'Beach 101' offered for 'unprecedented' beach renouishment
By Paul Roat
Islander Reporter
An "unprecedented number of beaches" which lost sand after an "unprecedented number of hurricanes" will result in about $180 million in beach renourishment dollars to Florida shores, including Anna Maria Island, according to a U.S. Army Corps of Engineers official.
Bids to add roughly 5 miles of additional sand along the Island's Gulf of Mexico shore are scheduled to be opened Friday, April 24. The estimated $4-million project will add about 400,000 cubic yards of sand to the beach, with work projected to start by May.
That's if all goes well, according to Corps Senior Project Manager Rick McMillen. He said the federal government was breaking new ground after the four hurricanes hammered the Sunshine State last summer and fall - first Charley in Southwest Florida, then slow-moving Frances in Southeast Florida, powerful Ivan in the Panhandle and then Jeanne on virtually the same path as Frances.
The storms prompted the U.S. Congress to pump vast funds of money into beach renourishment efforts in the state, McMillen said. Coupled with non-federal funds - read state or local dollars - the Corps was able to dust off past projects that requested additional sand and was able to do in months what it would usually take years to accomplish: 17 massive beach renourishment projects.
"It's unprecedented to do all these beaches at one time in Florida," McMillen said last week, "and unprecedented to have four hurricanes in one year."
McMillen and other federal officials were on Longboat Key to discuss the projects and offer a "Coastal Engineering 101" course. His basic premise regarding shorelines is that they tend to erode.
Groins, seawalls, rock revetments or other hardening structures generally exacerbate beach erosion, either at the local site or "downstream," McMillen said. The prevailing offshore drift pattern for currents and sand is north-to-south, so upstream properties will generally contribute sediment to more southerly neighbors.
Depending on the time of year, sand will also move onto and off the beach in a more linear fashion. Winter, with its nor'easters, is a bad time for beaches, since the long-term pounding of high waves and winds from the north drives sand off the beaches and away from the area where it can move readily back onto shore.
Hurricanes, McMillen said, are generally not all that bad for the beach because of their speed. A two- to three-day storm event with high waves, although devastating to structures, often is only a brief problem for the beach.
"In hurricanes, sand movement is generally directly offshore," he said, "but then it comes back."
McMillen added that hurricanes also are summertime events, which is a traditional time of greater width of beaches in Florida. No nor-easters and gentler winds from the southwest, which result in more sand pushed ashore.
He said that the dry beach that most assume is "the beach" is only a fraction of the total shoreline profile, a profile that often stretches out to 3,000 feet from the mean high water line as far as coastal engineers are concerned when they work toward developing a model for a beach renourishment project.
Waves, offshore sandbars, erosion trends, erosion speed - all of those and much more data contribute to the final beach picture.
McMillen said the average erosion rate of Florida beaches was 1 foot per year. That rate can change based on the beach, though: A shoreline in Northeast Florida is losing up to 22 feet of beach a year.
Manatee County, and Anna Maria Island, have had two major beach renourishment projects, one in 1992-93, another in 2002. There have also been several sand-addition programs based on dredging of Longboat Pass for navigational purposes over the years.
In the upcoming effort, McMillen said, Manatee County first requested the project from the Corps, then rejected it in fear of inferior sand, later agreeing to the sand quality.
The 1993 project caused some angst among beachgoers with the shell-filled, rocky material that came ashore from huge pumps. The latest project, using finer-grain sand, was generally accepted by Islanders as a fine beach addition.
But McMillen offered a chilling commentary on fine-versus-coarse-versus-shelly material coming ashore:
"If you're looking for sugary sand, it generally won't last as long."
The upcoming beach renourishment project is slated to use mostly fine-grain sand from nearby offshore borrow sites. Projected length of the sand's stay ashore before the next renourishment is estimated at eight to 10 years. |
