Carolina Environmental Diversity Explorations
The formation and migration of inlets is another important natural process that takes place on the Outer Banks. Inlets perform two primary functions during storms. They allow the storm surge that piles up in the sound to escape, and they also allow the fresh water that runs off of the land to flow out to sea.
Between storms, these inlets reduce to small channels, and may even close. If the channel remains open, the flow through the inlet is controlled by the ebb and flow of the tides. This tidal-dominated flow results in the formation of a series of shoals at both ends of the channel, known as the ebb-tide and flood-tide deltas. The tidal deltas play a vital role in the transport and storage of sediment within the inlet system.
Oregon Inlet formed during a hurricane in 1846 and has migrated more than two miles to its present position. The sites of the two original lighthouses, built in 1814 and 1859, have been claimed by the migration of the inlet, and the Bodie Island Lighthouse, constructed in the 1870s, now stands 3.8 miles from the edge of the inlet it was built to mark.
The spectacular Herbert C. Bonner Bridge spans 2.5 miles over the Oregon Inlet. At the northern end of the bridge, the inlet shoreline has migrated southward, leaving marshy land in an area that was underwater when bridge construction began in 1962.
Figure 15 shows the northern end of the Herbert C. Bonner Bridge. Notice how far the inlet’s shoreline has migrated since the bridge’s construction. The marsh in the foreground has developed on sand deposited in the tidal delta system of the inlet.