Wimble Shoals along Rodanthe isn't just a system of underwater sand dunes/ridges. The sandy bottom sits on ancient hard ground.
"Morphology , Geologic History and Dynamics of Wimble Shoals , Rodanthe , NC
ECU Author/Contributor"
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"In many coastal studies , onshore processes of erosion and accretion have been correlated to the location of nearshore morphological features , such as ridges , shoals , and shore-oblique bars. These nearshore features are commonly used as sediment borrow sources for nearby beach nourishment projects. Wimble Shoals , offshore of Rodanthe , NC , is a major bathymetric feature that consists of five shore-oblique ridges and is adjacent to a perennial erosional hotspot area that has been the subject of a recent beach nourishment project. Although it is often reported that nearshore bathymetric features impact onshore dynamics , little is known about the nature and origin of these features , and in particular their evolution , morphology , and influence on the coast."
"Decadal- and century-scale bathymetric analyses showed that Wimble Shoals is migrating southward and has some control over the areas of accretion and erosion seen in the onshore environment. Wimble Shoals is composed of highstand systems tract and lowstand systems tract sands that overly a gently dipping Pleistocene surface."
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Somewhere online last year I saw a drawing of eastern NC as it looked 20,000 years ago. The sound was dry mainland, and all of the rivers in the eastern part of the state ended up draining into the ocean through the area that is now Ocracoke Inlet. As the last ice age ended 11,000 or 12,000 years ago the ocean level came up creating the sound and inlets came and went. The first European written report, in 1585 iirc, mentioned Ocracoke Inlet as the only inlet at that time.
I've often wondered why Ocracoke and Roanoke Islands don't migrate like the oceanfront Outer Banks - they are actual islands that were part of the main land mass and not just a sand bank. I'd also wondered why Ocracoke Inlet has stayed open and why it runs right next to the island. It's the ancient river channel scoured into the hard ground under all the shifting sand and not just a channel scoured out of soft sand.
And fwiw, ever wonder why there are freshwater aquifers under eastern NC that extends out under the sounds and allows 3 wells to pull water from 600' down in Ocracoke (there's water 10' down, but they use water from the bottom of the aquifer and then process it with reverse osmosis) and in KDH from the Yorktown aquifer? It was formed when the mainland extended far out into what is now the sound and the ocean.
One of these days I'm going to take a week and start looking into all of this. Or maybe I'll just go fishing.
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