Cascading Threat Model Applications in Conducting Hazard and Risk Assessment for Wildfire and Post-Burn Flash Flood
Fred May
Cascading hazard models depict either potential threat (threat model) sequences or document historic ones (consequence model). Wildfires and associated flashfloods produce a numerous array of potential threat sequences, too numerous to recall. Threat models developed using computer software designed to capture cascading and branching threat sequences enable mitigation workers to anticipate complex sequences, identify critical threats or consequences, and develop mitigation and response strategies and to determine systematic education or training needs.
Credible cascading threat models are developed by multi-agency teams of specialists. They are updated as events provide additional insights. Threat models are powerful analytical tools useful in regional planning and for detailed and systematic local hazard and risk assessments. These models have been used successfully for hazard and risk assessment with Federal, State and local planning teams coming together to analyze threat or consequence sequences for specific geographic areas. The systematic approach leaves “no stone unturned” in analyzing threat and risk and in determining mitigation or response strategies. The approach is efficient, allowing for a complete analysis in a couple of hours; updates for analysis conducted on an annual cycle require less time and are more complete than fragmental approaches based on limiting lists or tables of considerations. As analyses are conducted, the software allows for easy updating to include additional threats or consequences encountered during actual analysis sessions.
Cascading models are understood with a unique nomenclature beyond the typical primary and secondary hazards, and with threat and consequence/impact nomenclature, threat tree geography, linkage, and pathway and branch analysis. An effective analog is cascading (toppling) dominoes, arranged in branching sequences, depicting how a wildfire can threaten community or government resources. These are based on the combined experience of planning teams. Envisioning a single domino (part of a cascading sequence), one sees two numbers. For the purpose of cascading hazard and risk analysis, the top number refers to the degree of damage for a particular asset, while the bottom number refers to the degree of consequence if that asset is lost, or damaged. As dominoes tip over, they tip over in a sequence analogous to the cascading of threats in a wildfire, or post-burn flashflood. The first to topple is called the primary threat (anticipated) or consequence (historic), the second is the secondary threat, the third are tertiary threats, the fourth are quaternary threats, etc., in branching sequences. The computer depicts the branching sequences as a branching tree structure – a cascading threat or consequence model – also known as a hazard tree. In reality, what is observed are cascading degrees of damage and associated cascading degrees of consequence. The analysis process ultimately exposes the anticipated cascading wildfire and post-burn flash flood damages (losses) and consequences. It then serves as a realistic justification tool for mitigation. It also identifies highly-dangerous threats that may otherwise go undetected but can now be factored into decision making for development of mitigation strategies. Rather than developing mitigation plans for single point threats, as is often done, the strategies are developed for sequences of events, where some mitigation can be performed at each node between threats (dominoes).
This paper explains both generic (anticipated) and historic (consequence) cascading threat models for wildfire and post-burn flashflood. On August 18 through
Fire Session - Thursday Afternoon
corresponding author:
Institute for Emergency Preparedness
Jacksonville State University
700 Pelham Road
Jacksonville, AL 36265
Encyclopedia ID: p75
