the Gulf of Thailand to reduce discharge during the wet season

• Protection of valuable assets and adaptation of local citizens to the new natural balance

Based on desired discharges and water levels preliminary design parameters of the proposed hydraulic structures were determined. The effectiveness of these solutions was assessed based on their ability to reduce the water level in Can Tho. The reduction that the discharge sluice achieved was determined with a zero-dimensional model, whereas the water level reduction that the wetlands and bypass option achieved were determined by Delft3D models. The discharge sluice performed best in reducing the water level in Can Tho, as it opposes the tidal influence in the Hau River.

To assess the quality of the solutions relative to each other a best-worst multi-criteria analysis is done. In this assessment other factors such as financial aspects, socio-economics and transportation are taken into account. The most important criteria are flood reduction and funding opportunities. According to the assessed criteria, the discharge sluice and the wetland are the best-scoring solutions. These solutions have the most potential in reducing the river inundation problems in the Hau River estuary. This does not mean that the bypass and adaptation solutions should be neglected or are not useful. For a complex problem in a complex system like the Hau River estuary, one solution is not going to solve all the problems. A good balance between different aspects has to be determined by also considering other problems like sand mining, subsidence and salt intrusion. ... Read more