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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
Coastal Protection and Restoration Authority of Louisiana
• 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
Coastal Protection and Restoration Authority of Louisiana
Primary Fishery Habitat Zone
Primary SUBTIDAL Habitat Zone
Coastal Protection and Restoration Authority of Louisiana
Coastal Protection and Restoration Authority of Louisiana
Place Title of Slide Here Secondary Title
Coastal Protection and Restoration Authority of Louisiana
Place Title of Slide Here Secondary Title
Public Hearing New Orleans
Coastal Protection and Restoration Authority of Louisiana
Place Title of Slide Here Secondary Title
Coastal Protection and Restoration Authority of Louisiana
Cost per Linear Foot = $460
Place Title of Slide Here Secondary Title
Public Hearing New Orleans
Coastal Protection and Restoration Authority of Louisiana
Place Title of Slide Here Secondary Title
Coastal Protection and Restoration Authority of Louisiana
Place Title of Slide Here Secondary Title
Public Hearing New Orleans
Coastal Protection and Restoration Authority of Louisiana
Coastal Protection and Restoration Authority of Louisiana
SHORELINE CHANGE 1998-2012
Coastal Protection and Restoration Authority of Louisiana
-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
Coastal Protection and Restoration Authority of Louisiana
-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
Public Hearing New Orleans
Coastal Protection and Restoration Authority of Louisiana
Flanking Erosion
Gabion Mats
REACH E GABION MATS FLANKING EROSION
Flanking Erosion
Gabion Mats
qReach E
Reference Area
Coastal Protection and Restoration Authority of Louisiana
ELEVATION CHANGE 2008-2011
Coastal Protection and Restoration Authority of Louisiana
Coastal Protection and Restoration Authority of Louisiana
Coastal Protection and Restoration Authority of Louisiana
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
Coastal Protection and Restoration Authority of Louisiana
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
Coastal Protection and Restoration Authority of Louisiana
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
Coastal Protection and Restoration Authority of Louisiana
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
Coastal Protection and Restoration Authority of Louisiana
• 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
Coastal Protection and Restoration Authority of Louisiana
• 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
Coastal Protection and Restoration Authority of Louisiana
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