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Section 227
National Shoreline Erosion Control Development and Demonstration Program 

DEMONSTRATION SITE

Miami Beach, Florida
USACE Jacksonville District, CESAJ - Contact:
Mr. Jonas White

Status

A coastal processes evaluation of the project site was completed in September of 2001 in coordination with the Dade County Beach Erosion Control and Hurricane Protection Project.  Click on documents to download a copy of the report, Coastal Processes Analysis:  Dade County and 63rd Street Hot Spot.  Innovative and non-traditional products and/or methodologies for reducing erosion at the project site are currently being solicited.  More information on submitting a proposal is under the Special Broad Agency Announcement (BAA).

Site Description

The City of Miami Beach is located on the southeast Florida coast in Dade County.  The project site extends along the shoreline for approximately 762 m, with a southern limit of 63rd Street.  The Florida Department of Environmental Protection (FLDEP) has established survey monuments along the Dade County shoreline at a nominal separation distance of 305 m.  The project site is located from approximately FLDEP monuments R-44 to R-46.5. 

Prior to the recent emergence, the Dade County shoreline was inundated by the Pamlico Sea, which left thin deposits of Pamlico sand lying unconformably over the widespread Miami Oolite.  The Dade County shoreline consists of a barrier island with a bay behind it, but is not a typical young shoreline.  Where the typical barrier island is a sand dune moving progressively over the bay sediment, the Dade County barrier island (i.e. Miami Beach) probably developed on a shallow sandstone reef where mangroves grew and trapped additional sediments creating a stable island.  A series of three reef lines (with areas of sand in between) exist offshore of the project site.  These reef lines vary in relief (rises in elevations above adjacent sandy areas) from low relief (< 1 m) to high relief (> 3 m).  The continental shelf offshore of the project site is relatively narrow with the shelf break located only a few kilometers from the shoreline. 

Analysis of the Wave Information Study revised Phase II database indicates that the incident direction of wave energy along the Dade County shoreline is bimodal.  Northeasters produce large waves which strike the Dade County shoreline from a steep northerly angle during much of the fall and winter months, and the easterly/southeasterly trade winds produce smaller but more persistent waves from the eastern and southern sectors during the rest of the year.  The direction of peak wave energy is from the northern sectors, as evidenced by southerly net sediment transport, but the wave energy incident from the southern sectors is significant.  Referenced to the elevation of mean low water (MLW) at the City of Miami Beach, the National Geodetic Vertical Datum is +0.39 m while mean high water (MHW) is +0.77 m.  Therefore, the mean tide range is 0.77 m with spring tides of 0.93 m (MLW).  The Federal Emergency Management Agency estimates storm surge return period in the area as 1.04 m (5 year), 1.61 m (10 year), 2.01 m (20 year), 2.59 m (50 year) and 3.11 m (100 year). 

The shoreline recession rate in the demonstration project site ranges from 4.27 m to 7.62 m, annually (excluding the effects of beach fill).  Shoreline recession in this area is in direct correlation to local impacts of tropical and extratropical storm events. 

Problem Statement

The 63rd Street demonstration project site can be described as an “erosional hot spot” within the Federally authorized Dade County Beach Erosion and Hurricane Protection Project (BEC&HP).  The authorized BEC&HP is designed to provide a specific level of storm damage reduction and recreation benefit through the establishment and maintenance of a beach nourishment design template.  This design template must provide for the life of the project in order for realization of the return on Federal and non-Federal investments.  Monitoring of the BEC&HP indicates that shoreline recession at the demonstration project site exceeds the rates experienced on adjacent shorelines.

Project Description

Project design is pending detailed analysis of coastal processes at the project site.  Following which, conceptual designs will be solicited and considered for implementation.  The primary objective of the demonstration project will be to hold the maintain template dimensions between renourishment in an innovative or non-traditional manner.  This demonstration project will also document the performance other non-traditional methods implemented maintain the beach nourishment design template at other erosional hot spots in the BEC&HP (e.g., use submerged rubble mound reef for wave attenuation, and use of T-head groins or headland structures for sediment retention).

Photographs
(click on photo for larger image)

Miami Beach Figure 1.  63rd Street, Miami, Florida erosional hot spot encroaching on vegetated dune.
Miami Beach Figure 2.  63rd Street, Miami, Florida erosional hot spot relative to wide adjacent beaches

 

Aerial Photography

Plan Map of Study Area

Hot Spot Location