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New Video Shows a Virtual Fly-Through Along the Lower Elwha River, Washington, Using Recently Acquired Ground-Based Lidar Data



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The U.S. Geological Survey (USGS) recently released a short video that takes the viewer on a virtual flight down the lower Elwha River on Washington’s Olympic Peninsula. The video—posted on the USGS YouTube channel at http://youtu.be/0tEvz-rEz3Q—was created from ground-based lidar (light detection and ranging) data collected in September 2011 as part of USGS work investigating how the removal of two large dams on the Elwha will affect the river system downstream. (See “Elwha Dam Removal Begins—Long-Planned Project Will Restore Ecosystem, Salmon Runs,” Sound Waves, November/December 2011.) The video begins about 0.8 river kilometers upstream (south) of the bridge on Elwha River Road. The virtual flight path then proceeds downstream approximately 5.5 kilometers, in a northerly direction, to the mouth of the river on the Strait of Juan de Fuca.

Screenshot from recently released USGS video that takes the viewer on a virtual flight through lidar (light detection and ranging) data collected along the lower Elwha River Josh Logan and Amy Draut of the USGS collecting lidar data on the lower Elwha Rive
Above Left: Screenshot from recently released USGS video that takes the viewer on a virtual flight through lidar (light detection and ranging) data collected along the lower Elwha River, Washington. Location is approximately 500 meters upstream from the bridge on Elwha River Road. Black "holes" in data (see prominent one in lower third of image) are sites where the lidar scanner stood; because of limitations in the scanner's vertical field of view, no data are collected immediately below the scanner. Likewise, the water surface appears black because it is not measured by the scanner. [larger version]

Above Right: Josh Logan (left) and Amy Draut of the USGS collecting lidar data on the lower Elwha River, Washington, on September 14, 2011, less than a week before removal of two large dams commenced on September 17. Photograph by Justin T. Minear, USGS. [larger version]

The data shown in the fly-through are a composite of multiple scans collected with a ground-based lidar scanner, which uses high-speed laser measurements to produce highly accurate three-dimensional maps of the surrounding environment. By combining these measurements with digital images from a camera mounted on the scanner, the instrument produces three-dimensional “point clouds” that can be displayed in true color. Because the water surface is not measured by the lidar scanner, it appears black in the video. Each of the millions of data points represents a discrete measurement of precise elevation and geographic position. Cobble bars, gravel beds, bluffs, riverside vegetation, and manmade features are all visible in the data. Using the appropriate software, each feature can be queried for size, geographic position, and precise elevation.

Amy Draut of the USGS collecting lidar data near a large bluff on the lower Elwha River Lidar image of bluff
Above Left: Amy Draut of the USGS collecting lidar data near a large bluff on the lower Elwha River, Washington, on September 14, 2011. The same bluff appears in the lidar image at right. Photograph by Justin T. Minear, USGS. [larger version]

Above Right: Lidar image of bluff in photograph at left. Colors in this image indicate the intensity of light returned to the lidar scanner (reds and yellows for higher intensities, greens and blues for lower intensities), which is a function of distance from the scanner as well as of the texture of the reflecting surface. Black "hole" surrounded by yellow and orange near bottom of image is one of the sites where the scanner stood; because of limitations in the scanner's vertical field of view, no data are collected immediately below the scanner. [larger version]

The river system shown in the video is downstream from the Elwha and Glines Canyon Dams, both of which are being removed in the largest dam-removal project in U.S. history. For nearly a century, these dams have been preventing salmon and steelhead from accessing historic spawning habitat above the dams. The dams have also been blocking the natural supply of sediment to the lower river and the nearby coastal beaches. Beginning in 2006, scientists from the USGS have been monitoring seasonal changes in the river channel below the dams to serve as a baseline with which to compare post-dam-removal changes in the future. Just before dam removal began in September 2011, scientists from the USGS conducted a ground-based lidar survey to map the lower river in great detail. This data set will provide scientists with an accurate snapshot of the lower river before dam removal. The elevation models produced from these data will be compared with measurements from future surveys to monitor and quantify changes that occur in the river system as it responds to dam removal.

To view the video—produced by scientists Joshua Logan and Amy Draut of the USGS Pacific Coastal and Marine Science Center, Santa Cruz, California, and Justin T. Minear of the California Water Science Center, Sacramento—visit the USGS YouTube channel at http://youtu.be/0tEvz-rEz3Q.

To learn more about the USGS science supporting Elwha River restoration, visit http://walrus.wr.usgs.gov/elwha/. For additional information about the Elwha River Restoration project, visit the National Park Service’s Elwha River Restoration Web site at http://www.nps.gov/olym/naturescience/elwha-ecosystem-restoration.htm.

 

Related Sound Waves Stories
Elwha Dam Removal Begins—Long-Planned Project Will Restore Ecosystem, Salmon Runs
Nov. / Dec. 2011

Related Web Sites
Video: Lower Elwha River, Ground-Based Lidar Fly-Through
USGS
Elwha River Restoration Project
USGS
Elwha River Restoration
National Park Service

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Maps Based on Satellite Telemetry Help Tanker Avoid Sea Ducks

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How Often Do Sediments on the Seafloor Move?

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Monterey Bay Marine GIS Users Meeting

Staff Ph.D. Student Researching Marine Mineral Deposits

Dutch Student Visiting USGS in California

Publications New Video Shows Virtual Fly-Through Along Lower Elwha River

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