Identification of the deposited layers in landslides reservoir and investigation of the sediment yields during the later sixteenth century on the Hill Loess Plateau, China

摘要

There are many sediment trapping reservoirs in the Hill Loess Plateau. The Huangtuwa small catchment is selected as a research field where samples were collected in a sediment deposit profile with a vertical length of 12.73 m. By the variation of fine particle content and pollen concentration, 54 flood couples were identified. Taking the freeze-thawing disturbed texture as the sign of the latest flood couple in a year, it is ascertained that those 54 floods should happen in 31 years. Using pyramid volume calculation formula, the sediment yields of flood ranged between 716-30376 t center dot km(-2). The average sediment yield was 7106 t center dot km(-2). The annual sediment yields varied between 968-55579 t center dot(km(2) center dot a)(-1), and the average value is 12629 t center dot (km(2) center dot a)(-1). Compared with the modern annual sediment discharge of the Huaining River, the erosion rate in the Huangtuwa region 450 years ago was similar to the modern erosion rate. In the period from the 27th year to the 31st year, the average annual sediment yield increased sharply to 31309 t center dot (km(2) center dot a)(-1). It implied that re-reclamation of the abandoned land in the catchment since the landslide disaster, where vegetation had rehabilitated already, caused very severe soil erosion in the catchment.