Abstract
We examine oceanic dispersal of the iRIC-Nays2DH-evaluated sediment and suspended 137Cs influxes from Niida River, Fukushima, with a particular attention to the first flood event in late May of 2011 after the Fukushima nuclear accident. Alongshore suspended 137Cs transport occurs assymetrically, comprising storm-driven southward transport confined in the shallow area due to shoreward Ekman transport associated with strong northerly wind, followed by northwestward widespread transport under mild southerly wind condition. About 70 % of the Niida River-derived suspended 137Cs remains near the mouth for 20 days after the flood event. Nevertheless, our model results as well as an observation suggest that the area is dominated by erosion as for high bed shear stress all the time, thus suspended radionuclides are redistributed to dissipate away in long term.
