Airborne Remote Sensing in Grand Canyon

Science Center Objects

A high-resolution image collection in 2021 will be the most recent in a rich archive of aerial imagery that are used to track changes of the Colorado River in Grand Canyon. Imagery will be acquired from an airplane in Grand Canyon National Park along the Colorado River corridor and the Little Colorado River starting Memorial Day weekend and continuing through the first week of June 2021. This imagery will be used by the USGS and partners from the Glen Canyon Dam Adaptive Management Program (GCDAMP) to monitor changes in the Colorado River and riparian ecosystem in Grand Canyon and impacts of management including Glen Canyon Dam operations. Water released from Glen Canyon Dam will be reduced to a steady discharge of 8,000 cubic feet per second (cfs) in the Colorado River for the duration of the image collection mission. The low river discharge is required because consistent water levels are necessary for remote sensing image analyses that compare this new image dataset to historic datasets which also were collected with constant steady discharge  of 8,000 cfs.

History of Aerial Remote Sensing in Grand Canyon

Similar to 2021, 4-band multispectral imagery and photogrammetrically derived topography data were also previously acquired in 2002, 2005, 2009, and 2013. With each of those previous digital image acquisitions, GCMRC remote sensing staff developed and improved upon a methodology for producing a spatially seamless, spectrally consistent, and nearly cloud- and blemish-free image mosaic (Davis and others, 2012; Durning and others, 2016). That proven methodology will be used to develop an image mosaic from the 2021 acquisition.

An abbreviated history of aerial remote sensing of the Colorado River in Grand Canyon:

  • The earliest air photos are black and white prints acquired from an airplane in 1935. 
  • The first set of air photos acquired after Glen Canyon Dam was completed are black and white prints from May 1965
  • The first color and color-infrared air photos were acquired during flights in the 1980s
  • The first digital multispectral images were acquired in the late-1990s
  • The first acquisition similar to this year's overflight (high spatial resolution digital multispectral imagery and digital topography) occurred in May 2002, and then again in 2004, 2005, 2009, 2013, 2021

Aerial Remote Sensing Science for the Colorado River in Grand Canyon

GCMRC scientists have leveraged this rich archive of data to relate observations of landcover changes to physical, biological and hydrological processes (Figure 1). This remote sensing science helps to support resource management decisions in the iconic Grand Canyon and Colorado River. One example is a quantitative assessment of riparian vegetation changes that occurred as a function of dam operations and climate during the first five decades of the operations of Glen Canyon Dam. Other examples are mapping tamarisk and tamarisk beetle impacts throughout the Colorado River in Glen Canyon and Grand Canyon. For these tamarisk studies, imagery were incorporated from the Worldview 2 constellation satellite and,  while the satellite imagery were helpful, they were not high resolution enough to replace the airborne multispectral imagery such as will be collected in the 2021 overflight. Changes in campsites area used by river runners and dunefields sourced by windblown river sand, which help to preserve archeological sites, are also evaluated with remote sensing. Using highly detailed vegetation and sand maps and predictive modelling, future riparian landcover changes are forecasted as a function of river flows owing to the planned operations of Glen Canyon Dam through 2036.

Bar graph of land cover data in Grand Canyon

Figure 1. Example graph of land cover calculations derived from remote sensing image analysis for 0.1-mile segments of the Colorado River from Glen Canyon Dam to Diamond Creek. The percentage of the river valley covered by water (at 8,000 CFS river discharge), sand, vegetation, and other landcover are plotted for each 0.1-mile segment of the river.

(Public domain.)