Tag Archives: flooding

Climate Change in Florida — Seeing is Believing

Photo of Miami skyline

Miami, Florida. Image: Unsplash.com. Photo by Muzammil Soorma

Back in 2014, Rick Scott, then republican governor of Florida, was asked if he had a plan to deal with Climate Change. Here’s a 24-second YouTube video clip in which Scott gives his answer: No Plan. That was his position for the remainder of his term in office.

The threat posed by sea level rise to the future of Miami is known and it is dire. Yet people continue to purchase ocean front properties as if no such threat exists. The question is, why? Noah Smith, in an opinion piece for Bloomberg News dated May 3, 2018, suggested that “Increased probability of coastal flooding makes waterfront real estate a bit like a junk bond.” It’s an analogy that calls for elaboration.

A junk bond is a high-yield, moderate-risk security. For example, a city in danger of going broke, may raise money by selling ten-year junk bonds that pay a higher rate of interest (the yield) to attract buyers. The risk to the buyer is that the city may go bankrupt before the ten-year maturity date is reached, in which case the bonds become worthless. Waterfront property threatened by ocean flooding can be compared to that city. The property will continue to attract investors so long as it continues to offer a higher than normal quality of life (real or imagined). That’s the yield. The risk to the buyer in the short term — 10 to 20 years — is the unlikely chance that the property insurers (private or government) run out of money to cover damage when flooding does occur. In other words, the short-term risk to the buyer is negligible.

What about the long term threat posed by sea level rise (3 to 6 feet higher by the end of the century)? As far as Miami real estate transactions are concerned, it hasn’t yet become an issue. The immediate attraction of a higher quality of life (seaside living) has so far trumped whatever worries buyers may have about sea level rise. Furthermore, the prevailing political position has been to avoid giving the buyers reasons to to worry. State officials have taken a see-no-evil, speak-no-evil approach to the threat. There are no zoning laws or other disincentives aimed at discouraging further development in the region’s  flood-prone areas. In effect, the politicians are sitting on their hands, apparently waiting for the ocean to force the issue. 

That raises another question: when forced to act by rising waters, what will the city or the state do to protect the people and their way of life? Move them to higher ground? Miami is built on land that lies barely above sea level. The average elevation of Miami-Dade County is about 6 feet. The highest point in the county is about 25 feet. This means that high-tide flooding already affects those parts of the city that sit at little more than a foot and a half above Mean Sea Level (the average level of the sea between high and low tide). And even conservative predictions say that in 15 to 25 years, sea level will be a foot higher than it is today.

There’s a geological feature called the Atlantic Coastal Ridge stretching along the eastern edge of the Florida peninsula. It consists of outcrops of limestone, which In some places provide marginally higher ground. For example, the North Miami communities known as Little Haiti and Liberty City are built on ridge limestone that rises a few feet higher than the surrounding land. Noah Smith, in his opinion piece for Bloomberg News, mentions studies showing that “higher elevation locations have risen in price faster than similar locations at low elevations.” Okay. But it’s a side issue. The population of the Miami metropolitan area is pushing seven million.     The place can’t speculate its way out of the problems that lie ahead. It needs a real plan.

Florida now has a new Governor, Ron DeSantis, another republican. Here’s a YouTube video in which he says, “I see the sea rising, I see the flooding in South Florida, so I think you’d be a fool not to consider that as an issue we need to address.” That’s progress. Let’s see what he actually does about it?

Rhode Island’s Fox Point Hurricane Barrier. Can it handle a big one?

Photo of Huge ocean wave. Image by Ray Collins

Ocean Wave. Photo by Ray Collins

Rhode Island’s Narragansett Bay sits like an open mouth, ready to swallow any hurricane that makes its way up the East Coast. Usually these northward trending hurricanes lose steam when they reach the colder waters off New England. Usually but not always. The Great New England Hurricane of 1938 arrived over Rhode Island with a forward speed of 50 to 60 mph and wind speeds exceeding 120 mph. It carried with it an ocean swell that filled the bay to overflowing.

Map of Narragansett Bay, Rhode Island

Narragansett Bay, Rhode Island. Openstreetmap.org

According to the National Weather Service (NWS-Boston), “The hurricane produced storm tides of 14 to 18 feet across most of the Connecticut coast, with 18 to 25 foot tides from New London east to Cape Cod. The destructive power of the storm surge was felt throughout the coastal community. Narragansett Bay took the worst hit, where a storm surge of 12 to 15 feet destroyed most coastal homes, marinas and yacht clubs. Downtown Providence, Rhode Island was submerged under a storm tide of nearly 20 feet.”

In 1954, Hurricane Carol produced a storm surge of more than 14 feet in Narragansett Bay. Downtown Providence was once again flooded, this time by 8 to 12 feet of water. All levels of government — local, State, and Federal — agreed that something had to be done to protect the low lying city center. The Fox Point Hurricane Barrier, completed in 1966, was the result.

Aerial photo of Downtown Providence and Providence River

Downtown Providence and the Providence River. The Fox Point Hurricane Barrier is hidden behind the I-195 highway bridge. Image: providenceri.gov

All travellers on the I-195 Highway pass within feet of the Barrier as they drive across the eight-lane bridge over the Providence River. But those who want to look at the barrier and appreciate its design, leave the highway on the east side of the river, and make their way back to Bridge Street and its small riverside park (marked in yellow on the satellite view below)

Satellite view of Fox Point Hurricane Barrier

Satellite view of Fox Point Hurricane Barrier and vicinity. Google Maps Image

The barrier is located a couple of hundred yards up stream from Fox Point, and just north of the I-195 Highway Bridge. It consists of a concrete wall built across the Providence River and earthen dikes that extend flood protection about a thousand feet over the land on each side of the river. Built into the river wall are three, 40 foot wide gates, each weighing  53 tons. Under normal weather conditions, the gates remain open so as not to impede the flow of the river. The gates are located at the eastern end of the river wall. They can be seen in the sattelite view above.

Fox Point Hurricane Barrier, Providence, RI

Fox Point Hurricane Barrier’s three flood gates, looking down stream from park on Bridge Street. I-195 Hwy bridge in background. Providence RI. Image: Brown.edu

An essential component of the barrier system is the pumping station consisting of five massive 4500 H.P pumps, each as big as a grain elevator. When the flood gates are closed to keep a storm surge out, the entire flow of the river must be continuously pumped up and over the barrier. Otherwise the river would be held back, overflow its banks, and flood the city. The pumping station is housed in a building at the western end of the river wall (its roof is plainly visible in the satellite view). The five pumps, operating together, can lift 3.1 million gallons per minute and discharge the flow to the downstream side of the barrier.

Fox Point Hurricane Barrier, Providence RI

View of Fox Point Hurricane Barrier from Bridge Street pocket park. Pumping Station at far right. Google Image

The barrier gates have been closed against storms several times since going into service in 1966. During Hurricane Sandy in 2012, the water crested at 9.5 feet. But the barrier has yet to experience a direct hit from a category 4 or 5 hurricane. As coastal flooding increases in the coming years, hurricane barriers of all kinds are going to be in the news.

New flood gates will keep NYC road tunnels dry next time the city’s streets are under water

New York City was struck by hurricane Sandy six years ago. Since then, while the city has updated its flood-risk maps, it hasn’t taken any concrete steps to prevent storm surges from entering the city. That’s not surprising; the city is rimmed by more than 580 miles of coastline, most of it at risk from storm surge.

Map of NYC flood-zones. Image from NYC Mayor’s Office

NYC flood-zones. Image from Mayor’s Office

Instead, city planners have focused on upgrading critical systems, such as: ‘hardening’ electrical systems; relocating backup generators; flood proofing subway openings; designating more emergency shelters for flood victims. Resilience is a word the city planners like to use these days. In other words, let the seas rise, we’ll deal with the water when it comes.

the most impressive example of this approach so far has been a $64 million project (now complete) to install flood gates on two of the city’s four road tunnels, namely: the 9,117 ft. Hugh L. Carey (Brooklyn-Battery) tunnel under the East River, and the 6,414 ft. Queens-Midtown tunnel, also under the East River. Both suffered serious damage during the Sandy flooding, the Hugh L. Carey tunnel, especially  so. The portals of both tunnels are located within zone-1 (first zone to flood).

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Map showing location of tunnel flood gates

Eight steel flood gates have been installed, two at each tunnel end. The gates were manufactured by Walz & Krenzer, Inc., of Oxford CT. (“Watertight Closures for the Marine industry since 1939”), one of about 50 U.S. companies involved in the flood-control equipment business.

Each gate weighs 44,600 pounds (about 20 tons), and measures 29 ft. wide by 14 ft. high by 22 inches thick.

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MTA Photo

The gate swings on two massive hinges. When parked in its open position, the free end rests on jacks.  Assuming  a two man crew, a machine such as a forklift is needed to help close it. In the event of a storm, the crew will first remove steel cover-plates from  a trough that stretches across the mouth of the portal. Once the gate is closed, the crew will latch it to the face of the portal and to attachments within the trough. Compression seals around the gate’s inner edge will make it watertight.

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MTA photo

The only way to see these gates up close is to drive through the tunnels. You’ll get only a second or two of observation. Considering New York’s frantic traffic, stopping to gaze at the thing is something no prudent driver should attempt.

It’s just as difficult to get a good look at the gates while on foot. Barriers of one sort or another along the streets surrounding tunnel entrances inhibit pedestrians from peering over walls. The Morris Street footbridge will eventually provide a platform from which to observe the Hugh L. Carey flood gates at the tunnel’s Manhattan end, but that bridge is being renovated and will not be available for use this year.