The aim of this paper is to investigate how sustainability perceptions are emergent proper- ties of collaborative networks in flood governance in Switzerland. In recent decades, the impact of global warming and multiple stresses on water regimes has influenced the de- sign of new approaches to flood risk management, especially in Western Europe. The use of non-structural measures such as planning tools and watershed campaigns indicates a change from technocratic to more integrated flood governance perspectives. Flood gov- ernance is increasingly influenced by the principle of sustainability, understood as stronger horizontal integration of its social, economic and environmental dimensions. The paper ex- amines the integration of sustainability in the design of flood prevention and policies, sug- gesting that integration relates to participating actors' perceptions of sustainability and that these perceptions are reflected in network structures. Focusing on four regional case stud- ies, we use survey data and social network analysis to investigate how actors relate to each other and how they rank sustainability indicators. Results show that sustainability percep- tions differ strongly across cases, and tend to be more balanced (assigning equal impor- tance to environmental, economic and social indicators) within and sometimes even across actor types and sectors. We find that while actors in central network positions tend to have more balanced sustainability perceptions, context- and project-specific factors im- pact sustainability perceptions even more.