Page - 26 - in Book of Full Papers - Symposium Hydro Engineering

This paper is part of a series developed by the State of California, Department of Water Resources to present the results of warning and evacuation related research, conducted for the United States Army Corp of Engineers (USACE), on the Oroville Dam Spillway Incident. This investigation is part of the USACE effort to collect and analyze data on: 1) the timing of the decisions to order public evacuation warnings including the flow of information between engineers and engineering geologists monitoring the hazard and local officials, 2) the method and timing of the dissemination of those warnings including the diffusion or warning by various communication channels, and 3) the interpretation and response by the public to those warnings, including the timing of protective action decisions. The findings from this effort will not only provide invaluable lessons learned that can improve emergency management for this type of rare event, but they will also be incorporated into the existing approaches used by USACE and others to better understand evacuations and how their effectiveness impacts the risk associated with flooding downstream from dams and levees. 2. BACKGROUND ON WARNING AND EVACUATION RESEARCH 2.1. PURPOSE OF RESEARCH EFFORT Decisions within the USACE Dam and Levee Safety Programs follow a risk- informed management process where life safety is paramount. Understanding and making informed decisions related to life safety risk not only requires a clear understanding of the engineering aspects of our flood defense infrastructure, but also the human aspects. To that end, USACE engaged with well-respected social scientists in the areas of warning and evacuation to better understand how flood warnings spread through a community and what causes an individual to delay their decision to take a protective action based on those warnings. This understanding has not only allowed consequence specialists to better assess the existing life safety risk associated with flood defense, but also provide important insights regarding implementing or recommending efficient and effective risk reduction measures. The research, by Dr. Dennis Mileti and Dr. John Sorensen, both renowned socials scientists in the areas of emergency warning and evacuation, covers the warning and protective action initiation timeline, which is composed of three distinct timeframes (illustrated in Fig. 2): warning delay time, warning diffusion time, and protective action initiation time. Their research, which is a culmination of existing social science research on the topic, details the primary factors that influence each 26