2.1 Development of the Experimental Erosion
9
and Willgoose (2004) investigated the effect of erosion on a back-filled and a capped
earthen dam wall by constructing an experimental landscape simulator in the laboratory. Due to the design of the rainfall simulator, it is difficult to directly scale
the rainfall-runoff processes to the field. Consequently, no attempt has been made to
match the rate of gully development on the tailings dam to field-scale processes.
Recently, downscaled model experiments on soil erosion in small watersheds
of the Loess Plateau have been performed, and good progress has been made in
similarity methodology. Shi et al. (1997a, b) observed the quantitative erosion in the
gullies and on slopes of the downscaled watershed model of the Xiaofanjiagou Gully,
Shaanxi Province. However, the proportions of soil erosion in gullies and on slopes
in the model were not very reliable, because the model runoff was underdeveloped
and erosion types were changed, compared with those in the prototype due to insufficient similarity in rainfall dynamics and ground cover. Jiang et al. (1994) and Yuan
et al. (2000a, b) performed a series of downscaled model experiments for different
degrees of erosion control in the small watersheds on the Loess Plateau to evaluate
the relationship between the runoff and soil loss, in which the explicit similarity
conditions to those in river engineering were considered. These experiments were
relatively successful; however, some aspects of the model design are still in dispute
(Zhang and Zhang 2000). The Chinese government has paid considerable attention
to the theory underlying scale models for soil conservation on the Loess Plateau. The
theory on model-based Loess Plateau has been proposed, which includes prototype,
digital model and physical model (Li 2001). Several national foundations have been
given to develop the theory designing the physical models, especially the scale models, which could simulate the soil erosion processes in the small watersheds on the
Loess Plateau.
The Loess Plateau is characteristic for the large area, complex geomorphology,
and considerable soil erosion. Many gullies are required to reduce soil and water loss.
Constructing check dams in the gullies is an effective strategy for reducing sediment
loss. More than 100,000 check dams have been built over the last 50 years on the Loess
Plateau; however, few analogous dams have been constructed in other countries. The
Chinese Ministry of Water Resources states that 163,300 check dams will be built on
the Loess Plateau by 2020 (MWRC 2003). Designing check dam systems requires
the estimates for (1) preferred dam sites, (2) the number of dams required and their
heights for sediment retention and flood control, and (3) the optimal sequence and
interval for dam construction. In an optimum design for the dam-construction, the
maximum amount of sediment can be retained by check dams, whereas the following
features are determinate: the number, location and capacity of check dams for a
catchment, and the erosion rate for the controlled area (Tian et al. 2003). However,
check dams have not been sufficiently discussed in the international literature. This
study presents a novel experimental method for assessing the soil retained by check
dams in the small watersheds on the Loess Plateau, China.
9
and Willgoose (2004) investigated the effect of erosion on a back-filled and a capped
earthen dam wall by constructing an experimental landscape simulator in the laboratory. Due to the design of the rainfall simulator, it is difficult to directly scale
the rainfall-runoff processes to the field. Consequently, no attempt has been made to
match the rate of gully development on the tailings dam to field-scale processes.
Recently, downscaled model experiments on soil erosion in small watersheds
of the Loess Plateau have been performed, and good progress has been made in
similarity methodology. Shi et al. (1997a, b) observed the quantitative erosion in the
gullies and on slopes of the downscaled watershed model of the Xiaofanjiagou Gully,
Shaanxi Province. However, the proportions of soil erosion in gullies and on slopes
in the model were not very reliable, because the model runoff was underdeveloped
and erosion types were changed, compared with those in the prototype due to insufficient similarity in rainfall dynamics and ground cover. Jiang et al. (1994) and Yuan
et al. (2000a, b) performed a series of downscaled model experiments for different
degrees of erosion control in the small watersheds on the Loess Plateau to evaluate
the relationship between the runoff and soil loss, in which the explicit similarity
conditions to those in river engineering were considered. These experiments were
relatively successful; however, some aspects of the model design are still in dispute
(Zhang and Zhang 2000). The Chinese government has paid considerable attention
to the theory underlying scale models for soil conservation on the Loess Plateau. The
theory on model-based Loess Plateau has been proposed, which includes prototype,
digital model and physical model (Li 2001). Several national foundations have been
given to develop the theory designing the physical models, especially the scale models, which could simulate the soil erosion processes in the small watersheds on the
Loess Plateau.
The Loess Plateau is characteristic for the large area, complex geomorphology,
and considerable soil erosion. Many gullies are required to reduce soil and water loss.
Constructing check dams in the gullies is an effective strategy for reducing sediment
loss. More than 100,000 check dams have been built over the last 50 years on the Loess
Plateau; however, few analogous dams have been constructed in other countries. The
Chinese Ministry of Water Resources states that 163,300 check dams will be built on
the Loess Plateau by 2020 (MWRC 2003). Designing check dam systems requires
the estimates for (1) preferred dam sites, (2) the number of dams required and their
heights for sediment retention and flood control, and (3) the optimal sequence and
interval for dam construction. In an optimum design for the dam-construction, the
maximum amount of sediment can be retained by check dams, whereas the following
features are determinate: the number, location and capacity of check dams for a
catchment, and the erosion rate for the controlled area (Tian et al. 2003). However,
check dams have not been sufficiently discussed in the international literature. This
study presents a novel experimental method for assessing the soil retained by check
dams in the small watersheds on the Loess Plateau, China.