History: The Dangers of Dredging

| May 29, 2018

By Philip M. Farrell, MD, PhD

Sarasotans have had a long-term love affair of damaging nature… most of our historical environmental disregard is spurred by arrogance… Paul Roat, Siesta Sand, December 2013 [https://siestasand.net/sarasota-history-13/]

The area between Longboat Key and Big Sarasota Pass as depicted in the U.S. Coast and Geodetic Survey of 1883

   The primary weapon used to damage nature on the waterways of Sarasota County is the dredge. Dredging projects are generally motivated by financial interests and can be both destructive and constructive. Their damaging environmental impacts are immediate, but the long term harm is the greatest concern. During the first half-century of Siesta Key development, a series of dredging projects were completed that either improved or damaged this once pristine barrier island— depending on your viewpoint. Ecologists and commercial fishermen will argue that the harm has outweighed the benefits, while real estate developers disagree.  

   Many of Sarasota County’s dredging projects have been performed by the U.S. Army Corps of Engineers (USACE) — an organization that has been responsible for the development and maintenance of navigable waterways in the United States since 1824. Historically, the 54-mile long Gulf Intracoastal Waterway (ICW) was Sarasota County’s first dredging project and was designed to facilitate transport of goods along the southwest coast. During 1895, as settlements expanded and populations increased, business entrepreneurs and local citizens requested federal support and persuaded Congress to appropriate $5,000 for USACE to dredge a five-foot deep by 100-foot wide channel from Tampa Bay to Sarasota Bay. This was an immediately successful project, leading to significant commercial benefits without apparent harm.  Despite the emergence of better railway transport, extension of the ICW to Venice occurred in 1907, cutting through and destroying the ecologically important area known as “The Mangroves,” and disrupting shellfish.

Initial blow to closing Midnight Pass

   Although it must have been obvious that the ICW lacked commercial value after World War II, Congress appropriated funds in 1945 for an ambitious nine-foot deep re-dredging operation along the entire 54 miles.  In retrospect, its purpose seems unclear because recreational boating had not yet become popular. Whatever the rationale, the USACE dredgers arrived at Sarasota Bay in 1962 with much heavier equipment. By 1964, they were dredging around the south tidal inlet to Little Sarasota Bay at Bird Islands near the channel known as Midnight Pass.  The USACE engineers also dumped 225,000 cubic yards of dredged sediment around the Bird Islands and thereby altered the tidal flow through Midnight Pass— likely initiating its relentless migration northward and eventual closure. Harmful effects on the ecology, fishing, and shell fishing were soon evident also.

Siesta Key canals…

   Dredging on Siesta Key per se began in 1907 as the Siesta Land Company dug out a 35- foot wide canal that eventually segregated Bay Island and was named Hansen Bayou for the family of Ocean Deep Hansen Roberts. Ten years later, when the first north bridge was built, it was accompanied by more dredging to establish bayous and canals named for the Roberts’ children.

   Private dredging more radically altered Siesta Key in 1925 with the heart-shaped Archibald’s Canal that created Palm Island. This real estate development effort, however, was thwarted by the 1926 Miami Hurricane and Great Depression. Later in the 1950s, four extensions of the Grand Canal led to successful neighborhoods such as Siesta Isles.

   On the other hand, studies by New College Professor John Morrill published in 1974 revealed the poorly designed and even frivolous nature of these dredging projects. The Grand Canal’s long intricate system winding like a maze has many dead end finger canals with sluggish circulation and many sources of pollution that adversely affect the ecology and water quality. In addition, its seawalls may be inadequate as water levels rise with global warming.

Manmade…

Owen Burns huge dredger used in the 1920s for massive dredge-and-fill projects

   The largest dredge-and-fill project of the south Gulf Coast, undertaken during 1923-25 by Owen Burns, continues to raise questions about its long term sustainability. Burns’ crew used huge dredging machines to move millions of cubic yards of sediment and accomplish the real estate development dreams of John Ringling. The extraordinary nature of this massive project is evident from a 1883 U.S. Coast and Geodetic Survey that shows the spits of sand Burns aggregated to create Bird Key, Lido Key, and St. Armands Circle. Heavy rains, storm surges, and rising sea levels threaten to flood these man-made isles. 

   Moreover, every attempt to prevent Mother Nature’s impact with coastal engineering projects on Lido Key has failed, including groins of various kinds, tire barriers that washed up on Siesta/Crescent Beach, and a series of nourishment efforts that have provided only short-term benefits. The current proposal to dredge up 1.3 million cubic yards of sediment from Big Pass by USACE is likely to suffer a similar fate and only serve as another temporary measure. Yet no beach nourishment project of such design and magnitude has ever been attempted so the degree of damage is unpredictable.

   The greatest danger is to “America’s Best Beach” on Siesta Key. The lessons learned from other experiences with tidal inlet disruptions make it clear that the result of a massive Lido/USACE dredging could transform it to an eroding beach like Turtle Beach. And, history also shows that once erosion begins on a barrier island, it is relentless. 

   Massive dredging projects always endanger wildlife. Maiming and killing manatees occurs regularly on the ICW. Destruction of habitat is the potential problem for fish. According to Grant Gilmore Jr., president of the Vero Beach consulting firm Coastal and Ocean Science Inc., one species that would be affected by dredging Big Pass is the smalltooth sawfish, which is listed as “critically endangered.”

   Big Pass also is essential habitat for “hard-bottom species” such as grouper and snapper. Lastly, as the July 2015 USACE Engineer Manual on “Dredging and Dredged Material Management” points out, “the sea turtle is one of the animals most vulnerable to the effects of beach nourishment on the South Atlantic and Gulf Coasts.”

You can read more about these dangers and coastal geologists’ opinions in An Illustrated History of Siesta Key: The Story of America’s Best Beach, which is sold at both Davidson Drugs stores on Siesta Key, Captain Curt’s gift shop, and Crescent Beach Grocery.

Tags: , , ,

Category: Feature, News

Comments are closed.