PERMFILE103876

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 10 VEGETATION INFORMATION
• Media Type: D
• Archive: No

34
gallon of runoff water was much higher for the summer storm period than
for spring runoff.
The amount of total vegetative cover (Table 11) and the percent-
ages of both seeded and volunteer cover species have a marked affect
on the quantity of runoff and sediment yield for the summer storm
period. The treatment seeded ~.vith just shrubs and without any manage-
ment treatment had sediment yields that were considerably higher than
any other treatment; this treatment has the lowest total vegetative
cover and most of this cover is made up of volunteer cover species.
Sediment yields for the shrubs only treatment are even greater on the
4:1 slope. Treatments where the seeded species cover values are highest
have the lowest runoff and sediment yields; these treatments include
seeding shrubs, grasses, and forbs with the additional management
practice of mulching or mulching and fertilizing. Increasing the
slope to 4:1 did not greatly increase sediment yield for the mulched
and fertilized treatment.
The most important concept that can be gained from the runoff
and sediment yield data is the magnitude of the values. As was
mentioned earlier, the storms contributing to the June 24 sediment
values were relatively small and of a low intensity; one must consider
that an intense summer thunderstorm would result in much higher values.
A few of the collection culverts did leak when checked on
August 31, 1976; thus, maximum runoff values for spring runoff on
the plots with leaking culverts are not accurate. This leaking did
not affect sediment values, however, because the sediment is caught
in the primary collector (plastic garbage can) in each culvert.
Runoff values for the summer storm period were not affected by the
leaking because runoff did not exceed the volume of the primary
collector. The culverts were resealed in October 1976.
Vegetation
Shrub counts of bitterbrush are highest in the treatment that
was seeded with just shrubs on both the 11 ft. x 73 ft. runoff plots
(Table 11) and the 11 ft. x 22 ft. plots (Table 12). Bitterbrush
may also be responding to the mulch treatments (Table 11). Mulching
seems to be enhancing serviceberry establishment on the 11 ft. x 73 ft.
plots, however, this trend is not apparent on the mulched and ferti-
lized treatments of the 11 ft. x 22 ft. 4:1 slope plots by the end
of June and this may account for the lack of serviceberry seedlings
on these plots.
Big sage establishment was also enhanced by mulching; the
extremely high value (Table 11) for big sage on the mulched treatment
seeded with shrubs, grasses, and forbs is due to wind dispersal of
sage seed from nearby native stands. Observations on the revegetation
test plot in January and February of 1976 indicated that the prevailing
winds had been out of the southwest and snow drifts had accumulated
on the runoff plot with this very high sage seedling density. Big sage
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