Building floodgates like the ones pictured here to protect Rotterdam from flooding is one possible solution to prevent flooding of lower Manhattan.

New York City Mayor Michael Bloomberg announced in a June 11 address a $20 billion proposal to protect the city's 520 miles of coastline from the next superstorm.

The plan calls for removable floodwalls for lower Manhattan, a 20-ft. levee to protect Staten Island and dunes to protect the Atlantic shoreline. During Superstorm Sandy, lower Manhattan was inundated by a 14-ft. storm tide.

This plan is based on recommendations of scientists on the New York City Panel on Climate Change. Funding and follow-up of subsequent mayors aside a plan of this magnitude, of course, would have to be implemented in bits and pieces over many years.

Mayor Bloomberg deems the plan "urgent work," with Superstorm Sandy giving the plan immediacy to begin implementing concrete actions to prevent subsequent damage from flooding waters.

The climate panel estimates that by mid-century, the local waters will be 2.5 feet higher, and that eight percent of the city's coastline could see flooding just from high tides.