A combined sewer/enclosure overflow (CSO) sensor system is described for accurate detection and measurement of overflow events. From the combined data, trending information can determine if there is debris accumulation. Rain masks can be used in the trending data to measure overall health. External sensors in combination with the CSO sensors provide predictive information and additional levels of information/data accuracy. The sensor system automatically and remotely monitors CSO locations and provides real-time data regarding start times, stop times, duration, and flow volumes of overflows that occur in these structures and provide regulatory and public notification of these events.