NYC Floodgates: Pros And Cons

[desertpunk]

Bloomberg

Billions on Flood Barriers Now Might Save New York City

By Ken Wells and Mark Drajem - Nov 9, 2012 2:11 AM MT

Could a surge-protection barrier have saved New York City from much of the flood ravages of superstorm Sandy?

Malcolm Bowman and other hydrologists are convinced it could have.

Bowman, an oceanographer who has spent much of a 40-year career warily watching the tidal flows in and around New York Harbor, recalls a few years back being down in the construction site of Manhattan’s South Ferry subway station.

“It was just a concrete box underground then,” he said in an interview. Bowman, at the time an observer in the middle of filming a documentary, looked up a long stairway leading to blue sky and asked a construction official, “Would you mind telling us how far above sea level is the entrance there at street level?”

The reply was 11 feet -- an elevation designed, the official said, to withstand possible floods from a storm that occurs once in 100 years.

“I said, ‘That sounds awfully low to me and, by the way, that storm could come next week,’” said Bowman, a professor at the Marine Sciences Research Center of State University of New York at Stony Brook, Long Island.

It took a little longer than that. The South Ferry station, a $530 million jewel in New York City’s subway system at the tip of Manhattan, opened in March 2009. Superstorm Sandy, slamming into the New York metropolitan area on the evening of Oct. 29, brought a record storm surge of 13.88 feet (4.2 meters) into Battery Park, which abuts South Ferry. The station flooded floor to ceiling with briny seawater, destroying equipment and turning escalator wells and tunnels into caverns deep enough to scuba dive in.

[...]

A 2009 engineering study undertaken by Mahwah, New Jersey- based HydroQual Inc. estimated that a barrier system involving massive floodgates at key points such as the East River and the Verrazano Narrows would reduce the flooded area of the New York metropolitan region by 25 percent, the population affected by 20 percent, submerged property 35 percent, and cut storm damage to sewage plants and other hazardous waste facilities by half. Conceptual designs of several such systems were floated at a 2009 conference at the Polytechnic Institute of New York University.

High Cost

While such a system is expensive to build -- estimates range to $17 billion -- Sandy’s damage and economic losses to the region may reach $50 billion, $33 billion of that in New York state alone, Governor Andrew Cuomo said yesterday at a news briefing. And that’s not out of line with the $15 billion the federal government spent to rebuild New Orleans levees after Hurricane Katrina in 2005.

“Think about it this way,” said Bowman. “Including Hurricane Irene last year, we’ve had two 100-year storms in two years.”

[...]

[Hudson11]

it would be worth it for Manhattan but i'm sure residents of the other boroughs (or the rest of the state) wouldn't be happy paying the $$$
Companies leasing buildings in lower Manhattan might fork up some, but not billions.

[desertpunk]

Their estimates are way too low. The final cost of a comprehensive floodgate system, including LI Sound, would likely exceed $100 billion.

This is New York, not Louisiana.

[I-275westcoastfl]

Originally Posted by desertpunk

Their estimates are way too low. The final cost of a comprehensive floodgate system, including LI Sound, would likely exceed $100 billion.

This is New York, not Louisiana.

Exactly! LOL.. You're talking about a place that will spend a few billion replacing one bridge that they still haven't replaced..

[600West218]

The New York Times had a good article about how floodgates and other artificial systems can be a bad idea even ignoring the cost.

The reason is that by building floodgates you are leaving people in places that are more and more exposed and only able to survive as long as the flood gates work properly and stop all the storm surges. But should the ever fail, then you have a disaster. New Orleans would be a case in point. When the system failed it was a copmlete disaster. This is called a "binary" system. It works until it doesn't - and then you have a disaster.

What this means is that once you go down the road of using storm gates you will constantly need to rebuild them and make them bigger and stronger as they can never be allowed to fail. That, of course, is hard to do.

An alternative is to simply abondon areas that are too exposed to storms. The Rockaways, and parts of Staten Island and Coney Island should be pulled back from with that land that is at high risk used for things like parks - not residences.

Even parts of lower Manhattan should probably not have further building in anticipation of an eventual pull back.

[desertpunk]

One remedy is to indeed downzone areas like Far Rockaway and remove the public housing which concentrated large numbers of vulnerable people in a flood zone. Let wealthy individuals who can afford losses build dwellings along the shore and relocate public housing to areas that can support more people in a bad storm.

Lower Manhattan may need a flood wall and the kinds of pumps they have in New Orleans to clear out flood water. The problem with floodgates is that the cheapest, most effective place to build them, near the VN Bridge, would still leave huge areas undefended. Closing the gap at Sandy Hook would be extraordinarily expensive, take many years to build and might be shot down early for ecological reasons.

[babybackribs2314]

How feasible would it be to instead build a series of extremely large wind turbines and then connect the gaps with smaller sea walls (standing between each turbine)? I'd imagine it would be much more cost-effective and would also produce an ample amount of clean energy.

[Middle-Island]

Originally Posted by 600West218

An alternative is to simply abondon areas that are too exposed to storms. The Rockaways, and parts of Staten Island and Coney Island should be pulled back from with that land that is at high risk used for things like parks - not residences.

From what I've read in the local Newsday, buildings that were up to FEMA code fared very well. They did get flooding, yes, but are structurally sound. There was a lot of old housing stock along the south shore of Long Island, but especially in Staten Island. That's why the majority of deaths in the New York metro happened there (41), quite simply. Some of these bungalows built in the early 20th century in low-lying places such as Lindenhurst (SW Suffolk Co.) as well were taken out by 15 foot waves from the Great South Bay...a good several miles from the ocean, no less.

Lindenhurst (pop. 26,000) is no resort community. It's considered lower middle class and the vast majority of people, at least who've been interviewed, vow to stay and rebuild. These are tight-knit communities with a strong identity with fishing, boating. Same goes for locales such as Amityville, Babylon, out to Sayville. Long Beach, Island Park and the neighborhoods in the Rockaways went through hell with 40 degree homes, sewage in basements, no electric for almost two weeks, but again claim there's no other place they'd call home.

[600West218]

Originally Posted by desertpunk

The problem with floodgates is that the cheapest, most effective place to build them, near the VN Bridge, would still leave huge areas undefended. Closing the gap at Sandy Hook would be extraordinarily expensive, take many years to build and might be shot down early for ecological reasons.

CLosing the gap at Sandy Hook probably wouldn't work anyways. Sandy Hook is just a spit of sand sticking out into the water. It itself keeps moving. I was there last year and they have a light tower located at what used to be the end of it - now the end is half a mile away. I don't know that you can build your defensive line around something that keeps moving.

[desertpunk]

Originally Posted by 600West218

CLosing the gap at Sandy Hook probably wouldn't work anyways. Sandy Hook is just a spit of sand sticking out into the water. It itself keeps moving. I was there last year and they have a light tower located at what used to be the end of it - now the end is half a mile away. I don't know that you can build your defensive line around something that keeps moving.

It's feasible but you'd have to sink pilings down to thye bedrock and fill in with rock to form jetties around the bulwarked flood walls. Floodgates could then be placed in specific shipping lanes that aren't walled in. Very expensive and subject to eyewatering environmental reviews. I'm reminded of those contentious hearings over shadows cast by anything tall built out on piers or near the Hudson River...

[CNB30]

Originally Posted by 600West218

Even parts of lower Manhattan should probably not have further building in anticipation of an eventual pull back.

lets abandon Manhattan great idea!!!!

[Bobdreamz]

Originally Posted by 600West218

The New York Times had a good article about how floodgates and other artificial systems can be a bad idea even ignoring the cost.

The reason is that by building floodgates you are leaving people in places that are more and more exposed and only able to survive as long as the flood gates work properly and stop all the storm surges. But should the ever fail, then you have a disaster. New Orleans would be a case in point. When the system failed it was a copmlete disaster. This is called a "binary" system. It works until it doesn't - and then you have a disaster.

What this means is that once you go down the road of using storm gates you will constantly need to rebuild them and make them bigger and stronger as they can never be allowed to fail. That, of course, is hard to do.

An alternative is to simply abondon areas that are too exposed to storms. The Rockaways, and parts of Staten Island and Coney Island should be pulled back from with that land that is at high risk used for things like parks - not residences.

Even parts of lower Manhattan should probably not have further building in anticipation of an eventual pull back.

Should we abandon Florida & New Orleans too? The cost of building floodgates to protect NYC far outweighs the potential damage from another storm like Sandy.
If we can rebuild Iraq why can"t we do this? Remember the Hoover Dam was built during the Depression also. Let the Feds pay for it!

[redbaron_012]

If you use New Orleans as an example it shows how the town then city just grew beside the River doing it's normal thing, carting tons of soil downstream to a delta in the Gulf. Bit by bit they built levee banks till you have what is their now. Cities anywhere near sea level can build sea walls to cope with random storms or surges but in the end mother nature does what it wants. You can't abandon most coastline cities in the world just because a big damn storm hits now and then. Just if it does do the best you can.......I guess ?