If the Star Valley Town Council wants to keep creeks from gobbling up homeowners’ property, they can simply remove debris clogging channels or install an expensive upstream flood control facility, an engineer explained at Tuesday night’s council meeting.
Currently, homeowners with damaged property are doing what they can to stop floodwaters from cutting across their land, explained Mountain Standard engineer Andy Romance.
With jerry-rigged dams, creeks like Houston, Goat Camp and Mayfield Canyon Wash migrate in new directions and often get pushed onto other property owners.
“Urbanization around these and the other identified drainage ways has both modified natural channels, as well as increased risk for loss of property and life due to flooding,” Mountain Standard’s initial storm water control evaluation recommendation report states.
“When channel maintenance and improvements are by default conducted by individual property owners, without helpful government oversight, sporadic and varied approaches can result.”
The Floodwater Task Force identified 15 areas of town most affected by flooding and several possible solutions. Romance analyzed the options and said all four would work to ebb flooding.
The first option is removal of channel vegetation, specifically willow brush. In Goat Camp Wash at Valley Road, where water has overtopped the banks by 1.4 feet, removing obstructing brush would contain floodwaters.
“In the major channels, we need to clear out brush because it has been a lot of years without maintenance and the willow brush is choking them,” Romance said.
However, simply removing brush will not fix the problem in other areas.
“We may need to widen channels or line them with concrete to ‘slicken’ them,” he said. “But we cannot just move channels out 10 feet because that means a lot to the homeowners.”
Instead of widening whole channels, Romance suggested extending the channel bottoms to convey 100-year floodwaters.
In Goat Camp Wash, the current dimensions convey 2,700 cubic feet a second, but the expected 100-year flow rate is 3,663 cubic feet a second. Lining the existing channel with gunite or concrete will increase the channels capacity sufficiently, he said. Alternatively, the channel bottom could be widened an additional 10 feet.
In areas where the bank is eroding, Romance suggested planting the same plant that is clogging the channels — willow.
“That same willow holds the soil together, so on the bottom remove it, but on the side maintain it.”
Much of Goat Camp Wash is eroding, he said. Lining the banks with a fabric mat that promotes vegetation growth would stabilize erosion.
The last option is creating upstream storm water detention basins.
Water would collect in the basin and slowly siphon down through the creeks.
The basins could be placed upstream of Houston Creek, Mayfield Canyon Wash or at the confluence of Mayfield Canyon Wash and Schoolhouse Canyon Wash.
The biggest consideration with basins is cost and getting agencies like FEMA to agree, he said.
Councilor George Binney said he was concerned with the cost of projects.
Romance suggested the easiest and cheapest project to start now would be brush removal.
“The local government of Star Valley (should) continue to advance a regional solution and relieve the case-by-case approach that individual property owners tend to conduct on their own,” he said.