Change in the Length of the Middle Section of the 

Chandeleur Islands Oil Berm, November 17, 2010, 

through September 6, 2011

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

Open-File Report 2013–1075

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

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Suggested citation:

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

November 17, 2010, through September 6, 2011: U.S. Geological Survey Open-File Report 2013-1075, 8 p.

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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 middle 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 Middle Section of the 

Chandeleur Islands Oil Berm, November 17, 2010, 

through September 6, 2011

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) northFigure 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.

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
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.

northwest 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 

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 middle section (fig. 3) are reported here.
3

88°50'W 88°49'W

29°59'N

29°58'N

29°57'N

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

Completed

Middle

Section

of Berm

0 0.25 0.5 KILOMETERS

0 0.25 0.5 MILES

Base from U.S. Geological Survey

Landsat 5, December 3, 2010

WGS 1984 UTM Zone 16N

MISSISSIPPI ALABAMA

LOUISIANA

Map Area

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

Landsat 5 image was taken December 3, 2010, and shows the middle section of the berm, which lies 

approximately 70–90 m offshore of the Chandeleur Islands.

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

total of 29 observations were made from November 17, 2010, the first date usable satellite imagery 

was available after the completion of the middle section of the berm, to September 6, 2011, 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

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 

Figure 4. Example of a panchromatic image. 

Water, waves, island, beach, berm, and breaches 

in the berm are labeled. The dry sand berm and 

beaches appear as light grays to white, the water 

as darker shades of gray, and the wet sand of the 

berm breaches as mid-tone grays. 

waves

island

water

beach

berm

berm

 breaches

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.
5

polygon

not

measured

polygon

measured

as-built

footprint

selected

isolines

measure

line

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

0.59 μm) was used for three dates and band 3 (0.78 to 0.89 μm) was used for one date (table 2).

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 two 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 

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.
6

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

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 January 12, 2011, 

via Landsat 7. The root mean square difference was 236 m. 

0 

500 

1000 

1500 

2000 

2500 

3000 

3500 

Nov-2010 Jan-2011 Feb-2011 Apr-2011 June-2011 July-2011 Sept-2011 

Berm length (m) 

SPOT 4 

SPOT 5 

Landsat 5 

Landsat 7 

Lidar 

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

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.
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)

12/7/2010 16:33 SPOT 4 band 1 140 5 3389 -0.42 138628 126175

1/2/2011 16:32 SPOT 4 band 1 110 6 3026 -0.14 92235 82066

1/13/2011 16:20 SPOT 4 pan 165 5 2367 -0.32 63334 417091/23/2011 16:27 SPOT 4 pan 190 6 2484 -0.32 78718 56094

2/13/2011 16:22 SPOT 4 pan 170 10 2542 -0.67 63022 527602/24/2011 16:10 SPOT 4 band 1 220 10 2489 -0.22 80451 602133/16/2011 16:25 SPOT 4 pan 220 5 2368 -0.09 84400 713836/13/2011 16:09 SPOT 4 pan 50 7 1575 0.34 35668 30480

6/18/2011 16:13 SPOT 4 pan 65 5 1620 0.07 29956 27381

7/19/2011 16:15 SPOT 4 pan 175 15 1588 0.24 32739 28136

8/4/2011 16:06 SPOT 4 pan 200 11 1089 0.00 18749 17368

8/9/2011 16:10 SPOT 4 pan 205 9 886 0.06 10708 10476

8/30/2011 16:05 SPOT 4 band 3 185 5 998 -0.01 24985 13283

4/3/2011 16:36 SPOT 5 pan 200 8 2263 -0.11 46342 45864

4/29/2011 16:35 SPOT 5 pan 220 11 1868 0.19 54238 50614

9/6/2011 16:34 SPOT 5 pan --- 0 0 0.56 0 0

11/17/2010 16:15 Landsat 5 band 5 60 3 3390 0.19 142364 117665

12/3/2010 16:16 Landsat 5 band 5 60 4 3340 -0.48 126145 107662

12/19/2010 16:16 Landsat 5 band 5 65 4 3318 -0.19 121676 108867

2/21/2011 16:16 Landsat 5 band 5 75 8 2333 -0.17 70199 47633

3/25/2011 16:16 Landsat 5 band 5 65 5 2066 -0.01 82788 67412

5/28/2011 16:15 Landsat 5 band 5 80 5 1729 0.25 64399 521237/31/2011 16:15 Landsat 5 band 5 70 8 1048 0.23 20510 19110

8/16/2011 16:15 Landsat 5 band 5 110 9 1156 0.08 18342 17367
8

Image Time Number of Line Total Length Water Level Area of Isoline 

Date (MDY) (UT) Sensor Spectrum Isoline Segments (m) (m) Polygons (m2) Area of Berm (m2)

1/12/2011 16:19 Landsat 7 pan (band 8) 42 5 2237 -0.39 68479 60817

3/1/2011 16:19 Landsat 7 pan (band 8) 52 5 2668 -0.20 111199 92659

8/24/2011 16:19 Landsat 7 pan (band 8) 78 4 1089 0.35 22476 14944

2/12/2011 --- Lidar elevation cm 100 6 2247 --- 41525 34540

5/31/2011 --- Lidar elevation cm 100 8 1330 --- 12244 10776

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.

Table 2. Berm-length measurements.—Continued