Saving Calvert Cliffs
Efforts to control erosion may threaten unique geology
On the beach below his home in Scientists' Cliffs, retired geologist Peter Vogt points to his "blackboard." He removed the moss and ivy from this bare patch of cliff face the day before to prepare for a school group that he's leading to explore the local geology. Erosion-control efforts could slow the retreat of the cliffs but also block access to these unique formations. Credit: Daniel Strain.
THOUSANDS OF YEARS AGO, natural processes began to form Calvert Cliffs, which loom over the Chesapeake Bay as a natural and scientific marvel.
Erosion was the chief engineer that built these cliffs. Over millennia, wind and waves steadily weathered away the Bay's western shore, exposing the towering structures, among the tallest cliffs along the Mid-Atlantic. Those processes continue today, presenting rewards and risks, depending on your point of view.
Scientists are drawn to these rock faces, which extend along some 30 miles of shoreline in Calvert County, Maryland, because that same erosion has helped to expose a panoply of fossils. They include the remains of ancient whales and other sea creatures. Such discoveries have helped researchers better understand the evolution of marine organisms worldwide (see The Chesapeake's Excellent Fossils).
But for those who have chosen to buy homes along the cliffs' top, erosion has been a mixed blessing. Yes, it created the 100-foot walls where residents can look out over the Bay and the ships passing by. But erosion has also caused the edge of these cliffs to recede toward nearby houses, by up to three feet a year in some places. Many homes are now at risk of tumbling down to the beaches below.
Some residents who live near the steep cliffs have worked for decades to slow the steady collapse that threatens their homes. These efforts, however, can have unintended consequences. In this case, humans risk permanently altering the appearance of the cliffs, a local landmark, and may make them useless as a scientific resource. As homeowners living elsewhere beside the Bay have discovered, controlling erosion can be a challenge that has no easy solutions.
Peter Vogt, a geologist, places a high value on Calvert Cliffs as a teaching tool. He lives in Scientists' Cliffs, a rustic community about midway along the chain of outcrops. He thinks of the beach below his home as a classroom. Vogt often guides field trips from local schools to the beach so that students can get a firsthand look at the region's special geology and fossil specimens.
On a windy day, the scientist takes a walk down the sandy strip to show off the local geology. He reaches a bare patch of cliff face, which he calls his blackboard. Like a math teacher standing in front of a chalkboard filled with equations, Vogt points to interesting events in the planet's history that have been recorded in this gray surface. "It's like our local equivalent of the Grand Canyon," says Vogt, who retired years ago from the U.S. Naval Research Laboratory near Chesapeake Beach.
And like that national landmark, these cliffs owe their existence to erosion. Millions of years ago, the sediment contained in the outcrops made up an ancient sea floor. Then, as ages passed, sea levels rose and fell over and over again around the area where the Chesapeake now sits — driven by a series of ice ages and warmer periods that occurred across the globe. As waters curved around what is now known as Maryland's western shore, they slowly carved away at the ancient sediments there. Eventually, the steep cliffs that you see today were formed.
Or as Vogt puts it, spectacular geology and erosion often go hand in hand. "Most of our national monuments are due to erosion," he says.
Erosion can occur along the cliffs for a number of reasons, he explains. Water lapping at the base of the cliffs undermines the outcrops, causing them to collapse. And as ice freezes and thaws on the cliff face, it also weakens the features. This melting causes soft, moisture-rich chunks of sediment to slip off the cliff face and slide down to the beach.
Over long time periods, the cliffs by Vogt's house recede by less than a foot of land per year on average, according to rough estimates reported by the Maryland Department of Natural Resources Coastal Atlas program. Elsewhere, the cliffs can recede much faster. At spots north of Cove Point toward the south end of the county, for instance, Calvert Cliffs are pushed back annually by nearly three feet on average.
That high rate of erosion — much faster than what you would see by rocky cliffs — hinges on the sediment trapped in the cliffs: many portions of the cliff chain are made up of loosely bound sands, silts, and clays. For waves in the Bay, that's like cutting through butter.
Vogt's home sits about 250 yards from the cliffs' edge, so he doesn't have to worry much about that erosion. But many of his neighbors aren't so lucky.
Gary Loew is another homeowner in Scientists' Cliffs who is very familiar with this erosion. Recently retired from an administrative position at the U.S. Army Corps of Engineers, Loew grew up in Scientists' Cliffs in the 1950s and 60s. The community was founded in 1935 and today encompasses nearly 250 homes owned by a mix of retirees, professionals, and seasonal residents.
When Loew was a child, only a narrow strip of front yard separated his parents' house from the cliff face — and a steep drop. Today, there's nothing left of that waterfront cabin.
That is because in 2011, the Calvert County government applied for a grant through the Federal Emergency Management Agency to buy 10 privately owned homes along the cliffs. The houses, located at the edge of the outcrops, were in imminent danger of being lost to erosion. And two of them, including the old Loew house, were part of Scientists' Cliffs. All but one of the 10 homes have since been demolished.
"It was very sad," Loew says. "I mean, it was not only my childhood home. My father built it."
In order to prevent such losses, the Calvert County government adopted regulations in the 1980s to limit development near to the cliffs' edge. But plenty of homes were built before and remain standing today. As of 2011, more than 230 houses sat within 100 feet of the cliffs' edge, according to data kept by the Calvert County government. Roughly one-third of those were within 20 feet.
"If you can see the sea, then the sea can see you," says Kenneth Rasmussen, a geologist at the Northern Virginia Community College who lives a short walk away from Brownie's Beach at the north end of the cliff chain. "And it's going to get you eventually."
Erosion can get you in two ways on Calvert Cliffs, scientists have shown. Naturally eroding cliffs maintain a steep slope as they recede. Cliffs protected by erosion-stabilization efforts — like gabions — ideally, recede more slowly, becoming gentle slopes. Either way, houses that are too close to the edge may come tumbling down. Illustrations, adapted by Sandy Rodgers from figures in Clarke et al. 2004.
Slowing the Inevitable
On his walk, Vogt points out a remedy that may help homeowners to get ahead of the sea — if only for a little while.
By one stretch of beach, the cliff face is covered at its base with a line of mesh cages filled with heavy rocks. The cages are stacked on top of each other, adding up to about three feet high. Called gabions, these contraptions stretch down the cliffs for more than 100 feet. They completely block from view the cliffs' oldest and arguably most interesting layers, Vogt says. "They're destroying my blackboard," he says.
This small stretch of gabions is just the beginning. Over the next several years, residents of Scientists' Cliffs plan to put in around 1,600 feet of gabions up and down the beaches here. In all, the project will cost the community around $40 to $45 per linear foot of gabions installed, estimates Norman Prince, a local homeowner who chairs the Beach and Cliffs Committee for the residents of Scientists' Cliffs.
But for him and many of his neighbors, the gabions will be worth it: these structures — which perform a similar role to rip-rap, or large boulders that have been stacked on top of each other — should protect the cliffs from waves. And, engineers say, that should help to slow erosion.
Such ventures aren't unheard of locally: most of the length of Calvert Cliffs falls inside privately-owned land. A large cliffside development to the south of Scientists' Cliffs, called Chesapeake Ranch Estates, for instance, also recently obtained permits to similarly protect its cliffs.
Vogt, however, contends that efforts like these merely trade one problem for another. Erosion may be a hazard for homeowners, but it's also the key to Calvert Cliffs, he says. When the cliffs are allowed to erode naturally, as they have done for millennia, they recede. And as they recede, they retain the steep, vertical drop that the features are known for. It's a bit like cutting a piece out of a cake.
But when humans slow that erosion from happening, the cliffs don't stay cakelike: the base of the cliffs remains stable, but the top continues to crumble away. Before long, what was once a steep cliff becomes a gently curving hill that is soon covered in moss, ivy, and, eventually, trees.
The consequences of that transformation for scientists like Vogt would be dire: as the cliffs form into hills, the features' geologic strata — his teaching surfaces — would become buried under layers of dirt, making them all but invisible. Without erosion, the supply of fossils that paleontologists also love so much would be effectively cut off, too.
A 2004 report by a research team led by the U.S. Geological Survey concluded that Calvert Cliffs could be transformed this way in 35 to 40 years or even less following the installation of structures like gabions.
That seems to leave the Bay's cliff dwellers with a difficult choice: lose the cliffs or lose your homes. Vogt isn't the only scientist who has argued for saving the cliffs.
"If Calvert Cliffs are unique, which I truly believe they are, why do we want to destroy that uniqueness?" asks Ralph Eshelman, a paleontologist who served as the founding director for the Calvert Marine Museum in Solomons. "Why do we want the shores of the Chesapeake Bay to look like the shores along the rest of the East Coast?"
A long line of gabions (metal cages containing large rocks) was installed in fall 2013 to protect this cliff base in Scientists’ Cliffs. Erosion along the length of the cliffs threatens to overtake several homes, dumping them into the surf. Photographs: left, Daniel Strain; right, David Brownlee.
Living with Erosion
In the end, erosion will eventually swallow some homes on Calvert Cliffs no matter what steps are taken to control it, scientists say. Whether the cliffs collapse from below or erode from the top and form slopes, houses close to the edge will still be undermined. Homeowners, in other words, can't escape the Bay forever.
It's a reality that the residents of Scientists' Cliffs are aware of, says Norman Prince. "We're not doing this with the idea that we are going to preserve in perpetuity the houses that are presently on the cliff face," he says. "We are doing this to slow the process down."
Despite the risk, Gary Loew, who saw his old family home lost to erosion, wanted to spend his retirement there. He and his wife purchased a house about a year ago around 50 feet from the cliff edge. Loew says they did so because they love the community. They've formed tight bonds with their neighbors, and erosion or no, the view is a beauty.
He also thinks that he will have enough time to get the most out of his home before the eroding cliff face draws too close. "It's a calculated risk," he says. "I'm retired. I'm older. I figure we've got 10 or 15 years in this house before we have to downsize, so I think I'm good."