European seas are encountering an upsurge in competing marine activities and infrastructures. Traditional exploitation such as fisheries, tourism, transportation, and oil production are accompanied by new sustainable economic activities such as offshore windfarms, aquaculture, and tidal and wave energy. One proposed solution to overcome possible competing claims at sea lies in combining these economic activities as part of Multi-Use Platforms at Sea (MUPS). MUPS can be understood as areas at sea, designated for a combination of activities, either completely integrated in a platform or in shared marine space. MUPS can potentially benefit from each other in terms of infrastructure, maintenance, etc. Developing MUPS in the marine environment demands adequate governance. In this article, we investigate four European sites to find out how governance arrangements may facilitate or complicate MUPs. In particular, we apply a framework specifying

Water resources management issues tend to affect a variety of uses and users. Therefore, they often exhibit complex and unstructured problems. The complex, unstructured nature of these problems originates from uncertain knowledge and from the existence of divergent perceptions among various actors. Consequently, dealing with these problems is not just a knowledge problem; it is a problem of ambiguity too. This paper focuses on a complex, unstructured water resources management issue, the sustainable development-for ecology, economy and society-of the Delta-region of the Netherlands. In several areas in this region the ecological quality decreased due to hydraulic constructions for storm water safety, the Delta Works. To improve the ecological quality, the Dutch government regards the reestablishment of estuarine dynamics in the area as the most important solution. However, re-establishment of estuarine dynamics will affect other uses and other users. Among the affected users are farmers in the surrounding areas, who use freshwater from a lake for agricultural purposes. This problem has been addressed in a participatory decision-making process, which is used as a case study in this paper. We investigate how the dynamics in actors' perceptions and the knowledge base contribute to the development of agreed upon and valid knowledge about the problemsolution combination, using our conceptual framework for problem structuring. We found that different knowledge sources-expert and practical knowledge-should be integrated to create a context-specific knowledge base, which is scientifically valid and socially robust. Furthermore, we conclude that for the convergence of actors' perceptions, it is essential that actors learn about the content of the process (cognitive learning) and about the network in which they are involved (strategic learning). Our findings form a plea for practitioners in water resources management to adopt a problem structuring approach in order to deal explicitly with uncertainty and ambiguity.

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Green roofs can contribute to climate adaptation and a sustainable urban environment. Whether municipalities for these or other reasons should encourage green roofs, depends on the goals that are aimed at. For the municipality of Tilburg opportunities were investigated for usage of green roofs as measure for climate adaptation and for scaling up green roof in Tilburg and other municipalities. In three projects in Tilburg the opportunities for the application of green roofs and the attitude of actors involved were investigated. Also, the experiences of six other municipalities, which are promoting green roofs, were examined. The type of project, purpose, and insight in costs and benefits affect the attitude of actors and hence the opportunities for application and scaling. In the examined municipalities green roofs in general are stimulated with subsidy, communication and pilot projects.The experience with green roofs in other municipalities are predominantly positive.

It is widely recognized that integrated approaches are required to manage our limited water resources in an effective and sustainable manner. In the Netherlands, this is mostly realized by organizing integrated spatial development processes. This paper presents a discussion in which the distribution of freshwater is integrated with spatial development in the southwestern Delta in the Netherlands. This discussion is characterized by uncertainty in knowledge and stakeholders with diverging perceptions. By actively involving these stakeholders in a process of problem structuring, it was possible to reach an agreement on the preferred direction for solutions. Problem-structuring involves that stakeholders actively participate in formulating the problem and its solutions. It is characterized by interaction between stakeholders and the integration of expert knowledge and stakeholder knowledge. Based on these practical experiences, we conclude that putting integrated water management into practice benefits from a problem-structuring approach. This enhances learning processes and contributes to the development of an agreed upon and valid knowledge base. As the context of such processes is highly dynamic, there is a need for transparent and adaptive process management.

In this paper, we focus on a complex management issue, namely the physical effects of a large-scale offshore sand extraction. For these kinds of issues there is no obvious morphological model available to answer all management questions. Therefore, we aim to answer as many management questions as possible, using a set of existing morphological models parallel to each other. In this way, we can support governments to assess applications for licenses for large-scale sand extraction. We investigate whether this parallel modeling approach is significantly more helpful in addressing the management questions than a single modeling approach. The management questions are translated into quantifiable variables, known as Coastal State Indicators (CSIs). We focus on three coastal user functions: coastal safety and maintenance, offshore infrastructure, and navigation. The selected morphological models are assessed on (1) their applicability to the CSIs and (2) the reliability of their predictions. We quantify the predictive power of the models based on these two parameters. We conclude that by using a parallel modeling approach it is possible to address more management questions effectively in comparison with using just the best single model. The use of this parallel modeling approach increases the predictive power significantly, here 35%. ADDITIONAL INDEX WORDS:

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