Field Monitoring and Application Of WEPP Model For Sediment and Radiocesium Movements In Fukushima.

Sediments containing radiocesium carried by runoff from surrounding mountains into rivers were monitored in Iitate Village, Fukusima contaminated with radionuclides fallout by the accident of the Fukushima Daiichi Nuclear Power Plant. A monitoring system is composed of rain gauge, water level sensor, water velocimeter, turbidity sensor, and water sampler. The system was installed at Hiso River and Mano River. Around Hiso River is the place where the contamination is the most serious in this village. As the result, radiocesium ran off with suspended sediment and organic matter. The concentration of Cs137 was increased to 9.4 Bq/L in a storm event. It can be expressed 107 kBq/kg-SS as the content in suspended solids. We also prepared the datasets for Water Erosion Prediction Project, WEPP to estimate the sediment and radiosesium movements in these watersheds. These results and management practices that minimize the radiation dose will be presented.