Path 24

Path 23

Path 22

Path 21

EXPLANATION

Modified Coastal Zone Boundary: 14,587 mi2

Domain shown: 22,895 mi2

Landsat Worldwide Reference System-2 (WRS-2)

Excluded from domain (shown for reference purposes only)

Uplands (>10m) 

Uplands (>10m) 

New Orleans

Mississippi

Louisiana

Texas

Louisiana

Cameron

Lake Pontchartrain

Big

 Mar

Lake Maurepas

Lake Salvador

Barataria Bay

Timbalier Bay

Terrebonne Bay

Caillou Lake

Lake

 Mechant

Lake

 Boudreaux

Little Lake

Atchafalaya Bay

Gulf of Mexico

Lake Cataouatche

Atchafalaya

River

Lake Borgne

East Cote 

Blanche Bay

West Cote 

Blanche Bay

Vermilion Bay

White Lake

Grand Lake

Calcasieu

Lake

Black

 Lake

Freshwater Bayou

Wax Lake Outlet

Marsh

Island

 Lake PontchartrainCauseway

Gulf Intracoastal Waterway

Gulf Intracoastal Waterway

Gulf Intracoastal Waterway

Mississippi River-Gulf Outlet Canal

Mississippi River

Mississ

pi pi R vi er

Mississippi River

Southwest Pass

South Pass

Pass a Loutre

East Bay

West Bay

Garden

Island 

Bay

Bayou Lafourche

Labranche wetlands

Calcasieu Ship Channel

Sweet

 Lake

Breton Sound

Lake

Felicity

Gulf of Mexico

Gulf of Mexico

Calcasieu-Sabine Basin

Chandeleur Sound

C

h

a

n

d

ele

ur Isla

n

d

s

Teche-Vermilion 

Basin

Atchafalaya 

Delta Basin

Terrebonne Basin

Barataria Basin

Mississippi River 

Delta Basin

Breton Sound

Basin

Pontchartrain

Basin

Lac des 

Allemands

Uplands (>10m)

Uplands (>10m)

Uplands (>10m)

Uplands (>10m)

Gulf of Mexico

Hackberry

Johnsons Bayou Grand Chenier

Wax Lake Delta

Atchafalaya Delta

Morgan

City

Intracoastal

City

Pecan

Island

Houma

Thibodaux

Golden

Meadow

Port Fourchon

Larose

Montegut

Dulac

Theriot

Amelia

Cut Off

Lake Charles

Sulphur

Vinton

Iowa Welsh

Jennings

Crowley

Rayne

Lafayette

New Iberia

Jeanerette

Abbeville

Franklin

Donaldsonville

White 

Castle

Plaquemine

Port Allen Baton Rouge

Slidell

Mandeville

Covington

Ponchatoula

Gonzales

Lake 

Verret

Lake 

Palourde

Flat

Lake 

Lake 

Fausse Pointe

The 

Pen

Breaux Bridge

Redfish 

Bay

Blind

Bay

Quarantine

Bay

Adams

Bay

Bastian

Bay

Lost Lake Four League

Bay

Bayou Perot

Bayou Rigolettes

Grand

Lake

Lake De Cade

Lake

Saint Catherine

Sabine

Lake

Mermentau Basin

Lake Lery

Scale 1:265,000

10 5 0 10 20 30 40

Kilometers

10 5 0 10 20 30 40

Miles

Uplands5

Persistent forested wetland5

Persistent water

Persistent wetland5

Basin boundary

1

Gain is determined by the last date a particular pixel transitioned from water 

 to land and remained land throughout the period of observation.

2

Loss is determined by the last date a particular pixel transitioned from land 

 to water and remained water throughout the period of observation.

EXPLANATION

1977–85 land gain1,4

1932–56 land gain1

1956–73 land gain1,4

1973–75 land gain1,4

1975–77 land gain1,4

1990–95 land gain1

1985–88 land gain1

1988–90 land gain1

2004–6 land gain1

1995–98 land gain1

1998–99 land gain1

1999–2002 land gain1

1977–85 land loss2,4

1932–56 land loss2

1956–73 land loss2,4

1973–75 land loss2,4

1975–77 land loss2,4

1990–95 land loss2

1985–88 land loss2

1988–90 land loss2

2004–6 land loss2

1995–98 land loss2

1998–99 land loss2

1999–2002 land loss2

2006–8 land gain1

2008–9 land gain1,3

2006–8 land loss2

2008–9 land loss2,3

Developed5

3

Because this date range has only one ending dataset, some of these effects 

 may be temporary phenomena.

4

This date range contains at least one date in which the land/water data were 

 created from Landsat Multispectral Scanner System (MSS). 

2002–4 land gain1

2002–4 land loss2

5

Land cover categories based on 2008 data. “Persistent” is defined as not 

 having undergone a consistent change in land/water category during the 

 observation period.

2009–10 new land1,3

2009–10 new water2,3

Uplands5

Persistent forested wetland5

Persistent water

Persistent wetland5

Developed5

Background imagery

(outside modified Coastal 

 Zone Boundary)

Background imagery 

(inside modified Coastal 

 Zone Boundary)

Scientific Investigations Map 3164

Pamphlet accompanies map

U.S. Department of the Interior 

U.S. Geological Survey 

By Brady R. Couvillion, John A. Barras, Gregory D. Steyer, William Sleavin, Michelle Fischer, Holly Beck, Nadine Trahan, Brad Griffin, David Heckman

Land Area Change in Coastal Louisiana (1932 to 2010) 

Image source:

Analyses presented utilized imagery 

from Landsat Multispectral Scanner 

System (MSS) and Thematic Mapper 

(TM) satellites. Landsat imagery is

provided by the USGS Center for

Earth Resources Observation and

Science (EROS).

The background image depicts data 

from Landsat TM that are classified 

by types of land and water coverage.

Suggested citation:

Couvillion, B.R.; Barras, J.A.;

Steyer, G.D.; Sleavin, William;

Fischer, Michelle; Beck, Holly;

Trahan, Nadine; Griffin, Brad; and 

Heckman, David, 2011, Land area 

change in coastal Louisiana from 

1932 to 2010: U.S. Geological Survey 

Scientific Investigations Map 3164, 

scale 1:265,000, 12 p. pamphlet.

See pamphlet for references cited.

Publishing support provided by 

USGS Lafayette Publishing 

Service Center

Introduction

The U.S. Geological Survey (USGS) analyzed landscape changes in coastal Louisiana by determining land and water classifications for 17 datasets. 

These datasets include survey data from 1932, aerial data from 1956, and Landsat Multispectral Scanner System (MSS) and Thematic Mapper (TM) data 

from the 1970s to 2010. Previous studies have analyzed land change in coastal Louisiana, but many are out of date, provide data for limited time periods, 

or lack the temporal frequency necessary to provide information about when the loss occurred. The purpose of this study is to provide updated estimates 

of persistent land change and historical land change trends for coastal Louisiana and for each hydrologic basin, as defined by the Coastal Wetlands 

Planning, Protection and Restoration Act Program (n.d.), for the 1932–2010 period of record. The use of 17 datasets plus the application of consistent 

change criteria in this study provide opportunities to better understand the timing and causal mechanisms of wetland loss that are critical for forecasting 

landscape changes in the future.

Methodology

This study analyzed changes in the extent of land in coastal Louisiana by using 17 datasets summarizing land and water areas from 1932 to 2010 

(table 1). The datasets were derived from multiple sources including (1) historical survey data (1932); (2) National Wetlands Inventory (NWI) data based 

on aerial photography (1956); (3) Landsat Multi-Spectral Scanner (MSS) data (1973–79); and (4) Landsat Thematic Mapper (TM) satellite imagery 

classified into land and water categories (1985–2010). Variable data coverage among the 1932 and 1956 datasets and all subsequent data required an 

assumption of no change in the area of no data coverage (areas with no overlap) in those datasets. No change is assumed in land area from 1932 to 1956 

and from 1956 to 1973 in portions of the dataset that occur outside the boundaries of the 1932 and 1956 data coverage. (Refer to figure 1 for more 

information regarding the areas within the coastal basins to which this assumption was applied.)

The areas missing from the 1932 and 1956 datasets mostly consist of forested wetlands. These areas are historically stable, so the assumption of “no 

change” is correct in most instances; however, the area and change summaries should only be used with an in-depth understanding of the impacts of this 

assumption in areas where there are no data in 1932 and 1956.

Preprocessing of all datasets included use of ERDAS IMAGINE AutoSync (ERDAS Inc., Norcross, Ga.), a software that uses an automated process 

to align common landform features between images. To assess change, the geometric registration between datasets must be highly accurate. Misalignment 

of features at the same location could produce invalid land change results. This processing step was critical in ensuring that the 1932 and 1956 data 

aligned with the later satellite-based data. The Landsat MSS data (1973, 1977, and 1979), which have a native 60-meter (m) resolution, were first 

resampled to a 30-m resolution by using a cubic convolution resampling method to facilitate comparability with later Landsat TM-based data (native 30-m 

resolution). Conducting this resampling prior to land-water classification is more appropriate than resampling the results of the land-water classification. 

All satellite imagery data were then classified into land/water categories by using a standard methodology similar to that used in previous studies (Barras, 

2006, 2007; Barras and others, 2008).

The methodology used in this study relied heavily on the use of the near infrared band of Landsat data (MSS: Band 7; TM: Band 5) in the early 

stages of classification. Near infrared (NIR) was selected because the wavelengths in this range, 1.55–1.75 micrometers, are particularly informative and 

discriminatory with regard to land and water categories. Supervised and unsupervised classification was then used to account for areas that may be 

incorrectly classified by the NIR band alone. Areas that need further attention for accurate classification commonly include highly turbid water areas 

and floating aquatic vegetation. These areas were manually recoded to their appropriate land/water categories by expert analyses.

Land Area Changes 

The resulting land area data were summarized by time period and by basin (table 1 and fig. 2). These analyses show that coastal Louisiana has 

experienced a net change in land area of approximately -1,883 mi2 from 1932 to 2010. Land area estimates can vary substantially because of 

environmental variations such as seasonality and, most notably, water-level variations on the date of acquisition (DOA) of the data (Morton and others, 

2005; Bernier and others, 2006). (Refer to table 2 for more information regarding the water levels on the DOA for the data used in these analyses.) To 

reduce some of the errors associated with apparent land change caused by misclassification or transient environmental phenomena, two approaches were 

utilized. Changes must persist for at least two time periods (of variable length, depending upon availability of cloud-free imagery) following the initial 

change, and anomalous changes among land and water categories can only occur in less than 20 percent of the remaining datasets. The mapped dataset 

identifies only these areas of persistent and consistent change (table 3; figs. 3 and 4). For this reason, recent land changes (2008–9 and 2009–10) cannot 

yet be defined as persistent because data are not available to confirm that these changes have persisted into the two following analysis periods. These 

unconfirmed changes are instead referred to as “new land investigation areas” and “new water investigation areas” (figs. 3 and 4). 

It is important to note that there is a difference between net land area change (table 1 and fig. 1) and persistent losses and gains (table 3, figs. 3,4). 

As classification of an area as loss or gain depends upon persistence criteria, the amount of area of persistent loss or gain for a particular period can be 

less than or greater than the net land area change for that period. This occurs because persistent losses in a particular location can be offset by transitory 

gains in another.

Land Change Trends

Land change trends by hydrologic basin within the modified coastal zone were calculated solely on the basis of Landsat TM data for 

1985–2010 (figs. 5 and 6). Linear regressions were calculated for two time periods, 1985–2004 and 1985–2010, because strong hurricanes in 

2005 (Katrina and Rita) and 2008 (Gustav and Ike) greatly impacted both eastern and western coastal Louisiana wetlands. Results show that the 

Atchafalaya Delta Basin is the only area in coastal Louisiana showing increasing land area (positive land change slope), but the rate of growth 

in this one basin is not sufficient to offset the losses coastwide, particularly in years of increased hurricane activity. The 2005 and 2008 datasets 

were excluded to reduce the influence of transitory storm effects. The variability in land area data points around the slope illustrates the 

influence of various sources of environmental variance or classification error.

Discussion and Conclusions

This assessment provides a comprehensive analysis of historical trends and rates of land area change in coastal Louisiana. The primary 

improvement over past efforts is an increased temporal frequency of analysis. This gives scientists the ability to better quantify the amount of wetland 

loss and the time period in which it was lost. Having this information can allow gradual loss patterns to be distinguished from losses due to episodic 

events such as hurricanes. The spatial and temporal patterns observed reveal a dynamic landscape changing as a result of the complex and often 

interactive effects of natural and human-induced processes.

Variability in land area estimates can often be attributed to temporary wind and water level fluctuations present at the date and time of acquisition 

of the aerial and satellite imagery. Morton and others (2005) found that water area varied by as much as 5 percent over short time periods, largely as the 

result of environmental variability. The 17 dates of imagery analyzed provide a more robust estimate of change by reducing the inclusion of land area 

fluctuations caused by environmental variability.

 The desire to reduce errors associated with environmental variability was a driving force behind the development of the persistence criteria 

utilized in this analysis. An area must experience a change in land/water category, and that change must persist for at least two time periods following the 

initial conversion before that area is classified as “loss” or “gain”. The temporal resolution, as well as the persistence criteria used in this analysis, ensures 

that the data presented are more likely to represent permanent changes compared to previous studies; however, it is important to note when examining 

wetland loss/gain by time period that wetland areas often fluctuate between land and water categories. These fluctuations can take place for multiple time 

periods prior to a persistent conversion of an area from land to open water or, conversely, from open water to land. 

Consequently, loss that is shown to have occurred in a specific time period may have begun that transition in an 

earlier period. Initial losses often recover temporarily, only to be lost again because of a secondary or compound 

stressor. With the exception of anomalies, this assessment documents the last time period in which the persistent 

conversion occurred as opposed to the first time a change was documented. 

These analyses have shown that episodic events, such as hurricanes and other extreme storms, have 

contributed significantly to coastal land loss, particularly in recent years. Annual rates of coastal land loss for 

1985 to 2010 (-16.57 ± 3.26 mi2

/yr) increased by approximately 4.8 mi2/year relative to the 1985 to 2004 trends 

(-11.76 ± 4.47 mi2/yr), reflecting hurricane-induced acceleration of coastal land loss. This is consistent with 

previous analyses described in Barras and others (2008). In addition to the immediate loss caused by direct 

physical impacts, hurricanes have been observed to induce excessive plant stress, such as from storm-driven 

elevated salinity and sulfides (Steyer and others, 2010), which has been suggested to contribute to future wetland 

losses. This analysis has shown areas that were not immediately observed as loss following a particular storm’s 

landfall, but those areas began to consistently appear as water several months later. Storm-induced stress likely 

contributed to at least some of the observed losses.

Excluding the high rates of wetland loss due to recent hurricanes, rates of wetland loss had been decreasing 

from the high rates observed in the 1970s. Britsch and Dunbar (1993) observed a similar trend of decreasing loss 

after 1978. Though the wetland loss in coastal Louisiana is a dire situation, this observed decrease is at least a 

measured source of positive news, as past trends are often indicative of potential future losses.

An interesting finding of this analysis may be observed in the increase in net land area in the 2009 and 2010 

datasets, as seen in figure 2. Though it may be intuitive to interpret this land area increase as recovery from the 

low, hurricane-influenced land area estimates of 2008, the potential influence of environmental variability dictates 

caution before interpreting this pattern as “recovery.” Discriminating the permanence of these increases from the 

transitory effects of environmental variability may require several additional years of observations. 

The temporal frequency of land change 

provided by this study is allowing scientists to 

further investigate the causal mechanisms of the 

loss which has occurred. These investigations 

will provide improved information to develop 

tools to monitor ecosystems, forecast possible 

impacts, and plan protection and restoration 

activities. These data can help support the 

development of strategies to adapt to our 

changing environment.

Table 1. Land area in coastal Louisiana by basin, as defined by the Coastal Wetlands Planning, Protection and Restoration Act Program (n.d.) , 1932–2010.

[Land area in square miles. Dates are approximate averages of imagery used for various portions of the coast. 

date of acquisition of the imagery. Refer to table 2 for water level information]

Decimal date1 Basin

Atchafalaya 

Delta

Barataria Breton Sound CalcasieuSabineMermentau Mississippi 

River Delta

Pontchartrain TecheVermilionTerrebonne Coastwide

19322 212.58 1,479.78 427.63 824.99 958.27 262.07 1,105.19 548.94 1,726.48 7,545.92

19562 197.57 1,382.60 376.07 810.52 918.78 241.82 1,038.25 520.24 1,618.43 7,104.28

1973.9 197.04 1,339.06 395.08 691.40 888.94 80.34 1,029.61 529.78 1,598.43 6,749.68

1975.7 210.52 1,224.77 347.76 697.76 902.95 94.27 999.08 528.12 1,529.68 6,534.90

1977.4 190.51 1,297.88 356.49 591.98 799.89 138.71 993.72 500.33 1,396.13 6,265.65

1985.1 186.80 1,149.74 333.87 615.44 780.54 121.63 979.22 492.36 1,325.53 5,985.12

1988.1 205.89 1,170.51 339.86 636.36 785.76 129.06 991.19 487.43 1,393.58 6,139.65

1990.8 198.92 1,104.10 313.00 659.23 835.71 137.99 970.87 477.91 1,322.58 6,020.31

1995.7 225.18 1,026.72 292.17 637.31 849.77 136.91 934.51 476.86 1,263.14 5,842.57

1998.2 180.94 1,092.40 313.33 596.14 738.04 114.04 961.99 484.70 1,266.84 5,748.43

1999.9 231.23 1,055.72 300.26 644.40 834.03 152.01 946.91 489.33 1,270.68 5,924.58

2002.2 211.68 1,082.12 304.58 629.88 781.19 133.59 944.58 485.88 1,294.11 5,867.61

2004.9 218.90 1,048.56 295.87 654.05 816.48 119.02 936.71 474.31 1,253.01 5,816.89

2006.8 213.99 1,035.94 264.10 625.14 731.29 105.98 912.33 477.43 1,241.69 5,607.89

2008.8 203.15 1,016.36 240.40 580.23 727.70 113.74 900.98 464.57 1,204.62 5,451.75

2009.8 219.35 1,010.85 242.50 568.86 731.03 108.69 903.23 470.82 1,204.45 5,459.78

2010.8 229.31 1,024.19 253.40 611.42 803.09 138.03 910.96 471.57 1,220.73 5,662.71

1

Decimal dating is a more specific dating system than the calendar year and is used to facilitate statistical analyses. It is derived by dividing the day of the year (in the Julian system) by the number of days in the year. 2

Calendar dates were not available.

2 1956 assumes no change from 1956 to 1973 in 920 mi2

 of coastal Louisiana.

1 1932 assumes no change from 1932 to 1956 in 1,115 mi2

 and no change from 1932 to 1973 in 577 mi2

of coastal Louisiana.

3 Datasets are based on Landsat Multispectral Scanner System (MSS) data, which are originally at 60-m resolution.

7,722

7,529

7,143

7,336

6,950

6,757

6,564

6,371

6,178

5,985

5,792

5,598

5,405

Coastal Louisiana land area, in square miles

1930 1940 1950 1960 1970 1980 1990 2000 2010

Year

1

2

3

3

3

Figure 2. Land area in coastal Louisiana, 1932–2010. Coastwide,

net land area decrease from 1932 to 2010 was 1,883 mi2

. (See table 1 for

specific area measurements.)

Table 2. Water levels at a selected gage (station ID: 8761724, located near Grand Isle, La.) on the date of acquisition for 

imagery used in the land area estimates.

Path 211 Path 221 Path 231 Path 241

Decimal

 date2

Calendar

date

Gage height, 

in feet3

Calendar

 date

Gage height, 

in feet3

 Calendar

date

Gage height, 

in feet3

 Calendar

 date

Gage height, 

in feet3

19324 Not available Not available Not available Not available

19564 Not available Not available Not available Not available

1973.9 12/5/1973 Not available Not available Not available Not available

1975.7 10/11/1975 Not available Not available Not available Not available

1977.4 7/2/1977 Not available 6/3/1977 Not available 1/23/1977 Not available 4/6/1977 Not available

1985.1 10/11/1985 6.79 1/19/1985 5.81 1/26/1985 5.94 12/3/1985 6.30

1988.1 12/4/1987 6.46 1/28/1988 5.02 12/2/1987 6.33 1/26/1988 5.97

1990.8 2/14/1991 5.97 11/1/1990 6.56 11/24/1990 6.40 10/30/1990 6.69

1995.7 10/7/1995 6.89 9/28/1995 6.86 10/5/1995 6.92 9/10/1995 6.82

1998.2 2/17/1998 6.04 2/24/1998 5.64 3/3/1998 6.14 3/10/1998 6.17

1999.9 11/27/1999 6.36 11/18/1999 6.46 11/16/1999 6.50 10/24/1999 6.73

2002.2 1/3/2002 6.00 2/27/2002 5.45 2/2/2002 5.97 1/8/2002 6.00

2004.9 10/15/2004 6.76 11/7/2004 6.46 10/13/2004 6.79 11/5/2004 6.59

2005.8 10/18/2005 6.73 10/25/2005 6.10 10/16/2005 6.66 10/23/2005 6.69

2006.8 1/25/2007 5.97 10/28/2006 6.53 11/4/2006 6.66 12/13/2006 6.23

2008.8 10/26/2008 6.82 10/1/2008 6.89 10/8/2008 6.89 9/29/2008 6.89

2009.8 11/14/2009 6.66 11/5/2009 6.69 11/12/2009 6.66 11/3/2009 6.73

2010.8 10/16/2010 6.53 10/7/2010 6.30 10/14/2010 6.36 10/5/2010 6.86

1

Refer to figure 1. These “path” designations correspond to the Landsat Worldwide Reference System-2 (WRS-2) tiling system.

2

Decimal dating is a more specific dating system than the calendar year and is used to facilitate statistical analyses. It is derived by dividing the day of the year (in the Julian system) 

 by the number of days in the year.

3

Elevations provided in station datum.

4

Calendar dates were not available.

4/15/1975

2/3/1973

9/25/1975

12/7/1973

9/26/1975

12/9/1973

Table 3. Persistent land loss and land gain in coastal Louisiana by basin, as defined by the Coastal Wetlands Planning, Protection and Restoration Act Program (n.d.) , 1932–2010.

[Land area in square miles]

Basin 1932–56 1956–73 1973–75 1975–77 1977–85 1985–88 1988–90 1990–95 1995–98 1998–99 1999–2002 2002–4 2004–6 2006–8 2008–9 2009–10

Total 

persistent

Loss Loss Negative change

Atchafalaya Delta -4.48 -1.92 -1.75 -0.90 -0.64 -0.99 -1.37 -1.15 -0.83 -0.49 -0.39 -0.51 -0.37 -0.66 -0.01 -0.02 -16.49

Barataria -56.46 -70.98 -64.21 -27.94 -42.81 -16.80 -26.30 -26.76 -16.76 -17.83 -9.12 -8.95 -13.76 -15.86 -3.94 -3.23 -421.71

Breton Sound -30.94 -11.34 -9.95 -9.58 -7.97 -5.67 -8.28 -9.64 -6.93 -6.47 -4.26 -5.48 -29.32 -12.25 -0.98 -1.79 -160.87

Calcasieu-Sabine -8.41 -66.70 -17.30 -15.08 -9.59 -6.19 -4.22 -6.90 -7.15 -5.19 -2.85 -1.59 -22.00 -23.74 -1.30 -0.72 -198.94

Mermentau -18.68 -24.35 -7.00 -9.31 -10.01 -6.59 -5.49 -6.58 -5.74 -3.96 -4.03 -2.76 -22.26 -6.13 -0.43 -0.60 -134.37

Mississippi River Delta -34.06 -61.93 -10.51 -9.61 -4.86 -2.44 -5.64 -4.41 -1.89 -1.02 -1.02 -3.46 -10.11 -0.90 -0.14 -0.03 -152.02

Pontchartrain -34.41 -32.50 -12.74 -12.84 -9.47 -6.88 -9.67 -11.07 -7.85 -6.68 -4.20 -5.70 -15.14 -7.24 -1.26 -1.60 -179.25

TecheVermilion -14.68 -8.40 -4.43 -4.22 -3.06 -3.23 -3.23 -2.81 -3.57 -3.15 -1.71 -3.23 -3.78 -4.51 -0.29 -0.29 -64.61

Terrebonne -75.28 -46.25 -45.65 -50.87 -35.11 -22.97 -27.54 -30.63 -23.12 -22.50 -11.99 -9.63 -18.27 -23.40 -12.31 -4.49 -459.99

Total -277.41 -324.39 -173.55 -140.35 -123.52 -71.78 -92.18 -99.94 -73.83 -67.29 -39.57 -41.30 -135.02 -94.69 -20.65 -12.77 -1,788.241

Basin 1932–56 1956–73 1973–75 1975–77 1977–85 1985–88 1988–90 1990–95 1995–98 1998–99 1999–2002 2002–4 2004–6 2006–8 2008–9 2009–10

Total 

persistent

Gain Gain Positive change

Atchafalaya Delta 0.89 1.12 0.63 0.32 1.77 1.17 0.60 2.47 0.76 4.74 0.98 1.12 2.28 2.08 3.77 5.25 29.95

Barataria 1.11 0.10 0.05 0.45 0.24 0.05 0.08 0.15 0.29 0.09 0.30 0.31 1.25 0.58 0.35 0.52 5.91

Breton Sound 1.34 0.32 0.01 0.12 0.20 0.06 0.16 0.14 0.38 0.20 0.31 0.27 1.15 0.59 0.29 0.49 6.03

Calcasieu-Sabine 1.87 1.68 0.18 0.26 0.74 0.19 0.19 0.57 0.20 0.28 0.40 0.86 0.81 0.51 0.08 0.19 9.02

Mermentau 1.71 0.57 0.12 0.10 0.28 0.13 0.53 1.16 0.70 0.18 0.33 0.28 0.44 0.19 0.04 0.11 6.87

Mississippi River Delta 2.43 0.50 0.95 2.34 2.52 1.10 1.06 0.67 0.83 1.62 1.43 0.63 2.62 2.52 0.37 2.16 23.74

Pontchartrain 1.59 1.69 0.61 0.17 0.30 0.16 0.28 0.20 0.16 0.07 0.32 0.30 1.11 0.64 0.27 0.46 8.31

TecheVermilion 1.64 0.34 0.01 0.04 0.13 0.05 0.05 0.16 0.09 0.10 0.12 0.14 0.51 0.24 0.13 0.11 3.85

Terrebonne 2.96 0.21 0.25 0.31 0.49 0.26 0.24 0.28 0.40 0.76 0.47 0.37 1.67 0.67 0.66 0.43 10.42

Total 15.53 6.52 2.82 4.10 6.68 3.17 3.21 5.79 3.80 8.03 4.66 4.27 11.82 8.03 5.95 9.71 104.111

1

Data are rounded to two decimal places; values shown may not add to totals shown.

Figure 3. Persistent land loss and land gain in coastal Louisiana by 

period for 1932–2010.

*

As persistence of these changes cannot yet be determined, these areas are coined “new water investigation areas” 

 and “new land investigation areas.” These are areas under investigation for persistence of the changes observed.

-325

-300

-275

-250

-225

-200

-175

-150

-125

-100

-75

-50

-25

0

25 *

*

 Persistent area change, in square miles

Figure 4. Persistent land loss and land gain across Louisiana by basin (as defined by the Coastal Wetlands Planning, Protection and

Restoration Act Program, n.d.) and period for 1932–2010.

*

*

*

*

*

*

*

*

*

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

-80

-70

-60

-50

-40

-30

-20

-10

0

10

-35

-30

-25

-20

-15

-10

-5

0

5

-70

-60

-50

-40

-30

-20

-10

0

10

-25

-20

-15

-10

-5

0

5

-65

-55

-45

-35

-25

-15

-5

5

-35

-30

-25

-20

-15

-10

-5

0

5

-16

-14

-12

-10

-8

-6

-4

-2

0

2

-80

-70

-60

-50

-40

-30

-20

-10

0

10

*

As persistence of these changes cannot yet be determined, these areas are coined “new water investigation areas” and “new land investigation areas.” These are areas under investigation for persistence 

of the changes observed.

Atchafalaya Delta Basin Barataria Basin Breton Sound Basin 

Calcasieu-Sabine Basin Mermentau Basin Mississippi River Delta Basin 

Pontchartrain Basin Teche-Vermilion Basin 

Terrebonne Basin 

Land area, in square miles

Land area, in square miles

Land area, in square miles

Land area, in square miles

Land area, in square miles

Land area, in square miles

Land area, in square miles

Land area, in square miles

Land area, in square miles

Figure 5. Linear 

regressions of land 

area change trends 

coastwide across 

Louisiana, 1985–2010; 

negative measurements

indicate land loss, while 

positive measurements 

indicate land gain. 

Rates including and 

excluding the effects 

of the hurricanes of 

2005 and 2008 are 

shown for comparison.

1985 1990 1995 2000 2005 2010 2015

5,405

5,791

6,177

6,563

(r 2=

0.7208)

1985–2004 = 0.4969)

(r 2 1985–2010 = =

-11.76 ± 4.47

-16.57 ± 3.26 mi2

/year

Katrina/Rita Gustav/Ike

mi2/year

L

a

n

d

are

a, in square miles

Year

95 percent confidence band, 

 1985–2010

Regression trend line, 

 1985–2010

Regression trend line, 1985–2004

Land area

Excluded data points, 2005–8

EXPLANATION

Atchafalaya Delta Basin

1985 1990 1995 2000 2005 2010 2015

116

154

192

230

268

306

Katrina/Rita Gustav/Ike

(r2 =

0.3909)

1985–2004 = 0.2758)

(r2 1985–2010 = =

1.32 ± 0.81

1.22 ± 0.48 mi2

/year

mi2

/year

Land area, in square miles

Barataria Basin

1985 1990 1995 2000 2005 2010 2015

849

926

1,003

1,080

1,157

1,234

1,311

1,388

Katrina Gustav

Land area, in square miles

Breton Sound Basin

1985 1990 1995 2000 2005 2010 2015

232

309

386

Katrina Gustav

Land area, in square miles

Mermentau Basin

1985 1990 1995 2000 2005 2010 2015

579

676

773

870

967

Rita Ike

Land area, in square miles

Mississippi River Delta Basin

1985 1990 1995 2000 2005 2010 2015

77

115

153

191

Katrina Gustav

Land area, in square miles

Pontchartrain Basin

1985 1990 1995 2000 2005 2010 2015

849

887

925

963

1,001

1,039

Katrina Gustav

Land area, in square miles

Terrebonne Basin

1985 1990 1995 2000 2005 2010 2015

1,081

1,158

1,235

1,312

1,389

1,466

Katrina Gustav

Land area, in square miles

Teche-Vermilion Basin

1985 1990 1995 2000 2005 2010 2015

444

463

482

501

520

Rita Ike

Land area, in square miles

Calcasieu-Sabine Basin

1985 1990 1995 2000 2005 2010 2015

541

618

695

772

Rita Ike

Land area, in square miles

(r2 =

0.7070)

1985–2004 = 0.6033)

(r2 1985–2010 = =

-5.27 ± 1.62

-4.76 ± 0.97 mi2

/year

mi2

/year (r2 =

0.8126)

1985–2004 = 0.6544)

(r2 1985–2010 = =

-1.97 ± 0.54

-2.98 ± 0.45mi2

/year

mi2

/year

Year Year Year

(r 2=

0.1009)

1985–2004 = 0.05010)

(r 2 1985–2010 = =

0.67 ± 1.10

-0.97 ± 0.91mi2

/year

mi2/year (r2 =

0.06836)

1985–2004 = 0.01922)

(r2 1985–2010 = =

0.74 ± 2.01

-1.30 ± 1.52 mi2

/year

mi2

/year

(r2 =

0.03195)

1985–2004 = 0.01624)

(r2 1985–2010 = =

0.22 ± 0.65

-0.29 ± 0.51mi2

/year

mi2

/year

Year Year

Year

(r2=

0.8437)

1985–2004 = 0.7054)

(r2 1985–2010 = =

-2.44 ± 0.60

-2.81 ± 0.38mi2

/year

mi2

/year (r2 =

0.6910)

1985–2004 = 0.5797)

(r2 1985–2010 = =

-4.73 ± 1.52

-4.37 ± 0.92 mi2

/year

mi2

/year (r2 =

0.3774)

1985–2004 = 0.1451)

(r2 1985–2010 = =

-0.32 ± 0.29

-0.45 ± 0.18mi2

/year

mi2

/year

Year Year Year

Land area Excluded data points, 2005–8 Regression trend line, 1985–2004 Regression trend line, 1985–2010 95 percent confidence band, 1985–2010

EXPLANATION

Figure 6. Linear regressions of land area change trends in coastal Louisiana by hydrologic basin (as defined by the Coastal Wetlands Planning, Protection and 

Restoration Act Program, n.d.), 1985–2010; negative measurements indicate land loss, while positive measurements indicate land gain. Rates including and excluding the 

effects of the hurricanes of 2005 and 2008 are shown for comparison.

Figure 1. Map of the study area in coastal Louisiana. The coastal zone boundary was modified to improve the conservation plan boundary. The conservation plan boundary 

delineates the zone for which statistics were calculated and isolates coastal regions while excluding fastlands (defined as developed, agricultural, and other protected areas) 

from statistical analysis of coastal land change. Of particular note are the areas of non-overlapping data coverage in the 1932 and 1956 datasets (based on survey and aerial data) 

and in the 1973–2010 datasets (based on satellite imagery data). Because no data exist for these non-overlapping areas, an assumption of no change in those areas has been used 

for those time periods in the analyses (a reasonable assumption since a majority of these data voids occurs in areas dominated by forested wetlands, a habitat type known to have 

been particularly stable in past observations). The background image is shown for reference purposes to a northern boundary delineated by the 10-m elevation contour 

(referenced to the North American Vertical Datum of 1988 [NAVD 88]).

Missing from 1932 data: 1,115 mi2 within modified Coastal Zone Boundary

Missing from 1956 data: 920 mi2within modified Coastal Zone Boundary

Missing from 1932 and 1956 data: 577 mi2within modified Coastal Zone Boundary