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Findings Shed Light on Murky Waters

Coldstream's watershed is the culprit of high sediment levels in the Truckee River
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Coldstream Watershed Study Complete
On January 16 Matt Kiesse of River Run Consulting presented the findings of a study of the Coldstream Canyon watershed. In the audience were Truckee Town Planning Commission members, Teichert employees, Coldstream property owners, and a handful of residents who enjoy recreating in the watershed that is a primary contributor of sediment to the Truckee River. The Truckee River is currently listed as impaired by sediment on the State Water Resources Control Board (SWRCB) 303(d) list of waters that do not meet the standards of the 1972 Clean Water Act.

'Available data suggest that Cold Creek is probably the single largest contributor of sediment to the Truckee River,' Kiesse said. The data also indicate that in relation to the size of its watershed, Cold Creek is one of three Truckee River tributaries most laden with sediment, exceeded only by Squaw and Gray Creeks.

The study began in Spring 2006. It was coordinated by the Truckee River Watershed Council and funded through an SWRCB Pollution Reduction Grant. The Department of Parks and Recreation worked in partnership with the Watershed Council. Cynthia Walck, geomorphologist for California Parks and Recreation, described the study as an attempt to understand the erosion and habitat issues of the watershed, and to determine why the amounts of sediment stored and transported by the watershed have fallen so far out of balance.

Human Impacts
The volcanic soils that compose much of the Coldstream watershed erode easily, and produce some of the sediment that eventually enters the Truckee. However, 'Coldstream has experienced enormous human impact,' Kiesse said. 'A significant portion of the sediment is from human disturbance.' Of this human-triggered sediment, slightly less than half washes off of roads in the canyon. The remaining portion erodes from regions of the streambed disturbed by human activities.

In storm events 'the roads become rivers,' Kiesse said. The exposed surfaces of the roads disintegrate relatively easily when water flows over them.

Human activities have destabilized two regions of the streambed. The uppermost region lies downstream of a railroad culvert, below the upper reaches of the canyon. In 1867, Central Pacific Railroad workers constructed the culvert over the top portion of an alluvial fan. The fan was created as runoff waters laden with rocks, sand, and boulders from the steep, unstable slopes below the Sierra Crest deposited their contents on the low-angle terrain in the floor of the canyon. The culvert interrupted that process. As Walck described it, 'The sediment rich water from the upper forks of Cold Creek used to wander across the alluvial fan, now all of that water is confined to one little spot, the culvert. Its sediment deposition function is disrupted.'

The streambed immediately below the culvert has been transformed into what Kiesse termed a 'supernaturally straight' channel. It is a segment of Cold Creek that flows between ten- to twelve-foot banks and over a streambed composed of 'very tightly packed and welded' sediments. Material that would formerly have been stored in the alluvial fan enters the culvert, sweeps through this 'perfect transporting monster,' and flows downstream into an area that has become highly unstable as a result of the added influx of sediment. This destabilized portion of Cold Creek shifted 50-feet in the floods of 1997, destroying a road and carrying away many tons of sediment.

The length of Cold Creek that flows from the outlet of Coldstream Canyon to Donner Creek has also been destabilized by human actions. Like the region near the culvert, this lower plain is an alluvial fan. Over tens of thousands of years Cold Creek deposited sediment on this low-angle terrain, and for forty years of the last century people mined the abundance that deposition created. Teichert Materials was the last company to do so. Teichert began harvesting gravel under lease in 1966, and purchased the land in 1983.

During the period of mining Cold Creek was routed into a channel. The channel is sufficient to contain virtually any flood; however, over the years the banks of the channel have eroded and widened considerably. As with the section of stream near the railroad culvert, this lower stretch of Cold Creek once stored sediment but now produces and transports it. The sediment that flows out of the channel threatens to destabilize portions of Cold Creek and Donner Creek as it flows toward the Truckee.

Possibilities for Restoration
The Draft Report written by River Run Consulting and Hydro Science acknowledges that the complicated pattern of land ownership in the Coldstream Canyon will make it difficult to mitigate road erosion, but suggests performing regular maintenance on water bars and other erosion control measures, upgrading or re-routing roads particularly prone to erosion, and removing roads that experience little traffic.

In the area destabilized by the railroad culvert 'a head-on restoration approach may not be feasible,' Kiesse said. An effective modification of the culvert would be prohibitively expensive and would not benefit the most volatile region of the Creek. Instead, Kiesse recommends fortifying the destabilized area with woody debris. This approach would ideally augment the Creek’s ability to store sediment while simultaneously dampening the erosive force of future flooding events.

In the lower channelized section it is more likely that the original character of Cold Creek may be restored. Before human disturbance the Creek wandered over an inset floodplain – a swath of riparian terrain set below the surrounding landscape. By widening the channel this floodplain may be restored. The report states that through this approach, 'the amount of fine sediment introduced to the creek during streambank erosion can be significantly reduced, and the process of riparian vegetation and floodplain development can be significantly accelerated.'

Parks and Recreation favors this approach. Walck suggested that a restored inset floodplain would provide a scenic and naturally attractive area, as well as 'a nice habitat corridor.' Habitat corridors extend and connect animal territory. They are especially important in areas of human development.

Unruly Watershed Meets Planned Community One
Teichert Land Company has submitted an initial draft of Planned Community One, a 180-acre, mixed commercial and residential development that will occupy the former Teichert mining land. Project Manager Mike Isle emphasized that Teichert has been in contact with River Run Consulting and TWRC, but said, 'we’re not sure what will make the most sense yet.'

According to Dale Creighton of SCO Planning and Engineering, the developer’s response to the watershed study will depend largely on what action Parks and Recreation chooses to take. Parks and Recreation owns a portion of the channelized section of Cold Creek just upstream of the development site. 'Right now we’re meeting with Parks and Rec.,' Creighton said, 'trying to figure out if this will be a joint project or two simultaneous projects.' Creighton did not think the existing plans would have to be altered to accommodate a restored floodplain, explaining, 'the plans were developed while the study was in progress, and we were able to take many of the findings into account.'

Cynthia Walck and Beth Christman of TWRC commended Teichert for its response to the watershed assessment. 'Teichert attended the two stakeholder meetings and the public meeting, and has independently contacted River Run Consulting,' Christman said.

The next opportunity for public comment will occur when Teichert submits the next draft of its plans. According to Isle, Teichert intends to do so in March.

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November 8, 2018