Detection and Response Warning Systems

New technological advances in stream and rain gage networks and the increased regional floodplain management efforts have led to the adoption of thousands of local flood-warning systems. Many are simple detection systems and do not provide any mechanism for alerting the population at risk. In the United States until the 1990s warning or detection systems were planned and administered primarily at the local level.

Since then, the federal government including the Bureau of Reclamation, the U.S. Army Corps of Engineers, the National Oceanic and Atmospheric Administration, and the Federal Emergency Management Agency have actively participated in the installation and maintenance of detection and warning systems. Many systems are still managed by regional or local entities, but the percentage of federal dollars has increased substantially. Standards have also been established to help make the systems more compatible across regions (U.S. Department of Commerce, 1997).

An automated integrated network of stream and rain gages is being used in more than 1000 communities in the United States to help provide lead time for floods. Most of the systems are developed through collaborative efforts of many agencies. These ALERT systems (automated local evaluation in real time) have performed many functions other than flood warning, including helping in water supply decision making, fire weather forecasting, pollution monitoring, and providing data for river recreationists (Gruntfest and Huber, 1991). The availability of real-time data on the Internet also has increased interest in these monitoring systems (Gruntfest and Weber, 1998). The State of Arizona is developing a network for flood warning throughout the state. More than 30 agencies and communities are working together on the comprehensive ALERT system (

Warning systems may be nothing more than "cheap payoffs of the raingods." Too often communities install rain gage/stream gage monitoring systems without a plan for getting the warning message disseminated. A warning system is only necessary once poor land-use decisions have been made, allowing people to settle in harm's way. Many of the systems being built are not being adequately maintained to be reliable (Gruntfest and Huber, 1991; Parker and Fordham, 1996). Public education encouraging people to heed environmental cues is also being used. It is particularly difficult to provide adequate lead times for flash floods. Some communities do have drills to test the reliability and completeness of their systems to be sure the systems will operate when the conditions warrant.

As of 2001 a combination of factors increase the likelihood that automated detection systems may become more popular and more valuable. More powerful, less expensive computers, and World Wide Web access provide opportunities for inexpensive real-time weather data. While real-time stream and rain gage networks may be originally installed for flash flood forecasting, many agencies and users find the data useful for alternative purposes.

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