By day’s end, we’d motor-sailed Spartina 74 miles along the intracoastal waterway (ICW) from Blackwater Creek in Virginia to the lower Alligator River. Under a twilight December sky, I set the anchor in 10 ft. of water just south of Tuckahoe Point. Here we slept soundly all night.
At first light the next morning, we got underway down the 27-mile-long Alligator-Pungo canal. At 6 knots, we’d exit into the Pungo River 4 hours later. With luck and a little wind, we’d swing at anchor south of Oriental in Adams Creek by sunset.
As the name implies, the Alligator-Pungo Canal, one of the oldest stretches of the intracoastal waterway, connects the lower Alligator River to the upper Pungo River. The canal’s completion in 1935 created a convenient inland water route to bypass Cape Hatteras (aka: the graveyard of the Atlantic). The canal bisects the Albemarle-Pamlico (A-P) Peninsula through a swampy, sparsely populated region where black bears may out number humans.
Propeller-eating tree stumps lined both sides of the canal. We navigated dead down the middle, only altering our course to work around a few floating logs and one stray vessel. About a mile into the canal, I started noticing the dead trees along the southeastern bank. “Salt water intrusion?… Sea level rise?”, the earth scientist in me thought out loud. Turns out that some of both stressed these trees.
Sea level change is described as either relative or eustatic. Eustatic sea level change refers to global sea level change referenced to a fixed point. Relative sea level change refers to change in sea level relative to the adjacent land mass. Most land masses move vertically, either up or down. Much of the movement occurs due to a process called isostasy.
Similar to bread dough, the earth’s mantle is somewhat squishy. Depressing one part causes a bulge somewhere else (think conservation of mass). When the last ice age peaked 20 thousand years ago, a 3-kilometer thick ice sheet depressed the earth below Canada and upper mid-west. This caused lower latitudes, such as the Chesapeake and parts of the Carolinas to bulge upward in response. Once the ice sheets melted, the peripheral bulges deflated as depressed areas north began to rebound upward. These isostatic adjustments continue today. Geographic locations north, such as Hudson Bay, rebound to gain elevation, while places south deflate to lose elevation. As a result, relative sea level rise is higher along much of the Southeastern coast than is found in the Canadian Maritimes.
Because of isostatic adjustments, the A-P peninsula is slowly sinking, thus increasing the rate of local sea level rise. Much of the A-P peninsula is made up of a peat-like earth known as pocosin soil. An Eastern Algonquian word, pocosin means swamp-on-a-hill. Starting in the 1880’s, farmers dug miles of canals and ditches to drain this mucky, nutrient deficient pocasin soil. Now generations later, these ditches and canals act to conduit salt water from rising sea level into formerly freshwater environments.
After exiting the canal, we turned south along the ICW just outside of Belhaven, NC. About then, a strong northeastern wind picked up and pushed us across the Pamlico River and into Goose Creek. A light rain followed us under the Hobucken Bridge. Once we cleared the Bay River at Maw Point, a 25-knot northeast wind roller coastered us down the Neuse River at 8 knots under jib alone. We made Adam’s Creek just as the December sun set. Spartina’s anchor dug into the mud and held tight through the night’s bluster.