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The Merced River
Corridor Restoration Plan - Phase IV Project (CALFED
ERP-02-P12-D) evaluated strategies for channel and floodplain
restoration in the Dredger Tailings Reach (DTR) of the Merced
River (RM 45-52) within the context of the contemporary flow
regime. The overarching goal of the project was to bolster
ecologic integrity at the Merced River Ranch (MRR) through
restoring fundamental geomorphic and floodplain processes, the
latter achieved by scaling channel and floodplains to the
regulated flow regime of the Merced River.
Stillwater Sciences, working with the California Department of
Fish and Game (CDFG) and various subcontractors (URS Corp., KSN
Inc., River Partners, Frontier Geosciences, Slotten and Ayers [UC
Davis], Point Reyes Bird Observatory, Geomatrix, Inc., and
McBain&Trush), developed restoration plans for the MRR (RM
50-51), a property purchased by CDFG in 1998 as a source of
coarse sediment for future river restoration projects and as a
floodplain restoration site. Historical gold dredger mining
operations in the reach, and alterations to the natural
hydrograph by upstream dams has resulted in the loss and
degradation of habitat for native species. The reach is the
primary spawning area in the Merced River for fall-run Chinook
salmon (Oncorhynchus tshawytscha), an important management
species for CDFG, and potentially steelhead (O. mykiss), which
is listed as threatened under the Federal Endangered Species
Act.
The removal of tailings from
the floodplain has the potential to yield multiple restoration
opportunities and ecosystem benefits, but the detailed impacts
of such restoration activities are largely unknown. As such, a
suite of studies were undertaken to support restoration planning
at this site, with a view towards providing transferable
scientific information to reduce uncertainty in future
restoration designs on the Merced River and potentially in other
rivers in the Central Valley.
To support the catchment context, baseline data was collected at
several spatial scales. At the MRR, studies have included
analysis of the volume and texture of dredger tailings, an
evaluation of the potential for methylmercury release from
tailings, and a native tree-growth experiment under controlled
conditions. Reach-scale investigations along the Dredger
Tailings Reach included baseline surveys of the abundance and
diversity of fish, birds, and invertebrates, and two years of
monitoring channel form and sediment transport dynamics.
Detailed cross-section and long profile surveys were used to
construct reach-scale hydraulic and sediment transport models to
interpret the prevailing flow regime.
Under of Phase IV of this project, restoration strategies were
developed for the MRR based on current understanding of
contemporary geomorphic and riparian vegetation design
principles with the aim of using the channel-floodplain portion
of the MRR as a pilot project for the similar areas in the DTR
or elsewhere in the Central Valley. Design drawings were
developed to the 75% completion stage, along with plans for
gravel infusion and augmentation, implementation, and
post-project monitoring and evaluation. Draft permit
applications and cost estimates will be prepared as a pre-cursor
towards implementation funding.
Two summary documents were produced: one detailing the
scientific insights offered by the project (currently under
review), and the other a
pamphlet for public distribution outlining the proposed
restoration.
Updated: 02/12/2007 |
