Tag Archives: Sea Level Rise

North Carolina’s valuable pile of sand

This land isn’t permanent, it moves. This whole pile of sand moves with every storm with sea level rise, and it’ll continue to move for hundreds of years. And we’ve tried to engineer it like it’s Raleigh, like it’s a rock, but it’s not. It’s sand.” — Stanley Riggs, former professor of marine and coastal geography. — Courier-Tribune, Sept. 15, 2018

The pile of sand Riggs is talking about is the Outer Banks, the 200 mile string of barrier islands off the coast of North Carolina. His concern is the continuing development on that long sand bank, and the general lack of interest in restricting it.

Map of North Carolina’s Outer Banks

Map of North Carolina’s Outer Banks. Image from U.S. National Parks Maps

Given that the Outer Banks consist of shifting sands, sit barely above sea level, and are located in a part of the world subject to violent ocean storms, why is there continuing development?

The developers know that building houses and roads on sand is asking for trouble. The difficulties associated with the stability of buildings have been researched for well over 2000 years. Matthew, a great authority on the subject, said: ”And everyone who hears these words of mine and does not do them will be like a foolish man who built his house on the sand. And the rain fell, and the floods came, and the winds blew and beat against that house, and it fell, and Great was the fall of it.“ — The guy knew what he was talking about.

Image of fallen house on Hatteras Island, North Carolina

fallen house, Hatteras Island, Outer Banks, North Carolina. Image: Steve Early/ Virginia Post

North Carolina’s Coastal Resources Commission studied the situation in 2010 and wrote a report predicting a 39 inch rise in sea level by the year 2100, enough to flood coastal towns and wash away the existing built environment on the Outer Banks. Advocates for economic development in twenty of the State’s coastal counties formed the NC-20 group to lobby against the report which, they said, was based on bad science. It would, they argued, scare away business and tourists. The Legislature agreed, passed a bill prohibiting scary predictions, and ordered the commission to write something acceptable to the economic development people. The result was a 2015 report predicting a sea level rise of 6 – 8 inches by the year 2045. What a relief.

As well as the thousands of year-round residents and summer-cottage owners, the Outer Banks attract several million tourists each year. It’s a big enterprise and an important tax generator. Of course government wants to support it, and they’ll continue to do so until the environmental situation becomes untenable. In the mean time, the real estate developers, estate, agents, house builders, private insurers, road contractors, shop owners, and rental accommodation suppliers, will all get paid. And the tourists will continue to enjoy fun in the sun.

What about the property owners? Well, in real estate, timing is everything. They’ll just have to watch the market and judge when to sell — that’s if they even care; purchasing beach-front property is not a poor man’s game. And if a hurricane happens to blow their stuff away, there’s always FEMA and the Feds (the American taxpayer) to help them rebuild their houses, on taller stilts if necessary.

Beach houses on Hatteras Island, August 2011 after Hurricane Irene

Beach houses on Hatteras Island, August 2011 after Hurricane Irene. Image: Telegraph/AP

If sea level rises faster and higher than the 6 – 8 inches currently mandated by North Carolina’s law makers, who will bare the cost? Probably the people living in towns along the State’s low lying mainland coast. The houses they live in are not summer homes or holiday rentals — it’s all they’ve got.

Map of North Carolina showing physical regions

North Carolina Physical Regions. Map image from NCPedia

 

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.”

Sea Level Rise and how you can track it in real time

Washington DC

On checking the weather, we see a day-old Coastal Flood Warning issued for the District of Columbia which says: “more than a third of Roosevelt Island will be covered by water and back water flooding of Rock Creek in Georgetown will begin.” An unusual occurrence? Not any more. Most low-lying coastal cities, including Washington DC, have begun to experience a new phenomena: High Tide Flooding during quiet weather days, the result of a gradual increase in sea level over the past one hundred and forty year.

Climate experts say that the the rate of sea level rise is speeding up and that the long-term effects could be dire. It’s a challenging subject and we’ve decided to find out more about it, starting today. Our first stop is Washington DC’s tide-gauge station on Pier 5 near the south end of Water Street, one of the many tide-gauge stations operated by NOAA, the National Oceanic and Atmospheric Administration.

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Washington DC showing location of NOAA Tide Gauge Station

It’s a cloudy, not-too-hot September day. From Independence Avenue we walk ten blocks south on 4th Street to where it ends at P Street, then west by a short footpath to the Washington Channel shoreline. The Titanic Memorial (a large granite statue of a man with arms outstretched as if in flight) stands at that point. Pier 5 lies a few hundred yards to the north. We approach it by the waterfront footpath. We can see the tide gauge from the shore but cannot inspect it closely. The DC Police Harbor Patrol have their headquarters on the pier and they refuse to allow unauthorized access. No matter; we’ll look into how tide gauges work later.

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Image from NOAA website

Knowledge about sea level is based on information generated by a global network of about 2000 tide-level stations. A British organization called the Permanent Service for Mean Sea Level (PSMSL) is responsible for the collection and publication of the data produced by the network.

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From: PSMSL website (psmsl.org > data coverage)

There are two trends that give climateologists nightmares: global warming and sea level rise, the second the result of the first. The trend line for the rise in sea level is based on the data generated by the global tide gauge network since 1880. Here’s an example, one of many available on the web.

From: EPA website published 2016

The graph shows that since 1880, sea level has risen by about 9 inches, an average of about 1/16th of an inch per year. However, since 1993, the rate of rise has speeded up to about 1/8th of an inch per year, twice the rate of the long term average. What do the experts say will happen next? Many suggest 1.5 to 3 feet higher by the year 2100. Others, pointing to increasing global warming and the potential for rapid melting of the polar ice sheets, talk about six feet and up by the year 2100, enough to put southern Florida under water and swamp most of the world’s major cities.

Predictions that imply 2100 is the year the rubber hits the road, are not useful. Why? Two reasons: (1) predictions that are safe from being proved wrong within the lifetime of the predictors, are not impressive and easily ignored; (2) the year 2100 is eighty years in the future, much too long a time frame to be of practical use to most people. We need predictions that focus on the near term. We also need a way to keep track of the situation in real time and without having to depend directly on experts for information on which to base personal decisions, such as where to live, for example.

Help is at hand in the form of a paper titled ‘Sea level rise drives increased tidal flooding frequency . . . ‘ published Feb. 3, 2017 in the ‘open access’ journal PLOS ONE. Here’s an excerpt:

“. . . because the general public often perceives climate change as a temporally distant threat, we have chosen to focus on two time frames (15 and 30 years into the future) that are easily comprehensible within a human lifetime.”

In the paper, the authors have predicted the severity of tidal flooding at 52 locations along the U.S. east and gulf coasts by the years 2030 and 2045. They did this by first establishing a correlation between tide-gauge measurements and Coastal Flood Advisories (CFAs) issued by the U.S. National Weather Service. They then show that the number and frequency of CFAs for any  given location can substitute for tide-gauge measurnts as a predictor of future flooding severity.

This is great. We, or anyone else with access to the web, can easily keep track of the number and frequency of CFAs affecting coastal property. A daily check on the Coastal Flood Advisory section of the National Weather Service takes little effort. After two or three years we can crunch our numbers and decide for ourselves whether or not sea level rise is a threat to take seriously. We won’t have to depend on media reports about climate change to be in the know.

Here’s an example from the PLOS ONE paper. By 2015, the number of tidal flood events affecting the shore area of Annapolis, Maryland, had risen to about 35 per year. Based on the CFA record for Annapolis, the authors predict that that number will rise to 145 by the year 2030 (only 11 years from now) and to 180 by the year 2045. If those predictions become fact, who is going to put up with streets and shop fronts that get swamped by sea water every second or third day of the year? The report paints a similar near-term future for the waterfront areas of Washington DC and other cities.

Since we intend to keep track of the Coastal Flood Advisories issued for Annapolis, we decide to visit the city to see for ourselves how tidal flooding has affected it so far. Annapolis lies about 30 miles from DC on a different branch of Chesapeake Bay. We retrieve our car from its parking spot and head east out of Washington, aiming to connect with Route 50.

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Annapolis MD showing the tourist area affected by intermittent tidal flooding

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Washington DC and Annapolis, Maryland in relation to Chesapeake Bay