geotimesheader  
Geotimes Home Calendar Classifieds Subscribe Advertise
Geotimes
 Published by the American Geological Institute
December 2000
Newsmagazine of the Earth Sciences

Geophenomena
Seawalls and Sandbags
By Orrin H. Pilkey and Matthew L. Stutz

The owners of the Villa Capriani Condominiums on North Carolina’s North Topsail Island recently built a permanent seawall of stiff vinyl plastic and heavy posts to protect a swimming pool from beach erosion. The seawall violated state law, and the state brought the condo owners to court. But the judge of the North Carolina state court ruled in the owners’ favor.

He said, in effect, that it’s true the seawall violates the law, but the wall is doing no harm right now so let it stay. The judge could not see the long-term, geologic consequences of the owners’ actions.

This ruling is just the most recent of many blows to North Carolina’s regulation of seawalls and, as a result, its ability to protect its beaches. Seawalls built on eroding shorelines destroy beaches. Although they can hold the shoreline in place, seawalls cannot hold the beach in place. After a seawall is erected, the beach backs up against the wall, eventually narrowing to nothing.

  
  A sandbag seawall in South Nags Head, N.C., as it appeared
  in 1997. The wall is higher and longer than it was in 1987. The 
  varying colors of the sandbags, first installed as a “temporary” 
  barrier,  indicate the wall was rebuilt many times. 
  Courtesy of Orrin Pilkey.

It looked like North Carolina had solved its seawall problem in 1985 when it passed ground-breaking regulations prohibiting seawall construction. At the time, only 5 percent of North Carolina’s developed shoreline was armored with seawalls, compared with 55 percent in west peninsular Florida and 50 percent in New Jersey.

The legislation included one exception: If a building will soon topple into the sea, a temporary sandbag seawall can be built to protect it until the building is moved. The bags must be removed in two years. Sandbags are no different than concrete walls when it comes to beach destruction. Their one advantage is that they can be removed easily and cheaply.

This exception for sandbags has become the legislation’s Achilles heel. Since 1985, sandbags have grown from 50 pounds to seven tons with new sandbag technology imported from Florida. Also, North Carolina has proved incapable of enforcing sandbag removal. Hundreds of sandbag seawalls, some as long as 1,200 feet, now adorn our beaches. Some have remained in place for over a decade.

The engineering community has fought the notion of seawall-induced beach loss long and hard and a few engineers still do. One reason for their resistance is that they are “customer oriented.” It is unthinkable that a homeowner or a community shouldn’t be allowed to prevent their property from falling victim to the sea. Politicians are also customer oriented, operating on election-cycle time scales of six years or fewer.

But the loss of beach in front of a seawall can take three to four decades on the East Coast and Gulf Coast. Regulatory enforcement, on the other hand, has immediate political, economic and societal impacts that a government is seldom willing to risk. If beach loss took one year instead of four decades, people could easily see and respond to the problem. In our view, the long-term nature of the geologic process of beach loss is the reason North Carolina is failing to protect its beaches.

In contrast to its management of beaches, North Carolina has initiated an ambitious, proactive approach to regulating river flood plains. The state is buying structures that have been repeatedly flooded, and has spent $60 million since Hurricane Floyd last fall. But on the beaches, the state is about to sign off on a $1.6 billion, 14-mile-long renourishment project for the Outer Banks that will secure the status quo for the next 50 years. The cost of buying out all the buildings and property that will be affected by the project would be only one-fourth that amount. As with flood plain management, relocation and buyouts are the most prudent and economical long-term approaches to beach management.

Few beachfront property owners view seawall-induced beach loss as a problem. For them, their property is more important than the beach. Although its details are different, the seawall dilemma is not unlike the problem of allowing buildings on eroding sea cliffs, along landslide-prone hills, in river floodplains, and at the base of a boulder-strewn slope. But people, if they even recognize the hazard, consider the likelihood of cliff erosion, landslides, floods and boulder falls to be a roll of the dice and they are willing to take the chance. Beach loss in front of seawalls, on the other hand, is a certainty on eroding shorelines.

Even when everyone agrees the outcome of a geologic process is certain, we don’t respond well and we leave the problem for the next generation. Clearly we have a long educational road ahead of us to convince the public, our engineers and our politicians to take a realistic view of the long haul.

Pilkey is a professor emeritus and Stutz is a Ph.D. candidate, both in the Division of Earth & Ocean Sciences at Duke University, Durham, NC 27708.
E-mail: mls4@duke.
edu
 
 

Other Activity

Ski danger
Authorities in Chile heightened the alert status near Villarrica Volcano on Nov. 1, due to increased seismic activity around the mountain. Climbers and tourists were forbidden to ascend the 9,200-foot volcano, and police stepped up patrols of the region to enforce the warnings. The volcano has experienced more frequent seismic activity since Oct. 5, when boulders blocked one of its craters. Known as the “Switzerland of Chile,” Villarrica is one of South America’s most popular ski resorts.

Storm
Tropical storm Bebinca slammed the Philippines’ east coast early Nov. 2, packing winds of 69 mph as it moved on its west-northwesterly path over the main island of Luzon. Bebinca hit the storm-ravaged archipelago following the deadly typhoon Xangsane, which killed scores of people in the Philippines and Taiwan earlier in the week and were a cause of the runway crash of a Singapore Airlines jet in Taipei.

Landslide
At least 40 people in Indonesia were buried alive during the first week of November as torrential rains in southern parts of densely populated West and Central Java triggered numerous landslides. More than 4,000 people have been left homeless in the destruction caused by the slides. Construction crews struggled to reopen the region’s main roads, including the Trans Java Highway.
 


Associate Editor Christina Reed compiles Geophenomena.



Geotimes Home | AGI Home | Information Services | Geoscience Education | Public Policy | Programs | Publications | Careers

© 2014 American Geological Institute. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the express written consent of the American Geological Institute is expressly prohibited. For all electronic copyright requests, visit: http://www.copyright.com/ccc/do/showConfigurator?WT.mc_id=PubLink