Are new reefs the answer to beach erosion?
STORY BY STEVEN M. THOMAS, (Week of August 18, 2011)
A quantum shift in Indian River County’s strategy for preserving the barrier island beaches may be getting underway.
At their two most recent meetings, mayors of the county’s five cities pushed the idea of a comprehensive scientific study to see if new approaches to the use of artificial reefs may be the most cost-effective way to protect 32963’s beaches from erosion.
A 4,000 foot long assembly of concrete structures placed off of Vero’s central beach in 1996, the so-called PEP reef barely visible in the photo above, has been the only experiment with artificial reefs along county’s 22 mile stretch of shoreline.
Now County Coastal Engineer James Gray, the man responsible for defending 32963’s invaluable beaches from the impact of wind, waves and storms, says he too favors the idea of a study to see whether new types of man-made breakwaters might be effective.
“The county needs to explore all available options,” says Gray. “The mayors’ meeting is a good starting point. Their support for a study – including potential financial support – is encouraging. We need to update our beach preservation plan, and this study could be a good step in the right direction.”
The study discussed by the mayors would survey 11 miles of Atlantic coast, from The Spires on Vero’s beachfront north toward Sebastian Inlet, using the latest computer modeling software to determine the kinds of artificial reefs that would work best and in what locations.
“Up until now, there has only been one alternative tried in that area to stabilize the beaches,” says Jim Eagan, executive director of the Marine Resources Council. “It has been pump sand and dump sand, but there are multiple types of artificial reefs out there that have proven effective.”
A 2011 white paper issued by the highly respected American Shore and Beach Preservation Association confirms Eagan’s assertion, stating: “There are many examples worldwide of erosion control structures that have been used to successfully retain sand and control erosion.”
“We have a responsibility to maintain our beach infrastructure,” says county Commissioner Joseph Flescher. “It is extremely costly to deliver the sand continually while knowing that it is going to be eroded tomorrow. I don’t believe we are going to be in a position to continue that process in the future and I am a strong proponent of considering alternatives to sand delivery.”
The county’s ongoing 6.6-mile beach replenishment project on the northern part of the island that aims to dump 586,000 cubic yards of inland sand is now budgeted at more than $15 million. That is double the original $7.2-million contract price agreed to by the county and sand contractor Ranger Inc. The job has dragged on for years longer than scheduled and is still not complete.
The study being discussed by the mayors would cost about $250,000 according to Eagan, who secured that estimate from Dr. Gary Zarillo, a Florida Tech professor and scientist, who is likely to conduct the study.
Gray, Flescher and Eagan all emphasize that artificial reefs, which would be designed to reduce wave impact and keep sand from washing away, would not necessarily replace sand dumping entirely.
They might replace sand dumping in some locations while being used in conjunction with beach replenishment in other areas.
“The Marine Resources Council has no agenda,” says Eagan. “We are not saying just use reefs instead of sand. We are saying it would be smart to do the science before spending millions of dollars. Dr. Zarillo is a world renowned expert in this kind of modeling. We are excited about a scientific evaluation because of degree of accuracy he can provide.”
“It is only in recent years that we’ve developed the modeling tools to predict how artificial reefs will perform,” Zarillo says. “Using realistic, physics-based models, we will look at the full spectrum of what is going on along the coast. Based on that, we can provide information about how the county might proceed.”
According to Eagan, Zarillo’s modeling tools are “very, very powerful.” By plugging in factors such as water depth, wave height, current speed and direction, prevailing winds and sand composition, the computer program can predict the effect of a variety of structures on any given stretch of the coast.
“Imagine casting a net over the entire 11-mile stretch,” Eagan says. “With this kind of modeling, you can look and see what would happen at any interstice in the net if you installed a particular structure.”
With less accurate tools than he has now, Zarillo modeled the effect of Indian River County’s existing shore protection reef, the PEP reef. PEP is an acronym for prefabricated erosion structure.
“The sand industry fought unbelievably hard against the PEP reef,” says Eagan, but it has been effective in protecting the beach, even though it didn’t work exactly as planned.”
The central beach structures are 25-ton, steel-reinforced chunks of concrete with a triangular cross section, sloping down from a narrow crest to a wide base on their shore and ocean sides. The 215 individual units are interlocked to form 11 “reef” sections placed alternately closer and further from the shore.
A 2007 study, “From Failure to Success: Update on the Vero Beach P.E.P. Reef,” found “an overall reduction in shoreline erosion and increased stability of the beach” between 1996 and 2006. It also found the amount of sand on the beach and the width of beach adjacent to the reef increased during that time, even though the beach was not replenished by sand dumping.
Coastal Tech engineer Michael Walther says the reef has been merely “innocuous,” and an Army Corp of Engineers study completed in 2000 noted that the reef structures had settled deeper into the sand bottom than they were designed to, reducing their wave-reduction effectiveness.
Most others seem to agree the reef, which survived the 2004 hurricanes, has been effective despite the settling.
“It has performed more or less as designed,” says Zarillo. “Over the years it seems to have held the beach. There is no way it can be classified as a negative.”
At the July 25 Mayor’s Meeting, Orchid Mayor Richard Dunlop showed before and after pictures of the central beach to examine the reef’s effectiveness and said that in the mid-1990s “water went under the Ocean Grill,” which is not the case today.
“It has reduced erosion at the site, and from that perspective it has been very successful,” says Beth Mitchell, chairwoman of the Sebastian Inlet District Commission.
“In the absence of the PEP reef, the shoreline might have retreated,” says Gray, who sees artificial reefs as a way to protect the county’s recent multimillion dollar investments in beach replenishment.
Besides prefabricated reef structures, other erosion prevention devices include reef balls, rubble reefs, groins and jetties. A modeling study would be able to predict the effectiveness of each type of structure in any given location, with or without sand replenishment.
“We are able to come up with a scientifically valid model that so perfectly simulates what is going on out there that you can get a real handle on what various structures will do before spending big bucks to install them,” says Eagan.
Indian River County's developing interest in manmade beach protection structures is part of a wider reevaluation of erosion prevention.
For decades, indiscriminate use of coastal armoring such as seawalls and jetties caused as many problems as they solved by redirecting wave energy in ways that washed away adjacent or nearby beaches.
Environmental organizations came to oppose such structures even as the sand industry gained clout, and beach protection became synonymous with sand replenishment, especially in Florida.
“Florida has been more resistant that other states to support infrastructure enablement, barriers to erosion,” says Commissioner Flescher. “But breakwaters do work. They are used where I come from up north and sand replenishment is needed less often. A permanent structure means less sand delivery and less burden on the taxpayers.”
Now, with federal and state money for beach replenishment drying up even as sand dumping costs escalate, a nationwide reappraisal is underway.
“Reintroducing Structures for Erosion Control on the Open Coasts of America,” the American Shore and Beach Preservation Association white paper, notes that “sand shortages (especially in south Florida), higher dredging costs and environmental impacts on nearby habitats are constraining designers to use less sand in beach management projects.”
Those conditions coupled with advances in artificial reef technology and modeling capability make the cost-effective use of permanent structures likely in Indian River County in the near future.
“There has been a political bias against structures in the marine environment,” says Mitchell, “but we are in a completely different climate now concerning how to fix beaches and who is going to pay for it.”
The mayors left their last meeting July 25 with plans to consult their councils about sharing the costs of the reef study based on the amount of shoreline in each community. They are scheduled to reconvene to further consider the matter on Sept. 26, and are inviting county commissioners and the county Beaches and Shores Commission to attend.
“We need further discussions to figure out who is going to pay what,” says Flescher, who attended the mayors’ June meeting. “But I saw a lot of support for the study among the mayors. I think there is a consensus that it’s a good idea, and if it is done fairly, I believe we may have something here. It seems to me, a study would be a minimal investment for a maximal value.”