The monitoring component of a modern flood-threat recognition system can range from a collec- tion of automated precipitation and stream gauges (e.g., Automated Local Evaluation in Real Time [ALERT] systems) to more advanced systems that utilize weather radars, satellites, and sophisti- cated hydrometeorological numerical models of the atmosphere and watersheds. The objectives of the measurement and detection task are to monitor developing hydrometeorological and watershed conditions and project what might develop in the near term. Reliable data transmissions from the sensors to a central location for display and assessment are essential for these systems, as are trans- missions of the assessments and warnings to response authorities and citizens. Flood-threat recognition systems may include flood forecasting using technology appropriate to the situation as well as the capabilities for assessment and operational support. The value of the fore- cast is derived from the additional lead time made available for the response effort to reduce impacts. There are trade-offs between the accuracy and the timeliness of advanced warnings; typically, rapid assessments are less accurate, but extended analyses can lengthen the time for threat recognition and response. Warning dissemination is an additional key element in order to get messages to public safety authorities in a timely manner and in understandable formats. Advanced warnings can be used to motivate evacuations and guide deployment of assistance. With longer lead times, more aggressive actions may be accomplished, such as drawing down reservoir levels to increase capture capacities, moving vehicles and materials from low-lying areas, or initiating flood-fighting efforts. Mathematically, warning time can be described as (USACE 1996)