Geoscience Reference
In-Depth Information
floods
ever was incurred as a result of the Missis-
sippi River flood of 1993.
Deaths in North America from river
floods have dramatically decreased in the
past few years because of improved warning
systems. This is not so for deaths from hur-
ricane storm surge flooding and tsunami
flooding, as seen in Asia recently. Cyclone
Nargis killed 133,000 people in Myanmar in
2008, and the great Indian Ocean tsunami
killed 200,000 people in 2004. The mas-
sive Indus River floods that hit Pakistan
in 2010 (said to be the worst in a thousand
years) inundated about 20% of the country,
destroying over a million homes and leav-
ing over twenty million people homeless—
astounding numbers.
Areas likely to be at risk from increased
floods are the American Southwest (flash
floods), the Northeast (spring floods), and
the Northwest (more fall and winter flood-
ing). Northern to northeastern Europe will
also be at increased flood risk.
Admittedly, the warming atmosphere
is not the only cause of increased flood
damage. Other causes include increases
in human population (which means there
is more property to damage), in the value
of property, in the amount of construction
in lood-prone areas, and in the area of im-
permeable surfaces (e.g., concrete), as well
as misplaced trust in engineering systems
(e.g., levees).
Increased atmospheric temperatures will
lead to increased water content in the at-
mosphere. For every increase of 1 degree
Celsius (1.8 degrees Fahrenheit), the at-
mosphere can hold about 7% more water.
As winters warm, more of the precipita-
tion will be in the form of rain rather than
snow, leading to different runoff patterns,
another factor that will undoubtedly con-
tribute to more frequent flooding. Changes
in climate will be quite complex, and as
noted earlier, they are very difficult if not
impossible to predict on a local scale. Some
changes in rainfall patterns will be sea-
sonal. For example, Germany is expected
to be drier in the summer and wetter in the
winter as global change proceeds.
More important perhaps than average
and seasonal rainfall changes is the like-
lihood of more extreme rainfall events,
which will lead to more flooding. The four-
teen inches of rain that fell on the first
weekend of May 2010 in Nashville is a
good example of an extreme event. The
frequency of intense bursts of rain will be
higher, even in arid areas.
For the insurance industry the impor-
tance of increased flooding is clear. Indus-
try representatives note that flooding ac-
counts for about one-tenth of all property
insurance payouts, one-third of all eco-
nomic losses from natural catastrophes,
and more than half of all deaths from such
catastrophes. The costliest insurance loss
