What's an engineered logjam, and why does the Boise River need them?
Flood control, development and recreational floating have combined to strip fish habitat from the Boise River.
Ada County and Idaho Fish and Game have partnered to put some back in an unusual project for a metro area.
Three engineered logjams and dozens of boulders are being added to a 500-foot stretch of river between the Eckert Road bridge and the Barber Park boat ramp, where the popular summer floating route begins.
“It’s one of the problems of a developed area — people take the wood away from the river, and then the rivers become devoid of fish habitat,” said Jeanne McFall, the fisheries engineer leading the project for Idaho Fish and Game. “By being able to add the wood back, it really benefits the fish.”
McFall usually does her work in remote areas of the state to improve habitat for steelhead and Chinook salmon because of the mitigation funding dedicated to those fish.
This is the first project of its kind in the Boise River.
“A river like this, where you’re coming out of the mountains and you hit a broad, flat valley, is generally very meandering with a wide floodplain and a lot of input of trees and woody material,” said Joe Kozfkay, regional fisheries manager for Fish and Game. “As we’ve encroached on the river, we’ve made it a single thread and pulled out most of that wood. When you have that channelized stream profile, there isn’t a lot of resting areas for trout, especially when flows go up to 6,000 to 7,000 (cubic feet per second). Most of the velocities in the river ... are suboptimal for trout.”
The logjams and boulders will create sheltered areas for fish to rest, hide from predators and feed on bugs.
Work began Nov. 15 and is scheduled for completion by the end of this week. Some cleanup work on the area, particularly the gravel walking path on the north side of the river, will take a little longer.
“It’s definitely going to attract anglers,” Kozfkay said.
‘Testy,’ but no lawsuit
Ada County spent $45,000 on the river project in the aftermath of a power outage at the county-owned Barber Dam in February 2015. The dam is about a quarter-mile upstream from Barber Park. The outage lasted 7-8 hours and led to the river flow dropping below the winter minimum of 240 cfs. A handful of juvenile fish were found dead.
“Although there’s no data to really determine if that resulted in any significant issues to the fishery, you surmise that there were,” said Scott Koberg, the director of Ada County Parks and Waterways.
The county and dam operator Enel Green Power North America (EGP-NA) made upgrades to the dam to prevent future outages, Koberg said. The county also formed the Ada County Environmental Advisory Board and searched for a project to improve the river’s fish habitat. The Barber Park-area project was selected.
EGP-NA contributed to the project’s cost.
“If this would have happened in a lot of other states, there’d be lawsuits involved,” Kozfkay said. “I think it’s pretty unique that we came to a sort of commonsense compromise without any of that happening. ... We got through it. It was a little testy maybe at the start, but people got over that and I think we made good things happen in no time.”
Recycling tree stumps
The project area already was popular with local anglers. Barber Park is one of Fish and Game’s regular stocking sites.
The river features wild rainbow trout, brown trout and mountain whitefish. The stocking program adds hatchery rainbow trout, steelhead and Chinook salmon.
Now, the area could be one of the best spots for fish in town.
“It’s a pretty nice little fish hole, fish hangout,” McFall said as she explained one of the engineered logjams.
The project calls for two logjams on the north bank of the river and one on the south bank. Several tree stumps with root wads still attached are placed with the roots sticking out into the river in each logjam. They’re attached to wooden structures that are buried 10-12 feet into the ground for support. The stumps were brought in from the Broadway Bridge project on the river.
A hole is dug below the logjam to create a pool for fish.
The structure will be completely underwater in higher flows.
“We want it to appear natural,” McFall said, “and we also don’t want it to go anywhere. That’s why it’s called engineered.”
The boulders will be placed in clusters in the river and create some visible disturbances on the surface. Pools will be dug behind them as well.
“You don’t want to have one long run,” McFall said. “That’s not good for fish habitat.”
The project is part of what Koberg calls a “progressive” effort to improve the river for fish after years of altering it for the good of people. For example, the past couple years Ada County has moved some wood debris in the river out of the floater path but left it in the river to create fish habitat.
“It’s all about that balance now,” Koberg said.
And he hopes this project proves an example of how that can be accomplished.
“We’re excited about the outcome and then monitoring it over time to see what it does,” he said. “People come here to fish all the time. We hope that this becomes an even better location.”
Fishing in the Boise River contributes $2 million in direct expenditures to the Treasure Valley economy, Kozfkay said.
“What that must do for property values?” he said. “Having a trout stream in your back yard? That’s almost incalculable.”