The U.S. government, as the insurer of last resort, is
becoming increasingly vulnerable to the costs of natural disasters through
disaster declarations and spending by the Federal Emergency Management Agency
(FEMA). The number of presidential disaster declarations has generally increased
over the last half century, since the federal government has assumed continuous
responsibility for disaster aid. The federal government’s costs for natural
disasters are increasing both in terms of the federal budget and the gross
domestic product (GDP).
In July
1993, flooding on the Mississippi River wreaked havoc in Missouri. A total of
534 counties in nine states were declared federal disaster areas, and 168,340
people registered for federal assistance. Federal disaster aid has been on the
rise over the past 50 years for hazards, including floods, hurricanes and
earthquakes, as disaster response and mitigation efforts inadvertently have
encouraged development in high-risk areas. Image by Andrea Booher/FEMA
Photo.
Even when accounting for the exponential rise in GDP
over the last four decades, costs of natural disasters as a percentage of GDP
have more than tripled. This figure does not include the recent costs from
Hurricane Katrina, which will most likely be the most expensive disaster in U.S.
history, and has raised fundamental questions about high-risk land use.
The costs of natural disasters are driven by relatively few events — fewer
than 1 percent of disaster declarations are responsible for the majority of
costs. To reduce our nation’s exposure to natural disasters, we need to
determine what factors cause these few events to be so expensive.
In
general, the increase in cost correlates strongly with the large increases in
population and wealth in disaster-prone areas — in particular, East Coast
regions vulnerable to hurricanes and West Coast regions vulnerable to
earthquakes. By directly comparing disaster costs with local infrastructure
costs, event size and event frequency, however, more subtle relationships
emerge. Earthquakes, hurricanes, tornadoes and floods vary in frequency and
impact, but all have the capability of inflicting great damage and incurring
high costs to the federal government. U.S. hazard mitigation efforts and
disaster relief policies may inadvertently be contributing to these increased
costs by making us more vulnerable to expensive low-probability, high-cost
events. The political and social forces that support these counterproductive
policies will require a national change in how we perceive these disasters — a
change that hurricanes Katrina and Rita may help initiate.
Hurricanes
In
the last century, more than 170 hurricanes have hit the United States. Each year
in the Atlantic, approximately six hurricanes form, with one or two making
landfall on the United States. Hurricane frequency, strength and location are
affected by wind shear and sea-surface temperatures, both of which are part of
the greater El Niño-Southern Oscillation and multi-decadal cycles and patterns.
Despite this year’s highly active Atlantic hurricane season, there does
not appear to have been a significant increase in either the occurrence or the
severity of hurricanes over the last century; El Niño and La Niña provide an
explanation for which years have more or fewer. During an El Niño phase, the
sea-surface temperature anomaly in the Pacific Ocean is high, and the number of
storms in the Atlantic is low (in 1983 for example). During La Niña (the
opposite of El Niño), the anomaly is low and the number of storms is high (in
1988 for example).
Hurricanes are complex events, having a diverse set of
factors that drives damages in the areas they strike. Wind speeds, intense
rainfall, coastal storm surges, unpredictable paths and varying travel speeds
are among the characteristics that, together, define each hurricane event. In
general, the physical and temporal uniqueness of each hurricane event mean that
a large portion of the cost is the result of coincidental damages. Katrina, for
example, would not have generated so much flooding if it had not moved so slowly
over the coastal areas it affected.
The quantifiable storm
characteristic that is most strongly correlated with FEMA spending is population
density in the county where landfall occurred for large events, of Category 3 or
higher on the Safir-Simpson scale.
Hurricanes typically strike coastal
areas with strength, but weaken quickly after making landfall. Coastal areas,
already at risk of storm-surge flooding, are therefore subject to more forceful
winds. Increases in sea level, the inevitable landward migration of East Coast
barrier islands and the continued population shift to coastal areas on the East
Coast — which includes building high-value beachfront property — result in
higher damage costs from hurricanes that make landfall, though the number of
storms has not been increasing.
The more typical and less severe
Category-1 or 2 events, which are not hugely different from a harsh rainstorm,
show little or no correlation between FEMA spending and population density at
landfall. The more forceful (and rare) events, as with earthquakes above
magnitude 6.0, show a strong correlation between FEMA spending and population
density.
Earthquakes
Between 1989 and 2004, more than 180
earthquakes of magnitude 5 or greater have struck in the continental United
States. U.S. presidents have declared 11 of these events disasters.
As
with hurricanes, earthquake costs are determined by the population impacted. The
relationship between cost and population becomes apparent by comparing
earthquake size and population density between 1989 and 2004. When FEMA awarded
money to an area with a moderate or high population density (200 to 1,800 people
per square mile) affected by an earthquake of a magnitude greater than 6.5, the
funding increased with the population density irrespective of the magnitude of
the event (for example, the Northridge, Loma Prieta and Olympia quakes). When
FEMA awarded money to an earthquake-affected area with low population density
(20 to 200 people per square mile), the funding scaled with the magnitude of the
event (for example, the Landers, Petrolia, San Simeon, Clackamas, Napa and
Plattsburgh quakes). When FEMA awarded money to an earthquake-affected area with
a very low population density (between 0 and 20 people per square mile), the
funding was small — approximately $5 million — irrespective of the magnitude of
the event (such as with the Denali and Klamath quakes).
Tornadoes
Between 1989 and 2004, 155 disaster declarations have included the word
“tornado” in their description. The size of tornadoes is described by the Fujita
scale F0 to F5 (similar to the magnitude of an earthquake or the category of a
hurricane). A dramatic increase in reported F0 events occurred in the late
1980s, due to the introduction of Doppler 88-D surveillance radar (see story,
this issue); more events were detected and therefore more reported. After
removing the F0 events, the frequency of tornadoes over the last 20 years shows
no increase.
Most tornadoes occur in the central United States, where
population densities are low (between 20 and 200 people per square mile) and
relatively uniform. Tornadoes are also short-lived and affect only small areas.
For a tornado to incur a high cost, it must occur along with significant
flooding, or be a unique event in terms of what it destroys. On March 14, 1997,
for example, an F5 tornado destroyed an airplane hangar in Kentucky containing
expensive aircraft, and in another case, on May 4, 1999, an F5 event included a
cluster of 94 tornadoes occurring over two days in the Oklahoma City region.
In contrast to earthquakes and hurricanes, which are low-frequency,
high-cost events, tornadoes exemplify high-frequency, low-cost events. Tornado
events are similar in cost — typically less than $25 million — because they
occur frequently in areas of moderate to low population density.
Floods
Because
of the complex nature of rivers and their drainage basins, defining one standard
that successfully measures a flood is difficult. No scale exists for floods that
is similar to the magnitude scale for earthquakes, the Fujita scale for
tornadoes or the category system for hurricanes. Recurrence intervals are used
to measure the size of a flood, but the measurements are unique to a drainage
basin and do not allow comparisons among different drainage basins.
More
than 85 percent of U.S. counties have been declared federal disaster areas due
to floods in the past 50 years. With increasing development in floodplains, less
soil is available to soak up water, and flooding occurs more easily than ever.
Floods are such high-frequency, ubiquitous events that much has already been
done to ameliorate effects of common flooding disasters. On a local scale, the
cost-effectiveness of further flood control measures is questionable, especially
in areas not normally prone to flooding. On a national scale, however, floods
constitute a high portion of FEMA’s disaster obligations.
The 20 most
expensive floods in the United States show that costs roughly depend on
population density. However, five of these 20 floods do not follow this trend.
These outlying events are either extremely large, such as the Mississippi River
flood in 1993, or occurred in areas unprepared for a flood, such as Detroit,
Mich., in 2000. As with tornadoes, the relationship suggests that the driving
factor of the cost of expensive floods is the unusual nature of the event with
regard to its magnitude or its location.
Politics 
For extreme events, disasters can also be a test of governments, as
the world has witnessed with Hurricane Katrina. Disasters can bond a community
and provide opportunities for politicians to demonstrate leadership. In fact,
political support for incumbent politicians commonly increases following a
disaster. Conversely, if a government fails to respond properly, disasters can
also foment political unrest. On a small scale, they can change public opinion
of a leader, as illustrated by polls that showed lower approval ratings of
President Bush following Katrina. And on the larger scale, they can even result
in the overthrow of governments, as in the case of the 1972 Managua earthquake,
when the vast destruction contributed to the unrest that eventually led the
Nicaraguan people to oust General Somoza.
This seawall was built to protect homes from migrating coastlines
along the New Jersey shore. Such mitigation practices against moderate hazards
(supported with federal funds) can result in making regions more vulnerable to
large hazards, as it not only leads to the loss of the beach, but also
encourages the development of expensive infrastructure in high-risk areas. Image
courtesy of Gregory E. van der Vink.
In the United States,
usually the governor of the affected state makes a formal request for FEMA
assistance. Because a presidential disaster declaration is required before FEMA
can provide an area with federal disaster relief funding, political factors can
be introduced into the process. Based on records from 1952 to 2002, whether the
U.S. president and the state governor shared a party affiliation had no
significant effect on whether a disaster declaration would be approved or turned
down. Furthermore, Republican and Demo-cratic administrations have similar
approval and denial rates.
Although party politics do not seem to play a
major role in disaster funding, almost every election year shows a small spike
in the number of disaster relief requests approved — particularly when the
incumbent is running for reelection. Meeting symbolically with disaster victims
and approving requests for disaster funding are attractive opportunities for a
candidate to improve his or her public image. The minor year-to-year political
fluctuations are small, however, when viewed in the context of the overall
increase in disaster declarations with time.
Opportunity for
change
The timescale of human experience is short compared to
the recurrence interval of many natural phenomena. While we develop
infrastructure resilient to common events, such as routine seasonal weather, we
remain vulnerable to those events that occur less frequently or over longer
timescales. For example, a 6-inch snowfall in Boston, where such storms occur
annually, has much less impact than a 6-inch snowfall in Washington, D.C., where
such storms occur only once a decade.
When considering events that garner a FEMA disaster declaration, two
cost-frequency trends emerge. Earthquake and hurricane disasters are generally
high-cost, low-frequency events, whereas tornado and flood disasters are
low-cost, high-frequency events. The common factor for high cost is the extent
to which the disaster is unusual — either in terms of its recurrence interval or
its size. In other words, rare events such as earthquakes and hurricanes just
need to happen in populated areas to be costly. More frequent events, such as
tornadoes and floods, need to be unusually large or to occur in areas where they
usually do not occur.
The government
of Japan maintains this house, destroyed by a volcanic eruption, as a reminder
to improve awareness of such low-probability high-impact events. Image courtesy
of Gregory E. van der Vink.
In the United States, the
increase in costs to the federal government is most likely an unforeseen
consequence of our own disaster management policies. Mitigation strategies
require public support; public support requires awareness; and awareness usually
requires the occurrence of an event. As a result, resources are almost always
available to respond to the last event, but rarely to mitigate against the next.
We tend to view natural disasters as random unfortunate acts, rather than the
predictable consequence of high-risk land use. As a result, we rebuild
communities in the same high-risk areas — thus inadvertently using taxpayer
dollars to put more people in harm’s way.
In many cases, the influx of
federal assistance and rebuilding can actually boost the local economy —
resulting in more infrastructure and increased population in these high-risk
areas. Such efforts may, themselves, then become responsible for increased
costs. Whether it is cost-effective for communities to maintain a state of
readiness for low-probability events, such as a “storm of the century” or even a
“storm of the decade,” is questionable.
Mitigation against moderate
events can make us more vulnerable to large events. For example, a levee may be
enlarged to handle a 100-year storm rather than a 50-year storm. If the net
result of the rebuilding is four times as many people move into the area, the
risk ends up increasing. Paradoxically, our mitigation efforts, like our
response efforts, subsidize such high-risk land use as living on migrating
barrier islands, in floodplains or on active fault zones.
Consequently,
we are becoming more vulnerable to low-probability events. For any specific
individual city, this short-term solution is politically and, with federal
disaster relief, economically attractive. When such an approach is adopted
across a nation, however, the result increases already large costs to the
federal government.
Population trends, mitigation efforts and federal
disaster relief policies all contribute to encouraging high-risk land use and
ultimately to making our society more vulnerable to the costs of natural
disasters. Hurricane Katrina has created an opportunity to change this trend at
the national scale. If New Orleans is built to accommodate the inevitable next
extreme hurricane, it will set an example for future land-use management and
urban planning. Absent such change, the costs of natural disasters, and the
government’s liability, will simply continue to increase as we place more people
and infrastructure in harm’s way.
|
Forecasting hurricane damages |
 |
Geotimes Home | AGI Home | Information Services | Geoscience Education | Public Policy | Programs | Publications | Careers  |