105°8'

105°8'

105°9'

105°9'

105°10'

105°10'

105°11'

105°11'

105°12'

105°12'

105°13'

105°13'

105°14'

105°14'

105°15'

105°15'

105°16'

105°17' 105°16'

40°14'

40°14'

40°13'

40°13'

40°12'

40°12'

40°11'

40°11'

Photo 1. Main Street in downtown Lyons is innundated during the September 13, 2013, 

flood event. Photograph by Lauren Simms. Used with permission.

Photo 2. Flooded house on the South Saint Vrain Creek, Southwest of Lyons, Colorado, 

September 13, 2013. Photograph by Bill Benzel (USGS).

 Flooded house on the South Saint Vrain Creek, Southwest of Lyons, Colorado,

Ph t 1 M i St t i d t L i i d t d d i th S t b 13 2013

NEBRASKAKANSAS

TX

OK NEW MEXICO

WYOMING

AZ

UTAH COLORADO

Denver COLO.

EXPLANATION

Surface-water cover—September 13, 2013

Road Classification

U.S. route

66 State route

36

©2013 DigitalGlobe

NextView License

©2013 DigitalGlobe

NextView License

©2013 DigitalGlobe

NextView License

Hygiene Hygiene Hygiene

Lyons

Longmont Longmont Longmont ongmont

Lyons

Middle/Senior

High School

7

7

66

66

66

36

36

36

Sandstone Sandstone

Quarry

Sandstone

Quarry

Sandstone

Quarry

Sandstone

Quarry

Sandstone

Quarry

Golden Ponds Park Golden Ponds Park

and Nature Area and Nature Area

Golden Ponds Park

and Nature Area

Golden Ponds Park

and Nature Area

Golden Ponds Park

and Nature Area

Golden Ponds Park

and Nature Area Vance Brand Vance Brand

Airport Airport

Vance Brand

Airport

Vance Brand

Airport

Vance Brand

Airport

Vance Brand

Airport

Indian

Mountain Mountain

Indian

Mountain

Indian

Mountain

Indian

Mountain

Indian

Mountain Rabbit

Mountain Mountain

Rabbit

Mountain

Rabbit

Mountain

Rabbit

Mountain

Rabbit

Mountain

Table Top able Top

Mountain Mountain

Table Top

Mountain

Table Top

Mountain

Table Top

Mountain

Table Top

Mountain

Saint

North

Vrain Creek

Saint

South

Vrain

Creek

Vrain

Saint

Creek

McCall

Lake

McCall

Lake

McCall

Lake

McCall

Lake

McCall

Lake

Foothills

Reservoir

Foothills

Reservoir

Foothills

Reservoir

Foothills

Reservoir

Foothills

Reservoir

McIntosh

Lake

McIntosh

Lake

McIntosh

Lake

McIntosh

Lake

McIntosh

Lake

McCaslin

Lake

McCaslin

Lake

McCaslin

Lake

McCaslin

Lake

McCaslin

Lake

Burch

Lake

Burch

Lake

Burch

Lake

Burch

Lake

Burch

Lake

Independent

Reservoir

Independent

Reservoir

Independent

Reservoir

Independent

Reservoir

Independent

Reservoir

ROADROA

CANYONCANYONCANYONCANYONCANYONCANYON

STONE

ST

NE

ST

NE

ST

NE

ST

NE

HIGHWAY HIGHWAY HIGHWAY HIGHWAY HIGHWAY HIGHWAY

FOOTHILLS

OTHILLS

FOOTHILL

OTHILLS

FOOTHILLSFOOTHILL

HYGIENE ROAD

ROAD SAINT VRAIN

ROAD

VRAIN

SAINT

STREET N 75TH

N 75TH

RAILROADRAILROAD RAILROA RAILROADRAILROAD RAILROA

RAILROAD RAILROAD RAILROAD RAILROADRAILROAD RAILROAD

STREETSTREET N 75TH

N 75TH

WOODLAND ROAD

VERMILLION VERMILLION VERMILLION ERMILLION ROAD

UTE HIGHWAY

UTE

HIGHWAY HIGHWAY HIGHWAY HIGHWAY

HIGHWAY HIGHWAY

17TH AVENUE AVENUE AVENUE AVENUE

9TH AVENUE

Location of

photo 1

Location of

photo 2

1 1/ 2 0 1 MILE

SCALE 1:15 000

1000 1000 0 2000 3000 4000 5000 6000 7000 FEET

1 .5 0 1 KILOMETER

Image base mosaics produced from DigitalGlobe WorldView-2 data, accessed Sept. 13, 2013

Water and place names derived from 1:1,000,000-scale U.S. Geological Survey National Map

digital data, accessed in 2014 at http://viewer.nationalmap.gov/viewer/. 

This dataset has been orthorectified and pan-sharpened to enhance mapping accuracy and

spatial resolution. Multispectral red (band 3), green (band 2), and blue (band 1) image

composite shown. 

UTM projection, zone 13N, World Geodetic System of 1984 (WGS84) 

©COPYRIGHT 2013 DigitalGlobe, Inc., Longmont, Colo., USA, 80503. DigitalGlobe and the

DigitalGlobe logos are trademarks of DigitalGlobe, Inc. The use and/or dissemination of this data

and/or and product in any way derived therefrom are restricted. Unauthorized use and/or

dissemination is prohibited.

MN

8°56'

159 MILS

0°12'

4 MILS

GN

UTM GRID AND 2013 MAGNETIC NORTH

DECLINATION AT CENTER OF SHEETS

Publishing support provided by:

Denver Publishing Service Center

Manuscript approved for publication March 6, 2015

This report is available at:

http://pubs.usgs.gov/of/2015/1042

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20151042

Any use of trade, firm, or product names is for descriptive purposes 

only and does not imply endorsement by the U.S. Government.

Although this information product, for the most part, is in the public 

domain, it also contains copyrighted materials as noted in the text. 

Permission to reproduce copyrighted items must be secured from 

the copyright owner.

Use of Satellite Images to Determine Surface-Water Cover During the Flood Event of September 13, 2013, 

in Lyons and Western Longmont, Colorado

By

Christopher J. Cole,1

 Beverly A. Friesen,1 Earl M. Wilson,1 Stanley R. Wilds,2 andSuzanne M. Noble2

2015 1

U.S. Geological Survey

2

Parallel, Inc., Lakewood, Colo.

To learn about the USGS and its information products visit

http://www.usgs.gov/ 

1-888-ASK-USGS

For more information concerning this publication, contact:

Center Director

USGS Special Applications Science Center 

Box 25046, Mail Stop 520

Denver, CO 80225

(303) 236-1464

Suggested citation: Cole, C.J., Friesen, B.A., 

Wilson, E.M., Wilds, S.R., and Noble, S.M., 2015, 

Use of satellite images to determine 

surface-water cover of the September 13, 2013,

flood event in Lyons and western Longmont, 

Colorado: U.S. Geological Survey Open-File Report 

2015–1042, 1 sheet, scale 1:15,000,

http://dx.doi.org/10.3133/ofr20151042/. 

References Cited

Balluck, Kyle, 2013, Obama declares major disaster in Colo. (video): Washington, D.C., News Communications, Capitol Hill Publishing Corp., The Hill, September 15, 2013, accessed May 16, 2014 at 

http://thehill.com/blogs/blog-briefing-room/news/322289-obama-signs-colo-disaster-declaration.

Boulder Creek Critical Zone Observatory, 2013, The Colorado Storm and Flood of 2013: Boulder, 

Colo., Critical Zone Observatories, October 25, 2013, accessed May 16, 2014 at

http://criticalzone.org/boulder/news/story/the-flood-of-2013/.

Cole, C.J., Friesen, B.A., Wilds, S.R., Noble, S.M., Warner, Harumi, and Wilson, E.M., 2013, 

Satellite images of the September 2013 flood event in Lyons, Colorado: U.S. Geological 

Survey Open-File Report 2013–1286, 1 sheet, http://dx.doi.org/10.3133/ofr20131286.

Current Results, 2013, Average Yearly Precipitation for Colorado: Smithers, B.C., Canada, Current 

Results Nexus, accessed May 16, 2014 at

http://www.currentresults.com/Weather/Colorado/average-yearly-precipitation.php.

Definiens, 2012, Developer XD 2.0.4 user guide: Carlsbad, Calif., Definiens Inc., accessed September 

5, 2014 at https://workspace.imperial.ac.uk/imagingfacility/public/DefiniensUserGuide.pdf.

DigitalGlobe, 2013, The Benefits of the Eight Spectral Bands of WorldView-2: Longmont, Colo., 

DigitalGlobe, accessed September 5, 2014 at 

https://www.digitalglobe.com/sites/default/files/DG-8SPECTRAL-WP_0.pdf. 

Freedman, Andrew, 2013, Flood-ravaged Boulder, Colo., sets annual rainfall record: New York, 

Climate Central, September 16, 2013, accessed May 16, 2014 at http://www.climatecentral.org/

news/flood-ravaged-boulder-colorado-sets-annual-rainfall-record-16481.

Garrison, Robert, 2013, Colorado flood—Rebuild likely to take more than a year: McLean, Va., 

Multimedia Holdings Corp., Gannett Company, Inc., 9News, September 16, 2013, accessed 

May 16, 2014, at 

http://www.9news.com/news/article/355407/339/Rebuild-likely-to-take-more-than-a-year.

Gesch, D.B., Oimoen, M.J., Greenlee, S.K., Nelson, C., Steuck, M., and Tyler, D., 2002, The 

National Elevation Dataset: Photogrammetric Engineering and Remote Sensing, v. 68, no. 1, p. 5–11.

Henson, Bob, 2013, Inside the Colorado deluge—How much rain fell on the Front Range, and how 

historic was it?: Boulder, Colo., University Corporation for Atmospheric Research (UCAR), 

AtmosNews, September 14, 2013, accessed May 16, 2014 at 

http://www2.ucar.edu/atmosnews/opinion/10250/inside-colorado-deluge.

Lacaux, J.P., Tourre, Y.M., Vignolles, Cecile, Ndione, J.A., and Lafaye, M., 2007, Classification of 

ponds from high-spatial resolution remote sensing—Application to Rift Valley Fever 

epidemics in Senegal: Remote Sensing of Environment v. 106, p. 66–74.

McFeeters, S.K., 1996, The use of the Normalized Difference Water Index (NDWI) in the 

delineation of open water features: International Journal of Remote Sensing, v. 17, no.7, p.1425–1432.

Paulson, Amanda, 2013, For Colorado's 'biblical' floods, numbers tell astonishing tale: Boston, 

Mass., The Christian Science Monitor, September 18, 2013, accessed May 13, 2014 at 

http://www.csmonitor.com/USA/2013/0918/For-Colorado-s-biblical-floods-numbers-tell-aston

ishing-tale-video.

Rouse, J.W., Jr ., Haas, R.H., Schnell, J.A., and Deering, D.W., 1973, Monitoring vegetation 

systems in the Great Plains with ERTS, in Third Earth Resources Technology Satellite (ERTS) 

Symposium, Washington, D.C., December 10–14, 1973, Paper A–20: National Aeronautics 

and Space Administration (NASA) SP–351, v. 1, 309–317.

Shiff, Blair, 2013, Colorado floods—Statewide fatality numbers revised: McLean, Va., Multimedia 

Holdings Corp., Gannett Company, Inc., 9News, September 18, 2013, accessed May 16, 2014 

at http://www.9news.com/news/article/355519/339/Statewide-fatality-number-revised.

Smith, Matt, and Hennen, Dave, 2013, Record rain, steep canyons fueled Colorado floods: New 

York, Time Warner, Turner Broadcasting System, Cable News Network (CNN), September 20, 

2013, accessed May 16, 2014 at http://www.cnn.com/2013/09/18/us/colorado-flooding/index.html.

Abstract

The flooding that occurred in north-central Colorado in 2013 was some of the most destructive in the 

state’s history. Following a summer of drought and wildfires, a wet weather system stalled over the Front 

Range area from Fort Collins in the north to Colorado Springs in the south, including the cities of Lyons and 

Longmont. This weather system produced rainfall amounts that greatly exceeded historical highs. The 

Colorado Office of Emergency Management reported at least eight deaths. More than 11,000 people were 

evacuated from their homes, and the flooding caused an estimated $2 billion dollars in damages. On 

September 14, 2013, President Barack Obama issued a major disaster declaration for 15 Colorado counties 

affected by the severe weather and related damage. 

To support local, State, and Federal disaster response coordination efforts in Colorado, the U.S. 

Geological Survey (USGS) developed a geospatial product to identify surface-water cover from Lyons to 

western Longmont. This information was derived from September 13, 2013 WorldView-2 multispectral 

imagery at a spatial resolution of 3 meters (m). These data were orthocorrected and pan-sharpened. Three 

spectral indices (NDVI, NDWI, and NDTI) that were computed from this processed imagery were used to 

help determine the extent of the surface-water cover. The result was converted to a vector format. 

This surface-water cover dataset was created as a timely representation of post-flood ground conditions 

to support response efforts. This dataset and all processed imagery and derived products were uploaded to the 

USGS Hazards Data Distribution System (HDDS) website (http://hddsexplorer.usgs.gov/uplift/hdds/) for 

distribution to those responding to the flood event.

Introduction

The flooding that occurred in north-central Colorado in 2013 was some of the most destructive in the 

state’s history. Following a summer of drought and extreme wildfires, a wet weather system stalled over the 

Front Range area from Fort Collins south to Colorado Springs and produced rainfall amounts that greatly 

exceeded historical highs (Boulder Creek Critical Zone Observatory, 2013). Boulder County has an average 

annual precipitation of 20.7 inches, and it was one of the worst hit areas with 9.08 inches of precipitation on 

September 12, 2013, and up to 17 inches of rain on September 15 (Current Results, 2013; Freedman, 2013; 

Henson, 2013; Paulson, 2013; Smith and Hennen, 2013). At least eight deaths were reported by the 

Colorado Office of Emergency Management (Henson, 2013; Shiff, 2013), more than 11,000 people were 

evacuated from their homes (Boulder Creek Critical Zone Observatory, 2013; Garrison, 2013), and the 

flooding caused an estimated $2 billion dollars in damages (Shiff, 2013). President Barack Obama declared 

a state of disaster for 15 counties in Colorado (Balluck, 2013). 

Purpose

The U.S. Geological Survey (USGS) developed a 1:15,000-scale geospatial product to identify 

surface-water cover to support local, State, and Federal disaster response coordination efforts in Colorado. 

This product, presented here as a map, depicted the water-surface cover that resulted from the flooding that 

occurred from Lyons to western Longmont on September 13, 2013.

Methodology

Water cover was derived from DigitalGlobe’s WorldView-2 multispectral imagery dated September 

13, 2013, at a spatial resolution of 3 meters (m) (DigitalGlobe, 2013). The WorldView-2 data were 

orthocorrected using a 10-m USGS Digital Elevation Model (DEM) to enhance mapping accuracy (Gesch 

and others, 2002; see The National Elevation Dataset, NED, at http://ned.usgs.gov/). A 0.50-m resolution 

pan-sharpened multispectral image was produced to support National Guard flood relief efforts in Lyons, 

Colorado, and vicinity, and was used for water-cover mapping verification of the extent of the flooding 

(Cole and others, 2013).

Three spectral indices were computed from the processed 3-m imagery. Spectral indices are commonly 

used by remote sensing scientists to identify a particular surface-cover type based upon its absorption or 

reflection of incident solar energy in different regions of the electromagnetic spectrum. The Normalized 

Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized 

Difference Turbidity Index (NDTI) used for this study are defined below:

Normalized Difference Vegetation Index (NDVI)=(Near infrared–red)/(near infrared+red). The 

NDVI is used to discriminate vegetation health and to differentiate this cover from non-vegetated 

surfaces (Rouse and others, 1973).

Normalized Difference Water Index (NDWI)=(Green–near infrared)/(green+near infrared). The 

NDWI is useful for delineating clear water cover (McFeeters, 1996).

Normalized Difference Turbidity Index (NDTI)=(Red–green)/(red+green). The Normalized 

Difference Turbidity Index (NDTI) allows the detection of high turbidity (low clarity) water 

cover (Lacaux and others, 2007). Turbid water contains a high volume of suspended materials 

and is common following flood events.

The use of these indices enabled us to determine the extent of the surface-water cover. Vector 

polygons identifying all surface-cover features were derived from the processed 3-m data using eCognition 

Developer image segmentation software (Definiens, 2012). This software allows us to group similar image 

pixels and convert them into vector objects based on their spatial and spectral characteristics. Water was 

then delineated from other surface cover using classification rules based on pixel-value thresholds of the 

processed imagery, the derived spectral indices, and terrain slope calculated from 10-m DEM information. 

For instance, surface water holds a very low pixel value in the NDVI, and higher levels in the NDWI and 

the NDTI than other cover types. The use of slope information from the DEMs reduced the incidence of 

misclassification of non-vegetated background soils as distinguished from water in high-relief areas. Minor 

editing was used to refine the extent of the surface-water cover data, and included merging and smoothing 

the vector polygons as well as revising some of them based on visual interpretation.

Summary

The data displayed on this map were created to support flood-response efforts, specifically for use in 

determining damage assessment and informing mitigation decisions. Water cover was derived from 

multispectral imagery at a spatial resolution of 3 m. The data were orthocorrected and pan-sharpened to 

produce a multispectral image. Three spectral indices (NDVI, NDWI, and NDTI) were computed from the 

processed imagery. The extent of the surface-water cover was determined and converted to a vector format. 

The processed data were then placed onto a base image. All processed imagery and derived products were 

uploaded to the USGS Hazards Data Distribution System (HDDS) website (http://hddsexplorer.usgs.gov-

/uplift/hdds/) for distribution to those responding to the flood event. These data were intended to provide a 

timely representation of post-flood ground conditions to aid in flood-response efforts by decisionmakers and 

the general public, and could also be used to support future water-science studies, such as historical 

inundation trends.

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2015–1042