Rebuilding an Island to Restore Bird Nesting Habitat for ...

Rebuilding an Island to Restore Bird Nesting Habitat for Species Injured by the

DWH Spill

NRDAR

Assessment Injury Determination Settlement Restoration

DWH Early Restoration

NRDAR Injured species’ needs assessment

Target areas

Target actions

Selection and Implementation

: Bird Restoration Planning

Breton Island: 1989

Breton Island: 2012

Major hurricanes impacting Breton since 1989 • Andrew 1994 • Georges 1998 • Ivan 2004 • Katrina 2005 • Rita 2005 • Gustav 2008 • Ike 2008

Loss of island area

~27 acres/yr loss

Island retreat 2014 lidar shoreline overlain on 2008 DOQQ imagery

~28 ft/yr past century 750 ft after Hurricane Katrina

Seafloor change

Accretion - Erosion 1920 to 2007

Breton Is.

erosion

erosion

deposition

deposition

MRGO ship channel

Data from the Louisiana Barrier Island Comprehensive Monitoring Project

Identifying resources for barrier island restoration

Chandeleur Is.

2011 oil-spill mitigation sand berm

Dredge pit

• Sufficient quantities of compatible sediments must be identified

• The sediments must be in close proximity to the restoration site

• The borrow site cannot be too close to the island platform to affect wave dynamics and sediment processes

Beach restoration

Dune restoration

Marsh restoration

Conceptual construction design

• Not a lot of sandy material off of the island platform

Identifying resources for barrier island restoration

• Regardless of source modeling is necessary to evaluate impact of sediment removal on wave climate at the island

A. Buried distributary channels

B. Offshore shoals

C. Terminal spit deposits similar to Hewes Point

• An estimated 3 million cubic yards of sand is needed

A. MRGO and natural inlet Ebb-tidal delta

• Potential sites indclude:

Identifying resources for barrier island restoration (potential offshore shoal deposits)

Offshore shoal

NOAA Bathymetry (~1922)

Breton Island

1987 vibracore

Identifying resources for barrier island restoration (potential offshore shoal deposits)

Offshore shoal

NOAA Bathymetry (~1922) Pre – 1778 Nautical Chart

Breton Is. Breton Island

• Does Breton Island predate the Chandeleur Islands? • What are the geologic and morphologic relationships between the two systems?

Identifying resources for barrier island restoration (potential offshore shoal deposits)

• Offshore geophysical investigation (August, 2014) Swath bathymetry Sidescan soar High-resolution sub-bottom seismic profiling • Ground-truth with 20-foot sediment cores (September / October, 2014)

Example seismic subbottom profile

Proposed survey tracklines

Modeling impact of dredge pits on wave refraction

Dredge pit scenarios Wave refraction modeling (SWAN)

Geophysical characterization of the barrier island system

• Nearshore investigation (July, 2014) Swath bathymetry (> 1m wd) Single-beam bathymetry High-resolution sub-bottom seismic profiling Sediment grab samples • Provide updated/baseline elevation data for models and restoration design. • Sediment budget and processes • Comparison to historical (bathymetric change, sediment change)

Breton Is.

Gosier shoal

Curlew shoal

“To watch the terns flashing in a shifting maze above the beach…or to see a file of pelicans winging their way home-ward

across the afterglow of the sunset, is like a gallery of old masters…their loss would be like the loss of artists for all time.”

-Theodore Roosevelt, 1915, Breton Island, LA