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Last updated on April 17, 2014 at 1:21 EDT

Ike Underscores Foolishness of Building on Barrier Islands

September 12, 2008

As Hurricane Ike pummels the Texas coast, the only thing
standing in the way is a thin stretch of land called Galveston.

Galveston is a barrier island, a narrow landmass made mostly
of sand that extends along a coastline parallel to the land. These islands, common along the Gulf Coast and East Coast of the United States, are
some of the most fragile and changing landforms on Earth. And they are
particularly vulnerable to storms.

“Barrier islands are exposed to the open ocean, and the
waves and storm surges generated by hurricanes,” said Bob Morton, a
geologist at the U.S. Geological Survey’s Center for Coastal and Watershed
Studies in St. Petersburg, Fla. “As a storm makes landfall they’re the
ones that are going to receive the strongest winds and the highest wave
actions.”

National Hurricane Center officials have warned residents of
Galveston to evacuate
or else face “certain death,” though several thousand are thought to
be staying put.

Wisdom questioned

Barrier islands like Galveston are particularly vulnerable
to storm damage because they are made of sand, as opposed to the hard bedrock
that underlies larger islands and the mainland. They also tend to have very low
elevations, making it easy for water to wash over and submerge the island.

Many have questioned the wisdom of choosing to build on and develop
barrier islands, given their risks.

“Every year there’s reporting on the foolishness of
building on barrier islands, but people are going to do it anyway,” Morton
told LiveScience. “We don’t
learn from the past. If you look at the barrier islands on the Mississippi
coast in particular, after both Hurricane Camille in 1969, and Katrina, what
did they do? They rebuilt. It’s a perfect example of a coastal area that did
get hit as bad as it can get, and they just go back and rebuild.”

Barrier islands tend to be even riskier places to live than
coastal areas, because they bear the brunt of any approaching storm impact.

“If you think about their location, they’re basically lonely
sentinels that serve as barriers for the mainland,” said Clark Alexander,
a marine geologist at Georgia’s Skidaway Institute of Oceanography. “Basically
you’re in a vulnerable spot, because you’re located where you get the first effects
of anything coming in off the ocean.”

Setting up residence in these vulnerable spots is particularly
perilous.

“From a safety standpoint, it’s silly,” Alexander
said. “Because the lifespan of a typical house is something like 60 years.
But if you live on a barrier island, you can’t guarantee you’ll have land under
your house in 60 years. It’s trying to put something permanent in a place that’s
very dynamic.”

As a result of Hurricane Katrina, a number of barrier islands off the
Mississippi coast were completely wiped off the map. Even when storms aren’t enough to
raze islands completely, barriers often suffer severe damage from
storms.

The 1989 Hurricane Hugo wreaked massive havoc on Pawleys Island in South Carolina. Isles
Dernieres off the coast of Louisiana was devastated by Hurricane Andrew in
1992. Often, after these storms, people move back and set themselves up for
disaster again.

St. George Island on
Apalachicola Bay off the
Florida coast “has been washed away five or six or eight times and people just
keep building back their houses,” Alexander said.

For many people
living on barrier islands, there is no amount of structural support that can
ward off the worst.

“It’s important
to note that in the big storms, the category 4 or 5 hurricanes, it really
doesn’t matter how well-constructed your building is,” said Orrin Pilkey,
a professor emeritus of geology at Duke University, of homes on barrier islands. “And
it doesn’t matter whether you have a seawall or not. The chances are pretty
good that if you have beachfront property, it’s history.”

Outlook for Galveston

Though Ike might not completely destroy
Galveston Island, it could inflict
major damage. Already Friday afternoon, the island was being pounded by high waves and flooding. How much depends on how the hurricane develops and what
part of the island the eye of the storm passes over.

The eastern part of Galveston Island (also the more densely
inhabited) has a strong 18-foot sea wall in place to deflect some of the
incoming waves, so it should be more protected than the western half, depending on the extent to which the storm surge overtops the wall.

Galveston was hit hard by Hurricane Alicia in 1983, and was
devastated by the “Great
Storm”
of 1900, when thousands died. After that disaster, a major
effort went into fortifying the island against future storms.

“They went in and literally raised the city, propped up
houses on stilts,” Morton said. “They brought a huge dredge in from
Europe and dredged up material and pumped it into the land to build it up. It
was an amazing engineering feat for the time. No other place has done something
like that.” The city also erected a seawall.

Constantly changing

Other well-known U.S. barrier islands include the Outer Banks of
North Carolina, the islands along the Eastern Shore of Virginia, and even New
York’s Long Island (though Long Island’s northern position makes it less
vulnerable to storms than barriers in the Gulf of Mexico and southern Atlantic
coast).

The ultimate fate of barrier islands varies, with many
gradually retreating landward as eroded sand is pushed back to deposit in the
lagoon behind it, and ultimately joining the coast. But some barrier islands
with high dunes can avoid this fate.

Galveston is not yet migrating toward the coast, but is in
what Morton calls a “narrowing stage,” with sand on both sides of the
island gradually eroding away. Many barrier islands wax and wane, with sand
shifting around and sometimes reducing the land area, but most inhabited
barriers are not at risk of being completely destroyed.

“Barrier islands are constantly changing,” Morton
said. “The barrier islands as a whole are some of the most dynamic
landforms on the surface of the Earth.”

     


      Source: imaginova