78
6 A Close Look of the Gravity Erosion …
6.3 Methods and Materials
Most of the landslide data were collected from the Bulletin of National Geological Disaster (CGEIS 2016), and others were obtained from academic monographs,
journal articles and the investigation undertaken by the authors of this book. In the
Bulletin of National Geological Disaster, the location, time, volume, death toll and
direct economic loss of each landslide were collected in field investigations conducted
by the expert group, and triggering factors were analyzed according to the results of
field investigation together with the data on meteorology, precipitation, earthquake
and engineering. The landslide volumes were obtained from the field measurement
or the field investigation coupled with remote sensing interpretation or on-site survey combined with aerial photograph and synthetic aperture radar. In the academic
monographs and journal articles, landslide data were gathered from the field investigation, exploratory boring, monitoring, and survey of the representative landslides
and interpretation of remote sensing results. For instance, Tang (2014) performed
field investigation in the southern area of Yulin in the northwest of China to obtain the
loess landslide data about the location, time, volume and triggering factors, and so did
Song et al. (1994). Wang (2004) and Liu (1998) analyzed triggering factors and creep
behavior via field investigation and deformation monitoring, while Guo et al. (2014)
obtained the amount of landslide through field measurement coupled with remote
sensing interpretation. Furthermore, a geophysical survey was chosen to estimate
the landslide volume (Huang 2009), whereas a comprehensive method including
ground survey, measurement of typical landslides and remote sensing interpretation
was utilized to acquire landslide data about geometrical characteristics (Chen et al.
2013).
To get a close look at the landslides on the Loess Plateau, the authors trudged
along the Liudaogou Catchment in Shenmu County of Shaanxi Province from July
to August, 2014. After that, the authors also trekked into the rural area of the Lvliang
City, Shanxi Province in May, 2015 to investigate local disasters, including landslides
in Tuban Town, Houwa Village, Shang’an Village and Wangjiagou Catchment, as
well as some small-scale mass failures in other areas. All these collapse sites were
measured and photographed. In addition, the authors interviewed local villagers and
the researchers in the Water Conservancy Bureau of the local government. The distances between the control points were measured with a long steel tape and a laser
range finder. Subsequently, pictures of the landslides containing the control points
were put into AutoCAD to portray the margin of the landslides, and then the collapse
area within the margin could be calculated in the software. The volumes of undisturbed failure blocks could be directly measured through the laser range finder and
the tape. However, for the landslide sites that had been cleared of residual materials,
the volumes of the failure blocks could not be obtained by direct calculation. Fortunately, from previous experiences reported in the literature, the empirical relationship
linking landslide area A and volume V could be used to calculate the volumes of the
failure blocks (Chen et al. 2015; Guzzetti et al. 2008). Here, the volume-area scaling relation is used to estimate individual landslide volumes: V = 6.4473 × A
1.1422 ,
6 A Close Look of the Gravity Erosion …
6.3 Methods and Materials
Most of the landslide data were collected from the Bulletin of National Geological Disaster (CGEIS 2016), and others were obtained from academic monographs,
journal articles and the investigation undertaken by the authors of this book. In the
Bulletin of National Geological Disaster, the location, time, volume, death toll and
direct economic loss of each landslide were collected in field investigations conducted
by the expert group, and triggering factors were analyzed according to the results of
field investigation together with the data on meteorology, precipitation, earthquake
and engineering. The landslide volumes were obtained from the field measurement
or the field investigation coupled with remote sensing interpretation or on-site survey combined with aerial photograph and synthetic aperture radar. In the academic
monographs and journal articles, landslide data were gathered from the field investigation, exploratory boring, monitoring, and survey of the representative landslides
and interpretation of remote sensing results. For instance, Tang (2014) performed
field investigation in the southern area of Yulin in the northwest of China to obtain the
loess landslide data about the location, time, volume and triggering factors, and so did
Song et al. (1994). Wang (2004) and Liu (1998) analyzed triggering factors and creep
behavior via field investigation and deformation monitoring, while Guo et al. (2014)
obtained the amount of landslide through field measurement coupled with remote
sensing interpretation. Furthermore, a geophysical survey was chosen to estimate
the landslide volume (Huang 2009), whereas a comprehensive method including
ground survey, measurement of typical landslides and remote sensing interpretation
was utilized to acquire landslide data about geometrical characteristics (Chen et al.
2013).
To get a close look at the landslides on the Loess Plateau, the authors trudged
along the Liudaogou Catchment in Shenmu County of Shaanxi Province from July
to August, 2014. After that, the authors also trekked into the rural area of the Lvliang
City, Shanxi Province in May, 2015 to investigate local disasters, including landslides
in Tuban Town, Houwa Village, Shang’an Village and Wangjiagou Catchment, as
well as some small-scale mass failures in other areas. All these collapse sites were
measured and photographed. In addition, the authors interviewed local villagers and
the researchers in the Water Conservancy Bureau of the local government. The distances between the control points were measured with a long steel tape and a laser
range finder. Subsequently, pictures of the landslides containing the control points
were put into AutoCAD to portray the margin of the landslides, and then the collapse
area within the margin could be calculated in the software. The volumes of undisturbed failure blocks could be directly measured through the laser range finder and
the tape. However, for the landslide sites that had been cleared of residual materials,
the volumes of the failure blocks could not be obtained by direct calculation. Fortunately, from previous experiences reported in the literature, the empirical relationship
linking landslide area A and volume V could be used to calculate the volumes of the
failure blocks (Chen et al. 2015; Guzzetti et al. 2008). Here, the volume-area scaling relation is used to estimate individual landslide volumes: V = 6.4473 × A
1.1422 ,