BlO—Lancaster Fanning, Saturday, March 31,1984
WASHINGTON Each spring
the deadly cycle repeats itself
somewhere. It begins with minute
crystals of snow transformed into
a single drop of water.
The process accelerates. Vast
quantities of snow turn to mush.
Tranquil streams swell into raging
torrents. Rivers overflow their
banks.
On the first line of defense are
the National Weather Service’s 13
River Forecast Centers scattered
across the country. Responsible
for issuing annual flood forecasts,
they need the most accurate,
timely information they can get on
the volume of water expected from
spring snow melt.
Until recently, the only reliable
measurements were taken by
ground-based workers who often
had to slog through waist-high
drifts and blinding blizzards to get
accurate measurements. This is
especially difficult in places such
as the Greant Plains, where
snowfields stretch for hundreds of
square miles and often contribute
to disastrous spring runoffs.
Now, instruments on a low-flying
airplane routinely estimate the
water content of snow on the
ground in most parts of North
Dakota, South Dakota, and Min
nesota.
The small aircraft, leased by the
Weather Service, flies over
designated areas well before the
first snowflake appears so it can
measure Earth’s natural gamma
radiation. The plane returns when
snow cover is heaviest.
Snow cover decreases or
weakens the gamma ray
emissions, so, by calculating the
difference in readings before and
after snowfall, scientists can
determine the amount on the
ground and its water content.
The instruments on the plane can
scan a 1000-foot-wide, 10-mile-long
path in about five minutes. “It
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Airplanes help fight floods
would take all day for a ground
based crew of a dozen men to get
meaningful data from a similar
area,” points out Thomas R.
Carroll, manger of the Airborne
Gamma Radiation Snow Survey
Program in Minneapolis.
“Following carefully designated
flight lines, we’ve been able to
estimate the water content of a
30,000 square-mile area in just
three days.”
The system has been so suc
cessful that the plane will fly
eastward this year to scan
potential trouble spots in Indiana,
Michigan, Ohio, New York, Ver
mont, and Maine. Parts of Canada
will also be surveyed with special
attention given to regions around
Lake Superior, which sometimes
help spawn spring floods.
But it’s usually rain, not snow,
that triggers the most deadly of all
water disasters the flash flood.
“Large thunderstorms that stall
and dump rain hour after hour
over the same area are the most
common culprits,” says Robert A.
Clark, director of the National
Weather Service’s Office of
Hydrology.
Appalachia is particularly prone
to flash flooding. “It’s because so
many communities there grew up
between the mountains on flood
plains,” observes Clark.
Help has arrived. The Weather
Service’s first automatic flood
warning system is functioning in
two Pennsylvania counties and the
region where Kentucky, West
Virginia, and Virginia meet, an
area of the Central Appalachians
containing some of the most
vulnerable valleys in the country.
The Integrated Flood Observing
and Warnings System will be
expanded this year to cover 80
counties. In a typical IFLOWS
setup, rain gauges equipped with
tiny radio transmitters are
positioned on hillsides near a
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community. Other automated
guages measure the depth and flow
of streams and rivers that could be
dangerous.
Signals from the gauges are
beamed to a computer that im
mediately analyzes the data,
enabling the Weather Service and
local civil defense people to issue
warnings and mobilize the com
munity against any threats.
IFLOWS got one of its first
serious tests last December when
heavy rains threatened areas near
Williamsport, Pa.
“We were able to get the word
out three to six hours before the
first flooding began, allowing civil
defense workers and flash flood
coordinators to take action and
spread the word,” recalls Albert S.
Kachic, the Weather Service’s
hydrologist for the Eastern
Region. “For a change everyone
was evacuated before waters were
seeping into living rooms.”
Budget constraints may hinder
further expansion of IFLOWS, but
other parts of the country could use
it too. Last year floods of all kinds
claimed more than 200 lives and
caused about $4.5 billion in
property damage.
At least half the deaths occurred
in automobiles. Explains
hydrologist Clark, “Some people
misjudge the depth and force of the
water, the car suddenly starts to
float, and then tips over with them
inside.”
His advice: “Don’t value the car
more than your life. When caught
in threatening waters, abandon
auto.”
Johy V. Byrne, administrator of
the National Oceanic and At
mospheric Administration, is
convinced that flash flood
programs such as IFLOWS will
help forestall such tragedies.
“Our goal is to provide reliable
advance warnings of flash floods
from 30 minutes to three hours in
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On a windy day have fun with this
butterfly finger kite
You 11 need a sheet of paper the
size of the pattern above sctssois
paints felt tip markers or crayons tuo
feet (60 cm} of string two drinking
straws some tape
Using the pattern above trace the
butterfly -kite onto the paper Then cut
it out Color it to look like your favorite
butterfly
Next lay the string across the middle
of the kite as shown You should have
advance,” he says. “This, com
bined with effective local action,
(^<TA
about four inches (10 cm) of string on
cine side and about 20 inches {5O cm)
on the other Now lay tuo -.traces onto
the kite to make an X Onle the part of
the string under the center of the X
(where the two straws cross) should be
touching the straws Tape the two
straws in place Then knot the string
around the center of the X
Hold onto the long end of the string
and run with your kite It will look like
a beautiful fluttering butterfly
could dramatically cut the loss
life and property.”
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