Dune formation

Figure 3. The steep slope of Run Hill Dune was formed by strong opposing winds. (Photograph by Blair Tormey. More about the photograph)

The migration of dunes in response to the prevailing winds is an important process on the Outer Banks. Nags Head Woods is flanked on three sides by large dune fields. To the north of the woods is the Run Hill dune field.

Run Hill Dune is an unusually large, unconstrained, natural dune. It was one of a series of nine dunes of this magnitude on the northern Outer Banks, but development and the excavation of the dunes for fill have destroyed all but four. The dunes are formed by winds from the two prevailing directions on the Outer Banks, the northeast and southwest. Because the two prevailing winds flow in opposing directions, tremendous volumes of sand build up within the dunes, and the opposing flow contributes to formation of steep slopes on the northeast and southwest sides.

Figure 3 shows the southwest side of Run Hill Dune. Notice the steep slip face of the dune, formed as northeast winds blow over the crest of the dune, lose their energy, and drop sand grains. A similar steep face can be seen on the northeastern side of the dune, shown in Figure 4.

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