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Measuring and Modeling Runoff, Soil Erosion and Sediment Yields to assess Management Options in the Post-Fallout Watersheds of Iitate Village, Fukushima, Japan
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  • Chris Renschler,
  • Kazutoshi Osawa,
  • Takuhei Yamasaki,
  • Taku Nishimura
Chris Renschler
University at Buffalo

Corresponding Author:[email protected]

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Kazutoshi Osawa
Utsunomiya University
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Takuhei Yamasaki
The University of Tokyo
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Taku Nishimura
The University of Tokyo
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Following the radioactive fall out of the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, radiocesium (Cs-137) contaminated soils of forests, uplands, rice paddies and other land uses released contaminated sediments onto neighboring areas and into the creeks and rivers in Iitate Village, Japan. The study used conventional and Cs-137 fingerprinting techniques to determine runoff and suspended sediment discharges to assess the small and large-scale soil redistribution dynamics within contributing areas in two watersheds. Also, we attempted to use Cs-137 fingerprinting to identify spatial and temporal patterns of erosion, transport and sedimentation on hillslopes within those watersheds. Tributaries near the outlet of the 30 km2 Hiso watersheds were simulated at the hillslope and watersheds using the process-based Water Erosion Prediction Project (WEPP) model and the Geospatial Interface for WEPP (GeoWEPP). Besides the simulation of historic soil redistribution events, a particular emphasis was the identification and assessment of various land use and cover changes on the past soil redistribution. Results of the analysis in the post-fallout landscapes enables scientists and farmers as well as natural resources and disaster managers to investigate the consequences of active and passive land use and cover changes on the runoff and sediment dynamics at the plot, hillslope and watershed scales. Especially the behavior of Cs-137 contaminated clay particles in soils and sediments seem to be the key for the success of the measurement, modeling and management techniques. The result of this study has the potential to assist decision and policymaking for stakeholders not only in areas that were impacted by the contamination through radioactive fallout.