Menu Bar

Home           Calendar           Topics          Just Charlestown          About Us

Sunday, December 23, 2012

Challenge for Charlestown, too

From: Andy Soos,

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.

"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.