Study on Lacustrine Sediments Responsing to Climatic Precipitation and Flood Discharge in Lake Taihu Catchment,China

It is necessary to know long-term flood records and the sequence for understanding the features and periods of extreme flood,while lacustrine sediments from Taihu Lake has provided the records much longer than the observations.This paper has reconstructed historical flood events during the past 150 years in Taihu Lake catchment,by sedimentary records from TXS core in the centre of the open water.Dating of the 210Pb and 137Cs and characteristics of the grain size and magnetic susceptibility were analyzed,and sedimentary flood index were configureated which have been correlated with regional summer precipitation and flood discharge in the lower reaches of the Yangtze River.Results showed that there were about 24 events of the extreme large floods when we used cutoff the 90th percentiges for the discharge(Q≥90th%) and summer precipitation(Pjja≥90th%) from historical documents since 1840AD.Compariably,flood index from grain size of sedimentary sand(64 μm) and low-frequency magnetic susceptibility can catch 15 flood events during the past 150 years,62.5% corespending with the historical records.This result supported that lacustrine sediment records can well reconstruct the paleoflood change,and provid scientific basis of sedimentology and magnetic susceptibility to recognize centenary timescale extreme floods in features and periods.