Download the complete
Riparian Ecosystem Restoration
Feasibility Study
Return
to main library page
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.
Executive
Summary
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
Return
to main library page
