The floodgates in the pictures above provide a simple, yet effective means to prevent extensive damage from floodwaters. In October 2012, when Super Storm Sandy ravaged New York City, many subway stations there were forced to shut down, stranding many New Yorkers. As NYC looks for means to combat the increasing threat of rising sea levels and increased incidents of extensive flooding, these floodgates offer one solution.
But I believe there is a better solution. The downside to floodgates, from my standpoint, is that they would require constant maintenance and human intervention to be properly implemented during a flood. What else could the city do to offer protection? Build cement steps at the entry of the subway, rising up several steps, before leading to the down staircase. A full time cement barrier. They would not be susceptible to mechanical failure or require any personnel to implement them during a flooding event. Yes, they would be expensive to build, but far less expensive than the seawater swirling around in the subway tunnels caused.
The pictures above are very compelling.