Real-time disaster management and decision support systems rely on complex deadline-driven simulations and require advanced middleware services to ensure that the requested deadlines are met. In this paper we propose a reference architecture of an integrated smart levee monitoring and flood decision support system, focusing on the decision support workflow and urgent computing management. The architecture is implemented in the ISMOP project where controlled flooding experiments are conducted using a full-scale experimental smart levee. While the system operating in the ISMOP project monitors a test levee, it is designed to be scalable to large-scale flood scenarios.