Consequences of the river valley bottom transformation after extreme flood (on the example of the Niida River, Japan)

3rd International Conference Environment and Sustainable Development of Territories: Ecological Challenges of the 21st Century

生态环境科学;地球科学;经济学

Botavin, D.^1 ; Golosov, V.^1 ; Konoplev, A.^2 ; Wakiyama, Y.^2

Faculty of Geography, Lomonosov Moscow State University, Leninskie Gory, 1, Moscow

119991, Russia^1

Institute of Environmental Radioactivity, Fukushima University, Fukushima, Japan^2

关键词: Alluvial soil;    Direct measurement;    Extreme flood events;    Quantitative assessments;    Sedimentation rates;    Spatial changes;    Time interval;    Top-soil layer;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/107/1/012002/pdf
DOI  :  10.1088/1755-1315/107/1/012002

学科分类：环境科学（综合）

来源: IOP

【 摘 要 】

Detailed study of different sections of floodplain was undertaken in the Niida River basin (Fukushima Prefecture) after an extreme flood event which occurred in the middle of September 2015. The upstream part of the basin is located in the area with very high level of radionuclide contamination after the accident at Fukushima Dai-ichi NPP. Field and GIS methods were used, including direct measurement of the depth of fresh sediment and its area, with soil descriptions for the typical floodplain sections, measurement of dose rates, interpretation of space images for a few time intervals (before and after flood event) with the following evaluation of spatial changes in deposition for different floodplain sections. In addition, results of quantitative assessment of sedimentation rates and soil radionuclide contamination were applied for understanding the effect of extreme flood on alluvial soils of the different sections. It was established that the maximum sedimentation rates (20-50 cm/event) occurred in the middle part of the lower reach of the Niida River and in some locations of the upper reaches. Dose rates had reduced considerably for all the areas with high sedimentation because the top soil layers with high radionuclide contamination were buried under fresh sediments produced mostly due to bank erosion and mass movements.