In Part II, representative case studies on erosion research are exhibited, with the
purpose of providing a scientific context of soil conservation in the semiarid
regions, particularly on the Loess Plateau of China, as well as testifying the
effectiveness and practicability of the above devices. Chapter 6 describes the statistical analysis and field investigation of landslides on the Loess Plateau. Data
collected here may provide the prototype proofs to study soil conservation with
field experiments. Chapter 7 calculates the impact factors of conservation practices
on soil, water, and nutrients in a representative catchment of the Loess Plateau
based on field experiments. The results show that soil erosion and nutrient loss had
been greatly mitigated with various conservation practices, and check-dam was the
most appropriate conservation practice on the Loess Plateau. In Chap. 8, a runoff
simulation experiment for a single check-dam and a rainfall simulation experiment
for the whole check-dam system were conducted. The experiments demonstrate a
characteristic phenomenon, i.e., relative stability of the check-dam system on the
Loess Plateau and evaluated the effects of the dam construction sequence on the soil
deposition in the catchment. The gravity erosion is a dominant geomorphic process
on the steep loess slopes. In Chap. 9, rainfall simulation experiments were conducted to monitor the occurrence and behavior of the mass failure on steep loess
slopes. The results show that the avalanche played a crucial role of soil erosion as
the landform was made with loess by hand patting. Chapter 10 describes a series of
laboratory experiments aiming to test the stability of different slope geometries
under rainfalls. A sensitivity analysis is also performed to quantitatively explore the
triggering mechanisms of mass failures on the steep loess slope. In Chap. 11, a
series of experiments in the laboratory were conducted to observe the slope
geometries after mass failures, and then a sensitivity analysis was performed to
quantitatively explore the triggering mechanisms of failure scars on the steep loess
slope. Chapter 12 introduces the rainfall simulation experiments conducted on the
natural loess slopes where a series of mass failures happened under the simulated
rainfall. An index of enrichment/dilution ratio was used to quantitatively explore
the change of suspended sediment sizes affected by gravity erosion. In Chap. 13,
detailed monitoring of water and sediment delivery from the major tunnel systems
was conducted in a small semiarid sub-basin, locally known as the Yangdaogou
Catchment, in the hilly loess region of the Loess Plateau.
Beginning in 2001, a series of experimental studies were performed by the first
author together with his students and partners to generate and test the hypotheses
for the mechanism of the soil erosion on slopes and gullies, sediment storage effects
of check-dam systems, and behaviors and triggers of gravity erosion on the steep
slope. Some papers have presented the results of these experiments, but much of the
work remains unpublished. The characteristic features that make the study distinctive are shown as follows: (1) The theory system, i.e., the three pillars of the
Experimental Erosion, is presented in this book. The theoretical concepts presented
here are those needed for an understanding of soil behavior in the laboratory/field
tests described in subsequent chapters. A semi-scale model for simulating soils
retained by check-dams, the increase-rate-analysis method to evaluate the sensitivity of the erosion to the causal factors, a moveable laboratory for field tests, a
xiv
Preface
purpose of providing a scientific context of soil conservation in the semiarid
regions, particularly on the Loess Plateau of China, as well as testifying the
effectiveness and practicability of the above devices. Chapter 6 describes the statistical analysis and field investigation of landslides on the Loess Plateau. Data
collected here may provide the prototype proofs to study soil conservation with
field experiments. Chapter 7 calculates the impact factors of conservation practices
on soil, water, and nutrients in a representative catchment of the Loess Plateau
based on field experiments. The results show that soil erosion and nutrient loss had
been greatly mitigated with various conservation practices, and check-dam was the
most appropriate conservation practice on the Loess Plateau. In Chap. 8, a runoff
simulation experiment for a single check-dam and a rainfall simulation experiment
for the whole check-dam system were conducted. The experiments demonstrate a
characteristic phenomenon, i.e., relative stability of the check-dam system on the
Loess Plateau and evaluated the effects of the dam construction sequence on the soil
deposition in the catchment. The gravity erosion is a dominant geomorphic process
on the steep loess slopes. In Chap. 9, rainfall simulation experiments were conducted to monitor the occurrence and behavior of the mass failure on steep loess
slopes. The results show that the avalanche played a crucial role of soil erosion as
the landform was made with loess by hand patting. Chapter 10 describes a series of
laboratory experiments aiming to test the stability of different slope geometries
under rainfalls. A sensitivity analysis is also performed to quantitatively explore the
triggering mechanisms of mass failures on the steep loess slope. In Chap. 11, a
series of experiments in the laboratory were conducted to observe the slope
geometries after mass failures, and then a sensitivity analysis was performed to
quantitatively explore the triggering mechanisms of failure scars on the steep loess
slope. Chapter 12 introduces the rainfall simulation experiments conducted on the
natural loess slopes where a series of mass failures happened under the simulated
rainfall. An index of enrichment/dilution ratio was used to quantitatively explore
the change of suspended sediment sizes affected by gravity erosion. In Chap. 13,
detailed monitoring of water and sediment delivery from the major tunnel systems
was conducted in a small semiarid sub-basin, locally known as the Yangdaogou
Catchment, in the hilly loess region of the Loess Plateau.
Beginning in 2001, a series of experimental studies were performed by the first
author together with his students and partners to generate and test the hypotheses
for the mechanism of the soil erosion on slopes and gullies, sediment storage effects
of check-dam systems, and behaviors and triggers of gravity erosion on the steep
slope. Some papers have presented the results of these experiments, but much of the
work remains unpublished. The characteristic features that make the study distinctive are shown as follows: (1) The theory system, i.e., the three pillars of the
Experimental Erosion, is presented in this book. The theoretical concepts presented
here are those needed for an understanding of soil behavior in the laboratory/field
tests described in subsequent chapters. A semi-scale model for simulating soils
retained by check-dams, the increase-rate-analysis method to evaluate the sensitivity of the erosion to the causal factors, a moveable laboratory for field tests, a
xiv
Preface