Computer graphics and scientific visualization are fields of computational science that have evolved rapidly over the past decades. Scientific visualization has become an important technology in serious gaming and science-based decision support. Water management is a complex process dealing with a wide range of, often conflicting, considerations. Especially in flood risk assessment and disaster management, stakeholder involvement is an important component in the decision making process. Both 2D map-based approaches as well as 3D virtual environments are explored for applications in water management. Case studies focus on the role of 3D information in river delta development, flood disaster management and coastal protection. Implications for next-generation decision support systems are outlined.