THE DEVELOPMENT OF A MULTI-LEVEL FLOOD/DEBRIS FLOW WARNING SYSTEM IN A HIGH ENERGY ENVIRONMENT

The development of a highly integrated, multi-level, flood/debris flow warning system operating in near real time in a higher energy, rapid response, mountainous environment is discussed. The watershed used in this study is located in the coastal region of Orange County, CA. Over a period of 70 years, it has undergone 13 major flood/debris flow events resulting in tens of millions of dollars in damage and in several instances the loss of life. Moreover, an evaluation of the dynamics of the watershed indicated the effective response time between flow event initiation and impact on critical locations was approximately 15 minutes or less making it an ideal site for the study and the implementation of such a system.

The warning system developed to operate in these time frames and in relatively harsh conditions consists of: 1) an integrated regional radar/ local radar, combined with a regional/local near real time rain gauge reporting system; 2) a network of in-situ slope water level monitoring sensors reporting hillside saturation levels in near real time; 3) a network of channel camera and water levels monitoring systems tracking channel flow levels in near real time; 4) an integrated central computer monitoring system bringing all of the information together at a emergency operations center; 5) an integrated multi-level threshold based alarm system; and 6) a communications system that enables reliable and redundant remote access to the entire network not only at a central decision making center but also from field or other key locations in the area. This last requirement was deemed critical in terms of providing the capacity for field based command decisions with respect to evacuations, resource deployment, and other emergency response decisions by individuals, groups and agencies tasked with dealing with the threats posed by the flood and debris flow events that occur in such an area. The system is presently in operation.