Sediment movement through riparian vegetation under simulated rainfall and overland flow
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Authors: R. A. Pearce, M. J. Trlica, W. C. Leininger, D. E. Mergen, and G. W. Frasier
Date: 1998
Journal: Journal of Range Management
Volume: 51
Number: 3
Pages: 301-308
Summary of Methods: Sediment movement over two riparian communities during a simulated rainfall (60 mm hr-1) event and overland flow were examined using three vegetation heights (unclipped, clipped to 10 cm, and clipped to soil surface) and two sediment treatments (sandy loam and ground silica loam) along Sheep Creek in the Roosevelt National Forest of Colorado during summer for two years. The first experiment evaluated the movement of sand particles >200 µm. A second experiment examined the movement of particle size classes (2-10, 10-30, 30-50, 50-100, and 100-200 µm) collected in sediment traps established 60, 120, and 180 cm downslope from the upslope border of the simulator. Stubble height, vegetation cover, vegetation density, litter cover, species composition, surface roughness, bare ground, slope, soil texture, and rock cover were measured.
Article Summary / Main Points: When vegetation was clipped to the soil surface, sand movement (downslope) increased compared to undisturbed vegetation. The largest difference in movement of finer particles occurred between the 2-10 and 10-30 µm particle ranges. The amount of 2-10 µm particles collected at 180 cm downslope was greater than that collected at 60 or 120 cm when vegetation was clipped to the soil surface. As vegetation height increased there was a smaller amount of 10-30 µm particles recovered at 120 cm downslope. Vegetative cover is more important in defining sediment movement than stubble height. Other factors such as biomass, vegetation density, vegetative cover and coarse particle size also influenced sediment movement. Therefore, stubble height guidelines are not the most effective way to manage riparian areas.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 48A Southern Rocky Mountains
Agrovoc Control Words: Riparian zones Runoff Sediment retention
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: stubble height, erosion, transport capacity, sediment filtration, particle size distribution, nonpoint source pollution
Annotation: This was a replicated study over two years, with results applicable across many montane riparian areas. This study illustrated that vegetated stream banks increase sediment deposition compared with bare stream banks. Managing ecosystems just for stubble height may not address complex issues such as sediment movement, filtration and detachment and therefore additional variables influencing sediment movement should be studied for managing riparian zones. Additionally, Pearce et al. (1997, J. Environ. Quality 26:139-144) studied the effectiveness of grass buffer strips on sediment filtration in lab simulations and Pierce et al. (1998, J. Range Manage. 51:309-314) studied sediment filtration in montane riparian zones under rainfall simulation. Together all three Pierce et al. articles present important research for understanding sediment filtration under simulated rainfall and overland flow.
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