Safeguarding Nye

NYE - An eroding bend in the West Fork of the Stillwater River poses a threat to the downstream community around Nye if continued erosion diverts the river into a former channel that hasn’t flowed in more than a century, a watershed expert warns.
“The West Fork River could recapture its old channel,” Warren Kellogg, of Clancy-based Stream and Watershed Consulting, states in his 2014 Upper Stillwater River Assessment.
Kellogg, who was hired by the Stillwater Valley Watershed Council to conduct the river corridor assessment, warned about the threat to human safety, homes, roads, irrigation structures, drinking water, other infrastructure, and fish and aquatic habitat.
The problem site is about two miles up Limestone Road from Stillwater River Road, where the West Fork naturally divides into two channels. The right-hand channel carries much less streamflow and is partially blocked off from the main channel by a natural log jam that mostly occurred during the June 2011 flood, according to Noel Keogh, whose ranch land encompasses the site.
Several hundred feet downstream from the log jam is an eroding bend in the secondary channel, and several hundred feet away, across a boulder-strewn patch of flat riparian land, is the head of the old river channel.
Water flowing from Horseman Creek weakens the stream bank at the bend, making it easier for the bank to erode. The concern is that continued erosion and big flows during a flood event could cause the West Fork to return to its old channel.
Geological evidence indicates that creeks and rivers have moved all around the Nye Valley, but Kellogg notes in his assessment that Government Land Office maps from 1903 show the West Fork flowing in its current location.
“Much of the West Fork is self-armored with lots of rock,” Keogh explained during a Feb. 12 tour, “but around the Stillwater, the river has moved a lot over the years through natural movement.”
The old river channel tracks in a southeastern direction about three miles to the Stillwater River. Less than a mile up the Limestone Road is a headgate in the West Fork that diverts water into a portion of the old river channel for irrigating the Ekwortzel Ranch.
The old river channel crosses beneath two state roads – the Stillwater River Road not far from South West Fork Road, and the Nye Road at mile marker 20, several hundred feet west of the Nye Trading Post. In both places, small culverts beneath the roads handle irrigation runoff and ephemeral spring water.
After passing under the Nye Road, the old river channel tracks through cottonwoods to a floodplain along the Stillwater River where more than a dozen houses and trailers are located – mostly summer homes on small lots hooked up to wells and septic systems on rocky ground.
While Kellogg stated in his assessment that “it is not likely that the river will revert to its old channel,” he ranked the potential avulsion up Limestone Road as “high” and he offered a number of recommendations that could be considered in a preliminary engineering report.
Kellogg recommended installing rock flow deflectors in the West Fork’s main channel to “encourage” streamflow away from the secondary channel, reshaping the bend in the secondary channel and armoring it with rip-rap, using a low berm to redirect Horseman Creek so it enters the secondary channel downstream from the bend, and constructing a 3-foot high by 80-foot long dike about 100 feet down-valley from Horseman Creek to prevent out-of-bank flows from reaching the old river channel.
The watershed council joined the Stillwater Conservation District in securing $11,550 in grants to help pay for a preliminary engineering report to come up with mitigation proposals for the potential West Fork avulsion. The Stillwater Mining Co. provided $2,500 toward the project. Pioneer Technical Services will begin work on the report as soon as weather allows.
Local landowners also worked with the Stillwater Valley Watershed Council and Stillwater Conservation District boards to rank other projects prioritized in Kellogg’s 2014 report. After water users of the Yanzick and the Brey-Riddle irrigation ditches expressed interest in sponsoring a project for their diversion structures, the two boards agreed to support the project.
The goal is to improve water-use efficiency at the headgates and to eliminate annual disturbances in the Stillwater River.
The two boards recently received a $10,000 state grant to pay for a preliminary engineering report which will recommend an alternative that will improve river stability, aquatic habitat and public safety. The report from Pioneer Technical Services is expected to be completed this spring.