Relationship between sediment yield and socio-economic factors in the Upper Yangtze River

Taking Sichuan Province and Chongqing Municipality as an example, this paper studies the relationship between socio-economic factors and sediment yield in the Upper Yangtze River based on section data in 1989 and 2007. The results show that sediment yield is significantly correlated with population density and farmland area, in which the former appears to be more closely related to sediment yield. Moreover, in the relation of sediment yield vs. population density, a critical value of population density exists, below which the sediment yield increases with the increase of population density and over which the sediment yield increases with the decrease of population density. The phenomenon essentially reflects the influence of natural factors, such as topography, rainfall and soil property, and that of some human activities on sediment yield. Regions with higher population density than critical value are located in the east of the study area and are characterized by plains, hills and low mountains, whereas regions with lower level are located in the west and are characterized by middle and high mountains. In the eastern region, more people live on the lands with a low slope where soil erosion is slight; therefore, sediment yield is negatively related with population density. In contrast, in the western region, the population tends to be concentrated in the areas with abundant soil and water resources which usually lead to a higher intensity of natural erosion, and in turn, high-intensity agricultural practices in these areas may further strengthen local soil erosion.