Erosion and deposition in a field/forest system estimated using cesium-137 activity

Soil erosion and deposition were estimated using Cs-137 activity within a 7.25-ha field/forest system in the southeastern coastal plain. Sol eroded from the field was deposited both in the riparian forest ecosystem and in downslope areas of the field. Total activity, depth to peak activity, and depth to zero activity increased downslope from field to stream. Erosion and deposition rates, estimated by changes in activity per unit area from a reference undisturbed forest site, showed that about twice as much total deposition had taken place as total erosion. Excess deposition was attributed to deposition from the upstream portions of the watershed. Erosion and deposition rates estimated with this method were about 63 and 256 Mg/ha/yr, respectively. Erosion and deposition rates estimated by two different calculation techniques were nearly identical. These rates were considerably higher than rates estimated in an earlier study. The rates may be overestimated because the differential rates of Cs-137 movement on clay particles were not considered. The riparian ecosystem acted as a very efficient sediment trap. 19 refs., 5 figs., 3 tabs