Maryland's Vanishing Cliffs
by Kent Mountford
Winter rains sped the changing face of the Chesapeake shoreline. Painfully, scientist Mountford watched his land in Calvert County disappear.
In the Miocene era, the Western Shore of today's Chesapeake Bay lay at the floor of a shallow coastal sea, with sandy barrier islands forming and eroding much as Assateague and Chincoteague do today in the face of violent nor'easters. Now-extinct species of clams, oysters, scallops and snails lived out countless generations there.
Beneath the soil and sands of Southern Maryland, the muds of those ancient lagoons, compacted for 14 million years, have become dense clays. At the foot of my steep and sometimes eroding cliff on St Leonard Creek, the beach is littered with Miocene fossil shells.
New Year's Day, the tide was so low that the first sprigs of submerged Bay grasses, encouraged by this mildest of winters, were exposed 50 feet out from the cliff to the edge of my oyster bed.
Above us, the cliff has become inordinately steep and somewhat undercut after two decades of erosion, and we looked up at big oaks, their boles hanging 35 feet above us. I have in earlier times walked to the edge of that cliff without fear to watch my sunsets.
Defined by Rainfall
But this winter, more than a foot of rain fell - about unprecedented in our quarter-century at Osborn Cove.
In times like this, the soil, while percolating deeply, still becomes saturated with moisture. The water reaches down to the ancient Miocene clays, which remember their marine origin and begin to hydrate and become muds again. They become slippery. The sand is unstable and fluidized, the clay layer lubricated, and the heavy soil above begins to move laterally.
I went down into Middle Valley during the deluge. The pond into which my orchard drains was receiving a waterfall. The entire floor of the valley was ankle deep in water.
Tide on the creek normally varies about a foot and a half from high to low. On this night, the creek lapped against the toe of my cliff; the dock in Osborn Cove was almost submerged, with a storm-driven tide five and a half feet above its low on New Year's Day.
Engineers call it "catastrophic failure."
It happened during the night. My neighbors think they heard it. I, sleeping much closer by, did not.
Fifty feet along the face of my cliff, weighing in the hundreds of tons, had collapsed into the creek. An immense oak, close to five feet in circumference, lay on her side in the water. A platform of land had fallen atop the submerged beach and now stretched several yards offshore. It was formed from what had been the edge of my field and its adjacent vegetated bank and was complete with vines, grass and smaller trees standing 20 feet high.
Roots from the big oak had torn away six to eight feet back into the cliff, taking another seven to 10 tons of soil.
Open vista now replaced what had been a view through forested buffer and looking west, along the creek.
My more westerly neighbors, who just purchased this land, are saddened by the loss of their biggest trees. I figure this and previous storms over my quarter century here have taken away thousands of square feet of my land, with a conservative market value of $11,157 - land upon which I continue to be assessed by the state, in its wisdom.
Time, Tides and Taxes
So this is El Niño? Compounded by global warming? By inconsiderate boat wakes all summer? By the shoreline hardening our neighbor on the other side has carried out?
One thing's certain: that in fits and starts, over the centuries, this has been going on all 'round the Chesapeake without surcease. Cliffs crumble houses with them marsh erodes, beaches vanish, islands and villages disappear - all crying against the injustice.
The downed trees at Osborn Cove will help inhibit future erosion. Vegetation and more trees will slowly carpet the now-naked cliffs again. The platform of sand and soil atop the beach will inexorably erode and move laterally along the shoreline, driven by waves from sou'westers and nor'westers, to feed the growth of salt marsh farther north and build the marshy spit that protects Quicksand Pond, our little tidal embayment.
In the pond, the submerged bed of Bay grasses and a nursery for juvenile fish and shedding crabs will flourish.
And likely, before I die sometime towards the year 2030, it will all happen again.
-Kent Mountford, who lives in Lusby, is senior scientist with US Environmental Protection Agency's Chesapeake Bay Program. His occasional letters are written for his colleagues, but he has agreed to share them with New Bay Times readers.
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Volume VI Number 11
March 19-25, 1998
New Bay Times
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