Study Assesses Feasibility, Recommends Alternatives
On March 6, 2006, River Run Consulting of Truckee led a team of consultants in a study that resulted in a 112-page report on the feasibility of restoring the Upper Truckee River.
The Upper Truckee River has been negatively impacted by land use practices since Europeans settled the Lake Tahoe Basin. Comstock Era timber harvest increased erosion and flooding, and the transport of logs on the river caused direct impacts on the channel.
Farming and ranching practices altered the channel and surrounding floodplain. In many locations, particularly in the lower portion of the river downstream of Meyers, the channel was straightened and enlarged to protect or improve farming operations. Much of the former marsh and delta at the mouth of the river was lost to accommodate residential development.
The river was channelized and adjacent floodplain occupied in the construction of an airport. Adjacent floodplain was highly altered in the development of a golf course in the project reach. Downstream of Meyers, the river ecosystem of at least half of the length of the Upper Truckee River has been highly modified, resulting in the loss of habitat and water quality protection. These historic and ongoing modifications have negatively impacted the ecologic and geomorphic function of the Upper Truckee River.
The California Department of Parks and Recreation (CDPR) owns the reach upstream of Elks Club near Sawmill road to just downstream of the highway 50 crossing at Meyers. The CDPR property includes a Washoe Meadows State Park and Lake Valley State Recreation Area which includes the Lake Tahoe Golf Course.
The golf course reach was identified as the greatest opportunity for rehabilitation in the “Upper Truckee River Upper Reach Environmental Assessment report” by Swanson Hydrology and Geomorphology (SH&G). SH&G recommended 4 possible options, ranging from (1) no action, (2) hard engineering (riprap), (3) creation of inset flood plain, to (4) restoration. This document reviews and summarizes a conceptual stream and ecosystem restoration project within CDPR property. Although several other restoration projects are currently being planned for the lower UTR, many significant constraints to full geomorphic or ecosystem restoration exist.
The Washoe Meadows project represents a unique opportunity for restoration of the lower UTR because there are few constraints on project planning and implementation due to public ownership by CDPR (such as concerns about flooding on infrastructure or other potential restoration impacts).
Within the project area, the UTR has been channelized, resulting in a straighter and deeper channel. The stream responded to human disturbance by incising relative to the floodplain, which is now flooded less frequently. The stream has continued to adjust to past disturbance, resulting in high rates of instability. Construction of the golf course, much of which is in the former floodplain, has resulted in the loss of native riparian vegetation, including wet and mesic meadows and willow shrub-scrub.
Because the golf course was constructed after major channel modifications in the project area, and significantly constrains the channel with bridges and fairways and greens on streambanks, it has also essentially locked the river into a modified alignment. Channel instability continues as the stream adjusts to past channel modifications, and maintenance of golf course infrastructure has become a continual problem, requiring extensive bank stabilization measures.
Human disturbance of the UTR within the project area, and resulting channel instability, have had a number of negative consequences for the stream ecosystem. Instream habitat is of poor quality, and former spawning habitat for salmonids has been lost.
Riparian shrubs and meadows have been converted to golf course. The beneficial effect of disturbance caused by regular flooding on riparian habitats has been lost. Ongoing erosion threatens water quality in the stream and in Lake Tahoe, and the loss of overbank flooding no longer allows for the improvement of water quality by settling sediment on adjacent floodplain, or the uptake of nutrients by floodplain vegetation.
The primary objectives of the proposed project are to restore riparian ecosystem processes and function, and to restore stream geomorphic function. CDPR's goals for the project include:
• restore, to the extent possible, ecosystem function to the CDPR reach of the Upper Truckee River through restoration of natural geomorphic processes which sustain channel and floodplain morphology, and in turn promote the establishment of functional riparian vegetation communities, ecological processes and aquatic habitat;
• reduce erosion and improve water quality;
• reduce the impact of the golf course on the river, water quality, and riparian habitat;
• maintain recreation opportunities, including relocation and reconstruction of part of the golf course on higher capability lands in accordance with the highest environmental standards; and
• minimize risk in relation to expected benefits
Meeting these goals will require recognition that functional streams are dynamic over time. Available evidence indicates that, prior to human disturbance, the UTR channel was dynamic, both through slow migration of meander bends and through more rapid channel migration during larger floods. Riparian and aquatic ecosystems have evolved in response to the dynamism inherent in functional stream channels; many aspects of ecosystem function are dependent on the disturbance resulting from channel dynamics. Thus the restoration plan must allow for channel dynamics and channel change over time.
The proposed restoration plan has two basic components; passive restoration and active restoration. Passive restoration, or the removal of impacts to ecosystem and geomorphic function, is the essential first step in restoration planning. Thus, the first and most important restoration action is to remove golf course infrastructure from the historic floodplain area. This step requires removing greens, fairways, tees, bridges, irrigation system in former floodplain areas and potentially relocating them in nearby uplands, areas more suitable to this land use.
Passive restoration is important to ecosystem restoration in the project area because it will allow for functional channel configuration and channel dynamics over time.
The second component of this plan is active restoration, the objective of which is to restore channel and floodplain processes and vegetation communities. The active restoration plan outlined in this document is designed to meet multiple objectives: restoration of geomorphic function; aquatic and riparian habitat restoration; water quality improvements; and reduction of maintenance of golf course facilities.
Because regular disturbance by flooding, including some erosion, is critical to sustaining function in riparian plant communities, this plan seeks to restore natural rates of erosion and deposition rather than to completely stabilize all streambanks.
The active restoration plan calls for restoring length to the channel, and raising the channel bed. The new channel would incorporate segments of the existing channel with reactivation of abandoned meanders coupled with reconstruction of some obliterated meanders.
Abandoned meanders that were active in the 1940's and 1950's, features that still exist, would be incorporated into the channel design. This would improve constructability of the restoration project as these meanders are currently well-vegetated. Over 50% of the existing channel would be retained, improving stability and construction feasibility. Grade control, and increases in channel elevation, would be accomplished through the use of coarse riffles at regular intervals within the channel. This restoration technique has been used in other Tahoe Basin projects with success. More highly engineered grade controls would be constructed at the upstream and downstream ends of the project area to assure stability and transition to downstream elevations. Finally, revegetation treatments would be applied to the former golf course to restore native vegetation communities.
This restoration plan would provide several important benefits. Merely removing the golf course from the floodplain would eliminate the need to manage the river to assure the stability of golf course infrastructure, including some under-sized bridges. Rip-rap and other measures that degrade stream function would no longer be required. Removal of the golf course would also allow for natural channel dynamics, an important requirement for the establishment of functional riparian vegetation communities.
Important water quality benefits would be realized as well, by moving fertilization and irrigation out of the floodplain. And moving the golf course away from the river paves the way for active restoration measures, such as the reestablishment of riparian meadow and shrub vegetation communities.
Active river restoration, lengthening and raising the channel, would increase the amount and improve the quality of instream habitat. The river would flood the adjacent floodplain more frequently, providing the regular disturbance necessary to restore functional riparian vegetation communities.
Streambank height and channel slope would be reduced, resulting in more stable banks and less erosion. More regular overbank flow would improve water quality, with fine sediment deposited on the floodplain during floods. Higher groundwater tables would enhance adjacent riparian vegetation communities and would provide water quality benefits by allowing for more effective nutrient uptake by plants. Over 45 acres of vegetation currently in golf course management would be converted to native vegetation types. Most of this converted vegetation would be riparian communities, such as wet and mesic meadows and riparian shrub.
The ecosystem consequences of moving the golf course to adjacent upland were also analyzed within this study. Potential ecological impacts and mitigation measures were summarized. No major ecological obstacles to golf course relocation were identified. Ecological benefits over the current configuration include:
• Better water quality protection through the construction of state-of-the-art water quality protection measures, such as computerized irrigation, effective sub-drains, and wetland treatments.
• Removal of golf course habitat impacts from relatively rare vegetation communities that have been significantly disturbed by human development (riparian meadows and shrub-scrublands) to a vegetation community type far more widely distributed and less disturbed in the basin (pine forests).
Finally, the feasibility of implementing the project was analyzed. The recommended construction techniques have been implemented in other Tahoe Basin projects and are feasible. Measures for protecting water quality in construction practices are outlined, including construction phasing, isolation of newly restored areas to allow for vegetation establishment, and use of clean substrates. Similar measures have been successfully implemented on other Tahoe Basin restoration projects. This analysis concludes that the project can be feasibly constructed while protecting water quality.
In summary, the restoration project for the UTR within Washoe Meadows State Park would provide important ecosystem restoration benefits, resulting in better riparian and aquatic habitat and improvements in water quality. This restoration project represents a unique opportunity to restore riparian ecosystems and geomorphic function to a reach of the UTR, the largest tributary to Lake Tahoe.
Download the complete Riparian Ecosystem Restoration Feasibility Study
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