12.1 A Review on the Study of Particle Size Distribution …
193
rain splash, sheet flow and rill flow (Hao et al. 2016; Govers 1985; Alberts et al.
1980). No experimental study has been conducted on the changes in the particle size
distribution of suspended sediment during the mass failure processes. In this study,
we carried out a series of experiments under simulated rainfall on the natural loess
slopes on the Loess Plateau of China. The experiment is a closely monitored segment
of unscaled reality. A suite of indexes such as median particle size (d 50 ), sediment
heterogeneity (H), fractal dimension (D) and enrichment/dilution ratio (R ed ) are then
used to evaluate the effect of gravity erosion on PSDSS. This study will be of theoretical and practical significance in understanding the sediment transport processes and
hyper-concentrated flows, as well as tracing the sources of sediments in the Yellow
River (Xu 2000).
12.2 Characteristics of the Liudaogou Catchment
Rainstorm-induced gravity erosion frequently occurs on the Loess Plateau due to
the crisscrossing gullies of the undulating terrain, sparse vegetation, and numerous
vertical joints in the loess deposits. Steep gully/valley banks with slope gradients
more than 70° in the upper reaches of small watersheds are particularly susceptible to
gravity erosion (Xu et al. 2015b). Sediment discharge from mass movement accounts
for a considerable proportion of the total soil loss (Xu et al. 2017). The study site,
Liudaogou Catchment (110°21
–110°23
E, 38°46
–38°51
N), is located in waterwind-gravity erosion crisscross region on the Loess Plateau, which is characterized
by a large number of deep gullies and undulating loess slopes (Fig. 12.1a). In this
area, gravity erosion, including avalanche, landslide, and earthflow, is very active
on steep slopes, and contributes a large amount of sediment yield in the catchment.
Field experimental results show that the amount of the gravity erosion might account
for 67% of the total erosion on the steep slopes of the Liudaogou Catchment (Guo
et al. 2016).
12.3 Methods and Materials
In the summer of 2014, a series of experiments were conducted on the natural loess
slopes in the Liudaogou Catchment, Shenmu County (Fig. 12.1). Three conceptual
landforms were “cut” in the field without disturbing the slope beneath. In other
words, the original texture and density of soils on the landforms were kept unaltered,
although the surface was cut to be smooth. Each of them covered an area of 3.0 m
by 2.8 m. All landforms had a height of 1.5 m and a gentle upper slope of 3°. The
steep lower slopes of the landforms were 60°, 70° and 80°, respectively. Underlying
the surfaces was sandy loess, with the d 50 of 0.108 mm. A mobile lab was set up in
the experimental spot to keep out sunshine and winds. Each simulated rainfall had
an intensity of 0.8 mm/min and a duration of 60 min. Five rainfalls were applied
193
rain splash, sheet flow and rill flow (Hao et al. 2016; Govers 1985; Alberts et al.
1980). No experimental study has been conducted on the changes in the particle size
distribution of suspended sediment during the mass failure processes. In this study,
we carried out a series of experiments under simulated rainfall on the natural loess
slopes on the Loess Plateau of China. The experiment is a closely monitored segment
of unscaled reality. A suite of indexes such as median particle size (d 50 ), sediment
heterogeneity (H), fractal dimension (D) and enrichment/dilution ratio (R ed ) are then
used to evaluate the effect of gravity erosion on PSDSS. This study will be of theoretical and practical significance in understanding the sediment transport processes and
hyper-concentrated flows, as well as tracing the sources of sediments in the Yellow
River (Xu 2000).
12.2 Characteristics of the Liudaogou Catchment
Rainstorm-induced gravity erosion frequently occurs on the Loess Plateau due to
the crisscrossing gullies of the undulating terrain, sparse vegetation, and numerous
vertical joints in the loess deposits. Steep gully/valley banks with slope gradients
more than 70° in the upper reaches of small watersheds are particularly susceptible to
gravity erosion (Xu et al. 2015b). Sediment discharge from mass movement accounts
for a considerable proportion of the total soil loss (Xu et al. 2017). The study site,
Liudaogou Catchment (110°21
–110°23
E, 38°46
–38°51
N), is located in waterwind-gravity erosion crisscross region on the Loess Plateau, which is characterized
by a large number of deep gullies and undulating loess slopes (Fig. 12.1a). In this
area, gravity erosion, including avalanche, landslide, and earthflow, is very active
on steep slopes, and contributes a large amount of sediment yield in the catchment.
Field experimental results show that the amount of the gravity erosion might account
for 67% of the total erosion on the steep slopes of the Liudaogou Catchment (Guo
et al. 2016).
12.3 Methods and Materials
In the summer of 2014, a series of experiments were conducted on the natural loess
slopes in the Liudaogou Catchment, Shenmu County (Fig. 12.1). Three conceptual
landforms were “cut” in the field without disturbing the slope beneath. In other
words, the original texture and density of soils on the landforms were kept unaltered,
although the surface was cut to be smooth. Each of them covered an area of 3.0 m
by 2.8 m. All landforms had a height of 1.5 m and a gentle upper slope of 3°. The
steep lower slopes of the landforms were 60°, 70° and 80°, respectively. Underlying
the surfaces was sandy loess, with the d 50 of 0.108 mm. A mobile lab was set up in
the experimental spot to keep out sunshine and winds. Each simulated rainfall had
an intensity of 0.8 mm/min and a duration of 60 min. Five rainfalls were applied