Eroding Confidence
By James Hellegaard
For many people, Florida is beaches. Hundreds of thousands of residents live within a stone's throw of the ocean, and 8,000 miles of shoreline are the destination of more than half the state's 40 million tourists annually.
But a succession of severe hurricanes and too much building too close to the water has put the beaches and the people who enjoy them in jeopardy.
The most active hurricane season in 62 years included 19 named storms in 1995, three of which hit the Florida Panhandle.
The giant, pounding waves produced by Allison, Erin and Opal scooped up millions of cubic yards of the snowy white sand that makes the region a tourist mecca, swallowing much of it into the Gulf of Mexico and pushing the rest into living rooms and parking lots far inland.
"It's probably been one of the worst years in terms of erosion, especially on
the west coast," says Robert Dean, chairman and graduate research professor in
the Coastal and Oceanographic Engineering Department at the University of
Florida College of Engineering. "Hurricane Erin and Hurricane Opal both caused
substantial damage due to erosion."
As the hurricane victims struggle to rebuild their lives, people like Dean and associate Professor Daniel Hanes assess the damage and search for ways to minimize destruction from the inevitable next storm.
UF researchers learn much about coastal dynamics right in Gainesville. In a large laboratory just east of campus, they use a 130-foot-long wave tank to simulate nature.
Elsewhere in the warehouse-sized facility, researchers use a wave basin to study things like rip currents and the safe navigation of inlets. A wave maker at one end of the basin sends waves onto a small-scale beach, while large pumps send water into and out of inlets.
Richard Seymour, director of the Ocean Engineering Group at the Scripps Institution of Oceanography in San Diego, calls UF "one of the true leaders in coastal processes."
"UF was the first in the nation to study beach erosion and remains a leader in the field," says Seymour, who also directs the Offshore Technology Research Center at Texas A & M University. "The state of Florida depends upon the University of Florida to provide rational solutions to the state's coastal problems."
Hurricanes have been pounding Florida's coastline for eons, but only in the last century has coastal development led to the staggering financial losses by which today's storms are measured. At about $2 billion, Hurricane Opal was the second most costly storm in Florida's history, exceeded only by Hurricane Andrew in 1992.
Hanes says erosion occurs at some time on virtually every beach, but that on deserted beaches without a reference point, changes in the shoreline are not very obvious.
"In front of a condo the erosion is obvious and alarming," he says.
The natural dynamic along Florida's east coast is for sand to be transported south, says Dean. But the construction of dozens of artificial inlets over the years has disrupted that flow and resulted in excessive erosion of beaches south of the inlets.
"If it weren't for these inlets, many of Florida's coasts would be building up instead of eroding," Dean says.
And the smaller those beaches get, the more vulnerable they are to hurricanes like Opal and Erin.
A member of the National Academy of Engineering, Dean has been tracking the erosion of Florida's beaches since he arrived at UF in 1966. He subscribes to the "beach nourishment" school of coastal engineering, which holds that the best way to protect the shoreline and restore lost beach is to replace the sand, usually by dredging it up offshore and piping it back to the beach.
A 1987 study Dean directed for the state Division of Beaches and Shores found that wider beaches resulted in less storm damage to upland buildings. During a storm, a wide beach will cause large waves to crest sooner and break farther out.
To prove his point, Dean cites the success of beach nourishment projects in south Florida. A study done following Hurricane Andrew found that the 18 miles of nourished beaches in Dade County survived the storm remarkably well. A 2.4-mile-long project on Key Biscayne, closest to where the hurricane's eye made land, actually gained 26,000 cubic yards of sand.
At an average cost of about $5 a cubic yard, beach nourishment is a massive commitment. A $64 million project in Miami Beach involved 10 million cubic yards of sand, enough to build a castle the size of a football field and a mile and a half high. But the alternative, in dollars and human suffering, can be even more costly.
Several years ago, concerns expressed by some Panama City Beach residents shelved an Army Corps of Engineers' proposal to renourish a 16-mile stretch of beach along U.S. Highway 98 at a cost of $33 million.
Today, Highway 98 is a buckled mess and the Corps estimates the beach renourishment project would have saved $50 million in damages.
Shortly after Hurricane Opal struck, Dean was invited to join the Florida Department of Environmental Protection's efforts to quantify Opal's impact on the beach system, including how much sand was lost and when or if it will come back.
The results of the survey will help the Florida Legislature determine the best course of action for restoring the damaged beaches -- from doing nothing to planting dune-anchoring vegetation to nourishing the beaches with sand from offshore.
"It is likely that the 1995 storm season has provided fresh impetus for implementing the Corps' beach nourishment project along Panama City Beach," Dean says. "I hope so. I think it is an investment."
Where eroded sand is deposited in a storm depends on the height of the storm surge, Dean says. In areas with healthy dunes, more sand will go offshore. But if the slope of the shore is low, as it is in most of the state and particularly along the lower Gulf Coast, then the waves will carry the sand farther onto the land in an action known as "overwash."
Thanks to a healthy dune system in the Panhandle, much of the eroded sand in the 1995 storms was taken out to sea, Dean says. That was the case for beaches from Pensacola Bay to Panama City Beach, areas Dean and his colleagues have been surveying for some time.
"Some of that sand will come back over time," Dean explains. "But it may take years or decades for the dunes to rebuild."
On places like Okaloosa Island, however, the storm surge pushed the beach far inland, blanketing everything in its path.
"The lower level of nearly every seaside condominium is gutted and caked with up to three feet of sand," the Northwest Florida Daily News reported. "Where there were houses, there is sand. Where there were streets, there is sand."
While Dean's research focuses on near-term solutions to beach erosion, his colleague, Dan Hanes, seeks a better understanding of the processes that cause beach erosion.
Hanes has done a series of experiments over the past five years funded by about $1 million from the Office for Naval Research that he hopes will help engineers understand the mechanisms involved in erosion so they one day may be able to predict where it will happen.
Hanes is trying to understand the physical processes by which sand is suspended by waves on the Continental Shelf.
Since existing models cannot predict how a shoreline will respond to a storm, Hanes and his fellow researchers have put out an intense array of instruments to measure what's happening to the individual grains of sand in a small area.
Hanes hopes to develop models that will relate the sediment response to climatic forces, which in turn will allow researchers to predict, modify or even prevent changes in the coastline.
"We're trying to understand the physics of the process," Hanes says. "It's really quite mysterious."
Recent advances in electronics, computers, acoustics and video have brought high-tech methods to the study of the very low-tech problem of beach erosion.
Besides devising ways to buffer property from the destructive forces of wind and water, the other half of the formula is to construct buildings so they can withstand the storms.
"There's a right way to develop along the shoreline and a wrong way," says Paden Woodruff, senior engineer with the state Bureau of Beaches and Coastal Systems. He cites the state's Coastal Construction Control Line as the standard for sensible coastal development.
Structures built seaward of the line must be above the crest of a wave that would occur during a 100-year storm and founded on pilings deep enough to withstand severe erosion.
Woodruff says damage from the 1995 storms to structures built before and after establishment of the line in the 1970s was "like night and day." He recalls seeing homes with minor damage next to concrete slabs and piles of rubble.
While structures built to modern standards for the most part successfully weathered the 1995 hurricane season, time will likely take its toll on Florida's beaches. In recent decades, at least one powerful hurricane has hit the Gulf coast every 10 years, Dean says, devastating the area in 1975, 1985 and now in 1995.
"Nature," Dean says, "is going to make some of these decisions for us."
James Hellegaard is a writer for UF News & Public Affairs.
Robert G. Dean
Graduate Research Professor and Chair, Department of Coastal & Oceanographic Engineering, (352) 392-1436,
dean@coed.coastal.ufl.edu
Daniel M. Hanes
Associate Professor, Department of Coastal & Oceanographic Engineering,
(352) 392-9801,
hanes@coastal.ufl.edu