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One of the
questions the National Oceanic and Atmospheric Administration
(NOAA) regularly fields from the public is, apparently,
why the government isn't doing more to prevent hurricanes.
Suggestions range from dropping moisture-absorbing gel
into the storm to coating the ocean's surface with some
sort of substance that prevents water from evaporating,
and from seeding the clouds with silver iodide (this
one was actually attempted) to blowing the storms away
from shore with giant windmills.
While we
might not be close to preventing them, we can predict
hurricanes earlier than ever before, and we can also
measure their effects with greater precision - particularly
the extent of coastal erosion they cause. Storm damage
can be all too apparent to those whose homes and livelihoods
lie in the path of a hurricane, but the larger effects
and the long-term changes to the shoreline have not
always been clear from the ground. Assessing how the
coast is holding up can dictate what steps to take next,
and it has immense economic implications. For example,
cities that have undertaken beach replenishment projects
- adding sand to widen the beaches - were especially
anxious after Hurricane Isabel in September to know
the current shape of their shorelines.
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| Hurricane
Isabel close to making landfill; image taken September
18, 2003, at 7:53 a.m. EDT |
The practice
has always been controversial; many argue that beach
replenishment, or beach nourishment as it's sometimes
called, simply washes away money, because the processes
of erosion that are stealing the beach in the first
place will inevitably claim the added sand as well.
Others, such as engineers in Virginia Beach who watched
as Isabel threatened to remove much of the sand they'd
recently spent $125 million to place in front of hotels
and tourist spots, view the practice as an insurance
policy.
The newly
expanded beaches, rather than the expensive real estate
behind them, absorbed the brunt of Isabel's waves. In
the past, storms have sometimes left such severe destruction
that it was difficult for those assessing the aftermath
to identify landmarks and damaged structures, or even
to hazard a guess as to where some manmade structures
had been located; GPS and GIS technology allow far better
orientation.
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| Comparison
of the new inlet created by Hurricane Isabel near
Cape Hatteras Village, NC. The back-and-white images
was taken in 1998. The color image as taken September
19, 2003, by a NOAA aircraft. |
Vastly improved
mapping technologies, too, are allowing us to track
- and sometimes to predict - not only the violent and
sudden changes from a Hugo or an Isabel but also more
subtle patterns of long-term erosion and water-level
changes. Ideally, seeing these trends can help guide
land-use planning and new development. It also allows
time for erosion control measures to be implemented
for existing structures that are threatened.
LiDAR (light
detection and ranging) and other technologies are being
used extensively to create baseline maps for just these
reasons. (See "Shoreline Mapping Along the Great
Lakes" in the March/April 2003 issue, www.forester.net/ecm_0303_shoreline.html.)
NOAA, using
a new aircraft-mounted digital sensor system camera
that it acquired just weeks before Isabel, can carry
out long-term mapping projects and was also able to
document within hours a new inlet that the hurricane
created near Cape Hatteras. Remote-sensing technologies
such as synthetic aperture radar, which can obtain shoreline
imagery even through dense clouds, and Airborne Visible
and Infrared Imaging System hyperspectral imaging are
also being used for mapping shorelines and tracking
coastal changes.
For EC practitioners,
this ability to have more data sooner - whether it helps
predict sudden damage or slow change - is a significant
planning tool and a boost to credibility as well, as
it can visually demonstrate to planners the prudence
of investing in erosion control measures - or in relocation
of assets, as the case might be. Incidentally, NOAA
actually addresses the feasibility of each of the hurricane-dissipating
suggestions on its Web site (www.aoml.noaa.gov),
including the results of Project Stormfury, the cloud-seeding
effort, in the 1960s and '70s.
Send
Janice an Email
EC
- November/December 2003
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