Satellite Images Reveal How a New Island Was Born Off North Carolina

Satellite images reveal a new barrier island forming off the coast of Cape Hatteras National Seashore in North Carolina.
Credit: NASA Earth Observatory

How is a barrier island born? A new series of satellite images tells the tale.

Shots taken by an instrument aboard the Landsat 8 satellite between November 2016 and July 2017 show the formation of "Shelly Island," a mile-long (1.6 kilometers) spit off the coast of Cape Hatteras National Seashore in North Carolina. The island formed rapidly, adding most of its mass between April and May 2017. (The Landsat satellites are run jointly by NASA and the U.S. Geological Survey.)

New islands are quite common on this stretch of shore, where waves and tides sculpt sand into shapes that sometimes protrude above the ocean surface. The shallow undersea expanses of sand associated with the capes are called shoals, and it is from these shoals that new barrier islands form, experts say. [See Images of a Volcanic Island Birthed in Japan]

"A likely process would be a high tide or storm-driven water elevation that piled up sediment to near the surface, and then water levels went down, exposing the shoal," Andrew Ashton, a geomorphologist at Woods Hole Oceanographic Institution in Massachusetts, told NASA' Earth Observatory, which released the new satellite images.


Satellite images revealed the island formed some time between November 2016 (left) and July 2017 (right).

Satellite images revealed the island formed some time between November 2016 (left) and July 2017 (right).
Credit: NASA Earth Observatory

"Waves then continue to build the feature while also moving it about," Ashton said.

According to The Virginian-Pilot, the island got its moniker from a visiting 11-year-old, who explored the spot on Memorial Day weekend. (It was loaded with seashells.) But by June, officials were warning people not to try to get to the island, after a series of attempted visits necessitated rescues. A strong rip current makes the 50-yard (45 meters) crossing from the cape to the island dangerous, the newspaper reported

The first snapshot taken by the Operational Land Imager (aboard Landsat 8) on Nov. 16, 2016, shows Cape Point, a prominent local fishing spot, before the island formed. By Jan. 28, 2017, the white froth of breaking waves is visible just off the point, hinting at the very shallow sand below. In the final image, taken July 7, 2017, the island is fully formed.

Barrier islands like Shelly Island are both changeable and resilient. They can be destroyed or shifted by major storms, which happened to many barrier islands during Hurricane Sandy in 2012. But when big storms steal the sand from barrier islands, it often ends up just offshore, so it's available when smaller waves return and start gently building the island back up again, Brian Romans, a sedimentary geologist at Virginia Tech, told Live Science in 2011

This natural process can be disrupted by human activities, like the building of piers or redirection of sediment. 

=============================================================================================

Is your community really ready for hurricane season?

As anyone within 50 miles of a storm-prone coast surely knows, June 1 is the start of the Atlantic hurricane season. But as we head further into July towards the heart of the season in August and September, chances that a storm might spin up in the warming waters increases.

Depending on how recently a storm came calling on your coast, the hurricane-season-is-here coverage may have included recollections of disasters past, an assessment of the season ahead, an expression of concern about the lack of preparedness and awareness in your area, and the usual directions and admonitions now how to be ready for a storm before, during and after.

This is certainly appropriate, the kind of pre-season overview that coastal media has gotten rather good at cranking out – often, because not much changes year to year, so you can dust off last year’s graphics and update the warnings and descriptions. It certainly does remind coastal dwellers (and you coastal-adjacent residents as well) to stock up on storm supplies and make whatever pre-season preparations you can.

But these mundane discussions do not launch a real conversation about survivability over the long haul – about the big-picture issues your community can (or should) address to make it more able to both survive a storm and be ready to bounce back quickly once the wind and waves die down.

How you manage your coastline makes a big difference in how it will protect you in a storm. It simply can’t be said enough: A wide beach, high dunes and elevated structures improve a community’s chance of making in through a severe storm intact. These three elements are crucial enough to warrant a discussion on their own:

Wide beaches: What constitutes a “wide” enough beach depends on your coastline and what kind of storm you’re anticipating (i.e. one that can generate a lot of surge from a long approach and or a slow-moving storm vs. one that is fast moving and does not have time to build up that level of water in front of it). And “wide” is not only sand, but all the “soft” infrastructure options available… wetlands and marshes, reefs and buffers – anything that can put distance between the waves and upland properties and infrastructure.

High dunes: While wide beaches are politically popular, high dunes can face some property owner opposition – until they see what kind of protection that dune can provide them. Again, “high” can be a function of your coast’s tidal range and wave action – and high has to include some stability (via vegetation, fences or other structures) to enable them to stand up to storm waves.

Elevated structures: If high dunes take a little convincing, elevating coastal structures can be a much harder sell to the general public – until they see how much difference it makes for structural survival. That’s why elevation is rarely done pre-storm and is almost always done as a post-storm requirement rather than a recommendation.

One way that storm survivability may become part of the community conversation is as part of a larger effort to make communities more resilient – better prepared before a storm, more secure during a storm, and quicker to recover after a storm. A continuing federal focus on resilience is trying to drive the discussion toward these more proactive approaches, both as a way to speed recovery and to control costs for disaster relief by controlling the potential for damages.

Recent storm history also should warn us to watch for last-minute changes, both for good and bad. Some storms have lost power unexpectedly just before landfall, sparing coastal communities a category level or two of havoc. Other storms have ended up causing more damage than their strength should have warranted, either because of unique conditions or unexpected durability thanks to warmer waters and weaker steering currents (among other products of our climate’s current vagaries).

Local communities should not need to wait for Washington or even the state to act to look long and hard at their own assets and liabilities in storm preparedness and recovery. A federal framework for measuring resilience was one of the recommendations from the post-Sandy studying of the affected coastline, and that can provide both a good entrance into understanding the issue and an objective measure to see where your community might stand today (and could hope to move toward tomorrow). (You can find out more about the study and the resiliency measurements at http://www.nad.usace.army.mil/CompStudy/.)

The best first step is to recognize that preventing disaster is always easier than cleaning up after one, and that some pretty simple approaches – such as wide beaches, high dunes and elevated structures – can make a big difference in how your community looks after the storm should this hurricane season brew up a storm with your name on it.