Sediment Dynamics in Vehicle Ruts

摘要

Vehicle ruts often concentrate (channel) surface flow much like natural rills. These channeled flows have higher velocities and greater turbulence than overland sheet flows and detach and transport more sediment downslope. The velocity and turbulence of rut and rill flows are directly related to channel roughness and cross-sectional geometry. This study measured the amount of change in vehicle ruts that resulted from in-rut sediment erosion and deposition. Five vehicle-tracking plots were established in October 1996 and re-trafficked in October 1998 on a slope at the Ethan Allen Firing Range (EAFR) in northwestern Vermont, USA. The newly formed ruts varied from less than 1 to 7 cm deep and from 25 to 60 cm wide. Changes in rut cross-sectional geometry were measured at 46 locations to define seasonal and long-term sediment dynamics. Changes were defined by a root-mean-square (RMS) difference and the maximum erosion and deposition between corresponding points on successive cross sections. Generally the high RMS differences occurred in the winter-spring period when soil water was high due to thaw and snowmelt. Knowledge of in-rut sediment dynamics will be useful in soil-erosion prediction and landscape-evolution models, and could be used to identify landscape conditions on military training lands that should be avoided because they result in increased soil erosion.