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BLM finds the tiny beginnings of big waterways

Gordon Stokes, Victoria Jones and Carla Rothenbuecher, left to right, identify a stream inception point at 1,200 feet in the Oregon Coast Range, outside Eugene. (Jonas Parker, BLM)
Thursday, June 25, 2020

Even a creek with no name deserves some recognition.

This spring, hydrologists with the Bureau of Land Management hiked into the Coast Range foothills outside Eugene to document a stream inception point, where the water first bubbles to the surface.

At 1,200 feet elevation, a barely gurgling stream channel may be only inches wide, just strong enough to move some dirt and pine needles around, said Jonas Parker, a BLM hydrologist based in Salem.

“You would literally need to get down on your hands and knees to see that scour and channel,” Parker said.

So how does a hydrologist find such a hidden waterway too small to even make a sound? Old-school training. It requires the ability to identify plants that live near flowing water. Yet the implementation and widespread use of aerial laser imagery helps, too.

Lidar, short for light detection and ranging, is able to see through the vegetation to provide an incredibly detailed scan of the Earth’s surface. BLM field scientists use the imagery in a number of ways.

Hydrologists are able to see indentations, natural ridges where water might be likely to pool or flow.

Then the on-the-ground exploration begins, or, as Parker said, when the “physical and biological attributes combine.”

Once in the field, hiking through dense Oregon Coast Range forest, spotting plants such as ferns, skunk cabbage and devil’s club are sure signs a riparian area and flowing water are nearby.

BLM hydrology technicians in northwest Oregon have surveyed more than 225 miles of stream so far this year, Parker said.

The findings are helpful in assessing habitat for fish or establishing riparian buffer zones needed for future timber harvests.

Although unnamed, the water flowing out from the inception point discovered in late April can be traced to nearby Swartz and Lake creeks, and then the Siuslaw River, and finally, the Pacific Ocean.

The BLM manages more than 245 million acres of public land in 12 western states, including Alaska.

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