‘The Dutch are not going to lose against the sea’, is a commonly accepted quote of the citizens of The Netherlands. Having developed a country below sea level, Dutch people are aware of the challenges of the sea, but are committed in an endless fight against it. Nowadays, with global warming increasing, the challenge for them is even bigger. Sea level rises threateningly, and the estimations about the future conditions are characterized by deep uncertainty. For that reason, the Dutch government identified 13 weak links in the coastal defence system, one of which is the area of interest for this research, the Scheveningen district and its surroundings, belonging to the Municipality of The Hague. Apart from its vulnerable coastal defence position, the area is densely populated and the most popular beach destination of the country. The aim of this research is to provide water safety solutions in the long term (until 2100), while taking into account the stakeholders demands. Secondly, compare the designs and identify specific aspects in which decision makers in the Municipality of The Hague would be forced to make compromises in order to implement a final solution for the project. Thirdly, investigate on additional measures that can complement and optimize the water safety design. For that reason, a background research was conducted through literature reviewing, interviewing experts and stakeholders, in order to collect information about possible sea level rise scenarios, existing boundaries of the system and stakeholders perspectives. The water safety issue was tackled with nature-based solutions following the principles of Integrated Coastal Zone Management by Building with Nature a framework that delivers solutions for sustainable infrastructure. Two solutions packages were obtained. The first one uses a Preserve strategy, attempting to maintain the current coastline position with soft (sandy) interventions where possible, keeping construction costs relatively low. The second package uses an Advance strategy, extending land in the seaward direction, and creating a large space for the development of natural habitats and human activities. To evaluate and compare the resulting designs, a Multi Criteria Analysis was conducted according to five criteria: Recreation and tourism, Social values, Ecology, Economy and Finance, Sustainability, Design. The goal of this part of the analysis is not the selection of a winner option but the assistance to the decision making process by providing strengths and weaknesses of each option, as well as a comparison between the two in terms of the above mentioned criteria. From this point on, this research identified a total of eight aspects where the decision maker, the Municipality of The Hague, would be forced to make some sort of compromises between different interests, in order to implement the project. The evaluation process resulted in a slight preference for the Advance strategy as the most integrated solution package. The optimization of this design was realised and four additional measures were proposed, leading to a more holistic proposal with more chances to bring acceptance among all stakeholders involved.

Nature-based initiatives have emerged as potential solutions to problems caused by saltwater intrusion in deltas found globally, but their successful implementation is enabled partly by a multi-stakeholder approach. The latter involves managing several parallel stakeholder objectives, which usually requires quantitative knowledge to understand possible collisions of interests. On that account, the present work developed a systematic approach (referred to as the `comparison tool') to quantitatively compare the objectives of multiple stakeholders interplaying in a delta. As a first approach, the comparison tool is intended to support decision-making to deal with potential conflicts between freshwater supply and port logistics interests. In particular, the present juncture in the Rhine-Meuse Delta in the Netherlands was used to investigate potential trade-offs generated by the nature-based shallowing (or river bed heightening) of the Rotterdam Waterways. The comparison tool is founded on the objective-based assessment of Building with Nature (BwN) solutions. The effects of a BwN solution are assessed separately for each functional requirement and then are related in a combined assessment. The impact assessment for the shallowing of the Rotterdam Waterways required two numerical modelling studies. First, effects on the hydrodynamics and salt transport in a partially-mixed estuary were modelled with the Operationeel Stromingsmodel Rotterdam (OSR), developed by the Port of Rotterdam Authority. Secondly, changes in meso-scale traffic flows over the port network were modelled with the OpenTNSim developed by TU Delft. Afterwards, the effects on freshwater supply and port performance (capacity and efficiency) were quantified separately and then compared. This research delivered a systematic procedure and demonstrated how a combined assessment could be performed in the context of nature-based solutions to mitigate salt intrusion. The most important outcome entails quantitative trade-offs between port efficiency and freshwater supply over a range of bed level increase from 0.0 m to 3.9 m. In general, results showed that the improvement towards the objective of port logistics always goes to the detriment of the freshwater supply objective while increasing bed level. Also, this study found that a collision of interests between the two types of end-users might worsen for a bed level increase over 2 m. Additional results showed that shallowing could be associated with benefits for freshwater supply through a decrease in the duration of water shortages due to a retreat in salt intrusion. The latter holds for specific environmental conditions of low river discharge and mild wind. Also, this study concluded that shallowing could negatively affect port efficiency due to heavier vessel traffic and more burdensome tidal window restrictions, which can result in an exponential growth of vessels average waiting times if the bed level increases over 2 m. Since the freshwater and port sub-systems were simplified, uncertainty in the results was unavoidably accepted. Despite these simplifications, this research demonstrated the main principles in implementing the comparison tool and lays the groundwork for more comprehensive models. In addition, several recommendations for policy-making are proposed, setting a basis for later discussions between freshwater supply and port-related stakeholders in the Rhine-Meuse Delta.