The Middle Channel reef project is supported by grants from the National Oceanic and Atmospheric Administration and the U.S. Fish and Wildlife Service through the U.S. Environmental Protection Agency’s Great Lakes Restoration Initiative. Led by Michigan Sea Grant, this project is part of a long-term collaboration among federal, state and private groups interested in restoring valuable native fish populations in the Huron-Erie Corridor. USGS water flow velocity and depth models were used to determine ideal reef placement within the river. Further, USGS is leading the pre-/post- reef construction egg and larval fish assessments.

The data that are shown in the fly-through are a composite of multiple scans that were collected with a ground-based lidar (light detection and ranging) scanner, which uses high-speed laser measurements to produce highly accurate three-dimensional maps of the riparian environment. By combining these measurements with digital images from an onboard camera, 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 with precise elevation and geographic position. Cobble bars, gravel beds, bluffs, riverside vegetation and man-made features are all visible in the data. Each feature can be queried for size, geographic position and precise elevation.

The river system shown in this 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 United States Geological Survey (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. As part of the last survey before dam removal began in September 2011, scientists from the USGS conducted the ground-based lidar survey to accurately map the lower river in great detail. This data set will be compared with measurements from future surveys to monitor and quantify changes that occur in the river system after the two dams have been removed.