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Table 2 Frequency Ratios of Landslide Causal Factors

From: An investigation of the characteristics, causes, and consequences of June 13, 2017, landslides in Rangamati District Bangladesh

Causal Factors

Classes

Area (%),

\( \frac{{\boldsymbol{A}}_{\boldsymbol{ij}}}{{\boldsymbol{A}}_{\boldsymbol{total}}} \)

Landslides (%),

\( \frac{{\boldsymbol{N}}_{\boldsymbol{ij}}}{{\boldsymbol{N}}_{\boldsymbol{total}}} \)

FR,

\( \frac{{\boldsymbol{N}}_{\boldsymbol{ij}}/{\boldsymbol{N}}_{\boldsymbol{total}}}{{\boldsymbol{A}}_{\boldsymbol{ij}}/{\boldsymbol{A}}_{\boldsymbol{total}}} \)

Aspect

Flat

0.00

0.00

0.00

North

17.80

5.73

0.32

Northeast

11.12

12.50

1.12

East

11.17

17.19

1.54

Southeast

10.22

12.50

1.22

South

10.63

15.10

1.42

Southwest

12.37

16.67

1.35

West

11.79

6.25

0.53

Northwest

10.33

10.94

1.06

North

4.58

3.13

0.68

Elevation (m)

0–50

47.64

23.96

0.50

50–100

34.34

50.00

1.46

100–170

10.71

21.88

2.04

170–274

5.51

4.17

0.76

> 274

1.81

0.00

0.00

Slope (°)

0–5

25.71

8.85

0.34

5–10

30.28

25.00

0.83

10–16

24.32

28.13

1.16

16–24

14.91

28.13

1.89

24–59

4.78

9.90

2.07

SPI

2–5

22.19

15.63

0.70

5–7

38.22

44.79

1.17

7–8

28.49

32.29

1.13

8–11

8.69

6.77

0.78

> 11

2.43

0.52

0.21

TWI

6–10

48.98

68.23

1.39

10–12

26.20

25.52

0.97

12–15

12.36

5.21

0.42

15–19

11.41

1.04

0.09

> 19

1.05

0.00

0.00

Plan Curvature

Convex

41.09

43.75

1.06

Concave

50.52

42.53

1.19

Flat

16.38

5.73

0.35

Profile Curvature

Convex

41.12

45.83

1.11

Concave

44.71

50.00

1.12

Flat

14.17

4.17

0.29

NDVI

−0.1-0.1

17.99

1.59

0.09

0.1–0.2

6.98

8.47

1.21

0.2–0.3

20.42

36.51

1.79

0.3–0.4

31.87

34.92

1.10

0.4–0.5

22.74

18.52

0.81

Distance to Road Network (m)

0–500

10.50

72.49

6.90

500–1000

17.01

14.81

0.87

1000-2000

23.04

8.99

0.39

2000-6000

42.82

3.70

0.09

> 6000

6.63

0.00

0.00

Distance to Drainage Network (m)

0–500

8.01

12.70

1.59

500–1000

7.99

16.40

2.05

1000-2000

16.14

21.16

1.31

2000-5000

50.86

34.92

0.69

> 5000

17.01

14.81

0.87

Distance to Fault Lines (m)

0–500

1.88

4.76

2.54

500–1000

6.88

5.29

0.77

1000-5000

45.27

66.14

1.46

5000-10,000

38.65

23.81

0.62

> 10,000

7.33

0.00

0.00

Rainfall (mm)

2370-2450

32.16

11.9

0.37

2450-2525

24.40

63.69

2.61

2525-2607

21.11

15.41

0.73

2607-2707

9.78

9.00

0.92

> 2707

12.55

0.00

0.00

Geology

Dihing and Dupi Tila Formation

4.65

19.07

4.10

Boka Bil Formation

28.92

30.41

1.05

Bhuban Formation

8.97

16.49

1.84

Tipam Sandstone

12.41

27.84

2.24

Valley Alluvium and Colluvium

0.46

0.00

0.00

Dupi Tile Formation

14.73

3.61

0.25

Lake

26.46

0.00

0.00

Girujan Clay

3.41

2.58

0.76

Land use/Landcover

Vegetation

73.60

70.26

0.95

Waterbodies

18.40

0.00

0.00

Bare land

5.38

14.87

2.77

Built up

2.62

14.88

5.67

Land use Change

Water-Vegetation

5.31

2.05

0.39

Water- Bare Land

0.70

0.51

0.73

Water-Built up

0.25

0.51

2.02

Vegetation-Water

0.00

0.00

0.00

Vegetation-Bare land

3.54

12.82

3.62

Vegetation-Built up

1.74

9.23

5.31

Built up- Vegetation

0.81

1.54

1.91

Built up-Bare land

0.23

0.51

2.20

Bare land-Vegetation

2.09

7.18

8.65

Bare land- Built up

0.45

3.59

3.44

No Change

84.88

62.06

0.73