Chapter 12
Effects of Gravity Erosion on Particle
Size Distribution of Suspended Sediment
Abstract Gravity erosion generates an enormous volume of sediments on steep
slopes throughout the world, yet its effect on the particle size distribution of suspended sediments (PSDSS) remains poorly understood. In this chapter, experiments
were conducted in a field mobile laboratory in which mass movements were triggered on steep slopes under simulated rainfall. A suite of indexes such as median
sediment size (d 50 ), sediment heterogeneity (H), fractal dimension (D), and enrichment/dilution ratio (R ed ) were used to evaluate the effect of mass movement on
PSDSS. Mass movements led to a drastic increase in the sediment concentration and
the enrichment of fine particles, which developed into hyperconcentrated flows. R ed s
for clay, silt, and sand fractions were 13.9, 1.4, and 0.7 respectively. The d 50 , H,
and D were significantly correlated with slope failures. The changes of PSDSS after
mass movements reflected a combined complex effect of soil sources, erosion types,
selective detachment, and deposition processes.
Keywords Gravity erosion · Landforms · Particle size distribution · Sediment ·
Soils
12.1 A Review on the Study of Particle Size Distribution
of Suspended Sediment on Steep Slopes
Gravity erosion, also referred to as mass movement or mass wasting, is slope failures on steep slopes driven by self-weight, which is in contrast to other types of soil
erosion processes that require physical impetus of wind or water. Forms of gravity
erosion include landslide, avalanche, and earthflow (Xu et al. 2015a). Slope failures are not only a hazard in almost all countries, causing billions of dollars of
damages and many casualties, but also contribute to landscape evolution and erosion in mountainous regions (Keefer and Larsen 2007). Moreover, slope failures
could deliver a huge amount of sediments to rivers throughout the world, and seriously affect the structure and function of ecosystems and society. For example, a
streamside landslide delivered 60,000 of mixed-size sediment to the Navarro River
in California in the spring of 1995 (Sutherland et al. 2002). In some catchments of the
Loess Plateau, mass movement contributed over 50% of the total sediment discharge
© Science Press and Springer Nature Singapore Pte Ltd. 2020
X. Xu et al., Experimental Erosion,
https://doi.org/10.1007/978-981-15-3801-8_12
191
Effects of Gravity Erosion on Particle
Size Distribution of Suspended Sediment
Abstract Gravity erosion generates an enormous volume of sediments on steep
slopes throughout the world, yet its effect on the particle size distribution of suspended sediments (PSDSS) remains poorly understood. In this chapter, experiments
were conducted in a field mobile laboratory in which mass movements were triggered on steep slopes under simulated rainfall. A suite of indexes such as median
sediment size (d 50 ), sediment heterogeneity (H), fractal dimension (D), and enrichment/dilution ratio (R ed ) were used to evaluate the effect of mass movement on
PSDSS. Mass movements led to a drastic increase in the sediment concentration and
the enrichment of fine particles, which developed into hyperconcentrated flows. R ed s
for clay, silt, and sand fractions were 13.9, 1.4, and 0.7 respectively. The d 50 , H,
and D were significantly correlated with slope failures. The changes of PSDSS after
mass movements reflected a combined complex effect of soil sources, erosion types,
selective detachment, and deposition processes.
Keywords Gravity erosion · Landforms · Particle size distribution · Sediment ·
Soils
12.1 A Review on the Study of Particle Size Distribution
of Suspended Sediment on Steep Slopes
Gravity erosion, also referred to as mass movement or mass wasting, is slope failures on steep slopes driven by self-weight, which is in contrast to other types of soil
erosion processes that require physical impetus of wind or water. Forms of gravity
erosion include landslide, avalanche, and earthflow (Xu et al. 2015a). Slope failures are not only a hazard in almost all countries, causing billions of dollars of
damages and many casualties, but also contribute to landscape evolution and erosion in mountainous regions (Keefer and Larsen 2007). Moreover, slope failures
could deliver a huge amount of sediments to rivers throughout the world, and seriously affect the structure and function of ecosystems and society. For example, a
streamside landslide delivered 60,000 of mixed-size sediment to the Navarro River
in California in the spring of 1995 (Sutherland et al. 2002). In some catchments of the
Loess Plateau, mass movement contributed over 50% of the total sediment discharge
© Science Press and Springer Nature Singapore Pte Ltd. 2020
X. Xu et al., Experimental Erosion,
https://doi.org/10.1007/978-981-15-3801-8_12
191