Currents on Chichagof Island mapped using high resolution digital elevation data. (Photo courtesy of Terrainworks)

Alaska may have five times as many streams as previously thought, according to a group of scientists and programmers who have mapped the state for nearly a decade.

lee benda runs terrain work, A company that maps natural landscapes. He says many state and federal agencies rely on the National Hydrography Dataset which charts known waterways.

“The problem with the dataset is that the mapping accuracy is poor to fair,” Benda said. “He lacked a large number of springs and rivers because he was drawing them from photographs and interpreting their location even under dense vegetation.”

Benda’s team created the new maps based on state-of-the-art high-resolution digital elevation data collected by the aircraft. And it led to some dramatic discoveries.

“On northern Chichagof Island, west of Juno, we observed a 518% increase in the channel length of the network in that island, based on high-resolution digital data,” Benda said. “It was eye-opening to see all those streams that are missing on current maps.”

Benda’s new maps have already revealed nearly 200,000 miles of new streams in Alaska. That’s enough current to go around the world seven times! And so far, they have mapped only half of the state. Benda says all of this matters for two big reasons. First, the fish habitat.

“Well, if you’re going to protect fish habitat, you have to know where the habitat is,” Benda said. “And so with advanced mapping and the discovery of all these, what I would call missing streams, there are also missing salmon habitats that have been identified.”

and second, natural disasters.

“At the same time flood plains are also mapped, so you know exactly where you are exposed to flooding,” Benda said. “And at the same time, small tributaries from the mountains carry landslide debris and hit homes on lower-sloping land.”

Terrain Works is now collaborating with the US Geological Survey to improve mapping in the Yukon Territory and the St. Lawrence Islands. They will also work with the US Forest Service to uncover hidden watercourses on the Prince of Wales Islands in the coming months.

You can hear about Benda’s work during his presentation, “Searching for Missing Streams and Salmon Habitats,” which will take place Thursday, August 17 at 6:30 p.m. at the Petersburg Public Library.




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