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ARS Home » Pacific West Area » Pullman, Washington » Northwest Sustainable Agroecosystems Research » Research » Publications at this Location » Publication #101009
Title: FREEZE-THAW-INDUCED GEOMORPHIC AND SOIL CHANGES IN AND OUT OF VEHICLE RUTS

Author
item GATTO, L - CRREL
item HALVORSON, J - WASHINGTON STATE UNIV.
item MCCOOL, DONALD

Submitted to: Engineering Geology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Land managers of military training lands must preserve and conserve soils to ensure that training can continue on those lands. Yet, military maneuvers damage vegetation, break up soil crusts, loosen surface soil, change soil-surface geometry, compact soils and often form ruts which channel surface water flow much like natural rills and increase soil erosion potential. We established research sites at Yakima Training Center in south central Washington and Ethan Allen Firing Range in northwestern Vermont. Field observations and measurements over two winters show: 1)tank ruts smoothed as sediment from rut crests slid into the rut during thaw; 2)freezing and thawing reduced the mean penetration resistance and bulk density of the upper 5 cm of soil in ruts; 3)below 5 cm depth, soil resistance and density in ruts were higher than out of ruts, especially when the soil was wet during tracking; 4)surface-water-runoff began sooner and runoff rates were 67 to 77% higher in ruts than on adjacent, untracked soil; and 5)scattered side wall slumps occurred along deeper rills during spring thaw, but slumped sediment was removed by subsequent flow. These results can be used to calibrate soil-erosion models for use by land managers of military-training lands in cold regions.

Technical Abstract: Land managers of military training lands must protect soils to ensure that training can continue on those lands. Yet, military maneuvers damage vegetation, break up soil crusts, loosen surface soil, change soil-surface geometry, compact soils and often form ruts which channel surface water flow and increase soil erosion potential. Flow in ruts and rills transport far more sediment than overland flow. However, the impacts of maneuvers change over time and our objective was to measure how soil freeze-thaw (FT) cycling changes compacted soil and the geometry of rills and military- vehicle ruts. We established research sites at Yakima Training Center in south central Washington and Ethan Allen Firing Range in northwestern Vermont. Field observations and measurements over two winters show: 1)tank rut cross sections smoothed as sediment from rut crests slid into the rut during thaw; 2)FT reduced the mean penetration resistance and bulk density of soil from 0 to 5 cm depth in ruts; 3)below 5 cm depth, soil resistance and density in ruts were higher than out of ruts, especially when the soil was wet during tracking; 4)saturated hydraulic conductivity was lower in straight ruts made on soil with 15% water, lower yet in turning ruts, and not statistically different in and out of ruts when tracking on soil with 5% water; 5)surface-water-runoff began sooner and runoff rates were 67 to 77% higher in ruts than on adjacent, untracked soil; 6)incipient rills formed in ruts while adjacent, untracked soils showed no rill initiation; and 7)scattered side wall slumps occurred during spring thaw, but slumped sediment was removed by subsequent flow. These results can be used to parameterize soil-erosion models for use by land managers of military- training lands in cold regions.