Deposition and Preservation of Sediment in Floodplain of the Yangtze River

Abstract:

In order to investigate the depositional processes and preservation of sediment in floodplain, two sediment cores were collected from the lower reach of the Yantze River. These two sediment cores were analyzed with grain size analyzer, ²¹⁰Pb and ^137Cs. Flood events were reconstructed mainly based on grain size of sediments and were compared with the recorded flood events happened in the drainage. These results demonstrate that only about one third flood events could be rebuiled and all the extreme floods could be identified via this way. This is in accordance with the previous research result gained also in the lower Yangtze River. A partial of floods could not be identified from the sediment cores maybe because the total deposition resulted from relatively small floods was eroded by strong flow during the subsequent extreme flood events whereas only a partial of deposition left by the extreme floods could be eroded by relatively small flood events, resulting in a partial of relatively small floods being invisible in the sediment cores. This needs further study via in-situ investigation or modelling.