National Erosion Control Development and Demonstration
Program (Section 227)
Miami Beach, Florida
Description
The City of Miami Beach project site extends along the shoreline for approximately 762 m
(2,500 ft) with a southern limit near 63rd Street. The Florida Department of Environmental
Protection has established survey monuments along the Dade County shoreline at 305 m
(1,000 ft).
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
View of Miami Beach, Florida
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 (3.3 ft)) to high relief (>3 m (9.8 ft)). The
continental shelf offshore of the project site is 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 inci-
dent direction of wave energy along the Dade County shoreline is bimodal. Nor′easters
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. The mean tide range is 0.77 m (2.5 ft) with spring tides of
0.93 m (3.1 ft) mean low water. The Federal Emergency Management Agency estimates
5-year return period storm surge in the area as 1.04 m (3.4 ft), 10-year as 1.61 m (5.3 ft),
20-year as 2.01 m (6.6 ft), 50-year as 2.59 m (8.5 ft), and100-year as 3.11 m (10.2 ft).
The shoreline recession rate in the demonstration project site ranges from 4.27 m (14 ft) to
7.62 m (25 ft) 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.
U.S. Army Engineer Research and Development Center
May 2005
www.erdc.usace.army.mil
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