What could be the highest return in decades of fall chinook salmon to Bear Creek this fall might not get past downtown Medford, thanks to two obstructions beneath the Jackson Street bridge.
A concrete slab under which the creek has flowed the past two years has partially collapsed, forcing the creek to gurgle through several underground outlets that may or may not be large enough for adult chinook to navigate like they did last year.
Even if they can make it, they’ll have to contend with the same abandoned sewer pipe that biologists believe needs altering to push the creek through a makeshift fish ladder they recently crafted with sandbags and creek rock.
Together they make fish passage sketchy at best under the bridge, just as these behemoths are migrating up the Rogue River and could be in Bear Creek any day now.
“So what’s a chinook to do?” said Pete Samarin, a fish biologist with the Oregon Department of Fish and Wildlife. “This is not good. It’s an enormous fish-passage headache. We need to do something, and we need to do it quickly because the fish are coming.”
The fish-passage woes are the latest saga to play out under the bridge, where biologists and Medford officials would like to remove the two obstacles. However, the Oregon Department of Transportation doesn’t want to see any disturbance there until a yet-to-be-funded engineering study ensures that removal won’t over time trigger erosion problems at an Interstate 5 viaduct abutment upstream in Hawthorne Park.
The current passage problems were created when the Jackson Street Dam was removed from the creek two decades ago, creating upstream “head cut” erosion exposing the decommissioned sewer pipe and a rock-and-concrete structure that once protected fiber-optic cables spanning the creek well under the creek bed.
Last year, the impediments created a concrete bridge across the creek with the water flowing about 15 feet underground before entering a large pool. Upstream-migrating chinook swam underground through the waterway before reaching the sewer pipe.
However, part of that concrete recently collapsed, and now garbage and other Bear Creek Valley detritus doesn’t flow through, and water seems to filter out in a half-dozen locations.
“You can’t tell if chinook will be able to make it through that thing or not,” Samarin said.
If the chinook can’t make it through, ODFW technicians could be forced to sweep nets through the downstream hole to capture chinook and carry them upstream past the obstructions for several weeks, Samarin said.
“That’s not good for adult chinook to be handled a lot like that,” Samarin said. “Then again, it’s not good to be stuck in that pool.”
If they can traverse the first obstacle, they’ll need help getting over the pipe, Samarin said.
Possible solutions include affixing rubber baffles to the top of the pipe so all the flow is pushed to the creek’s west bank, where the sandbag fish ladder was built recently, Samarin said.
After decades of poor showing, fall chinook have made a comeback in Bear Creek in recent years, with chinook regularly reaching Ashland and even as far as Emigrant Creek toward the base of Emigrant Dam.
Returns to the Rogue Basin were forecast this year to eclipse 130,000 adults, which is about 50 percent more than last year.
While there is no estimate for how many are headed up Bear Creek this late summer and fall, their stamina in getting past Medford’s obstacles could determine how far up the system they’ll get this year.
“I don’t think we’ll have reports of chinook in Emigrant Creek if they have to waste all their energy here,” Samarin said.