Tornado Disaster -- Kansas, 1991

On April 26, 1991, 54 tornadoes swept across six midwestern states, causing 24 deaths and more than 200 injuries, requiring disaster-relief services for more than 8000 persons, and causing property damage of more than $250 million. In Kansas, one tornado, with wind speeds exceeding 260 mph, caused 17 deaths. The 46-mile path of the tornado led through Andover, Kansas (Butler County) (population: 4300), where the town's only outdoor warning siren failed. A mobile-home park (MHP) in Andover with 244 homes and one community storm shelter was struck by the tornado, resulting in the destruction of 205 (84%) of these homes. This report summarizes a poststorm survey, conducted by local health departments, the Kansas Department of Health and Environment, the American Red Cross, and CDC, to identify risk factors for injury and death among persons in the MHP.

Telephone interviews were conducted with one adult from each MHP household that was destroyed. Data were obtained from relatives or neighbors for households in which no one survived. Information collected included length of warning, evacuation and shelter behavior, types of injury, and causes of death. Data were available for 333 of 336 persons who were at home during the tornado. The mean age of the study population was 29.7 years; 50% were female, and 99% were white.

In the 45 minutes before the tornado reached the MHP, 146 persons (44%) fled the MHP. Among the 187 (56%) persons remaining, 149 (80%) were in the community shelter and 38 (20%) were not when the tornado struck.

No deaths or serious injuries (i.e., injuries requiring hospitalization) occurred among persons who fled the MHP or among persons who reached the community storm shelter. Among the 38 unsheltered persons, 11 (29%) were killed, 17 (45%) were hospitalized, and nine (24%) sustained minor injuries.

Remaining unsheltered in the MHP was the prominent risk factor for injury or death and was associated with both delayed warning and advanced age. Persons receiving less than 5 minutes of warning time were more likely to remain unsheltered than were those with greater than or equal to 5 minutes of warning (relative risk (RR)=10.3; 95% confidence interval (CI)=4.6-22.9). Persons aged greater than or equal to 60 years were more likely to remain unsheltered than were those aged less than 60 years (RR=3.5; 95% CI=1.9-6.4).

Although Andover's only outdoor warning siren failed, 72% of the persons in the MHP study population received warning cues transmitted by the media from the National Weather Service. The MHP study population was aware of a tornado threat to their county for an average of 18 minutes. Because the tornado struck the MHP during daylight, many residents were able to see the funnel for as long as 14 minutes before impact.

In Butler County, 12% of the population resides in mobile homes, a rate twice the national average of 6% (Bureau of the Census, unpublished data, 1990). A survey of MHPs (defined as a centrally managed grouping of five or more mobile homes) in Butler County, conducted in conjunction with the poststorm survey, determined that, of 25 MHPs, 40% reported not having a community storm shelter. No legal requirements existed in Butler County at the time of the disaster for MHPs to provide community storm shelters for their residents.

Reported by: M Wemmer, MSW, Z Meyers, American Red Cross; C Borger, Butler-Greenwood Bi-County Health Dept; F Tosh, MD, City-County Health Dept, Sedgwick County; C Konigsberg, Jr, MD, D Taylor, C Wood, MD, State Epidemiologist, Kansas Dept of Health and Environment. Health Studies Br, Div of Environmental Hazards and Health Effects, Div of Injury Control, National Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: In the United States, an average of 700 tornadoes are reported each year (1). Kansas is among five states with the highest incidence of tornadoes per 10,000 square miles (2). Since 1961, approximately 2500 persons have died, and 50,000 persons have been injured as a result of tornadoes in the United States (National Severe Storm Forecast Center, unpublished data, 1990). Persons at highest risk for injury during a tornado are the elderly, residents of mobile homes, and persons attempting to flee by automobile (3-5).

Adequate warning and proper sheltering are critical factors in preventing tornado injuries and deaths. Tornado-related deaths have been declining since 1950, largely because of improvements in warning systems (2). However, more than 12.7 million persons in the United States live in mobile homes, and more than 200,000 units are constructed each year (6). As the number of residents of mobile homes increases, mobile-home-related injuries from tornadoes are expected to rise unless the availability and use of storm shelters increase at a similar rate.

The investigation in Andover, Kansas, demonstrates that the use of a community storm shelter by a MHP population can prevent injuries and deaths during a tornado. Recommendations for tornado safety in MHPs include 1) providing community shelters that are accessible and of sufficient size and number to accommodate all residents; 2) making special provisions for the elderly who may have disabilities that impair their ability to access shelter and/or comprehend storm warnings; and 3) ensuring that tornado warning systems do not rely on a single mechanism to assure prompt and specific notification of potential danger (7).

References

1. Sanderson LM. Tornadoes. In: Gregg MB, ed. The public health consequences of disasters 1989. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, 1989:39-49.

2. National Climatic Data Center. National summary of tornadoes 1989. Asheville, North Carolina: National Climatic Data Center, 1989:10-13. (Storm data; vol 31, no. 12).

3. Glass RI, Craven RB, Bregman DJ, et al. Injuries from the Wichita Falls tornado: implications for prevention. Science 1980;207:734-8.

4. Eidson M, Lybarger JA, Parsons JE, et al. Risk factors for tornado injuries. Int J Epidemiol 1990;19:1051-6.

5. CDC. Tornado disaster -- North Carolina, South Carolina, March 28, 1984. MMWR 1985;34:205-6,211-3.

6. Wallis AD. Wheel estate: rise and decline of mobile homes. New York: Oxford University Press, 1991:12-3.

7. Lindell MK, Perry RW. Warning mechanisms in emergency response systems. International Journal of Mass Emergencies and Disasters 1987;5:150.

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