A century behind a wall made Missoula's main waterway a fairly predictable neighbor. It rose and fell like the Bitterroot and Blackfoot rivers, but Milltown Dam leashed much of the Clark Fork's ability to reshape its banks. So features stayed the same for miles above and below that barrier.
Look at the whopping sandbars at the Sha-Ron fishing access east of Missoula or the waterlogged campfire rings on Kelly Island west of town. They're hard to see right now, as spring runoff sends the Clark Fork to the top of its banks, but be ready for some redecorating along the river's living room come June.
On a tour of Kelly Island last week, Brick and U.S. Army Corps of Engineers research ecologist Jock Conyngham wandered through cottonwoods that probably sprouted around the time Milltown Dam was finished in 1908. The barrier allowed fine silt to pass through Missoula, which helped the trees. But it starved the river of larger “spawning gravel” that fish need.
Kneeling along a new sandbar, Conyngham pulled up a handful of rocks ranging from BB- to thumbnail-size.
“It's coarser gravel that the eggs are both protected by and can mature in,” Conyngham said. “It's got to be clean enough that fry can swim up through it.”
Dozens of old cottonwoods were newly knocked down along the Kelly Island banks. Conyngham sank to the top of his chest waders along one side of a big trunk, but found the channel just over knee-high on the other side.
“As bars form on the inside of a bend and put pressure on the outside of a bend, you're going to get some really deep slots,” he said. “These areas where woody debris goes in, because of recent bank erosion - they hold a lot of fish.”
See a video demonstration of some of the changes occurring at Kelly IslandElsewhere along the Clark Fork, river users are bracing for change. One person watching closely is Missoula Fire Department battalion chief Todd Scott, who leads the department's water rescue crews.
“The river's definitely a different animal since the dam came down,” Scott said. “We had maps for our jet boat, showing where the safest channels were to run the river. They've definitely changed. Now we're finding sediment and riffles where there used to be nice deep channels.”
That jet boat lives in a shed in McCormick Park, with a concrete ramp leading to the river. Scott said last summer, he noticed the end of the ramp was growing a new sand bar that made it tough to get the boat in and out of the water. If that continues, the ramp may need to be redesigned.
The sediment is not the toxic heavy-metal deposits that prompted removal of Milltown Dam in the first place. This year, much of it comes from a huge deposit the Blackfoot River dropped last year just below the damsite.
It could be seen, briefly last year, when Envirocon excavators shifted the Clark Fork out of the dam spillway and into a new channel where the powerhouse used to be. During the 2008 spring runoff, an eddy spooled below the now-dry spillway and deposited a football field full of sand and gravel, mostly from the now dam-free Blackfoot River.
After removing the old spillway, excavators cut the coffer dam and returned the Clark Fork to its original channel on March 27. Because the Missoula city reach of the river is heavily armored, most of the sediment will race right through town and start settling out around Kelly Island.
Montana Fish, Wildlife and Parks fisheries biologist Pat Saffel said that deposit depended on the combination of a high runoff spring in 2008 combined with the 14-foot drawdown brought about by the dam's removal. It's not likely to happen in that magnitude again, barring a 100-year flood.
But the Clark Fork will be regularly moving everything from pea gravel to alder trees through town, like the Bitterroot and Blackfoot have done along their banks for the past century. That could bring changes to FWP boating sites at Kelly Island, Kona Bridge and other Clark Fork recreation areas.
“That's kind of a wild card for us,” Saffel said. “We're not really certain how those sites will be affected.”
Spring runoff should keep the river enigmatic for another several weeks. When the waters clear, prepare to rethink old ways.
“When we talk about what people expect to see when they go to their favorite area, like Kelly Island, is that these are processes that occur regularly,” Brick said. “Sometimes they don't occur on a human scale. Some things that might take place over 100 years, dam removal does that in a different way. What we can expect to see most is change.”
Reporter Rob Chaney can be reached at 523-5382 or at rchaney@missoulian.com.
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OverStated wrote on Apr 27, 2009 12:00 PM:
I for one doubt very much that we will see the fishing improve very much over what it was before they started mucking with the river, to date all that they have succeeded in doing is crash the trout population and give us lots of promises.
Son't get me wrong, I would completely oppose the daming of any river. But I'm not so sure the Milltown dam was the big meanie everyone claimed it to be. And I think those good affects that removing it would bring are WAY overstated, once again for the reasons of justifying certain peoples jobs and getting those millions of dollars flowing to the right pockets. In short, they've completely oversold expectations to the public.
The real benefit of removing the dam will be in large degree a lot greater to the bank accounts of certain people than to the benefit of the river itself. "