Beaver dams destroying trails at Dredge Lake

Forest Service plans to kill some animals to solve the problem

Posted: Monday, November 05, 2007

If you've ever hiked in the Dredge Lake area of the Mendenhall Valley, you know tennis shoes are of little help.

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But this year the system of trails is even more water-logged than usual, thanks to the rain and the handiwork of beavers.

"Normally they were in some areas and not in others," said Marc Scholten, a longtime forester with the U.S. Forest Service. "Now it seems like they're just about everywhere."

The beavers are damming the Dredge Lake area like they rarely have before. Water levels have risen and floods are washing away material from the area's trails and roads.

That's bad news for recreationists, dog-walkers, birders and cross-country skiers who love the system of trails that cuts between creeks, lakes and the Mendenhall River in between Back Loop Road and the Mendenhall Glacier.


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"It's just out of hand," Scholten said. "We're losing a lot of improvements that we've made to the area. I don't want to see these trails get washed away."

"We do what we can, but we don't have the funds to dedicate to going out there every day," said Pete Schneider, fisheries biologist with the U.S. Forest Service. "It would take 10 man hours every day this time of year to maintain the lake level as good as you could do it. And there's no guarantee that we're going to get the lake levels down to a point where you can walk in tennis shoes."

In past years, the Forest Service has attempted to live-trap and relocate the rodents. That's proven to be an inefficient process.

This winter, plans call for lethal traps. A trapper will come in sometime after Dec. 1, when legal-trapping season begins.

"We'll wait until it freezes up," said Dennis Chester, wildlife biologist with the Forest Service. "We want to make it as safe as possible for anybody else."

"The best time to trap is in the wintertime, when they can set them underneath the ice and they don't have incidental catches of dog and pets," Scholten said.

To trap, the Forest Service will need to apply for a permit from the Alaska Department of Fish and Game.

The service hired a trapper last winter. But due in part to the heavy snows, no beavers were trapped, Chester said.

Most of the trapping will be done in the southern end of the Dredge Lakes area. That's where flooding has done the most damage to trails and fish habitat improvement projects.

Beaver trapping is a contentious issue. Many argue that the creatures have just as much right as humans to use the Dredge Lake area.

"To me, it's a very sad situation," said Juneau naturalist and photographer Bob Armstrong.

"I'm on the beaver's side," he said. "They create wonderful habitat for wildlife. Much of what we enjoy out in the (Mendenhall) Valley is because of the beavers. They create nesting area for waterfowl, feeding areas for kingfishers and herons, breeding areas for dragonflies and rearing area for coho salmon. I think they're very beneficial."

But what can be done about the small army of beavers and the havoc that their lifestyle creates?

The Dredge Lake area offers a good habitat for the beavers. It's fairly flat, there's plenty of water, and alders, willows and cottonwoods - which beavers like - have taken hold where the glacier has receded.

"In another 30 to 40 years, the spruce and hemlocks will take over for the deciduous trees, and you're not going to have as many beavers," Schneider said.

Where there's running water, the beavers will usually try to dam it. The rodents start building their dams in the summertime to raise pond levels and build more swimming habitat. Once the water is to their liking, they'll prepare their winter lodge or work to cache food for the winter supply.

"The beavers are very active this time of the year," Schneider said. "They have to make sure all their I's are dotted and all their T's are crossed before the winter sets in."

Five years ago, trail repair crews trucked in material to the Dredge Lake area to try to raise the level of the roads. The hope was that the trails would be in better shape for cross-country skiing, open earlier in the fall and last longer in the spring. But as the dams have risen and lake levels have flooded, more fill and sediment has washed away.

The west end of Dredge Lake has overflowed. The beavers have built a new lodge on the west side Moraine Lake. The south end of Moraine Lake is dammed. A holding pond and the small outlet pond from Moose Lake are clogged. The beavers have even obstructed a small road culvert near the National Weather Service office on Back Loop Road.

"And that hasn't been dammed in many, many years," Scholten said. "I busted up that dam about two weeks ago, and it was built up the next day."

"These beavers will beat you to the ground, and they won't feel bad about beating you," Schneider said. "They're way more motivated than anybody else to keep that lake level as high as possible."

During the weekend of Oct. 19-20, a team of 12 volunteers organized to clear out the six-foot-tall man-made culverts that pass under Glacier Spur Road as it heads north toward the Mendenhall Glacier Visitor Center.

The debris was preventing fish from reaching their natural spawning ground at Upper Steep Creek.

The beavers had done such a good job on the culverts that it took the team almost two hours - in chest waders - just to get down to the top of the structures.

After a couple of days, the team had cleared enough brush so that the fish could move upstream.

"We had both coho and Dolly Varden moving upstream right through out legs as we were working," Armstrong said. "That was really a good feeling. They were anxious to get up there."

It took five days and several pickup truck loads of brush to completely clear the culverts. But the beavers did not give up.

On the first night the culvert was cleared, the critters immediately plugged it again. It took a volunteer 2 ½ hours the next day to re-clear it.

Again, the beavers struck overnight. This time, the volunteer needed 1 ½ hours.

For two more nights, the beavers returned. The volunteer spent 30 minutes and 15 minutes respectively, pulling the brush away.

"By the fifth night, they were no longer putting sticks in at night," Armstrong said. "When we had this fairly recent rain, it brought in numerous coho. And the bears are up there, the magpies, the bald eagles. It's really a joy to see it back to so-called normal."

"It was much appreciated," said Ron Marvin, director of the Mendenhall Glacier Visitor Center. "We like the idea that people can come up and see the creek in rearing season. If we get more fish up Steep Creek, we get more opportunities and food for the bears."

• Korry Keeker can be reached at 523-2268 or

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