WHEN EVACUATION IS THE ANSWER
A challenge during hurricanes and other hazards is the evacuation of massive numbers of people. Pamela Murray-Tuite, associate professor of civil engineering, is the co-author of Large-scale evacuation: The analysis, modeling, and management of emergency relocation from hazardous areas (Taylor and Francis, 2019; Lindell, M. K., Murray-Tuite, P., Wolshon, B., & Baker, E. J.). She shared with us some important lessons learned about mass evacuations through research and modeling.
When we talk about evacuation, what hazards are you considering?
A: Evacuation can apply to any hazard for which it is a safer course of action to move from a threatened area than to remain. Hazards that typically come to mind are fires, floods, hurricanes, tsunamis, nuclear power plant incidents and some hazardous materials releases. Each hazard has different characteristics and challenges, such as the amount of advanced warning, size of the affected area and the distance to safety.
What are some practical things we should remember when authorities in our area are calling for evacuation?
A: First, recognize that authorities do not make evacuation recommendations lightly. Evacuations can be expensive, and if the hazard does not hit, local areas may face challenges with reimbursement. The authorities do not want to unnecessarily worry or inconvenience their citizens. There are two ways for authorities to be considered “wrong” — issuing evacuation notices and the hazard does not hit the area and failing to issue evacuation notices for a hazard that does strike. The first error type still preserves the safety of the public, while the latter has life-safety consequences. No one knows exactly what is going to happen. When an evacuation notice is provided, it is important to pay attention.
Second, for a large-scale hazard (e.g., hurricane), remember that many people are in the same situation. They may have similar preferences, such as daylight departure and arrival or not evacuating until some of the uncertainty is resolved. Much of the congestion associated with evacuations is due to demand exceeding capacity. Evacuating earlier — be it days in advance or earlier on a given day (say around 4 a.m.) — can help alleviate some congestion. Congestion also increases fuel/energy consumption; when magnified by a large number of travelers, fuel shortages are a possibility.
Finally, recognize that your decisions affect others. Neighbors may observe you evacuating and use this as a cue to behavior they may want to consider. The aggregate decisions of the population largely affect how successful (or not) the evacuation is considered.
What are some of the lessons have we learned since Hurricane Katrina and other similar events?
A: Each event is unique and brings opportunities to learn about and make improvements to disaster management. Sometimes, evacuation is not the best course of action, depending on the hazard, location and time to impact. Although there are many lessons learned from high-profile evacuations, only four are discussed here:
Hazards can be compounded. During Hurricane Katrina, the hurricane led to an evacuation, but a second evacuation was needed when the levees failed and flooded much of New Orleans. In 2011, an earthquake off the coast of Japan triggered a tsunami that exceeded the sea wall protection built for the Fukushima Daiichi Nuclear Power Plant. The water led to several issues with generators used for cooling, eventually leading to meltdowns and radiation releases. Multiple sets of evacuations were needed for the power plant issues as well as the tsunami. Finally, although it is well recognized that hurricanes bring strong wind and storm surge and are accompanied by rain, the potential magnitude of that rain was highlighted in Hurricane Harvey. This storm, which delivered over 40 inches of rain, led to thousands of rescues.
Not every household has a reliable vehicle for evacuation. The evacuation for Hurricane Katrina worked fairly well for those who were able to self-evacuate in their own vehicles. However, Hurricane Katrina highlighted that carless households could be geographically clustered, making it challenging to obtain rides. Overall, better planning was needed for those who could not evacuate themselves.
Actions taken to address transportation issues for a normal day can affect evacuation performance. The wildfire known as the Camp Fire in 2018 highlighted this issue. One of the main evacuation routes had been intentionally narrowed to improve safety and reduce the number of vehicles able to use the road. (St. John et al., 2018). Addressing evacuation needs during development and when modifying the transportation system could lead to improved evacuation outcomes.
Clear communication is crucial. Communication surrounding an evacuation should clearly state who is issuing warnings, what the hazard is, at-risk locations and populations, when the hazard should arrive, how probable it is, the specific recommended protective actions, and where to find additional information and sources of assistance. (Lindell et al., 2019). Clear messaging can help encourage those who should evacuate to recognize that this is the recommended protective action for them. Clear messaging can also help reduce shadow evacuation (people from low-risk areas evacuating), which can delay travel for those at higher risk. The information should also be communicated in multiple languages, reflecting the resident and tourist populations, and disseminated through multiple channels since communication technology preferences differ.
Drabek, T. E. (1999). Understanding disaster warning responses. The Social Science Journal, 36(3), 515-523.
Lindell, M. K., Murray-Tuite, P., Wolshon, B., & Baker, E. J. (2019). Large-scale evacuation: The analysis, modeling, and management of emergency relocation from hazardous areas. Taylor and Francis.
Lindell, M. K., & Prater, C. S. (2007). Critical behavioral assumptions in evacuation time estimate analysis for private vehicles: Examples from hurricane research and planning. Journal of Urban Planning and Development, 133(1), 18-29.
St. John, P., Serna, J., & Lin, R.-G. (2018). Must Reads: Here’s how Paradise ignored warnings and became a deathtrap. Los Angeles Times. https://www.latimes.com/local/california/la-me-camp-fire-deathtrap-20181230-story.html.
Trainor, J. E., Murray-Tuite, P., Edara, P., Fallah-Fini, S., & Triantis, K. (2013). Interdisciplinary approach to evacuation modeling. Natural Hazards Review, 14(3), 151-162.