Group tries to prep Basalt for 100-year flood |

Group tries to prep Basalt for 100-year flood

Brent Gardner-Smith

A group of citizens, professional planners and engineers has begun developing a new master plan to manage the Roaring Fork River through Basalt in the event of a 100-year flood.

Operating under the premise that the river will once again overflow its banks and threaten property, primarily on the river’s south side, the group is putting together a list of changes to better deal with nature’s sometimes unruly course.

“The goal is to allow the 100-year flood to make its way through town without causing any safety problems or property damage,” said Mark Fuller, a consultant who is serving as the facilitator for the River Stewardship Roundtable. The group includes about 20 citizens and an equal number of technical consultants. “There are some goals that go along with that, such as maintaining the riparian environment, maintaining public access to the river for recreational purposes, and to do all this using natural systems instead of too much engineering.”

The group’s goal is to come up with a list of recommendations in a master plan format, have the Basalt Town Council adopt the plan, and then budget the funds to implement the recommended actions.

The focus is on the stretch of river from the upper Basalt Bypass bridge on Highway 82 to Hook’s Bridge, which is behind and below the Mid-Valley Design Center. The town budgeted $35,000 in 2000 for the roundtable, and that includes an evaluation of the river by McLaughlin Water engineers. For 2001, the town has budgeted $70,000 for the project.

Wednesday night in Basalt, the group got together for its second meeting and heard tales of both the 1957 flood and the 1983 flood. The river also flooded in 1918, 1921 and 1995.

Longtime Basalt resident Billy Grange said the waters in ’57 flooded the low-lying land near the river. At the time it was mostly farmland, but one resident was prepared to torch his farmhouse instead of seeing it swept away to become an instant dam. Today, the area is built out and includes the Basalt Store, the Roaring Fork Mobile Home park, and the homes and businesses in the area now known as Southside.

In 1983, Pitkin County engineer Bud Eylar remembered, Don Davis, then the county’s emergency manager, was prepared to pull down a two-story building just upriver from the 7-11 store, as the river had risen to the point where it was undercutting the bank beneath the building.

“Davis had asked me what I thought was going to happen,” Eylar said. “I told him I thought the building was going to fall into the river, was going to get hung up on the bridge and then act like a dam. Then the river is going to wash out the road and then run through the trailer park.”

At that point, Davis was prepared to take down the building. A cable was strung around it and attached to a bulldozer. But in the end, just before the pulling began, the river backed off, and the building still stands on the riverbank today.

It is those types of scenarios that Basalt hopes to avoid in future high-runoff years.

And one of the reasons it has put together such a large and diverse group of citizens to consider the issues is that tradeoffs may have to be made.

For example, the bridge across the river between the Basalt Store and the 7-11, known as the Emma Bridge, used to be the main auto bridge across the river. Today, it serves as a pedestrian bridge and is a pleasant spot to watch the river flow.

However, it’s also a major pinch point for the river, and it may make sense to take the bridge out. On the other hand, the bridge also gives protection to the mobile home park just downstream.

“The citizens are there to help prioritize the various tradeoffs that are going to have to be made in dealing with the river,” Fuller said. “We may get to the point where some values that we associate with the river, like easy access, may need to be sacrificed to some degree for safety reasons.”

The upper Basalt Bypass bridge is also causing problems. Engineers from the Colorado Department of Transportation originally thought the bridge’s abutments would cause the river to scour a deeper channel under the bridge. Instead, what they’ve found is that riverbed material is piling up under the bridge on one side, and rushing water is scouring the riverbank on the other.

“They were trying to engineer nature, and nature didn’t cooperate,” said Fuller.

The meeting also included a primer on how Basalt’s topography and geology interact with the river in the area. The Roaring Fork River runs down a steep, incised channel for most of its course from Aspen to the Wingo Junction bridge. Then, it enters a broad flat area and meanders a bit.

“The river wants to spread out through the area when it rises instead of cutting a deeper canyon,” said Fuller. “It wants to move laterally back and forth across the landscape, and when you encroach upon the river with development and confine the river with things like road-building, you make flood events more harmful.”

In addition to the river’s changing course, it is moving through an area that is filled with round river rock, piled up through the eons and now 30 feet deep.

“We’re sitting on some of the most unstable alluvial soils that the state rates,” said Sloan Shoemaker, a Basalt resident serving on the roundtable. “We’ve built a community under the assumption that we are on stable soil next to a stable river, but we’re on unstable soil next to an unstable river.”

The roundtable hopes to present the river master plan to the Basalt trustees by June or July 2001.

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