SARASOTA COUNTY – LIDO KEY HURRICANE & STORM DAMAGE REDUCTION PROJECT

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


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.


2

1971

2006

1986


OVERVIEW – PROJECT FEATURES


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


PROJECT PLAN


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


PLACEMENT – LIDO KEY


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


SOURCE – BSP BORROW AREAS


6

D2

C

B


RETAIN – SOUTHERN GROINS


7

Retain

Beach

Nourishmen

t

BUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville DistrictBUILDING STRONG® US ARMY CORPS OF ENGINEERS | Jacksonville District

PROJECT PLAN – BORROW AREA QUESTIONS?


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?


ALT D2, C, B – 1.7 MCY BORROW AREA FOOTPRINTS

D2

C

B


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


% 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?


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?


PROJECT PLAN – SOUTHERN GROINS

GENERAL QUESTIONS?


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?


350’ 500’

460’

600’800’

2004 Present Day

HOW LONG? HOW MUCH SPACE IN BETWEEN ?


HOW BIG ARE THEY?


CAN I WALK ALONG THE BEACH?


CAN I SWIM IN THE SURF ZONE? CAN I NAVIGATE PAST THEM?


PROJECT PLAN – SOUTHERN GROINS

HYPOTHETICAL QUESTIONS?


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?


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?


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


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


Groins – Anchor the Nourishment

Beach

Nourishment

Retain

1981

1983

1986


Questions/Discussions

Milan A. Mora, P.E.Project Manager

Jacksonville DistrictWater Resources Branch701 San Marco Boulevard

Jacksonville, FL 32207904-232-1454

[email protected]

LIDO KEY SPP

SARASOTA COUNTY – LIDO KEY HURRICANE & STORM DAMAGE REDUCTION PROJECT

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