BLM  Builds  Cascades  On  Siuslaw
August 31, 1998
©The Register-Guard - Used with permission

You don't see this every day: a huge yellow excavator in the middle of the Siuslaw River, grabbing and stacking boulders as it runs up and down the stream bed.

But sometimes, desperate measures are needed for desperate times. Oregon's wild coastal coho salmon runs, which once numbered about 1 million, have dwindled to less than 25,000.

"There's been some nasty things done to this watershed," says Leo Poole, fish biologist for the U.S. Bureau of Land Management's Eugene District. "We've basically denuded the whole river. ... We've got to do something."

Last month, the federal government listed coho as threatened under the Endangered Species Act. But wild coho populations are expected to drop again this year.

"It's a critical time for the fish," Poole says. "Things are going downhill very quickly."

The Siuslaw River once accounted for almost a quarter of the historic run of wild coho but now has only a few thousand fish. Ocean conditions and loss of habitat along streams are blamed for much of the decline.

So this summer, the BLM is installing more than a half-dozen "cascades" along the Siuslaw near Alma, about 30 miles upstream from where the river pours into the Pacific Ocean at Florence. More than 700 tons of rocks are being piled across the river.

The boulders and large logs are intended to provide habitat for salmon so they can feed and spawn. But the cascades also are intended to build up the river bottom, which has been lowered by the effects of intense logging, removal of large conifers along the river and construction of the road that runs next to the river.

One of the new structures is 8 feet high. Poole says the river bottom should rise back to its near-natural state if sediments and gravel slowly build up behind it and in front of it.

Juvenile fish should be able to swim through openings in the rocks. And adults won't have trouble going upstream in the winter, when the river runs higher, Poole says.

"We're just trying to bring the stream channel back up," he says. "By itself, it would take a hundred years or more to get back to something close to natural conditions. But we don't have that much time."

For example, "this time of year, we have lethal water temperatures for salmon" in the Siuslaw, Poole adds. The 65 degree to 70 degree water largely results from logging that has removed conifers from along the Siuslaw and tributaries.

The cascades should help cool water by creating deeper pools and shade under logs.

The $160,000 project is being funded through the federal government's "Jobs in the Woods" program, which employs loggers who've been hit hard economically by federal timber harvest cutbacks.

The project is also one of hundreds of stream-restoration efforts launched this decade as state and federal agencies try to figure out ways to save the Northwest's dwindling wild fish populations.

Stream-restoration projects have been controversial, largely because they are unproved.

Some environmentalists also question how effective the projects are without also fixing roads that might wash out and without limiting upstream clear-cutting, which can cause erosion and landslides.

Poole says the idea of a cascade, or large rock and log structure to block much of the water, came from his observations of natural conditions. A smaller cascade installed three years ago on Wolf Creek, a tributary of the Siuslaw, resulted in significant increases in juvenile salmon.

"It's a bit unorthodox, I'll admit," Poole says. But he's seen chinook salmon in the Siuslaw try to spawn in gravel that's only 2 inches to 6 inches deep when they need at least a foot.

But he also says that streamside tree buffers ought to be widened on private timberlands, which cover much of the Siuslaw's watershed. The federal government has been pressuring the state of Oregon to do just that.

Indeed, just upstream from the Siuslaw restoration project, loggers have stripped trees from a long stretch of the river, except for a narrow buffer near the water.

And as for the heavy equipment in the stream, Poole says he worried at first about churning up sediment.

Most equipment has been banned from rivers such as the Siuslaw for decades, except for special restoration projects.

But Poole says his concerns were eased after water tests a mile or two downstream showed no increase in sediments.

"We're looking at a couple hundred years before we get enough large conifers to shade the river," Poole says. "We're trying to help things along a little bit."