We report characterization and radio assay of the surface run-off substances obtained (or collected) at the forest observation plots in the Ogi district of Kawauchi-mura and the Yamakiya district of Kawamata-machi, and at the soil-saving dam in the Ogaki district of Namie-machi, Fukishima prefecture, Japan. Both Cs-134 and Cs-137 were detected from soil samples taken in these areas, and their concentrations were high particularly in the fine substances (silts and clay). The radioactive caesium concentration of surface run-off soils which flowed out from Kawauchi, and Kawamata observation plot were on the same level with that of the splash erosion soils. The radioactive caesium concentrations of the Ogaki soil saving dam were increased with finer-sized particle contents, mainly silt fraction in the sample soils.
