Spatial redistribution of Cs-137 and soil erosion on Orléans Island, Québec

Abstract

Cs-137 redistribution data have been used to estimate the extent and the pattern of long-term soil erosion in the Québec City area. Mean annual net soil movements ranging from a deposition of 10.8 t ha−1 yr−1 to a loss of 31.8 t ha−1 yr−1 were estimated. The slope steepness and the land use significantly influenced the estimated rates of soil movement, while soil texture was less important, probably because of the soils’ sandy texture or the high content of organic carbon, which kept their erodibility low. The net soil losses estimated from Cs-137 data were consistently higher than those predicted by the USLE. Besides net soil losses, it was possible to estimate separately the magnitude of soil detachment and soil deposition. Two–thirds of the stations sampled experienced net soil loss while the remaining third showed evidence of soil accumulation. These data suggest that the small net soil losses measured for low erosive conditions (flat slopes, dairy farming) result from important soil redeposition rates as much as from small soil detachment rates. Cs-137 redistribution data not only produce reliable estimates of soil movement rates, but also allow enhanced estimates of the agronomic and environmental impacts of soil erosion.Key words: Cs-137, erosion, sedimentation, USLE, sediment delivery ratio