Disastrous Flood Events Found in Lacustrine Sediments from Lake Biwa(<Featured Articles>Mega-Earthquake and Geomorphic Hazards)

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Sediment core samples were obtained from Lake Biwa, central Japan, to clarify the hydro-environmental fluctuation that has occurred over the past 100 years on the basis of the physical properties of the sediments. The analysis of the core sediments showed that disastrous flood events, the Isewan Typhoon (IT; 1959) and Meiji heavy rainfall (MH; 1896), are clearly recorded in the physical properties of the sediments; the density and mineral content of the sediments from the events were large. They are positively proportional to rainfall intensity (70-mm excess rainfall). The mineral grain size in the IT period was large, while that in the MH period was small. These sizes are closely related to the distance from the river mouth to the sampling point (water level). The mineral grain size distribution here may be a function of the rainfall intensity in the catchment and the transport distance from the river mouth.
2012-10-25