Massive spruce blocks river in Aspen’s North Star Nature Preserve | AspenTimes.com

Massive spruce blocks river in Aspen’s North Star Nature Preserve

Note to anyone who likes to float the North Star Nature Preserve east of Aspen: Brace yourselves.

"At this point, I would say Mother Nature has closed the river," said John Armstrong, Pitkin County Open Space and Trails senior ranger. "My thinking is the Great Spirit has spoken."

The snowstorm that blew through the Roaring Fork Valley on Nov. 17 may not have delivered much snow but it did bring intense wind, Armstrong said. That wind snapped the trunk of an approximately 80-foot-tall spruce tree, which had been leaning out over the river. The tree fell across the Roaring Fork River about 200 yards upstream from the Southgate entrance to the North Star Nature Preserve.

"It could be a new bridge," Armstrong said Friday after climbing on to the massive tree that completely blocks passage down river.

“At this point I would say Mother Nature has closed the river,” said John Armstrong, Pitkin County Open Space and Trails senior ranger. “My thinking is the Great Spirit has spoken.”

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The tree's trunk is about 2½ feet around, while the bottom branches stick up about 18 to 20 feet high. It stretches across the river and up on to the opposite bank. The tree is probably at least 100 years old if not closer to 150 years old, Armstrong said.

The 175-acre North Star Nature Preserve is located about 1½ miles east of Aspen and features the only calm stretch of water on the Roaring Fork River. Because of that, the placid float has become such a popular summer activity for locals and tourists alike that the county has had to begin aggressively policing river behavior, especially in the past year.

And while the large spruce won't become an issue until those boaters return in late spring and summer, if it remains in place it almost certainly will become an issue then, Armstrong said.

"With this popular stretch of river, I would definitely say there will be local interest in removal of the tree," he said. "I think there will be a lot of interest in reopening the river."

But taking out the tree will be dangerous and expensive, Armstrong said, estimating the cost at "thousands of dollars." Open space officials are consulting with a local tree service to figure out their options, he said. The tree could be partially or totally removed, or it could be "hinged" so spring floods push it to the side bank, he said.

Gary Tennenbaum, executive director of the county's Open Space and Trails Program, will make the final decision on whether the tree will be removed, Armstrong said. An attempt to reach Tennenbaum on Friday — when county offices were closed — was not successful.

The spruce marks the third large tree in the North Star Preserve blown down by wind in the past year, Armstrong said. The other two fell within a month of each other in the fall of 2015, but they fell on a boardwalk area and not on the river, he said.

As if the spruce wasn't bad enough news for boaters, a beaver has been busy building a dam about 200 yards downstream from the treefall. Armstrong said he first noticed the dam — which is located close to the Southgate access point to the preserve — about six weeks ago.

As of Friday, the dam structure — made of mud and mainly willows woven together — stretched three-quarters of the way across the river. Much of it was below the surface, Armstrong said. Many nearby willows on the riverbank showed signs being sheared off by beavers.

"I've never seen a beaver dam on North Star," Armstrong said. "This is a pretty good size stream to dam up. Usually they like to build them on creeks."

Just upriver from the dam on the opposite side of the river is a cluster of willows in the water that Armstrong also said was the work of the beaver or beavers.

"I'm not sure how many are working on it," he said.

However, damming the entire river will be difficult for the beaver or beavers because of the quantity of water now being forced through the remaining open portion, the depth of the river at that point and the swift current, Armstrong said.

"It will be a lot harder for him to sustain a dam there," Armstrong said. "He's at the most challenging point of his engineering project."

If the beaver is successful in damming the river, Armstrong said he plans to leave the dam alone. Boaters could likely pass over the top of it, he said.

jauslander@aspentimes.com