Part 3: Development Pressure Narrows the Boise River Channel

Narrow channel of the Boise River, Aerial view

By Steve Stuebner

As the Boise River Greenbelt project started to get more momentum in the 1970s – the project was originally conceived in 1962 by the Boise City Council – more people were paying attention to Flood District 10 maintenance activities on the river, officials said.

As more miles of Greenbelt were built, the riverbanks became more appealing to business and residential developers. At the same time, developers built levees along the Boise River channel in the downtown core to allow development to occur in the old flood plain.

“Up to the 1970s, people were pretty content to not build in the flood plain,” Susan Stacy, author of When the River Rises: Flood Control on the Boise River 1943-1985, said in a 1993 video produced by the Bureau of Reclamation. “And then after the Greenbelt made the river beautiful, popular, and aesthetically pleasing, and people were floating down it, property owners and developers thought, oh, here’s a value. We ought to build houses as close to the river as we can because obviously, people want to be right next to it.”

An overhead view looking down at the Boise River Greenbelt shows a tight space
between the river, the pathway, and homes nearby.

That led the cities along the river and Ada County to work toward development ordinances that applied a flood standard of 6,500 CFS to the Boise River corridor -- a standard that still exists today. That made the job of Flood 10 more difficult because the river channel was narrowed as development occurred in Boise, Garden City, and Eagle through the 1970s and 1980s. A tighter river corridor focused more of the river’s energy into a smaller space, officials said.

When the Boise River exceeds 6,500 cfs, it threatens homes in the flood plain,
especially in the Eagle Island area. 

For example, if the river banks were repaired and shored up on one side of the river, that would push the energy and impact of high water flows toward the bank on the other side or a riverbank farther downriver.

The river’s width was narrowed from an average of 900 feet wide – or three football fields wide – prior to the construction of Anderson Ranch and Lucky Peak dams, with an average peak flow of 10,700 cubic feet per second (CFS), to an average of 140 feet wide (half the length of a football field), and average peak flow of 3,700 CFS.

A Statement of Intent from the Flood 10 commissioners dated August 26, 2003, explains the quandary: “The District believes that land-use changes significantly affect flood plain conveyance and storage, affecting individual sites and reaches above and below these sites,” the statement says.

“Development in the flood plain, combined with lack of channel-forming flow events, sediment erosion and deposition, and the growth of gravel bars and associated vegetation, reduces the conveyance capacity of the Boise River and increases flooding risks.”

“The most pressing issue facing the District in the future – minimizing flood impacts in the face of rapid growth – requires river maintenance and protecting unimpeded access to the river,” Flood 10 commissioners said.

In the late 1980s, more pressure came from the Idaho Department of Fish and Game, the Idaho Division of Environmental Quality and Idaho Rivers United (IRU) to ensure that any streambank work or stream-alternation projects to address flood damage were done in a way that met state and federal law.

“By then, there were more eyes on the river than ever before,” said Erv Ballou, Assistant Project Manager of Flood 10. Ballou reviewed stream-alteration permits for 39 years for the Idaho Department of Water Resources. “Fish and Game and IRU would review the stream-channel alteration proposals, put them under the microscope, and then they’d give feedback to us at IDWR,” he said.

Cottonwood groves flooded by the Boise River is a normal occurrence
that benefits plants and wildlife in the flood plain.

Conservation and fishing groups wanted to maintain more woody debris on the stream banks for trout habitat. They were concerned about how much gravel could be removed from the river, the impacts of heavy equipment on the river environment, etc.

“There was a real evolution in river management during that time,” Ballou said. “We had the direction from the IDWR Director and the Legislature to allow the river work to occur, but we told Flood 10 and anyone else trying to do riverbank repairs, you’ve got to do it right.”

While working for IDWR, Ballou recalls working with the cities and the county to push for wider development setbacks than were approved along the Boise River to allow for flooding and flood repairs and reserve space along the river’s edge for riparian habitat.

“I was asking for 75- to 100-foot setbacks minimum, but the planning and zoning officials were telling me 25 feet is the best we can do. In some places, the set back is only 10 feet between the water’s edge and the Greenbelt.”

By this time, Flood 10 had its first paid staff member, LaRue Bevington, in 1987, serving at the pleasure of the three commissioners guiding the flood district at the time. The paid staff allowed the district to focus more attention on winter maintenance activities, secure stream-alteration permits for the maintenance work, and coordinate with other governmental entities that oversee growth and management of the Boise River corridor.

Through the 1980s and 1990s, thousands of homes and many office buildings were built along the Boise River corridor. The Greenbelt expanded west to Eagle, with a long-term goal of connecting to Eagle Island State Park. Much of the Greenbelt has become a “floodway,” a buffer of sorts between the river and buildings or homes nearby.

Boise River 2000 Diversifies Viewpoints on Boise River Management

The Boise River 2000 study helped bring people and stakeholders with diverse points of view together to discuss river management issues, looking ahead to future needs.

Flood 10 Chairman Bill Clayton remembers talking to a number of groups like IRU and others about Boise River management in those days.

Tom "Chel" Chelstrom, an active canoeist, was an active participant in Boise River 2000.

“I’d start with my black hat on, and I’d say, I’m chairman of Flood District 10, and we cut trees out of the Boise River. And then I’d put on my white hat and say, I’m also a catch-and-release fly fisherman, and I’m committed to preserving the natural character of the Boise River channel. Believe it or not, we can do both and enhance the river in the future.”

As the different stakeholders met together over several years, they developed friendships and relationships of trust. “We have to recognize that we’re not all necessarily enemies here,” Tom “Chel” Chelstrom of Boise remembers telling the Boise River 2000 committee. “Recreation and business can be partners in keeping a healthy river and improving the river.”

Added Clayton, “We must step forward with a long-term solution so we can look at habitat, water users, flood control, recreation – all at the same time. I think we are getting there.”

Next: Part 4: Snowmageddon 2017 - 101 Days of Flooding on the Boise River


For more information about Flood Control District 10, contact Mike Dimmick, District Manager

For feedback on the stories, contact Steve Stuebner