| Abstract: | The hazard of flash flooding, affecting both remote upland stream valleys and urbanizing metropolitan watersheds, poses a need for rapid identification and analysis of sudden changes in stream flow to allow timely public warning. Since 1976, the US National Weather Service (NWS), in cooperation with various regional authorities, has developed a new, low-cost system in response to this need. This system, known as ALERT (Automated Local Evaluation in Real Time) employs stream and rain gauges equipped with self-activating radio transmitters which communicate with a central microcomputer. Using software calibrated to the watershed in question, predictions of downstream flood levels may be rapidly generated. This paper reviews the origins and technology of ALERT systems and reports on the experiences to date of 32 system users. The survey found a high level of satisfaction with ALERT, but uncertainty concerning the reliability of the systems, since few have yet been tested in actual flash floods. |
