137Cs estimates of soil erosion rates in a small catchment on a channelized river floodplain in the lower reaches of Yangtze River, China

Abstract

Channelization significantly affects soil erosion in river floodplains. The object of this study was to use ¹³⁷Cs as a tracer to determine the ¹³⁷Cs inventory and derived soil erosion rates under various land use types in a catchment on channelized river floodplain in the lower reaches of Yangtze River, China. Sampling was carried out to establish a¹³⁷Cs reference inventory in a 70-year old paddy field located on the shoulder-slope of a local hill. The mean reference inventory of ¹³⁷Cs was 1275 Bq m^-2, whereas the ¹³⁷Cs inventory within the catchment ranged from 284 to 1150 Bq m^-2 and the soil erosion rates from -33.3 to -2.4 t ha^-1 yr^-1, respectively. The dominated land use of paddy in cultivated soils contributed relative low soil erosion. Bamboo and castanea mollissima were preferential for local land uses in uncultivated soils in comparison with woodland and Pinnus massoniana. The rates of soil erosion rates in old tea garden were higher than that in new tea garden. Overall, severe soil erosion and no deposition in the entire catchment occurred in the entire catchment due to the human-induced channelization in the 1970s. Our results suggest that restricting farmland being returned to tea plantations, thereby maintaining the current land use types would reduce soil erosion in river floodplain in the future.

Keywords: (137)Cs technique; Channelization; Small catchment; Soil erosion.