Rain and The Great Outer Banks Escarpment

Beach escarpment in Nags Head, looking toward Jennette's Pier.
Beach escarpment in Nags Head, looking toward Jennette’s Pier.

Into every life a little rain must fall, but this has been ridiculous. Since this last system moved in on Saturday evening, rainfall has come in around 10”. That’s a lot.

For the most part the Outer Banks actually handles a heavy rain like that pretty well. The ground is porous—these are giant sandbars—so the water drains quickly into the aquifer. There is often some deep standing water on the roads during the rain; that can’t be helped. We are, after all, at sea level, so there is not very much drainage happening.

Some interesting things did occur this time.

Combination of Natural Forces Create New Beach Feature

One in particular was something we hadn’t seen before. The combination of a king tide—a high tide that lasts longer than usual, heavy seas and extraordinary amounts of rain combined to combined to carve out a 10’ high escarpment in the Nags Head beach just north of Jennette’s Pier.

It’s an interesting physical featue. Extending about 200 yards along the sea, the first half of the escarpment is 10’-11’ high, gradually lowering until it rejoins the beach.

According to an Outer Banks Voice interview with Tim Kana, the President of Coastal Science, scientific term for what has happened is an “erosional arc,” and it is certainly arc shaped. Coastal Science is the firm that designed the Nags Head beach nourishment project. Nags Head will renourish their beach next year.

According to Kana, the dramatic loss of sand was probably caused by a gap in the offshore sandbar that is usually there to dissipate the force of the waves. The combination of high surf and a longer than usual high tide caused the sand to collapse and be taken back out to sea.

It is certainly possible that the sand will form a sand bar. Generally speaking, sand from the beach does not travel very far.

Another escarpment has formed in Kitty Hawk. However, that is caused by town pumps that are draining low lying areas adjacent to the ocean. The outflow has carved away the beach. The effect in Kitty Hawk is expected to be short term.

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