EXPORT OF RADIOACTIVE CESIUM IN AN EXTREME FLOODING EVENT BY TYPHOON ETAU

Abstract

 We evaluated the behavior of radioactive Cs deposited by the accident of Fukushima Daiichi Nuclear Power Plant in the Uda River locating in the coastal region of Fukushima prefecture during the super heavy rain event (Typhoon Etau). The estimated total runoff volumes of Cs-137 from small forest catchment, dam lake, and the entire river catchment during the event were 1.4 to 5.3 times greater than the annual total runoff volumes in 2014, respectively. However, the sizes of Cs-137 runoff fell much below those of SS runoff from Matsugabou dam lake and the entire Uda River basin due to the decrease in concentrations of Cs-137 associated with SS by possible effect of decontamination operation in the catchments.