DEMONSTRATION SITESection 227
National Shoreline Erosion Control Development and Demonstration Program
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).
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)
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Figure
1. 63rd Street,
Miami, Florida erosional hot spot encroaching on vegetated
dune. |
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Figure
2.
63rd Street, Miami, Florida erosional hot spot
relative to wide adjacent beaches
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Aerial Photography
