Soil erosion and sediment deposition represent serious problems in the world. Several quantitative and qualitative techniques have been developed and used to measure soil erosion and deposition throughout the world. However, most of them do not produce the spatial patterns of soil redistribution within the fields to understand soil loss. Understanding of the spatial distribution of soil erosion and deposition within a catchment is important for designing soil and water conservation measures. Use of nuclear techniques in erosion monitoring and especially for qualification of soil loss has offered a fast and economical tool to estimate erosion rate. 137 Cs is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of nuclear weapons test primarily during the period of 1950s–1970s with the maximum rate of 137 Cs fallout from atmosphere in 1963. 137 Cs fallout is strongly and rapidly adsorbed by fine particles as by clay minerals and organic mater in the topsoil. Chemical or biological removal of 137 Cs from soil particles is negligible and it is assumed that only physical processes soil redistribution soil erosion and tillage practice are involved in 137 Cs traort. In the study area, soil erosion rates have increased greatly over natural rates as a result of human activities. Deforestation, over-grazing, changes in land-use and non-sustainable farming practices are main concerns of land degradation by human activity in the study. Therefore research objectives were to establish the spatial variability of cesium and to map the pattern of 137 Cs redistribution using geostatistics and variography, and to establish soil redistribution rate at the complex hill slope in the west of Iran , Chahar Mahal Bakhtieari province. 90 soil sample sites were surveyed with a Theodolite and in a grid pattern with 20 m distances. The dried soil samples sieved to pass through a 2 mm screen and were placed in Marinelli beakers and sealed for 137 Cs analyses. The 137 Cs activity (Bq kg ?1 ) was measured by gamma spectroscopy with a high-resolution germanium detector. Spatial correlation analyses of 137 Cs redistribution were performed with version 5.1 of GS + software and the different geostatistical parameters and the fitted model were introduced in the SURFER 8 Software to produce a map of the spatial distribution of 137 Cs and soil redistribution. The results of study showed that the mean erosion rate in the studied field estimated about 20.9 t ha ?1 year ?1 by applying the proportional model.
