VALIDATION OF137 Cs TECHNIQUE IN SOIL EROSION AND SEDIMENTATION STUDIES

Soil is the basic constituent required for the production of plants and livestock and this necessary component is mostly affected by erosion worldwide. This factor neglected by most of the developing countries because of the longer time and larger manpower needed to estimates the actual rates of erosion by conventional methods. An alternate, economic and less time-consuming method being applied in many developed countries is the use of fallout radionuclides (FRN) in estimating not only erosion but also re-distribution within the catchment. For this purpose, the reference site was established at Lokot area 33oo52’37”N, 7323’74”E at altitude 1477 m above the mean sea level near the newly constructed Murree Motorway having the total 1372 Cs inventory 4910 Bq/mwith very smooth and well distributed profile along the depth. Mass Balance 1 and the Profile Distribution Model were applied to calculate the soil redistribution. The soil redistribution at fields in Pind Begwal, Islamabad area range from 116 to12.7 t/h/yr and at Savor village ranging from 127 to 24 t/h/yr. The permanently grassy patches in the same area have very low erosion (~ 2 t/h/yr). Five samples collected from the area along road construction site on main Murree Motorway have shown severe erosion of topsoil ranging from 176 to 0.7 t/h/yr. The samples collected from the deforested hill in the same area indicate the severe erosion of around 176 t/h/yr. In comparison to this location, the samples in the same area with forest/ permanent plant cover, value range from (erosion) 14 t/h/yr to deposition of 5.4 t/h/yr at different points. In general, the human induced activities are found to be the major source of erosion in this area.