CHAPTER 1
BACKGROUND AND OVERVIEW OF THE EVENT
A decaying tropical system, previously known as Tropical Storm
Alberto, produced torrential rainfall which resulted in some of
the worst flooding ever observed across portions of the States
of Georgia, Alabama, and Florida during July 1994. Alberto, the
1994 Atlantic Hurricane Season's first named tropical system,
came ashore near the Florida Panhandle town of Destin at about
1500 Universal Coordinated Time (UTC) on July 3. The winds associated
with the tropical storm caused only minor damage and no casualties,
as maximum sustained winds of around 65 mph (55 knots) were briefly
observed at the time of landfall. The highest storm surge was
estimated at 5 feet near the point of landfall (Destin, Florida).
No reports of tornadoes were confirmed in association with Alberto
or its remnants.
As the tropical storm's winds rapidly diminished, attention
was quickly and appropriately turned to the threat of heavy rainfall
associated with the deep tropical moisture being transported by
the remnants of Alberto. Indeed, over the course of the 4 days
following landfall, the forward motion of the remnants of Alberto
slowed and halted, only to loop back over the same area already
traversed before finally dissipating. It was this meandering motion
which resulted in record-breaking rainfall, including a storm
total of over 27 inches at Americus, Georgia, more than 21 inches
of which fell in a 24-hour period. The torrential rainfall led
to exceptional flooding across central and western Georgia, southeastern
Alabama, and the Florida Panhandle. Five river basins were particularly
hard hit (see Figure 1-1 ): (1) the Flint
River Basin in western Georgia, (2) the Ocmulgee River Basin in
central Georgia, (3) the Chattahoochee River Basin along the Georgia-Alabama
state line, (4) the Choctawhatchee River Basin in Alabama, and
(5) the Apalachicola River Basin in Florida.
Figure 1-2 shows the counties that
were Presidentially declared disaster areas. Most of the declared
counties were concentrated along the five rivers (and their tributaries)
mentioned in the section above. A total of 78 counties were declared
Federal disaster areas, including 55 in Georgia, 10 in Alabama,
and 13 in Florida.
The flooding took a significant toll on human life, as a total
of 33 persons perished. Of that total, 31 deaths occurred in Georgia,
while the other 2 occurred in Alabama. Many of the fatalities,
as is typical with flood events, occurred as a result of flash
flooding; and most occurred in vehicles. In addition, approximately
50,000 people were forced from their homes due to the flooding.
More than 18,000 dwellings were damaged or destroyed by the floods,
and nearly 12,000 people applied for emergency housing. In Macon,
Georgia, the fresh water supply to nearly 160,000 people was disrupted
when the water treatment plant, located along the banks of the
Ocmulgee River, was flooded. Some residences were without fresh
water for as long as 19 days. In addition, thousands of people
and pieces of equipment were engaged in various flood-fighting
efforts throughout the three-state area impacted by the flooding.
Dozens of Federal, state, and local government agencies, private
organizations, as well as various volunteer groups, were heavily
involved in the massive mobilization of resources. Federal agency
participation included, but was not limited to, the
Federal Emergency Management Agency (FEMA) ,
U.S. Army, U.S. Army
Corps of Engineers, U.S. Department
of Transportation, U.S. Department
of Housing and Urban Development,
and Small Business Administration.
With respect to property damages, the estimates are nearly $750
million across the States of Georgia, Alabama, and Florida as
a result of this flood event. In addition to the more than 18,000
dwellings damaged or destroyed, hundreds of bridges and well over
1,000 roads sustained damages. Also, 218 dams (most of them small
dams located in Georgia) were damaged by the flooding, many of
which failed altogether. Agricultural losses accounted for approximately
$100 million. In the States of Georgia, Alabama, and Florida combined,
more than 900,000 acres of crops were affected by the flooding.
Georgia and Alabama suffered the greatest crop losses with more
than 400,000 acres in each state impacted. In all three states,
peanuts and cotton were the commodities most severely affected.
Livestock losses were also significant, especially to poultry,
with as many as 250,000 chickens reportedly lost to the flooding.
While Tropical Storm Alberto will not likely be remembered for
its wind nor its storm surge, it most certainly will be remembered,
especially amongst Georgians, for its rainfall and flooding. The
following sections describe, in some detail, the tropical weather
system that was Alberto, from its origin as a tropical wave over
western Africa to its dissipation as a tropical depression over
central Alabama.
The tropical weather system which would eventually become Alberto
was first detected as a tropical wave over western Africa on Saturday,
June 18. Moving on a westerly course, the wave traversed the tropical
Atlantic Ocean uneventfully until it neared the Virgin Islands
when some increase in thunderstorm activity occurred. However,
thunderstorm activity diminished 2 days later when the wave neared
the Bahamas.
The wave continued moving westward and, on June 29, moved across
Cuba where thunder- storm activity rapidly increased; and a very
weak circulation became evident. With the system located in the
vicinity of the western tip of Cuba, a
National Oceanic and Atmospheric Administration (NOAA) reconnaissance
aircraft was sent to investigate the disturbed weather area. Based
on the information obtained from that flight, NOAA's National
Hurricane Center proclaimed the system the 1994 Atlantic Hurricane
Season's first tropical depression on June 30 (see
Figure 1-3 for Alberto's track). Still moving westward, the
poorly organized depression cleared Cuba then took a turn to the
northwest into the Gulf of Mexico where it became better organized.
Reconnaissance aircraft data indicated that the depression then
strengthened to a tropical storm at approximately 0000 UTC, July
2, at which time the system was named Tropical Storm Alberto.
Alberto then began to track northward towards the Florida Panhandle
as it continued to gradually intensify. Peak intensity was reached
just prior to landfall when Alberto's sustained winds were 60-65
mph (55 knots), and the central pressure of the storm was near
993 millibars (mb). Alberto's center made landfall near the town
of Destin, Florida, at 1500 UTC on Sunday, July 3, approximately
39 hours after becoming a tropical storm. On Sunday evening (0000
UTC July 4), just a few hours after landfall, the storm was down-
graded to a tropical depression. For the next 2 days after landfall,
the remnants of Alberto moved north-northeastward at a progressively
slower forward speed, eventually coming to a halt near Atlanta,
Georgia, on July 5. The remnants of Alberto then began to backtrack,
moving westward into east-central and then central Alabama. The
system dissipated during the evening hours of Thursday, July 7,
over central Alabama.
With respect to the antecedent conditions prior to Alberto's
arrival, much of the spring of 1994 was quite dry throughout the
Southeast. In fact, many southeastern residents were undoubtedly
concerned about recurring drought conditions, similar to those
which occurred during the summer of 1993. However, June 1994 brought
much wetter conditions over most of the Southeast. In fact, the
rainfall in June resulted in some localized flash flooding and
even some limited, mostly minor river flooding across portions
of the Southeast. At the beginning of June, moderate-to-extreme
drought conditions existed across a considerable portion of the
Southeast, especially over Georgia and South Carolina. But due
to the wet June, by the time of Alberto's arrival in early July,
hydrologic conditions across much of the Southeast had returned
to near normal, or just slightly drier than normal. Thus, the
wet June certainly was a factor in the evolution of the July flood.
There is little question as to the cause of the torrential rainfall
associated with Alberto and its remnants. While heavy precipitation
accompanies nearly every tropical system, excessive rainfall was
produced by the remnants of Alberto due to two main factors: (1)
the slow, forward motion of the system and (2) the meandering,
looping (retrogressive) nature of the system's track. These characteristics
contributed to rainfall accumulations that, in several places,
exceeded 20 inches. Noteworthy was Americus, Georgia, which received
a storm total of 27.61 inches (July 3-9), including a 24-hour
total of 21.1 inches (July 5-6). While such amounts are certainly
not unprecedented, they are nonetheless rare, even with decaying
tropical systems.
Figure 1-4 shows the
National Weather Service (NWS) Climate Analysis Center's
storm total isohyetal analysis. The heaviest rains (16 inches
or greater) fell in a relatively narrow band across southwestern
Georgia and southeastern Alabama. Some of the worst flash and
urban flooding occurred in this excessive rainfall area, as evidenced
by the 15 fatalities that occurred in the vicinity of Americus,
Georgia. In contrast, a far larger area was inundated with 8 or
more inches of rainfall. It was this heavy precipitation that
fell over a fairly large area that generated tremendous runoff
and resulted in the widespread river flooding.
Figure 1-5 is a composite figure combining
portions of Figures 1-1 through 1-4. This figure shows the inland
track of Alberto and its remnants, the area enveloped by the 8-inch
rainfall isohyet, the major rivers affected by flooding, and the
counties that were Presidentially declared disaster areas.
As is typical with flood events of this magnitude, widespread
major river flooding evolves from flooding which first manifests
itself in the form of urban, small stream, and flash flooding.
Such was the case with this flood. The first reports of flooding
included flooded roads, underpasses, culverts, and the like. Since
the heaviest rains were generally close to the path of the center
of Alberto, the pattern of flooding essentially followed the path
of the storm center. Thus, flooding first broke out across portions
of the Florida Panhandle and southeast Alabama, then across southwestern
portions of Georgia. Flooding later broke out across much of the
remainder of western and central Georgia. As rainfall persisted
and soils became saturated, small streams and rivers began to
overflow; and small dams were threatened by the tremendous inflow
into the reservoirs behind them. Some small, unregu- lated earthen
dams began to fail, and reports of road and bridge washouts became
common.
Within a day after landfall, the forward motion of Alberto slowed.
The rains continued, and some of the larger rivers began to approach
flood stage at various locations. Late on July 5, with the center
of Alberto coming to a halt near Atlanta, portions of numerous
large rivers exceeded flood stage; and river flooding became more
widespread and significant. By the morning of July 6, some locations
had observed record flooding; and the first crests began to appear
along some of the smaller rivers and at some upstream locations
along the larger rivers. Alberto's movement became erratic--the
system was now moving westward, looping back over a portion of
its previous track. Additional rainfall caused a progression in
flooding from urban and small stream flooding to river flooding.
By July 7, as Alberto's center drifted into central Alabama, rainfall
finally diminished, both in intensity and in areal coverage. Tremendous
volumes of water were now moving down major river systems in portions
of Georgia, Alabama, and Florida: the Flint, Ocmulgee, Chattahoochee,
Choctawhatchee, and the Apalachicola Rivers. River flooding peaked,
both in terms of coverage and severity, during the period July
6-15; but flooding would continue along portions of some rivers
until close to the end of July.
By far, the worst flooding occurred along Georgia's Flint and
Ocmulgee Rivers and their tributaries. Some of the hardest hit
cities along these rivers include Albany, Macon, and Montezuma.
Across the entire three-state area impacted by the flooding, 17
NWS river forecast locations set new record flood stages, some
breaking the old record by 5-7 feet. In all, 47 NWS river forecast
locations exceeded flood stage. Crests of 5-15 feet above flood
stage were common, while portions of some rivers observed crests
that exceeded flood stage by more than 20 feet. The NWS offices
involved in the flood event across the three-state area issued
657 watches, warnings, and statements related to the event; and
the Southeast River Forecast Center (SERFC)
issued 238 NWS internal river forecasts.
Figure 1-1 Major river basins impacted by flooding in July
1994 as a result of Alberto: Flint, Ocmulgee, Chattahoochee,
Choctawatchee, and Apalachicola River Basins.
Figure 1-2. A total of 78 counties were declared Federal
disaster areas: 55 in Georgia, 10 in Alabama, and 13 in Florida.
Figure 1-3. Alberto's track, July 1994.
Figure 1-4. Storm total precipitation during the period July
3-9, 1994 (Americus, GA: 27.61" storm total).
Figure 1-5. Composite showing Alberto's inland track (dashed
line), the 8-inch isohyet, the 78 counties declared Federal
disaster areas (shaded), and the five major river systems.
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