Wichita County, Texas Risk Assessment
Julie Hagen
10873930
Dr. Siebeneck
EADP 3035 (001)
17 March 2014
I.
Description of the Hazard
A tornado is an aggressively rotating column of wind that forms during a thunderstorm. As
rising warm air and descending cold air intersect, the result is a vortex of dangerous and
potentially deadly winds (Lindell, 122). Tornado season is generally considered to begin in
early-April and end in late June in the area covered by this assessment; although, tornadoes can
happen anytime—and anywhere. There is, however, an area of the United States more prone to
tornado hazards; this range has been deemed “Tornado Alley.” The American Meterological
Society Glossary of Meteorology defines tornado alley as:
“A term often used by the media to denote a zone in the Great Plains region of the central
United States, often a north-south oriented region center on north Texas, Oklahoma,
Kansas, and Nebraska, where tornadoes are most frequent.” (Meterology Glossary)
(Google Maps)
The map above illustrates what is normally considered “tornado alley.”
The following risk assessment covers tornado hazards in Wichita County, Texas. Wichita
County is located in north central Texas along the border of Oklahoma, with a population
exceeding 130,000 individuals (Wichita County Home Page). Being in tornado-alley, Wichita
County is at an especially heightened risk from tornado hazards.
(Benbennick)
(Google Maps)
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Tornadoes create an atypical risk in that their movement is incredibly unpredictable. This
puts the entire area at risk from tornadoes. There is nowhere in Wichita County where one does
not need to be concerned, warned, and prepared for a tornado.
Tornadoes’ strength is measured on the Enhanced Fujita Scale. This scale, as classified
by the Meteorology Glossary, is “A six-level numerical, damage-based classification of
estimated wind speeds. (Meteorology Glossary)” The original Fujita Scale, designed by Dr. T.
Theodore Fujita, was designed to categorize tornadoes based on their intensity and area (National
Weather Service). The scale designed, howver, was lacking in many respects. Dr. Fujita realized
this; the chart below is his “Modified” Fujita Scale (National Weather Service).
(National Weather Service)
Although the modified scale above is quite similar to the Enhanced Fujita Scale used today, it
was not quite enough of an adjustment. Before long, a committee convened to discuss the
creating the Enhanced Fujita Scale. The most important assumption of the new scale was that it
would have to be comparable to the original Fujita Scale so that the (at the time) current tornado
database could be left unchanged (National Weather Service).
The Enhanced Fujita Scale determines tornado strength by looking at the type and
construction of a structure pre-disaster and approximating what wind force was needed to
produce that sort of damage on such a building. Each particular category of structure has its own
specific number on an official list of twenty-eight indicators. Each of these indicators has its own
Degree of Damage (DOD), which included windspeed estimates for that grade of destruction.
These windspeed estimates can then be compared to the EF-Scale and used to determine the
intensity of the tornado. Following is a chart representing the Enhanced Fujita Scale:
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(The Enhanced Fujita Scale)
II.
Hazard History and Frequency
Wichita County has experienced a number of tornadoes in its past. The National Oceanic and
Atmospheric Administration’s National Weather Service has undertaken the task of compiling a
list of all of the tornadoes that have occurred in the United States. The list covers all known
twisters from 1950 to 2012. According to this record, there have been 52 tornadoes in Wichita
County since 1950. April 10th, 1979, Wichita County saw its largest tornado to-date. It was not
Texas’ deadliest, but it was Texas’ most destructive and costly. This EF-4 tornado was one of
many born during a tornado outbreak that later received the title “Red River Outbreak”
(LaNore). It touched down in Archer County and traveled into Wichita Falls, Texas, leaving a
path of destruction in its wake. The total property damage in Wichita County was estimated to be
somewhere around $400,000,000—this made it the most costly tornado in American history up
to that point (LaNore). Forty-two people were killed and around 1,800 more were injured
(LaNore). The tornado displaced between 10%-20% of the population (LaNore). To this day,
citizens in Wichita Falls, remember April 10th 1979 as “Terrible Tuesday”. Since then, there
have been no more widely destructive tornadoes (Severe Weather Database). The last one
recorded occurred in 2008. There was one injury and one fatality; the financial losses are
unknown (Severe Weather Database). The risk, however, still exists and is very present. As the
statistics will show, a tornado is very likely to occur again in Wichita County.
There is an 82.5% probability of a tornado occurring in Wichita County in any given
year. This was calculated by totaling the number of years that have passed between the first
recorded tornado (1951) and the current year. The result was 63 years (2014- 1951 = 63). Next,
that number is divided by the number of tornadoes that occurred within that span of time—52.
63 (the number of years) divided by 52 (the number of events) equals 1.21 (the recurrence
interval). Finding the probability is done by dividing one by the recurrence interval (1/R). One
divided by 1.21 (the recurrence interval) equals 0.8254 ≈ 82.5%. Also note that this probability is
the likelihood of any tornado occurring—this calculation was made disregarding tornado
strength/intensity. The likelihood of a tornado occurring in Wichita County is very likely. This
estimation is simply the chances—there is no guarantee that Wichita County will be struck by a
tornado. The numbers presented here are simply estimates and statistics.
The following table represents the probability of a tornado for each of the EF-scale
ratings.
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EF-Scale Rating
Number of Tornadoes
Recurrence Interval
Probability
EF-0
23
2.74
36.5%
EF-1
16
3.94
25.4%
EF-2
8
7.88
12.7%
EF-3
3
21
4.8%
EF-4
1
63
1.6%
EF-5
1
63
1.6%
Any Tornado
52
1.21
82.5%
(Information obtained from Severe Storm Database Files)
III.
Hazard Impacts
The entire population of Wichita County is at risk from tornadoes. Tornadoes can land anywhere
and move in any direction. Tornadoes, if powerful enough, destroy everything in their path. This
makes them especially dangerous and a risk to all. There is no community that does not need to
be prepared or mitigated for tornadoes. While all are at risk, there are some populations that are
at more risk than others. Those especially at risk include those living in structurally unsound
homes and/or mobile homes, the elderly, children, those with language barriers, tourists, military
personnel, and others.
Mobile homes are at an extreme risk from tornadoes. According to the United States
Census Bureau’s 2008-2012 Community Survey 5-year Estimates, 7.6% of the dwellings in
Wichita County are mobile homes (U.S. Census Bureau). This immediately puts 7.6% of the
population at a high level of risk. 13.4% of the population in Wichita County can be defined as
elderly (U.S. Census Bureau). 6.6% of the population are young (under 5 years old) children.
The elderly and children must receive special consideration in disaster situations because in
many cases they are highly dependent upon other individuals. Also, many of the warning
systems will go unheard by these two populations because of 1) they are unable to understand the
message, 2) they are unable to receive the message (technological disconnect), or 3) they choose
not to heed the message at all because they do not understand the seriousness of the situation).
Finally, one last particularly vulnerable population in Wichita County: military personnel.
Wichita Falls—the county seat and largest city in the county—is home to Sheppard Air Force
Base. Much of the county’s population is connected to this installation. Many of these
individuals are completely unfamiliar with the area and may be uninformed on how to prepare
for this hazard. Some may not even be aware with this hazard at all.
There are a number of critical facilities at risk in Wichita County. A critical facility is a
location or institution that, if disabled or destroyed, would incapacitate a community. Every
community has several critical facilities; without them, a community cannot be a thriving
establishment. A good example of a critical facility would be a community’s water source. For
instance, if a water source was not available for use in an area, a wildfire could produce
catastrophic damage—the said area would be left devastated. Another example of a critical
facility would be a nuclear power plant. If a power plant were to be damaged, the entire
surrounding community would be in enormous danger.
While somewhere there is an official list of the critical facilities in Wichita County, this
list is not open to the public. This is, of course, for a number of reasons. Revealing these risks
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would/could put the area at more risk—not from natural hazards, but from man-made hazards
(i.e. terrorism). However, there are a number of facilities that are clearly crucial to Wichita
County; one does not need an official list to determine that these structures are important.
Wichita Falls—the county seat and largest city in the county—is home to Midwestern State
University (MSU) and Sheppard Air Force Base. Both of these institutions are incredibly
principal to Wichita County. MSU has an enrollment of 5,870, and an on-campus population of
1,500 students (MSU Quick Facts). This is a huge number of people condensed into a small area,
putting the area at a greater risk. Sheppard Air Force Base has a daily population of 15,000
people (Base Information). Not only is this a large number of people in a small space, this is also
an Air Force Base—a very important asset to the United States. It is at a high risk from all types
of hazards—including tornadoes. The list of critical facilities continues: hospitals, police
stations, fire departments, local government buildings, power source facilities, the water
supply/system, communication channels, and so-on—any facility, that if damaged or removed
would leave the area incapacitated or disabled.
Wichita County’s greatest vulnerabilities are no different than any other community’s.
Areas of the county are mitigated for the next disaster—other areas are not. As always is, some
residents are prepared for the next storm, while others have not given preparedness any thought.
Wichita County must continue mitigating its critical facilities—there are so many to protect. The
population of Wichita County must be encouraged to prepare and instructed how to mitigate their
own homes. Too often, tornado awareness and preparedness is considered common knowledge—
something you learn about when you’re little. However, much of the population in Wichita
County are military personnel—individuals who did not grow up in tornado prone areas. Special
attention should be given to these individuals. The county needs to be sure they too receive and
understand the warnings. No one can know when the next storm will strike and it’s never too
early to mitigate for the next disaster.
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Annotated Bibliography
"Base Information." Sheppard Air Force Base. N.p., n.d. Web. 11 Mar. 2014.
http://www.sheppard.af.mil/library/baseinformation/index.asp. This site provided the
daily population numbers for Sheppard Air Force Base.
Benbennick, David. Map of Texas highlighting Wichita County. 2006. United States county map
locator, Wichita County. Wikipedia. Web. 10 Mar. 2014. This map clearly displays where
Wichita County is in the State of Texas.
"The Enhanced Fujita Scale." National Weather Service Weather Forecast Office. National
Oceanic and Atmospheric Administration, n.d. Web. 11 Mar. 2014.
http://www.crh.noaa.gov/arx/efscale.php. This article provided a useful chart
demonstrating the wind estimates used in the Enhanced Fujita Scale.
Google Maps. Tornado Alley. 2014. Google Map data, United States. Google. Web. 10 Mar.
2014. This map illustrated the generally accepted location of Tornado Alley.
Google Maps. Wichita County. 2014. Google Map data, United States. Google. Web. 10 Mar.
2014. This map effectively shows the shape of Wichita County, and goes well with the
Map of Texas highlighting Wichita County.
LaNore, Steve. "Wichita Falls: Giant tornado: April 10, 1979." Examiner. N.p., n.d. Web. 10
Mar. 2014. http://www.examiner.com/article/wichita-falls-giant-tornado-april-10-1979.
This article helped me in constructing a narrative for the tornado that struck Wichita
County in April of 1979.
Lindell, Michael K., Carla S. Prater, and Ronald W. Perry. "Principal Hazards in the United
States." Fundamentals of Emergency Management. United States of America: FEMA,
2006. 122-123. Print. This chapter provided a useful overview of tornadoes—how they
are formed and a few of the known facts about them.
"Meteorology Glossary." American Meteorological Society Glossary. N.p., n.d. Web. 8 Mar.
2014. http://glossary.ametsoc.org/wiki/Main_Page AMS's glossary is a helpful lexicon
of meteorological terms and expressions. It provided beneficial classifications for the
terms "tornado alley" and "Enhanced Fujita Scale."
"MSU Quick Facts." Midwestern State University. N.p., n.d. Web. 11 Mar. 2014.
http://mwsu.edu/about-mwsu/quickfacts/index. This site provided the enrollment and
student population numbers for Midwestern State University.
National Weather Service. "Storm Prediction Center Enhanced Fujita Scale (EF Scale)." NOAA's
National Weather Service. N.p., n.d. Web. 8 Mar. 2014. http://www.spc.noaa.gov/efscale/
NOAA's article on the Enhanced Fujita Scale (EF Scale) provides a valuable explanation
of the scale and how it functions. The graph provided is immensely useful and thorough.
"Severe Weather Database Files (1950-2012)." Storm Prediction Center WCM Page. National
Oceanic and Atmospheric Administration, n.d. Web. 10 Mar. 2014.
http://www.spc.noaa.gov/wcm/#torclim. This site included a data file, on which was
recorded every tornado to have occurred in the United States. I used this excel file to find
all of the tornadoes to have occurred in Wichita County and construct my own table
representing that data.
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U.S. Census Bureau "American FactFinder - Results." United States Census Bureau. U.S.
Department of Commerce, n.d. Web. 6 Mar. 2014.
http://factfinder2.census.gov/faces/tableservices/jsf/pages/productview.xhtml?src=bkmk.
This page was incredibly useful in finding out about the demographics of Wichita
County.
"Wichita County Home Page." Wichita County, Texas. N.p., n.d. Web. 16 Mar. 2014.
http://www.co.wichita.tx.us/ I used this site to find the approximate population of
Wichita County and the Wichita County emblem used on my coverpage.
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