Floods also may become more frequent (see Section 126.96.36.199). All rivers are susceptible to flooding, and nearby populations are potentially vulnerable. In the United States, floods are the most frequent natural disaster, as well as the leading cause of death from natural disasters. The mean annual loss of life is estimated to be 146 deaths yr-1 (National Weather Service, 1992; Patz et al., 2000). In 1997, the Canadian Red River flood displaced more than 25,000 people (Francis and Hengeveld, 1998; Manitoba Water Commission, 1998).
During a flood, disaster relief workers may be at risk of injury. For example, 119 injuries were identified from medical claims of people engaged in sandbagging activities in the 1993 Midwest floods. Heat-related injury or illness (HRI), which occurs when the body can no longer maintain a healthy core temperature, was the most frequently reported injury diagnosis; a total of 23 HRI (19.3% of the 119 total injuries) were reported (Dellinger et al., 1996). HRI therefore is a potential problem in disaster relief situations, particularly if high ambient temperature and high humidity exist. Following a flood, flood victims may be at risk of post-traumatic stress disorder (PTSD) and depression, which are risk factors for suicide. Krug et al. (1998) showed that suicide rates increased from 12.1 to 13.8 per 100,000 population in the 4 years after floods. Inundations of sites that contain toxic wastes, sewage, animal wastes, or agrochemical products may result in immediate human exposure to wastes from floodwaters, contamination of edible fish, and long-term contamination of flooded living structures (see Sections 188.8.131.52 and 184.108.40.206.2.2).
Climate models currently are unable to project accurately how hurricanes will change in the future. Today, an average of two hurricanes make landfall each year along the coastline of the continental United States (Hebert et al., 1993). There has been considerable interdecadal variability in the number of landfalling hurricanes in the United States (Pielke and Pielke, 1997). The Federal Emergency Management Agency (FEMA) declared fewer than 20 natural disasters annually in the 1950s and 1960s but more than 40 yr-1 in the 1990s (Miller et al., 2000). Hurricanes' strong winds and heavy rains cause injury, death, and psychological disorders (Logue et al., 1979; Patz et al., 2000). A total of 20-30% of adults who lived through Hurricane Andrew showed evidence of PTSD at 6 months and 2 years after the event (Norris et al., 1999).
Milder winter temperatures will decrease heavy snowstorms but could cause an increase in freezing rain if average daily temperatures fluctuate about the freezing point. It is difficult to predict where ice storms will occur and identify vulnerable populations. The ice storm of January 1998 (see Section 220.127.116.11) left 45 people dead and nearly 5 million people without heat or electricity in Ontario, Quebec, and New York (CDC, 1998; Francis and Hengeveld, 1998; Kerry et al., 1999). The storm had a huge impact on medical services and human health. Doctors' offices were forced to close, and a large number of surgeries were cancelled (Blair, 1998; Hamilton, 1998). One urban emergency department reported 327 injuries resulting from falls in a group of 257 patients (Smith et al., 1998b).
Although some evidence is available regarding increases in the intensity and frequency of some extreme weather events, it is not yet clear how tornadoes will be affected. The tornado of July 31, 1987, in Edmonton, Alberta, killed 27 people and injured 253 (Etkin et al., 1998). Trends in the United States appear to show a decreasing number of deaths since the 1950s, although data on the number of events causing deaths do not show a trend (Kunkel et al., 1999). Godleski (1997) reports that persons who endure tornadoes often experience a variety of stress responses, including depression, acute and post-traumatic stress disorders, substance abuse, anxiety, and somatization.
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