By Richard Wildermann for Island Eye News
The 35 barrier islands that form a broken chain along the South Carolina coast have important responsibilities. They protect the coastline and are the front-line guardians of a vital ribbon of life at the interface of land and sea. Salt marshes, essential habitat for marine life, nestle behind them for protection.
While they are dynamic and fragile, barrier islands are critical to the Lowcountry’s economy. Everyone loves the beach, so we crowd onto barrier islands to live or just to have fun on a summer weekend.
Barrier islands are particularly vulnerable because they are inherently unstable, low-lying and surrounded by water. Their oceanfront edges are constantly twisted and reshaped by the relentless forces of waves, tides, currents and wind. Rising seas pose an additional threat. As erosion and increased flooding eat away at protective sand dunes, salt water will inundate an island’s interior, killing vegetation and contaminating groundwater. Back-barrier marshes will also be flooded; some will disappear and be converted to tidal lagoons and bays. Behind the islands, the salinity of estuaries and aquifers will increase, threatening aquatic life and water supplies.
In some cases, barrier islands have shown they can take a punch from occasional hurricanes and, with enough time, regenerate naturally or with beach renourishment. But the threat from rising seas is relentless. As the National Oceanic and Atmospheric Administration points out, “The ocean takes a very long time to respond to warmer conditions at Earth’s surface, so ocean waters will continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than that of the current century.”
Since the early 1930s coastal Louisiana has lost about 2,000 square miles of wetlands due to the loss of Mississippi River sediment, subsidence, oil and gas canals, storms, and sea level rise. Almost a billion dollars have been spent in the last 20 years to restore about 75 miles of undeveloped barrier islands that protect the state’s coastal wetlands and human communities. Sand from offshore is pumped onto the islands and piled up with earthmoving equipment. New dunes are stabilized with fences and planted vegetation. Continuing this massive effort will slow but not stop land loss along the Louisiana coast.
Solutions for developed barrier islands are more difficult. We can’t just dump and bulldoze sand on top of established communities. Usually the first steps are to upgrade stormwater and flood management systems and to require that new homes be built higher. Other measures may include requiring greater setbacks for new construction in low-lying areas and elevating roadways where they cross tidal inlets and creeks.
Typically structural barriers are built to keep water out, and when flooding occurs the water is pumped back to the sea as quickly as possible. With expert advice from the Netherlands, some localities are employing a new technique called living with water, that integrates some floodwater into the landscape and allows it to recede gradually. Areas set aside to store the water can be left natural or aesthetically landscaped as amenities.
As the built environment and natural landscape on barrier islands evolve, well-informed planning is essential to identify and put in place the best methods to sustain our quality of life. Communities should assess what natural and man made components of their islands are most vulnerable to sea level rise and then prioritize efforts to address those threats. Cooperation with neighboring islands would help address the many challenges that could overwhelm individual communities. It’s hard to imagine now, but in time the only option remaining for residents of the islands most at risk will likely be to leave.
Richard Wildermann, a Seabrook Island resident, was an environmental specialist and manager with the U.S. Department of the Interior. He directed agency compliance with environmental laws and managed the analyses for offshore oil and gas proposals in federal waters. He currently works with nonprofit organizations in the Lowcountry in opposition to offshore seismic surveys and oil drilling.