On the nature based flood defence dilemma and its Resolution: A game theory based analysis

Nature-based flood defence is an innovative design alternative for achieving protection against flooding. Despite significant advancements in science, models and concepts, routine implementation beyond pilot projects remains limited. To better understand why, we have looked into the complexities of nature-based flood defence implementation and its resolutions, modelling decision-making situations using game theory in three nature-based flood defence cases: The Markermeer Dikes, the Afsluitdijk Dam and the Sand Engine. We observe that nature-based flood defence games are of a multi-level and nested nature. While the decision of whether to employ a nature-based flood defence is seemingly made at the project level, this can only happen when it is coherent with the institutional context that is determined at the policy level. A social dilemma is apparent: while a multi-functional nature-based solution is attractive to a coalition of actors, it is not the most beneficial option for individual actors. Hence, they are faced with the dilemma of opting for their maximum benefit or opting for the greater societal benefit which is less favorable to them. This social dilemma can be tackled by making 'smart moves', as inspired by the Sand Engine case. The nested nature of the problem requires structural change in the institutional context to enable favourable conditions for nature-based flood defence implementations.