Figure 1.
Geographic location and DEM of the Jiangjia gulley area and Fengjie County, southwestern China. (a) the Geographic location of the Jiangjia gulley area and Fengjie County; (b) the DEM of the Jiangjia gulley area; and (c) the DEM of the Fengjie county.
Figure 1.
Geographic location and DEM of the Jiangjia gulley area and Fengjie County, southwestern China. (a) the Geographic location of the Jiangjia gulley area and Fengjie County; (b) the DEM of the Jiangjia gulley area; and (c) the DEM of the Fengjie county.
Figure 2.
Schematic diagrams of the morphological skeleton algorithm showing (a) different positions of maximum disk sizes and (b) the whole skeleton, indicated with dashed lines.
Figure 2.
Schematic diagrams of the morphological skeleton algorithm showing (a) different positions of maximum disk sizes and (b) the whole skeleton, indicated with dashed lines.
Figure 3.
Morphological ridge and valley skeletons showing (a) binary image with valleys shown in white, (b) binary image with ridges shown in white, (c) morphological skeleton of valleys over shaded relief, (d) morphological skeleton of ridges over shaded relief, (e) closed morphological skeleton network in which each small region contains homogenous geomorphological features and (f) slope unit extracted by MIA-HSU method.
Figure 3.
Morphological ridge and valley skeletons showing (a) binary image with valleys shown in white, (b) binary image with ridges shown in white, (c) morphological skeleton of valleys over shaded relief, (d) morphological skeleton of ridges over shaded relief, (e) closed morphological skeleton network in which each small region contains homogenous geomorphological features and (f) slope unit extracted by MIA-HSU method.
Figure 4.
Schematic diagram of slope unit definition from the conventional method (reverse DEM = DEM rotated by 180° along the horizontal plane A-A′). Thus, high DEM values are turned into low values, and low DEM values are turned into high values, and the original drainage line is turned into a ridge line. “a” represents a sub-watershed obtained from the DEM data, and “b” and “c” are the watersheds obtained by the reverse DEM.
Figure 4.
Schematic diagram of slope unit definition from the conventional method (reverse DEM = DEM rotated by 180° along the horizontal plane A-A′). Thus, high DEM values are turned into low values, and low DEM values are turned into high values, and the original drainage line is turned into a ridge line. “a” represents a sub-watershed obtained from the DEM data, and “b” and “c” are the watersheds obtained by the reverse DEM.
Figure 5.
Ground LiDAR survey in the Jiangjia Gully area showing (a) DGPS base station (b) RIEGL Z-6200 laser scanner.
Figure 5.
Ground LiDAR survey in the Jiangjia Gully area showing (a) DGPS base station (b) RIEGL Z-6200 laser scanner.
Figure 6.
Point cloud data collection and processing in Jiangjia Gully area showing (a) data acquisition points with error fields and (b) point cloud data obtained from scanning, with density of points shown.
Figure 6.
Point cloud data collection and processing in Jiangjia Gully area showing (a) data acquisition points with error fields and (b) point cloud data obtained from scanning, with density of points shown.
Figure 7.
Topographic feature extraction for shallow landslides in Jiangjia Gully area showing results from (a) The MIA-HSU method and (b) The conventional method.
Figure 7.
Topographic feature extraction for shallow landslides in Jiangjia Gully area showing results from (a) The MIA-HSU method and (b) The conventional method.
Figure 8.
Standard deviation of slope gradient of slope unit; (a) the MIA-HSU method and (b) the conventional method.
Figure 8.
Standard deviation of slope gradient of slope unit; (a) the MIA-HSU method and (b) the conventional method.
Figure 9.
Photographs of the Xinpu landslide showing (a) front view, (b) Daping landslide terrace (T1), (c) Shangertai landslide terrace (T2) and (d) Xiaertai landslide terrace (T3).
Figure 9.
Photographs of the Xinpu landslide showing (a) front view, (b) Daping landslide terrace (T1), (c) Shangertai landslide terrace (T2) and (d) Xiaertai landslide terrace (T3).
Figure 10.
Geomorphological features of the Xinpu landslide showing (a) front view and (b) lateral view (the measuring points are marked with red stars).
Figure 10.
Geomorphological features of the Xinpu landslide showing (a) front view and (b) lateral view (the measuring points are marked with red stars).
Figure 11.
Geomorphological features of the Jijing landslide showing (a) front view and (b) lateral view (the measuring points are marked with red stars).
Figure 11.
Geomorphological features of the Jijing landslide showing (a) front view and (b) lateral view (the measuring points are marked with red stars).
Figure 12.
Geomorphological features of the Xinpu landslide based on slope unit extraction: (
a) front view and (
b) lateral view of slope units from the MIA-HSU method; (
c) front view and (
d) lateral view of slope units from the conventional method. Note that the three landslide terraces shown in
Figure 6 (T
1, T
2, and T
3) were extracted using the MIA-HSU method, which is not the case for the conventional method.
Figure 12.
Geomorphological features of the Xinpu landslide based on slope unit extraction: (
a) front view and (
b) lateral view of slope units from the MIA-HSU method; (
c) front view and (
d) lateral view of slope units from the conventional method. Note that the three landslide terraces shown in
Figure 6 (T
1, T
2, and T
3) were extracted using the MIA-HSU method, which is not the case for the conventional method.
Figure 13.
Results of terrain characteristic extraction from the Jijing landslide: (
a) front view and (
b) lateral view of slope units from the MIA-HSU method; (
c) front view and (
d) lateral view of slope units from the conventional method (Numbers one to seven in the slope units from MIA-HSU extraction correspond to numbers one to seven extracted from field measurement in
Figure 10).
Figure 13.
Results of terrain characteristic extraction from the Jijing landslide: (
a) front view and (
b) lateral view of slope units from the MIA-HSU method; (
c) front view and (
d) lateral view of slope units from the conventional method (Numbers one to seven in the slope units from MIA-HSU extraction correspond to numbers one to seven extracted from field measurement in
Figure 10).
Figure 14.
The slope unit extraction process of conventional method of Jijing landslide: (a) the divide lines extracted from normal DEM and (b) the drainage lines extracted from reverse DEM.
Figure 14.
The slope unit extraction process of conventional method of Jijing landslide: (a) the divide lines extracted from normal DEM and (b) the drainage lines extracted from reverse DEM.
Figure 15.
The slope unit extraction process of MIA-HSU method of Jijing landslide: (a) morphological skeleton of valleys and ridges over shaded relief and (b) closed morphological skeleton network in which each small region contains homogenous geomorphological features.
Figure 15.
The slope unit extraction process of MIA-HSU method of Jijing landslide: (a) morphological skeleton of valleys and ridges over shaded relief and (b) closed morphological skeleton network in which each small region contains homogenous geomorphological features.
Table 1.
The comparison of the Jiangjia Gulley area and the Fengjie county ([
5,
23,
25]).
Table 1.
The comparison of the Jiangjia Gulley area and the Fengjie county ([
5,
23,
25]).
Study Area | Mean Annual Precipitation (mm) | Elevation (m) | Climate | Lithology | Soil Type | Landslide Hazard |
---|
Jiangjia gulley area | 900 | 1020–3250 | subtropical and dry monsoon | gray slate | gravel soil | Mainly shallow landslide |
Fengjie county | 1145 | 70–2100 | subtropical and humid monsoon | Limestone and sandstone | gravel soil | Deep-seated landslide |
Table 2.
The shallow landslide contained in slope units.
Table 2.
The shallow landslide contained in slope units.
ID of HSU | Shallow Landslide Number | ID of Conventional Slope Unit | Shallow Landslide Number |
---|
102 | 1 | 45 | 6 |
104 | 6 | 70 | 4 |
106 | 2 | 71 | 2 |
111 | 3 | 78 | 4 |
124 | 4 | 120 | 1 |
146 | 2 | 123 | 1 |
159 | 1 | 142 | 1 |
Table 3.
The measurement result of landslide terrace 1–3 in the Xinpu landslide.
Table 3.
The measurement result of landslide terrace 1–3 in the Xinpu landslide.
Landslide Terrace | 1 | 2 | 3 |
---|
Area (km2) | 0.19 | 0.22 | 0.30 |
x-coordinate of centroid point (km) | 916.92 | 916.97 | 916.79 |
y-coordinate of centroid point (km) | 3434.15 | 3434.71 | 3435.07 |
Table 4.
Jijing landslide measurement result.
Table 4.
Jijing landslide measurement result.
Terrain Regions | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
---|
Area (km2) | 0.16 | 0.12 | 0.21 | 0.19 | 0.32 | 0.13 | 0.18 |
x (km) | 928.339 | 928.126 | 928.025 | 927.842 | 927.577 | 928.442 | 928.809 |
y (km) | 3453.29 | 3453.61 | 3452.25 | 3453.01 | 3452.71 | 3452.36 | 3452.32 |
Table 5.
Area overlap degree of area of slope unit and landslide terraces 1–3 of the Xinpu landslide.
Table 5.
Area overlap degree of area of slope unit and landslide terraces 1–3 of the Xinpu landslide.
Landslide Terrace | T1 | T2 | T3 |
---|
AT (km2) | 0.19 | 0.22 | 0.30 |
AS (km2) | 0.13 | 0.18 | 0.28 |
AS ∩ AT (km2) | 0.12 | 0.10 | 0.26 |
i (%) | 63.15 | 63.63 | 86.67 |
Table 6.
The overlap degree of area of slope unit and terrain regions in Jijing landslide.
Table 6.
The overlap degree of area of slope unit and terrain regions in Jijing landslide.
Terrain Regions | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
---|
AT (km2) | 0.16 | 0.12 | 0.21 | 0.19 | 0.32 | 0.13 | 0.18 |
AS (km2) | 0.14 | 0.09 | 0.15 | 0.20 | 0.35 | 0.14 | 0.16 |
AS ∩ AT (km2) | 0.13 | 0.09 | 0.14 | 0.15 | 0.30 | 0.12 | 0.11 |
i (%) | 81.25 | 75.00 | 66.67 | 78.94 | 93.75 | 92.30 | 61.11 |