The failure of the Tous dam in 1982 caused one of the most important socio-natural disasters in Spain during the twentieth century. That event triggered a paradigm change in the way disaster risks were perceived and managed, not only locally, but also at multiple levels of governance. Fifteen interviews with relevant stakeholders, content analysis of scientific literature, and review of historical and media accounts indicate that the collapse of the Tous dam had the two major effects. First, it prompted a process of institutional development, which led to the growth, and increase in complexity of the organizations involved both in vertical and horizontal communication of disaster risk reduction. Second, actions taken and experiences gained in dealing with disaster risk reduction in the Tous area were used as a benchmark to develop new strategies, as well as new mechanisms for communication and planning in other territories and other risk domains in Spain. This paper also identified the three main stages in the evolution of disaster risk reduction planning in the area: (1) After the collapse of the Tous dam, disaster risk reduction strategies in Spain focused on improving preparedness in order to reduce short-term risks. (2) Disaster management in the 1990s was strongly influenced by international initiatives, which emphasized the contextualization of risk and the importance in long-term disaster risk reduction measures such as land-use planning. (3) The European Water Framework Directive (2000) and, more recently, the Floods Directive (2007) are exerting a strong influence on the development of a new Spanish flood policy that focuses on preventive measures. However, this process is far from complete and many issues still remain unresolved: dealing with different domains of risk action, integrating concepts of ecological resilience and climate change, and promoting public awareness and effective participation.