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10/12/2005
Battling the Water
Be careful what you wish for, you may get it. Our part of New
Jersey has been suffering from a drought and we’ve all been
wishing for rain. All the remnants of this year’s hurricanes
passed either to the west or to the east of us and other storms
split when they approached, leaving us high and dry. Tropical
storm Tammy’s remnants did none of those things and dumped
as much as 9 to 12 inches of precip in certain parts of Jersey and
we certainly got our share. As a result, on Saturday night my
wife and were manning a towel brigade in our basement
mopping up the encroaching H2O. Reluctantly following a
suggestion by my wife, I also found myself outside in a
drenching downpour in the dark with a hoe in hand trying to
make a trench to divert water away from a corner where a major
pool of water had formed.
Fortunately, our towels and possibly my hoeing stemmed the tide
of the flooding in the basement and, thanks to Doppler radar and
our local weather channel, we went to sleep assured that the
deluge would be over shortly. The next morning, the Sunday
papers headlined the horrible earthquake in the Pakistan-India
region and the deadly mudslides in Guatemala. These tragedies
and the devastation caused by Katrina and Rita certainly put our
minor problem with Tammy in perspective.
The last time we had water in our basement was several years
ago when we were in Amsterdam and, unbeknownst to us, our
town had 8 inches of rain in one day. We came home to find the
large carpet from our basement rec room in our driveway, carried
up there wet by our artist, Harry Trumbore! I hadn’t planned to
write anything more about hurricanes and the Gulf coast but the
September 16 issue of Science had articles about hurricanes and
possible approaches to reconstruction of New Orleans and its
environs. There was an Amsterdam connection in an article by
John Bohannon and Martin Enserink on the “Dutch Solution” to
keeping out the sea from The Netherlands, half of which
(including Amsterdam) is below sea level and sinking.
The Netherlands had its own version of Katrina back in 1953
when a North Sea storm breached neglected dikes. The flooding
killed 1800 people. The Dutch responded by building a bunch of
dams, storm surge barriers and dikes over a period of more than
four decades in a project known as the Delta Works. The dikes
protecting the most heavily populated regions are claimed to be
able to hold up against all but a once-in-ten thousand-years
storm, according to Bohannon and Enserink. That sounds pretty
good unless you just happen to be there for the “big one”.
How about those big ones? We recently talked about hurricanes
being more intense if they pass over warm waters and the
possible influence of global warming. In another paper, Peter
Webster of the Georgia Institute of Technology and his
colleagues have examined closely examined the worldwide data
on tropical cyclones (call them hurricanes or typhoons, the
effects are the same) over the past 35 years. They’ve broken out
the number of category 4 and 5 hurricanes, lumping them in one
category, lumping the category 2 and 3 storms in a second
category and the category 1 hurricanes as a class by themselves.
Looking at a plot of the number of hurricanes in each category
over the period of 1970 through 2004, the three weaker category
storms show no striking trend. However, the number of category
4 and 5 hurricanes jumped significantly. To illustrate this, the
researchers divided the data into two 15-year periods, 1970 to
1989 and 1990 to 2004. In our North Atlantic basin, the number
of category 4 and 5 hurricanes jumped from 16 in the 1970-1989
period to 25 in the 1990-2004 period. In the Western Pacific
basin, the number jumped from 85 to 116 category 4 and 5
storms. In the Indian Ocean basin, the number more than
doubled, from 24 to 57! By comparison, we in the eastern half of
the United States get off relatively easily.
Bottom line – it’s clear that the number of intense storms is on
the rise worldwide. Webster and his coauthors are careful to
point out that, although the data are consistent with global
warming, there isn’t a long enough history of data on worldwide
numbers and intensities of hurricanes to nail down global
warming as the culprit. Whatever the case, we certainly aren’t
making things better by settling on the coasts, ensuring major
trauma from any strong storm.
Which brings us back to New Orleans and The Netherlands.
Would the Delta Works model work in the Mississippi delta?
Would a storm surge barrier work to seal off Lake Pontchartrain?
New Orleans is different from The Netherlands. It has this huge
river constrained by those levees. The silt that used to build up
the delta and build up those barrier islands now gets dumped into
the Gulf of Mexico. Without all that stuff to build them up and
sustain them, the barrier islands and the wetlands have been
eroding away. Barrier islands are called by that name because
they are indeed barriers that help protect land onshore from
strong storms.
John Day, an ecologist at Louisiana State University in Baton
Rouge, has been leading a study started in 2000 in which they are
diverting part of the Mississippi River into the wetlands. The
level of the land is rising at 1 centimeter a year, less than half an
inch. Day says that’s enough to compensate for rising sea levels.
But there’s another problem. Like Venice, New Orleans is
sinking and probably will have sunk another 3 feet or so by the
end of the century. What to do about that? One approach is to
raise the level of the New Orleans bowl. One method for doing
this has been suggested by Roel Boumans, a fellow who got his
Ph.D. at LSU and is now at the University of Vermont in
Burlington. Boumans says why not pipe in the sediment from
the Mississippi and build up the bottom of the New Orleans bowl
until it’s at sea level?
That’s obviously a pretty ambitious project and he figures it
would take another 50 to 60 years. What to do in the meantime?
Build houses on stilts and/or build them so they float! Turn New
Orleans into a Venice or a semi-Venice. In a sense, that’s what
Amsterdam is. It has canals, streetcars, autos and lots of
bicycles. It appears that we have a controversy over the best use
of the Mississippi sediment - build up the city or build up the
barrier islands. With all the money that will be thrown at solving
the problem of New Orleans, the fights over what should be done
to rebuild New Orleans are already starting and should last for
years to come.
The Netherlands has its own controversies, with some advocating
living only on higher ground or mounds or floating cities,
“embracing the water” as Prof. Henk Saeijs at Erasmus
University in Rotterdam puts it. On the other hand, hydraulics
engineer Han Vrijling at Delft Technical University says that
embracing the water approach is just a “romantic” notion. He is
comfortable living with putting up higher dikes in a sinking
country.
Oh well, it’s good to live here in suburban New Jersey, where a
bit of water in the basement or the threat of another terrorist
attack in nearby New York make for as exciting a life as old
Bortrum cares to experience. It''s still raining!
Allen F. Bortrum
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