Shoreline Characteristics and Previous Beach Renourishment Projects

Village of Key Biscayne


Shoreline Characteristics and Sand Supply

The eastern boundary of the Village of Key Biscayne is 6,440 yards, or approximately 1-1/4 miles, of Atlantic Ocean beachfront. Residents and visitors alike enjoy the beauty of the beach and ocean bordering the Village limits, and can walk unimpeded to Cape Florida Bill Baggs State Park to the south, and Miami-Dade County's Crandon Park to the north.

The Key Biscayne beach seaward of the Erosion Control Line (ECL), located generally within the dunes, is the property of the State of Florida. The Village maintains the beach area from the upland dunes to the waterline.

Coastal Systems Incorporated, the Village's beach management consultant, conducts regular assessments of beach and dune performance according to the Village's Long Range Beach Management Plan completed in 1997. Examination of historical beach management data show that the central reach of the Key Biscayne beach (the section that borders the Village) experiences approximately 7,000 cubic yards of erosion and 5 feet of shoreline loss per year.

Prevailing local wind, wave and current patterns that naturally erode the central portion of the arc-shaped Key Biscayne shoreline contribute to this loss, and long-term sea level rise also has an effect on usable beach width. However, Key Biscayne beaches are also starved of sand normally transported from north to south along the Florida coast by a process called littoral drift. The sand-replenishing function of this offshore river of sand in South Florida was impaired by the construction and maintenance of deep artificial inlets along the barrier islands seaward of the mainland. Notable projects include Port Everglades in Broward County and Haulover Inlet and Government Cut in Miami-Dade County.

The Government Cut entrance to the Port of Miami was constructed by the U.S. Army Corps of Engineers (USACE) in 1905. This inlet "barrier" influences the Atlantic beaches of Fisher Island, Virginia Key, and Key Biscayne by restricting the amount of sand naturally supplied to these downstream islands by littoral drift. Authorities have resorted to various beach stabilization and renourishment efforts.  Fisher Island, a privately owned island, constructed a beach littoral "cell" with coastal structures (T-head groins) in 1991 to preserve their beach. The USACE maintains the shoreline along Virginia Key. Coastal groins were constructed along the beach beginning in 1948 with improvements in 1956. In 1969, a 177,000 cubic yard beach nourishment was conducted, followed by another 110,000 cubic yard project in April 1974.  Most recently, the groins fronting the Historic Virginia Key Beach Park were reconstructed in 2003 along with truck-haul beach fill from upland sources.

In Key Biscayne, the most recent comprehensive beach restoration project, completed in 2002, included the installation of dunes anchored by native dune plantings along the length of the Village beach. Dunes help to retain sand on the beach that would normally blow away during storms. This, in turn, prevents sand loss to the entire beach system while increasing protection to the uplands from waves and storm surge. Well-established dunes help to directly buffet and impede storm surge, thus protecting beachfront property, as well as inland infrastructure, from low and medium storm surges. The increased beach area provides expanded potential nesting habitat for threatened and endangered sea turtles. People and associated recreational activities are also supported.

Chronological Summary of Beach Renourishment/Management Projects along the Key Biscayne Beach

  • 2011 Beach Management Strategy

    The Village Council approved a 10-year beach maintenance plan to consist of more frequent, periodic truck haul beach nourishment projects.  Environmental permits will be obtained from local, state, and federal agencies for maintenance projects to streamline the process of conducting these beach nourishment projects within the guidelines of the federal programmatic biological opinions (BO) for southeast Florida. The first truck haul project will be constructed in 2012. The truck haul method avoids impacts to sensitive seagrass beds along the pipeline corridor to the offshore borrow areas and to seagrass beds that have been mapped within the borrow areas utilized for beach construction in 2002 and in 1987. The periodic truck haul beach nourishment approach to beach management is in accordance with the Long Range Beach Management Plan prepared by Coastal Systems, with input from the volunteer Village Beach Task Force, and adopted by the Village in 1997.

  • 2006-2011 Pipeline Corridor Seagrass Mitigation

    The 2002 beach nourishment construction included permitted impacts along the offshore pipeline corridor of 0.14 acres of seagrass. These impacts were caused by the placement of the submerged pipeline along the 6,000-foot corridor from the offshore borrow areas southeast of Key Biscayne to the beach. The pipeline connected the hydraulic dredge pumping the sand slurry to the beach for fill placement.  The initial dredge pipeline was installed in 2000 as beach construction commenced. Due to delays in construction, this pipeline remained in place for approximately 2 years, and a second pipeline was installed by the contractor once beach fill placement eventually commenced in the spring of 2002. Both pipelines were removed in late 2002 at the completion of construction. 

    From 2004-2005, Miami-Dade DERM documented 0.32 acres of seagrass impacts in the pipeline corridor, which represented an increase of 0.18 acre over the permitted acreage.

    For mitigation of these impacts, 0.28 acres of seagrass were to be restored within the pipeline corridor and in the form of prop scar restoration within seagrass beds in Biscayne Bay. 

    The Village negotiated with the environmental regulatory agencies, State of Florida Department of Environmental Protection (DEP) and Miami-Dade County Department of Environmental Resource Management (DERM), for seagrass mitigation related to these impacts. The agencies required a total of 1.33 acres of off-site seagrass mitigation, and the affected seagrass areas along the pipeline corridor recovered naturally. This acreage incorporated all non-permitted impacts, permitted impacts, and increases due to the time delay in mitigation implementation.

    For details of the seagrass mitigation projects, visit the Seagrass Mitigation related to Previous Beach Renourishments webpage.


  • 2008 "Hot Spot" Beach Dune Enhancement

    In response to erosion from 2005 hurricanes, the Village implemented a dune restoration project within erosion "hot spot" areas in the vicinity of the Silver Sands and Sonesta hotels and in the vicinity of Ocean Club and the Beach Club. Approximately 3,800 cubic yards (5,700 tons; 253 truckloads) of beach-compatible fill was truck-hauled to the dune areas and placed above the Mean High Water (MHW) line into the authorized beach fill template. Native dune vegetation was planted to stabilize the newly placed dunes, and the project was completed in April 2008. The design, permitting and construction was funded 100% by the Federal Emergency Management Agency (FEMA).


  • 2007 Dune Maintenance

    The Village conducted dune maintenance which included the removal of exotic vegetation and planting of appropriate native dune vegetation.

  • 2000-2002 Beach Renourishment Project Overview

    The beach bordering the Village of Key Biscayne, representing approximately 6,600 feet of shoreline along the central portion of the Atlantic coast, was widened by a renourishment project implemented by the Village in 2000-2002. Restoration and planting of dunes followed the sand pumping and grading phases of the project. By replicating the beach conditions that were present before disturbance by development, the project recreated a system that previously protected the beach and surrounding areas in an effective matter, while enhancing the biological, ecological and aesthetic value of this erosion control project. Post-construction biological and physical monitoring was completed in FY 2005-2006.

    Three borrow sites, identified for the renourishment project, were located approximately 3,500 to 6,000 feet offshore of the Cape Florida Lighthouse. These areas were determined to contain beach quality sand of sufficient volume for 6 to 7 periodic renourishment projects.

    The predicted performance of the project included a renourishment interval of 8 to 10 years. This interval wss based on the erosional patterns along the Village shoreline and the performance of the 1987 project.

    The Village entered into an Interlocal Funding Agreement with the Miami-Dade County DERM. The agreement stated that DERM provide 50% of the non-state share of the project, effectively 25% of the total project cost. DERM also conducted all the physical and biological monitoring required by state, federal and county permits. The Florida DEP entered into an agreement with the Village to provide 50% share of the total project costs. The Village funded effectively 25% of the project as the local sponsor.

 

  • 1997 Long-Range Beach Renourishment Plan

    The Village Council approved the Long Range Beach Management Plan that summarized alternatives for shore protection and beach nourishment in 1997 after the Plan was developed by CSI and members of Village Beach Task Force appointed by Council. The Village would take responsibility for beach management along the shoreline within the Village limits. Prior to Village incorporation in 1991, Miami-Dade County, in conjunction with the USACE, was responsible for beach management on Key Biscayne. The first phase of this plan was to implement the beach renourishment project in 2000, with continued periodic renourishment events.  Alternatives for federal and state and local cost sharing for project implementation were identified.

  • 1987 Key Biscayne Shore Protection Project

    A one-time nourishment project was conducted in April through June of 1987 by the USACE to address the erosion of the Key Biscayne shoreline. The federal Key Biscayne Shore Protection Project(R101-R113.7) restored 2.4 miles of beaches (excluding a gap at R111-R112.3) using 420,000 cubic yards of sand from an offshore borrow area located one mile southeast of Cape Florida. The project restored a 25 foot wide berm along the shoreline of what would become the Village of Key Biscayne and a 20 foot wide berm at Cape Florida State Park, both at an elevation of +7 ft MLW.  It provided additional beach fill equivalent to seven years of advance nourishment. A terminal groin was also constructed at the south end of Bill Baggs Cape Florida State Recreation Area (R113.7). The project met its performance expectations by preserving a beach through the seven year nourishment interval. In 1994, damage caused by Hurricane Andrew to the terminal groin and adjacent revetment protecting the Cape Florida Lighthouse was repaired.

  •  1969 Biscayne Beach Erosion Control Project 

    In 1969, a federally authorized beach nourishment project was constructed by the USACE at Crandon Park on northern Key Biscayne in conjunction with a contemporaneous Virginia Key project. The project resulted in a 50-foot wide berm at elevation +7 ft NGVD along two segments of shore (R92.5-R96, R99-R101) using 196,000 cubic yards of sand from a borrow area located immediately offshore.

     

     

     

     

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