Formation and Evolution of Concentrated Flowpaths on a Pinyon-Juniper Woodland
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Authors
Costigan, Katie H.
Issue Date
2010
Type
Thesis
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Abstract
There has been a dramatic increase in the last thousand years in Pinyon-Juniper
woodlands, which is primarily attributed to global climate change. The focus of this
thesis is to describe the hydrologic impact of hand felling Pinyon and Juniper trees
perpendicularly to the slope to provide physical barriers to overland flow, reduce velocity
of flow, and minimize soil erosion. Experimental design consisted of two cover
conditions (naturally occurring bare interspaces and slash piles from felled trees on
naturally occurring bare interspaces) at two slope steepnesses (30% and 10%), and three
concentrated flow water application rates. Water was applied from a specially designed
flow initiator with pressure compensating flow regulators calibrated to rates of 15, 30 and
42 L min-1
for 12 minutes after runoff first occurred to quantify the ability of the
treatment to reduce concentrated erosion rates. Each treatment-slope-water application
rate combination was replicated three times.
The research indicates that hand felling Pinyon and Juniper trees can be highly
successful in reducing the size of concentrated flow paths, velocity and sediment load.
Results from this research also indicate that soil detachment is a far more complex
process that cannot be described in one function. There are processes such as soil
armoring, detachment capacity of water, and litter dams that are created that contribute to
the complexity of modeling soil detachment rates. This research is being used by the
USDA to develop concentrated flow equations for use in the Rangeland Hydrology and
Erosion Model (RHEM), which is being developed in support of the USDA‟s
Conservation Effects Assessment Project (CEAP).
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In Copyright(All Rights Reserved)