The following post is from Carl Hobbs, author of The Beach Book: Science of the Shore. For more on the book, you can also read an interview with Carl Hobbs and don’t forget to enter our giveaway to win a FREE copy of The Beach Book!
This summer, enjoy your vacation at the beach with your children and, especially, your grandchildren. The shore will be different when they bring their children to the beach.
Writing in the New York Times on May 15th, Cornelia Dean describes a recent study of Hawaii’s beaches, which shows that 70 percent of the beaches on three of the major islands are eroding. The loss of beach sand is, in part, a consequence of sea-level rise. Dean quotes Charles Fletcher, one of the authors of the report, who concludes, “if we want beaches we have to retreat from the ocean.”
It’s not just Hawaii. In 2007, the U.S. Geological Survey convened a panel of coastal scientists, including me, to assess the potential consequences of different rates of sea-level rise on the shore from the eastern tip of Long Island, New York to Cape Lookout, North Carolina. The study covered major destinations for both day trips and extended vacations, and different coastal settings, for example headlands and barrier beaches, which are subject to different rates of sea-level rise. For all of the low-lying areas, shoreline erosion, overwash, and breaching of the barrier become more likely under any of the sea-level scenarios including maintaining the recent rates of rise. When the rate of sea-level rise is 7 mm per year (2.3 ft per century) greater than the rate during the twentieth century, most of the barrier islands and spits approach or reach a “threshold condition” meaning that there is a high potential for the islands to migrate rapidly or to break into segments or to disintegrate. Some areas, including much of North Carolina’s Outer Banks, are already approaching that threshold.
Rising sea levels attack barrier islands and spits by abetting wave-driven erosion on the ocean side and by flooding it from behind.
At developed beaches backed by seawalls or bulkheads, the rising sea level will bring storm waves to damage the structures more frequently. When waves hit and reflect from a wall, they erode the sand in front of the wall and the beach goes away. Beach nourishment can be a good, temporary remedy when and where there is sufficient economic justification and an available supply of suitable sand. However, beach nourishment is not a one-time fix.
At about eight miles long and a little over a mile at its widest, the barrier island on which Atlantic City, NJ rests is about the same size as the undeveloped and rapidly eroding islands along the Virginia segment of the Delmarva Peninsula. While Atlantic City’s seawall has stabilized the shoreline, it will be nearly impossible to maintain the beach as the ocean rises. That same rising water level is also encroaching on the back side of the island. Meanwhile, the ocean sides of the Virginia islands are retreating dozens of feet a year and the islands are suffering the same assault from behind.
Too often we seem to bury our heads in the sand when we are forced to look at the future. In their recent book The Battle for North Carolina’s Coast, Stanley Riggs of East Carolina University and his co-authors suggest, among other actions, abandoning some of the infrastructure on the Outer Banks and replacing some roads with an expanded system of ferries running between the islands and to the mainland. While their suggestions make good sense, they fail to consider the social and dollar costs of implementing them. Who will decide what to do and will we pay to do what needs to be done? If we delay making and acting on decisions about strategies for dealing with sea-level rise, Mother Nature will continue on her course and we will have fewer, probably starker options.