Ground Freezing Effects on Soil Erosion of Army Training Lands
Part 2 : Overwinter Changes to Tracked-Vehicle Ruts,
Yakima Training Center, Washington
JONATHAN J. HALVORSON, DONALD K. MCCOOL,
LARRY G. KING, AND LAWRENCE W. GATTO
from late fall to early spring (Rickard 1988), coin-
INTRODUCTION
ciding with times of soil freezing. Information
Heavy tracked vehicles create ruts, compact
about how freezethaw cycles affect the shape and
soils, and disturb vegetation, thereby increasing
the degree of soil compaction in tank ruts is
the potential for erosion. Ruts can concentrate
important for assessing impacts of ruts on water
surface water flow, depending on orientation,
infiltration and soil erosion. In addition, soil ero-
slope, soil characteristics and landscape position
sion models such as RUSLE (USDA-NRCS 1997)
(Voorhees et al. 1979, Foltz 1993). The geometry
and WEPP (USDA-ARS 1997) can incorporate this
of hillslope channels, such as rills or ruts, is impor-
information to more accurately predict soil losses
tant because it influences the velocity and thus
on Army lands in cold climates.
erosivity of water flowing in it (Elliot and Laflen
This research is part of a CRREL/USDA-ARS
1993, Gatto 1997b). Soil compaction affects erosion
project to determine soil freezethaw effects on
by changing the stability and size distribution of
hydraulic geometry, soil strength, infiltration, run-
soil aggregates, and increasing soil bulk density
off erosivity and soil erodibility of vehicular ruts
and penetration resistance (Thurow et al. 1993,
and natural rills. Our specific goal for the 1995
Gatto 1997b). Small increases in soil bulk density
1996 winter was to determine the effect of soil
can result in disproportionately large decreases in
freezethaw cycles on the surface shape and com-
infiltration rates that increase the potential for
paction of M1 tank ruts. Changes in rut geome-
runoff (Meek et al. 1992). Vehicle traffic can phys-
try and degree of soil compaction are important
ically disrupt vegetation (Shaw and Diersing 1990,
to rut-flow hydraulics and erosion, and they can
Greene and Nichols 1996, Jones and Bagley 1997)
be readily measured by military land managers.
but may also indirectly impact plant growth by
altering nutrient availability, soil physical charac-
teristics, and patterns of soil moisture storage
RESEARCH SITES
(Wolkowski 1990, Buchkina 1997).
We established two research sites 8 December
Wind and water erosion (with cycles of wetting
1995 within the boundaries of an ongoing Tracked
and drying and freezing and thawing) modifies
Vehicle Impact Model (TVIM) study, managed by
rut geometry and ameliorates soil compaction
YTC personnel (Jones and Bagley 1997). We chose
(Thurow et al. 1993, Gatto 1997a,b, Sharratt et al.
these sites because they represent conditions com-
1997). As it thaws, frozen wet soil becomes tem-
mon on the YTC, were accessible, and had uniform
porarily weakened with a low resistance to ero-
vegetation and soil. In addition, information about
sion (Formanek et al. 1984, Kok and McCool 1990).
the date of rut formation and antecedent soil mois-
Freezethaw effects may be especially important
ture was available.*
in cool semiarid locations such as the Yakima
Training Center (YTC) in central Washington
(Fig. 1), where the majority of precipitation occurs
*Russell Fitzgerald, YTC, personal communication 1997.
Previous Page
