Tag Archives: storm surge

Norfolk VA – Retreat, Dig-In, or Both?

The Coastal Plain — the land bordering the Atlantic Coast from Florida to Cape Cod — was once sea bottom. It has low topographic relief and extensive areas of wet land and drowned valleys such as the Chesapeake, the Delaware, and Long Island Sound. From the air the plain looks as flat as a pancake. The part of the plain that extends eastward into the Atlantic, forms the continental shelf. Norfolk, Virginia, is located on the eastern edge of the plain, on land the sea now wants to reclaim as its own.

Water view of Norfolk VA

Norfolk VA viewed from across the Elizabeth River. Wiki Commons image

It’s a pleasantly warm November day in downtown Norfolk. The sun is shining on the Elizabeth River and there’s nothing to suggest to the casual visitor that the city is under threat from an encroaching ocean. But the Inhabitants of the city are well aware of the threat and are constantly reminded of it.

For example, here’s part of a memorandum from the administrators of the Eastern Virginia Medical School to its students, faculty, and staff, concerning campus safety:

[The school] is located in a low lying coastal area; Norfolk’s elevation and its proximity to several rivers make it susceptible to flooding. Nearly every year, and sometimes several times throughout the year during times of heavy rain, hurricanes or nor’easter storms, the EVMS Community is threatened with the potential of precipitation, tidal and/or wind-driven flooding and/or low-land flooding.

The memo goes on to offer safety tips: If advised to evacuate your home, do so immediately; If there is any possibility of a flash flood, move to higher ground; If possible, move essential items to an upper floor; Turn off utilities at the main switches or valves; Do not walk through moving water. As little as 6 inches of moving water can make you fall; Do not drive into flooded areas. If floodwaters rise around your car, abandon the car and move to higher ground if you can do so safely.

The EVMS campus is located a mile or so north-west of Norfolk’s downtown core, in the district called Ghent. But the threat of flooding is not restricted to any one area, it is a constant concern throughout the city. 

Norfolk VA storm surge map

Norfolk VA storm surge map. Virginia Dept. of Emergency Management

What the map tells us is that, under present sea level conditions, the surge from a category three hurricane would put most of the city under several feet of sea water. However, because the level of the sea is continuing to rise, the potential for catastrophic flooding will increase with time.

The grey area on the map at the north end of the city marks the location of Navel Station Norfolk, the nations largest navel base. The base is particularly vulnerable to storm surge. When a serious storm approaches, the fleet wisely heads out to sea.

Navel Base Norfolk from the air

Navel Base Norfolk. Wiki Commons image

So what can be done to protect the city?

The US Corps of Engineers – Norfolk District, has produced a 438-page report titled ‘Coastal Storm Risk Management Feasibility Study’ in which it proposes building — at a cost of $1.57 billion — a series of storm surge barriers and sea walls. The scheme is designed to protect the city from a 50-year storm, assuming a rise in sea level of 1.5 feet. However, since no one knows what level the sea will actually rise to, or how strong future storms will actually be, and considering the high cost of the plan, it’s unlikely the city will move on the recommendations any time soon.

The May 21, 2018 issue of Inside Climate News, quotes George Homewood, Norfolk’s planning director:

“I truly believe that technology will begin to address some of our climate issues and some of our sea level rise issues, . . . There are obviously some issues, but in theory, can we live with water? Can we make it so the water comes, the water goes, and we just keep on keepin’ on?”

In the same issue, the author, Nicholas Kusnetz, writes:

“Norfolk officials say they don’t know how exactly their city will cope in the long term if seas rise quickly. They voice an understandable, but ultimately troubling faith that someone, somehow, will figure out a solution. Homewood acknowledges that, on some level, it won’t be enough.”

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.