Overflight Remote Sensing 

in Support of Long-Term Monitoring and LTEMP 

Glen Canyon Dam Adaptive Management Work Group Meeting 

February 28-29, 2024, Phoenix, AZ 

Joel B. Sankey, US Geological Survey (USGS), Southwest Biological Science Center (SBSC), 

Grand Canyon Monitoring and Research Center (GCMRC) 

Nathaniel Bransky, Northern Arizona University (NAU) 

Thomas Gushue, USGS, SBSC, GCMRC 

Keith Kohl, USGS, SBSC, GCMRC 

Lori Pigue, USGS, Astrogeology Science Center (ASC) 
 

 

 

 

 

 

 

 

 

 

Project Goals and Objectives 

GCMRC Triennial Workplan (TWP) 

Project L FY2021/2022/2023/2024 

Budget $892k/$284k/$316k/$352k 

Imagery and derivative data products from overflight 

remote sensing are used either directly or indirectly by 

every science project proposed in the TWP to address 

every resource goal of the LTEMP 

Science Questions: 

• How has landcover changed in the Colorado River

Ecosystem (CRe) at decadal timescales?

• How are observed landcover changes related to dam

operations, other land use and management activities, as

well as climate and other environmental factors in the Little Colorado River 

ecosystem? Confluence – May 2021 

Preliminary data – do not cite 
 

 

Airborne Remote Sensing in Grand Canyon 

The high-resolution image collection from GCDAMP’s May 2021 overflight is the most recent in a 

rich archive of aerial imagery that is used to track changes of the Colorado River in the Grand 

Canyon. 

History of aerial remote sensing in Grand Canyon: 

• Earliest air photos are black and white prints acquired 

from an airplane in 1935 

• First set of air photos acquired after Glen Canyon Dam 

was completed are black and white prints from May 

1965 

• First color and color-infrared air photos were acquired 

during flights in the 1980s 

• First digital multispectral images were acquired in the 

late-1990s 

• First acquisition similar to the May 2021 overflight (high 

spatial resolution digital multispectral imagery and 

digital topography) occurred in May 2002, and then 

again in 2004, 2005, 2009, 2013, 2021 

https://www.usgs.gov/centers/southwest-biological-science-center/science/airborne-remote-sensinggrand-canyon 
 

2021 Overflight Orthomosaic 

Data Collection by Fugro, Inc. under 

contract with the USGS Grand Canyon 

Monitoring and Research Center 

1. Collected from just upstream of Glen 

Canyon Dam (in Lake Powell) near 

Page, Arizona, downstream to Lake 

Mead's Pearce Ferry, Arizona, for a 

total length of 475 kilometers (km) at 

a width of about 500 meters (m) 

centered on the mainstem of the 

Colorado River and seven primary 

tributaries 

2. Targeted river discharge of 227 m3/s 

(8,000 cubic feet per second) 

3. For any given section of the river 

corridor, five or six overlapping linear 

flightlines were acquired, allowing for 

the greatest probability of error-free 

and low-shadow imagery 

4. Initial image orthomosaic of 

overlapping flightlines produced by 

contractor (Fugro) Preliminary results, please don’t cite 
 

May 2021 Overflight Status 

• Sankey, J.B., Bransky, N., Pigue, L., Kohl, K., 

and Gushue, T.M., 2024, Four Band Image 

Mosaic of the Colorado River Corridor in 

Arizona--2021, including Accuracy Assessment 

Data: U.S. Geological Survey data release, 

https://doi.org/10.5066/P9BBGN6G.. 

• Sankey, J.B., Kohl, K., Gushue, T., Bransky, 

N., Bedford, A., Durning, L., Davis, P.A., In 

Press, DSMs for Colorado River Corridor in 

Grand Canyon National Park and Glen Canyon 

National Recreation Area: 2002, 2009, 2013 

and 2021 and DEM for 2021: U.S. Geological 

Survey data release 

Preliminary results, please don’t cite 
 

 

The End and Next Steps 

Thanks for listening and remember it is not too early to begin planning for the next overflight which 

could occur in 2025 or 2026 during the next Triennial Workplan!