U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3063

August 2006

Monitoring Changes in the Platte River Riparian Corridor 

with Serial LiDAR Surveys

By Paul J. Kinzel and Jonathan M. Nelson (U.S. Geological Survey, Golden, CO) and C. Wayne Wright (National Aeronautics and 

Space Administration, Wallops Island, Virginia)

Printed on recycled paper

Airborne laser altimetry, also known as light 

detection and ranging (LiDAR), is an innovative 

mapping technology that precisely measures the 

time it takes for a laser pulse transmitted from an 

aircraft to be reflected from the ground surface 

back to the aircraft. The laser-ranging measurements are used in tandem with the position 

of the aircraft as determined with an onboard 

global positioning system (GPS) and inertial 

measurement unit (IMU) to map the elevation 

of the ground surface. Recently, the National 

Aeronautics and Space Administration (NASA) 

developed the Experimental Advanced Airborne 

Research LiDAR (EAARL) to survey coastal 

and shallow-water marine environments (fig. 1) 

(Wright and Brock, 2002).

 To investigate the possibility of extending the use of this system to shallow rivers, an 

EAARL survey was flown over the Platte River 

in central Nebraska in 2002 and 2005 to collect 

bathymetric and topographic elevation measurements in the river channel and along riparian 

areas. The elevation surfaces that were generated 

from flights along two river reaches highlight the 

unique capabilities of LiDAR and illustrate how 

these data can be used to monitor both natural 

and human alterations in the riparian corridor. 

Introduction 

The Platte River in central Nebraska (fig. 

2) is a wide, sand-bedded river that provides 

habitat for migratory water birds along the North 

American flyway. The central Platte River 

functions as critical habitat for the endangered 

whooping crane (Grus americana) and also is 

an important habitat for the endangered least 

tern (Sterna antillarum) (U.S. Fish and Wildlife 

Service, 1967, 1985a) and the threatened piping plover (Charadrius melodus) (U.S. Fish 

and Wildlife Service, 1985b). Upstream water-resource development over the last century 

has decreased the water and sediment supplied to the central Platte River (Williams, 1978; 

Eschner and others, 1983). This has resulted in vegetation encroachment and narrowing of 

Platte River channels. The National Academy of Sciences’ National Research Council, in a 

recent review of these critical habitat designations, concluded that the current morphology 

of Platte River channels is limiting the recovery of the endangered 

and threatened avian species (National Research Council, 2004).

Figure 1.  Illustration of an EAARL survey.
Habitat-enhancement efforts along the Platte River currently (2006) are focused on the clearing of vegetation from 

in-channel and riparian areas, whereas future plans propose 

the release of water from upstream dams as a means to prevent 

vegetation from encroaching on the active river channel (U.S. 

Department of the Interior, 2006). For this reason, monitoring 

the physical response of the river channel to these management 

treatments is an important component of a proposed habitat 

recovery program (Platte River Recovery and Implementation 

Program, 2005). Understanding the effects of management 

strategies on Platte River riparian habitat also is a key objective 

of the U.S. Geological Survey’s (USGS) Platte River Priority 

Ecosystem Program (http://mcmcweb.er.usgs.gov/platte/). This 

fact sheet describes applications of LiDAR to monitor changes 

in the Platte River riparian corridor.

Challenge—Mapping a Wide, 

Shallow River

Traditional methods for collecting bathymetric data in 

rivers vary with the depth of the channel to be surveyed. For 

rivers of sufficient depth to be navigated by boat, hydroacoustic 

sensors are the preferred technology. For shallow rivers where 

navigation is not possible, such as the Platte River, wading 

measurements typically are made with conventional laser theodolites or survey-grade GPS technology. Because of the width 

and topographic complexity of the Platte River, wading surveys 

are labor intensive and, therefore, are prohibitive for mapping 

detailed features in the channel, such as sandbars and islands, 

over long river reaches. 

Aerial photography has been used for documenting 

changes in Platte River planform (Williams, 1978; Eschner and 

others, 1983). Photogrammetric techniques could be used with 

aerial photography to derive ground-surface elevations, but 

difficulty in determining elevations below the water surface is 

a potential limitation to this approach. Conventional airborne 

laser-altimetry systems provide efficient elevation data collection over large areas, but their use in wetted areas is limited 

because these systems typically use a near-infrared wavelength 

of laser light that is attenuated in water. 

The EAARL System

The EAARL system is operated from a Cessna 310 aircraft 

and consists of a yttrium aluminum garnet (YAG) laser that 

produces up to 5,000 1.3-nanosecond duration, 70-microjoule, 

532-nanometer (blue-green) pulses each second. A blue-green 

wavelength of laser light is not attenuated as much as a nearinfrared and thus is capable of returning a pulse from an underwater target. A scanning mirror directs the spacing of individual 

laser samples along each swath. When the EAARL is operated 

at a 300-meter (m) altitude and is traveling at 50 m per second, 

the spacing of individual laser samples in a 240-m swath is 

2 m x 2 m in the center of the swath and extends to 2 m x 4 m 

on the edges of the swath. All transmitted and returned laser 

pulses are stored by the EAARL system. In addition, a highresolution color infrared digital camera and a lower resolution 

red, green, and blue digital camera obtain images of the area 

below the aircraft every second. The imagery and laser data 

collected from the EAARL flights can be viewed later, and 

elevation surfaces can be created by using the Airborne Laser 

Processing Software (ALPS). 

An EAARL survey was flown over the Platte River study 

area on March 26 and 29, 2002, and June 15, 2005. On these 

days, USGS personnel obtained detailed ground-truth measurements at study sites. These comparisons were used to evaluate 

the vertical accuracy of the system (Kinzel and Wright, 2002; 

Kinzel and others, 2006b). 

EAARL Application—The Cottonwood Ranch

The EAARL laser returns collected for the Cottonwood 

Ranch study site were processed by using a first-return algorithm that computes the ranging measurement to the ground on 

the basis of the centroid of the first peak in the returned laser 

backscatter. The Cottonwood Ranch, owned by the Nebraska 

Public Power District, is a property along the Platte River that is 

Figure 2.  Study area along the Platte River in central Nebraska.
undergoing habitat enhancement for the endangered and threatened species (figs. 2 and 3) (Kinzel and others, 2006a). These 

enhancements include the clearing of riparian trees to increase 

the sight distance for roosting whooping cranes and lowering 

the elevation of islands to provide potential nesting sites for 

terns and plovers. 

Examination of the EAARL first-return surfaces collected 

for the Cottonwood Ranch illustrates the effect of these habitat 

enhancements on the riparian corridor. The trees (shown in red 

in fig. 3A) along the north bank of the river were present on the 

March 29, 2002, EAARL first-return surface. The trees are no 

longer present on the June 15, 2005, EAARL first-return surface 

(fig. 3B). 

Although traditional aerial photography could be used 

for detecting such changes, the LiDAR surfaces also permit 

examination and quantification of changes in the vertical relief. 

LiDAR can be used to determine the height of tree canopies or 

measure the change in elevation of the island in the center of 

the image. This island was graded to a lower elevation, and a 

channel was cut through it to create a tern and plover habitat 

(fig. 3B). Viewshed analysis of these surfaces also could be 

performed easily in a geographic information system (GIS) to 

determine the sight distance across the river for roosting cranes.

EAARL Application—The Rowe Sanctuary

An EAARL survey also was flown over the National 

Audubon Society’s Lillian Annette Rowe Sanctuary (Rowe 

Sanctuary) (figs. 2 and 4). This reach of the Platte River is an 

important roosting site for sandhill and whooping cranes. Vegetation encroachment in this reach is controlled by annual clearing of the sandbars. The EAARL surfaces collected on March 

26, 2002, and June 15, 2005, were processed with a first-return 

algorithm and a bathymetry algorithm (figs. 4A, B). Comparison 

between these surfaces shows that the morphology of sandbars 

in this reach had changed. The sandbars from the June 15, 2005, 

surface are incised more than those from the 2002 surface. This 

is because streamflows during the intervening period were at 

historical lows and the water was concentrated into narrow 

channels. 

In addition to providing a means to detect elevation 

changes in the in-channel morphology, EAARL data can be 

imported into the USGS’s Multi-Dimensional Surface Water 

Modeling System (MD_SWMS) (http://wwwbrr.cr.usgs.

gov/projects/SW_Math_mod/OpModels/MD_SWMS/index.htm).

MD_SWMS can be used to simulate spatially explicit distributions of water depth and velocity for various streamflows. This 

methodology has been used to assess roosting habitat for sandhill cranes in the Platte River (Kinzel and others, 2005). 

References

Eschner, T.R., Hadley, R.F., and Crowley, K.D., 1983, 

Hydrologic and morphologic changes in channels of the 

Platte River basin in Colorado, Wyoming and Nebraska—A 

historical perspective: U.S. Geological Survey Professional 

Paper 1277–A, 39 p.

Kinzel, P., Nelson, J.M., and Heckman, A.K., 2006a. Channel 

morphology and bed-sediment characteristics before and after 

riparian vegetation clearing in the Cottonwood Ranch, Platte 

River, Nebraska: U.S. Geological Survey Scientific 

Investigations Report 2005–5285, 25 p.

A. March 29, 2002

Elevation, in meters

B. June 15, 2005

Figure 3.  Elevation surfaces (referenced to the North American Vertical Datum of 1988) of the middle channel of the Platte River on the

Nebraska Public Power District’s Cottonwood Ranch property. The surfaces were created with ranging measurements computed with the

EAARL first-return algorithm.
Kinzel, P.J., Nelson, J.M., and Parker, R.S., 2005, Assessing sandhill crane roosting habitat along the Platte River, 

Nebraska: U.S. Geological Survey Fact Sheet 2005–3029, 

2 p.

Kinzel, P.J., and Wright, C.W., 2002, Evaluation of EAARL, an 

experimental bathymetric and terrestrial LiDAR for collecting river channel topography along the Platte River, Nebraska 

[abs.]: Geological Society of America Abstracts With Programs, v. 34, no. 6, p. 232.

Kinzel, P.J., Wright, C.W., and Nelson, J.M. 2006b, Application of an experimental airborne laser scanner for surveying a 

braided river channel, in Proceedings of the 8th Federal Interagency Sedimentation Conference, April 2–6, 2006, Reno, 

Nev. : Subcommmittee on Sedimentation, CD-ROM, 8 p.

National Research Council, 2004, Endangered and threatened 

species of the Platte River: Washington, D.C., National 

Academies Press, 336 p.

Platte River Recovery and Implementation Program, 2005, 

Attachment 3, section V. Final draft—December 7, 2005: 

Available at http://www.platteriver.org/library/

Program-Document-Dec-2005/Program.pdf and 

accessed June 1, 2006.

U.S. Department of the Interior, 2006, Platte River Recovery 

Implementation Program, Final environmental impact statement: Available at http://www.platteriver.org/ and accessed 

June 1, 2006.

U.S. Fish and Wildlife Service, 1967, Endangered species 

list —1967: Federal Register, v. 32, FR4001. 

U.S. Fish and Wildlife Service, 1985a, Interior population 

of least tern to be endangered: Federal Register, v. 50, 

FR221784-21792.

0 0.1 0.2 0.3 0.4 0.5 KILOMETER

Elevation, in meters

632.00

628.00

0 0.1 0.2 0.3 MILE

N

0 0.1 0.2 0.3 0.4 0.5 KILOMETER

Elevation, in meters

632.00

628.00

0 0.1 0.2 0.3 MILE

N

Figure 4. Elevation surfaces (referenced to the North American Vertical Datum of 1988) of a reach of the Platte River that passes

through the National Audubon Society’s Rowe Sanctuary. These surfaces were created with ranging measurements computed by

using the EAARL first-return and bathymetry algorithms.

U.S. Fish and Wildlife Service, 1985b, Determination of 

endangered and threatened status for piping plover: Federal 

Register, v. 50, FR50726-50734. 

Williams, G.P., 1978, The case of the shrinking channels—The 

North Platte and Platte Rivers in Nebraska: U.S. Geological 

Survey Circular 781, 48 p.

Wright, C.W., and Brock, J.C., 2002, EAARL— A LIDAR 

for mapping coral reefs and other coastal environments, in

Proceedings of Seventh International Conference on Remote 

Sensing for Marine and Coastal Environments, May 20−22, 

2002, Miami, Florida; National Oceanic and Atmospheric 

Administration, 8 p.

For more information, contact:

Paul J. Kinzel

U.S. Geological Survey 

Geomorphology and Sediment Transport Laboratory

4620 Technology Drive, Suite 400, 

Golden, CO 80403 

pjkinzel@usgs.gov

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

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

Government.

A. March 26, 2002 B. June 15, 2005