evaluating the shoreline protection functioning of three divergent constructed...

Evaluating the Shoreline Protection

Functioning of Three Divergent Constructed

Oyster Reef Structures in Terrebonne Bay,

Louisiana

Glen Curole

Coastal Resources Scientist-CPRA

&

Dr. Earl Melancon

Professor-Nicholls State University

3rd Biennial State of Coast Conference

March 18-20, 2014

Ernest N. Morial Convention Center

New Orleans, LA

committed to our coast committed to our coast

Coastal Protection and Restoration Authority of Louisiana

• 8 YEAR CWPPRA DEMONSTRATION PROJECT

• SPONSERED by USFWS & CPRA

• CURRENTLY in YEAR 6 (2014)

• PLACED on 10th CWPPRA PPL in MAY 2000

• LAKE BARRE SHORELINES SELECTED

• HIGH OYSTER PRODUCTIVITY

• HIGH RATES of SHORELINE EROSION

• E&D AUTHORIZED in JAN 2001

• DESIGNED to CONSTRUCT 6 STRUCTURE TYPES at 3 REACHES

• EACH STRUCTURE 91.4 METERS (300 FEET) in LENGTH

• 5 REACHES INVESTIGATED

• REACHES A, B, & E SELECTED

• CONSTRUCTION APPROVED in AUG 2003

TERREBONNE BAY SHORE PROTECTION DEMONSTRATION

PROJECT (TE-45) TIMELINE & HISTORY


• TE-45 PROJECT MODIFIED & RE-BID in JUN 2007

• 3 STRUCTURE TYPES ELIMINATED from DESIGN

• GABION MAT, A-JACK, & REEFBLK STRUCTURES

SELECTED

• CONSTRUCTION BUDGET INCREASED

• REACH B RELOCATED

• CONTRACTOR SELECTED

• CONSTRUCTION

• BEGAN on SEP 13, 2007

• ENDED on DEC 19, 2007

• COST $1,653,301

• TE-45 PROJECT EVALUATED the 3 STRUCTURE TYPES for:

• EFFECTIVENESS in REDUCING SHORELINE EROSION

• ABILITY to DEVELOP & SUSTAIN OYSTER REEF HABITAT

OYSTER HABITAT ZONES IN BARATARIA-TERREBONNE ESTUARIES


Primary Fishery Habitat Zone

Primary SUBTIDAL Habitat Zone

Place Title of Slide Here Secondary Title



Public Hearing New Orleans




Cost per Linear Foot = $460


SHORELINE CHANGE 1998-2012


-8.0

-7.0

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

A-jack Gabion Mat ReefBlk Reference Area

Sho

relin

e C

ha

ng

e (

m/y

r)

Treatments

1998 – 2012 SHORELINE CHANGE BY TREATMENT

Pre-construction 1998-2005 Post-construction 2007-2008

Post-construction 2008-2010 Post-construction 2010-2012

*Different Letters Denote Significant Differences (P < 0.05)

A C B


-12.0

-11.0

-10.0

-9.0

-8.0

-7.0

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

Reach A Reach B Reach E Reference A Reference B Reference E

Sho

relin

e C

ha

ng

e (

m/y

r)

Reaches

1998 – 2012 SHORELINE CHANGE BY REACH

Pre-construction 1998-2005 Post-construction 2007-2008

Post-construction 2008-2010 Post-construction 2010-2012

*Different Letters Denote Significant Differences (P < 0.05)

A C A B B



Flanking Erosion

Gabion Mats

REACH E GABION MATS FLANKING EROSION

Flanking Erosion

Gabion Mats

qReach E

Reference Area


ELEVATION CHANGE 2008-2011


Reach Treatment

Windward Position Volume Change 2008-2011 (m3)

Leeward Position Volume Change 2008-2011 (m3)

A A-Jack -60 -18 B A-Jack -54 -10 E A-Jack -49 -12

A Gabion Mat -76 0.93 B Gabion Mat -50 3 E Gabion Mat -112 8

A ReefBlks -70 -8 B ReefBlks -21 15

E ReefBlks -76 -21

A Reference -46 -97

B Reference -18 -11

E Reference -97 -64

Mean - -61±8 -18±9

STRUCTURE SEDIMENTATION 2008-2011


STRUCTURE SETTLEMENT 2008-2011

Reach Treatment Structure Elevation 2008 NAVD 88 (m)

Structure Elevation 2011 NAVD 88 (m)

Structure Settlement 2008-2011 (m)

A A-Jack 0.28 0.23 -0.05

B A-Jack 0.28 0.24 -0.04 E A-Jack 0.22 0.13 -0.09

A Gabion Mat 0.29 0.23 -0.07

B Gabion Mat 0.35 0.29 -0.06

E Gabion Mat 0.25 0.19 -0.07

A ReefBlks 0.30 0.28 -0.01

B ReefBlks 0.40 0.32 -0.09 E ReefBlks 0.22 0.07 -0.14

Mean - 0.29±0.02 0.22±0.03 -0.07±0.01


• The pre-construction TE-45 shorelines transgressed at high and variable

rates.

• All the structures and all the Reaches experienced reductions in shoreline

erosion rates during the post-construction assessments.

• To date the Gabion Mat treatment is clearly the most effective shoreline

protection structure at the TE-45 Reaches.

• The post-construction shoreline transgressions behind the ReefBlk and A-

Jack treatments were temporally similar.

• The post-construction reference area Reaches have continued to erode at

differential rates.

• Additional temporal data is needed to determine if the low erosion rates

behind these structures are sustainable.

SHORELINE EROSION SUMMARY


• All shoreline Reaches recorded volume losses during both pre- and post-

construction intervals.

• The Reach A and E reference areas had substantial volume reductions for

areas of less than one acre because of erosion along their shorelines.

• The TE-45 structures and reference areas sustained post-construction

sedimentation deficits primarily in the windward position.

• The Reach E structures were established at a slightly lower vertical

position than the Reach A and B structures.

• Currently, the Reach E ReefBlk and A-Jack structures have the lowest

vertical profile.

ELEVATION SUMMARY


ACKNOWLEDGEMENTS

Dr. Quenton Fontenot Tori Bacheler

Stephen Odekirk Maggie Bruce Justin Sancho

Natasha Dufrene Caleb Bourgeois

Kristin Buter Mark Linson

Dan O’Malley Samantha Ordoyne

Daniel Dearmond Dain Gillen

Maury Chatellier Ralph Libersat

Todd Folse Darin Lee

Robert Dubois Ronnie Paille

Martha Segura

evaluating the shoreline protection functioning of three divergent constructed...

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