Slow-moving Waves of Sand
Thursday, November 15, 2012 • 6:52pm
We like to think of the land under our feet – and our houses - as solid. But that’s just not the case on New Jersey’s ever-shifting barrier islands. I asked Dr. Emile DeVito of New Jersey Conservation Foundation to share his thoughts on our state’s barrier islands.
Barrier islands are interesting geological phenomena, waves of sand that slowly move inland in response to sea level rise. Humans generally like stability and dislike change – and, thus, have done everything possible to keep shore communities static. After all, many of us have built homes, visited the Jersey Shore and have lifetimes of memories of this spectacular place. But the geophysical foundation of barrier islands continues to change. Even before Superstorm Sandy wreaked havoc on our beloved Jersey Shore, the barrier islands were on the move westward toward the mainland.
As natural barrier islands slowly travel westward, they gain elevation relative to fixed points on the mainland. Sand is blown onto the dunes by wind and trapped by the ecological marvel Ammophila breviligulata, commonly called American beach grass.
Beach grass is tolerant of salt, and can survive being buried alive by sprouting new roots from the base of its buried stems. Beach grass seeds are also excellent at colonizing newly deposited or eroded sands left bare from cataclysmic storms like Sandy.
Along the quiet mudflats on the bay side of barrier islands, new soil deposits add girth and are colonized by maritime forests of holly, black cherry, and red cedar. Slowly or in giant lurches, a natural barrier island rises and moves toward the mainland, on average keeping pace with sea level rise.
In some areas of this state we’re in, ancient barrier islands have swept so far to the west that little or no bay remains. In other areas, wide bays like Barnegat still exist.
Barrier islands protect the mainland from the powerful surges of the ocean. If left in a natural state, their plant communities simply move in response to sea level rise and storms.
If you dig straight down in the sand at Island Beach State Park, eventually you’ll hit the organic remains of a buried maritime forest once perched on an ancient shoreline of Barnegat Bay, when sea level was lower and the island was east of today’s location. Island Beach State Park has remained ecologically identical for more than a millennium, but it is not in the same place!
Natural plant communities move by themselves, but gas and sewer lines, roads, and house foundations of human communities do not. Static objects can’t be protected forever; eventually they will be at or below sea level, like the trolley tracks of the former town of South Cape May, long ago claimed by the Atlantic.
Some structures can be raised on stilts, and seawalls can protect roads from small and moderate storms. But seawalls deflect the energy of ocean waves, instead of absorbing water and energy as does a beach and dune system. Where seawalls are in place, the loss of beach sand (natural or artificially-replenished) accelerates. Sand is carried north toward Sandy Hook from Sea Bright, or south from Seaside Park to the Barnegat Inlet jetty by the omnipresent longshore currents that parallel the beach.
Armed with the knowledge of the inevitable westward movement of our barrier islands and our growing understanding of climate change and its impact on sea level rise and storm frequency, will we change our behavior and recognize the futility of building and living on barrier beaches? Or will we blindly ignore the realities of the changing ocean, and rebuild our Jersey Shore exactly as it was before the storm?
Tim Dillingham, Executive Director of the coastal advocacy group, American Littoral Society, shared his thoughts with me about rebuilding. “As the communities along the shore are rebuilt, there is an opportunity to reduce the risk they will face from inevitable future storms, to make them more resilient, to restore some of the lost natural environment of the coast. We should restore the lost natural elements of the Shore along with the built; we should rebuild dunes, beaches, salt marshes and oyster reefs: each provides natural storm protection.
“There are no strategies which will keep us completely risk free. However, the opportunity to shape a new coastal landscape in the rebuilding to come provides an opportunity to reduce that risk, and to restore a better balance in our co-habitation of the coast with natural, and predictably recurring events like hurricanes.”
The recent tragedy is forcing us to confront the geological and climatological science of our barrier islands. As we look to rebuild and recover, we must deliberately and strategically manage a retreat from certain unsustainable activities on the barrier islands. And we can use a portion of the state’s Blue Acres program to buyout private property in critical hazard areas, perhaps a better use of limited public dollars than the controversial federal flood insurance program. Beach and dune restoration projects can take into account the physics of tides and ocean currents. Tourism infrastructure and public access facilities should anticipate sea level rise and storm surges.
Over the last 150 years, the Jersey Shore was intensively developed due, in part, to a lack of scientific understanding. We now have the knowledge, tools and opportunity to make sure history won’t repeat itself.
For more information on our state’s coast please visit the American Littoral Society website at www.littoralsociety.org.