Spatial Heterogeneity of Soil Shear Strength within the Large Complex Gully Systems on the Loess Plateau of China

Authors: Tongxin Zhu*, University of Minnesota
Topics: Geomorphology, Soils, Applied Geography
Keywords: soil shear strength, gully systems, mass movement, tunnel, Loess Plateau
Session Type: Paper
Presentation File: No File Uploaded

Although soil shear strength has been extensively measured in agricultural lands, very limited has been done within gullies. An understanding of the spatial heterogeneity of soil shear strength can provide insight into erosion mechanism within gully systems, and is a prerequisite to modeling gully erosion processes, as well as helps identify effective conservation measures for gully erosion control. In this study, a comprehensive investigation of soil shear strength within gully systems was conducted in a semi-arid, complex-terrain watershed on the Loess Plateau of China. In-situ soil shear strength was measured at various positions of the gully systems (e.g. gully headcut, walls, sideslope, knickpoint, gully bottom, tunnels, mass movement), in different kinds of deposits (colluvium and alluvium), as well as on surfaces with or without vegetation covers). For comparison, soil shear strength was also measured under different land use conditions in the inter-gully areas, such as terrace and slopeland under different tillage practices, as well as shrubland and woodland. In total, about 5000 measurements were taken in situ in the field prior to the rainy seasons of 2006 and 2008. The results demonstrated that soil shear strength within the gully systems has a much greater spatial variability than inter-gully areas. Mass movement along sideslopes and gully head sharply decreases soil shear strength of materials that are most prone to water erosion during the rainstorm. Shrubs and grasses growing on both sideslope and bottom of gullies increase soil shear strength substantially and therefore can be effective in reducing gully erosion.

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