Could storm surge barriers have thwarted Sandy’s impact?

>>> correspondent, richard engel , is used to flying over terrible scenes by helicopter. he did so again today, only in this country, in this city, where he saw some terrible things down below and saw clearly some of the challenges before us from the air where richard says you can clearly see a merging of weather and national security .

>> reporter: four days after hurricane sandy left people feeling like a bomb had dropped on them, we took the the skies with this detective on an nypd helicopter to survey the damage.

>> the force of this water, that's why they tell people to evacuate. there's no playing with the ocean. but just to see it after is pure amazement.

>> reporter: from about 1,000 feet, we could see how this storm pummeled the empire state .

>> the boardwalk is completely torn up here.

>> reporter: boardwalks in splinters.

>> we lost 100 houses in breezy.

>> reporter: burned black patches where homes used to be. entire harbors tossed. an oil tanker, breached and leaking. crews have begun to pump out lower manhattan . but some areas are profoundly waterlogged, like the subways. we went underground to see.

>> there's still under water there now.

>> we have water all the way up to the mezzanine.

>> reporter: joe is in charge of getting mass transit drained and running.

>> reporter: anything that can be done to prevent this from happening again?

>> we looked at this storm right from the beginning as a category 1 . so we began covering all the vents in the area with plywood. we boarded up all the station entrances that we could. in the future, if you're going to prevent storms like this, category 1 , category 2 , with storm surges like this, you would have to actually raise the bulkhead and create more of a seawall to prevent the water from coming in.

>> hurricane sandy is a wake-up call to all of us in the city and on long island.

>> reporter: this oceanographer has been arguing for years that the new york metropolitan area needs a better plan.

>> that means designing and building storm surge barriers like many cities in europe already have.

>> reporter: in the netherlands, following a major storm in 1953 which drowned thousands, the government built an extensive series of storm surge barriers.

>> if we had such barriers in place during hurricane sandy, there would have been no damage at all.

>> reporter: this animation, produced by the dutch company, shows what a barrier in new york harbor right look like. if a surge was coming, 25-foot-high gates would drop and then swing shut to block the water until the danger had passed.

>> the surge is completely blocked by the system.

>> reporter: but bowman's idea would require years of study and cost as much as $15 billion, a huge amount. but still, just about a third of the estimated cost of rebuilding after sandy.

>> we can't put all our eggs in that basket.

>> reporter: cynthia, who heads the climate impacts group at columbia university , cautions that barriers are not the only answer.

>> the better way is for new yorkers to be smart, from engineered solutions like tidal barriers, fixing the subways where they're vulnerable, fixing our seawall, remaking our wetlands so that we can across our whole region and for all our 21.5 million people protect against the next hurricane sandy.

>> reporter: and with scientists now predicting that the sea level could rise between three and six feet by the end of the century , even moderate storms could be catastrophic.

>> we have to expect this to be the new norm. we have to take bold new approaches if we want to have cities to survive.

>> this has everything. it's got politics, environment, national security . in endorsing obama today, mayor bloomberg mentioned climate change . and as i said to the governor, it's already new amsterdam. could the city be the new new amsterdam?

>> i think it's important to start thinking about infrastructure as essential national security . for the last ten years plus, the united states has had a main national security priority, the thing we've spent the most money on, a trillion-plus dollars, that's been bringing democracy to iraq and afghanistan, with very questionable results. people i've spoken to, experts in the field say, we would be a lot safer, not just richer, if he had spent a lot of that money on improving infrastructure. that is not to say that counterterrorism isn't important. it certainly is. but they're related because the stronger your society is, the more protected you are also from a terrorist attack.

>> may have to keep you around to cover this for a while. richard engel , thanks.