FAIRBANKS — The decades-old practice of dumping old vehicles, chunks of concrete and large rocks into the Chena River to stabilize eroding riverbanks might be nearing an end.
A riverbank restoration technique developed by the U.S. Fish and Wildlife Service that uses giant, spruce root wads anchored into the riverbank is taking hold in Fairbanks.
Great Northwest recently used the technique to reinforce a 200-foot long section of riverbank behind the Fairbanks North Star Borough building on Pioneer Road as part of a riverbank stabilization project spearheaded by Festival Fairbanks, a nonprofit community service organization.
The Fairbanks contractor excavated the riverbank last weekend and “planted” 42 white spruce root wads to build what is essentially a retaining wall of root wads along the riverbank.
The root wads, which have eight to 10 feet of tree trunk still attached, were laid perpendicular to the river on top of a “footer” log that was entrenched in the river bottom near the water’s edge. The root wads face the water and run parallel to the river.
Another “header” log is placed on top of the root wad trunks, just behind the root wad, and a piece or rebar is driven through all three logs to pin them together. Likewise, another header log is pinned in place at the end of the trunk of the root wad to hold them in place.
The result is a crib-like foundation that is then covered with rock and gravel, a bed of willow cuttings and top soil to produce what eventually should grow into a healthy vegetative mat that will hold the riverbank in place.
“It all becomes one entity tied together,” Gordon Schlosser, landscape architect for Fairbanks construction company Great Northwest, Inc., said. “It’s not rocket science; it’s common sense if you spend any time in the woods and look at riverbanks that are solid.”
The restoration project was funded by a $66,000 grant Festival Fairbanks received through the U.S. Fish and Wildlife Service’s “Partners for Fish and Wildlife Program” and a matching $33,000 grant from the Fairbanks North Star Borough.
The U.S. Fish and Wildlife Service has been using the root wad technique for riverbank stabilization on the Kenai River for more than 10 years with great success, said Julie Jones, executive director of Festival Fairbanks.
“They’re finding it to be quite successful, especially as far as maintaining fish habitat,” she said. “It’s just a great technology.
“The old days of throwing junk cars, old concrete and rocks on the riverbank may become a thing of the past,” Jones said.
When the borough building was constructed in the early 1980s, all the deep-rooted riparian plants along the riverbank were removed and replaced with grass, she said. Even though the riverbank behind the borough building was still in fairly good condition and would have lasted for several more years because it’s not on a bend in the river, Jones said the riverbank would have eventually been eaten away as a result of wakes produced by passing motorboats.
“There were a lot of cracks going up the riverbank, and the vegetative mat was hanging over the bank,” Jones said. “When boats come by, the water from the wake slips up under the vegetative mat, and the soil starts to wash away.”
Other property owners have used the same technique to stabilize riverbank along Chena, Jones said. The Binkley family, owners of Riverboat Discovery, received a grant to install root wads to reinforce the riverbank where they dock their sternwheeler this summer, she said.
“They have to use jet propulsion to push the boat away from bank, and the jets of water were digging away at riverbank,” Jones said. “They had plan to put in a big retaining wall and hard dock and then heard about this technique and decided to try it.”
The riverbanks stabilization projects are part of Festival Fairbanks’ plan to build a foot path on the north side of the Chena River from Peger Road to the William Ransom Wood Centennial Footbridge in downtown Fairbanks. The organization is in the process of trying to raise $5 million for the project, Jones said. The restoration project behind the borough building will help show property owners along the river how well the technique works, she said.
“In the next few years, we’re going to be developing that path and we’re obviously going to have to do some riverbank restoration,” Jones said. “This was an opportunity to give a demonstration and educate local landowners about what they can do. Maybe instead of putting a lawn next to the river they will do this as well.”
Anna Plager, chair of the joint city/borough Chena Riverfront Commission, said she hopes the project behind the borough building is “the first of hopefully what will be a long line of riverbank improvement projects that have long been needed in the downtown area.”
“I’m kind of hoping this matching grant funding makes it more financially feasible for property owners to do something like this,” she said.
While the south bank of the Chena River through downtown is nicely vegetated, that’s not the case on the north bank of the river, Plager said.
“If you look along north bank, which is what visitors walking on the south bank see and the sun hits most, it’s all been denuded,” she said. “We’re hoping property owners will emulate this kind of protection for their property.”
Festival Fairbanks got the idea for the project as a result of the first annual Chena River Summit hosted by the Tanana Valley Watershed Association in May, Jones said.
That TVWA has been a proponent of environmentally friendly riverbank stabilization projects for years and helped facilitate the recent project by coordinating communication between the borough and U.S. Fish and Wildlife Service, executive director Jewelz Nutter said.
“It’s great to see all this synergy is coming together,” she said. “To me, sticking trees in the ground so trees grow and the riverbank remains intact is sort of a no-brainer. It’s a win-win.”
Great Northwest harvested the root wads from its own property, Schlosser said.
Contact staff writer Tim Mowry at 459-7587. Follow him on Twitter: @FDNMoutdoors.