Flooding deposit's environmental magnetism characteristics of Han Jiang River in 2005

摘要

The Hanjiang River has occurred the heaviest flooding since 1983 at the beginning of October, 2005. Through the systematic sample and analysis of flood deposit in different morphologic unit of Xiantao river section, we discover the characteristics of the magnetic fabric of Hanjiang River flood deposit as following: 1) the magnetic fabric parameter of different morphologic unit of stream channel has different characteristic; 2) river bed deposit's magnetic susceptibility anisotropy parameters κ, P, F, T and E, their statistical average values are all higher than the relevant value of flood plain, in contrast, the value of q and L in river bed are actually lower than the relevant value of flood plain; 3) in the three different sedimentary environments, river bed sediment in normal water level get the maximum κvalue, minimum q value; 4) the curve of the point bar deposit of the magnetic fabric's statistical values fluctuate most obviously, whereas the space of flood plain of this value change a little. 5) the shape factor of magnetic magnitude ellipse (T) of three morphologic units are all positive, ellipticity(E) are larger than 1 and show the basic characteristic of common river sediment. It is analyzed that the characteristic of magnetic fabric is consistent with miniature geomorphology and sedimentary structure of different morphologic unit in river channel, both of them are determined by the water kinetic energy of different morphologic unit when flood.