Louisiana Barrier Island Comprehensive Monitoring 

(BICM) Program Summary Report: Data and Analyses 

2006 through 2010

By Jack L. Kindinger, Noreen A. Buster, James G. Flocks, Julie C. Bernier, and Mark A. Kulp

Open-File Report 2013–1083

U.S. Department of the Interior

U.S. Geological Survey
Cover: The eight BICM study regions in Louisiana displayed with a 2008 NASA Terra satellite image after 

Hurricane Ike passed inland.
Louisiana Barrier Island Comprehensive Monitoring 

(BICM) Program Summary Report: Data and Analyses 

2006 through 2010

By Jack L. Kindinger, Noreen A. Buster, James G. Flocks, Julie C. Bernier, and Mark A. Kulp

Open-File Report 2013–1083

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

Ken Salazar, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia 2013

For product and ordering information:

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its natural and living resources, natural hazards, and the environment:

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Suggested citation:

Kindinger, J.L., Buster, N.A., Flocks, J.G., Bernier, J.C., and Kulp, M.A., 2013, Louisiana Barrier Island 

Comprehensive Monitoring (BICM) Program Summary Report: Data and Analyses 2006 through 2010: U.S. 

Geological Survey Open-File Report 2013–1083, 86 p.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Acknowledgments..................................................................................................................................................................................x

Primary documents and contributing authors in support of this report.............................................................................................x

Executive Summary................................................................................................................................................................................1

Introduction............................................................................................................................................................................................1

Study Area..........................................................................................................................................................................................2

Monitoring the Louisiana Coast.........................................................................................................................................................4

Review of Available Data Prior to BICM Implementation .................................................................................................................7

Six BICM Volumes – Data Reports ....................................................................................................................................................8

Volume 1: Barrier-Shoreline Post-Storm Assessment ...................................................................................................................8

Volume 2: Shoreline Changes and Barrier-Island Land Loss, 1800s to 2005 ................................................................................8

Volume 3: Bathymetry and Historical Seafloor Change, 1869–2007 ...........................................................................................9

Volume 4: Accuracy of EAARL Lidar Ground Elevations Using a Bare-Earth Algorithm in Marsh and Beach Grasses on the 

Chandeleur Islands, Louisiana ....................................................................................................................................12

Volume 5: Chenier Plain, South-Central Louisiana, and Chandeleur Islands Habitat Mapping and Change Analysis 1996 to 

2005 ............................................................................................................................................................................12

Volume 6: Characterization of Louisiana Coastal Sediment Samples: Back-Barrier through Offshore Samples of the Chenier 

Plain, South-Central Barrier-Island Systems, and Chandeleur Islands......................................................................12

Regional Discussions...........................................................................................................................................................................17

Lakes Region - Lake Pontchartrain Basin ........................................................................................................................................18

History of Topographic and Bathymetric Changes .................................................................................................................20

Habitat Change .......................................................................................................................................................................20

Impacts of Storms...................................................................................................................................................................20

Mississippi River Delta Plain ...........................................................................................................................................................22

Chandeleur Islands ......................................................................................................................................................................22

History of Topographic and Bathymetric Change ...................................................................................................................23

Habitat Change .......................................................................................................................................................................25

Impacts of Storms...................................................................................................................................................................25

Modern Delta, Lafourche, and Teche Deltas...............................................................................................................................28

History of Topographic and Bathymetric Change ...................................................................................................................30

Habitat Change ......................................................................................................................................................................33

Impacts of Storms...................................................................................................................................................................33

Acadiana Bays..................................................................................................................................................................................37

History of Topographic and Bathymetric Changes .................................................................................................................38

Habitat Changes and Impacts of Storms................................................................................................................................40

Chenier Plain ...................................................................................................................................................................................40

History of Topographic and Bathymetric Changes .................................................................................................................41

Habitat Change .......................................................................................................................................................................43

Impacts of Storms...................................................................................................................................................................44

Discussion of Louisiana Coast-Wide and Topical Themes..................................................................................................................45
iv

THEME 1: Barrier-Shoreline Evolution in a Regime of Rapid Relative Sea-Level Rise and Interior-Wetland Loss........................45

Physical Coastal Processes .........................................................................................................................................................46

Coastal-Sediment Budget ............................................................................................................................................................46

THEME 2: Hurricane Impact to the Chandeleur Islands during the Period 1855 to 2005 and the Likelihood of Island Recovery.47

Impacts of Hurricanes and Implications for Management ..........................................................................................................50

THEME 3: Impact of Tropical Storms on Barrier-Shoreline Elevations and the Response of Island Renourishment to Storms ...54

THEME 4: Barataria Bay Tidal-Inlet Management Considerations..................................................................................................60

Methods 61

Tidal-Inlet Morphological and Hydrodynamic Evolution..............................................................................................................61

Barataria Pass.........................................................................................................................................................................63

Quatre Bayou Pass..................................................................................................................................................................65

Pass Abel ................................................................................................................................................................................67

Caminada Pass........................................................................................................................................................................68

Tidal-Range Evolution ..................................................................................................................................................................68

Conclusions: Impacting Wetlands and Inlets in Central Louisiana .............................................................................................70

THEME 5: Habitat Changes Related to Long-Term Relative Sea-Level-Driven Erosion and Short-Term Storm-Driven Erosion.....71

Pontchartrain Basin......................................................................................................................................................................71

Mississippi River Delta Plain .......................................................................................................................................................71

Chandeleur Islands (Breton Island to Hewes Point) ...............................................................................................................71

Modern Delta (Chaland Headland, Bay Joe Wise, Shell Island, Scofield, and Sandy Point) ...............................................71

Lafourche Delta (Timbalier Island, East Timbalier Island, the Caminada Headland, Grand Isle, Grand Terre Island, and East 

Grand Terre Island) ...........................................................................................................................................................71

Teche Delta (Isles Dernieres Chain from Raccoon Point to Wine Island Pass)......................................................................72

Acadiana Bay ...............................................................................................................................................................................72

Chenier Plain (Ocean View to Hackberry Beaches)......................................................................................................................72

THEME 6: Future Goals of the BICM Program .................................................................................................................................72

Future BICM Monitoring ..............................................................................................................................................................73

Semi-Decadal and Annual-Scale Monitoring of BICM Regions.............................................................................................73

Proposed Data Collection .......................................................................................................................................................73

Technology Advances .............................................................................................................................................................74

Standardization of Methods and Quality Control...................................................................................................................74

External Considerations...............................................................................................................................................................74

Establishment of Hydrodynamic Monitoring Stations............................................................................................................74

Development of Barrier-Island Value Assessment Model .....................................................................................................75

Data Management and User Tools.........................................................................................................................................75

References...........................................................................................................................................................................................76
v

Figures

1. The original four coastal Louisiana shoreline regions based on geologic and physiographic setting (Pontchartrain Basin, 

Mississippi River Delta Plain, Acadiana Bays, and Chenier Plain) with the eight regions used in BICM analyses (the 

Lakes Region; Chandeleur Islands; Modern, Lafourche, and Teche Deltas; Acadiana Bays; and the eastern and western 

Chenier Plain). ............................................................................................................................................................................3

2. Data-coverage map for each BICM task: barrier-shoreline post-storm assessment, historical shoreline changes, bathymetric 

and historical seafloor change, lidar surveys for the Louisiana coast, habitat mapping and change analysis, and 

characterization of coastal surface-sediment samples. ............................................................................................................5

3. Example of Volume 1 Barrier-Shoreline Post-Storm Assessment aerial time-series photo pair of Trinity Island for 2005 and 2007.. .9

4. Location map depicting the 80 different reaches of shoreline designated during the BICM program to analyze shoreline change

for coastal Louisiana. ..............................................................................................................................................................10

5. Historical shoreline positions for the Isle Dernieres from 1887 to 2005 with change maps for time periods: 1887–1934, 1934–

1996, 1996–2004, and 2004–2005. .........................................................................................................................................11

6. Seafloor-change maps created by digitizing historical bathymetry and collecting data during the BICM program for the 

northern Chandeleur Islands. ..................................................................................................................................................13

7. A time-series depiction of lidar data collected for the Chandeleur Islands showing land loss along the island chain over an

approximately 5-year period from October 2002, to September 2005—2 days post-Hurricane Katrina, and to June 

2007—22 months post-Hurricane Katrina. .............................................................................................................................14

8. Habitat-change map (1996 to 2005) for Timbalier Island, Lafourche Delta. .......................................................................................15

9. Map showing locations and grain sizes of surficial-sediment samples collected for the BICM program along one stretch of the

modern Mississippi River Delta. ..............................................................................................................................................16

10. Distribution and chronology of Holocene Mississippi River delta complexes. ..................................................................................17

11. Map of the Pontchartrain Basin showing the river basins that drain into Lakes Pontchartrain, Maurepas, and Borgne. ................18

12. Holocene evolutionary model of Lake Pontchartrain. .........................................................................................................................19

13. Map showing shoreline change around Lake Pontchartrain, Lake Borgne, and Lake Maurepaus between 1855 and 2005. ..........21

14. Aerial photos taken of the coastline within the Pontchartrain Lake Basin in 2006 as part of the BICM program. ..........................21

15. Bathymetric map (2006–2007) using BICM data collected in the nearshore waters around the Breton National Wildlife 

Refuge area..............................................................................................................................................................................22

16. Bathymetric-data coverage for the northern Chandeleur Islands. .....................................................................................................24

17. Sediment isopach of Hewes Point terminal spit; deposit (purple and red) is approximately 27 km2 (10 mi2), 8 m (26.3 ft) thick, 

and is composed of 97 percent well-sorted fine sand. ...........................................................................................................25

18A. Habitat-change map of Breton Island (1998 to 2002). ....................................................................................................................26

18B. Habitat-change map of the Chandeleur Islands (2004 to 2005)—note the large areas of habitat change to water after 

passage of Hurricane Katrina. . ..............................................................................................................................................27

19. Cumulative percentage histograms of habitat change in analysis areas during the four analyses time periods. ............................28

20. Oblique aerial-photo time series of a portion of the Chandeleur Islands. ........................................................................................29

21. Bathymetry collected during the BICM project in 2006 along Caminada Headland, Grand Isle, and Grand Terre. Barrier extents 

are indicated by green with shorelines derived from thematic classifications produced from image datasets and GIS 

editing. ....................................................................................................................................................................................31
vi

22. Seafloor-change map of the Raccoon Point to Sandy Point area from the 1880s to 2005. ..............................................................31

23. Historical (from 1884 to 2005) shoreline-change time series of Timbalier Island, Caminada Headland, and Grand Isle using 

shoreline data compiled from BICM Volume 2. ......................................................................................................................32

24. Habitat-change classification for Whiskey Island, Teche Delta between the years 1996 and 2005 showing that during the 

passage of Hurricanes Katrina and Rita, significant washover occurred on Whiskey Island, increasing the acreages of 

beach and intertidal-flat habitat. .............................................................................................................................................34

25. Cumulative percentage histograms of habitat change in analysis areas during the four analyses time periods. ............................35

26. Caminada Headland shoreface seafloor-change map, 2005 to 2006. ...............................................................................................36

27. Example of Volume 1 Barrier-Shoreline Post-Storm Assessment aerial time-series photo pair of Elmers Island for 2005 and 

2007. ........................................................................................................................................................................................37

28. Vibracore transect across Atchafalaya Bay, to the west of the present navigation channel. The cross section reflects the 

transition from a brackish-marsh environment into estuarine, or bay, and then modern fluvial delta. .................................38

29. Shoreline-change map (1800s to 2005) of the Morgan City quadrangle. USGS Quadrangle in the Acadiana Bays region 

analyzed during BICM project. .................................................................................................................................................39

30. Oblique aerial photos of the Atchafalya Delta, 2006, and Marsh Island, 2005, shorelines taken as part of the BICM program. ...39

31. Historical (1855 to 2005) shoreline-change rates in meters per year along the Chenier Plain coastline. .......................................40

32. Western Chenier shoreline and 2007 bathymetric map using BICM-program data. .........................................................................41

33. Western Chenier historical seafloor-change map from the 1880s to 1920s using digitized H- and T-sheets from the U.S. 

Coastal and Geodetic Survey and seafloor change methods and uncertainty analysis. .......................................................42

34. Western Chenier historical seafloor-change map from the 1920s to 2007 using digitized H- and T-sheets from the U.S. Coast 

and Geodetic Survey and seafloor change methods and uncertainty analysis. ....................................................................42

35. BICM habitat-change map (1998 to 2002) for Holly Beach along the western Chenier Plain. .........................................................43

36. Oblique aerial time-series photo pair of Johnson’s Bayou shoreline for the years 2005 and 2006. ................................................44

37. Southern coastal Louisiana land-loss change analysis, 1956 to 2004. .............................................................................................45

38. Location map showing the Chandeleur Islands relative to other physiographic features. ...............................................................47

39. Shoreline-retreat and land-area change for the Chandeleur Islands between 1855 and 2005. .......................................................48

40. View to the south of the seafloor surfaces of the Chandeleur Islands of the 1870s versus those of 2006. ....................................50

41. Maps of the Chandeleur Islands before and after Hurricane Katrina (August 2005) based on lidar data. .......................................51

42. Changes of the shoreline and width of the Chandeleur Islands from lidar surveys before Hurricane Katrina (August 2005), 2 

days after the storm, and 22 months after the storm. ...........................................................................................................52

43. Conceptual model demonstrating how a barrier-island management-restoration approach may employ natural physical 

processes to extend the life span of the Chandeleur Islands. ................................................................................................53

44. Hurricane and tropical storm tracks that impacted the Louisiana coast over the 50-year time period between 1957 and 2008. ...54

45. Erosion of a barrier island is a function of elevation compared to total water run-up, for example, surge+setup+runup on the 

beach. ......................................................................................................................................................................................55

46. Peak elevations (Dhigh) determined every 20 m (67 ft) along the length of the Chandeleur Islands using lidar data processed 

for first return. .........................................................................................................................................................................56
vii

47. Changes to a 2.5-km (1.6-mi) reach of the Chandeleur Islands showing persistent erosion and landward retreat during the 22

months after landfall by Hurricane Katrina (modified from Sallenger and others, 2009). ....................................................57

48. Bare-earth peak elevations (Dhigh), maximum-of-the-maximum storm-surge elevations for different categories (“cat”) 

of hurricanes, and storm surge for Hurricane Katrina computed by using the Sea, Lake, and Overland Surges from 

Hurricanes (SLOSH) model. (A) 2 days after. (B) 22 months after. (C) Change in Dhigh between 2 days after and 22 

months after (Sallenger and others, 2009). .............................................................................................................................58

49. Types of erosional and depositional features produced by extreme storms include (A) dune erosion, (B) channel incision, (C) 

washout, (D) washover terrace, (E) perched fan, (F) sheetwash lineations (Morton and Sallenger, 2003). ..........................59

50. Hydrodynamic instrument deployment locations and acoustic Doppler current profiler (ADCP) survey tracklines (Howes, 2009). .60

51. (A) High resolution tidal inlet cross sections from single beam soundings (Howes, 2009) (* denotes transects across the inlets 

were taken along the same line each, with the exception of Quatre Bayou, where they were offset by 50 meters). (B) 

Barataria Pass shows an increase in inlet hydraulic radius with increased cross-sectional area compared to the other 

three passes. It is also the only inlet that did not develop an inlet platform even with increased cross-sectional area 

(Howes, 2009). .........................................................................................................................................................................62

52. Graph showing the relation between peak ebb discharge and tidal range for the four inlets (Barataria Pass, Quatre Bayou, 

Caminada Pass, and Pass Abel)...............................................................................................................................................63

53. Graph showing inlet cross-sectional area since 1888. ......................................................................................................................64

54. The morphological evolution of Barataria Pass, including (A) the extension of the inlet channel as defined by the 5m contour, 

(B) the inlet throat defined as greater than 10 m deep, (C) cross sections across the inlet throat, and (D) the change in 

hydraulic and dynamic radius (dynamic radius is a measure that weights the depth to the power of 5/3); the dynamicradius measure shows the same general trend as hydraulic radius (Howes, 2009). .............................................................64

55. Morphological evolution at Quatre Bayou Pass, including (A) the extension of the inlet channel, (B) the inlet throat defined as 

greater than 10 m (32.8 ft) deep, (C) cross sections across the inlet throat, and (D) the change in hydraulic and dynamic 

radius. ......................................................................................................................................................................................65

56. Morphological evolution at Pass Abel, including (A) the extension of the inlet channel, (B) there is no panel for B because the 

inlet throat was defined as greater than 10 m, and this inlet did not achieve that depth, (C) cross sections across the 

inlet throat, and (D) the change in hydraulic and dynamic radius. .........................................................................................66

57. Morphologic evolution at Caminada Pass, including (A) the extension of the inlet channel, (B) there is no panel for B because 

the inlet throat was defined as greater than 10 m, and this inlet did not achieve that depth, (C) cross sections across 

the inlet throat, and (D) the change in hydraulic and dynamic radius. ...................................................................................67

58. (A) Three complete cycles of the 18.6-year nodal tidal cycle. (B) The residual tidal signal after the 18.6-year cycle is removed, 

showing an increase in tidal range over approximately the past 50 years; the rate change increased between 1951 and 

the early 1970s (Howes, 2009). ...............................................................................................................................................68

59. (A) Relative sea-level rise at Grand Isle, 1947–2006. (B) Hydraulic radius at Barataria Pass (blue points) and the increase in 

annual tidal range at Grand Isle relative to tidal range in 1951, as shown in 59 (Howes, 2009). .........................................69
viii

Tables

Table 1. Locations and amount of 2006–2010 BICM data collected as numbers of photos, images, mosaics, line-kilometers, 

minutes of video, and number of samples collected/ analyzed by scientists. .........................................................................6
ix

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

mile, nautical (nmi) 1.852 kilometer (km)

Area

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2

)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 
x

Acknowledgments

This report is the cumulative effort of more than 50 contributors who collected and processed data, conducted 

analyses and interpretations, and wrote data reports. We could not have completed this report without the managerial 

support and funding from Alyssa Dausman and Jess Weaver of the U.S. Geological Survey Southeast Region and Richard 

Poore of the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center. We appreciate the invaluable 

discussions about report approach and structure with Darin Lee, Syed Khalil, and Richard Raynie of the Coastal 

Restoration and Protection Authority of Louisiana. We thank Nick Howes for leading the effort to rewrite Theme 4, 

Dallon Weathers (University of New Orleans) for making data and figures available, and also Betsy Boynton’s help with 

U.S. Geological Survey publication layout and compliance. This report was improved considerably by the comments and 

suggestions of Syed Khalil, Darin Lee, Barbara Lidz, Kay Naugle, and Abby Sallenger.

Primary documents and contributing authors in support of this report

Volume1: Barrier Shoreline Post-Storm Assessment

Part 1: 2005 Post Hurricanes Katrina and Rita Photography

Westphal, K.A.

Part 2: 2006/2007 Aerial Survey Photography 

Westphal, K.A. and Penland S.

Part 3: 2005-2007 Photo-Pairs

Westphal, K.A.

Part 4: Historic Photo-Pairs/Time Series

Westphal, K.A.

Part 5: 2006/2007 Aerial Video Survey

Westphal, K.A., Penland S., and Weathers, D.

Volume 2: Shoreline Changes and Barrier Island Land Loss 1800’s-2005

Appendix A: Tide Gauge Stations, Locations, and Stage Data

Appendix B: NOAA Coastal Survey Maps Used in Historical Analysis

Appendix C: Area Change Graphs, Change Rate Graphs, 11x17 Maps and Data DVD’s and CD’s

Martinez, L., O’Brien, S., Bethel, M., Penland, S., and Kulp, M.

Volume 3: Bathymetry and Historical Seafloor Change 1869-2007 

Part 1: South-Central Louisiana and Northern Chandeleur Islands, Bathymetry Methods and Uncertainty 

Analysis

Part 2: South Central Louisiana and Northern Chandeleur Islands, Bathymetry Maps
xi

Part 3: Southern Chandeleur Islands and Western Chenier Beaches, Bathymetry Maps

Miner M.D., Kulp M., Flocks J., Twichell D., Penland S., Weathers D., Martinez L., Motti J., DeWitt N., 

Reynolds B.J., Baldwin W., Danforth B., Worley C., Bergeron E., Ferina N., McCarty P., Brown, M., and 

Torres J. 

Part 4: Historical Seafloor Change Analysis

Miner, M., Weathers, D., Kulp, M., and Rafferty, R.

Volume 4: Louisiana Light Detection and Ranging Data (Lidar) 

Part 1: Lidar Systems and Data Processing Techniques

Hansen, M. and Howd, P.

Part 2: Lidar Flight Path Maps

Morgan, K.L.M

Part 3: Accuracy of EAARL Lidar Ground Elevations using a Bare-Earth Algorithm in Marsh and Beach 

Grasses on the Chandeleur Islands, Louisiana

Doran, K., Sallenger, A.H., Jr., Reynolds B.J., and Wright, C.W.

BICM Lidar Team: Sallenger, A.H., Jr., Wright, C.W., Kristy G., Sullivan, C., Howd, P., Doran, K., Morgan, 

K.L.M., Reynolds B.J., Hansen, M., and DeWitt, N.

Volume 5: Chenier Plain, South-Central Louisiana, and Chandeleur Islands, Habitat Mapping and 

Change Analysis 1996 to 2005

Part 1: Methods for Habitat Mapping and Change Analysis 1996 to 2005

Part 2: Habitat, Habitat Change, Land Loss, and Mosaic Maps

Part 3: Habitat Class Tables, Habitat Change Tables, and Final Statistics 1996 to 2005

Part 4: Results and Interpretations of the Habitat Mapping and Change Analysis 1996 to 2005

Fearnley, S., Brien, L., Martinez, L., Miner, M., Kulp, M. and Penland, S.

Volume 6: Parts A and B: Characterization of Louisiana Coastal Zone Sediment Samples: Backbarrier 

through offshore samples of the Chenier Plain, South Central Barrier Island Systems and Chandeleur 

Islands 

A: Kulp, M., Miner, M., Weathers, D., Motti, J., McCarty, P., Brown, M., Labold, J., and Boudreaux, A., 

B: Flocks J.G., and Taylor, C.

Theme 4 – Barataria Bay Tidal-Inlet Management Considerations

Howes, N.C., Z.J. Hughes, D.M. FitzGerald, and I.Y. Georgiou
xii

USGS Science Investigations Report 2009-5252: Sand Resources, Regional Geology, and Coastal 

Processes of the Chandeleur Islands Coastal System: an Evaluation of the Breton National Wildlife 

Refuge

Lavoie, D., editor

Contributing Authors (Alphabetical):

Baldwin, W., Bohling, C., Brien, L., Doran, K., Fearnley, S., Flocks, J., Georgiou, I. Y. Guy, K., Howd, P., Kulp, 

M., Martinez, L., Miner, M., Pendleton, E., Penland, S., Rogers, B., Sallenger, A.H., Jr., Sanford, J., 

Schindler, J. Twichell, D., Weathers, D., Williams, S.J. and Wright, C.W.
1

Louisiana Barrier Island Comprehensive Monitoring 

(BICM) Program Summary Report: Data and Analyses 2006 

through 2010

By Jack L. Kindinger1, Noreen A. Buster1, James G. Flocks1, Julie C. Bernier1, and Mark A. Kulp2

Executive Summary

The Barrier Island Comprehensive Monitoring (BICM) program was implemented under the Louisiana Coastal 

Area Science and Technology (LCA S&T) office as a component of the System Wide Assessment and Monitoring 

(SWAMP) program. The BICM project was developed by the State of Louisiana (Coastal Protection Restoration Authority 

[CPRA], formerly Department of Natural Resources [DNR]) to complement other Louisiana coastal monitoring programs 

such as the Coastwide Reference Monitoring System-Wetlands (CRMS-Wetlands) and was a collaborative research effort 

by CPRA, University of New Orleans (UNO), and the U.S. Geological Survey (USGS). The goal of the BICM program 

was to provide long-term data on the barrier islands of Louisiana that could be used to plan, design, evaluate, and maintain 

current and future barrier-island restoration projects. The BICM program used both historical and newly acquired (2006 

to 2010) data to assess and monitor changes in the aerial and subaqueous extent of islands, habitat types, sediment texture 

and geotechnical properties, environmental processes, and vegetation composition. BICM datasets included aerial still 

and video photography (multiple time series) for shoreline positions, habitat mapping, and land loss; light detection 

and ranging (lidar) surveys for topographic elevations; single-beam and swath bathymetry; and sediment grab samples. 

Products produced using BICM data and analyses included (but were not limited to) storm-impact assessments, rate of 

shoreline and bathymetric change, shoreline-erosion and accretion maps, high-resolution elevation maps, coastal-shoreline 

and barrier-island habitat-classification maps, and coastal surficial-sediment characterization maps.

Discussions in this report summarize the extensive data-collection efforts and present brief interpretive analyses 

for four coastal Louisiana geographic regions. In addition, several coastal-wide and topical themes were selected that 

integrate the data and analyses within a broader coastal context: (1) barrier-shoreline evolution driven by rapid relative 

sea-level rise (RSLR), (2) hurricane impacts to the Chandeleur Islands and likelihood of island recovery, (3) impact of 

tropical storms on barrier shorelines, (4) Barataria Bay tidal-inlet management, and (5) habitat changes related to RSLR. 

The final theme addresses potential future goals of the BICM program, including rotational annual to semi-decadal 

monitoring, proposed new-data collection, how to incorporate technological advances with previous data-collection and 

monitoring protocols, and standardizing methods and quality-control assessments for continued coastal monitoring and 

restoration. 

Introduction

The historical conversion of Louisiana’s wetlands, cheniers, and barrier islands to open water has been well 

documented in numerous studies and anecdotal observations (Williams and others, 1992; List and others, 1997; Morton 

and others, 2004; Georgiou and others, 2005; Penland and others, 2005; Barras and others, 2008; Blum and Roberts, 

2009; Fearnley, Miner, Kulp, FitzGerald, Flocks, and others, 2009; Couvillion and others, 2011; Linscombe and Hartley, 

2011). The Barrier Island Comprehensive Monitoring (BICM) program (2006 to 2010) was developed to provide baseline 

and monitoring data to support coastal-management decisions and adaptive-management planning. The BICM program 

was initiated under the Louisiana Coastal Area Science and Technology (LCA S&T) office as a component of the System 

Wide Assessment and Monitoring (SWAMP) program (USACE, 2004), planned by the Coastal Protection and Restoration 

1

U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida 33701, USA

2

Department of Earth and Environmental Sciences, University of New Orleans, New Orleans, Louisiana 70148, USA
2

Authority (CPRA, previously Louisiana Department of Natural Resources, LDNR) and implemented by a collaborative 

research effort by CPRA, University of New Orleans (UNO), and the U.S. Geological Survey (USGS). The BICM 

program study area encompassed barrier islands and sandy shorelines extending from the Chandeleur Islands west to the 

Chenier Plain of Louisiana (fig. 1). 

Five main objectives were originally identified:

(1) Determine the elevation, longevity, and conservation mass of the barrier islands;

(2) Determine major habitat types and the distribution and quantity of each habitat on the barrier islands over 

time;

(3) Determine geotechnical properties of sediments on the barrier islands and surrounding waters to access 

compatibility of the sediment and the sediment-dispersal pattern to evaluate fill performance;

(4) Relate available data on environmental forces that affect the ecology and morphology of the barrier islands to 

other BICM datasets; and

(5) Determine species composition and diversity of vegetation within major habitat types on the barrier islands.

As the project evolved, six data-collection tasks were designed to address: 

(1) Barrier-shoreline post-storm assessment (aerial videography and photography); 

(2) Historical shoreline changes and barrier-island land loss; 

(3) Bathymetry and historical seafloor change; 

(4) Light detection and ranging (lidar) surveys for the Louisiana coast’s sandy shorelines and barrier islands; 

(5) Habitat mapping and change analysis; and

(6) Characterization of Louisiana coastal surface-sediment samples. 

The methods, data, and results for each of these tasks were published in six data volumes that can be found at 

ftp://ftp.dnr.state.la.us/BICM and are summarized below. The Louisiana coast is a complex system that encompasses 

highly variable geomorphic and geologic settings. Regional discussions in this report describe the geologic history and 

processes that have shaped this coast and provide the relevant scientific context to understand and interpret the BICM 

data. Finally, data that were collected for the BICM program were incorporated into thematic discussions that focus on 

current scientific themes, such as understanding the impacts of sea-level rise and large-storm events on the coastal system. 

Study Area

The BICM program area encompasses the mainland shoreline of the southern Louisiana coast with special 

emphasis on the sandy beaches and barrier islands. For this study, the Louisiana coast was divided into four distinct 

regions based on geologic and physiographic setting: (1) the Pontchartrain Basin, (2) the Mississippi River Delta Plain, (3) 

the Acadiana Bays, and (4) the Chenier Plain. As the project developed, BICM further subdivided the coastline into eight 

regions: the Lakes Region; Chandeleur Islands; Modern, Lafourche, and Teche Deltas; Acadiana Bays; and the eastern and 

western Chenier Plain (fig. 1).

Not all BICM tasks included data collection across every region. Each task had different priorities and areas 

of concern. For example, shoreline-change analyses and lidar surveys were conducted along the entire coast, whereas 

bathymetric surveys focused on the barrier islands and sandy shorelines and were restricted to three primary geographical 

provinces: (1) parts of the eastern and western Chenier Plain; (2) from the western edge of Raccoon Island of the Isles 

Dernieres to Sandy Point along the Plaquemines Parish shoreline; and (3) the Chandeleur Islands. Aerial photography was 

BICM Program Summary Report: Data and Analyses 2006 through 2010
3

Study Area

Figure 1. The original four coastal Louisiana shoreline regions based on geologic and physiographic setting (Pontchartrain Basin, 

Mississippi River Delta Plain, Acadiana Bays, and Chenier Plain) with the eight regions used in BICM analyses (the Lakes Region; 

Chandeleur Islands; Modern, Lafourche, and Teche Deltas; Acadiana Bays; and the eastern and western Chenier Plain).
4

collected to support other tasks (for example, to identify shoreline positions for habitat mapping and land-loss analysis) 

and overlaps some or all of the geographic areas focused on by other tasks. Data coverage and general products for each of 

the six tasks and eight BICM regions are provided in figure 2 and table 1.

Although the objectives of BICM were delineated into six tasks, none of them stand alone as single entities. 

Instead, the tasks are interrelated, and data from one task were commonly incorporated into analyses within other tasks. 

For example, while the group tasked with collecting and acquiring historical and modern shorelines created their scientific 

products, the bathymetry group was producing similar products in many of the same areas. Identifying the shoreline 

location of a barrier island is a result of using the nearshore bathymetry, aerial photography, and lidar topography. These 

data are also used to map the geomorphology of the area. Islands consist of sandy sediments, and the nearshore sediment 

texture is a reflection of the source of sediments and the energy of the area. Nearshore surficial sediments were collected 

as a discrete task within BICM; however, maps depicting sediment properties along with bathymetry and shoreline 

position provide a basis for interpreting and understanding sediment transport, sediment-source location, sediment 

depositional sinks, and energy of the environment. Concurrently, another group was tasked with describing habitat 

classification, habitat change, and land-loss trends. Changes in nearshore bathymetry and barrier-island shape are driven 

by sediment deposition or erosion caused by nearshore currents and changes in energy, particularly by storms. As a result 

of these changes, some island habitats can change dramatically while other areas may remain stable over time. Time-series 

analysis of data collected for all tasks is imperative to monitor these dynamic environments. 

The 2006 to 2010 BICM projects primarily focused on the barrier-island environments along the Louisiana coast. 

The barrier islands extend for more than 150 kilometers (km; 93 miles, mi) from southern Terrebonne Parish east to the 

western Mississippi River Delta, and north from the eastern side of the delta to the Mississippi Sound. The majority of 

the data collected for the BICM program focused on these crucial barrier-island systems because these geologic features 

provide unique habitats and protect fragile estuaries and mainland environments from the full force of tropical storms and 

hurricanes. To adequately predict island response to storm events, sediment supply, and sea-level change, it is necessary 

to (1) understand historic shoreline positions and bathymetry; (2) establish baseline topography and bathymetry; and (3) 

characterize habitats and their distribution.

The geomorphology of Louisiana’s barrier islands is a complex arrangement of landscapes produced by fluvial 

processes and sea-level rise over the past 7,000 years. Currently, mainland and barrier-island configurations are shaped 

by eustatic sea-level rise, land subsidence, prevailing wave climate, and storm activity. Interactions among these dynamic 

processes, along with declining historical fluvial deposition, are forcing a redistribution of the antecedent topography 

to maintain equilibrium with the changing coastal environment. The resulting overall trend is net erosion and shoreline 

regression; however, variations in landform distribution, textural composition, and land subsidence create areas of 

localized deposition.

Monitoring barrier-island change requires repetitive surveys of the aerial dimensions of the islands as well as the 

subaerial nearshore and back-barrier environments. Topographic and bathymetric data provide an easy reference for how 

the system is changing. Imagery, lidar, and geophysical surveys are the primary tools currently used to gather detailed 

shoreline position, habitat, and subaerial extent of barrier islands. The results of the BICM program provide data for 

shoreline and seafloor-change analyses, identify “hotspot” areas that are especially sensitive or require additional research, 

and link the geologic framework to surficial processes for selected areas. 

The Louisiana barrier islands are part of a complex system with many overlapping and interrelated processes. 

Data for the BICM tasks were collected and compiled with consistent approaches and methodologies. The resulting data 

are more comparable, consistent, accurate, and complete than previously available barrier-island data that were generated 

for local projects. BICM databases and survey results provide scientific support for understanding the complex coastal 

changes that are occurring in coastal Louisiana and provide a baseline dataset for future investigations of the entire 

Louisiana Coastal Area (LCA) barrier-island system.

Monitoring the Louisiana Coast

Typically, monitoring and modeling environments and associated physical processes on a regional scale are 

more complex efforts than on the local scale, primarily because regional studies must consider diverse physical processes 

that interact at multiple scales. On a regional scale, for example, the benefits of improved habitat in one location may be 

counteracted by degradation at another location, and the net result could be interpreted as no overall benefit. In addition, 

regional studies commonly involve monitoring changes in multiple baseline conditions over time or space and typically 

are very labor intensive. However, regional studies provide a comprehensive assessment of coastal change, whereas 

local studies typically focus on a single system. When possible, site-specific monitoring and regional-scale information 

BICM Program Summary Report: Data and Analyses 2006 through 2010
5

Monitoring the Louisiana Coast Figure 2. Data-coverage map for each BICM task: barrier-shoreline post-storm assessment, historical shoreline changes, bathymetric and historical seafloor change, lidar surveys for the Louisiana coast, habitat mapping and change analysis, and characterization of coastal surface-sediment samples.
6

BICM Program Summary Report: Data and Analyses 2006 through 2010 ed as numbers of photos, images, mosaics, line-kilometers, minutes of video, and number of Locations and amount of 2006–2010 BICM data collect Table 1. samples collected/ analyzed by scientists. Volume and Data type / BICM Region The Lakes Chandeleurs Modern Lafourche Teche Acadiana E. Chenier W. Chenier TOTAL VOLUME 1 - POST-STORM ASSESSMENT 2005 Aerial photos no data 126 81 243 165 87 194 233 1,129 2006/2007 Aerial photos 1,717 204 654 423 433 1,276 290 164 5,161 2005 to 2006/2007 Photo pairs no data 20 18 75 34 no data 25 33 205 2005 to 2006/7 Historic Photo pairs time series no data 49 38 68 120 no data 13 22 310 2006/2007 Video Aerial Surveys (minutes) 312 63 118 117 84 369 82 56 1,201 NOAA Coastal Survey maps (T-sheets) used as primary source for the 1855-1898 National Geodetic Survey's (NGS) vector shorelines 18 5 7 3 1 14 54 NOAA Coastal Survey maps (T-sheets) used as primary source for the 1904-1952 National Geodetic Survey's (NGS) vector shorelines 5 4 13 4 2 20 53 Coastal Flights - Aerial photos no data 9 21 29 8 no data no data no data 67 DOQQs (1998, 2004, 2005) individual or mosaicked 5 no data 1 1 no data 1 1 no data QuickBird (2005) no data 2 1 4 1 no data no data no data TOTAL Shoreline length evaluated (kilometers) 1,405 Shoreline Change Rates and Land Area Change Graphs - Historical, Long Term, Short Term, and Near Term VOLUME 3 - BATHYMETRY AND BATHYMETRIC CHANGE 2006 Bathymetry data (Line-kilometers) no data 4,670 no data 1,070 10,502 Historical H-sheets (NOAA) georeferenced and digitized no data 12 no data 23 Change maps produced (1800's to 2000's) no data 4 6 3 3 no data 18 Sediment volume analysis (1800's to 2000's) no data 2 no data 7

Elevation Grid - Bare Earth no data 5 3 5 3 1 5 4 26

Elevation Grid - First Surface no data 8 2 5 4 3 10 8 40

Elevation Grid - Difference no data 3 2 5 3 no data 5 4 22

VOLUME 5 - HABITAT CLASSIFICATION AND CHANGE

Classification Maps 1996/8 - 2005 no data 10 20 20 16 no data no data 20 86

 Change Maps 1996/8-2005 no data 8 20 24 16 no data no data 20 88

Land Loss Maps 1996/8-2005 no data 8 20 20 16 no data no data 20 84

Mosaic (year) no data no data no data 1996 1996 no data no data no data

no data 1998 1998 no data no data no data no data 1998

no data no data 2001 no data no data no data no data 2001no data 2002 2002 2002 2002 no data no data no data

no data 2004 2004 2004 2004 no data no data 2004

no data 2005 2005 2005 2005 no data no data 2005

VOLUME 6 - SEDIMENTS

# of sediment samples no data 301 200 393 209 no data no data 397 1,500

 * see Table 2, Volume 2 Report for temporal distribution of shorelines

3

65

See Tables 5 and 6, respectively - BICM Volume 2

11

2

** Historical data acquired from List and others (1994) 

4,762

2

**

VOLUME 2 - SHORELINE CHANGE/LAND LOSS*VOLUME 4 - LIDAR
7

needs should be interrelated. In some cases, regional monitoring efforts may be an extension of ongoing local monitoring 

projects, but regional-scale monitoring may also involve designs and procedures that are different from site-specific 

monitoring and may extend beyond the purview of the local project teams. Although regional-scale monitoring efforts may 

be challenging, the resulting data and analyses enable a more comprehensive understanding of each aspect of the diverse 

coastal environments and their dependence upon and interactions among each other.

Although the BICM data-collection effort was extensive, the BICM data could also be integrated with data from 

existing monitoring efforts in coastal Louisiana. For example, the Coastal Wetlands Planning, Protection and Restoration 

Act (CWPPRA) program has been monitoring restoration and protection projects in coastal Louisiana since 1990 (Steyer 

and Stewart, 1992; Steyer and others, 1995). The CWPPRA monitoring program incorporates a comprehensive wetlands 

monitoring and assessment component, the Coastwide Reference Monitoring System (CRMS; Steyer and others, 2003). 

The establishment of the CRMS network represented a change from local, project-oriented monitoring to regional-scale 

monitoring and assessment of overall ecosystem health. The proposed BICM program study plan (Troutman and others, 

2003) included repeated data-collection efforts along the barrier islands and sandy shorelines every 5 years and was 

intended to complement CRMS and integrate coastal-shoreline monitoring from numerous restoration efforts. CRMS 

and BICM provide system-wide performance measures that are evaluated to help determine the cumulative effects of 

restoration and protection projects in coastal Louisiana, as demonstrated in the Terrebonne Basin Barrier-Shoreline 

Restoration Project Feasibility-Level Monitoring and Adaptive Management Plan (Louisiana Coastal Area [LCA] 

Adaptive Management Framework Team, 2010).

Review of Available Data Prior to BICM Implementation

Several previous studies contributed to our present understanding of the geologic framework and processes in 

the BICM study area. Williams and others (2012), Flocks, Kulp, and others (2009), Flocks, Twichell, and others (2009), 

Flocks, Miner, and others (2009), and Kindinger and others (2001) provided a comprehensive review of relevant studies 

through 2000. Suter and others (1991) conducted a regional nearshore sand-resource inventory from Marsh Island 

to Sandy Point. The Louisiana Barrier Island Erosion Study, a cooperative study with the USGS and the Louisiana 

Geological Survey (LGS), investigated the general geologic framework, historical changes, and modern processes 

affecting the Louisiana barrier islands (Sallenger and Williams, 1989). The final products of the Barrier Island Erosion 

Study included the publication of a shoreline-change atlas (Williams and others, 1992) and a seafloor-change atlas (List 

and others, 1994) for the coastline extending from the Isles Dernieres to the modern delta lobe. Williams and others (1992) 

described the geologic history of the study area and included a detailed series of shoreline maps with accompanying data 

analysis documenting the evolution of the barrier-island systems since the first shoreline surveys in 1853. List and others 

(1994) documented seafloor elevation along the deltaic coast and presented seafloor-erosion and accretion data necessary 

to understand and describe regional sediment-transport processes along the south-central Louisiana coastline.

With funding from CWPPRA, the State of Louisiana implemented a long-term program constructing multiple 

local coastal-protection and restoration projects. After a decade of CWPPRA project implementation, Penland and others 

(2003) assessed five barrier-island restoration projects constructed in Terrebonne Basin along the central Louisiana Gulf 

Coast. That report provided an extensive review of different restoration methods with respect to environmental benefits 

and implications for island longevity, as well as logistical challenges encountered during project construction and total 

construction costs. Penland and others (2003) reported three primary conclusions: (1) the use of dredged material and 

vegetation to restore barrier-island dunes and back-barrier marsh was the most efficient in terms of effectiveness and cost 

to manage and mitigate long-term barrier-island erosion; (2) the use of segmented breakwaters and rubble-mound seawalls 

was less effective and more costly than the use of dredged material and vegetation; and (3) improvements were needed in 

the final design templates to ensure that the slopes and elevations were correct for back-barrier marsh creation. Many of 

the findings in Penland and others (2003) have since been incorporated into subsequent CWPPRA and other restoration 

projects.

Since the early 1980s, the USGS, the LGS, Louisiana State University (LSU), University of New Orleans 

(UNO), and other State and Federal agencies working in coastal Louisiana have compiled large volumes of data. Some 

examples include nearshore to offshore geophysical surveys (USGS, LGS, LSU, and UNO), photo mosaics, repeat lidar 

surveys (USGS and USACE), and the USACE-funded Beneficial Use of Dredged-Material Monitoring Program (2010). 

Some of these data were incorporated into existing national Geographic Information Systems (GIS) databases such as 

usSEABED (USGS; http://walrus.wr.usgs.gov/usseabed/) and regional publications such the Environmental Atlas of the 

Lake Pontchartrain Basin (Penland and others, 2002a). In an effort to facilitate the integration and dissemination of these 

project-specific data for scientific research, the USGS developed the Louisiana Sedimentary and Environmental Database 

Review of Available Data Prior to BICM Implementation
8

(LASED; http://coastal.er.usgs.gov/lased/), and the Louisiana Department of Natural Resources developed the Strategic 

Online Natural-Resources Information System (SONRIS). 

Historical relative sea-level rise (RSLR) in coastal Louisiana is among the most rapid in the continental United 

States (Zervas, 2001) and many studies have documented historical land-loss trends and habitat changes in coastal 

Louisiana (for example, Cahoon and Groat, 1990; Reed, 1995; Barras, 2003; Barras and others, 2008; and Linscombe 

and Hartley, 2011). But there are very few peer-reviewed habitat-classification studies for coastal Louisiana. The existing 

studies primarily consist of internal GIS-change analyses conducted for the annual CWPPRA Wetlands Value Assessment 

process and various state and U.S. Army Corps of Engineers (USACE) restoration-planning documents such as Coast 

2050 (LCWCRTF and WCRA, 1998), the LCA (USACE, 2004), and the Louisiana Coastal Master Plan (CPRA, 2007, 

2012). The most recent National Wetlands Inventory database for coastal Louisiana is from 2009 (Dahl, 2009) and 

includes data originally published in Wicker (1980, 1981). Various Landsat Thematic Mapper satellite-based land-cover 

datasets have been used for regional updates, but these generally do not use a common, standardized habitat-classification 

scheme (for example, Hartley and others, 2000 - GAP, 1993; and Fry and others, 2011 - USGS National Land Cover 

Database, 2006). 

Six BICM Volumes – Data Reports

The six data-collection tasks under the 2006 to 2010 BICM program were assigned to separate science teams on 

the basis of area(s) of expertise. In order to meet the objectives outlined in the BICM working plan, the science teams 

acquired both new and, in some cases, historical data. The data for each BICM task were organized into six data volumes, 

each of which includes a brief report summarizing the methodology, data, and results. Currently (December 2012), these 

data volumes can be accessed at: ftp://ftp.dnr.state.la.us/bicm/. Because BICM was largely an extensive data-collection 

effort (table 1) intended to support long-term coastal monitoring, the data volumes primarily consist of raw data. However, 

most of the data volumes also include preliminary analyses that establish historical and baseline conditions for future 

studies, and Volumes 2, 3, and 5 include detailed shoreline, bathymetric, and habitat-change analyses, respectively. In 

addition, much of the 2006 to 2010 BICM data have been published as part of separate studies, including task-specific 

peer-reviewed journal articles (for example, Miner, Kulp, Penland, and others, 2009) and a comprehensive analysis of the 

Breton National Wildlife Refuge (USGS Scientific Investigations Report 2009-5252, Lavoie, 2009). Brief summaries of 

each of the BICM data volumes follow.

Volume 1: Barrier-Shoreline Post-Storm Assessment

The Volume 1 aerial video-survey archive includes imagery from 1984 to 2007 (Westphal and others, 2009). 

The BICM surveys included both still aerial photography and simultaneous video imagery and established a standardized 

methodology to produce imagery that can be directly compared with imagery from future surveys. The baseline 2005 

aerial photography was collected immediately following the landfalls of Hurricanes Katrina and Rita on August 29 and 

September 24, respectively (Westphal, 2009). As part of the Volume 1 Barrier-Shoreline Post-Storm Assessment, photos 

from the 2005 and 2006/2007 surveys (Westphal, 2008; Westphal and Penland, 2009) were compared and the resulting 

photo pairs illustrate recent coastal-landscape change between these time periods (fig. 3). In addition, photographic slide 

archives for historical surveys conducted between 1984 and 1992 were analyzed for images that overlapped with the 

recent surveys, and time series encompassing several time periods were created for locations where multiple images were 

available (Westphal, 2009).

Volume 2: Shoreline Changes and Barrier-Island Land Loss, 1800s to 2005

Historically, land-loss rates in coastal Louisiana exceeded 100 square kilometers per year (km2/yr) (37 square 

miles per year [mi2

/yr]) (Dunbar and others, 1992; Barras and others, 2003; National Inventory Report [NIR], 2008). 

Although land-loss rates have declined since about 1978, recent land-loss rates remain higher than the pre-1950s 

background rates (Barras and others, 2008; Couvillion and others, 2011; NIR, 2010), resulting in drastic changes to 

shoreline position, geometry, and configuration. BICM data were used to conduct a comprehensive shoreline-change 

analysis of the entire coastal shoreline in order to (1) establish a baseline dataset for future restoration efforts; (2) define 

the character and patterns of historical shoreline change; and (3) quantify the rates of linear shoreline retreat. The effects 

of the 2005 hurricane season in Louisiana and subsequent development of integrated hurricane-protection and coastalrestoration planning programs made this an appropriate time to collect the baseline data necessary for understanding past 

BICM Program Summary Report: Data and Analyses 2006 through 2010
9

Six BICM Volumes – Data Reports

Figure 3. Example of Volume 1 Barrier-Shoreline Post-Storm Assessment aerial time-series photo pair of Trinity Island for 2005 and 

2007. Red arrow denotes the same geographic location (BICM Volume 1; Westphal and Penland, 2009).

changes and planning for the future. 

In data Volume 2, historical maps, satellite imagery, and aerial photography were integrated to document patterns 

and rates of shoreline change relative to the high-water line for 80 shoreline reaches over four time periods (figs. 4 and 

5): 1855–2005 (historical term), 1920s–2005 (long term), 1996–2005 (short term), and 2004–2005 (near term) (Martinez, 

O’Brien, and others, 2009a). The average historical and long-term shoreline-change rates were –2.7 and –4.2 meter per 

year (m/yr) (–8.9 and 13.8 foot per year [ft/yr]), respectively. Between 1996 and 2005, the average short-term shorelinechange rate accelerated to –8.2 m/yr (–26.9 ft/yr). The average near-term rate of erosion following landfall of Hurricanes 

Katrina and Rita in 2005 was –57.8 m/yr (–186.6 ft/yr) (Sallenger and others, 2009). The highest rates of erosion due 

to the 2005 storm impacts were found along the Isle Dernieres and the Timbalier and Chandeleur Islands, where some 

shoreline reaches underwent as much as 182 meters (m) (597 feet [ft]) of landward retreat. Shoreline reaches that did not 

undergo significant shoreline retreat generally were associated with beach nourishment, dune construction, and backbarrier marsh-creation projects.

Volume 3: Bathymetry and Historical Seafloor Change, 1869–2007 

High rates of delta-plain subsidence, ongoing eustatic sea-level rise, and processes such as storms, island 

segmentation, changes in sediment supply, and human alteration, collectively contribute to shoreline retreat and barrierisland land loss as shoreline sediments are eroded or become inundated by marine waters (Penland and Ramsey, 1990). 

Although mapping and identifying shoreline changes and the aerial extent of barrier islands is essential to understanding 

the shoreline and barrier island response to storms, monitoring the subaqueous extent of the islands is also important. 

A significant component of the BICM program included documenting the historically dynamic morphology within the 

nearshore, offshore, and back-barrier environments in coastal Louisiana. Data Volume 3 includes (1) compilation of 

known historic bathymetric datasets from multiple time periods; (2) new bathymetric data collected during the BICM 

project; and (3) analyses of patterns and rates of seafloor change along selected shorelines. 
10

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 4. Location map depicting the 80 different reaches of shoreline (numbered on figure) designated during the BICM program to 

analyze shoreline change for coastal Louisiana. See the Volume 2 data report for maps depicting historical (1855–2005), long term 

(1920s–2005), short term (1996–2005), and near term (2004–2005) shoreline changes for each of the 80 regions (modified from BICM 

Volume 2; Martinez, O’Brien, and others, 2009a).

The Chandeleur Islands region provides a good example where historical data were located, georeferenced, 

digitized, and transformed to a common horizontal and vertical datum for comparison with the recent bathymetric data 

acquired for BICM (Miner, Kulp, Penland, and others, 2009). From these data, maps were created that depict bathymetric 

change over approximately 130 years (fig. 6) (Miner, Kulp, Motti, and others, 2009; Miner, Kulp, Penland, and others, 
11

Six BICM Volumes – Data Reports

Figure 5. Historical shoreline positions for the Isle Dernieres from 1887 to 2005 with change maps for time periods: 1887–1934, 1934–

1996, 1996–2004, and 2004–2005 (modified from BICM Volume 2; Martinez, O’Brien, and others, 2009a).
12

2009; Miner, Kulp, Weathers, Motti, and others, 2009; Miner and others, 2011). Similar datasets were compiled for 

the Isles Dernieres, Timbalier Islands, and Plaquemines Parish barrier islands and also along the western Chenier Plain 

beaches. These maps contributed to a comprehensive assessment of the most geologically active portions of the barrier 

islands. In addition, the most recent surveys conducted by the USGS and UNO will serve as an important baselinebathymetry dataset for future monitoring of the shoreline to measure both storm-induced and long-term coastal change.

Volume 4: Accuracy of EAARL Lidar Ground Elevations Using a Bare-Earth Algorithm in Marsh and Beach 

Grasses on the Chandeleur Islands, Louisiana

Topographic surveys of the BICM shorelines were collected using four different airborne lidar systems (Hansen 

and Howd, 2009; Morgan, 2009). For most of the BICM regions, post-hurricane surveys were flown in September 

or October 2005 (Chenier Plain, Acadiana Bays, and Chandeleur Islands) using the National Aeronautical and Space 

Administration (NASA) Experimental Advanced Airborne Lidar (EAARL) system. Post-hurricane data along the Teche, 

Lafourche, and Modern delta coasts were collected in December 2006 using a Leica ALS50-II lidar system. For each of 

the regions, the post-hurricane data were compared to data collected in September 2001 (Chandeleur Islands only) or 

October 2002 using the NASA All Terrain Mapper (ATM) (Hansen and Howd, 2009). Additional surveys were flown 

over the Chandeleur Islands in October 2005 using the USACE Compact Hydrographic Airborne Rapid Total Survey 

(CHARTS) lidar system and in March and September 2006, and in June 2007 using EAARL to monitor post-hurricane 

morphological changes (Doran and others, 2009).

The Chandeleur Islands lost more than 80 percent of their land area during Hurricane Katrina, and many of the 

islands experienced continued shoreline retreat during the following 2 years (fig. 7). In addition to land-area losses, the 

decreased dune elevations made the islands increasingly vulnerable to future storm inundation. The USGS, CPRA, and 

USACE are continuing to monitor changes in shoreline position, land area, and elevation to assess the long-term poststorm response of the Chandeleur Islands. 

Volume 5: Chenier Plain, South-Central Louisiana, and Chandeleur Islands Habitat Mapping and Change 

Analysis 1996 to 2005 

The goal of Volume 5 task was to classify land area by habitat type along five coastal shorelines (the western 

Chenier Plain; the Teche, Lafourche, and Modern deltas; and the Chandeleur Islands) (figs. 1 and 2) for four discrete time 

periods (1996 or 1998, 2001 or 2002, 2004, and 2005) and to identify habitat changes that occurred between those time 

periods (Fearnley, Brien, and others, 2009a). The BICM data sources were color-infrared (CIR), QuickBird satellite and 

Digital Orthophoto Quarter Quadrangle (DOQQ) imagery for each region and time period. Imagery data were mosaicked, 

projected to a common datum, and resampled to 2-m (6.6-ft) pixel resolution. Habitat types were classified using the 

eight categories (water, intertidal, marsh, barrier vegetation, beach, bare land, structure, and riprap) defined by Penland 

and others (2004). The habitat maps were analyzed to produce habitat- and land-area-change maps for each region 

(fig. 8) (Fearnley, Brien, and others, 2009b, 2009c). Monthly and annual mean water levels from six USACE tide gages 

were calculated for the analysis time periods, and differences in mean water level between image-acquisition dates were 

assessed in the habitat-change interpretations.

Hurricanes Katrina and Rita significantly impacted many coastal habitats within the BICM study areas. In 

several areas, low-lying habitats were inundated with water and eroded due to flooding and high winds associated with 

the passage of each storm. This resulted in a decrease in coastal land and habitat areas in 2005. However, some areas also 

experienced an increase in beach habitat along the coastline as a result of sediment being transported inland with the storm 

surge. Overall, reductions in the extent of marsh, barrier vegetation, and intertidal habitat occurred due to conversion to 

beach or open water; these changes can be attributed directly to hurricane impacts (Fearnley, Brien, and others, 2009d; 

Fearnley, Miner, Kulp, Bohling, Martinez and Penland, 2009; Fearnley, Miner, Kulp, Bohling, and Penland, 2009).

Volume 6: Characterization of Louisiana Coastal Sediment Samples: Back-Barrier through Offshore Samples 

of the Chenier Plain, South-Central Barrier-Island Systems, and Chandeleur Islands

Characterization of sediment texture, or grain size, within coastal-zone environments is necessary in order to 

evaluate relations between sediment-transport patterns, alongshore variability from the shoreline to Depth-of-Closure 

(DoC), geotechnical properties that influence the development of shoreline nourishment and restoration approaches, and 

BICM Program Summary Report: Data and Analyses 2006 through 2010
13

Six BICM Volumes – Data Reports

Figure 6. Seafloor-change maps created by digitizing historical bathymetry and collecting data during the BICM program for the 

northern Chandeleur Islands from (A) the 1870s to the 1920s and from (B) the 1920s to 2006/2007. Warm colors denote erosion, and 

cool colors show deposition of sediment around the islands (modified from BICM Volume 5; Miner, Kulp, Motti, and others, 2009, Miner 

and others, and 2011). Abbreviation: m, meter.

to model-anticipated coastal-system response to storm events. Sediment samples were collected during BICM along 

shore-normal transects across washover platform, back-barrier marsh, dune, beach berm, upper shoreface (mean low 

water; MLW), middle shoreface, and basal shoreface (seaward to DoC) environments in the western Chenier Plain, Teche, 

Lafourche, and Modern deltas, and in the Chandeleur Island regions (Kulp and others, 2011a, 2011b). This baseline 

dataset provides a foundation for restoration monitoring and planning, modeling coastal processes, and developing a 

better understanding of sediment-dispersal patterns. For example, beach-sediment sampling provided data used to relate 

fill performance to characteristics of the fill material for beach nourishment and restoration projects. This sampling design 

also characterized longshore and cross-shore variability in sediment characteristics that will allow assessments of the 

hydrodynamic zonation of sediments on the islands (fig. 9) and that can be used to help explain habitat distribution and 

vegetation composition on the islands.
14

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 7. A time-series depiction of lidar data collected for the Chandeleur Islands showing land loss along the island chain over an 

approximately 5-year period from October 2002 (pink), to September 2005—2 days post-Hurricane Katrina (yellow), and to June 2007—

22 months post-Hurricane Katrina (green) (courtesy, USGS).
15

Six BICM Volumes – Data Reports Figure 8. Habitat-change map (1996 to 2005) for Timbalier Island, Lafourche Delta. This is a final product of data collected during the BICM program used first to classify habitats and then to determine change in habitats over time along the Louisiana coast (BICM Volume 5; Fearnley, Brien, and others, 2009c).
16

BICM Program Summary Report: Data and Analyses 2006 through 2010

ern Mississippi River Delta Figure 9. Map showing locations and grain sizes of surficial-sediment samples collected for the BICM program along one stretch of the mod

olume 6; Kulp and others, 2011b). (modified from BICM V
17

Regional Discussions

Multiple large datasets were acquired throughout the extent of the Louisiana coast during the 2006 to 2010 BICM 

program (table 1). The coast encompasses several geologic and physiographic settings and multiple unique habitats. In 

order to provide the necessary scientific context and background to understand and interpret the BICM data, the eight 

BICM regions were grouped into four areas: (1) the Pontchartrain Basin, (2) the Mississippi River Delta Plain, (3) the 

Acadiana Bays, and (4) the Chenier Plain (figs. 1 and 2). Each of the following regional discussions includes a brief 

description of the geologic setting and BICM results, with a mention of major topographic, bathymetric, habitat, and 

storm-impact changes that occurred in that region. 

The subsurface geologic framework and surface topography of the Louisiana coast reflect a complex history 

of regional plate-tectonic events and fluvial, deltaic, and marine sedimentary processes affected by numerous largemagnitude sea-level variations (Salvador, 1991; Flocks , Twichell, and others, 2009). Despite the complexity, a long 

history of in-depth investigations yielded a substantial understanding of the regional geologic evolution and framework 

and the processes that shape the coast. Kulp and others (2005) provided an excellent review of the geologic history and 

framework of the north-central Gulf of Mexico basin with a specific emphasis on Holocene processes and geomorphologic 

features of the Louisiana coast. 

The 300-km- (186-mi) wide deltaic plain is the product of continuous sediment accumulation deposited by the 

Mississippi River and its distributaries within the entrenched Pleistocene alluvial valley during the last 8,000 to 7,000 

years as sea level rose to within –10 m (–30 ft) of its present position. The delta plain is composed of six major delta 

complexes (fig. 10) consisting of at least 18 smaller deltaic lobes. Several classic studies (for example, Fisk, 1955, 1961; 

Kolb and Van Lopik, 1958; Coleman and Gagliano, 1964; Frazier, 1967) focused on the regressive phase of Mississippi 

Delta sedimentation, during which overlapping, stacked sequences of unconsolidated sands and muddy deltaic sediments 

were deposited adjacent to the active distributary channel(s). Delta-lobe switching occurred about every 1,000 years as 

fluvial gradients along the active distributary decreased and the available accommodation space filled (Coleman, 1981; 

Roberts, 1997). There are relatively few discussions of the corresponding transgressive component of the Mississippi 

Delta, in particular those of Boyd and Penland (1981) and Boyd and others (1989). Following abandonment of individual 

delta lobes or delta complexes, dewatering, compaction, and subsidence of the unconsolidated deltaic sediments 

contributed to regional sea-level rise and submergence of the former deltaic headland. The coarser-grained deltaic 

sediments were reworked by marine processes to form transgressive coastlines, barrier-island systems, and, ultimately, 

Six BICM Volumes – Data Reports

Figure 10. Distribution and chronology of Holocene Mississippi River delta complexes (modified from Kulp and others, 2005).
18

submerged sand shoals on the continental shelf, and the finer-grained sediments were concentrated in back-barrier marsh 

and estuarine environments (van Andel, 1960; van Andel and Poole, 1960; Frazier, 1967; Coleman, 1988; Boyd and 

Penland, 1988; and Boyd and others, 1989).

In addition to periodic shifts in the course of the Mississippi River, sea-level rise has influenced the development 

of the delta plain. From a maximum lowstand at approximate depths of –110 to –150 m (–360 to –490 ft) at the end of 

the Pleistocene Epoch (Curray, 1960; Frazier, 1974; Suter and others, 1987), relative sea level rose rapidly (>0.02 m/yr; 

>0.065 ft/yr) during the early Holocene to within –10 m (–30 ft) of present levels by 7,500 years ago (Coleman, 1988; 

Penland and Boyd, 1981; Penland and others, 1988). Since the middle Holocene, sea level has continued to rise gradually, 

primarily due to compaction and subsidence of thick (>100 m, >300 ft) Holocene deltaic sediments.

The geologic history of the Chenier Plain is closely linked to depositional processes in the delta plain. Beginning 

about 3,000 years ago, alongshore processes began depositing fine-grained deltaic sediments in prograding mudflats along 

the Chenier Plain coastline. When the Mississippi River deltaic depocenters shifted to the east, sediment supply to the 

Chenier Plain decreased, and the mud-rich sediments were reworked by coastal processes, which concentrated the coarsergrained sediments into shore-parallel, transgressive, sandy, beach ridges (“cheniers”). The extant topography, consisting 

of broad mudflats capped by wetland vegetation separated by intervening narrow cheniers, is a result of repeated cycles of 

deposition and sediment reworking. 

Lakes Region - Lake Pontchartrain Basin 

The estuarine ecosystem that includes Lake Pontchartrain is one of the largest in the United States. The lake 

originated as an embayment open to the Gulf of Mexico and covers an area of 1,632 km2 (630 mi2) that rarely exceeds 6 m 

(20 ft) of water depth (figs. 1 and 2). The tidal estuaries of Lake Pontchartrain, Lake Maurepas, and Lake Borgne together 

occupy more than 15,000 km2 (5,792 mi2) and represent the drainage terminus of the Pontchartrain Basin watershed 

(fig. 11). The watershed encompasses approximately 44,000 km2 (16,989 mi2) of rolling hills, woodlands, estuaries, and 

wetlands that support agricultural, coastal, urban, and industrial communities (fig. 1). 

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 11. Map of the Pontchartrain Basin showing the river 

basins that drain into Lakes Pontchartrain, Maurepas, and 

Borgne (modified from Flocks and others 2009a).
19

The areas around Lake Pontchartrain support a population of 2 million, or nearly one-half of the inhabitants in 

Louisiana (http://coastal.louisiana.gov/index.cfm?md=pagebuilder&tmp=home&pid=112 - accessed Dec. 2012). Over 

the past two centuries, human activities have significantly controlled and impacted the geography and environmental 

quality of the lake. Much of the southern shoreline is armored to prevent shoreline erosion, and manmade transportation 

corridors reduce hydrologic connectivity through the Rigolets and Pass Manchac tidal channels and control tidal 

interchange with the Gulf of Mexico. Agricultural and stormwater runoff, deforestation, and shell dredging have degraded 

water quality, reduced habitat, and increased erosion in the surrounding wetlands. By the end of the twentieth century, 

much of the commercial and recreational value of the lake had been damaged (Penland, Beall, and Kindinger, 2002). 

Following the Pontchartrain Basin Restoration Act of 2000, a variety of monitoring, research, and restoration activities 

has led to an enhanced understanding of the ecosystem, and several ecosystem-restoration initiatives and management 

plans have been implemented (Penland, Beall, Bristch, and Williams, 2002, Penland, Beall, and Kindinger, 2002; Penland, 

Beall, and Maygarden, 2002; Reed, 2009).

The evolution of the Pontchartrain Basin began 60 million years ago with the formation of the Gulf of Mexico. 

However, most of the present morphologic features, including Lake Pontchartrain, developed during the last 1,000 years 

(kyr) (Flocks, Kulp, and others, 2009). A prominent feature of the Pontchartrain Basin is a series of terraces north of the 

lake that were formed over numerous glacial cycles from the Pliocene through the Pleistocene. These alluvial deposits dip 

to the south and are overlain south of the lake by the Holocene deposits of the Mississippi River Delta Plain.

During the late Holocene, as rising sea level approached present levels, longshore transport developed a barrierisland system that extends from Mobile Bay to the Pontchartrain embayment. By 4,000 years ago, while the locus of delta 

building was in west-central Louisiana, the barrier-island systems migrated westward into the area that is now Orleans 

Parish. This barrier-island system, known as the Pine Island trend, initiated closure of the incipient Lake Pontchartrain 

Lakes Region - Lake Pontchartrain Basin

Figure 12. Holocene evolutionary model of Lake Pontchartrain: (A) Sea-level lowstand at the end of the Late Wisconsinan exposed 

the Prairie Terrace Formation that was incised by rivers extending to the shelf edge. (B) During the Holocene transgression, longshoretransport processes led to the development of the Pine Island barrier trend. This mid-Holocene trend extends from the Pearl River Delta 

toward the west to the modern subsurface of New Orleans. (C) The Pine Island complex is thought to have ceased development as the 

St. Bernard delta complex prograded across the Pontchartrain Basin from the west, effectively closing off the estuary from the open 

Gulf of Mexico and (D) forming the present southern shoreline of Lake Pontchartrain (modified from Flocks, Kulp, and others, 2009).
20

from the Gulf of Mexico. Eventually, the Mississippi River avulsed eastward, forming the St. Bernard delta complex 

across modern Plaquemines Parish, burying the Pine Island trend, and creating the modern morphology of wetlands, lakes, 

and the Chandeleur Islands (fig. 12). This region is referred to as the Lakes Region because of the system of lakes that 

developed during this time. 

The elevation difference between Lake Pontchartrain and neighboring metropolitan New Orleans creates an 

extremely vulnerable environment for flooding by tropical storms. New Orleans’ elevations average 1.8 m (5.9 ft) below 

lake level, necessitating protection by a system of levees, and stormwater from the city is pumped into the lake. In 

addition, high rates of sea-level rise due to regional subsidence contribute to the ongoing loss of wetlands and barrierislands, which abate storm surge and wave activity during storm events. The extreme vulnerability of New Orleans to 

storm impact was demonstrated in the aftermath of Hurricane Katrina in 2005. On August 29, the eye wall of Katrina 

passed along the eastern edge of the lake. The city of New Orleans experienced wind speeds in excess of 160 kilometers 

per hour (kph) (100 miles per hour [mph]) and a surge of 6–9 m (20–30 ft) (Heitmuller and Perez, 2007). The system 

of protection levees failed at several locations, and 277 x 106 cubic meters [m3] (9,782 x 106 cubic feet [ft3]) of water 

from Lake Pontchartrain, Lake Borgne, and the Chandeleur Sound flooded Orleans and St. Bernard Parishes. Four days 

after the storm, analyses of lidar topography indicated that 150 km2 (60 mi2) of the New Orleans area was flooded by 

1 m (3.28 ft) of water and that water was 3 m (9.8 ft) deep over 25 km2 (9.7 mi2) (Gesch, 2007). The water remained for 

2 weeks and mixed with wastewater, petrochemicals, and other waste associated with the industrial corridor. The bulk 

of this contaminated water was then pumped back into Lake Pontchartrain. Heitmuller and Perez (2007) estimate that 

100 to 200 billion liters (22–44 billion gallons) of water were discharged into the lake; their study concludes that most 

of the waterborne contaminants and microorganisms were flushed out of the lake through the Rigolets and Chef Menteur 

tidal passes. Elsewhere in the Pontchartrain Basin, saltwater intrusion from the floodwaters damaged floodplain forests 

and eroded shorelines (Barras, 2007; Faulkner and others, 2007). In wetland areas surrounding the lake, introduction of 

organic material from the storm surge initiated increased plant growth and elevation, although this increase had dissipated 

2 years after the storm (Reed and others, 2009).

Future evolution of the Pontchartrain Basin is dependent on continued geologic change. This change is most 

dramatically expressed in wetland loss and shoreline erosion as sediment compaction and fault-related subsidence, 

coupled with RSLR, impact the southern portion of the basin. Increasing open-water areas expose major industrial and 

metropolitan centers to storm impact. Continued investigation and monitoring of the processes that drive this change are 

necessary to properly manage the coastal zone and protect the ecosystem and human population. 

The BICM program has limited data from the Lakes Region. Data Volume 1 contains video aerial surveys from 

2006 and 2007, and an oblique digital-photo survey in 2007. Data Volume 2 has shoreline-change analysis from 1880 to 

2005.

History of Topographic and Bathymetric Changes

Rates of shoreline retreat in the Lakes region accelerated along most shoreline reaches since 1855, averaging 

–1.5, –2.4, and –3.0 m/yr (–5.0, –7.9, and –10.0 ft/yr) for the historical (1855–2005), long-term (1904–2005), and 

short-term (1996–2005) periods, respectively (fig. 13). Following landfall of Hurricane Katrina, near-term (2004–2005) 

shoreline-change rates in this region increased significantly, averaging –11.9 m/yr (–39.0 ft/yr) (Martinez, O’Brien, and 

others, 2009a). No bathymetric or lidar data were collected in the Lakes Region during the BICM project.

Habitat Change

The BICM project did not collect habitat classification or change data in the Lakes Region. This is an important 

data gap in the BICM program.

Impacts of Storms

The elevation difference between Lake Pontchartrain and neighboring metropolitan New Orleans creates an 

extremely vulnerable environment for impact by tropical storms. Post-Katrina BICM imagery was collected in the Lakes 

region in 2006 (aerial photography) and 2007 (video aerial surveys) (fig. 14; Westphal and others, 2009).

BICM Program Summary Report: Data and Analyses 2006 through 2010
21

Mississippi River Delta Plain

Figure 13. Map showing shoreline change around Lake Pontchartrain, Lake Borgne, and Lake Maurepaus between 1855 and 2005. 

Data compiled and analyzed for the BICM program, Volume 2 (modified from BICM Volume 2; Martinez, O’Brien, and others, 2009a).

Figure 14. Aerial photos taken of the coastline within the Pontchartrain Lake Basin in 2006 as part of the BICM program: A) East 

Rigolets and B) Frenier Swamp areas (BICM Volume 1; Westphal and others, 2009).
22

Mississippi River Delta Plain

Chandeleur Islands 

The arcuate, 80-km- (50-mi) long Chandeleur Islands (fig. 1) form the longest barrier-island chain in the northern 

Gulf of Mexico. The Chandeleur barrier-island system is part of the Breton National Wildlife Refuge, which extends 

from Hewes Point north of the Chandeleur Islands, along the ephemeral shoals of Curlew and Grand Gosier Islands, to 

Breton Island in the south (fig. 15). The Chandeleur Islands were formed through the erosion and reworking of the deltaic 

headland of the abandoned St. Bernard Delta complex (fig. 10) (Suter and others, 1988; Brooks and others, 1995). The 

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 15. Bathymetric map (2006–2007) using BICM data collected in the nearshore waters around the Breton National Wildlife 

Refuge area. The Chandeleur Islands (green) arcuate barrier-island chain extends from Hewes Point in the north, along the islands to the 

ephemeral shoals of Curlew and Grand Gosier, and Breton Island in the south (modified from Flocks, Twichell, and others, 2009; Twichell 

and others, 2009a). Abbreviation: m, meter.
23

delta was active from about 3,500 to 1,800 years ago (Tӧrnqvist and others, 1996; Miner, Kulp, Weathers, and Flocks, 

2009; Miner, Kulp, Weathers, Motti, and others, 2009; Rogers and Kulp, 2009). After abandonment, waves and currents 

concentrated the coarser-grained deltaic sediments into the Chandeleur Islands and the offshore St. Bernard Shoals. 

Compaction and subsidence of the muddy St. Bernard prodelta deposits, which may be greater than 35 m (115 ft) thick 

(Twichell and others, 2009a), and relative sea-level rise resulted in erosion and submergence of the back-barrier marsh 

environments such that the Chandeleur Islands are presently located about 40 km (25 mi) offshore of the Louisiana 

mainland.

History of Topographic and Bathymetric Change

Topographic and bathymetric data collected for BICM in 2006 and 2007 were merged into a single topographicbathymetric grid (fig. 15). This dataset was compared against historical survey data from the 1870s and 1920s (fig. 16) 

to create bathymetric-change maps and to calculate volumes of sediment erosion and deposition around the Chandeleur 

Islands over the past ~140 years (fig. 6). The 2006/2007 data also serve as a baseline (post-Hurricane Katrina) for future 

change analyses.

The northern segment of the Chandeleur Islands (Hewes Point to Curlew Shoal) includes the highest elevations 

and most extensive subaerial island extents. Between the 1870s and 2006, this segment underwent net shoreface erosion 

of about 285 x 106 m3 (373 x 106 yd3). Much of the eroded sediment was deposited in the back-barrier environment 

(29 percent) through overwash processes or was transported north to Hewes Point (45 percent). 

The Hewes Point terminal spit at the north end of the Chandeleur Islands is an elongate deposit up to 8 m (26 ft) 

thick (fig. 17) consisting of 97 percent well-sorted, fine-grained sand that formed as the result of littoral transport of 

sediment into the deeper waters north of the barrier-island platform. A combination of island orientation parallel to the 

prevailing wave climate, a centralized source of sandy deposits, and terminal accommodation space adjacent to the St. 

Bernard Delta produced this unique depositional system; the approximately 258 x 106 m3 (338 x 106 yd3) deposit at Hewes 

Point is the largest sand body among the Louisiana barrier-island systems. South of Hewes Point, the Chandeleur Islands 

are composed of small islands separated by inlets. The islands contain dunes and overwash splays that protect back-barrier 

saltwater marsh and submerged aquatic vegetation. Although this is the longest section of the barrier-island arc, there is 

significantly less sediment than at Hewes Point because the island platform is only 1.5 to 4.2 km (0.9 to 2.6 mi) wide, and 

the barrier-island deposits are less than 5 m (16.4 ft) thick (Twichell and others, 2009a). Large parts of this section are at 

or below sea level and contain a veneer of sandy material. 

Historically, the central section of the Chandeleur barrier-island system (Curlew and Grand Gosier shoals) 

underwent the greatest amount of net erosion (Miner, Kulp, FitzGerald, and Georgiou, 2009). More than 405 x 106 m3

(530 x 106 yd3) of sediment were eroded between the 1870s and 2007, of which only 18 percent was deposited in the 

back-barrier environment. The Curlew and Grand Gosier shoals are the submerged remnants of these formerly emergent 

barrier islands. The Curlew – Grand Gosier platform is wider (3.7 to 12 km, 2.3 to 7.5 mi) than, and about as thick as, the 

platform that underlies the Chandeleur Islands. 

Like the shoals, Breton Island at the southern end of the Chandeleur barrier-island system has been severely 

reduced in size and is predominantly submerged. The Breton Island platform is 5.2 to 7.6 km (3.2 to 4.7 mi) wide and 

is also less than 5 m (16.4 ft) thick (Twichell and others, 2009a). Only 7 percent of the 51 x 106 m3 (68 x 106 yd3) that 

eroded historically along the shoreface was deposited in the back-barrier environment (Miner, Kulp, FitzGerald, and 

Georgiou, 2009). Much of the sediment loss at Breton Island can be attributed to updrift sand removal at the Mississippi 

River to Gulf Outlet (MRGO) shipping channel. Maintenance of the MRGO has moved up to 52 x 106 m3 (68 x 106 yd3) of 

sediment to a disposal area seaward of the island platform, depleting sediment from the natural system.

Shoreline- and seafloor-change analyses based on historical hydrographic data (since 1869), shoreline surveys 

(since 1855), and satellite imagery for the Chandeleur Islands reveal long-term trends of barrier-island shoreface retreat, 

platform thinning, and, recently, barrier-island disintegration. Volume calculations indicate that sediment was deposited 

downdrift (northward) and seaward at the Hewes Point terminal spit over the past 125 years. A similar volume of sediment 

accreted at the extreme southern limits of the island chain. The volume deposited in the back barrier, however, is only half 

that distributed to the flanks, indicating that the dominant transport mode is alongshore as opposed to cross-shore. The 

depositional sinks at the flanks of the island arc accreted at rates of more than 1 x 106 m3/yr (1.3 x 106 yd3/yr) between 

1870 and 2007; however, calculations of potential alongshore sediment-transport rates based on 20 years of offshore wave 

data are two orders of magnitude less than the accretion rates. The sediment sources for these accretionary zones at the 

flanks include (1) relict deltaic deposits that have eroded from the shoreface since 1870 and (2) nearshore and subaerial 

barrier-island sand. (For more detailed discussion on volumetric changes, see Theme 2, this report.)

Mississippi River Delta Plain
24

BICM Program Summary Report: Data and Analyses 2006 through 2010

detic Survey maps. (B) Figure 16. Bathymetric-data coverage for the northern Chandeleur Islands. (A) The 1870s soundings were digitized from U.S. Coast and Geo

etic Survey). (C) The 2006 data were 

, and the shorelines used were obtained from BICM data (modified 

The 1920s soundings were obtained digitally from the National Ocean Services, Coast Survey (originally from U.S. Coast and Geodcollected during the BICM program by the University of New Orleans and the U.S. Geological Survey

, Kulp, Weathers, Motti, and others, 2009). Abbreviation: m, meter. eathers, and others, 2009; Miner , Kulp, W olume 3; Miner from BICM V
25

Mississippi River Delta Plain

Figure 17. Sediment isopach of Hewes Point terminal spit; deposit (purple and red) is approximately 27 km2 (10 mi2), 8 m (26.3 ft) thick, 

and is composed of 97 percent well-sorted fine sand (modified from Flocks and others, 2011). Abbreviation: m, meter.

Habitat Change

Analysis of BICM habitat data from 1998, 2002, 2004, and 2005 indicated that even prior to Hurricane Katrina, 

the distribution of habitat types on the Chandeleur Islands varied between analyses, and significant changes occurred 

following the passage of Hurricane Katrina in 2005. For example, after Hurricanes Isidore and Lili impacted the area in 

2002, about half of the land area on Breton Island (figs. 18a and 19) and almost all of Grand Gosier and Curlew Islands 

were converted to open water (Fearnley, Brien, and others, 2009b). All three islands had recovered slightly by 2004, but 

all habitat types on Breton, Curlew, and Grand Gosier Islands were converted to open water in 2005 (fig. 19) following the 

passage of Hurricane Katrina (Fearnley, Brien, and others, 2009d).

Compared with the southern and central islands (Breton to Curlew Islands), the total habitat acreage on the 

northern Chandeleur Islands was relatively stable from 1998 to 2004 (fig. 19). In 2001, specimens of Spartina alterniflora

(smooth cordgrass) were planted on 10 overwash fans on the northern islands as part of the Chandeleur Islands Marsh 

Restoration Project (PO-27; LCWCRTF, 2004). These plantings and higher island elevations may have helped to mitigate 

the impacts of Hurricanes Isidore and Lili in this area. Like Breton, Grand Gosier, and Curlew Islands, the northern 

Chandeleur Islands were significantly impacted by Hurricane Katrina; in the 2005 analysis, all habitat types except some 

marsh areas were converted to open water (figs. 18b and 19).

Impacts of Storms

Presently, the Chandeleur Islands are experiencing a very high RSLR (>4 millimeter per year [mm/yr]; >0.16 inch 

per year [in/yr]; Twichell and others, 2009b) and are undergoing extreme subaerial deterioration due to the combined 

effects of compaction of the underlying St. Bernard prodelta deposits, eustatic sea-level rise, and multiple impacts by 

tropical storms in the past decade. Recent storm activity has had the most significant impact on the subaerial extent of 

the Chandeleur Islands, and researchers have documented an increasing inability of this barrier-island chain to recover 

from storm-induced breaching and dune erosion (fig. 7). Tropical storms can cause rapid land loss, and major events drive 
26

BICM Program Summary Report: Data and Analyses 2006 through 2010

ify habitats and then to Figure 18A. Habitat-change map of Breton Island (1998 to 2002). This is a final product of data collected during BICM used first to class

, Brien, and others, 2009b). determine change in habitats over time along the Louisiana coast (BICM Volume 5; Fearnley
27

Mississippi River Delta Plain

Figure 18B. Habitat-change map of the Chandeleur Islands (2004 to 2005)—note the large areas of habitat change to water after 

passage of Hurricane Katrina. This is a final product of data collected during BICM used first to classify habitats and then to determine 

change in habitats over time along the Louisiana coast (BICM Volume 5; Fearnley, Brien, and others, 2009b).
28

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 19. Cumulative percentage histograms of habitat change in analysis areas during the four analyses time periods: (A) Breton 

Island analysis area totals 9.3 km2

 or 2,354 ac. (B) Curlew and Grand Gosier Islands analysis area totals 44.9 km2 or 11,089 ac. (C) North 

Chandeleur Island analysis area totals 205.4 km2

 or 50,748 ac. (modified from BICM Volume 5; Fearnley, Brien, and others, 2009d).

long-term shoreline erosion and transgressive submergence of the barrier-island chain. For example, only the vegetated 

back-barrier-marsh platforms remained emergent following the passage of Hurricane Katrina in 2005. Subsequently, a 

sandy beach reformed seaward of the marsh platform; however, the shoreline retreated landward by tens of meters, and the 

total emergent land area was significantly reduced compared with pre-Katrina conditions (fig. 20). The impact of tropical 

storms on the Chandeleur Islands is discussed in greater detail in Theme 2.

Modern Delta, Lafourche, and Teche Deltas

The Modern Delta BICM study area extends from Quatre Bayou Pass east to Sandy Point in Plaquemines Parish 

on the west flank of the Mississippi Balize (Birdsfoot) Delta and includes the Chaland Headland, Bay Joe Wise, Shell 
29

Island, Scofield, and Sandy Point (fig. 1). The Modern Delta, as defined for the BICM study, makes up only a small 

portion of the Balize Delta and is part of a continuous shoreline extending from Raccoon Point in Terrebonne Parish to 

Sandy Point; therefore, it will be discussed with the Lafourche and Teche Deltas.

The south-central Louisiana coastline that includes the Teche, Lafourche, and Modern Deltas forms a 165-km 

(102-mi) stretch of barrier shoreline that extends from Raccoon Point in the west to Sandy Point in the east. The study 

area consists of a series of barrier islands and two erosional headlands (fig. 1) that extend approximately 10 km (6.2 mi) 

seaward of the Gulf shoreline and approximately 2 km (1.2 mi) landward of the back-barrier shoreline. 

Mississippi River Delta Plain

Figure 20. Oblique aerial-photo time series of a portion of the Chandeleur Islands: top photo is from July 18, 2001 (courtesy, USGS), 

middle photo is one day after Hurricane Katrina, and bottom photo is 22 months after Hurricane Katrina. Arrows denote same 

geographical location (BICM Volume 1; Westphal and others, 2009).
30

The rapidly eroding Caminada Headland is a remnant of the Bayou Lafourche delta lobe that was active from 

about 1,500 years to 800 years B.P. (before present) (Frazier 1967; Miner, Kulp, Penland, and others, 2009). After 

abandonment, sediments eroded from the subsiding headland were redistributed, forming the transgressive Timbalier 

Islands and Grand Isle barrier systems west and east of Bayou Lafourche, respectively (Penland and Boyd, 1985; Penland 

and others, 1988; Jaffe and others, 1997). West and east of the Timbalier Islands and Grand Isle, the Isles Dernieres and 

Barataria Bight shorelines formed as the result of earlier deltaic progradation and abandonment cycles associated with 

the Lafourche (3,500–4000 years B.P.) and St. Bernard (3,500–2,000 years B.P.) delta complexes, respectively (fig. 10; 

Frazier 1967; Kulp and others, 2005). These shorelines also receive sediment transported downdrift from the eroding 

Caminada Headland. The Plaquemines shoreline east of the Barataria Bight was constructed by sediment eroded from 

the modern Balize delta lobe (1,000 years B.P. to present) as well as reworked sediment transported alongshore from the 

western Chaland Headland (Frazier 1967; Penland and Boyd 1985; Penland and others, 1988; Kulp and others, 2005; 

Miner, Kulp, FitzGerald, Flocks, and Weathers, 2009). 

History of Topographic and Bathymetric Change

High rates of RSLR (~0.9 (centimeter per year [cm/yr], 0.35 in/yr) coupled with storm-induced current and wave 

erosion have led to a large deficit in the coastal-sediment budget along the Teche-Lafourche and Plaquemines shorelines, 

which is forcing barrier-shoreface retreat along the periphery of the Terrebonne and Barataria Basins of the Mississippi 

River Delta Plain. One of the impacts associated with higher rates of RSLR is the conversion of interior wetlands to open 

water, leading to increased bay tidal prism. The increase in tidal prism results in degradation of the barrier islands by inlet 

widening, the formation of new inlets, and sediment sequestration in ebb-tidal deltas. In 2006, BICM sponsored nearshore 

single-beam bathymetric surveys (fig. 21) from Raccoon Point to Sandy Point. These data were integrated with historical 

bathymetry from three time periods (1880s, 1930s, and 1980s) to construct a series of digital elevation models that were 

used to calculate sediment volumetric changes and determine long-term erosional and depositional trends (Miner, Kulp, 

Penland, and others, 2009). Miner, Kulp, Penland, and others (2009) identified several predominant trends during the 125-

year period, including (1) shoreface erosion of ~1.6 x 109 m3 (2.1 x 109 yd3) that forced ~3 km (~1.9 mi) of shoreface 

retreat, (2) sediment deposition in coastal bights and enlargement of ebb-tidal deltas, and (3) a combined increase in tidal 

inlet cross-sectional area from ~41,400 to ~139,500 square meters (m2) (~45,514 to ~166,841 square yards [yd2]). Despite 

the observed sedimentation in coastal bights and ebb-tidal deltas, only ~14 percent of the eroded sediment volume was 

deposited within the study area. Miner, Kulp, Penland, and others (2009) also analyzed bathymetric and shoreline change 

datasets separated by shorter time (sub-annual) periods, demonstrating that long-term trends are driven by processes 

associated with major hurricane impacts, and rates of shoreface erosion are an order of magnitude greater during active 

hurricane seasons compared to long-term trends. 

. The majority (~89 percent) of the total erosion in the study area occurred along the shorefaces of the Isles 

Dernieres, Caminada Headland, and Plaquemines shorelines. By comparing the volume eroded per unit area of these three 

shoreface zones, Miner, Kulp, Penland, and others (2009) showed that the Caminada Headland underwent the greatest 

amount of erosion –3.4 cubic meters per square meter (m3/m2)(4.5 cubic yards per square yard [yd3/yd2]) relative to –2.1 

and –1.7 m3/m2 (–2.75 and –2.2 yd3/yd2) for the Isles Dernieres and Plaquemines shoreface zones, respectively. They 

measured an approximate maximum vertical erosion of –10 m (32.8 ft) along the Caminada Headland, –5 m (16.4 ft) 

along the Isles Dernieres, and –6 (19.7 ft) m along the Plaquemines shoreline. Erosion was not limited to the nearshore 

and upper shoreface; rather, a significant portion of the total shoreface erosion occurred along the lower shoreface and 

extended offshore beyond the limits of the study area (fig. 22).

In addition to shoreface erosion, scour at tidal inlets accounted for ~6 percent of the total erosion that occurred 

in the study area between the 1880s and 2006 (Miner, Kulp, Penland, and others, 2009). Processes that contribute to tidal 

inlet scour include (1) landward migration of inlet throats, (2) lateral inlet channel migration, (3) inlet throat deepening 

and widening, and (4) barrier breaches that remain open, forming new tidal inlets. For a more detailed discussion of 

hydrodynamic processes in Barataria Basin, see Theme 4 in this report.

The observed landward scouring and seaward shoaling of tidal inlets along the Teche-Lafourche coasts line 

resulted in high rates of shoreline and shoreface retreat in the study area (Miner and others, 2007; Miner, Kulp, Motti, and 

others 2009). The highest rates of inlet landward migration occurred along the Timbalier Islands. Raccoon Pass migrated 

landward at a rate of 29 m/yr (95 ft/yr) since the 1880s, and Little Pass Timbalier migrated landward at a rate of 44 m/yr 

(144 ft/yr) since the 1930s.

Lateral inlet migration in the study area was driven by lateral spit accretion as the barrier island migrated across 

a former inlet location (Miner, Kulp, Motti, and others, 2009). Because of the high rates of shoreline retreat, lateral 

BICM Program Summary Report: Data and Analyses 2006 through 2010
31

Mississippi River Delta Plain

Figure 21. Bathymetry (gray increasing water depth to darker blue) collected during the BICM project in 2006 along Caminada 

Headland, Grand Isle, and Grand Terre. Barrier extents are indicated by green with shorelines derived from thematic classifications 

produced from image datasets and GIS editing (modified from BICM Volume 3; Miner, Kulp, Weathers, Motti, and others, 2009). 

Abbreviation: m, meter.

Figure 22. Seafloor-change map of the Raccoon Point to Sandy Point area from the 1880s to 2005. High erosion occurs along the Isles 

Dernieres, Caminada, and Plaquemines shorelines, with deposition occurring at the tidal passes. The 2005 bathymetry data collected 

during BICM (BICM Volume 3; Miner, Kulp, Motti, and others, 2009) were compared with 1880s bathymetry from List and others 

(1994) and with shoreline data analyzed for the BICM program (modified from BICM Volume 2; Martinez, O’Brien, and others, 2009a). 

Abbreviation: m, meter.
32

migration is often accompanied by landward migration. The only tidal inlet where lateral migration dominated the 

morphologic evolution of the barrier system was at Cat Island Pass, where Timbalier Island has migrated >8 km (5 mi) to 

the west since the 1880s (figs. 22 and 23).

Barras (2006) reported that interior wetland loss in the Barataria and Terrebonne Basins inland of the TecheLafourche shoreline occurred at a rate of ~16 km2

/yr (6.2 mi2/yr) for the period 1956 to 2004. Several studies have 

documented increased historical tidal prisms along coastal Louisiana resulting from increased mainland open-water areas. 

The greater water volumes passing through the tidal inlets during each tidal cycle deepen and enlarge existing inlets and 

contribute to the formation of additional stable inlets along the barrier shoreline (FitzGerald and others, 2004, 2007; Miner 

and others, 2007; Howes, 2009). Between the 1880s and 2006, the combined tidal inlet cross-sectional area increased 

more than threefold in the study area (see Theme 4; Howes, 2009), and the number of tidal inlets have increased from 13 

to about 25. During this same time period, the combined barrier island footprint decreased in area from 81 to 25 km2 (31 

to 10 mi2) (Martinez, O’Brien, and others, 2009a).

Increasing the tidal prism also increases the efficiency of sediment trapping in ebb-tidal deltas (Walton and 

Adams, 1976; FitzGerald and others, 2004, 2007; Miner and others, 2007), increasing their sediment volume and extent. 

Although local ebb-tidal delta progradation is apparent at most inlets, the ebb-tidal deltas at coastal bights are the primary 

long-term sediment sinks. This is because more sediment was lost due to shoreface erosion at these locations than was 

deposited at ebb-tidal deltas, causing shoreface retreat at the terminal lobes of the ebb tidal deltas (Miner, Kulp, Motti, and 

others, 2009).

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 23. Historical (from 1884 to 2005) shoreline-change time series of Timbalier Island, Caminada Headland, and Grand Isle using 

shoreline data compiled from BICM Volume 2 (modified from BICM Volume 2; Martinez, O’Brien, and others, 2009a). Note shoreline 

retreat and land loss of Caminada Headland and westward migration and land loss of Timbalier Island.
33

Habitat Change 

BICM habitat data for 1998, 2001, 2004, 2005 were compared along the Teche, Lafourche, and Modern Delta 

shorelines. This portion of the Louisiana coast has a long history of being engineered to help maintain its form and 

structure, and many of the observed habitat changes were directly related to these restoration efforts. The most common 

construction projects typically place large amounts of dredge material (primarily fine-grained sand) on the shoreface to 

enhance beach width and elevation. Another common shoreface protection method was used at Raccoon Island, where 

eight concrete breakwaters were constructed in 1997 along the nearshore and eight more were constructed in 2008–09. 

Some projects also emplaced fine-grained material on the bayside of islands to provide substrate for back-barrier marsh 

environments. 

Habitat change in response to barrier island restoration varies; the following examples describe some of the 

changes that occurred post construction and also how hurricanes impacted those habitats. The Whiskey Island Restoration 

project (TE-27; LCWCRTF, 2002a) was completed in 2002 and showed that although the overall acreages of bare land 

and intertidal flat habitats increased as a result of dredge material emplacement, there was a slight decrease in marsh 

habitat acreages as a result of burial. By 2004, plants had begun to colonize the placed material and the acreages of barrier 

vegetation increased as acreages of bare land decreased. Marsh habitat acreage remained relatively stable, indicating 

that the placed material was colonized by dune and other non-wetland species rather than marsh grass—a result of the 

increased elevation of the placed material. Storm surge associated with Hurricanes Katrina and Rita caused significant 

washover at Whiskey Island, increasing the acreages of beach and intertidal flat habitat (figs. 24 and 25). The extent of 

marsh habitat at Whiskey Island remained relatively unchanged after the passage of Hurricanes Katrina and Rita.

The 1997 breakwater construction at Raccoon Island (TE-29; LCWCRTF, 2002b) increased the intertidal flat 

habitat acreage behind the structures by 2004 (fig. 25). Between 1996 (pre-construction of breakwaters) and 2004, marsh 

plants colonized the newly accumulated intertidal flats, increasing the acreages of marsh habitat. Significant overwash 

resulting from Hurricanes Katrina and Rita in 2005 deposited sandy sediment on Raccoon Island and increasing the 

acreages of beach and intertidal flat habitat while decreasing the acreages of marsh habitat for the 2005 analysis period.

Similar restoration projects have been constructed on Trinity and East Islands (Teche Delta) and Timbalier 

and East Timbalier Islands, Caminada Headland, Grand Isle, and Grand Terre and East Grand Terre Islands (Lafourche 

Delta). In most cases, dredged material was emplaced to create terraces, dunes, and marsh (LCWCRTF, 2002c, 2002d), 

resulting in increased acreages of bare land. Following the passage of Hurricanes Katrina and Rita, beach and overwash 

habitat generally increased at these locations. Planting native flora, such as Spartina patens and Panicum armanum, and 

placement of sand fencing also helped to create dunes (LCWCRTF, 2002c). Construction of breakwaters along Grand 

Isle, as well as numerous placements of sand for beach nourishment, has helped to maintain land acreages. The placement 

of dredge material and vegetative plantings on Grand Terre created 127 acres of land in the eastern portion of the island 

(LCWCRTF, 2008). 

Impacts of Storms

Using data collected during the BICM program, Miner, Kulp, Motti, and others (2009) and Miner, Kulp, 

FitzGerald, and Georgiou (2009) analyzed the impact of storms on the Teche, Lafourche, and Modern Delta coastline. The 

following summarizes these results.

Bathymetric data collected in July 2005 (DeWitt and others, 2007) were compared to the BICM data collected in 

June 2006 (fig. 26) to assess the impact of storms on the Caminada Headland shoreface and compare long-term sediment 

transport volumes with short-term sediment transport resulting from extreme storms. In order to assess the impact of three 

hurricanes that impacted the area in 2005 (Hurricanes Cindy, Katrina, and Rita; Knabb and others, 2005, 2006; Stewart, 

2006), the 2006 survey reoccupied the same transects as the 2005 survey. Miner, Kulp, Penland, and others (2009) showed 

that between 2005 and 2006, the maximum vertical erosion (~1 m; ~3.28 ft) occurred in water depths >8 m (26 ft) along 

the lower shoreface (fig. 26). The volume of sediment eroded from the Caminada Headland shoreface and nearshore 

environments was 8.94 x 107 m3 (11.69 x 107 yd3) from a 1.55 x 108 m2 (1.85 x 108 yd2) area. The long-term (1880s to 

2006) average rate of erosion for the same area was ~2.4 x 106 m3/yr (~3.14 x 106 yd3/yr). Shoreline straightening and 

equilibrium occurs during post-storm redistribution of sediment from nearby shorelines by littoral transport processes (fig. 

27). Redistribution of sediment readily occurs especially when nearby islands have recently been nourished providing an 

available sediment source. 

Mississippi River Delta Plain
34

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 24. Habitat-change classification for Whiskey Island, Teche Delta between the years 1996 and 2005 showing that during the passage of Hurricanes Katrina and Rita, significant washover occurred on Whiskey Island, increasing the acreages of beach and intertidal-flat habitat (BICM Volume 5; Fearnley, Brien, and others, 2009b).
35

Acadiana Bays

nd (total analysis area 20.0 km2 Figure 25. Cumulative percentage histograms of habitat change in analysis areas during the four analyses time periods: (A) Whiskey Isla

, Brien, and others, 2009b). or 4,936 ac) and (B) Raccoon Island (total analysis area 7.0 km2 or 1,725 acres) (modified from BICM Volume 5; Fearnley
36

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 26. Caminada Headland shoreface seafloor-change map, 2005 to 2006: (A) Short-term bathymetric changes along the shoreface 

of the Caminada Headland and (B) the x-x’ shore-normal profile comparison, demonstrating erosion that occurred between July 2005 

and June 2006. The two surveys were separated by the 2005 hurricane season, during which Hurricanes Cindy, Katrina, and Rita 

impacted the study area. The volume of sediment eroded during this single year was almost 40 percent more than the long-term 

(1880s–2006) average of erosion. The map coordinate system is UTM Zone 15 N meters. Modified from Miner, Kulp, FitzGerald, Flocks, 

and Weathers, 2009, and DeWitt and others, 2007. Abbreviation: m, meter.
37

Acadiana Bays

Figure 27. Example of Volume 1 Barrier-Shoreline Post-Storm Assessment aerial time-series photo pair of Elmers Island for 2005 and 

2007 (BICM Volume 1; Westphal and Penland, 2009).

Acadiana Bays

The Acadiana Bays extend from Marsh Island to Point Au Fer Islands and include West Cote Blanche, East Cote 

Blanche, and Atchafalaya Bays (figs. 1 and 2). These shallow bays and marshes are remnants of the Teche/Maringouin 

inner-shelf delta complex and include some of the oldest deposits in the BICM study area. The Teche delta complex 

deposited sediments in this region from about 6,000 to 3,000 years ago, after which flow was directed eastward to the 

St. Bernard delta complex (Frazier, 1967). Presently, the predominant process is active deposition and delta building 

associated with the Atchafalaya River, which is generating some of the highest accretion rates (at the Wax Lake and 

Atchafalaya Deltas) in the Mississippi River Delta Plain. These sediments are mostly laminated muds with coarser-grained 

material accumulating proximal to the modern deltas.

Compared with the other BICM study areas, the Acadiana Bays region has historically been the focus of far fewer 

investigations; most of these studies focused on the Atchafalaya and Wax Lake Deltas. As reported by van Heerden and 

Roberts (1988), in the 1970s, subaerial growth of the bayhead Atchafalaya Delta resulted from sediment infilling of the 

Atchafalaya River Basin and flood events that delivered an increased sediment load from the basin to the river mouth in 

Atchafalaya Bay. Since then, flood events and human alterations have contributed to or reduced delta growth (Flocks and 

others, 2002). Van Heerden and Roberts (1988) described the delta stratigraphy as “old bay” fill and prodelta deposits that 

coarsen upward into distributary and levee deposits. Roberts and others (1997) described a similar geologic framework 

from the Wax Lake Delta.
38

A stratigraphic cross section across Atchafalaya Bay to the west of the present navigation channel (fig. 28) shows 

the transition from a brackish-marsh environment into estuarine, or bay, and then modern fluvial delta (Flocks and others, 

2002). Calibrated Accelerator Mass Spectrometry (AMS) radiocarbon-age dates from the marsh-peat layers range from 

2,470 to 3,310 years BC, which corresponds to the end of active Teche Delta progradation. Averaged subsidence rate 

across the core transects is approximately 0.094 cm/yr (0.037 in/yr). This is the same average subsidence rate determined 

by Roberts and others (1994) from a core acquired approximately 19 km (12 mi) to the northwest (and within the second 

lobe of the Teche Delta, as defined by Frazier [1967]). Farther offshore, Neill and Allison (2005) measured deposition 

rates of Atchafalaya River muds at 1–2 cm/yr (0.4–1.79 in/yr). However, they suggested that sediment bypassing farther 

offshore and erosion by storms will prevent future land accretion in the area, constraining any subaerial extension to the 

modern Wax Lake and Atchafalaya Deltas.

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 28. Vibracore transect across Atchafalaya Bay, to the west of the present navigation channel. The cross section reflects the 

transition from a brackish-marsh environment into estuarine, or bay, and then modern fluvial delta (modified from Flocks and others, 

2002). Abbreviation: km, kilometer; AMS, Accelerator Mass Spectrometry.

History of Topographic and Bathymetric Changes

Shoreline-change trends in the Acadiana Bays region reflect the growth of the Atchafalaya and Wax Lake Deltas 

over the past century (fig. 29). In general, between the mid-1800s and the mid-1900s, rates of shoreline loss were fairly 

consistent, averaging about –3.5 m/yr (–11.5 ft/yr) (calculated from Martinez, O’Brien, and others, 2009a). Over the next 

half century, the bay shoreline reaches continued to retreat even as rapid accretion at the Wax Lake and Atchafalaya Deltas 

was initiated. Since then, shoreline retreat across the bays has stabilized, and delta growth has continued. Despite delta 

growth of >6 m/yr (>20 ft/yr) since the mid-1900s, long-term shoreline trends for the Acadiana Bays are negative, ranging 

from –1.5 to –8.0 m/yr (–4.9 to –26.3 ft/yr), with a 119-year cumulative average of –3.0 m/yr (–9.8 ft/yr), and an average 

cumulative retreat of 1.2 km (0.75 mi). No bathymetric data were collected in the Acadiana Bay region during the BICM 

project.
39

Acadiana Bays

Figure 29. Shoreline-change map (1800s to 2005) of the Morgan City quadrangle. USGS Quadrangle in the Acadiana Bays region 

analyzed during BICM project (BICM Volume 2; Martinez, O’Brien, and others, 2009a).

Figure 30. Oblique aerial photos: (A) Atchafalya Delta, 2006, and (B) Marsh Island, 2005, shorelines taken as part of the BICM program 

(BICM Volume 1; Westphal and Penland, 2009).
40

Habitat Changes and Impacts of Storms

No habitat classification or change data were collected in the Acadiana Bays region during the BICM project. 

This is an important data gap in the BICM program. In 2005, post-Hurricanes Katrina and Rita photography was acquired 

as a photo survey of the Marsh Island Gulf shoreline (fig. 30). This photo survey was integrated into the BICM Volume 1 

dataset, but no further analysis, historical time-series photography, or post-hurricane photo pairs are available. This is an 

important data gap in the BICM program.

Chenier Plain 

The Chenier Plain extends from Sabine Pass in the west to Southwest Point on Vermillion Bay in the east. The 

BICM project further divided the Chenier Plain into the western and eastern Chenier Plain (Sabine Pass to the Lower Mud 

Lake Outlet and Lower Mud Lake Outlet to Southwest Point, respectively) (figs. 1 and 2). The Sabine, Calcasieu, and 

Mermentau Rivers transect the Chenier Plain. Four major lakes in the Chenier Plain (Sabine and Calcasieu Lakes in the 

western Chenier Plain and Grand and White Lakes in the eastern Chenier Plain) formed as bays at the mouths of drowned 

late Pleistocene incised river valleys as sea level rose during the Holocene. Early studies (Fisk, 1944; Byrne and others, 

1959; Gould and McFarlan, 1959) correlated the timing and development of individual ridges and chenier complexes 

with delta-lobe switching and shifts in the location of the Delta Plain depocenters. Penland and Suter (1989) and McBride 

and others (2007) further refined these chronologies and described in detail the distribution, geomorphic features, and 

processes that formed the different cheniers and chenier complexes. Although transgressive processes dominated along 

the Chenier Plain coastline historically, with the modern Mississippi deltaic depocenter located in the eastern delta plain, 

Huh and others (2001) and Draut and others (2005) documented renewed mudflat progradation and increased sediment 

deposition on the inner-continental shelf along the eastern Chenier Plain coastline associated with sediment derived from 

the Atchafalaya River.

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 31. Historical (1855 to 2005) shoreline-change rates in meters per year along the Chenier Plain coastline (BICM Volume 2; 

Martinez, O’Brien, and others, 2009a).
41

History of Topographic and Bathymetric Changes

BICM and historical bathymetric data were collected only offshore of the western Chenier Plain beaches, whereas 

lidar surveys and shoreline-change analyses were conducted along the entire length of the Chenier Plain coastline. 

Historically, the western Chenier Plain shoreline has been relatively stable, with average shoreline-change rates averaging 

0.73, –4.49, and 0.7 m/yr (2.4, –1.6, and 2.3 ft/yr) for the historical (1855–2005), long-term (1904–2005), and shortterm (1996–2005) periods, respectively (Martinez and others, 2009a). In contrast, the eastern Chenier Plain shorelines 

experienced rapid retreat of –4.1, –4.76, and –7.3 m/yr (–13.4, –15.6, and –23.8 ft/yr) during the same time periods 

(fig. 31; Martinez, O’Brien, and others, 2009a). In particular, the Mermentau River, Rockefeller Refuge, and Mulberry 

Island shoreline reaches consistently experienced very high rates of erosion (up to –15.6 m/yr or –51.0 ft/yr short-term 

change along the Rockefeller Refuge shoreline). The Freshwater Bayou shoreline is the only reach in the eastern Chenier 

Plain where the shoreline prograded (2.6 to 3.2 m/yr or 8.6 to 10.4 ft/yr) for the historical to short-term analysis periods. 

This shoreline corresponds to the same area where Huh and others (2001) and Draut and others (2005) documented 

mudflat progradation and inner-shelf deposition along the eastern Chenier Plain coast. Average near-term shoreline-change 

rates differed significantly from the historical- to decadal-scale change rates for both the western (18.2 m/yr or 60.0 ft/

yr) and eastern (0.76 m/yr or 2.5 ft/yr) Chenier Plain coastlines. Assuming that these changes are indicative of nearly 

instantaneous redistribution of sediment from the nearshore area by Hurricane Rita, it is unlikely that the near-term trends 

will persist into the future.

Bathymetric data collected for BICM in 2007 (fig. 32) were compared with historical survey data from the 1880s 

and 1920s to create bathymetric-change maps and calculate volumes of sediment erosion and deposition along the western 

Chenier Plain beaches over the past ~130 years (Miner, Kulp, Weathers, and Flocks, 2009). These maps show significant 

changes in depositional patterns for the 1880s to 1920s relative to the 1920s to 2007s time period (figs. 33 and 34). The 

2007 dataset also serves as a baseline (post-Hurricane Rita) for future change analyses. Between the 1880s and 1920s, 

significant volumes of sediment were deposited in the Calcasieu Pass and Sabine Pass ebb-tidal deltas (net deposition 

55.4 x 106 and 56.8 x 106 m3 or 72.5 x 106 and 74.3 x 106 yd3, respectively), and the overall trend for the nearshore areas 

was essentially no change or sediment deposition (fig. 33). The only areas that showed net sediment erosion during this 

time were the Calcasieu River inlet and the nearshore extent along the Lower Mud Lake shoreline. In contrast, except 

for Calcasieu River ebb-tidal delta and localized deposition updrift of the Sabine and Calcasieu Pass jetties, most of the 

Chenier Plain

Figure 32. Western Chenier shoreline and 2007 bathymetric map using BICM-program data. Land is indicated by green with shorelines 

derived from thematic classifications produced from image datasets and GIS editing (BICM Volume 3; from Miner, Kulp, Weathers, and 

Flocks, 2009). Abbreviation: m, meter.
42

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 33. Western Chenier historical seafloor-change map from the 1880s to 1920s using digitized H- and T-sheets from the US 

Coastal and Geodetic Survey (modified from BICM Volume 2; Martinez, O’Brien, and others, 2009a) and seafloor change methods and 

uncertainty analysis (BICM Volume 3; Miner, Kulp, Weathers, and Flocks, 2009). Abbreviation: m, meter.

Figure 34. Western Chenier historical seafloor-change map from the 1920s to 2007 using digitized H- and T-sheets from the U.S. 

Coast and Geodetic Survey (modified from BICM Volume 2; Martinez, O’Brien, and others, 2009a) and seafloor change methods and 

uncertainty analysis (BICM Volume 3; Miner, Kulp, Weathers, and Flocks, 2009). Abbreviation: m, meter.
43

analysis areas along the western Chenier Plain coastline underwent seafloor erosion between the 1920s and 2007 (fig. 

34). However, because of the large volume of sediment deposited in the Calcasieu River ebb-tidal delta offshore from 

Calcasieu Pass (net sediment deposition 130.8 x 106 m3; 171.1 x 106 yd3), the overall 1920s to 2007 change for the entire 

analysis extent was net sediment accumulation. The change in historical depositional patterns was likely due in large part 

to dredging and enlargement of the deep-draft Calcasieu Ship Channel, which channeled freshwater flow and sediment 

discharge to the Gulf of Mexico, bypassing the interior coastal wetlands and the nearshore coastal areas (LCWCRTF, 

2002e; McCorquodale and others, 2009; Meselhe and Miller, 2009).

Habitat Change

BICM habitat classification and change analyses were limited to the western Chenier Plain beaches; no habitat 

data were collected in the eastern Chenier Plain. Total marsh habitat in the western Chenier Plain remained relatively 

constant from 1998 to 2005, although there was some variability within the separate analysis areas. Construction of the 

Holly Beach Sand Management Project (CS-31) was completed in 2003. This CS-31 project restored approximately 300 

acres of beach habitat between Holly and Constance Beaches, reestablished the shoreline near its historical position, and 

protected approximately 8,000 acres of existing intermediate and brackish-marsh wetlands north of the beach (LCWCRTF, 

2004). The positive benefit of this project is reflected in the increased beach and marsh acreage in this area between 2001 

and 2004. The amount of intertidal flat present in 2001 is significantly less than that in 1998 or 2004 because of the high 

water at the time that the 2001 imagery was acquired. Scouring and flooding of low-lying areas near the coastline after the 

passage of Hurricane Rita resulted in lower acreages of marsh habitat in 2005 compared with that in earlier years (fig. 35). 

Chenier Plain

Figure 35. BICM habitat-change map (1998 to 2002) for Holly Beach along the western Chenier Plain. This is a final product of data 

collected during the BICM project used first to classify habitats and then to determine change in habitats over time along the Louisiana 

coast (BICM Volume 5; Fearnley and others, 2009b).
44

Similarly, beach habitat was reduced in most areas in 2005; however, some localized increases in beach habitat were 

observed. These increases were the result of sediment being redistributed inland with the storm surge.

Impacts of Storms

The Chenier Plain was significantly impacted by Hurricane Rita, which made landfall on September 24, 2005, 

west of Johnson’s Bayou in southwestern Louisiana. Post-hurricane photo pairs from 2005 and 2006 and historical timeseries photos compiled for the BICM Volume 1 post-storm assessment documented significant damage along the Chenier 

Plain coastline as far east as Freshwater Bayou in the eastern Chenier Plain. In many locations, large volumes of sand 

were deposited inland of the previously existing beach, and extensive areas of low-lying coastal wetlands were flooded by 

the storm surge (fig. 36). 

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 36. Oblique aerial time-series photo pair of Johnson’s Bayou shoreline for the years 2005 and 2006 (BICM Volume 1, Westphal, 

2008). House is in the same location.
45

Discussion of Louisiana Coast-Wide and Topical Themes

Data collected during the BICM program were extensive and make up one of the broadest available coastal 

geophysical datasets for the Gulf of Mexico (GOM). In an attempt to integrate the data collected into meaningful analyses 

of the Louisiana shoreline, several coastal-wide and topical themes have been selected. The objectives of the thematic 

discussions are to address coast-wide impacts of relative sea-level change to the Louisiana coastal system, focusing on 

inlets, extreme storms, and habitats.

THEME 1: Barrier-Shoreline Evolution in a Regime of Rapid Relative Sea-Level Rise and 

Interior-Wetland Loss

Rates of RSLR, which are locally in excess of 1 cm/yr (0.39 in/yr), are driving barrier-shoreface retreat along the 

periphery of the Mississippi River Delta Plain. In addition, historical wetland losses in the delta-plain interior totaled more 

than 2,300 km2 (888 mi2) between 1956 and 2004 (fig. 37). This conversion of interior wetlands to open water increased 

bay tidal prisms, resulting in degradation of barriers through inlet widening, development of new inlets, and sediment 

storage in ebb-tidal deltas.

Bathymetric surveys completed as part of the BICM effort combined with historical bathymetry from three earlier 

time periods (dating to the 1880s) provide a series of digital-elevation models (DEMs) from Raccoon Point in Terrebonne 

Parish to Sandy Point in Plaquemines Parish (fig. 22). These models capture the three-dimensional morphological 

evolution of this area. As outlined in Miner, Kulp, Penland, and others (2009), these datasets identified three dominant 

trends during the 125-year period: (1) erosion of ~1.6 x 109 m3 (~2.1 x 109 yd3) from the shoreface, forcing shoreface 

retreat, (2) deposition in coastal bights and at ebb-tidal deltas, and (3) an increase in collective tidal-inlet cross-sectional 

area from ~41,400 m2 to ~139,500 m2 (~445,625 to ~1,501,565 square feet [ft2]) (refer to the Modern Delta, Lafourche, 

THEME 1: Barrier-Shoreline Evolution in a Regime of Rapid Relative Sea-Level Rise and Interior-Wetland Loss

Figure 37. Southern coastal Louisiana land-loss change analysis, 1956 to 2004 (red is conversion of marsh to open water, and green is 

conversion of open water to marsh or delta). Data from Barras and others (2008) and Morton and others (2010).
46

and Teche Deltas, Regional Discussions section in this report for more detail). The rate of increased tidal-inlet crosssectional area is directly proportional to the rate of interior-wetland loss. By comparing data collected between short time 

frames (years to decades) to long-term trends, Miner, Kulp, Penland, and others (2009) reported that rates of shoreface 

erosion and landward barrier migration are significantly greater from storm impacts when compared to the long-term 

trends. Historical shoreline-change analysis also shows that rates of as much as 3 km/century of barrier-shoreline retreat 

during the past 125 years are accompanied by erosion of the back-barrier shorelines, indicating that a net loss of sediment 

from the system coupled with rapid RSLR is causing the barriers to drown in place. 

Physical Coastal Processes 

The wave climate affecting the Louisiana coast can be divided into offshore- and nearshore-waves regimes, the 

latter generated by cold fronts and tropical storms. Deep-water wave data compiled from buoy records over the past 3 

decades provide a mean wave-height range of 0.3 to 1.3 m (0.98 to 4.27 ft) (Georgiou and others, 2005). Closer to shore, 

wind direction is generally from the south and southwest during the summer, and from the northeast and south during the 

winter. Nearshore-wave climate ranges from 0.07 to 0.8 m (0.23 to 2.63 ft), with the higher-wave climate dominated by 

weak storms. Tropical storms, however, can generate wave heights up to 2 m (6.56 ft). The most drastic shoreline change 

has been observed following the passage of tropical storms, although the much higher frequency of cold-front passage 

makes them an important component in nearshore sediment-transport processes (Georgiou and others, 2005).

Relative sea-level rise in coastal Louisiana is driven by subsidence and eustatic sea-level rise. Subsidence rates 

in Louisiana are 3 to 4 times higher than average rates in the Gulf of Mexico (Penland and Ramsey, 1990). Although 

subsidence is dominated by compaction of the recently deposited Mississippi River Delta Plain stratigraphy, faulting and 

fluid extraction also contribute locally, along with glacial isostatic adjustment and lithospheric flexure (Yu and others, 

2012). Data acquired from the NOAA tide gage at Grand Isle show a long-term (1947–2006) rate of 0.92 cm/yr (0.36 in/

yr), although the rate appears to be slowing in recent years (Miner, Kulp, Penland, and others, 2009). Morton and Bernier 

(2010) suggest a slowing trend in subsidence rates may be the result of rebalancing of subsurface stresses following the 

reduction of fluid withdrawal, a trend that may be reflected in the short-term RSLR rate. Natural RSLR and the conversion 

of wetlands to open water are further exacerbated by anthropogenic alterations. Constraining the Mississippi River with 

engineered levees reduces the amount of river-borne sediments contributing to land building, and the excavation of access 

canals for oil and gas extraction increases wave activity, salinity, and tidal volume, resulting in further erosion of the 

wetlands (FitzGerald and others, 2004; Miner and others, 2007).

Coastal-Sediment Budget

Results of the BICM bathymetric data compared to historical data (1880s to 2006) show that over the past 125 

years, 1.6 x 109 m3 (2.1 x 109 yd3) of sediment have been removed from the coastal system along the Teche, Lafourche, 

and Modern Delta shoreline (Miner, Kulp, Motti, and others, 2009). Erosion has not been spatially consistent in this 

system, with the majority volume per unit area occurring along the Caminada Headland (–3.4 m3/m2, –4.5 yd3/yd2) and Isle 

Dernieres areas (–2.1 m3/m2, –2.75 yd3/yd2), mainly from within the lower shoreface (Miner, Kulp, Penland, and others, 

2009).

As the shoreface erodes and retreats, the tidal inlets separating the barrier islands migrate landward, hydraulically 

scouring the seafloor as they advance while infilling and shoaling at their seaward extent. At the same time, interiorwetland loss is occurring at extremely high rates. Between 1956 and 2004, more than 1,600 km2

 (618 mi2) of wetlands 

within the Barataria and Terrebonne Basins have been converted to open water (Barras, 2006). As the tidal prism 

increases, so does flow at the inlets, creating more scour at the inlet throat and more efficient sediment trapping at the ebbtide deltas (FitzGerald and others, 2004, 2007; Miner and others, 2007). The enhanced sediment sink seaward of the inlets 

sequesters material offshore, removing it from the barrier-island system. Over the 125-year study period, more than 80 x 

106 m3 (105 x 106 yd3) of sediment have accumulated offshore from Barataria Pass and adjacent inlets, while 5 x 106 m3

have been removed from the adjacent Grand Isle inner shelf over the same time period (Miner, Kulp, Penland, and others, 

2009).

BICM Program Summary Report: Data and Analyses 2006 through 2010
47

THEME 2: Hurricane Impact to the Chandeleur Islands during the Period 1855 to 2005 and 

the Likelihood of Island Recovery

The impact of hurricanes on coastal systems has been intensively studied, but only recently have quantitative 

analyses progressed to strengthen realistic predictive modeling of the impact and likelihood of barrier island recovery 

following a hurricane. Developing these predictive capabilities requires baseline data and repetitive pre- and post-storm 

data. The BICM program has progressively provided baseline data for much of the Louisiana coast, but repetitive pre- and 

post-storm data are lacking in many areas. The Chandeleur Islands have been extensively studied using the comprehensive 

database collected by BICM along with pre- and post-storm data from Hurricanes Katrina and Rita and several minor 

storm events. The results from these studies provide a basis for understanding the impact of storms events along other 

sections of the Louisiana coast. Therefore, the recovery of the Chandeleur Islands as a proxy for coastal Louisiana is 

described until sufficient pre- and post-storm data are available to develop predictive models for other Louisiana barrier 

islands and shorelines.

The Chandeleur Islands is an arcuate barrier-island chain, extending 80 km (49 mi) that extends from Hewes 

Point north of the Chandeleur Islands, along the ephemeral shoals of Curlew and Grand Gosier Islands, to Breton 

Island in the south (fig. 38). Similar to other barrier islands of the northern GOM, the Chandeleur Islands are important 

THEME 2: Hurricane Impact to the Chandeleur Islands during the Period 1855 to 2005 and the Likelihood of Island Recovery

Figure 38. Location map showing the Chandeleur Islands relative to other physiographic features. The Chandeleur Islands shoreline 

shown is from 2002. The inset bathymetry is from the Coastal Relief Model (Divins and Metzger, 2008). The bathymetry in the larger 

map is a composite of bathymetry collected during the BICM program and the Coastal Relief Model. Abbreviation: m, meter.
48

because they (1) attenuate storm impacts for mainland Louisiana and Mississippi (Stone and Orford, 2004; Stone and 

others, 2005), (2) regulate estuarine salinity and circulation (Reyes and others, 2005), and (3) provide unique habitat 

for threatened and endangered species (Poirrier and Handley, 2007; Fearnley, Miner, Kulp, Bohling, Martinez, and 

Penland, 2009; Fearnley, Miner, Kulp, Bohling, and Penland, 2009). Located approximately 40 km (25 mi) offshore of the 

Louisiana mainland wetlands across Breton and Chandeleur Sounds, the islands are inherently susceptible to the effects of 

tropical storms entering the northern Gulf of Mexico and have been impacted by more than 40 hurricanes since the early 

1900s. 

Long-term sediment-transport trends are punctuated by nearly instantaneous restructuring during storm events. 

This was dramatically demonstrated at the Chandeleur Islands in the wake of Hurricane Katrina (2005), where storm 

surge inundated the islands and completely removed the subaerial sand, leaving discontinuous marsh islets (Sallenger 

and others, 2007). Miner, Kulp, Penland, and others (2009) reported that shoreline change related to storm impact 

significantly exceeds long-term change trends, and Fearnley, Miner, Kulp, Bohling, Martinez, and other, (2009) showed 

that the Chandeleur Islands lost the same amount of land between 1855 and 1996 as between 1996 and 2005 (fig. 39). The 

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 39. Shoreline-retreat and landarea change for the Chandeleur Islands 

between 1855 and 2005. (A) Average 

linear distance from the shoreline (at 

a given year) to an offshore baseline. 

In 2035, the shoreline is projected to 

erode to the bayside position of the 

islands, and the marsh is expected to 

disappear. (B) Using the frequencies of 

storm activity affecting the northern 

Chandeleur Islands and historical 

shorelines, land area was plotted for two 

periods: 1855–1996 (gray line) and 1989–

2005 (black line). These trends show two 

different trajectories for island survival 

(from Fearnley, Miner, Kulp, Bohling, 

and Penland, 2009). Abbreviation: km, 

kilometer.
49

historical (1855 to 1996) loss included changes caused by the passage of Hurricane Camille in 1969, which passed over 

the Chandeleur Islands as a Category 5 storm. Recently, Hurricanes Ivan (2004) and Katrina (2005) decimated the islands, 

reducing surface area by an average rate 10 times greater than in the previous century (Fearnley, Miner, Kulp, Bohling, 

Martinez, and Penland, 2009; Sallenger and others, 2009). Comparing the increased destruction to the Chandeleur Islands 

caused by Hurricanes Katrina and Ivan relative to Camille, Fearnley, Miner, Kulp, Bohling, Martinez, and Penland (2009) 

concluded that hurricane frequency and trajectory relative to island curvature and structure are as important as hurricane 

intensity.

In addition to the historical shoreline data compiled for the BICM project, Fearnley, Miner, Kulp, Bohling, 

Martinez, and Penland (2009) used historic maps from between 1744 and 1848 to determine the historical position of the 

Chandeleur Islands. The geomorphic response of the shoreline during the past century was investigated by using maps 

from five time periods: 1855, 1922, 1989, 2004, and 2005. For a comprehensive documentation of methods, uncertainty 

analysis, and measurement accuracy, see Fearnley, Miner, Kulp, Bohling, and Penland (2009), McBride and others (1992), 

Morton and others (2004), and Martinez, Penland, and others (2009b).

Results of historical (1855 to 2005) shoreline-change analyses conducted by Fearnley, Miner, Kulp, Bohling, 

and Penland (2009) for the Chandeleur Islands are consistent with the conclusions of Miner, Kulp, Penland, and others 

(2009): storm frequency and extreme storm impacts dominate the long-term evolution of island area and shoreline 

retreat (fig. 39). Prior to 1996, storm frequency was low, and island area changed at a relatively low rate of –0.16 km2

/yr 

(–0.062 mi2

); however, the rate increased to –1.01 km2/yr (–0.39 mi2) when the number of storms impacting the shoreline 

increased between 1996 and 2005. Shoreline-retreat rates also increased from a rate of –11.4 m/yr (–37.4 ft/yr) between 

1922 and 1996 to –41.9 m/yr (–137.5 ft/yr) between 1982 and 2005. The passage of Hurricane Katrina in 2005 produced 

an unprecedented erosional impact when compared to pre-storm observations. The shoreline of the northern Chandeleur 

Islands eroded and moved landward by –201.5 m/yr (–661.1 ft/yr), compared with an average rate of –38.4 m/yr (–126 

ft/yr) between 1922 and 2004. Based on their analysis of historical land-area trends (fig. 39), Fearnley, Miner, Kulp, 

Bohling, and Penland (2009) projected that the Chandeleur Islands could potentially lose all marsh area by 2013 if tropical 

storms continue to impact the islands at rates observed between 1996 and 2005. However, if storm frequency returns to 

pre-1996 conditions, the back-barrier marshes may persist through 2037 (Fearnley, Miner, Kulp, Bohling, and Penland, 

2009). 

Analysis of BICM bathymetric data from the Chandeleur Islands (Miner, Kulp, Weathers, Motti, and others, 

2009) identified long-term trends of barrier-shoreface retreat and land loss that are consistent with the long-term shorelinechange analyses presented by Fearnley, Miner, Kulp, Bohling, and Penland (2009). Volume calculations by Miner, Kulp, 

Weathers, Motti, and others (2009) indicate that about 150 x 106 m3

 (196 x 106 yd3) of sediment have been deposited 

downdrift (northward) and seaward of the northern terminal spit during the past 125 years (fig. 40). At the southern end of 

the island chain (south of Breton Island), a similar volume of sediment has accreted (Miner, Kulp, Weathers, and Flocks, 

2009). The volume of sediment deposited in the back-barrier environment (via cross-shore transport), however, is only 

half that distributed by alongshore currents to the flanks. Sediment-accretion rates of the flanking depositional sinks are 

more than 1.0 x 106m3 yr–1 (1.3 x 106

 yd3 yr1) between 1870 and 2007 (Miner, Kulp, Weathers, and Flocks, 2009). The 

sediment sources for the flanking depositional centers include (1) relict deltaic deposits eroded from the shoreface where 

significant erosion has occurred since 1870 and (2) nearshore and subaerial barrier sand. Miner, Kulp, Weathers, and 

Flocks (2009) concluded that long-term shoreline erosion and transgressive submergence are primarily associated with 

major storms and that rapid land loss accompanies these high-energy events. Seasonal nearshore currents transport sand to 

the flanks of the arc, removing it from the littoral system, and the islands are unable to fully recover from storm impacts. 

These downdrift sand reservoirs provide a unique, quasi-renewable potential resource for restoring the updrift barrier 

system if used in a practical coastal management plan.

The impact of Hurricane Katrina on the Chandeleur Islands in 2005 has been well documented. Sallenger and 

others (2009) studied geomorphic changes to the islands following the storm landfall by using multiple lidar surveys and 

additional BICM data. A summary of their study follows, and the full publication can be found in Lavoie (2009).

Sallenger and others (2009) found that nearly 2 years after Hurricane Katrina removed 86 percent of the subaerial 

surface area of the Chandeleur Islands, most of the island chain continued to rapidly erode (fig. 41). The hurricane impact 

triggered feedback processes that intensified shoreline erosion even under relatively mild, post-storm conditions. These 

processes were triggered during the hurricane storm surge, which completely submerged the islands. Sallenger (2000) 

described this “inundation regime,” and noted that when such submergence occurs, it can lead to differential water levels 

in the bay across the island and offshore, forcing currents to erode narrow beaches or inlets, connecting the back-barrier 

bay with the open ocean. Sallenger and others (2009) showed that during Hurricane Katrina, the Gulf of Mexico-facing 

shorelines were eroded landward an average of 268 m (879.3 ft) (fig. 42). Peak dune elevations on the islands decreased 

THEME 2: Hurricane Impact to the Chandeleur Islands during the Period 1855 to 2005 and the Likelihood of Island Recovery
50

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 40. View to the south of the seafloor 

surfaces of the Chandeleur Islands of the 1870s 

(blue) versus those of 2006 (orange). Note the large 

accretionary zone north of Hewes Point (orange in 

foreground) (modified from summary in Lavoie, 2009). 

Abbreviation: m, meter.

from >6 m (19.6 ft) to <3 m (9.8 ft), and sand was removed from the island surface, exposing remnant marsh platforms 

that were subsequently degraded by relatively small waves. Although some sand had been deposited on the islands by 

June 2007, elevations had not rebuilt appreciably, and the Chandeleurs remained vulnerable to inundation by weak storms. 

Limited sand supply and rapid sea-level rise means it is likely that the Chandeleur Islands will continue to experience 

extreme erosion and will ultimately become completely submerged.

Impacts of Hurricanes and Implications for Management

Numerous recent studies of the Chandeleur Islands have established that the islands are sand starved. Their 

original sediment source was fluvial sediments from the St. Bernard delta lobe (Penland and others, 1988). About 2,000 

years ago, the Mississippi River shifted course, diverted westward, to the location of the Lafourche delta complex. This 

natural transgression initiated a new stage of the St. Bernard delta complex, as coastal submergence and wave action 

started to form the Chandeleur Islands (Penland and others, 1988; Ritchie and Penland, 1988). As waves and currents 

reworked the delta lobe, sand was concentrating into a headland beach or being deposited in spits that formed to either 

side of the headland, such as Hewes Point to the north. As natural subsidence continued, the back-barrier marshes were 

submerged and the headland detached from the mainland, forming the Chandeleur Islands. With continued subsidence and 

sand starvation, the islands are forecast to become smaller and lower and eventually become a submerged shoal (Penland 

and others, 1988). Submergence of the islands is accelerated by storm impact, and Sallenger and others (2009) report 

that the islands response to Hurricane Katrina reveal failure modes that may ultimately contribute to the demise of the 

Chandeleur Islands. Hurricane Katrina stripped sand from the islands, exposing the muddy marsh platforms to waves and 

leading to rapid erosion (Sallenger and others, 2009).

The impact of Hurricane Katrina on the Chandeleur Islands was an unprecedented erosional event and highlights 

the vulnerability of the Chandeleur Islands to major storms. Fearnley, Miner, Kulp, Bohling and other (2009) analyzed 

measurements available between 1855 and 2005 and showed that the Chandeleur Islands area can be expected to convert 

to ephemeral barrier island/shoals between 2013 and 2037 (fig. 39). In addition to storm frequency, a key factor governing 

shoreline response to storm impact is the trajectory of the storm track with respect to the position of the islands. The 

highest rates of shoreline erosion are caused by storms that pass within 120 km (75 mi) to the west of the islands; a 

relatively small amount of shoreline erosion is caused by storms that pass more than 120 km (more than 75 mi) to the east. 

Curlew and Grand Gosier Islands in the southern part of the barrier-island arc reflect the future of the Chandeleur 

Islands. Curlew and Grand Gosier Islands have been reduced to submerged shoals as a result of the high storm frequency 
51

THEME 2: Hurricane Impact to the Chandeleur Islands during the Period 1855 to 2005 and the Likelihood of Island Recovery

Figure 41. Maps of the Chandeleur Islands before and after Hurricane Katrina (August 2005) based on lidar data. The island areas 

represent elevations above mean high water (MHW); elevations below MHW are white. (A) Lidar survey from before Hurricane Katrina 

acquired by using the National Aeronautics and Space Administration (NASA) Airborne Topographic Mapper on October 6 and 12, 2002; 

referred to in the text as the “pre-storm” survey. (B) Survey within several days of the landfall of Katrina taken by using the NASA 

Experimental Advanced Airborne Research Lidar (EAARL) from September 1 and 4, 2005; referred to in the text as the survey 2 days 

after. (C) Survey nearly 2 years after landfall taken by using the NASA EAARL on June 27 and 28, 2007; referred to in the text as the 

survey 22 months after.
52

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 42. Changes of the shoreline (A) and width 

(B) of the Chandeleur Islands from lidar surveys 

before Hurricane Katrina (August 2005), 2 days 

after the storm, and 22 months after the storm. 

Abbreviation: m, meter.

and diminished sand supply during the past decade. These ephemeral islands have undergone submergence in the past as 

a result of storm impacts, including erosion of their marsh platform, and subsequently reemerged during periods of calmer 

weather. The ephemeral nature of these islands is attributed to the absence of a stabilizing back-barrier marsh (Miner, 

Kulp, Weathers, and Flocks, 2009). As the northern islands erode and island areas are reduced to only sandy shoreline 

deposits with little or no back-barrier marsh, they will begin to behave similarly to the southern ephemeral islands.

Miner, Kulp, Weathers, and Flocks (2009) and Lavoie (2009) observed that during the post-storm recovery 

period, landward transfer of sand is facilitated by (1) landward migration of offshore bars that weld to marsh islets, (2) 

recurved spit formation at hurricane-cut inlets, (3) eolian processes (dunes, wind tidal flats, and deposition on the marsh 

surface), and (4) shoal aggradation and landward migration. The dominance of lateral transport over cross-shore transport 

is important, as sand is being concentrated in thick sediment bodies at the flanks of the island arc (fig. 40, Twichell and 

others, 2009a). By understanding where the sand is going, how long it takes to get there, and how the islands respond 

to a rapid introduction of new sediment, more efficient barrier management strategies can be developed. Lavoie (2009) 

suggested that restoration goals should mimic the natural processes of early stages of barrier island evolution (fig. 43), 

using natural coastal currents to transport sand laterally to the island flanks from a centralized source. This method would 

ultimately enhance the islands’ ability to naturally build back-barrier marsh, dunes, and a continuous sandy shoreline. 

Barrier-island sediment nourishment should be executed with the understanding that gulf-side shoreline erosion is 

inevitable; however, in principle, island area can be maintained and enhanced during retreat with strategic sand placement.
53

THEME 3: Impact of Tropical Storms on Barrier-Shoreline Elevations and the Response of Island Renourishment to Storms

Figure 43. Conceptual model demonstrating how a barrier-island management-restoration approach may employ natural physical 

processes to extend the life span of the Chandeleur Islands. The model is based on the Twichell and others (2009a) model that was 

interpreted from geophysical and sedimentological data. (A) Barrier-island formation is the natural result of sediment deposition from 

an abandoned deltaic headland. (B) Continued wave reworking of the sediment that is sourced from a headland or islands. (C) Sediment 

is transported alongshore to the flanks of the island system, leading to the eventual removal of sediment from the littoral system and 

forcing island erosion and submergence. (D) In the case of the Chandeleur Islands, utilizing and placing sediment from the “sediment 

sink” to the north (Hewes Point – HP) and the offshore sediment source from the St. Bernard Shoals (STB) may reverse the process of 

transgressive submergence. (E) The strategically and centrally placed sand will be naturally distributed by longshore currents to close 

inlets, broaden beaches, and increase dune elevations, making sand available for overwash and spit building upon which back-barrier 

growth of marsh vegetation can occur. Placing this sand updrift of the sand that was lost from the system may effectively reset the 

clock to stages A–B.
54

THEME 3: Impact of Tropical Storms on Barrier-Shoreline Elevations and the Response of 

Island Renourishment to Storms 

Hurricanes frequently impact coastal Louisiana causing widespread coastal change (fig. 44). Theme 2 discussed 

the changes that hurricane impacts can cause to barrier island morphology and the possibility of island recovery to prestorm conditions. In this theme the oceanographic and geologic processes that impact a coastal system during the passage 

of a storm will be discussed. Since oceanographic and geologic processes cannot be discussed completely separate from 

geomorphology, there is some overlap. As with the previous themes, the Chandeleur Islands, in particular, are used as 

proxy for the Louisiana coastal system because of the extensive data that are available.

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 44. Hurricane and tropical storm tracks that impacted the Louisiana coast over the 50-year time period between 1957 and 2008. 

Source of storm tracks is the National Oceanic and Atmospheric Administration (2010).

The size, intensity, duration, transit speed, and precipitation of tropical storms are highly variable. These 

variations drive the physical processes that influence coastal evolution. Factors that produce different responses include 

(1) the profile across the island and nearshore of a new construction may not be in equilibrium with the natural system 

and (2) the sediment grain-size of the source is different from the native sediment. Once a constructed barrier island or 

shoreline with appropriate sediment grain size has matured and reached equilibrium, it responds similarly to a storm as 

a natural barrier island or shoreline. For this discussion, it is assumed that natural and constructed barrier islands and 

shorelines respond similarly.

The following discussion summarizes several publications that addressed coastal response to tropical storms, 

many of which used data from the BICM project. Since the 1980s, several studies have documented the rapid landward 

migration and degradation of barrier islands and abandoned deltaic-headland shorelines in the Louisiana coastal zone 

(for example, Penland and others, 1988; Williams and others, 1992). Processes associated with the transgressive phase 

of the delta cycle (Roberts, 1997; Penland and others, 1988) including high rates of delta-plain subsidence, a paucity of 

sand, and interior-wetland loss, coupled with climatic factors such as eustatic sea-level rise and frequent large-magnitude 

storm impacts, collectively contribute to barrier degradation in Louisiana (Penland and Ramsey, 1990; McBride and 

others, 1992; List and others, 1994, 1997; FitzGerald and others, 2007; Miner, Kulp, FitzGerald, Flocks, and Weathers, 

2009; Fearnley, Miner, Kulp, Bohling, and Penland, 2009). Some significant processes are undetectable in the absence of 
55

a regional-scale investigation covering long time periods (Sallenger and others, 1992; List and Terwindt, 1995). While 

the manifestation of processes that drive transgression in the delta plain are well studied and monitored at the surface, 

the seafloor response and the role of seafloor-sediment dynamics in short- and long-term coastal evolution are not as well 

understood. To more effectively identify the magnitude, rates, and processes of coastal evolution in Louisiana, BICM was 

designed and implemented as a framework for a coast-wide monitoring effort.

As reported in Theme 1, before implementation of the BICM project in Louisiana, the only available regionally 

consistent documentation of bathymetry, sediment transport, and seafloor change was presented in List and others (1994). 

During the two decades that followed that compilation, storm intensity and frequency along the Louisiana coast increased 

significantly (Fearnley, Miner, Kulp, Bohling, and Penland, 2009). As a result of its geographic location, the Louisiana 

coast is susceptible to the effects of almost any major storm entering the northern Gulf of Mexico and has been impacted 

by more than 50 hurricanes since the 1850s.

The first manifestation of storms typically observed is shoreline erosion. Shoreline erosion is an easily measurable 

retreat of the shore along the perimeter of a water body that has substantial fetch to storm waves. The Gulf Coast has been 

impacted by 14 hurricanes over the past decade, and each of these storms caused observable changes to the coast; some 

stretches recovered naturally within months, whereas other changes persisted for several months or years. Sallenger (2000) 

used storm wave-run-up elevation and still-water elevation (which includes storm surge, wave setup, and astronomical 

tide) relative to the peak elevation of the foredune to show that the magnitudes of change can be scaled. Sallenger 

concluded that as the run-up and still-water elevation increase, thresholds that define regimes of increasing impact 

magnitude will be crossed. These impact regimes progress from run-up colliding against the dune and eroding it landward, 

to run-up overwashing the dune, to still-water level completely submerging the beach system (fig. 45; A.H. Sallenger, Jr., 

oral commun., June, 2012). The greatest coastal changes have been observed following complete submergence, which 

can occur locally on a barrier island and can scour inlets, as occurred during Hurricanes Camille (1969), Charley (2004), 

Ivan (2004), and Katrina (2005), or can submerge tens of kilometers of coast, as occurred on the Bolivar Peninsula, Texas, 

during Ike (2008) and on the Chandeleur Islands during Katrina (2005).

THEME 3: Impact of Tropical Storms on Barrier-Shoreline Elevations and the Response of Island Renourishment to Storms

Figure 45. Erosion of a barrier island 

is a function of elevation compared 

to total water run-up, for example, 

surge+setup+runup on the beach 

(Sallenger, 2000). The inundation regime 

can submerge tens of kilometers of coast, 

as occurred on the Bolivar Peninsula, 

Texas, during Hurricane Ike (2008) and 

on the Chandeleur Islands during Katrina 

(2005).
56

The most complete analysis of Louisiana barrier-island storm response and recovery to date has been by Sallenger 

and others (2009), who analyzed the impact of Hurricane Katrina and recovery of the Chandeleur Islands. Katrina was 

an Impact Level 4 on the Sallenger scale (fig. 45). The Katrina storm surge along the Mississippi coast approached 10 m 

(32.8 ft) (Knabb and others, 2005, reported that the highest measured watermark was near Bay St. Louis, Mississippi, at 

8.5 m, 27.9 ft.) Sallenger and others (2009) reported that peak surges along the Chandeleur Islands were smaller, ranging 

from about 3 m (9.8 ft) in the south to nearly 4 m (13.1 ft) in the north. Setup associated with wave breaking on the Gulf 

front of the islands added approximately an additional 1 m (3.28 ft) of still-water level. Using these data, they were able to 

calculate that the storm surge height was sufficient to submerge the southern half of the island chain; in the northern half, 

peak island dune elevations emerged through the combined surge and setup (fig. 46). The total elevation of wave run-up 

on the beach, however, was sufficient to overtop pre-storm peak elevations along the entire length of the islands (fig. 46). 

Therefore, during the early stages of the storm, the entire area of the islands was periodically overwashed by waves, 

driving sand from beaches and dunes from the Gulf side toward the Chandeleur Sound side.

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 46. Peak elevations (Dhigh) determined 

every 20 m (67 ft) along the length of the 

Chandeleur Islands using lidar data processed for 

first return. Only first return is available for the 

“pre-storm” survey, so even though bare-earth 

data are available for 2 days after Hurricane 

Katrina in 2005, the first return is shown here to 

be comparable with pre-storm data. Also shown 

are storm-surge elevations along the shore as 

determined by NOAA using the Sea, Lake, and 

Overland Surges from Hurricanes (SLOSH) model, 

surge plus calculated wave setup, and surge 

plus extreme (2%) wave run-up. (A) “Pre-storm” 

(merged 2001 and 2002) Dhigh determined from 

lidar data acquired with the NASA Airborne 

Topographic Mapper. (B) Dhigh from 2 days after 

the storm determined from lidar data acquired 

with the NASA Experimental Advanced Airborne 

Research Lidar (from Sallenger and others, 2009).
57

During the storm peak, dune elevations were reduced (compare figure 46A with B) because of inundation and 

overwash. At the peak of the storm, the still-water level was sufficient to completely submerge the islands (Sallenger, 

2000; fig. 45, Impact Level 4). Differences in sea level between the Gulf and Sound likely drove currents across the 

island shoals and contributed to the net transport of beach and dune sand from the islands, exposing the underlying marsh 

platforms.

In the aftermath of tropical storms, beaches typically recover naturally to some extent. Recovery processes 

include sand migrating onshore in swash bars and welding onto the beach during the weeks and months after the event 

(Owens and Frobel, 1977). During the 22 months after Katrina’s landfall, repeated lidar surveys showed that the islands 

did not recover uniformly, instead 56 percent of the Gulf-side shore continued to retreat landward, and the islands 

progressively retreated landward between successive lidar surveys (fig. 47). At one location, the total retreat was almost 

500 m (1,640 ft) (Sallenger and others, 2009).

THEME 3: Impact of Tropical Storms on Barrier-Shoreline Elevations and the Response of Island Renourishment to Storms

Figure 47. Changes to a 2.5-km (1.6-mi) reach of the Chandeleur Islands showing persistent erosion and landward retreat during 

the 22 months after landfall by Hurricane Katrina (modified from Sallenger and others, 2009). The base map is a rectified, vertical 

photograph from before the storm, January 20, 2004. A time series of lidar maps is overlain on the photograph; with more recent

surveys overlaid on previous surveys. If no change occurred, only the last survey (purple) would be visible. Erosion is shown between 2 

days after (red) and 2 months after (blue).
58

The muddy composition of nearshore sediments likely contributed to the continued rapid erosion and retreat 

following the storm. With the sand stripped from the islands, the muddy-marsh fragments that remained were exposed to 

the surf of the Gulf of Mexico and were vulnerable to erosion even by the relatively low post-Katrina waves. These marsh 

fragments contained a low percentage of sand and as the marsh shore eroded landward, the sand was released and made 

available to form incipient beaches, while the muddy fine sediments in the eroded marsh continued to disperse. Over time, 

these beaches will provide a veneer of sand that is likely to buffer the marshy shore from continued rapid erosion. 

The 44 percent of the Gulf shore that did not continue to erode over the 22 months after the storm showed the 

development of spits and welded swash bars that advanced the shore seaward. At one location, a beach developed seaward 

of the shoreline position, prograding the shoreline after the storm as much as 100 m (328 ft) seaward. Where accretion 

occurred, the islands widened from an average of 167 m (548 ft, 2 days after) to 231 m (758 ft, 22 months after). However, 

the overall mean shoreline change for the islands over the same period was 13 m (40.6 ft) of erosion.

Bare-earth lidar elevations (vegetation removed) acquired 2 days after and 22 months after the storm measure 

peak elevations on the islands. Immediately after the storm, island elevations averaged about 1 m (3.28 ft, fig. 48A); 22 

months later, elevations had increased by only 0.3 m (0.98 ft, fig. 48B and C). Also shown on these plots are the worstcase (maximum-of-the-maximum) storm-surge elevations for Category 1 through Category 3 hurricanes, as well as the 

surge simulated by NOAA using the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model and Katrina 

conditions.

Post-storm island elevations were lowered sufficiently to be vulnerable to complete submergence (inundation 

regime, Impact Level 4, fig. 45) by a Category 1 hurricane. Nearly 2 years later, island elevations along a portion of 

the northern Chandeleur Islands had recovered enough to be emergent through a Category 1 surge; with the rest of the 

islands vulnerable to inundation. The implication is that islands or shorelines that have been stripped of sand, exposing the 

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 48. Bare-earth peak elevations (Dhigh), maximum-of-the-maximum storm-surge elevations for different categories (“cat”) of 

hurricanes, and storm surge for Hurricane Katrina computed by using the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) 

model. (A) 2 days after. (B) 22 months after. (C) Change in Dhigh between 2 days after and 22 months after (Sallenger and others, 2009).
59

marsh platform base, are highly vulnerable to inundation from subsequent hurricanes, especially in the short term. This 

would likely remove all of the emergent sand from the marsh platforms again, exposing the muddy fragments to further 

degradation. Airborne lidar surveys showed that the inundated Chandeleurs lost 82 percent of their surface area, and their 

Gulf-front shores eroded landward an average of ~250 m (~820 ft). Combined with subsidence of the Mississippi Delta, 

rapid local RSLR has conditioned the coast for future extreme-storm changes. Should global sea-level rise accelerate in 

the future as predicted, barrier islands and sandy shorelines worldwide may respond similarly after being inundated during 

tropical storms.

Besides inundation, extreme storms striking the Gulf Coast region have caused several different morphological 

responses and have resulted in a large range of washover-penetration distances. Morton and Sallenger (2003) report that 

post-storm erosional responses included dune scarps, channel incisions, and washouts, whereas depositional responses 

included perched fans, washover terraces, and sheetwash lineations (fig. 49). The largest of these features are washover 

penetrations, products of shallow water, confined flow, and high-wind stress, ranging in length from approximately ~100 

to 1,000 m (~328 to 3,280 ft) with estimated erosional sediment volumes ranging from ~10 to 225 m3/m (~13 to 294 

yd3/yd) of beach. Unusual styles of morphological response (sheetwash lineations and incised channels) and maximum 

washover-penetration distances are closely correlated. Regional morphological responses and washover-penetration 

distances are controlled primarily by storm size, intensity, and approach direction. Transport and deposition of washover 

sediments across barrier islands and into the adjacent lagoon are common processes along the Gulf. These morphologic 

responses have a potential direct impact to constructed sandy beaches.

The washover process and associated deposits occur along the shores that are overtopped and inundated by 

waves and storm surge, causing the shoreline to retreat landward. The deposits form washover fans and terraces parallel 

to the wetland shores of the Gulf of Mexico or to shores of large embayments. Typical widths of washover deposits are 5 

to 20 m (16.4 to 65.6 ft) along the embayment shores, whereas 20- to 150-m (65.6- to 492-ft) widths have been reported 

along the Gulf shore for extreme storms (Morgan and others, 1958; Ritchie and Penland, 1988; Nyman and others, 1995; 

Faulkner and others, 2007). Thick washover deposits can raise the land elevation above the zone of normal inundation. 

Consequently, an overwashed former wetland near the shoreline can be colonized by non-marsh vegetation and be 

converted to an upland habitat (Courtemanche and others, 1999). As an example, in 1992, Hurricane Andrew buried marsh 

areas with overwash sediments; 2 years later, as much as 40 percent of these barren areas had been revegetated (Morton 

and Barras, 2011). 

THEME 3: Impact of Tropical Storms on Barrier-Shoreline Elevations and the Response of Island Renourishment to Storms

Figure 49. Types of erosional and depositional features produced by extreme storms include (A) dune erosion, (B) channel incision, (C) 

washout, (D) washover terrace, (E) perched fan, (F) sheetwash lineations (Morton and Sallenger, 2003). Whereas these six processes 

can cause shoreline deposition and erosion (Morton and Sallenger, 2003), perhaps the most frequently reported hurricane morphological 

impacts are the widespread shoreline deposits that result from the inland transport of sand and shell by storm overwash. See Sallenger 

scale Impact Level 3 (fig. 45).
60

THEME 4: Barataria Bay Tidal-Inlet Management Considerations

Authors: Howes, N.C.1*, Z.J. Hughes1, D.M. FitzGerald1, I.Y. Georgiou2, J.L. Kindinger3, N.A. Buster3

 1

Department of Earth and Environment, Boston University, Boston, Massachusetts 2

Department of Earth and Environmental Sciences, University of New Orleans, New Orleans, Louisiana 3

St. Petersburg Coastal and Marine Center, USGS, St. Petersburg, Florida 

 * Clastics Research, Shell International Exploration and Production, Houston, Texas

Bathymetric data collected during the BICM project were particularly useful in documenting the evolution of 

tidal-inlet morphology and hydrodynamics, as well as the redistribution of sediment reservoirs that result from the high 

rate of RSLR. Tidal inlets play an integral role in the response of the Louisiana coast to RSLR, and this study identified 

previously unrecognized feedback among inlet morphology, back-barrier tidal range, and tidal prism. This will be 

discussed with a focus on the Barataria Basin barrier island system, beginning with an overview of the morphological and 

hydrodynamic response of the Barataria Basin to RSLR then focusing specifically on the role of tidal inlets. In Barataria 

Basin, high rates of RSLR (~1 cm/yr) caused substantial wetland loss between 1956 and 2004 (more than 775 km2, about 

300 mi2; Barras, 2006) and a concomitant increase in area of open water within Barataria Bay. The increase in open water 

within the bay resulted in a larger tidal prism and forced a greater tidal discharge through the inlets. Inlet cross-sectional 

areas enlarged over time to accommodate the enlarging prism and as inlet area increased, the data indicate that backbarrier tidal range increased and augmented the tidal prism. This feedback between inlet morphology and back-barrier 

tidal range had not been recognized before and illustrates the dynamic, interconnected nature of the processes associated 

with Barataria Bay (or any bay) as a whole. These findings have implications for restoration practices and for identifying 

the importance of constructing land in the lower basin in a proximal location to the tidal inlets. This discussion utilizes 

BICM data as well as additional historical bathymetric data and hydrodynamic data and summarizes the master’s thesis of 

Howes (2009).

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 50. Hydrodynamic instrument deployment locations and acoustic Doppler current profiler (ADCP) survey tracklines 

(Howes, 2009).
61

Methods

To establish the response of tidal inlet morphology and hydrodynamics to RLSR over the past ~100 years, 

modern conditions were measured and compared with past conditions using historical datasets and records. Modern inlet 

morphology was measured with single-beam bathymetric surveys, which were conducted in 2006 and repeated in 2007, 

and included the four Barataria Bay inlets (Barataria Pass, Quatre Bayou, Pass Abel, and Caminada Pass) (fig. 50). To 

establish a comparison with past conditions, a historical record of inlet morphology was obtained from the regional-scale 

bathymetric changes in Barataria documented in BICM Volume 3 using data from surveys in the 1890s, 1930s, 1980s, 

and 2006. Because surveys in the 1890s, 1930s, and 1980s spanned multiple years, the midpoint dates were chosen for 

reference (1888, 1935, and 1988, respectively) (Miner, Kulp, FitzGerald, and Georgiou, 2009). To constrain the modern 

hydrodynamics, acoustic-doppler current profilers (ADCP) were used to profile the tidal flow/exchange within the inlets, 

and four current meters were placed landward of the surveyed inlets to measure the tidal water-surface elevation at the 

time of the surveys. Modern tidal range and the propagation of the tidal wave through Barataria Bay were determined 

from 11 USGS tide-gage stations located within the back-barrier. Historical data on tidal range were obtained from the 

Grand Isle tide-gage for the period 1951 to 2006, and additional historical hydrodynamic data were used from a long-term 

current meter deployment on the Gulf side of Barataria Pass in 2002. Unfortunately, there was no historical record of inlet 

hydraulics. In order to address this gap, modern field data were used to calibrate a one-dimensional (1-D) hydrodynamic 

model of inlet hydraulics focused on Barataria Pass. Once the model was calibrated, it was used to hindcast historical inlet 

hydraulics as well as back-barrier tidal range based on past bathymetric configurations of Barataria Pass obtained from the 

1890s, 1930s, 1980, and 2006 surveys. 

Tidal-Inlet Morphological and Hydrodynamic Evolution

The tidal inlet cross sections in Barataria Basin display variable morphologies. However, two distinct categories 

of inlets were apparent: (1) inlets with a symmetrical cross section, and (2) inlets with a distinctly asymmetrical cross 

section. Barataria Pass is symmetric in cross section, whereas Quatre Bayou Pass, Pass Abel, and Caminada Pass inlets 

are each asymmetric with a shallow subaqueous platform along their eastern margin and a thalweg (deepest portion of 

the inlet) occurring consistently on the western margin (fig. 51a). The asymmetric inlets generally are wider than their 

symmetric counterpart, and among the asymmetric inlets, the Caminada platform width is significantly less than the 

platform widths at Pass Abel and Quatre Bayou.

Historically, cross-sectional areas of the Barataria Basin inlets have increased in response to wetland loss and 

the ensuing larger tidal prism. Between 1888 and 2006, the cumulative inlet area increased by a factor of three, from 

6,400 m2

 to 20,890 m2 (68,889 ft2 to 224,858 ft2) (Howes, 2009). However, as the inlet cross-sectional areas increased to 

accommodate the greater tidal prism, the two categories of inlet symmetries evolved very differently. 

The cross-sectional area of Barataria Pass increased primarily by way of deepening of the inlet (fig. 51a). This 

process can be described by the hydraulic radius, which is defined as the ratio of inlet area to inlet perimeter and is a 

proxy for the mean flow depth. As the cross-sectional area increased, so did the hydraulic radius, following a linear 

trend (indicating deepening) (fig. 51b). In contrast, the increase in area of Quatre Bayou, Caminada Pass, and Pass Abel 

primarily was associated with widening and the erosion of the channel edge, producing a wide shallow platform and an 

asymmetric inlet. As the cross-sectional areas of these inlets increased, the hydraulic radii (or mean flow depth) remained 

nearly constant (fig. 51b). This response demonstrates that morphology of Quatre Bayou, Pass Abel, and Caminada 

evolved along a very different trajectory than that of Barataria Pass. The difference in cross-sectional morphology is 

significant in terms of inlet hydraulics. If all other variables remain constant, a larger hydraulic radius in a channel results 

in greater channel efficiency and less energy lost to friction between the water and the sediment bed. Thus increases in 

channel area at Barataria Pass have resulted in greater inlet efficiency in contrast to the Quatre Bayou, Pass Abel, and 

Caminada Pass, where inlet areas have increased with the widening platform region, but not with the same increase in 

inlet efficiency. This effect is apparent in the hydrodynamic data. For a given tide, Barataria Pass is able to convey twice 

the discharge of Quatre Bayou, despite comparable cross-sectional areas, a fact that can be attributed to the difference in 

hydraulic radius and efficiency. An increase in hydraulic radius, with other factors being constant, also reduces tidal wave 

attenuation and results in a larger tidal range in the back-barrier environments (see Tidal-Range Evolution).

In addition to understanding the overall cross-sectional response of the inlet system to wetland loss and larger 

tidal prisms, it is also important to determine how the tidal discharge and prism are distributed between the inlets. The 

peak discharge at the inlets varies directly with tidal range, such that the greatest discharge occurs during tropic tides (fig. 

52). Tidal discharge is distributed unevenly between the inlets. The discharge at Barataria Pass is more than twice the 

THEME 4: Barataria Bay Tidal-Inlet Management Considerations
62

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 51. (A) High resolution tidal inlet cross sections from 

single beam soundings (Howes, 2009) (* denotes transects 

across the inlets were taken along the same line each, with 

the exception of Quatre Bayou, where they were offset by 50 

meters). (B) Barataria Pass shows an increase in inlet hydraulic 

radius with increased cross-sectional area compared to the 

other three passes. It is also the only inlet that did not develop 

an inlet platform even with increased cross-sectional area 

(Howes, 2009).
63

THEME 4: Barataria Bay Tidal-Inlet Management Considerations

Figure 52. Graph showing the relation between 

peak ebb discharge and tidal range for the four inlets 

(Barataria Pass, Quatre Bayou, Caminada Pass, and 

Pass Abel). The data represent a synthesis of ADCP 

and BICM data collected in 2002, 2006, and 2009 

(Howes, 2009).

magnitude of any other inlet for a given tide. As the tidal range increases over a tropic-equatorial cycle, the peak discharge 

at Barataria Pass increases at a faster rate than at the other inlets (fig. 52), resulting in its capture of a greater proportion of 

flow relative to the other inlets during the largest tides. Barataria is clearly the dominant inlet in the system and is thus the 

focus of the 1-D model. Quatre Bayou has the second largest discharge of the inlets, whereas the discharges at Caminada 

Pass and Pass Abel are roughly equal in magnitude and are the least significant of the group. In order to calculate tidal 

prism, discharge was integrated over a single flood or ebb cycle to determine the volume of water (prism) exchanged 

through the inlets. On the basis of these calculations, Barataria Pass exchanges nearly 50 percent of the bay’s tidal prism. 

These discharge data were used to construct and validate a 1-D model of inlet hydraulics. In general, the model is in close 

agreement with the field data but with a slight tendency to overpredict discharge. This model is used in a later section to 

hindcast bay tidal range. 

Tidal currents in each of the four inlets exceed 1 meter per second (m/s) (3.28 feet per second [ft/s]) at peak ebb 

discharge (Howes, 2009). The greatest currents at Barataria Pass are concentrated along the eastern portion of the inlet 

(average current velocity exceeds 1.25 m/s, 4.1 ft/s). In the other three inlets—Caminada Pass, Pass Abel, and Quatre 

Bayou—maximum currents are entirely confined to the western thalwegs, and the depth-averaged currents in the channels 

are generally ~1 m/s (3.28 ft/s), locally exceeding 1.5 m/s. The shallow platforms in these three inlets account for ~60 

percent of the cross-sectional area, but only 30–35 percent of the total discharge at peak flow. Thus, the majority of the 

discharge is confined to the inlet thalwegs. The inlets to Barataria Bay are ebb-dominant; thus, sediments eroded from the 

bay or adjacent to the inlets are redistributed offshore and sequestered in ebb-tidal deltas. The ebb dominance results from 

the interaction of the diurnal and semi-diurnal tidal constituents (for more information on this process see, van Maren, 

2004). The following section describes the morphological response of each inlet in greater detail.

Barataria Pass

A review of historical bathymetry at Barataria Pass indicated that the inlet channel has not migrated laterally and 

has occupied the same footprint since at least 1888 (fig. 53) (Howes, 2009). In 1958, a navigational jetty was constructed 

on the western side of the inlet. The jetty trapped the littoral transport of sediment, causing Grand Isle to prograde seaward 

while all other regions, such as Grand Terre, retreated. Progradation and erosion of the shoreline resulted in a 15-degree 

counter-clockwise rotation of the inlet channel between 1888 and 2006 (Howes, 2009). In addition to channel rotation, 

Barataria Pass has undergone other geomorphic changes: (1) the inlet has lengthened, (2) the cross-sectional area of the 

inlet throat (defined as the area between the islands) has increased, and (3) the hydraulic radius has increased (Howes, 

2009) (fig. 54). In his analysis of Barataria Pass, Howes (2009) used the 5-m contour to approximate the location of the inlet 

channel and the 10-m contour to approximate the inlet throat/thalweg (the deepest portion of the inlet) (fig. 54a). The inlet 
64

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 53. Graph showing inlet cross-sectional 

area since 1888. The gray points along the x-axis 

represent the bathymetric-survey dates. The change 

between the data points is a linear interpolation 

(Howes, 2009).

Figure 54. The morphological evolution of Barataria Pass, including (A) the extension of the inlet channel as defined by the 5m 

contour, (B) the inlet throat defined as greater than 10 m deep, (C) cross sections across the inlet throat, and (D) the change in hydraulic 

and dynamic radius (dynamic radius is a measure that weights the depth to the power of 5/3); the dynamic-radius measure shows the 

same general trend as hydraulic radius (Howes, 2009).
65

channel extends beyond the barrier islands into the back barrier and seaward onto the ebb-tidal delta. The inlet channel has 

increased in cross-sectional area in response to tidal-prism changes within Barataria Bay. As the tidal prism increases, a 

greater volume of flow converges on the inlet channel, and velocities increase at the channel entrance, resulting in erosion 

and elongation of the channel. The inlet throat occurs in the confined portion between the barrier islands and experiences 

the highest tidal velocities; the length of the inlet throat has remained more stable than that of the inlet channel (fig. 54b). 

The greatest rate of change in cross-sectional area of the inlet throat occurred during the period from 1888 to 1935. 

After 1935, the rates of increase decelerated, and the channel area seemed to stabilize between 1988 and 2006 (fig. 53). 

Although the cross-sectional area of Barataria Pass stabilized in 1988, the cross-sectional area of the other inlets in the 

system has continued to increase. 

Quatre Bayou Pass

Quatre Bayou Pass is the second largest tidal conduit within the Barataria system (Howes, 2009) (fig. 52). 

The inlet throat has significantly deepened over time and has migrated landward as the shoreline retreated historically 

(Penland and others, 2005; Miner, Kulp, FitzGerald, Flocks, and Weathers, 2009) (fig. 55). The shoreline and the inlet 

have undergone more than 1 km of shoreline retreat since 1884 at an average rate of –11.6 m/yr (–38 ft/yr) (Penland and 

THEME 4: Barataria Bay Tidal-Inlet Management Considerations

Figure 55. Morphological evolution at Quatre Bayou Pass, including (A) the extension of the inlet channel, (B) the inlet throat defined 

as greater than 10 m (32.8 ft) deep, (C) cross sections across the inlet throat, and (D) the change in hydraulic and dynamic radius.
66

others, 2005). As the pass migrated landward, it eroded into a complex sedimentary sequence that may consist of a relict 

distributary channel (Levin, 1995), resulting in an extremely irregular bathymetry within the modern inlet channel. The 

rates of shoreline retreat are high in the vicinity of Quatre Bayou inlet for two reasons: (1) the inlet lacks a proximal 

sediment source such as the Caminada headland to the west, and (2) a portion of the longshore drift is trapped in the 

updrift ebb-tidal delta at Barataria Pass (List and others, 1997). 

The 10-m contour within Quatre Bayou did not exist at the time of the 1935 surveys; the contour developed as the 

inlet deepened between 1935 and 1988 (fig. 55b). Howes (2009) reported that the opening at Quatre Bayou widened since 

the 1888 survey and that the opening consists of two distinct geomorphic features: (1) a channel thalweg on the west bank, 

and (2) an extensive shallow shelf on the eastern margin that occupies most of the inlet width (fig. 55c). The majority 

of the tidal flow (between 65 and 75 percent) is confined within the channel. The shelf has a nearly constant depth over 

its width, and Howes (2009) suggested that a combination of sediment starvation and wave-current processes eroded a 

veneer of unconsolidated barrier sediments adjacent to the inlet, leaving the platform morphology. During a sustained ebb 

flow, tidal currents over this platform are between 0.35 and 0.50 m/s (1.45 and 1.64 ft/s) with velocities sufficient to cause 

erosion of sands and abrasion of muds. Georgiou and others (2005) showed that storm waves (>1–2 m, >3.28–6.56 ft) may 

also play a role in the erosion of this platform. The increase in hydraulic radius in Quatre Bayou is much more muted than 

the increase in Barataria Pass when measured over the same time period, since much of the increase in cross-sectional area 

has been due to the expansion and widening of the shallow subaqueous platform (Howes, 2009).

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 56. Morphological evolution at Pass Abel, including (A) the extension of the inlet channel, (B) there is no panel for B because 

the inlet throat was defined as greater than 10 m, and this inlet did not achieve that depth, (C) cross sections across the inlet throat, 

and (D) the change in hydraulic and dynamic radius.
67

Pass Abel

The morphological evolution of Pass Abel is similar to that of Quatre Bayou. Pass Abel is the widest inlet in the 

chain (2.2 km, 1.4 mi) (fig. 56). The thalweg is located along the western margin, abutting a wide subaqueous platform on 

the eastern side; a morphology that is remarkably similar to that of Quatre Bayou (fig. 55b). Pass Abel formed between the 

1888 and 1935 surveys. Shamban (1985) reported that it was present on the 1841 maps, although this initial opening was 

ephemeral and had apparently closed by 1888 before reopening permanently sometime after that (fig. 56a). FitzGerald and 

others (2004) hypothesized that the inlet reopened and remained stable in response to the increased bay tidal prism due to 

ongoing wetland loss. The proximity of Pass Abel to Barataria Pass allows it to capture a portion of Barataria’s tidal prism, 

which likely has contributed to the decreasing rate of change in inlet area at Barataria Pass after 1935 (Howes, 2009). 

THEME 4: Barataria Bay Tidal-Inlet Management Considerations

Figure 57. Morphologic evolution at Caminada Pass, including (A) the extension of the inlet channel, (B) there is no panel for B 

because the inlet throat was defined as greater than 10 m, and this inlet did not achieve that depth, (C) cross sections across the inlet 

throat, and (D) the change in hydraulic and dynamic radius.
68

Caminada Pass

The channel thalweg at Caminada Pass is also situated on the western margin of the inlet. A shallow platform 

extends to the eastern margin (fig. 57a and b), where the shore has been stabilized by riprap (Howes, 2009). In this area, 

the shoreline retreat rate is slower than in other areas of Barataria Basin, primarily due to the close proximity of Caminada 

Pass to the Caminada Headland, which is the primary sediment source for the shoreline (Howes, 2009). Between 1988 and 

2006, the inlet grew substantially in cross-sectional area, channel-platform area, and hydraulic radius (fig. 57c). 

Shoaling in Caminada Pass between 2006 and 2007 (Howes, 2009) was apparently a post-storm response to 

the Hurricane Katrina landfall. During passage of the hurricane, the wind pattern forced water into the basin (which was 

elevated due to the storm surge) southwest toward Caminada Pass (Resio and Westerink, 2008). Elevated water levels and 

storm-surge return flows produced ebb currents through the inlet in excess of 3.3 m/s (10.8 ft/s) (Carter, 2008). Howes 

(2009) suggested that these storm-induced, ebb-dominated tidal currents eroded sand from the channel margins, resulting 

in a temporary widening of the inlet, and the inlet, cross-sectional area was, thus, out of equilibrium with normal tidal 

flows. Subsequent shoaling of the inlet restored it to pre-storm configuration (a process captured by the 2006–2007 repeat 

survey). 

Tidal-Range Evolution

A long-term tide- gage dataset provides a historical record of tidal range in Barataria Bay. The record is a 

composite of two tide stations: the older Bayou Rigaud station and a modern Grand Isle station. Until 1979, the Bayou 

Rigaud station (NOAA ID: 8761720) was situated approximately 2.0 km (1.24 mi) west of Barataria Pass. In 1979, the 

modern Grand Isle station (876172) was installed in close proximity to Barataria Pass. The timing of station relocation 

does not correspond to the break in slope in the tide record around 1970; thus, the relocation is not responsible for the 

BICM Program Summary Report: Data and Analyses 2006 through 2010

Figure 58. (A) Three complete cycles of the 18.6-year nodal tidal cycle. (B) The residual tidal signal after the 18.6-year cycle is 

removed, showing an increase in tidal range over approximately the past 50 years; the rate change increased between 1951 and the 

early 1970s (Howes, 2009).
69

observed changes in tidal range (Howes, 2009). The tidal record is clearly dominated by an 18.6-year cycle, but also 

contains a longer-term increase in tidal range underlying the 18.6-year cycle (fig. 58).

To identify the underlying trend, Howes (2009) applied a fast-Fourier transform to the long-term Grand 

Isle (1951–2006) tidal record (fig. 58) after removing the variance associated with the 18.6-year cycle signal. This 

analysis identified an increase in tidal range of 2.5–3.0 cm (0.98–1.18 in.) over the period of 1951–2006, which is an 

approximately 10 percent increase from 1951 levels. The analysis showed that the greatest rate of tidal-range increase 

occurred between 1950 and 1970, which coincided with peak rates of RSLR (fig. 59). After 1970, the tidal range 

stabilized. Howes (2009) hypothesized that the increase in tidal range is explained by the observed change in inlet 

hydraulics, in particular the increase in the hydraulic radius of Barataria Pass, which was a result of the larger tidal prism 

caused by high rates of RSLR and wetland loss. Qualitatively, the overall trends in both the hydraulic radius and tidal 

range are extremely similar, although data on hydraulic radius are limited to three points (fig. 59). To test this hypothesis, 

Howes (2009) applied a 1-D hydrodynamic model to hindcast the tidal range in the back-barrier bay immediately 

behind Barataria Pass. Using historical bathymetry data to determine past channel configuration and cross-sectional 

areas, he calculated the previous hydraulic radius and past inlet configuration. The model predicts an increase in tidal 

range stemming from the observed tidal-inlet evolution and establishes a previously unrecognized feedback between the 

inlet hydraulics and back barrier tidal range in Barataria. The model under-predicts the observed increase in tidal range 

obtained from the long-term gage record, but it confirms the existence of the process feedback. 

The observed increase in tidal range has implications for restoration efforts. Traditionally in Louisiana, interior 

wetland loss in response to RSLR has been considered the sole mechanism contributing to the increase in tidal prism. 

However, Howes (2009) identified an internal feedback among back barrier wetland loss, inlet hydraulics, and a 

subsequent increase in tidal range. The increase in tidal range resulting from inlet alteration augments the initial response 

associated with wetland loss and may account for as much as 30 percent of the total increase in tidal prism over the period 

of the dataset. Restoration efforts should consider this effect and focus on maintaining the integrity of the barrier islands 

THEME 4: Barataria Bay Tidal-Inlet Management Considerations

Figure 59. (A) Relative sea-level rise at Grand Isle, 1947–2006. (B) Hydraulic radius at Barataria Pass (blue points) and the increase in 

annual tidal range at Grand Isle relative to tidal range in 1951, as shown in figure 59 (Howes, 2009).
70

and their inlets. The inlets are the effective agents in limiting back-barrier tidal range and thus prism, and as their crosssectional areas increase they become less effective at this process.

Once the tide propagates into Barataria Bay through the inlets, it continues into the basin as a progressive wave. 

The tide is gradually attenuated the farther it travels from the inlets. On a tropic cycle, the tide range decreases from 

0.53 m (1.74 ft) at Barataria Pass to approximately 0.07 cm (0.28 in.) at the Davis Pond diversion ~100 km (62.2 mi) 

up the basin. It takes approximately 13 hours for the high tide to travel from the inlet to Davis Pond. The style of tidal 

wave propagation also has implications for restoration and coastal management. Tidal prism is a volume of water and 

is calculated as a wetted area multiplied by a tidal range. On the basis of this concept, to optimize effectiveness land 

reclamation efforts should consider focusing on the lower portions of the basin, where the efforts may have a much greater 

impact in terms of reducing tidal prism on a per-unit-area basis, because the tidal range is greatest here. For example, a 

unit area of land will reduce tidal prism by 0.53 m3 (18.7 ft3) at Barataria Pass as opposed to 0.07 m3 (2.5 ft3) at Davis 

Pond, which is a factor of ~7.5. This conclusion is in opposition to a recent recommendation of Blum and Roberts (2009) 

that land be created in the upper portions of the basins. Blum and Roberts (2009) concluded that the modern sediment 

supply of the Mississippi River is insufficient to sustain the Louisiana deltaic plain in its entirety, especially in the face of 

accelerated sea-level rise, which is an important and indisputable point. However, the approach and recommendation of 

those authors are based on a passive sediment mass balance and omit the dynamics processes that govern coastal response 

and redistribute sediment. These dynamics processes provide restoration efforts some control over morphological change 

and the inevitable transgression on a decadal–centennial timescale. If the goal of a given restoration effort is to maximize 

overall restoration effectiveness on the entire basin then focusing on segments where effects of the tidal prism are greatest 

should be considered. In particular, the recommendation of those authors for land creation in the upper basin omits the 

central importance of tidal prism on coastal stability and does not consider the feedbacks between inlets and the back 

barrier that are especially relevant for coastal stability on the longer timescales. In addition, land creation in the upper 

basin would consist of low-salinity wetlands, which are more susceptible to erosion during the passage of storms than 

their high-salinity counterparts in the lower basin, as was observed during Hurricane Katrina in Breton Sound (Howes and 

others, 2010). Stemming the increase in tidal prism should be a central focus of restoration, since it is the only means by 

which to slow the erosion of inlets and the fragmentation of the barrier coast, which is especially relevant on a decadalcentennial timescale.

Conclusions: Impacting Wetlands and Inlets in Central Louisiana

The processes affecting Barataria Pass, Quatre Bayou Pass, Pass Abel, and Caminada Pass inlets are not unique to 

the Barataria Basin. Processes in this basin are an example of the far-reaching effects of RSLR on coastal land loss and the 

strong interaction and coupling between barrier-island and back-barrier systems. The coastline as a whole is changing, and 

no morphologic feature, habitat, or process is stable or independent from another. The observations and results presented 

by Howes (2009) (summarized above), are specific to Barataria Bay but are relevant to future changes along the entire 

coast. Howes’ (2009) primary conclusions follow:

(1) The spatial pattern of wetland loss in the back barrier has a strong bearing on tidal exchange through the inlets 

and the increase in tidal prism. Wetland loss in the lower basin results in a larger increase in tidal prism per unit area of 

land lost due to the larger tidal range. As a consequence, restoration efforts directed at land reclamation should focus on 

the lower basin where they will have the greatest potential to effect tidal prism and stabilize the system on a per unit area 

basis. 

(2) The cumulative cross-sectional area of the Barataria Bay inlets enlarged by ~15,000 m2 (161,459 ft2) in 

response to back-barrier wetland loss and a larger tidal prism between 1890 and 2006. In the current barrier-shoreline 

configuration, the bay’s tidal prism is distributed unevenly in the inlets. Barataria Pass controls nearly half of the tidal 

exchange between Barataria Bay and the Gulf of Mexico (48 percent), with Quatre Bayou contributing 23 percent, and 

Caminada Pass and Pass Abel supplying 14–15 percent, respectively. 

 (3) There are previously unrecognized complex coupling and dynamic feedbacks among back barrier wetland 

loss, inlet hydraulics, and tidal range. RSLR and the ensuing wetland loss forced significant changes in both the 

morphology and hydraulics of the tidal inlets, which in turn increased back-barrier tidal range. This coupling feedback 

compounds the initial back-barrier wetland loss and forms a substantial component of the trends in observed tidal prism, 

coastal erosion, and sediment redistribution and storage in offshore ebb-tidal deltas. Restoration efforts clearly benefit 

from a better understanding of these dynamic interactions. This understanding provides a potential to maximize the value 

of sediment input by focusing effort on key areas of the system, which can limit or reduce the rate of transgression and 

coastal land loss. 

BICM Program Summary Report: Data and Analyses 2006 through 2010
71

THEME 5: Habitat Changes Related to Long-Term Relative Sea-Level-Driven Erosion and Short-Term Storm-Driven Erosion

THEME 5: Habitat Changes Related to Long-Term Relative Sea-Level-Driven Erosion and 

Short-Term Storm-Driven Erosion

Habitat change analyses by Fearnley, Brien, and others (2009d) showed that Hurricanes Katrina and Rita had a 

significant impact on coastal habitats within the BICM study areas. In several areas, low-lying habitats were inundated 

with water and eroded, resulting in a decrease in coastal habitat. In some areas, an increase in beach habitat was observed 

along the coastline as a result of sediment being moved inland with the storm surge. Overall, reductions in marsh, barrier 

vegetation, and intertidal-flat habitat due to the conversion to beach or open water can be attributed directly to hurricane 

impacts. The following sections describe the results of Fearnley, Brien, and others (2009d) habitat-change analyses for 

each BICM region based on data from 1996 or 1998, 2001 or 2002, 2004, and 2005; the last two datasets bracket the 2005 

hurricane season.

Pontchartrain Basin

No habitat classification or change data were collected during the BICM project. This is an important data gap in 

the BICM program.

Mississippi River Delta Plain

Chandeleur Islands (Breton Island to Hewes Point)

Fearnley, Brien, and others (2009d) reported that the Chandeleur Islands experienced the greatest overall habitat 

change because of multiple hurricane impacts to the islands. After Hurricanes Isidore and Lili impacted the area in 2002, 

about half of the land area on Breton Island and almost all of Grand Gosier and Curlew Islands were converted to open 

water. These islands had recovered slightly by 2004, but all habitat types on Breton, Curlew, and Grand Gosier Islands 

were converted to open water in 2005 following the passage of Hurricane Katrina. Compared with the southern and central 

islands (Breton to Curlew Islands), the total habitat acreage on the northern Chandeleur Islands was relatively stable from 

1998 to 2004. Higher elevations along the northern islands may have helped to mitigate the impacts of Hurricanes Isidore 

and Lili in this area. Like Breton, Grand Gosier, and Curlew Islands, however, all habitat types except some marsh areas 

were converted to open water in 2005. 

Modern Delta (Chaland Headland, Bay Joe Wise, Shell Island, Scofield, and Sandy Point) 

The relative acreage of habitats within the Modern Delta remained approximately constant between analyses 

despite the passage of Hurricanes Katrina and Rita. The acreage of intertidal habitat fluctuated but was likely a result 

of changes in water-level conditions between time periods and not a response to hurricane effects (Fearnley, Brien, and 

others, 2009d). In addition, the completion of several restoration projects in this area in 2006 and may have masked the 

results of the analysis.

Lafourche Delta (Timbalier Island, East Timbalier Island, the Caminada Headland, Grand Isle, Grand Terre Island, and 

East Grand Terre Island) 

At Timbalier, East Timbalier, and Caminada Islands, overwash increased beach habitat, and a net decrease 

in marsh habitat and a total loss of barrier vegetation occurred on all three islands. Despite hurricane impacts, barrier 

vegetation and marsh habitat increased between 2004 and 2005, likely as a result of restoration efforts and the 

implementation of breakwaters. Grand Isle and Grand Terre experienced minimal impacts from the passage of the 2005 

hurricanes, and restoration efforts at Grand Terre apparently increased marsh habitat at the expense of barrier vegetation 

(Fearnley, Brien, and others, 2009d).
72

Teche Delta (Isles Dernieres Chain from Raccoon Point to Wine Island Pass)

 At Raccoon Island, hurricane overwash decreased marsh habitat and increased the acreage of beach and intertidal 

habitat. Whiskey Island marsh habitat proved resilient to washover; however, acreage of beach habitat was converted to 

open water, likely because of shoreline erosion. In addition, intertidal, marsh, and barrier-island vegetation lost significant 

acreage that was converted to beach. Hurricane impacts at Trinity Island included an increase in the acreage of beach and 

intertidal-flat habitat, despite the conversion of intertidal habitat to open water, because of habitat change from marsh and 

barrier-island vegetation to intertidal habitat. Washover increased the acreage of beach habitat at East Island, reducing 

intertidal-flat, marsh, and barrier-island habitats.

Acadiana Bay

No habitat classification or change data were collected during the BICM project. This is an important data gap in 

the BICM program.

Chenier Plain (Ocean View to Hackberry Beaches)

Total marsh habitat in the western Chenier Plain remained relatively constant from 1998 to 2005. Increased 

beach and marsh habitat between Holly and Constance Beaches between 2001 and 2004 were likely directly attributable 

to restoration efforts here. Reduced marsh and beach habitat acreages in 2005 were attributed to the passage of Hurricane 

Rita (Fearnley, Brien, and others, 2009d). 

THEME 6: Future Goals of the BICM Program

To more effectively identify the magnitude, rates, and processes of shoreline change, a barrier-island 

comprehensive monitoring program (BICM) was developed as a framework for a coast-wide monitoring effort. A 

significant component of this effort includes documenting the historically dynamic morphologic evolution of the 

Louisiana nearshore, shoreline, and back-barrier environments. This aspect of the program is designed to complement 

other project-specific monitoring programs that are currently underway through the support of agencies such as CPRA and 

USACE. 

In contrast to project-specific monitoring efforts, the BICM project provided more comprehensive, regionwide datasets. The methodologies developed under the BICM project allow efficient and accurate integration of historic 

and current datasets and provide a baseline that can be used in future assessments. This project provided long-term 

morphological data for all of Louisiana’s barrier islands and mainland shorelines, rather than just those islands and 

areas that are slated for coastal restoration projects or have had construction previously completed. In addition, BICM 

specifically provided a larger proportion of unified, long-term datasets that will be available to monitor construction 

projects, plan and design future barrier-island projects, develop operation and maintenance activities, and assess the range 

of impacts created by past and future tropical storms. The development of coastal models, such as those quantifying 

littoral-sediment budgets, and a more advanced understanding of the mechanisms forcing coastal evolution become 

increasingly feasible with the availability of the BICM datasets. These factors constitute critically important elements of 

any effort that is aimed at effective coastal restoration, sediment nourishment, or management.

The intent of this theme is to provide guidance for developing a continuation of the BICM program based on 

results of BICM Phase 1, to outline an ongoing monitoring program, and to develop tools that can be readily applied 

by the end users. The original BICM program objectives remain unchanged (see Introduction) and are incorporated in 

the proposed future BICM efforts. Feedback and assessment of the initial phase of the BICM program indicates it has 

advanced coastal science and provided baseline data that will directly influence coastal management practices. The 

continuing program can fill in gaps and enhance its value with future monitoring that includes broader aspects of the 

physical environment. Additionally, the timing of data collections should be staggered to better utilize resources and 

enhance data collection. 

BICM Program Summary Report: Data and Analyses 2006 through 2010
73

Future BICM Monitoring

Semi-Decadal and Annual-Scale Monitoring of BICM Regions

The initial BICM program established four geologic regions of the Louisiana coastal zone: Pontchartrain Basin, 

Mississippi River Delta Plain, Acadiana Bays, and the Chenier Plain. These regions would be monitored on a 5-year 

rotating basis, with measurement of physical parameters such as habitat type, topography and bathymetry, subsidence 

rates, and shoreline change. Presently, there are data gaps (for example, the Acadiana Bays region has very limited data), 

and additional efforts need to be focused in these areas to complete the comprehensive dataset. Several options may be 

considered: (1) revisiting each of the four geologic regions every 5 years on a rotating schedule until evaluation of the 

data collection determines optimum schedules that efficiently utilize resources and funding; (2) collecting all data for a 

geologic region simultaneously and rotating on a 5-year basis; or (3) collecting all of one data type in a single year (for 

example bathymetry or lidar) so that annual remobilization is not necessary. Scheduling data collection following storm 

impacts and to evaluate restoration and construction projects (such as at Shell Island and Whiskey Island) should also be 

considered and should be integrated with adaptive-management plans. 

On an annual basis, coverage of the barrier shorelines (for example., Raccoon Point to Sandy Point and the 

Chandeleur Islands) would be targeted to quantify shoreline and seafloor change. These annual geophysical profiles would 

reoccupy select, evenly spaced, BICM baseline data but at an increased survey trackline spacing. This approach would not 

provide the coverage necessary to produce a surface model, as provided by the baseline and semidecadal-scale surveys, 

but would efficiently quantify the nearshore processes that drive barrier-island evolution in Louisiana, including annual 

storm impact. Reoccupying survey transects allows for direct comparison to quantify short-term trends in shoreface 

profiles and sediment dynamics. Quantifying these short-term rates and identifying their role in long-term evolution 

are critical for barrier-island-restoration project design, site selection, identification of sand sources and sinks, life-span 

predictions, and post-construction monitoring. The annual surveys would also characterize short-term change due to 

winter cold fronts and tropical storms.

Proposed Data Collection

The BICM program is a data-collection effort. Data collection and data products could be based on BICM 

protocols that have been developed through user comments, workshops, and planning meetings. Data collections 

emphasized here are primarily a continuation of established methods developed during existing BICM studies and 

suggested modifications. The different types of data collections listed below provide specific individual datasets, but when 

used in combination, a broader holistic view of the Louisiana coastal system can be developed.

(1) Barrier-Island Habitat Assessment: Oblique aerial photography and video could be used to document 

shoreline conditions, habitat type, and changes due to impacts from hurricanes and seasonal storms.

(2) Shoreline Change Assessment: Imagery (for example, Digital Orthophoto Quarter Quads (DOQQ’s), Color 

Infrared (CIR) aerial photography or Digital Globe QuickBird satellite imagery) and lidar have been and 

could be used to monitor Louisiana shoreline-change rates. Assessment of the rates of shoreline change over 

time should drive planning for future aerial-photography surveys.

(3) Bathymetry: Changes in coastal bathymetry are critical to monitoring the impacts of tropical and seasonal 

storms, changes in sediment-transport patterns, and impacts of restoration efforts. The success of the initial 

BICM bathymetric surveys indicates that future surveys could be expanded to include additional innershelf and shoreline areas to provide the same management support to a broader region. Rates of change and 

impacts of storm events should drive the frequency of surveys. The near-surface geologic framework in these 

areas could also be characterized to determine the influence of the topography on coastal change.

(4) Topography: Barrier-island and shoreline elevations are critical for monitoring rates of changes in 

geomorphic features and sediment volumes. Lidar surveys are the most efficient and cost-effective datacollection method for this task. Lidar and bathymetric surveys could be coordinated to share resources, 

provide accurate integration, and enhance modeling efforts.

THEME 6: Future Goals of the BICM Program
74

(5) Habitat: Continued habitat-classification analysis is critical to monitoring the impacts of relative sea-level 

rise, storms, restoration, and coastal-planning activities. 

(6) Sediment Characterization: Changes in sediment character are typically an indicator of change in sediment 

transport and budget. Monitoring the coastal-sediment character in the BICM regions is crucial to evaluating 

restoration-project performance in addition to changes to unaltered systems.

(7) Subsidence: Monitoring of local subsidence rates will provide local rates of sea-level rise and establish 

elevation response to construction projects as opposed to natural changes. The need to incorporate local 

subsidence rates into restoration-project metrics has been identified and integrated into the Louisiana Coastal 

Master Plan (Beck and others, 2012). It is critical to identify the rate of subsidence in each BICM region and 

along each shoreline.

Technology Advances 

Because data collection and processing are the primary activities of BICM, using the best and most current 

technologies should be an important objective. For example, technological advances in topographic and bathymetric 

data-collection and processing techniques, resolution, equipment, and software could be reviewed and applied to enhance 

monitoring and coastal-management practices. This would also hold true for all data collected (coastal imagery, lidar, 

habitat type). However, since the objective of the BICM program is to monitor change over time, baseline protocols and 

datums need be adhered to so that the datasets remain comparable.

Standardization of Methods and Quality Control

Standardization of methods would provide guidance and coordination that assures that all data collected under 

BICM efforts and by project-specific studies are conducted under a uniform set of standards so that they are comparable 

and complimentary. This would include, but is not limited to, data-collection locations and datums, precision of 

instrumentation/systems that are used for data collection, methodology/calibration techniques, and uncertainty analysis/

quality control. Data-collection planning, processing, and analysis could be overseen by a single entity to ensure 

uniformity and consistency with established standards. BICM-type datasets that are collected by other agencies or under 

project-specific objectives outside of BICM (for example, LCA or CWPPRA coastal-management projects) could be 

processed and incorporated into the more regional and longer-term monitoring efforts expected of the BICM program. 

Since the completion of this phase of BICM in 2010, CPRA has developed protocols for geophysical data acquisition that 

aids consultants to collect data in a uniform manner for inclusion into the Louisiana Sand Resources Database (LASARD) 

(Syed Khalil, oral commun., 2012).

External Considerations

The BICM program, as implemented, is primarily a data-collection and synthesis effort to monitor coastal change 

in specific regions of Louisiana. Several considerations, while not under BICM responsibilities, should be promoted to 

other projects and partners.

Establishment of Hydrodynamic Monitoring Stations

Monitoring stations that record wave, current, water level, salinity, temperature, and other such data statistics 

could be established at key locations including barrier-shoreface and proximal back-barrier environments and at tidal 

inlets. These data are critical for quantifying and modeling regional processes along the sandy shorelines and can provide 

information for external projects that in turn can contribute analysis and results to the BICM program. These stations 

would complement or be incorporated into the existing CRMS-Wetlands stations and future CRMS-Water stations as well 

as existing stations offshore (Wave-Current-Surge Information System for Coastal Louisiana [WAVCIS] and National 

Ocean Service [NOS]).

BICM Program Summary Report: Data and Analyses 2006 through 2010
75

Development of Barrier-Island Value Assessment Model

The goal of this task would be to develop an assessment tool that would replace or augment existing models (for 

example, Wetland Value Assessment [WVA]) presently used to quantify changes in habitat quality and quantity that are 

predicted as a result of proposed barrier-island-restoration projects. Based on findings in the BICM project and in previous 

studies along the Louisiana barrier islands, the existing WVA barrier-island and barrier-headland models do not consider 

some of the most critical barrier-island-system habitats (for example, marine submerged aquatic vegetation, back-barrier 

platform, barrier shoal, and submerged-spit platforms) and processes. Moreover, existing models put a priority on total 

area created as a result of the project and do not consider sediment volume or strategic placement of sediment that 

might provide increased island area in subsequent years post-construction due to natural sediment-transport trends, tidal 

processes, and aeolian processes. This tool would consider the unique morphodynamics of sandy barrier-island systems 

(including subsurface stratigraphy) for quantifying projected changes as a result of project construction and projected 

changes without construction and would allow for development of best practices and management for restoration. 

Data Management and User Tools

A clear data-management system could be established that would allow researchers collecting and processing 

the data to seamlessly upload materials from offsite portals, archive data at various stages of development, and develop a 

template-based system to automatically generate end products to identical standards. This system would also be designed 

so that end users can efficiently obtain the data (temporally and spatially) as required for their specific missions from Webbased portals. This structure would also allow information to be accessed quickly and comprehensively for emergency 

response to natural and manmade disasters.

Discussion of Louisiana Coast-Wide and Topical Themes
76

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