Decision-making for flood defense while facing a considerable change in driving forces demands other methods than the traditional approach of forecasting and optimal policy selection. Exploratory modeling can be a candidate for helping adaptive policymaking to deal with the uncertainties that confront decision-makers. In adaptive policymaking, policies are considered as response to changes over time. This research addresses the question whether exploratory modeling is appropriate to support the design of flood defense strategies and in particular to assess the value of flexibility in such designs.