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Why Some Areas are “Sinking” Faster than Others

NOAA's Coastal Flood Exposure Mapper

A new article (https://www.popsci.com/sea-levels-rising-unevenly) recently published by Popular Science explains some quirks of sea level rise in a way that is easy for non-scientists to understand. The author, Marlene Cimons, uses a see-saw metaphor to help us to visualize the forces at work as changes in sea level affects the coastline differently in different areas.

The average lay person probably envisions sea level rise as a uniform phenomenon that simply increases the volume of the ocean, causing it to encroach the land masses equally all around the globe. But this is not how it happens in reality, and Ms. Cimon’s article helps us to understand why, as she describes the natural process that is called ‘post-glacial rebound’.

When a large glacier covers a land mass, the extreme weight of the huge ice feature weighs down the land under the glacier, but the ice-free edges are squeezed upwards. We can easily visualize this by thinking of the see-saw: when one side is down, the other side must go up. If we push on a water balloon, for example, the center of the ballon goes down but the edges go up. Over a long period of time the glacial ice has melted, and the weight has been lifted off the land. This results in the formerly weighed-down land springing back up, with the previously uplifted land sinking back down. Of course, none of this happens quickly, so in this sense the see-saw comparison is misleading. Even though the glaciers that once covered much of the northeastern U.S. have disappeared thousands of years ago, the land is today still see-sawing slowly in response to the changes created by the melting.

NOAA’s Coastal Flood Exposure Mapper is an online tool that allows the user to create and share maps of sea level rise and flooding, and view the potential populations impacted.

So in our present day we have land that is slowly rising in some places and slowly sinking in other places. This movement is not perceptible to us, and yet it is happening quickly enough that it can be measured during our lifetime. It is due to this post-glacial rebound that areas such as the Chesapeake Bay region are experiencing faster and more extreme sea level rise than an area that was not affected by glaciers. This region was historically located at the uplifted edges of a glacier during the distant past, and is now sinking, while simultaneously being inundated by sea level rise. These two factors, working together, make these areas of land much more likely to be inundated, because they are physically sinking at the same time that sea level rise is encroaching the entire coastline.

We now know with a high degree of certainty that this sea level rise is caused primarily by two things: the melting ice caps that are adding unfathomable amounts of fresh water into the oceans, and the warming of the oceans themselves, which physically expands the water. These forces, combined with the post-glacial settling of certain geographical areas, all work together to make it appear that some zones are being inundated at a much faster rate. These areas are today serving as canaries in the coal mine, and the alarming loss of land in these zones is perhaps waking up communities that are currently less affected.

With sea level rise speeding up measurably (and observably) even during one human lifetime, the need for flood defense and long-term planning has reached a critical status. Communities and municipalities that fail to learn from what is happening in Norfolk, Virginia will pay dearly in the near future. Zones that were formerly not known to flood will soon be suffering unspeakable flood damage and devastation if prudent measures are not put into place NOW.

Source: FloodBarrierUSA

Rising Sea Levels Threaten U.S. Military Might

U.S. military bases on the nation’s coastline are at increased risk to “catastrophic damage” from flooding due to rising sea levels, according to a recent article by NBCNews and InsideClimate News.

The National Oceanic and Atmospheric Association reports that global sea level is rising, and at an increasing rate. “In 2014, global sea level was 2.6 inches above the 1993 average—the highest annual average in the satellite record (1993-present).”

Rising sea levels expose many coastal communities to increased flooding caused by high tides and storms. According to NOAA, nuisance flooding from high tides and rain events is as much as “900 percent more frequent within U.S. coastal communities than it was just 50 years ago.”

High Risk Military Bases

Many of America’s strategic military bases are vulnerable to flooding, according to another report by the Union of Concerned Scientists. The Kennedy Space Center (Florida), US Naval Academy (Maryland), Washington Navy Yard (DC), and the Naval Air Station Key West (Florida) are among those at greatest risk.

The Norfolk Naval Shipyard in Virginia is in particular peril. The site is one of only four shipyards designed to maintain the U.S. arsenal of nuclear submarines and aircraft carriers, critical to U.S. defense and humanitarian missions. In the last ten years, the shipyard was impacted by nine major floods. Each event caused equipment damage and maintenance delays that affected the entire U.S. naval fleet.

Looming Disaster?

Sea level at Norfolk has risen 1.5 feet in the last 30 years causing an increase in nuisance flooding. After Hurricane Matthew dumped historic rain on the area, the Navy spent $1.2 million to repair one building badly damaged by flooding.

Most experts agree that a looming disaster for the shipyard is not a question of if, but when. Hurricane Florence came close to Norfolk in September 2018, veering south to bring a flooding crisis in Wilmington, N.C.

A recent computer simulation of a Category 4 Hurricane on Norfolk by the Federal Emergency Management Agency predicts a 12-15 foot storm surge that would submerge the entire area. A news release described the potential disaster as “New Orleans without the levee system.”

Protection from Rising Sea Levels

The military has been sitting on this issue for years. In 2010, the Quadrennial Defense Review made it clear that climate change should be a Department of Defense priority. In 2011, a Navy-commissioned National Research Council report warned that 56 Naval facilities worth $100 billion would be threatened if sea level rose three feet.

Since that report was published, little has been done to protect these assets from the threat of rising sea levels. Political resistance to climate change issues has blocked or slowed efforts to fund resiliency projects that would shore up America’s defenses before it is too late.

In Norfolk, the Navy dodged disaster in 2018, but climate change and rising sea levels remain a clear and present danger to U.S. military might.

Tangier Island: Doomed?

Photo by Eli Christman, Creative Commons License

When one hears the name, “Tangier Island”, pleasant thoughts of tropical vistas with swaying palm trees might come to mind. But in reality, Tangier Island is located off the coast of Virginia, and its primary claim to fame is not balmy beauty but the fact that the island has lost almost 70% of its land mass since the year 1850. Today, Tangier Island is a fast-disappearing symbol of climate change and sea level rise.

According to the most recent census, 727 people make their homes on Tangier Island, which has an area of about one square mile. The island is sandy and sits at a very low-elevation; most of the land is just 3-4′ above sea level. The problem for the inhabitants of this island is that sea level is increasing every year, and at the same time, the land itself is sinking due to the residual effects of an ancient glacier. According to most estimates made by environmental scientists, the entire island will be swallowed by the sea over the next 50 years… if the island keeps losing land at the current rate.

Tangier Island is part of a vulnerable group of islands scattered across the Chesapeake Bay. In the past, these islands numbered well over 500, and were important summer residences for Native American people. The islands even today are rich with oyster beds and crab fisheries, and these resources sustained Native American populations for hundreds of years before the Europeans arrived. Huge piles of ancient oyster shells have been found on the islands, including Tangier, as well as thousands of arrow and spear heads. The weapons are evidence that the islands were once much larger than they are today, and that they supported healthy populations of larger game animals.

Once the Europeans arrived at the Chesapeake Bay, things changed quickly. Native American populations were decimated by disease, encroachment, and the technological advantages of the invaders. A population of British seafarers and fishermen drove off the Native Americans, and settled on Tangier Island. Many habitants living there today are descendants of these hardy seamen, and still bear the old surnames and- because of the extreme isolation of the island- even now present the accented English of their forebears.

However, no amount of pluck and perseverance will be able to save the current residents of Tangier Island. Already today, the island is being swallowed by the sea, and the future looks grim even by the most optimistic of estimates. The land that is still above water is becoming marshy and squishy underfoot, and the sea swallows many meters of coastline every year. People who own homes and businesses on Tangier find themselves looking at a future of homelessness and displacement, with no hope of being able to sell off their assets.

While there is is currently a prospective rescue plan for the island, the plan is projected to cost in the range of $30m- a figure that is completely untenable to save an island important only to the 700 people who live there. And Tangier Island is only one of many endangered inhabited islands on the Chesapeake Bay- why save this particular island and not the others? At the same time, the coastal cities that line the Eastern Seaboard are competing for limited funds to install flood barriers, berms, and other flood control devices in order to stave off inundation. Flooding will be an ever-increasing part of life for all who live near the sea. For those who live surrounded by the sea, flooding will soon claim their entire world.

Source: FloodBarrierUSA

Flood Logs Protect Historic Site from Hurricane Florence

In September 2018 at historic Revolution Mill in Greensboro, North Carolina, Hurricane Florence threatened with high wind, rain and storm flooding. The structure weathered the worst of the storm thanks to Flood Log™ flood barriers from Flood Panel LLC.

Revolution Mill

Revolution Mill is a unique building complex that houses more than 100 businesses, meeting and conference facilities, 150 loft apartments, outdoor performance spaces, public art galleries, restaurants, coffee shops, greenway trails and more.

On the National Registry of Historic Places, the building was the first flannel mill in the South and by 1930 was the largest exclusive flannel producer in the world. Manufacturing in North Carolina declined in the mid-1900s and the Mill eventually closed. In 2012, a $100 million redevelopment project transformed the site into its current state.

Revolution Mill sits along North Buffalo Creek, a stream prone to flooding from seasonal rainstorms and hurricanes. Recognizing the vulnerability of this historic space, management purchased Flood Logs from Flood Panel LLC to protect the site from water damage during a flood event.

Hurricane Florence

Hurricane Florence began like many hurricanes in the Atlantic, as a tropical wave off the coast of Africa first identified by meteorologists on August 30, 2018.

By September 7, Florence had strengthened to a Category 4 hurricane with a bullseye on the North Carolina coast. Two weeks after it was first identified, Hurricane Florence made landfall in Wilmington, N.C. on September 14 as a Category 1 hurricane.

Gradually the storm weakened, but began to slow down moving only 2-3 miles per hour. Storm surge plus historic rainfall caused catastrophic flooding along the North Carolina coast. At one point, the entire city of Wilmington was completely cut off by flooded roadways. Some places recorded over 30 inches of rainfall and many rivers overflowed their banks.

Ready for the Storm

Management at Revolution Mill was ready for major flooding due to sudden storms, flash floods and hurricanes. They had 27 sets of Flood Logs to safeguard the structure.

Fortunately, Hurricane Florence gave the building maintenance crew a lot of time to prepare. “We saw it coming and we were watching developments,” said Don Elliott, Maintenance Supervisor, Revolution Mill. “We had a crew on site to put the Flood Logs up as soon as we knew we needed them.”

According to Elliott, they deployed 22 of the 27 sets of Flood Logs to secure the most vulnerable openings. Installation was fast and easy.

Although many businesses in North Carolina sustained major damage from the storm, Revolution Mill was spared. Flood water was an issue at only one of the protected entryways.

The Flood Logs held up to the rising water, which rose to three feet on one side of the building. According to Elliott, “Water rose outside an area of the building under renovation to become retail space. The water would have caused a lot of damage.”

Once the danger had passed, Revolution Mill stored the Flood Logs on custom racks. For now, they sit idle in storage, but ready for the next storm.

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