WWRC 97-05ff
The Effects of Three Residual-Vegetation Heights on Streambank Sediment
Deposition and Vegetation Production
Abstract
This is a continuation of a study initiated by Rumsey
in 1994. The study is designed to test the validity of
the 15.2 cm residual vegetation height standard
currently used by land managers. The study is being
conducted along Spring Creek, in the city of Laramie,
Wyoming. The objectives are to measure and
compare above-ground vegetative production, below-ground
biomass, stem density, and sediment
deposition on stream banks when residual vegetation
is maintained at 2.5, 7.6, 15.2 cm, and unclipped
vegetation heights, and to measure suspended
sediment during high flow events. Sample plots
located with a 1m2 grid were maintained at the
designated treatment levels. Each treatment level
(2.5, 7.6 and 15.2 cm and unclipped control) was
replicated four times per reach on five reaches.
Vegetation from the plots was collected, dried and
weighed. Buffer zones 3 m upstream and
downstream were maintained at the designated
treatment levels to ensure consistent flow across
sample plots. Sediment deposition was measured
immediately following a high flow event using nine
uniformly spaced 2.5 cm2 stakes set flush with the
ground. Stem density counts were taken inside and
outside of the sample plots and will be used to
compare Spring Creek with other streams in the area
and to see how density affects sediment deposition.
Base flow measurements and suspended sediment
load were determined. Preliminary results suggest
significant differences in vegetation production
between the 2.5 cm and the unclipped with the other
treatments. The 2.5 cm showed more cumulative
production than the other clipped treatments, but not
more than the unclipped. No significant differences
were found between the 7.6 and 15.2 cm treatments.
No significant differences were found for sediment
deposition between treatment levels. Stem density
inside the plots was not significantly different from
outside the plots. The relationship between stem
density and the amount of sediment deposited was
minimal.
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