87th AMS Annual Meeting

Tuesday, 16 January 2007: 4:00 PM
The Underestimation of Hurricane Damage Potential
206A (Henry B. Gonzalez Convention Center)
Alan E. Stewart, Univ. of Georgia, Athens, GA
Background As society has continued to develop the coastal regions of the southeastern United States, hurricanes will pose ongoing challenges to coping, adjustment, and survival (Changnon, Pielke, Changnon, Sylves, & Pulwarty, 2000; Pielke & Sarewitz, 2005) To ensure physical safety and psychological well-being, it is important for people in areas threatened by hurricanes to both obtain and to understand information that the National Hurricane Center provides about the path and intensity of an approaching hurricane. Among the most widely-cited and disseminated information over the last 25 years is the Saffir-Simpson hurricane scale that provides an indication of the storm's intensity based upon its maximum sustained winds (Simpson & Riehl, 1981). Importantly, the Saffir-Simpson categorization is a linear scale. For each increase in hurricane category (i. e., from 1 to 2, 2 to 3, and so forth), there is an approximately linear increase in the wind speed and the accompanying storm surge (i. e., ocean water driven by high winds that flows into low-lying areas). Although hurricanes are categorized and described according to linear increases in wind speed, the amount of kinetic energy dissipated by a hurricane, which relates to its danger, destructiveness, and lethality is related to the third power of its sustained winds (V3, Emanuel, 2005). Empirical verification of this relationship between the wind speeds associated with each category of hurricane and the ensuing damages was provided by Pielke and Landsea (1998). In examining the normalized costs of hurricanes from 1925 to 1995, both potential and actual costs of hurricane damages increased exponentially as a function of hurricane category. Compared to a category 1 hurricane, a category 3 hurricane resulted in 50 times the amount of damage and a category 4 storm produced 250 times the damage. A category 5 hurricane produced 500 times as much damage as a category 1 storm. The linear nature of the Saffir-Simpson scale may be not fully convey the destructive potential to people who may be affected by hurricanes. Consequently, people may rely upon a linear default strategy in appraising their risks according to the Saffir-Simpson scale. The linear default use of the Saffir-Simpson scale may lead people to believe that the destructive potential, danger, damage costs, and lethality of a hurricane increases in an even, step-wise manner with wind speed. Such a linear default use of the Saffir-Simpson scale would lead to progressively larger underestimations of the dangers posed by major hurricanes. It was hypothesized that although the destructive potential of hurricanes increases exponentially (along with the risk of property loss, injuries, and death) as a function of hurricane category on the Saffir-Simpson scale, people will estimate that the risks associated with each category increase only linearly.

Method Undergraduate students (N = 115) were asked to provide ratings of the damage costs associated with different categories of hurricanes. Data were also collected about the participant's demography, whether they had been evacuated due to a hurricane previously, and to provide ratings about their understanding of the Saffir-Simpson scale. The question format for soliciting participant's estimates of hurricane damages/costs were as follows: “If the monetary cost of the damages produced by a Category 1 hurricane were represented by the number "1," what number would you think best represents the cost of damages produced by a Category 3 hurricane? (Write your number in the blank or type DK for "Don't Know.")” No scales or endpoints were provided so that the participants would be free to use any ratings they wanted for each category of hurricane. Because ratings for hurricane categories 2 through 5 are anchored with a damage rating of 1 for a category 1 hurricane, the respondent's damage cost ratings necessarily represent multiples of damage produced by a category 1 storm, after Pielke and Landsea (1998)

Results Thirty seven (32%) of the participants indicated that they had “much” or “complete” understanding of the Saffir-Simpson scale. There were 19 (17%) of the participants who reported that they had been evacuated because of an approaching hurricane. Participants who had evacuated reported significantly greater understanding of the Saffir-Simpson scale than people who had not previously evacuated, t (113) = 1.94, p = .025 (one-tailed).

The median and mode damage ratings for hurricanes of category 2, 3, 4, and 5 were: 2, 3, 4, and 5, respectively. That is, a preponderance of the participants reported that they believed hurricane damage costs increased linearly with hurricane category. Sixty two percent of the participants produced such a linear profile of ratings. The mean values for hurricanes of category 2 and higher were greater than the median and modal values because some participants indicated that damages increased in a nonlinear manner. In this regard, 23% of the participants indicated that a category 5 hurricane produced at least 10 times as much damage costs as a category 1 storm. Seven percent of the participants produced estimates that exceeded the magnitude of damage increases Pielke and Landsea (1998) reported while the remaining 93% underestimated the magnitude of damages.

Discussion The results of this study are significant in that they reveal an informational or a perceptual lack of awareness of the power and damage potential of major hurricanes (i. e., those of category 3 or higher). Although people who have been evacuated because of an approaching hurricane claim greater understanding of the Saffir-Simpson scale, their responses reflect that they do not fully appreciate that the destructive potential of hurricanes increases exponentially as the category of hurricanes increase.

These results represent a pilot study of people's perceptions of hurricane damage potential. In September 2006, this study will be conducted on a larger scale, using random-digit dialing methods, to assess hurricane damage potential estimates of 300 residents living along the United States gulf coast. The results from this larger, more general study will also be presented at the AMS meeting along with the results of this pilot study. The implications of the findings for increasing the public's awareness of the destruction possible for hurricanes of differing severities will be discussed.

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