Measurement and prediction of long-term soil-landscape change in the Palouse region induced by tillage and water erosion

{dollar}rmsp{lcub}137{rcub}Cs,{dollar} a fallout product of atmospheric nuclear weapons testing, irreversibly adsorbs onto clay particles and was used to assess the sources, rates, and spatial patterns of soil movement in a 15.1 hectare open watershed located in the Palouse region of eastern Washington. The mean {dollar}rmsp{lcub}137{rcub}Cs{dollar} soil erosion rate was then statistically compared with mean soil loss estimate computed using the Revised Universal Soil Loss Equation (RUSLE). A sediment mass balance for and sediment delivery ratio from the watershed were also calculated. Spatial patterns of sediment movement were assessed using geostatistical techniques.; The calculated mean RUSLE soil loss rate, adjusted to account for non-contributing areas, was {dollar}-41.5{dollar} tons{dollar}cdot{dollar}ha{dollar}sp{lcub}-1{rcub}cdot{dollar}yr{dollar}sp{lcub}-1{rcub}{dollar} while the calculated {dollar}rmsp{lcub}137{rcub}Cs{dollar} mean erosion rate (MER) was {dollar}-45.1{dollar} tons{dollar}cdot rm hasp{lcub}-1{rcub}cdot{dollar}yr{dollar}sp{lcub}-1{rcub}.{dollar} The RUSLE soil loss rate was significantly less than the MER at the 0.05 level of probability. The sediment yield rate and sediment delivery ratio for the watershed were computed to be {dollar}-36.6{dollar} tons{dollar}cdot rm hasp{lcub}-1{rcub}cdot{dollar}yr{dollar}sp{lcub}-1{rcub}{dollar} and 81%, respectively.; Soil loss rates in the watershed were greatest on shoulders and decreased down the hillslope to backslopes and footslopes. Doubly concave landscape components experienced significantly lower soil loss rates than did doubly convex components. Soil loss rates on doubly convex backslopes were significantly greater than on linear concave footslopes and doubly concave backslopes.; Geomorphometric analysis revealed no watershed-wide correlation between soil movement rate and aspect. Soil movement rate increased slightly, however, with increasing profile curvature, contour curvature, and relative elevation.; Geostatistical analysis showed the directions of maximum and minimum spatial continuity of elevation to be {dollar}(0spcirc){dollar} and {dollar}(90spcirc),{dollar} respectively while the directions of maximum and minimum spatial continuity of soil movement rates were {dollar}(60spcirc){dollar} and {dollar}(0spcirc),{dollar} respectively. The discordance between the directions of maximum spatial continuity of elevation and soil movement rate may be due to spatial and temporal variations in erosional and depositional processes caused by spatial and temporal variations in topographic, soil, climatic/hydrologic, and management factors.