http://science.time.com/2012/11/02/manhattan-goes-dutch-building-levees-in-gotham/

In his discussion of the plan to build levees to protect New York City, Jeffery Kluger discussed the possible structural and economic impact posed by another storm such as Hurricane Sandy.  In his article, he focused on Manhattan, discussing how the geology of the island is primarily granite.  Due to this, if storm surge can be managed, he states that much of the damage can be mitigated, as citizens would not need to worry about the water weathering the island.  This is mostly true, as the quartz and any garnets in the granite are resistant to weathering, but the mica and feldspar would be much more susceptible to the warmer, and greater quantities of, sea water.  Depending on the composition of the granite, this could prove to be a virtual non-factor in adjusting for possible weathering or could prove to be another obstacle that must be managed.  Regardless of the composition, Kluger was correct in his assertion that levees would be necessary, but also in saying that pumps would be necessary to prevent water from pooling up, as this would increase the possibility for the mica and feldspar in the granite to dissolve.  This would be limited by  the lack of movement of the water, but it could still cause significant problems.  This weathering could also prove problematic if a major storm were to occur during the late fall, as did Hurricane Sandy, or early winter, allowing water to enter the cracks and potentially freeze, leading to more damage over a long period of time.

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