A Continuous High-Resolution Profile of the 

Riverbed and Water Surface for 460-km of the 

Colorado River in Grand Canyon

Shannon Sartain

U.S. Geological Survey

Southwest Biological Science Center

Grand Canyon Monitoring and Research Center

GCDAMP Annual Reporting Meeting 2023
Project B: Sandbar and Sediment Storage 

Monitoring and Research

• Project Elements and Objectives

• B.3 Control Network and Survey Support

• In support of Remote Sensing Overflight (Project L)

• Cooperators: Northern Arizona University

• LTEMP Resource Goals:

• Sediment: "Increase and retain fine sediment volume, area, and distribution in the 

Glen, Marble, and Grand Canyon reaches above the elevation of the average base flow for ecological, cultural, and recreational purposes“

This information is preliminary and is subject to revision. It is being provided 

to meet the need for timely best science. The information is provided on the 

condition that neither the U.S. Geological Survey nor the US. Government 

shall be held liable for any damages resulting from the authorized or 

unauthorized use of the information
Acknowledgements

Paul Grams, Matt Kaplinski, and Keith Kohl

U.S. Geological Survey, Grand Canyon 

Monitoring and Research Center

Katie Chapman

Northern Arizona University

Trip Participants:

Jeremy Swindlehurst, Bryan Smith, 

Chris Louderback, Karen Koestner, 

Sinjin Eberle, Bryan Cooperrider, 

John O’Brien, Maggie Ryan
2021 Survey Overview

• Surveys conducted May 29th through June 5th, 2021, 

concurrent with overflight

• Glen Canyon Dam releases held steady at 8,000 cfs (227 cms)

• Elevations of the water surface and the riverbed collected 

from Lees Ferry to Pearce Ferry

• River miles 0 to 280
Water surface elevation profile Water Surface Elevation
Vertical Year Reference Discharge Method Accuracy

Birdseye and Burchard 15,000 to 30,000 cfs, 1923 Spirit level, stadia rod ± 1.4 m (1924) spike of ~115,000 cfs

Previous water surface surveys
 

 

 

Previous water surface surveys 

Year Reference Discharge Method Vertical 

Accuracy 

1923 Birdseye and Burchard 

(1924) 

15,000 to 30,000 cfs, 

spike of ~115,000 cfs Spirit level, stadia rod ± 1.4 m 

2000 Magirl et al. (2005) 8,000 cfs GPS (aircraft) + LiDAR ± 0.5 m 

Magirl et al. 

(2008) 
Previous water surface surveys

Year Reference Discharge Method Vertical 

Accuracy

1923 Birdseye and Burchard 

(1924)

15,000 to 30,000 cfs, 

spike of ~115,000 cfs Spirit level, stadia rod ± 1.4 m

2000 Magirl et al. (2005) 8,000 cfs GPS (aircraft) + LiDAR ± 0.5 m

2021 This study 8,000 cfs GPS (boat) + 

total station survey ± 0.1 m*

*Vertical accuracy is spatially variable 

based on GPS quality. 10 cm vertical 

accuracy applies to ~245 of 280 river miles
Applanix 

Antennae

R10 

Antenna

Water Surface Elevation – Data Collection

2 continuous data sources

(Applanix and R10)

• Applanix system did not run during 

rapids

• Both systems post-processed with 

GNSS base stations on the rim

• Each Applanix and R10 point have 

an associated vertical error
2 continuous data sources

(Applanix and R10)

1 validation data source

(Total station survey)

95% of shots 

within 2.5 cm 

vertical error

Water Surface Elevation – Data Collection
Water Surface Elevation – Data Collection

• 201.5 miles of high quality Applanix Data (VE < 10cm) Pearce Ferry

High Quality Data Available (Applanix and R10 Vertical Error < 10 cm) Lees Ferry

We can use the total station survey 

points to validate the Applanix and 

R10 points by comparing their 

elevations for the same river mile

• 211.3 miles of high quality R10 data (VE < 10cm)

• 578 total station survey points at 316 unique river hundredth-miles

Preliminary data, subject to review, do not cite.
Water Surface Elevation – Data Validation

Applanix minus TS 

Survey (median): 

3.3 cm

Two independent systems, 

post-processed with different software, 

give us very similar results and are 

validated by our ground-truth surveys

R10 minus TS 

Survey (median): 

1.1 cm

*only data from -1.0 to +1.0 m are shown

261/269 (97%) Applanix comparisons shown

269/294 (91%) R10 comparisons shown

Preliminary data, subject to review, do not cite
Of Applanix points with vertical 

error < 10cm, 87% are within 

10 cm of the corresponding 

total station survey point

Of R10 points with vertical 

error < 10cm, 93% are within 

10 cm of the corresponding 

total station survey point

Applanix Vertical Error (m) R10 Vertical Error (m)

Preliminary data, subject to review, do not cite

Water Surface Elevation – Data Validation
How do we systematically

generate a profile from varying 

amounts and quality of data?

Preliminary data, subject to review, do not cite

Water Surface Elevation – Profile Creation
Both systems with 

VE < 10cm, 

validated by TS 

survey

One system with 

VE < 10 cm

Both systems 

with VE < 10 cm

One system with 

VE < 10 cm

We can group the data by the number of 

data sources and their vertical error.

Then we can systematically identify 

which data source to use to generate 

our final profile and the associated error

Preliminary data, subject to review, do not cite

Water Surface Elevation – Profile Creation
Preliminary data, subject to review, do not cite

Water Surface Elevation – Profile Creation

• One point per hundredth mile

• Each point has a data source (and 

how many data sources validate 

that point)

• Each point has a vertical error
 

 

Applanix 

Category # RMs 

Applanix or R10, VE <= 10 cm 246.1 

Applanix or R10, VE > 10 cm 29.2 

No data 6.2 

vertical 

error (m) 

Areas with high vertical 

error likely have GPS 

outages due to obstruction 

of the sky by canyon walls 

Preliminary data, subject to 

review, do not cite 
Water Surface Elevation – Profile Creation

Preliminary data, subject to review, do not cite
Not exactly enough data to 

make a profile with!

Only points with 

vertical error < 10 

cm shown in color

Water Surface Elevation – Profile Creation

Preliminary data, subject to review, do not cite
Preliminary data, subject to review, do not cite

We can try the 2000 profile 

(Magirl et al. 2005)

Water Surface Elevation – Profile Creation
Preliminary data, subject to review, do not cite

We can include heights from 

the 2021 overflight DEM

We will try the land surface 

near the water’s edge when 

that product is available

2021 Overflight 

DEM

Water Surface Elevation – Profile Creation
Lees 

Ferry

Water Surface Elevation – Final Profile

• Water surface elevation every hundredth mile 

with an associated data source and vertical error 

• For 245 miles that vertical error is within 10 cm

House 

Rock

Hance

Granite

Crystal

Waltenberg

Bedrock

Lava

Granite 

Springs

Phantom 

Ranch

Diamond 

Creek

Pearce Ferry

Preliminary data, subject to review, do not cite
Water Surface Elevation: Comparison of Profiles
Water Surface Elevation: Comparison of Profiles

Waltenberg: 112.8 

• 1923 to 2000: 1.4 m vertical change, 

4 debris flows documented 

(Magirl et al. 2005)

• 2000 to 2021: no change within 

margin of error

Preliminary data, subject to review, do not cite
Granite Springs: 220.6

Water Surface Elevation: Comparison of Profiles

Debris flow in August 2016

May 2013 to

Oct 2016

Preliminary data, subject to review, do not cite
Riverbed Profile
Applanix 

Antennae

Multi-beam 

sonar

R10 

Antenna

Riverbed Profile – Data Collection
Riverbed Profile –

Data Collection

Typical channel mapping trip: 

map of entire reach, covering 

river left to river right

2021 trip: just the centerline 

swath

How well does the centerline swath 

represent the entire riverbed when 

it comes to change over time?
Riverbed Profile – Analysis Preliminary data, subject 

to review, do not cite

Change in mean bed elevation in Upper Marble Canyon

2013 to 2016 

(2021 swath)

2013 to 2016

Change in mean bed elevation in Lower Marble Canyon

In some cases, we 

may be able to use 

the centerline to 

tell us about the 

entire riverbed.
Mean bed elevation of centerline swath by river mile in Upper Marble Canyon

Preliminary data, subject to 

review, do not cite

Riverbed 

Profile –

Analysis
Change in Sand Mass for River Miles 0 – 30 

Measured via Sediment Gaging Stations

Riverbed Profile –

Analysis

2013 channel 

mapping survey

2016 channel 

mapping survey

2021 centerline 

survey

2014 2015 2016 2017 2018 2019 2020 2021

The change in mean bed elevation of the 

centerline swath is reflected in the change in 

sand stored in Upper Marble Canyon for 2013 

to 2021, showing a decrease from 2016 to 2021.

Preliminary data, subject to 

review, do not cite
Conclusion

• Updated continuous water surface elevation profile for 282 river miles

• Validated by total station survey within centimeters

• 245 miles have a reported GPS vertical error of < 10 cm, improving error from 

previous profiles

• We are still working on filling in profile where we do not have data with low vertical error

• Applications

• Detect changes since 2000 (and 1923)

• Update resources used by GCMRC scientists like flow models and digital shoreline maps

• Created riverbed profile of centerline swath for 282 river miles

• Can detect changes in some cases despite limited spatial extent compared to 

typical channel mapping operations

• Both surveys completed concurrently in ~1 week

Preliminary data, subject to review, do not cite
Thank you!