Current Practices for Evacuation Planning

Many states do not have a single master evacuation plan. Some state governments have the power to order evacuations, but often do not do so. Evacuation decisions are usually controlled by or delegated to local levels of government, with the state level assisting once the decision has been made (Urbina and Wolshon 2003). Because of this, the decision making

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process for hurricane evacuation is unique to individual jurisdictions. This is done because local jurisdictions typically have more knowledge of their capabilities and needs.

A growing body of work has been devoted to evacuation planning in terms of how best to evacuate populations once the decision to evacuate has been made. One such recent advancement has been the development of contraflow evacuation methods (Wolshon 2001). Studies have also been performed on the expected response to evacuation orders as mentioned in Section 2.1.1 (Perception of Risk). Additionally, the economic impacts of hurricane evacuations have been investigated by determining the costs associated with evacuation, such as transportation and lodging, and the likelihood of a population evacuating (Whitehead 2003).

The most common overall method of evacuation implementation is the phased

evacuation. In the phased evacuation, the most vulnerable areas are evacuated first, with slightly less vulnerable areas evacuated afterwards. Figure 2.19 shows emergency evacuation zones for the state of Louisiana.

Figure 2.19 Hurricane Evacuation Zones for Louisiana. (GOHSEP 2008b)

The red area indicates Phase I of the evacuation and is intended to be issued 50 hours before the onset of tropical storm winds. Orange (Phase II) is issued 40 hours before the onset of tropical

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winds. Yellow (Phase III) is issued 30 hours before the onset of tropical storm winds. These three evacuation phases are intended for traffic management purposes, and do not in themselves mandate an evacuation. However, they do indicate the time before the onset of tropical storm conditions that is needed for a successful evacuation.

A now common practice during hurricane evacuations is the use of contraflow.

Contraflow is the reversal of traffic lanes opposite of their normal travel direction. By utilizing contraflow, more traffic can be routed through existing traffic networks in the desired evacuation directions. States currently using some form of contraflow in evacuations include Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Caroline, Texas, and Virginia.

2.11.1 Current Evacuation and Sheltering Decision Making Processes

There is a limited amount of information available in the literature on what decision processes are followed to determine evacuation and sheltering for hurricanes, and much of the available literature deals with how to effectively communicate information about hurricanes to different portions of the population. There is, however, some information available on

organizational decision making which pertains to decision making for hurricane evacuation and sheltering.

A primary function of emergency management officials is to continuously monitor the hurricane as it moves toward landfall. Information on a particular storm is gathered from the National Hurricane Center, as well as storm tracking programs such as HURREVAC (Lindell 2007). HURREVAC plots a storm‟s past and current positions, as well as the forecast track. The program estimates the onset of tropical storm force winds for an area, and combines these estimates with user input evacuation times. It then estimates timelines for which evacuations must be made based on onset of tropical storm winds (FEMA 2009). HURREVAC also has the ability to plot SLOSH storm surge elevations for single SLOSH model runs. Based on

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continuous information from the National Hurricane Center, as well as input from secondary computer programs such as HURREVAC, decisions are made on whether to evacuate or shelter. There is limited quantification of uncertainty input into the decision process. Tools such as the NHC forecast track “cone of uncertainty”, as well as wind probability tables, are available for use. These tools may not provide site-specific information for consideration in the decision making process.

Difficulties often arise when the decision must be made on whether to evacuate or shelter. This is because at the timelines required for evacuation, a storm is still far from landfall. Emergency officials must consider the costs, both economic and life-safety, which will be incurred by deciding to either evacuate or shelter. Examples of economic costs include: government expenses associated with evacuation management; lost business and tax revenue; and lost wages and gas, food, and lodging, costs for evacuees. Figure 2.20 shows a simple decision tree for the evacuation/sheltering decision.

Figure 2.20 Evacuation Decision Tree (Lindell 2007)

When making a decision, officials consider the impacts of their decision

regardless of whether the hurricane actually impacts their area of responsibility. If an evacuation is ordered, and the storm does not strike (Outcome B from Figure X), no lives will be lost from the storm, but high cost will have been incurred. Also, the official‟s credibility may have been compromised, and a future evacuation may not be heeded. If no evacuation is ordered (sheltering

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in place), and the hurricane strikes (Outcome C from Figure X), no economic cost from evacuation will be incurred, but lives could be lost and the officials credibility may be compromised.

Decision processes followed by administrators of critical care facilities are similar to emergency officials, but differ in several key areas. After Hurricanes Katrina and Rita, nursing home administrators were interviewed to determine why they did or did not evacuate for the storms (Dosa 2007). Twenty administrators participated in the study, and eighteen out of the twenty made the ultimate decision on whether to evacuate or shelter. For critical facility

administrators, the cost of evacuation is much higher, both in terms of life safety and economic cost. These costs factor heavily into their decisions. For Hurricanes Katrina and Rita, the administrators were more likely to decide to shelter in place than the general public. This was primarily due to the difficulty in moving facility residents, obtaining staff, and finding a suitable location outside the area anticipated to be heavily impacted by the hurricane to house their residents if they did evacuate.

Preliminary guidelines are available to aid nursing home administrators in evacuation and sheltering decision making (FHCA 2008). These guidelines are very general in nature and

discuss external and internal factors which must be considered when making decisions. External factors include the nature of the storm, the geographic location of the facility with respect to flooding, and the location of the facility with regard to population centers. Internal factors include available staff and supplies, resident characteristics, physical characteristics of the facility, and available evacuation transportation and destination. This guideline considers storm effects for an approaching hurricane, but does not consider uncertainty in storm forecast, or the probabilistic risk associated with the storm.

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