Simulating stakeholder support for river management

River management is a typical example of a complex problem involving a variety of stakeholder interests and fundamental environmental uncertainties. The Dutch government aims to take the different interests and views explicitly into account by allowing stakeholders to participate in the planning process. The aim of our research is to analyse this participatory process to investigate stakeholder support, their influence on the decision-making process, and the role of norms and co-operation. To this end, we developed an agent based model representing a negotiation among stakeholders. Stakeholder support for a river management strategy is modelled on the basis of the Theory of Reasoned Action and a theory of Social and Cognitive Action. For evaluating the different river engineering alternatives the Agent Based Model is coupled to an Integrated River Model that describes possible long-term impacts (e.g. flood risk, nature development) of river engineering options. We show how the coupled model framework can aid to analyse the participatory planning process of the ongoing Grensmaas project. Also, we assess how the policy outcome might change when the agents would take climate change into account.