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FALL 1997— VOLUME 5, NO. 1

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Hurricanes and Societal Impacts: Are We Prepared?

House damaged by hurricane

Extensive damage occurred when Hurricane Fran slammed into the North Carolina coast in 1996, destroying many beach front properties. The Category Three Hurricane caused extensive flooding from the Carolinas to Pennsylvania. As more people build in vulnerable coastal areas, damage costs will increase when hurricanes make landfall in those regions.
 Agnes. Andrew. Bertha. Camille. Gilbert. Hugo. Opal. Roxanne. This list of names holds little significance to much of the world's population, but to the people who endured the fury of these hurricanes, the names recall a host of devastating memories. The impacts of these violent tropical storms spawned over the warm waters of the world's oceans reach well beyond the coastal areas they pummel with wind and water. The storms, which are the costliest of all natural disasters in the United States, exact a heavy price in lives and property, and affect the way people live.

The societal impact of hurricanes is one topic researched by scientists at the National Center for Atmospheric Research's (NCAR) Environmental and Societal Impacts Group (ESIG). While much of NCAR's research focuses on atmospheric phenomena itself, the social scientists who work in ESIG examine the impacts of society on the environment and the environment on society so that people can better cope with and understand what Mother Nature has to offer.

Mother Nature's wrath can be cruel. The balmy temperatures and warm seas of the world's tropical oceans are both the vacationer's dream and the birthplace of tropical cyclones and hurricanes. As the sun heats the oceans of the tropics, water evaporates and forms clouds which can grow into the thunderstorms that give rise to tropical storms or hurricanes. If atmospheric conditions are right, the clouds begin to rotate counterclockwise due to the earth spinning on its axis; this is called the Coriolis effect. The characteristic pinwheel shape of a hurricane or tropical storm when viewed on a satellite image is the result. The bands of spinning clouds hold flood-inducing rain while furious winds whip the ocean's surface into enormous waves. With storm surge and winds spanning up to thousands of square miles, hurricanes unleash the brunt of their power when they make landfall.

To determine a hurricane's damage potential, scientists use a scale developed in the 1970's by Robert Simpson, a meteorologist and director of the National Hurricane Center, and Herbert Saffir, a consulting engineer in Florida. The scale has five categories, with Category One being the least intense and Category Five the most intense. Storms that fall below the strength of a Category One storm but have winds greater than 39 m.p.h. are Tropical Storms. Public officials use the designation of a storm's intensity to make decisions about safety and risk (see Saffir-Simpson Scale of Hurricane Intensity).

Why worry about what can't be controlled? Although hurricanes develop every year between June and December, they don't always make landfall, or reach shore, in a crowded area, and not every hurricane is of extreme intensity. ESIG scientists like Roger Pielke, Jr. believe we have much to worry about, however. As a social scientist with a keen interest in how policy and science are connected, his goal is to help make science useful, relevant, and more focused. He examines the value in forecasting hurricanes, floods, blizzards, and other weather events in terms of understanding risks and the creation of policies that reduce society's vulnerability to damaging losses.

According to Pielke, "the physical dimensions of hurricanes are captured in questions like the following: How often do hurricanes strike a particular community? What is the expected intensity of these storms? Will the future climate resemble or differ from the past? The societal aspects of hurricane risk pose other questions. Do members of a community carry adequate insurance? Are evacuation plans in place? Are building codes implemented and enforced?"

The people who make policy decisions about such questions often do not understand the science involved in making sound decisions, and scientists don't always understand what those same policy makers need to hear. "Scientists and policy makers need each other. Scientific answers need to be translated to see their value in a bigger context," says Pielke.

One example of the confusion between science and policy that Pielke found is a 1995 congressional report on federal disaster assistance which incorrectly concluded that strong hurricanes have become more frequent in recent decades. The report stated that hurricanes "have become increasingly frequent and severe over the last four decades as climatic conditions have changed in the tropics." In fact, scientific data and the historical record show the opposite.

Although the cost of damage has increased significantly in recent decades, the frequency and severity of storms has actually decreased. The period from the 1940's through the 1960's saw much higher hurricane activity than the 1970's to the present. Some policy makers believed that increasing damage is caused by more storms, when in fact the damage represents increases in population along the coast from Texas to Maine, the increasing number of insured properties, and the increased value of those properties. Every time a hurricane makes landfall, there is more at stake.

A storm that made landfall many years ago would cause significantly greater economic and physical damage today simply because the dollar is worth less now and there are more people and property in vulnerable coastal locations. For example, in 1990 Dade and Broward counties in south Florida were home to more than the total number of people who lived in all 109 counties from Texas through Virginia along the Gulf and Atlantic coasts in 1930, says Pielke.

Sometimes people put too much faith in what science has accomplished, putting communities at even greater risk. Pielke found one 1996 news article with the lead "Great killer hurricanes, like those seen in decades past, appear to be gone forever from the shores of the United States because of early warning systems." Yet just one year earlier, in 1995, the director of the National Hurricane Center wrote that a "large loss of life is possible" unless significant policy change activities occur. Pielke has come to the troubling conclusion that the United States is more vulnerable today to hurricane impacts than it has been in recent decades because society accepts the risk of living in hurricane-prone areas without acknowledging the magnitude of that risk.

Take Hurricane Andrew for example. Not only was it a powerful Category Four hurricane with sustained winds over 130 miles per hour, it also made landfall in a populated area of Florida. While loss of life was fewer than 50 people, the cost of the damage was over $30 billion.

The cost, however, could have been significantly less had society done a better job of preparing for such a hurricane. Even though Dade County, Florida, has some of the toughest building codes in the United States, the damage was devastating. The reason? The codes were not strongly enforced. Some insurance industry estimates suggest that failure to enforce the codes accounted for between $4 and $6.5 billion of the insured losses related to Andrew.

Andrew is considered one of the worst natural disasters in history and the costliest ever in the United States, but the cost would have been far higher had the hurricane tracked slightly north and hit Miami. After Hurricane Andrew, Dr. Robert Sheets, the director of the National Hurricane Center, testified before Congress that "We were lucky." The luck is simply that had Hurricane Andrew tracked a mere 20 miles north of where it made landfall, two studies estimate that losses could have exceeded $60 billion.

Pielke wants people to make a stronger practical link between the atmospheric science of hurricanes and their impact on society. He wants to translate the science so that it can be used to make effective decisions to save lives and property. He is a good person to make such translations because he maintains a close working relationship with an atmospheric scientist who researches hurricanes--his father. Pielke and his father, Roger Pielke, Sr., recently co-authored a book titled "Hurricanes: Their Nature and Impacts on Society," (John Wiley and Sons Press, 1997) which examines both the physical phenomena of hurricanes and how the storms affect people.

Some scientists are predicting that based on changing atmospheric conditions, the U.S. may be entering another active hurricane period like that of the decades prior to the 1970's. If those scientists are correct in their predictions, the United States may have to pay for devastating damage in coming years. Factors which affect hurricane intensity and frequency include elements such as rainfall in West Africa, stratospheric winds, sea surface temperatures, and the presence or absence of El Nino, a huge pool of warm water that develops in the eastern Pacific and changes weather patterns worldwide. El Nino tends to decrease Atlantic hurricane activity. In August 1997, with a major El Nino in progress, there wasn't a single Atlantic tropical storm or hurricane for the month--a first since August 1961.

To anticipate the future, one must often examine the past. Pielke went back through hurricane data from 1900 to present and estimated losses from hurricanes as if those hurricanes made landfall in 1995. In other words, he used 1995 dollar values, population figures, and property values or wealth to determine what such hurricanes would cost today. He found that even though intense hurricanes of Categories three, four, and five make up only 21 percent of the storms making landfall in the United States, they account for 83 percent of the damage costs. The 52 intense hurricanes that struck the United States from 1925 to 1995 resulted in an average of $5.5 billion per storm. Hurricane Andrew actually dropped into the number two position because the 1926 SE Florida/Alabama hurricane, a Category Four like Andrew, would have cost more than double that of Andrew if it made landfall today.

So what can society do? Hurricane-dissipating technology is the stuff of science fiction, so scientists strive to improve forecasting and early warning systems. With that knowledge public officials must make decisions about building codes, evacuation plans, insurance requirements, and potential taxpayer costs with an appropriate understanding of the risks of habitation in hurricane-prone areas. Ultimately, everyone shares the cost if those decisions are not made wisely. Roger Pielke, Jr. works to impart that wisdom.

Saffir-Simpson Scale of Hurricane Intensity

Category One Hurricane:

Winds 74 - 95 m.p.h. Storm surge generally 4 - 5 feet above normal. No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some coastal road flooding and minor pier damage.

Category Two Hurricane:

Winds 96 - 110 m.p.h. Storm surge generally 6-8 feet above normal. Some roofing material, door, and window damage to buildings. Significant damage to shrubs and trees with some trees blown down. Considerable damage to mobile homes, poorly constructed signs, and piers. Small craft in unprotected anchorages break moorings. Hurricane Bertha of 1996 was a Category Two hurricane when it hit North Carolina.

Category Three Hurricane:

Winds 111 - 130 m.p.h. Storm surge generally 9 - 12 feet above normal. Some structural damage to small residences and utility buildings. Foliage blown off trees and shrubs and large trees blown down. Mobile homes destroyed. Low-lying escape routes are cut by rising water 3 - 5 hours before arrival of hurricane center. Flooding near the coast destroys smaller structures and larger structures damaged by floating debris. Terrain continuously lower than five feet above mean sea level may be flooded inland eight miles or more. Hurricanes Fran and Roxanne were Category Three storms.

Category Four Hurricane:

Winds 131 - 155 m.p.h. Storm surge generally 13 - 18 feet above normal. Some complete roof structure failures on small residences. Shrubs, trees, and all signs blown down. Complete destruction of mobile homes. Extensive damage to doors and windows. Low-lying escape routes may be cut by rising water 3 - 5 hours before arrival of the hurricane center. Major damage to lower floors of buildings near the shore. Terrain lower than ten feet above sea level may be flooded, requiring massive evacuation. Hurricanes Andrew and Hugo were Category Four storms.

Category Five Hurricane:

Winds greater than 155 m.p.h. Storm surge more than 18 feet above normal. Complete roof failure on many residences and buildings. Some complete building failures with small utility buildings blown away or over. All shrubs, trees, and signs blown down. Complete destruction of mobile homes. Severe and extensive window and door damage. Low-lying escape routes may be cut by rising water 3 - 5 hours before arrival of the hurricane center. Major damage to lower floors of all structures located less than 15 feet above sea level and within 500 yards of shoreline. Massive evacuations of areas on low ground within 5 - 10 miles required. Hurricane Gilbert of 1988 and Hurricane Camille of 1969 were Category Five storms.

(This information was adapted from the National Hurricane Center Website@ http://www.nhc.noaa.gov)


Use the World Wide Web to Find Out More
The World Wide Web is an excellent resource for further research on hurricanes. Just use any search engine and type in either the general topic of "hurricanes" or a specific hurricane and you will find numerous entries. Some good starting points are the following sites:

  • The National Hurricane Center at http://www.nhc.noaa.gov provides satellite radar imagery, historical information, educational materials, current forecasts and reconnaissance data, and links to other sites.
  • The Hurricane Hunters Home Page at http://www.hurricanehunters.com/ allows browsers to take a cyberflight into the eye of a hurricane.
  • What are Hurricanes at http://www.atmos.uiuc.edu/dept/ based at the University of Illinois at Urbana-Champaign provides general information about all aspects of hurricanes and links to other useful sites.
  • The Federal Emergency Management Administration site at http://www.fema.gov/library/ includes photos and video archives of hurricanes and other natural disasters.

For more information about societal impacts of hurricanes and the research conducted at the National Center for Atmospheric Research you can browse Roger Pielke's home page at http://www.dir.ucar.edu/esig/HP_roger.html


Science Now is jointly published by the Walter Orr Roberts Institute at the University Corporation for Atmospheric Research and SIRS Publishing, Inc. (Social Issues Resources Series.) Science Now is published three times during the school year and is distributed to SIRS subscribers. Comments and questions should be directed to Joyce Gellhorn via Internet at jgellhorn@sprynet.com. You can also contact your SIRS representative or write to:

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Caroline Hanson

Scientific Editors:
Roger A. Pielke, Jr., ESIG

Bob Henson, UCAR Communications,
Cynthia Schmidt, UCAR Corporate Affairs


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