Department of Industry

Landslide susceptibility mapping: A remote sensing based approach using QGIS 2.2 (Valmiera) 1

Technical manual 1

1.Introduction 8

1.Introduction 8

a.How to use this manual 9

a.How to use this manual 9

b.Directory structure 10

b.Directory structure 10

2.Background 11

2.Background 11

a.Landslide susceptibility mapping 12

a.Landslide susceptibility mapping 12

b.Bivariate statistical method 13

b.Bivariate statistical method 13

3.Slope failures leave discernible morphological or spectral features; most of them can be recognized, classified and mapped both in the field and through remote sensing. 15

4.The morphological signature of a landslide depends on the type (i.e. rock fall, slide, flow, etc.) and the rate of motion of the mass movement. 15

5.Landslides do not occur randomly or by chance. Slope failure is controlled by mechanical laws that can be determined empirically, statistically or in a deterministic fashion. 15

6.The geological principle of uniformitarianism infers that “the past and present are keys to the future.” I.e. landslides are more likely to occur under the conditions that led to past instability. 15

1.Weights are calculated using the following hazard index method and described further in Table 2. (van Westen, 1997): 15

7.Landslide areas are compared with parameter maps to isolate landslide areas in each parameter class. The areas of each individual parameter class are recorded, as well as the areas of the landslides within them. The total area of the area of interest and the total area of landslides in the area of interest are also calculated. Landslide density values for each parameter class and the total landslide density for the area of interest are calculated. The density ratio for each parameter is calculated and the natural log of this value is calculated. This produces weightings for each parameter class. 15

8.To create the weighting maps for each data type, a new file must be created for each data type, and each parameter value is replaced with the weighting that was calculated. 17

9.To produce the final map, all individual weighting maps for each data type are summed together, to find the final susceptibility values for the area. 17

10.Data Inputs 19

10.Data Inputs 19

a.Digital elevations models: DTM versus DSM 20

a.Digital elevations models: DTM versus DSM 20

b.Remote sensing 21

b.Remote sensing 21

11.Building a landslide inventory 24

11.Building a landslide inventory 24

a.Using satellite imagery data 25

a.Using satellite imagery data 25

b.Normalised Difference Vegetation Index (NVDI) 28

b.Normalised Difference Vegetation Index (NVDI) 28

12.Quantum GIS (QGIS) 30

12.Quantum GIS (QGIS) 30

a.Downloading and installing QGIS 31

a.Downloading and installing QGIS 31

b.File extensions adopted in this manual 32

b.File extensions adopted in this manual 32

13.Landsat Data 34

13.Landsat Data 34

a.Downloading Landsat data 35

a.Downloading Landsat data 35

1.Select Decimal under the Coordinates tab. 35

14.Now select Add Coordinate 35

15.Type Latitude: -6.05101 35

16.Type Longitude: 145.021 35

17.Select the Date Range tab 35

18.Search from 02/23/2008 (US date format) until the present day. 35

19.Select Data Sets. This will take you to another window. 37

20.Click on the plus sign next to Landsat Archive to expand the list of Landsat satellites. 37

21.Check the box next to L8 OLI/TIRS (for different time periods, different Landsat satellites should be used). 37

22.Now click Results. 37

23.Select Download Options on the LC80980642014088LGN00 entry 39

24.The Download Options window will appear. 39

25.Select Level 1 GeoTIFF Data Product (969.8 MB) 39

26.Select Download Option button. A Download Scene window will appear. 39

27.Select Download and save the LC80980642014088LGN00.tar.gz file to the Training/Inventory/Landsat folder. 39

a.Unzipping Landsat data 40

a.Unzipping Landsat data 40

1.Navigate to the folder in which you saved the Landsat .tar.gz file (Training/Inventory/Landsat/LC80980642014088LGN00_B1.tar.gz). 42

28.Select the .tar.gz file 42

29.Select Extract to extract it into the Training/Inventory/Landsat folder. 42

30.Navigate to the Training/Inventory/Landsat folder again in 7-zip. The file will now be a .tar file. This requires another level of extraction. 42

31.Select the .tar file and click the Extract button again. The file will now contain all the bands of the Landsat image. 42

32.The .tar and .tar.gz files are no longer needed so they can now be deleted. 42

a.Decoding Landsat file names 43

a.Decoding Landsat file names 43

b.Useful website for Landsat data 44

b.Useful website for Landsat data 44

33.Creating a landslide inventory 46

33.Creating a landslide inventory 46

a.Loading and viewing a DEM 47

a.Loading and viewing a DEM 47

1.Open QGIS by double clicking on the QGIS Desktop 2.2.0 icon on the desktop. 47

2.To load the raster DEM select Layer 47

3.Select add Raster Layer. This opens a window. If QGIS has not automatically gone to the base_data folder, navigate to it. 47

4.Select the file png_dem.tif 47

5.Select Open. Your DEM should load. 47

6.Select Project 47

7.Select Save As and navigate to the base_data folder. 47

8.Name this file as base_data.qgs. 47

9.Select Save. 47

b.Reprojecting a raster 48

b.Reprojecting a raster 48

1.Select Raster 48

34.Select Projections 48

35.Select Warp (Reproject) and fill in the parameters as indicated in (Table 7.). 48

36.gdalwarp -overwrite -s_srs EPSG:4326 -t_srs EPSG:32755 -r cubic -of GTiff C:\Training\base_data\png_dem.tif C:/Training/base_data/png_dem_UTM.tif 50

37.Select Ok. The reprojected DEM should appear on the screen. 50

a.Creating a hillshade 51

a.Creating a hillshade 51

1.Confirm that the reprojected DEM (png_dem_UTM.tif) is still loaded 51

38.Select Raster 51

39.Select Analysis 51

40.Select DEM (Terrain models) and fill in the parameters as indicated in (Table 7.). 51

41.gdaldem hillshade C:/Training/base_data/png_dem_UTM.tif C:/Training/base_data/hillshade.tif -z 1.0 -s 1.0 -az 35.0 -alt 45.0 -of GTiff 51

42.Select Ok. The hillshade will now appear on the screen. 51

a.Loading and viewing Landsat data 52

a.Loading and viewing Landsat data 52

1.Select Raster 52

43.Select Miscellaneous 52

44.Select Merge. This opens a Merge window. 52

45.Click Select… (next to Input files) to open a Select files to merge window 52

46.Navigate to Inventory 54

47.Select Landsat 54

48.Select LC80980642014088LGN00 to select the files (by holding ctrl down while selecting them) 54

49.Select Open on the Select files to merge window. 54

50.Click Select… next to Output file 54

51.Navigate to Inventory 54

52.Select Landsat 54

53.Select LC80980642014088LGN00 54

54.Save the file as LC80980642014088LGN00_RGB 54

55.Select the checkbox for Layer stack 54

56.Select the checkbox for Load onto canvas when finished 54

An example Merge window is shown in Figure 7.. 54

57.Select Ok. 54

58.When the layer has loaded, right click on the layer in the Layers sidebar and from the drop down menu select Properties. 54

59.A Layer Properties window will appear 54

60.Select the Style tab 54

61.In the Band Rendering box select Multiband Colour from the dropdown list next to Render type. 54

62.Then match the Red Band with Band 4, the Green band with Band 3 and the Blue band with Band 2 from the respective drop down menus. 54

63.Select Apply. The image on the screen should now appear in true colour 54

64.To make the image brighter with more contrast select the Colour rendering box 54

65.Change the brightness to 145 54

66.Change the contrast to 70 54

67.Select Apply. The image is now ready for viewing. 54

a.Calculating NDVI ratios 57

a.Calculating NDVI ratios 57

1.Select Layer 57

68.Select Add Raster Layer 57

69.An Open a GDAL Supported Raster Data Source window will appear. 57

70.Navigate to the folder: Training/Inventory/Landsat/ LC80980642014088LGN00 57

71.Load bands 4 (LC80980642014088LGN00_B4.tif) and 5 (LC80980642014088LGN00_B5.tif) of Landsat data by selecting the files and clicking Open. 57

72.Select Raster 57

73.Select Raster Calculator 57

74.In the Raster calculator expression box write the expression: 59

75.Navigate to the Training/Inventory/Landsat/LC80980642014088LGN00 folder and name it LC80980642014088LGN00_NDVI.tif 59

76.Select Ok. 59

77.A new file named LC80980642014088LGN00_NDVI.tif will appear in the Layers window. 61

78.Repeat this for the rest of the Landsat imagery in the Training/Inventory/Landsat folder. 61

a.Making a raster layer transparent 63

a.Making a raster layer transparent 63

1.Double click on the layer (in the sidebar) which you wish to make transparent. In this case click on one of the Landsat files. This will take you to Properties. 63

79.Select the Transparency tab 63

80.In the Global Transparency box slide the slide bar to the percentage of transparency required (30% is recommended). 63

81.Press Apply and then Ok. 63

a.Creating the landslide polygons 64

a.Creating the landslide polygons 64

1.Select Layer 64

82.Select New 64

83.Select New Shapefile Layer. A window will pop up (Figure 7.). 64

84.In the Type box, select Polygon. 64

85.Specify CRS [Coordinate Reference System] (in this instance it was EPSG:32755 - WGS 84/UTM zone 55S). 64

86.To add a Date, fill in the Name field in the New attribute box with the word Date. For Type, click the drop down menu and select Date. 64

87.Click Add to attributes list. 64

88.To add a Classification/Type field, type Classification/Type in the Name field in the New attribute box. For Type, select Text data from the drop down menu. 64

89.Click Add to attributes list. 64

90.To add a Population Displaced field, type Population Displaced in the Name field in the New attribute box. For Type, select Whole number from the drop down menu. 64

91.Click Add to attributes list. 64

92.Press OK. A Save As window will pop up. 66

93.Name the file (e.g. landslide_12.shp) & choose a directory to save it in (e.g. Training/Inventory/Landslide). The layer will now appear in the Layers sidebar. 66

94.Select the layer in the layers window 66

95.Select Layer 66

96.Select Toggle Editing. The Editing toolbar will now be activated. 66

97.Locate the Porok landslide at Easting: 281760 Northing: 9332335. Here it is displayed in NDVI and true colour (Figure 7.). 66

98.Make sure that the layer (landslide_12) is still highlighted in the Layers window. 68

99.Click Add Feature in the Editing toolbar. 68

100.Now use the mouse to trace the edge of the landslide feature to outline it (click to add a point, click again to add net point). 68

101.Right click when you finish tracing the feature. A box will appear asking you to fill in the attributes. 68

102.Give the feature a unique landslide ID, date, classification/type and population displaced if the information is known. 68

103.If the area needs to be reshaped use the Node tool in the editing toolbar. 68

104.Save by clicking the Save Layer Edits button on the Editing toolbar (Important – the outline will not be saved if you don’t click the Save Layer Edits button). 68

105.When finished, deselect the Toggle Editing feature. 68

106.If you make a mistake and wish to delete a polygon or a node, go to Select Single Feature button, and then press the Delete Selected button in the editing toolbar. 68

107.To change the colour of the polygons, double click on the layer in the Layers sidebar to bring up the Layer Properties window. 68

108.Click the Style tab and choose a style or colour for the polygon to be. 68

109.To put a “hole” in the polygon (e.g. when a landslide bifurcates and then joins again) click Add Ring either under Edit in the top bar of QGIS, or in the toolbar. Then point and click to outline the area. 69

a.Merging the landslide shapefiles 71

a.Merging the landslide shapefiles 71

1.Confirm that all landslide shapefiles are in the same directory, with no other non-landslide files in that directory. 71

110.Select Vector 71

111.Select Data Management Tools 71

112.Select Merge Shapefiles to one 71

113.A Merge Shapefiles window will appear. Add parameters as indicated in Table 7. and Figure 7.. 71

114.Press OK. The merged file will now appear on the screen. 73

115.Select Vector 73

116.Select Geoprocessing 73

117.Select Union tool to merge the shapefiles one at a time. 73

To dissolve any intersections between merged files: 73

118.Select Vector 73

119.Select Geoprocessing Tools 73

120.Select Dissolve. 73

121.Processing input data 75

121.Processing input data 75

a.Calculating slope angle 76

a.Calculating slope angle 76

1.Open a new QGIS session 76

2.Save this session as processing.qgis in the processing folder. 76

3.Select Raster 76

4.Select Analysis 76

5.Select DEM (Terrain models) and fill in the parameters as indicated in Table 8. and Figure 8.. 76

122.gdaldem slope C:/Training/base_data/png_dem_UTM.tif C:/Training/base_data/slpang.tif -s 1.0 -of GTiff 78

123.Press OK. 78

a.Calculating slope aspect 79

a.Calculating slope aspect 79

1.Select Raster 79

124.Select Analysis 79

125.Select DEM (Terrain models) and fill in the parameters as indicated in Table 8.. 79

126.gdaldem aspect C:/Training/base_data/png_dem_UTM.tif C:/Training/base_data/slpasp.tif -zero_for_flat -of GTiff 81

127.Press OK. 81

a.Reprojecting a vector 82

a.Reprojecting a vector 82

127.a.1Rainfall 83

1.Select Layer 83

128.Select Add Vector Layer (Figure 8.) 83

129.Add the file rainfall_sim_region.shp from the folder base_data. 83

130.Right click on the rainfall_sim_region file in the Layers window 83

131.Click Save As and fill in the parameters as indicated in Table 8.. 83

132.Repeat this for the geology_sim_region.shp file, renaming it geology_sim_UTM.tif. 83

a.Converting from vector to raster 85

a.Converting from vector to raster 85

132.a.1Rainfall 86

1.Select Raster 86

133.Select Conversion 86

134.Select Rasterize (Vector to Raster) and fill in the parameters as indicated in Table 8.. 86

135.gdal_rasterize -a RAINFALL -tr 4.97722 4.97722 -l rainfall_sim_UTM C:\Training\base_data\rainfall_sim_UTM.shp C:/Training/base_data/rainfall_sim_UTM.tif 86

136.Click the edit button 86

137.Insert the red text into the script already in the box: 86

138.Press OK. 86

138.a.1Geology 88

1.Select Raster 88

139.Select Conversion 88

140.Select Rasterize (Vector to Raster) and fill in the parameters as indicated in Table 8.. 88

141.gdal_rasterize -a ROCKTYPE -tr 4.97722 4.97722 -l geology_sim_UTM C:\Training\base_data\geology_sim_UTM.shp C:/Training/base_data/geology_sim_UTM.tif 88

142.Click the edit button 88

143.To ensure the new file is converted to eight bit unsigned integer (Byte) format. 88

144.Insert the red text into the script already in the box:
gdal_rasterize -ot Byte -a ROCK TYPE -tr 4.97722 4.97722 -l geology_sim_UTM C:\Training\base_data\geology_sim_UTM.shp C:/Training/base_data/geology_sim_UTM.tif 88

145.Press OK. 88

145.a.1Changing the appearance of rasters 89

1.Right click on the file in the Layers sidebar 89

146.Select Properties (a Layer Properties window will appear) 89

147.Select the Style tab 89

148.Select Min / max in the Load min/max values box in the corner of the Layer Properties window 89

149.Select Load 89

150.Select Apply 89

151.To change the colour of the raster from grayscale to blue: 91

152.Check the box next to Colorize in the Colour rendering box 91

153.Select the coloured box on the right hand side of Colorize. A Select Colour window with a rainbow of colours will appear. 91

154.Select the colour that you wish to use (e.g. blue) 91

155.Select OK. 91

156.Select the drop down menu next to Colour gradient in the Band rendering box. 91

157.Select White to black 91

158.Click Apply 91

159.Repeat the geology_sim_UTM raster file 93

a.Clipping rasters to the study area 94

a.Clipping rasters to the study area 94

159.a.1Slope aspect 95

1.Select Raster 95

160.Select Extraction 95

161.Select Clipper and fill in the parameters as indicated in Table 8.. 95

162.Press OK 97

162.a.1Slope angle 98

1.Select Raster 98

163.Select Extraction 98

164.Select Clipper and fill in the parameters as indicated in Table 8.. 98

165.Press OK 98

165.a.1Creating a polygon of the DEM area 99

1.Select Vector 99

166.Select Research Tools 99

167.Select Polygon from layer extent and fill in the parameters as indicated in Table 8.. 99

167.a.1Rainfall 102

1.Select Raster 102

168.Select Extraction 102

169.Select Clipper and fill in the parameters as indicated in Table 8.. 102

170.Press OK. 102

170.a.1Geology 103

1.Select Raster 103

171.Select Extraction 103

172.Select Clipper and fill in the parameters as indicated in Table 8.. 103

173.Press OK. 105

a.Reclassifying rasters into parameter classes using r.reclass 106

a.Reclassifying rasters into parameter classes using r.reclass 106

173.a.1Slope angle 107

1.Select Processing 107

174.Select Toolbox. 107

175.Type r.reclass in the search bar 107

176.Alternatively, expand the GRASS commands menu and scroll down until you find the r.reclass tool. 107

177.Press OK. 109

178.Select Layer 109

179.Select Add Raster Layer 109

180.Browse to the file that you just created in (C:\Training\processing\slpang_study_area.tif) 109

181.Click Open. 109

182.Right click on the slpangcl file that has just appeared in the Layers sidebar, 109

183.Select Properties from the drop-down menu. A Layer Properties window will appear. 109

184.Click on the Style tab. 109

185.Select Min/Max in the Load min/max values box 109

186.Click Load 109

187.Click Apply and OK. 109

187.a.1Slope aspect 110

1.Select Processing 112

188.Select Toolbox 112

189.Select r.reclass and fill in the parameters as indicated in Table 8.. 112

189.a.1Rainfall 113

189.a.2Geology 115

b.Calculating weightings 116

b.Calculating weightings 116

189.b.1Calculating the total area of each parameter class 117

1.Select Processing 117

190.Select Toolbox 117

191.Select GRASS commands 117

192.Select Raster 117

193.Select r.report and fill in the parameters indicated in Table 8.. 117

194.Select Run. 119

195.Repeat this process for slpasp_study_area.tif, rf_study_area.tif and geo_study_area.tif. 119

195.a.1Clipping rasters to the area of the landslide inventory 120

1.Overlay the merged landslide layer and the parameter that you wish to calculate (this example uses slpangcl.tif). 120

196.Select Raster 120

197.Select Extraction 120

198.Select Clipper and fill in the parameters as indicated in Table 8. and Figure 8.. 120

198.a.1Calculating the area of landslides for each parameter 122

1.Select Processing 122

1.Select Toolbox 122

2.Select GRASS commands 122

3.Select Raster 122

4.Select r.report and fill in the parameters indicated in Table 8.. 122

199.Select Run. A window will appear (Figure 8.) 122

200.Repeat this step for slpasp_LS.tif, rf_LS.tif and geo_LS.tif. 122

200.a.1Using the weighting spreadsheet to calculate ratios and weightings 124

b.Applying the weightings to parameter classes 125

b.Applying the weightings to parameter classes 125

200.b.1Slope angle 126

1.Select Processing 126

5.Select Toolbox 126

6.Select r.reclass and fill in the parameters as indicated in Table 8.. 126

201.Press OK. 126

201.a.1Slope aspect 127

1.Select Processing 127

7.Select Toolbox 127

202.Press OK. 129

202.a.1Rainfall 130

1.Select Processing 130

8.Select Toolbox 130

9.Select r.reclass and fill in the parameters as indicated in Table 8.. 130

203.Press OK. 130

203.a.1Geology 131

1.Select Processing 131

10.Select Toolbox 131

11.Select r.reclass and fill in the parameters as indicated in Table 8.. 131

204.Press OK. 133

a.Adding final weightings together 134

a.Adding final weightings together 134

1.Select Layer 134

205.Select Add Raster Layer 134

206.Select angwt.tif and aspwt.tif to open files 134

207.Select Raster 134

208.Select Raster Calculator 134

209.In the Raster calculator expression box write the expression: 134

210.In the Result layer box, select the ‘. . . ‘button next to the Output layer field, navigate to the weighting folder and name it allwt.tif. 134

211.Click OK. 134

a.Composing a map 135

a.Composing a map 135

211.a.1Composer Manager 136

1.Select Project 136

2.Select Composer Manager. A Composer manager window will appear. 136

3.Set drop down menu to Empty Composer 136

4.Select Add. A Composer title window will appear. 136

5.Fill in the blank field and name this project Chimbu. 136

6.Click OK. 136

7.Click Show. A Chimbu window will now appear. 136

8.To navigate to this file again select Project 136

9.Select Print Composers 136

212.Select Chimbu 136

212.a.1Basic map composition 137

1.Select the values in the Composition tab in the side bar to the parameters indicated in Table 8.. 137

213.Select Layout 138

214.Select Add Map. While this is activated, click and drag a box on the blank page. The map will appear on the page. 138

215.Select Composer 138

216.Select Save project 138

216.a.1Adding a title 139

1.Select Layout 139

217.Select Add Label 139

218.Select the Item Properties tab in the sidebar. Text can be changed in the Main properties box. 139

218.a.1Adding and customising a legend 140

1.Select Layout 140

219.Select Add Legend 140

219.a.1Adding a logo 141

1.Select Layout 141

220.Select Add Image. 141

221.When you click on the page, a box will now appear. Move it to where you want it by clicking and dragging. You can also resize it. 143

222.On the Item properties tab, in the Main properties box click the … button that is next to the word Path. This will bring up a Select svg or image file window. 143

223.Navigate to the folder that the image file of the logo is in and press Open. 143

224.The logo will now appear. 143

224.a.1Adding a scalebar 144

1.Select Layout 144

225.Select Add scalebar. 144

226.When you click on the page, a scalebar will now appear. Move it to where you want it by clicking and dragging. You can also resize it. 144

227.If you want to change the unit of measurement, go to the Item properties tab, and go to the drop down menu in the Units box. 144

228.If you want to change the style of the scalebar, go to the drop down menu next to Style in the Main properties box. 144

228.a.1Exporting a map 145

1.Select Composer 145

229.Select Export as Image or Export as PDF (depending on whether you want to save it as an image or a PDF). A window will pop up. 145

230.Navigate to the folder you wish to save it in, name it and click Save. 145

231.Quality management 147

231.Quality management 147

1.Select Vector 147

2.Select Research 147

3.Select Random Selection 147

4.Select the Input Vector Layer LS_UTM 147

5.Select the Percentage of Features 25%. 147

6.Select Layer 147

7.Select Save Selection as Vector File, naming this file as Sample2. 147

8.Open the attribute table for the LS_UTM file and invert the selection. 147

9.Select Layer 147

10.Select Save Selection as Vector File. 147

References 149

References 149

232.QGIS Basics 149

232.QGIS Basics 149

a.Loading a vector dataset 150

a.Loading a vector dataset 150

1.Select Layer 150

2.Select Add Vector Layer 150

3.Select Browse to navigate to the file (Appendix Figure A.). 150

4.Click Open. 150

b.Reprojecting a layer 151

b.Reprojecting a layer 151

232.b.1Raster 152

233.Select Raster 152

234.Select Projections 152

235.Select Warp(Reproject) 152

236.Fill in required parameters 152

237.Press OK. 152

237.a.1Vector 153

238.Select Vector 153

239.Select Data Management Tools 153

240.Select Define current projection 153

241.Fill in required parameters 153

242.Press OK. 153

a.Loading a colour scheme 154

a.Loading a colour scheme 154

243.Double click on the layer e.g. DEM (in the layers window) to bring up the Properties window. 154

244.Select Load Style and locate the file Wikicarto_2.0.qml. 154

245.Select Open and Apply. 154

246.Press OK. 154

a.Useful tips and tools 155

a.Useful tips and tools 155

247.Select the file in the Layers sidebar 155

248.Select the pixel or feature you wish to identify in the main window. A window will pop up with information about the feature or pixel. 155

249.Double click on a layer in the Layers sidebar to bring up the Layer Properties window. 155

250.To view the attribute table of a vector layer in the Layers sidebar, right click on the layer to bring up a drop down menu, and then click on Open Attribute Table. 155