Change in the Length of the Northern Section of the 

Chandeleur Islands Oil Berm, September 5, 2010, 

through September 3, 2012

By N.G. Plant and K.K. Guy

Open-File Report 2013–1074

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:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

For more information on the USGS—the Federal source for science about the Earth,

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

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Suggested citation:

Plant, N.G., and Guy, K.K., 2013, Change in the length of the northern section of the Chandeleur Islands oil berm, 

September 5, 2010, through September 3, 2012: U.S. Geological Survey Open-File Report 2013-1074, 9 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

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

Methods...............................................................................................................................................................3

Results.................................................................................................................................................................6

Acknowledgments ...............................................................................................................................................6

Figures

1. Chandeleur and Breton Islands (part of the Breton Island National Wildlife Refuge), the Mississippi River 

Delta, the site of the Deepwater Horizon oil spill, and the location of the full extent of the Chandeleur 

Islands berm.............................................................................................................................................. 1

2. The Chandeleur Islands berm divided into northern, middle, and southern sections................................ 2

3. The completed northern section of the Chandeleur Islands berm............................................................. 3

4. Example of a panchromatic image............................................................................................................ 4

5. Example of isolines generated on the basis of pixel value............................................................................ 4

6. Example of berm-length measurement ..................................................................................................... 5

7. Time series of berm-length measurements from each data source. ......................................................... 6

Tables

1. Satellite multispectral and panchromatic image resolutions...................................................................... 4

2. Berm-length measurements...................................................................................................................... 7
1

Change in the Length of the Northern Section of the 

Chandeleur Islands Oil Berm, September 5, 2010, 

through September 3, 2012

By N.G. Plant and K.K. Guy

Introduction

On April 20, 2010, an explosion on the Deepwater Horizon oil rig drilling at the Macondo 

Prospect site in the Gulf of Mexico resulted in a marine oil spill that continued to flow through 

July 15, 2010. One of the affected areas was the Breton National Wildlife Refuge, which consists 

of a chain of low-lying islands, including Breton Island and the Chandeleur Islands, and their 

surrounding waters. The island chain is located approximately 115–150 kilometers (km) northnorthwest of the spill site (fig. 1). A sand berm was constructed seaward of, and on, the island chain. 

Construction began at the northern end of the Chandeleur Islands in June 2010 and ended in April 

Breton

Island

Chandeleur

Islands

Deepwater

Horizon

Mississippi

River

Delta

Berm

GULF

OF

MEXICO 0 10 20 30 MILES

0 10 20 30 KILOMETERS

Base from U.S. Geological Survey

Landsat 5, Feb 18, 2010

WGS 1984 UTM Zone 16N

89°W

30°N

29°N

MISSISSIPPI

ALABAMA

LOUISIANA FLORIDA

Map Area

Figure 1. Chandeleur and Breton Islands (part of the Breton Island National Wildlife Refuge), the Mississippi 

River Delta, the site of the Deepwater Horizon oil spill, and the location of the full extent of the Chandeleur 

Islands berm. The background image is U.S. Geological Survey Landsat 5 taken February 18, 2010, prior to 

the start of berm construction.
2

Base from U.S. Geological Survey

Landsat 5, Feb 18, 2010

WGS 1984 UTM Zone 16N

Northern

Section

Middle

Section

Southern

Section

As-built

Berm

C h a n d e l e u r I s l a n d s

88°50'W 88°48'W

30°0'N

29°58'N

29°56'N

29°54'N

MILES

KILOMETERS

0 1 2

0 1 2

MISSISSIPPI ALABAMA

LOUISIANA

Map Area

Figure 2. The Chandeleur Islands berm divided into northern, middle, and southern sections. The asbuilt berm footprint is shown in orange. The background image is U.S. Geological Survey Landsat 5 taken 

February 18, 2010, prior to the start of berm construction.

2011. The berm consisted of three distinct sections based on where the berm was placed relative to 

the islands (fig. 2). The northern section of the berm was built in open water on a submerged portion 

of the Chandeleur Islands platform. The middle section was built approximately 70–90 meters (m) 

seaward of the Chandeleur Islands. The southern section was built on the islands’ beaches. Repeated 

Landsat and SPOT satellite imagery and airborne lidar were used to observe the disintegration of 

the berm over time. The methods used to analyze the remotely sensed data and the resulting, derived 

data for the northern section (fig. 3) are reported here.
3

88°51'W 88°50'W

30°1'N

30°0'N

29°59'N

Base from U.S. Geological Survey

Landsat 5, September 30, 2010

WGS 1984 UTM Zone 16N

C h a n d e l e u r I s l a n d

F r a g m e n t s

Completed

Northern

Section

of Berm

0 0.25 0.5 MILES

0 0.25 0.5 KILOMETERS

MISSISSIPPI ALABAMA

LOUISIANA

Map Area

Figure 3. The completed northern section of the Chandeleur Islands berm. This U.S. Geological Survey 

Landsat 5 image was taken September 30, 2010.

Methods

The Chandeleur Islands berm was built approximately 50-m wide (above mean high water) 

and 2-m high relative to the North American Vertical Datum of 1988 (NAVD 88) and using the 1996 

Geoid model (Geoid 96). Because of the large size of the berm combined with the highly reflective nature of sand, observations from satellite imagery were possible. Medium resolution (5–30 m) 

Landsat and SPOT satellite imagery (table 1) provided relatively frequent observation opportunities. 

Additionally, three high resolution lidar elevation datasets were used for measuring berm length. A 

total of 54 observations were made from September 5, 2010, the first date usable satellite imagery 

was available after the completion of the northern section of the berm, to September 3, 2012, when 

the berm no longer occupied its as-built footprint. For the purpose of these berm-length measurements, only those portions of the berm that occupied its as-built footprint (as estimated from a 

sequence of SPOT satellite images obtained during the construction period: September 5, 2010; 

October 1, 2010; December 7, 2010; and April 3, 2011) were measured.
4

berm

berm

breaches

water

water

island

bar

Figure 4. Example of a panchromatic image. 

Water, island, bar, berm, and breaches in the 

berm are labeled. The dry sand berm appears as 

light grays to white, the water as darker shades of 

gray, and the wet sand of the berm breaches as 

mid-tone grays. 

Figure 5. Example of isolines generated on the 

basis of pixel value. The isolines are drawn in pink 

on top of the U.S. Geological Survey Landsat 7 

panchromatic image from which they were made. 

The berm is the wide, light streak of pixels running 

from the upper left to the lower right of the figure. 

The mid-tone grays in the upper right are waves.

Table 1. Satellite multispectral and panchromatic image resolutions.

Satellite Multispectral resolution Panchromatic resolution

SPOT 4 20 m 10 m

SPOT 5 10 m 5 m

Landsat 5 30 m (none)

Landsat 7 30 m 15 m

Satellite images were selected on the basis of availability, clear view of the berm, and resolution (ground sampling interval or cell size). The sensors on Landsat 5, Landsat 7, SPOT 4, and 

SPOT 5 differ in their spectral bands and resolution (table 1). When available, panchromatic bands 

were used because of their higher resolutions. When not available, single bands from the multispectral images were selected. Band 5 (1.55 to 1.75 micrometers (μm)) at 30-m resolution was used for 

Landsat 5 images. Of the twelve 20-m resolution multispectral SPOT 4 images used, band 1 (0.50 to 

0.59 μm) was used for 11 dates and band 3 (0.78 to 0.89 μm) was used for 1 date (table 2).
5

polygon

not

measured

polygon

measured

as-built

footprint

selected

isolines

measure

line

Figure 6. Example of berm-length 

measurement. The red line represents the berm’s 

as-built footprint. One yellow line encloses a small 

area that appears to be on the berm; however, 

this area does not fall within the as-built footprint. 

Therefore, this area is no longer considered part 

of the berm and is not measured. A second yellow 

line encloses a larger area and mostly falls within 

the as-built footprint. The brown line represents 

the resulting berm-length measurement.

Water has lower reflectivity than sand in the satellite images and, therefore, has a lower pixel 

intensity value. In a typical gray-scale representation where low values are dark and high values 

are light, water will appear dark and sand will appear very light or white. Wet sand is less reflective 

than dry sand and appears in mid-tone grays (fig. 4). The relatively high pixel values of dry sand 

were used to delimit the berm footprint. This method is subject to bias errors caused by differences 

in water levels when different images were acquired, and no corrections for these biases have been 

made here. The water levels from a nearby location (Station 8761305, Shell Beach, Louisiana), 

referenced to the mean sea level datum, are included in this report (table 2). 

Each image was visually examined to determine the footprint of the berm. Isolines based on 

pixel values were generated for each image using the Contour tool in ArcGIS® (fig. 5). A contour 

interval of 5 intensity units was used for Landsat 5 band 5, SPOT 4, and SPOT 5 images (fig. 5), 

and a contour interval of 2 intensity units was used for Landsat 7 panchromatic images. Because the 

pixel-intensity values for water, dry sand, and wet sand were not consistent between images, fixed 

contour levels were not used to delineate the berm. Instead, the contours were overlaid on the image 

and one of these contours was selected to represent the footprint of each berm segment as a polygon 

in the geographic information system (GIS). This footprint was then used to measure the length of 

the berm segment. Only those portions of the berm footprint that occupied the original as-built footprint were used to measure berm length (fig. 6). Once sand was moved beyond the as-built footprint 

by overwash, inundation, or breaching, it no longer contributed to the measured length of the berm.

The berm footprints obtained from three lidar elevation datasets were based on elevation 

rather than reflectivity. Contours were generated at 10-centimeter (cm) intervals and were compared 

to the berm footprints obtained from satellite imagery. The 100-cm (NAVD 88, Geoid 96) contour 

was selected to represent the subaerial portion of the berm. This level is well above the typical 

water level, allowing retrieval of topographic lidar from each survey. Similarly to the treatment of 
6

the satellite imagery, berm-length measurements were estimated where the 100-cm lidar-elevation 

contour fell within the as-built footprint. Some clusters of small polygons appeared in the lidar berm 

footprints. These clusters were measured as if they were one large polygon.

Results

The results from the satellite and lidar data analysis are presented in figure 7, which shows 

a time series of berm lengths derived from each of the sensors. The measurements are listed in 

table 2. The accuracy of the berm-length measurements was quantified from the differences between 

sequential length measurements, excluding the large length changes observed on September 6 and 

9, 2011, that were associated with storm Lee. The root mean square difference was 243 m. 

0 

500 

1000 

1500 

2000 

2500 

3000 

3500 

4000 

4500 

Sept-2010 Dec-2010 Mar-2011 July-2011 Oct-2011 Jan-2012 May-2012 Aug-2012

Berm length (m) 

SPOT 5 

Landsat 5 

Landsat 7 

Lidar 

Acknowledgments

The data collection and analysis presented in this report were conducted with support from 

the U.S. Geological Survey’s Coastal and Marine Geology Program. The clarity of the report was 

improved by reviews from C. Sherwood and J. Flocks. We thank B. Boynton, T. Burress, and 

K. Naugle for editing, producing, and publishing the final document.

Figure 7. Time series of berm-length measurements from each data source.
7

Table 2. Berm-length measurements.

Date (MDY)

Image Time 

(UT) Sensor Spectrum Isoline

Number of Line 

Segments

Total Length 

(m)

Water Level 

(m)

Area of Isoline 

Polygons (m2)

Area of Berm 

(m2)

9/5/2010 16:34 SPOT 4 band 1 70 2 4287 0.60 236405 215662

10/1/2010 16:23 SPOT 4 band 1 120 3 4209 0.24 224530 170784

12/7/2010 16:33 SPOT 4 band 1 140 1 4274 -0.42 332030 226925

1/2/2011 16:32 SPOT 4 band 1 110 1 4086 -0.14 296380 212314

1/13/2011 16:20 SPOT 4 pan 165 1 3997 -0.32 201112 164848

1/23/2011 16:27 SPOT 4 pan 190 1 3973 -0.32 274364 207905

2/13/2011 16:22 SPOT 4 pan 170 2 3981 -0.67 276848 203383

2/24/2011 16:10 SPOT 4 band 1 220 2 3864 -0.22 250067 181192

3/16/2011 16:25 SPOT 4 pan 220 1 3871 -0.09 300387 206710

5/28/2011 16:18 SPOT 4 pan 225 4 3569 0.25 184313 1523536/13/2011 16:09 SPOT 4 pan 50 2 3783 0.34 218465 171980

6/18/2011 16:13 SPOT 4 pan 65 2 3729 0.07 205332 1698867/19/2011 16:15 SPOT 4 pan 175 5 3335 0.24 142460 128903

8/4/2011 16:06 SPOT 4 pan 200 1 3791 0.00 245299 183110

8/30/2011 16:05 SPOT 4 band 3 185 2 3740 -0.01 236669 144353

9/9/2011 16:13 SPOT 4 pan 220 11 1969 0.30 86258 77147

9/14/2011 16:16 SPOT 4 pan 235 11 2191 -0.18 124252 60368

10/21/2011 16:02 SPOT 4 band 1 140 8 2048 0.04 125974 69291

12/1/2011 16:12 SPOT 4 pan 215 13 1921 0.04 94628 55188

1/27/2012 16:12 SPOT 4 band 1 170 4 1094 -0.17 35988 356573/25/2012 15:53 SPOT 4 band 1 185 7 671 0.17 15855 15537

6/16/2012 15:51 SPOT 4 pan 60 9 780 0.64 21563 21126

6/21/2012 15:55 SPOT 4 pan 60 6 594 0.55 14432 14363

6/26/2012 15:58 SPOT 4 pan 45 6 271 0.65 4071 3953

7/27/2012 16:00 SPOT 4 band 1 80 4 774 0.27 30992 26120

8/2/2012 15:44 SPOT 4 band 1 190 4 558 0.10 21987 12036
8

Table 2. Berm-length measurements.—Continued

Date (MDY)

Image Time 

(UT) Sensor Spectrum Isoline

Number of Line 

Segments

Total Length 

(m)

Water Level 

(m)

Area of Isoline 

Polygons (m2)

Area of Berm 

(m2)

4/3/2011 16:36 SPOT 5 pan 200 2 3864 -0.11 163295 155541

4/29/2011 16:35 SPOT 5 pan 220 1 3811 0.19 293933 198091

9/6/2011 16:34 SPOT 5 pan 180 15 1159 0.56 21958 21791

12/29/2011 16:40 SPOT 5 pan 180 11 1900 -0.17 54728 51267

4/6/2012 16:33 SPOT 5 pan 185 17 895 0.23 15599 15559

5/7/2012 16:36 SPOT 5 pan 220 13 828 0.45 14011 13999

6/2/2012 16:35 SPOT 5 pan 135 14 870 0.40 14779 14732

9/3/2012 16:44 SPOT 5 band 1 0 0 0.03 0 0

11/17/2010 16:15 Landsat 5 band 5 60 3 4251 0.19 213683 196434

12/3/2010 16:16 Landsat 5 band 5 60 1 4294 -0.48 327139 224936

12/19/2010 16:16 Landsat 5 band 5 65 1 4215 -0.19 308113 217324

2/21/2011 16:16 Landsat 5 band 5 75 1 3935 -0.17 325223 206750

3/25/2011 16:16 Landsat 5 band 5 65 1 3877 -0.01 364934 203410

5/28/2011 16:15 Landsat 5 band 5 80 1 3820 0.25 382134 1994627/31/2011 16:15 Landsat 5 band 5 70 1 3793 0.23 283368 1954068/16/2011 16:15 Landsat 5 band 5 110 2 3772 0.08 239345 177599

10/3/2011 16:14 Landsat 5 band 5 120 6 2154 0.21 103317 85999

1/12/2011 16:19 Landsat 7 pan - band 8 42 4 3813 -0.39 215844 186296

3/1/2011 16:19 Landsat 7 pan - band 8 52 4 3707 -0.20 300342 191166

8/24/2011 16:19 Landsat 7 pan - band 8 78 3 3759 0.35 204096 147228

9/25/2011 16:19 Landsat 7 pan - band 8 60 7 2213 0.22 120897 93973

12/30/2011 16:20 Landsat 7 pan - band 8 52 6 1809 -0.05 79836 64407

1/15/2012 16:20 Landsat 7 pan - band 8 60 7 972 -0.39 55414 34659

5/6/2012 16:21 Landsat 7 pan - band 8 78 6 501 0.47 11546 11536

5/22/2012 16:21 Landsat 7 pan - band 8 94 5 755 0.16 23029 22069
9

Table 2. Berm-length measurements.—Continued

Date (MDY)

Image Time 

(UT) Sensor Spectrum Isoline

Number of Line 

Segments

Total Length 

(m)

Water Level 

(m)

Area of Isoline 

Polygons (m2)

Area of Berm 

(m2)

2/12/2011 Lidar elevation - cm 100 1 3985 148019 127343

5/31/2011 Lidar elevation - cm 100 15 3332 77453 71713

2/6/2012 Lidar elevation - cm 100 11 1171 25314 24035

Date (MDY) = Date in month/day/year format.Image Time (UT) = Universal Time that image was acquired in hours and minutes (HH:MM).Sensor = Image source type.Spectrum = The satellite image band used or, for lidar, the elevation used, in centimeters.Isoline = Satellite image pixel value or lidar elevation of contour line used to delineate berm.Number of Line Segments = Number of line segments in berm measurement.Total Length (m) = Total length of berm, in meters.Water Level (m) = Water level Shell Beach, Louisiana, tide station, at the time of image collection, in meters using Mean Sea Level as the datum.Area of Isoline Polygons (m2) = Area of isoline polygons falling, at least in part, within the as-built footprint, in square meters.

Area of Berm (m2) = Area of the portion of the isoline polygons that fall within the as-built footprint, in square meters.