How can we make our cities more sustainable? And in particular, how to build the resiliency of urban environments to the effects of climate change and increased urbanization? This is one of the main challenges that urban planners are dealing with today. The relevance of this issue is reflected in the large number of cities around the globe that have recently developed climate adaptation strategies. These plans set out policies to build the capacity of vulnerable areas to withstand and bounce back from external disturbances; build their resiliency. In Delta cities the particular focus lies on improved water management and limiting the negative impacts of increased flooding. The study observes the actions public and private development actors are currently taking in New York City (NYC) in the United States, and the Dutch port city of Rotterdam. What policies have the planning authorities of these two cities adopted to stimulate the building of flood resiliency of in the process of area development? And how do these policies affect behavior of actors in development areas along the waterfront? The motivation behind the international comparison is to examine the effect that factors of the socio-political environment, the institutional landscape, have on the workings of these policies. In both NYC and Rotterdam a case study is conducted on a particular waterfront area. In addition to the literature study and document analysis, multiple semi-structured interviews have been conducted with planning and water management experts, city authorities and local actors. This has resulted in valuable insights in the process of development and incorporation of flood resiliency measures. The findings of this study contribute to the body of knowledge regarding this process of adaptation and, more specifically, building urban resiliency. Outcomes provide understanding in the influence of the institutional landscape on building this flood resiliency in the process of urban area development. Findings point to several aspects of the institutional landscape that affect the effectiveness of public policies. Insight into these aspects can help urban authorities to increase the effectiveness of their policy instruments. The findings furthermore allow for the formulation of recommendations for improving policy effectiveness. The recommendations are aimed at city authorities in both NYC and Rotterdam, as well as other cities that are trying to build their resiliency.