Software architecture description has been the subject of intensive research in the last two decades resulting in different formal ADLs applied for describing static and dynamic software architectures of (often large) single systems. However, none of these ADLs has the expressive power for formally describing the evolutionary architecture of a System-of-Systems (SoS). Recently, a novel ADL, called SosADL, was specially conceived for formally describing the software architecture of SoSs. This paper presents a case study demonstrating how SosADL can be applied to formally describe the architecture of a critical Software-intensive SoS, the Urban River Monitoring SoS deployed in the Monjolinho river crossing the city of Sao Carlos.