657 “New” Barrier Islands Charted
by Owen James Burke
Thanks to satellite images, topographical maps, and navigational charts, there are now 2,149 documented barrier islands in the world–657 more than previously thought. How did they go uncharted for so long? The islands are not newly formed, but probably went by overlooked. The low resolution of a 1997 NASA image of Brazil’s Gurupi River Delta (above) may give some insight.
For this past survey the satellite technology was much more handy and developed, distinguishing many barrier islands that did not register in the previous set of images.
It was commonly agreed that barrier islands could not exist on coastlines where tides exceeding 13 feet occur, so many places may not have even been studied in the first place. Barrier island chains are generally found on coastal areas with little tide variation (and most of them are), but there are now several exceptions. The Gurubi River delta in Brazil sees spring tides exceeding 20 feet, but it also consists of a 571 km, 54-island chain south of the Amazon rivermouth.
“This provides proof that barrier islands exist in every climate and in every tide-wave combination,” said study team member Orrin H. Pilkey of Duke University. “We found that everywhere there is a flat piece of land next to the coast, a reasonable supply of sand, enough waves to move sand or sediment about, and a recent sea-level rise that caused a crooked shoreline, barrier islands exist.”
Don’t pack your bags just yet however, none of these new findings are suitable for human inhabitance. What a barrier island does provide is just that though–a barrier, or a shelter, and when a storm arrives it is often all that lies between a habitat and a disaster.
For example the south shore of Long Island holds one of the most distinct barrier island chains in the world. If it weren’t there, hurricane swells and winter northeasters would send rivers of floods over New York, destroy a delicate ecosystem that serves as a nursery for young maritime critters.
As coastal development continues, barrier islands are at more and more risk. Unlike stationary land, barrier islands build up, shift, and erode over time in response to storms and swells. When we construct jetties, sea walls, groins, and constrictive barrier walls, we prevent barrier islands from performing their necessary adjustments, and pretty soon they become ineffective. Hopefully, with new satellite capabilities, scientists can now monitor and detect any drastic or threatening changes that might present themselves.