GENERAL42732

• Permit No: M1976032
• IBM Index Class Name: General Documents
• Doc Date: 6/5/1996
• From: USFS
• Media Type: D
• Archive: No

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/ II. Proposed Action •
Significant adjustments to channel stability and function of the South Fork and
mainstem San Miguel Rivers have occurred, due primarily to gravel mining and
extraction of materials. Activities associated with the mining operation have
modified the floodplain and riparian vegetation, and lowered base level (flows)
by excavating the bed of the river and its valley. Riparian vegetative loss
has destabilized the etreambanks adding to the rate of lateral migration. The
most significant change ie the lowering of the base level. This has resulted
in channel rejuvenation (over-steepening of the grade headword, thus increasing
the gradient) for the South Fork as well ae the mainstem San Miguel Rivers.
This has caused the original channel to abandon its foodplain and become
entrenched. Ae a result, subsequent future flows are more damaging,
accelerating bank erosion as the stream attempts to gain enough width to
re-establish a floodplain and meander geometry for natural energy dissipation.
The project proposal consists of a plan to rehabilitate the South Fork San
Miguel River and the mainstem above its confluence with the South Fork.
Restoration efforts will include boulder and log placement for bank protection
and instream structure and re-aligning the channel into a configuration
consistent with this particular channel type. Additional work will be
conducted to reconstruct the floodplain and riparian area, and bring the
channel(s) back to a stable condition.
The proposal ie designed to: 1) halt further headcutting of the channel by
installation of grade control structures; 2) reduce accelerated bank erosion;
3) create a single channel and eliminate the braided pattern which now exists;
4) restore aquatic and riparian habitat quality; 5) reduce the potential impact
of future flood damage; and 6) restore the visual, aesthetic, biological and
physical qualities of the riverine environment.
The time frames outlined in the proposal require the Forest to undertake this
work before winter freeze-up (typically November). The project will take place
between August 1, 1996, and October 1, 1996, if weather conditions and flows
allow.
This proposed action and alternatives 2 and 3 are consistent with the overall
management direction provided within the Land and Resource Management Plan
(Forest Plan) for the Grand Mesa, Uncompahgre and Gunnison National Forest. 11
The Forest Plan for the Grand Mesa, Uncompahgre and Gunnison National Forest is
being implemented as required by the Forest and Rangeland Renewable Resources
Planning Act of 1974 (RPA, P.L. 93-378) and the National Forest Management Act
of 1976 (NFMA, P.L. 94-588). This Forest Plan provides the framework for the
action proposed here, and the action is being undertaken as one step in
implementing the Forest Plan. The proposed action meets the Forest Plan
Goal(s) of managing all the components of the aquatic riparian ecosystems, to
include the stream channel ecosystem, the riparian vegetative ecosystem, and
adjacent transitional ecosystems that are closely associated with the aquatic
and riparian ecosystems (Management Prescription, pp. III-173 through III-188).
The Forest Plan is on file in the Forest Supervisor's Office in Delta, CO.
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