BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
SARASOTA COUNTY – LIDO KEY HURRICANE & STORM DAMAGE REDUCTION PROJECT
City of SarasotaSarasota CountyUS Army Corps of Engineers
22 October 2013Sarasota, Florida
Presented by: Milan A. Mora, P.E. Jason Engle, P.E.
James LaGroneKathleen McConnell
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | JACKSONVILLE DISTRICT
Information PresentationBOCC Joint Meeting
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
OVERVIEW – PROJECT SCOPE Authorized WRDA 1999
• Authority was contingent on a feasibility assessment of the project.
• 2002 Feasibility Study with Environmental Assessment (amended April 2004) determined that project was technically sound, environmentally acceptable and economically justified.
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
2
1971
2006
1986
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
OVERVIEW – PROJECT FEATURES
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
3
D2
C
B
Project Scope Project Length (ft) = 8,280 (R-35 to R43) Design berm elevation (ft) = +5 NGVD Approximately 460,000 cy of design and 615,000 cy
of advance material (1,075,000 cy for Initial Const) Three groins along the southern portion Borrow Areas: Big Sarasota Pass (BSP) & New
Pass 5-year nourishment interval over 50-year life 615,000 cy required for each re-nourishment
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PROJECT PLAN
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4
1) Placement:• Place approximately 1.1M CY of sand on Lido
Key
2) Source:• Obtain Sediment for Nourishment of Lido Key
• Egmont Key (Tampa Bay)• Offshore of Longboat Key• Ebb Shoal at Big Sarasota Pass (BSP)• New Pass – Future
3) Retain:• Construct Three (3) groins at the south end of
Lido Key
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PLACEMENT – LIDO KEY
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5
MHW Line - Design Berm
2013 MHW Line
MHW Line - Advanced
Berm
FDEP Monument R-39 (Lime Tree
Resort/Condos)
150’150’
80’ Design
Berm @ 5’
Advanced Berm
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SOURCE – BSP BORROW AREAS
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6
D2
C
B
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
RETAIN – SOUTHERN GROINS
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
7
Retain
Beach
Nourishmen
t
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PROJECT PLAN – BORROW AREA QUESTIONS?
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BORROW AREAS? What are the proposed borrow
area footprints?
How will this affect Big Sarasota Pass morphology?
How will this affect Siesta Key?
What are the effects on the navigation channel?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
ALT D2, C, B – 1.7 MCY BORROW AREA FOOTPRINTS
D2
C
B
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
Flood Marginal Channel
Relic
Ch
anne
l
Updrift Shoal
Mai
n Eb
b Ch
anne
l
Dist
al
Lobe
Downdrift Attachment
Flood Marginal Channel
In the long term:
These areas will be deeper
BSP MORPHOLOGY
Existing Conditions
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
% Increase in wave energy here and here
% Decrease in wave energy here and here
Results from the CMS morphologic model yields No indication of increased erosion over the Existing Condition at Siesta Key
HOW WILL THIS AFFECT SIESTA KEY?
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Navigable water greater than 6m depth without project
Navigable water greater than 6m depth with project
No significant difference in navigable water depths without and with project
EFFECT ON CURRENT NAVIGATION?
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PROJECT PLAN – SOUTHERN GROINS
GENERAL QUESTIONS?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
SOUTH LIDO KEY GROINS
What are the plans for the groins?
• How long are they?• How much space is
between them?• How big are they?• Can I walk along the
beach?• Can I swim in the surf
zone?• Can I navigate past them?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
350’ 500’
460’
600’800’
2004 Present Day
HOW LONG? HOW MUCH SPACE IN BETWEEN ?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
HOW BIG ARE THEY?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
CAN I WALK ALONG THE BEACH?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
CAN I SWIM IN THE SURF ZONE? CAN I NAVIGATE PAST THEM?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville DistrictBUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
PROJECT PLAN – SOUTHERN GROINS
HYPOTHETICAL QUESTIONS?
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
What if the groins do not work?
What is the effect on Lido Beach?
What is the effect on Siesta Key?
How will the groins affect the ebb shoal in BSP?
Why nourish the beach if we are installing structures?
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Downdrift Effects
Sediment Bypassing to BSP Ebb Shoal
Groins are constructed to anchor the nourishment template – not to intercept Sediment at the expense of downdrift beaches or ebb shoal morphology!
WHAT IS THE EFFECT ON LIDO KEY?WHAT IS THE EFFECT ON SIESTA KEY?
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How will the groins affect the ebb shoal in BSP?
Downdrift Effects
Sediment Bypassing to BSP Ebb Shoal
Adequate sediment bypassing at the seaward end of the groin structures will deter the growth of a crescentic shoreline . Adequate bypassing to the Ebb Shoal ensures that BSP will maintain its morphology – seen by lack of erosion in the shoal itself
BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District
Why nourish the beach if we are installing structures?
Groins are constructed to anchor the nourishment template – not to intercept sediment at the expense of downdrift beaches or ebb shoal morphology!
Groin construction without an associated nourishment project can lead to downdrift erosion and a lack of sediment supply to downdrift systems
The groins are designed to work with the nourishment design template – should the beach erode shoreward of the design template, Emergency measures are implemented
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Groins – Anchor the Nourishment
Beach
Nourishment
Retain
1981
1983
1986
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Questions/Discussions
Milan A. Mora, P.E.Project Manager
Jacksonville DistrictWater Resources Branch701 San Marco Boulevard
Jacksonville, FL 32207904-232-1454
LIDO KEY SPP