Researchers use LiDAR to Pinpoint Erosion Following Floods

By KBJR News 1

July 8, 2013 Updated Jul 9, 2013 at 9:52 AM CST

Duluth, MN (NNCNOW.com) - Jay Cooke State Park experienced some of the worst devastation in the 2012 floods.

The rushing waters washed out a big chunk of Highway 210, the park's main artery, and the soil beneath it.

The erosion is easy to spot, but that isn't always the case, especially in northern Minnesota.

"We don't have traditional flood plains. We have this giant slope. We have very different problems. What happens when water cascades down the hillside and the streams curves cause erosion," said George Host, an Ecologist at the Natural Resources Research Institute in Duluth.

Host is working to find those problem areas before they get worse.

His department is working with the Minnesota DNR to utilize LiDAR or Light Detection and Range to detect erosion.

That data is acquired by an airplane flying at about 6,000 feet.

"This device literally paints the surface with a series of laser pulses and using the speed of light and very accurate clocks, they can determine how far away the surface was from the sensor and then using a GPS, they can actually place that point in space," said Tim Loesch, the GIS section manager with the DNR.

The end result is a number of color coded points a meter and a half apart from each other, as seen in this LiDAR rendering of the Aerial Lift Bridge.

"You can make very detailed elevation maps that pull out things like buildings, trees, sometimes cars, and there is a lot of ecological application for that kind of data," said Host.

The Minnesota DNR wrapped up a LiDAR Survey of 70 percent of the state in 2011 at a cost of $7.5 million, a million dollars under the projected budget.

That extra money allowed DNR officials to once again survey a 3,000 square mile region following the floods, allowing for a very detailed comparison.

What researchers found were a number of erosion hotspots throughout the area, especially inside Jay Cooke State Park that could prove disastrous if not fixed in a timely fashion.

"Given the knowledge of what places are most likely to trap water or become eroded, we can do radiation techniques, stream bank stabilization, we got many tree planting efforts going on," said Host.

"I feel pretty strongly that we'll be able to quantify how much sediment was removed from hillsides and at least identify where some of it has gone," said Loesch.

The data for Minnesota is still in its infancy and carries some challenges, like its eight terabyte file size, but many agree it is, and will continue, to serve as a vital tool.

"I think this data will quickly go into decision making processes with PCA and EPA and groups looking to retain water quality and property values for the landscape," said Host.

Decisions that can be made with a click of the mouse, at a cost of 95 percent less than that of a survey crew on the ground.

"We're tickled as computer and data geeks. We live for getting this sort of data," said Host.

The Minnesota DNR is making it easy for everyone to access the data.

They will soon launch a web and mobile phone app putting the LIDAR information at your finger tips.

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Kevin Jacobsen
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