It will take tens of
billions of dollars to repair the damage of Superstorm Sandy. Will this be the
norm of the future as climate changes and the sea level rises? If it is the new
norm then repairs though necessary are not enough and a change in planning is
necessary.
Coastal storms will more likely cause flooding. How do you then spend limited funds to both repair New York and its environs and to improve coastal defenses against flooding? This is not just physical barriers but how people live in the area they want to live in.
Coastal storms will more likely cause flooding. How do you then spend limited funds to both repair New York and its environs and to improve coastal defenses against flooding? This is not just physical barriers but how people live in the area they want to live in.
"Storms today are different," says Jane Lubchenco, who heads the National Oceanic and Atmospheric Administration, which includes the National Weather Service. "Because of sea level rise, the storm surge was much more intense, much higher than it would have been in a non-climate changed world."
Some of the problems are
where we like to live and build. It is nice and convenient to build near
the beach but is that a good place to be?
Some things are a given.
You can see this as you drive through Staten Island's shore neighborhoods. Many
of these houses are painfully near the sea and just above sea level. Sandy
knocked homes off their foundations and flooded the rest. This is not the
only place of course. In New Jersey Long Beach Island was completely
devastated. This was extensive construction on a barrier
island.
Barrier Islands, a
coastal land form and a type of barrier system, are relatively narrow strips of
sand that are parallel to the mainland coast. They usually occur in chains,
consisting of anything from a few islands to more than a dozen. Excepting the
tidal inlets that separate the islands, a barrier chain may extend
uninterrupted for over a hundred miles. These are the first to be hit in
a major storm and the mostly likely to be damaged.
The net result after
Sandy was that many of these homes became uninhabitable and condemned. Marit
Larson, with the city's parks and recreation department, says most of the OK
ones were built after the late 1990s, when building codes changed.
In between many houses
you can see wetlands — tall reeds and twisted trees in standing water. Larson
says normally they slow runoff from rainstorms. But Sandy's 10-foot-high surge
overwhelmed them. It also shows where people built and questions
why they were built in or near wetlands.
"Just simply the
amount of water that came in and inundated these people's property — that
couldn't be held back by these wetlands," Larson says. She says wetlands
could be useful for future storms, however, if you put them in the right place
and make them big enough. So future planning should have this in mind as
well as wide beaches and barrier islands. Sand dunes and sea walls are
another option to help control flooding.
Engineer Franco Montalto
of Drexel University says beaches could be improved by building up with sand or
sediment to create dunes that hold back the water.
"And the evidence
seems to be that places that had rehabilitated beaches suffered less damage
than places that didn't," Montalto says.
"You know, a beach
nourishment project could have value in terms of protecting houses, it could
add habitat and could sort of enhance the value of this beach," Montalto
says.
New York is seeking
about $10 billion to prepare for the next big storm. Some experts, like
Montalto, say you get more bang for your buck with a "distributed"
defense — dunes, wetlands, bigger stormwater culverts, even urban parks in the
right area that slow down the flow of water.
It is all about planning
and then executing.
New York city officials
are contemplating plans to build huge sea walls — across the mouths of the
Hudson and East rivers, for example, and even one from New Jersey to New York.
Each would cost $6 billion or more. Of course a sea wall is fine for one
place but may complicate matters for another place.
Klaus Jacob, a
geoscientist at Columbia University's Lamont-Doherty laboratory in New York,
says: "The only thing that barriers do is prevent storm
surges," he says. "Now that's wonderful. It would have taken care of
Sandy and will take care of future storm surges up to a point."
That point being when
sea levels rise enough to push a storm surge over the top of the sea wall.
Since no one knows how high levels will go, a sea wall could become obsolete in
a few decades.
Moreover, a sea wall is
open most of the time to let traffic through. So as the ocean rises, it will
raise the river level, too.
A more proper response
may be to abandon some area prone to flooding and use them as natural barriers
rather than putting up a large wall.
In conclusion, a cost
benefit approach is an effective way to determine whether a seawall is
appropriate and if the benefits are worth the expense. Besides controlling
erosion, consideration must be given to the effects of hardening a shoreline
upon natural coastal ecosystems and human property or activities. Overall, a
holistic approach to planning is ideal. It is important to remember that a
seawall is a static feature, it will conflict with the dynamic nature of the
coast and impede the exchange of sediment between land and sea.
For further information
see Planning.
