Landslide susceptibility modelling and risk assessment in chittagong city

Presentation of Under Graduate Thesis
Department of Urban and Regional planning
Khulna University of Engineering & Technology

Landslide Susceptibility Modelling and Risk
Assessment in Chittagong City
Supervised By:
Showmitra Kumar Sarkar
Lecturer
Prepared By:
Md. Mehedi Hasan Khan
Roll No. 1317027
Provakar Chowdhury
Roll No. 1217024
URP 4000
Project & Thesis
Examine By:
Dr. Md. Mustafa Saroar
Professor

Acknowledgement
Firstly, all praises belong to the Almighty Allah, the most gracious and merciful to all the living beings, who has given us the strength and
composure to finish the task within the scheduled time.
We express our sincerest gratitude to Mr. Showmitra Kumar Sarkar, our undergraduate thesis supervisor and Lecturer, Department of
Urban and Regional Planning, KUET, for his patient Guidance and understanding during the thesis program. He provided us with a large
amount of data source and satellite imageries for the completion of the thesis. We would like to thank Mr. Esraz-UL-Zannat, Assistant
professor of the Department of Urban and Regional Planning, KUET for his continuous help and support during the thesis. Also, we would
like to thank Dr. Md. Mustafa Saroar, Head, Department of Urban and regional Planning, KUET for his supervision as external of this
thesis. He provide some valuable literature about landslide susceptibility and risk assessment. We would like to give our appreciation to
Md. Mokhlesur Rahman, Assistant professor, Department of Urban and Regional Planning, KUET for his priceless advice during the pre-
defense.
Thanks to all of our friends who always supported us during the thesis. I would like to thank Mahinur Rahman, Sharfan Upal and Sajnin
Tansim for giving me some valuable suggestion during my questioner preparation. Also, I would like to thanks my roommates Suddha
Ahmed, Mahinur Rahman and Sabbir Hossain for keep the room ambience useful for Study.

Landslide, one of the most occurring geological
hazards in the world
In Bangladesh 82% flat land and 18% hilly land
Hilly region of Bangladesh developed in tertiary age
CMA highly vulnerable to landslide
30 riskily hill in CMA
Physical damage, Economic and Environmental
losses
Background

Objectives
To examine the existing environmental scenarios associated to landslide
of the study area
To investigate the landslide susceptibility and risk of study area

Limitation
× Ward boundary is used as a smallest unit for vulnerability assessment
× Only available 9 indicators, more ara related (i.e. thunder strome is not
considered)
× Susceptibility does not consider magnitude of the expected landslide
× Secondary spatial data which is quite old

Desk Review
Methodology
Factors Fixation
Study Area Selection
Data Collection
1. DEM & Slope
2. Land Use and Land Cover
3. Rainfall
4. Geology
5. Distance from Natural drain
& Stream, Road and Man-
made structure
6. Field Survey
Present Scenario Analysis Data Preparation
Susceptibility Map Preparation
Validation
Choosing Most Accurate Model
Risk Mapping

Study Area
 Chittagong City Corporation area
- 41 wards
 5 wards ( 8,9,13,14,15) selected
 67% landslides within this area
 Total area - 4101.49 acres
Study Area Map

Indicators
Factors Functional Relation
Slop
Probability of landslide occurrence increase with slop (most
occur at 10-40°)
DEM Probability of landslide occurrence increase with elevation
Soil Moisture High moisture content in soil, lead to Landslide
NDVI Lower NDVI have promote Landslides
Land Use Land Cover
Removal of vegetation cover tends to promote the
occurrence of landslide
Rainfall Landslide probability increase with rainfall
Distance From Stream Nearby stream, landslides frequency is higher
Distance From Road Nearby road and railway, landslides frequency is higher
Distance From Drain Nearby drain, landslides frequency is higher
Factors Affecting Landslide
Source: Highland and Bobrowsky, 2008; Marrapu and Jakka, 2014; Chen and Huang, 2012; Pineda, Casasnovas and Viloria, 2016; F. Karsli, et al. ,
2009; Shahabi and Hashim, 2015; Ahmed, Rahman, et al., 2014; Sarker and Rashid, 2013
Analysis with Methodology (Cont.….)

Present Scenario Analysis
Landslide Inventory Map
21%
11%
26%
34%
8%
Bagmoniram (W-15) Lalkhan Bazar (W-14) North Pahartali (W-9)
Pahartali (W-13) Sulakbahar (W-8)
 38 landslides
 GPS logger
 Information on Extent, Vegetation
types, Number of houses and
population affected by Landslides
Ward wise Percentage of Past Landslides event Landslide Inventory Map

Landcover Mapping
 Landsat 7 ETM+ imagery, 2017
 Maximum Likelihood Supervised
Classiﬁcation
 Kappa Coefficient is .73>.7 so,
classification is substantial agreement
Ward wise Percentage of Past Landslides event Landcover Map
29%
55%
16%
0%
Buildup Area Vegetation Bare Soil Water Body

NDVI
2.1
5.3
19.7
31.4
64.6
62.1
54.0
40.5
33.4
32.5
26.3
28.2
-10.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
NDVI_02 NDVI_07 NDVI_12 NDVI_17
Percentage
Buildup Low dense
High dense Linear (Buildup)
Linear (Low dense) Linear (High dense)
Linear (High dense)
 NDVI For 2002, 2007, 2012 and 2017
 Buildup area – Increasing Trendline
 Forest Cover – Decreasing Trendline
NDVI for different YearsLand Use Changes

Precipitation
 Daily precipitation data of 50
years (1963–2013)
 Average rainfall of study area
is 2700 to 2850 mm.
 74% landslide occurs in 2723
to 2808 mm
 8 precipitation indices
calculated by R
Precipitation Maps of Study Area

Precipitation Indicators Analysis with Methodology (Cont.….)

Other Factors Analysis with Methodology (Cont.….)
DEM
 ASTER data
 Range 5 m to 72m
 76% past landslide occurs at 20-40m DEM
 ASTER data
 Range 0˚-29˚
 60% past landslide occurs at 3˚-10˚
Slope

Distance to Stream
 Euclidean Distance tools of ArcGIS 10.4.
 Maximum distance - 1250 m.
 Euclidean Distance tools of ArcGIS 10.4
 Maximum distance - 870.057 m
 Within a distance of 0-200m- 82% Past LS
Distance to Drain

Distance to Road
 Maximum distance - 765 m
 Road density lower in North Pahartali
 Within 0-200m from road- all past LS
 Silty sand more vulnerable to landslide
(Only 18% of area but 34% landslide occur)
Soil Types

Susceptibility Map Preparation Analysis with Methodology (Cont.….)
1. Analytical Hierarchy Procedure
2. Weighted Linear Combination Method
3. Logistic Regression Method
1. Combination 1 (WLC_1)
1. Logistic regression by considering only statistically
correlated variable (LR_1)
2. Logistic regression by considering all variables (LR_2)
(AHP)
(WLC)
(LR)
3 Techniques for Susceptibility Map Preparation

Weights Analysis with Methodology (Cont.….)
1. Elevation (m)
Criteria 0-10 10--30 30-50 50-72
0-10 1 0.333333 0.2 0.5
10--30 3 1 1 0.5
30-50 5 1 1 0.5
50-72 2 2 2 1
Eigen values 0.09976 0.236756 0.283539 0.379945
Consistency Ratio 0.096775
Principal Eigen values 4.264031
2. Landcover
Critiria Buildup Area Vegetation Waterbody Bare Soil
Buildup Area 1 4 5 8
Vegetation 0.25 1 4 4
Waterbody 0.2 0.25 1 2
Bare Soil 0.125 0.25 0.5 1
Eigen values 0.605123 0.24207 0.094587 0.058221
Consistency Ratio (CR) 0.055318
Principal eigen value 4.150925
3. NDVI
Criteria 0-.1 .1-.3 .3-.6 .6-.75
0-.1 1 2 3 3
.1-.3 0.5 1 1 3
.3-.6 0.333333 1 1 3
.6-.75 0.333333 0.333333 0.333333 1
Eigen values 0.451977 0.234867 0.216575 0.096581
Pairwise Comparison Matrix for Determining Eigen Value of Each Sub Criteria
 All CR < .1
 Consistent

4. Permeability (cm/hr)
Criteria 0-.1 .1-.2 .2-.3 .3-.4
0-.1 1 0.142857 0.2 0.142857
.1-.2 7 1 2 0.25
.2-.3 5 0.5 1 0.333333
.3-.4 7 4 3 1
Eigen values 0.045122 0.241719 0.163904 0.549254
5. Slope (Degree)
Criteria 0-2 2 to 6 6 to 10 10 to 30
0-2 1 0.125 0.142857 0.333333
2 to 6 8 1 0.5 5
6 to 10 7 2 1 2
10 to 30 3 0.2 0.5 1
Eigen values 0.049757 0.463269 0.351414 0.13556
6. Distance to Road(m)
Criteria 0-200 200-400 400-550 550-770
0-200 1 4 6 9
200-400 0.25 1 4 3
400-550 0.166667 0.25 1 2
550-770 0.111111 0.333333 0.5 1
Eigen values 0.628059 0.222159 0.089581 0.060202
 All CR < .1
 Consistent

7. Distance to Stream(m)
Criteria 0-200 200-450 450-700 700-1250
0-200 1 2 3 7
200-450 0.5 1 5 9
450-700 0.333333 0.2 1 5
700-1250 0.142857 0.111111 0.2 1
Eigen values 0.444508 0.38317 0.131627 0.040695
8. Distance to Drain (m)
Criteria 0-200 200-450 450-650 650-875
0-200 1 0.5 0.333333 0.2
200-450 2 1 0.333333 0.25
450-650 3 3 1 0.5
650-875 5 4 2 1
Eigen values 0.085088 0.127959 0.290341 0.496612
Consistency Ratio(CR) 0.020745
9. Precipitation (mm)
Criteria 2700-2736 2736-2772 2722-2808 2808-2850
2700-2736 1 0.333333 0.2 0.142857
2736-2772 3 1 0.333333 0.2
2722-2808 5 3 1 0.333333
2808-2850 7 5 3 1
Eigen values 0.055284 0.117523 0.262229 0.564963
Consistency Ratio(CR) 0.042953
 All CR < .1
 Consistent

Pairwise Comparison Matrix for Determining Eigen Value of Main Criteria
 CR < .1
 Consistent
AHP priorities
Criteria Landcover NDVI Slop Elevation Precipitation
Soil
Permeability
Distance to
Road
Distance to
Stream
Distance to
Drain
Landcover 1.00 2.00 0.14 0.33 0.33 0.20 2.00 3.00 0.50
NDVI 0.50 1.00 0.20 2.00 0.50 0.33 2.00 3.00 0.33
Slop 7.00 5.00 1.00 5.00 3.00 2.00 5.00 7.00 3.00
Elevation 3.00 0.50 0.20 1.00 0.50 1.00 3.00 2.00 0.33
Precipitation 3.00 2.00 0.33 2.00 1.00 0.33 2.00 2.00 2.00
Soil Permeability 5.00 3.00 0.50 1.00 3.00 1.00 5.00 5.00 3.00
Distance to Road 0.50 0.50 0.20 0.33 0.50 0.20 1.00 2.00 0.33
Distance to Stream 0.33 0.33 0.14 0.50 0.50 0.20 0.50 1.00 0.20
Distance to Drain 2.00 3.00 0.33 3.00 0.50 0.33 3.00 5.00 1.00
Eigen values 0.05694 0.06568 0.29708 0.08267 0.11349 0.19754 0.03876 0.029782 0.11802
 Eigen value of each sub criteria is used in AHP and WLC Method
 Eigen value of each main criteria is used only in AHP

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
WLC_1
WLC_2
WLC_3
AHP
0.1
0.1
0.05
0.07
0.1
0.05
0.1
0.06
0.05
0.05
0.05
0.04
0.2
0.1
0.1
0.08
0.2
0.25
0.2
0.30
0.05
0.05
0.05
0.12
0.15
0.2
0.3
0.20
0.05
0.1
0.1
0.11
0.1
0.1
0.05
0.03
NDVI Landcover Distance to Road Elevation Slop
Distance to Drain Soil Permeability Precipitation Distance to Stream

LSM by AHP Analysis with Methodology (Cont.….)
Susceptibility Types Value %
Very Low Susceptibility 0-.01 0.06
Low Susceptibility .01-.25 7.06
Moderate Susceptibility .25-.5 25.16
High Susceptibility .5-1 67.73
Grand Total 100
 Pairwise matrix
 Saaty’s pairwise comparison
scale
 Consistency ratio - smaller than
.1
 Weighted sum
 Normalization
LSM by AHP
Area cover by susceptibility
level

 Use the eguine value of sub-
criteria calculate by AHP
 Use 1st combination of main
criterion
 Weighted sum
 Normalization
Grand Total 100
LSM by WLC
LSM by WLC_1
Area cover by susceptibility level

Grand Total 100
LSM by WLC
LSM by WLC_2
 Use 2nd combination of main
criterion
 Weighted sum
 Normalization

Grand Total 100
LSM by WLC
LSM by WLC_3
 Use 3rd combination of main
criterion
 Weighted sum
 Normalization

Correlations Analysis with Methodology (Cont.….)
Sample Size
25% stratiﬁed random.
Correlation Analysis:
Landslide
Landuse
Permeability
Slope
Rainfall
Elevation
Stream
Road
Drain
NDVI
Landslide
Pearson
Correlation
1 -.008 .119
**
.006 .150
**
.033
**
0.014˟˟-.04
**
-.048
**
-.013
Sig. (2-
tailed)
.479 .000 .603 .000 .003 .004 .000 .000 .233
N 7903 7903 7903 7903 7903 7903 7903 7903 7903 7903
 Multidisciplinary concept
 Many interrelated factors work behind landslide
 Very difficult to statistically analyze

Grand Total 100
Logit(landslide) = - 1033.760 +2.110*pemeability+.073*rainfall+.064*elevation-.027*Distance to
road+.010*distance to drain-.014*Distance to stream
Hosmer and Lemeshow
Test
Model Summary
Chi-square Sig. Nagelkerke R Square
5.345 .720 .774
LSM by LR (Only considering correlated variables)
Model Acceptancy
LSM by LR_1

Grand Total 100
Hosmer and Lemeshow
Test
Model Summary
Chi-square Sig. Nagelkerke R Square
5.835 .666 .776
Logit(landslide) = - 1037.977 -.073*landuse+2.082*pemeability-
.038*slope+.009*rainfall+.071*elevation+1.911*NDVI-.028*road-.010*drain-.014*stream
LSM by LR (Considering all Variables)
Model Acceptancy
LSM by LR_2

Validation of Models Analysis with Methodology (Cont.….)
Area Under the Curve
Test Result
Variable(s)
Area
Std.
Errora
Asymp
totic
Sig.b
Asymptotic
95%
Confidence
Interval
Lower
Bound
Upper
Bound
AHP .638 .052 .004 .536 .739
WLC_1 .748 .043 .000 .664 .831
WlC_2 .726 .045 .000 .637 .814
WLC_3 .770 .042 .000 .688 .852
LR_1 .804 .032 .000 .741 .867
LR_2 .847 .036 .000 .776 .917
Area Under ROC Curve
ROC Graph

Vulnerability Assessment Analysis with Methodology (Cont.….)
Indicator /Ward
Population
Density
Female
Adult
literacy
rate
Househol
d
Head Count Ratio
(Percentage)
SVI
Bagmoniram 0.38 0.00 0.00 0.00 0.68 0.21
Lalkhan Bazar 1.00 0.27 0.70 0.34 0.74 0.61
Pahartali 0.24 0.36 1.00 0.32 0.89 0.56
North Pahartali 0.00 0.35 0.71 0.41 1.00 0.49
Sulakbahar 0.23 1.00 0.24 1.00 0.00 0.49
Indicator
/Ward
Avg.
Income
level
Unemployme
nt Rate
EVI
Bagmoniram 1 1 1
Lalkhan Bazar 0.5 0 0.25
Pahartali 0.75 0.12 0.44
North
Pahartali
1 0.70
0.85
Indicator
/Ward
Vegetatio
n (%)
Build Up
Area (%)
En_VI
Bagmoniram 0.45 0.56 0.50
Lalkhan
Bazar
0.68 0.67 0.68
Pahartali 0.61 0.69 0.65
North
Pahartali
0 0 0
Social Vulnerability
Index
Economic Vulnerability Index Environmental Vulnerability Index
Source: Ward Councilor office, 2018
Source: Ward Councilor office, 2018 Source: Landsat 7 ETM+, 2018

Indicator /Ward
Katcha building
(%)
Katcha Road (%)
Physical
Vulnerability index
Bagmoniram 0 0 0
Lalkhan Bazar 0.12 0.20 0.16
Pahartali 0.52 0.32 0.42
North Pahartali 1 1 1
Sulakbahar 0.39 0.60 0.50
Ward Name Social Economical Environmental Physical Vulnerability Index
Bagmoniram 0.21 1.00 0.50 0.00 0.43
Lalkhan
Bazar
0.61 0.25 0.68 0.16 0.42
Pahartali 0.56 0.44 0.65 0.42 0.52
North
Pahartali
0.49 0.85 0.00 1.00 0.59
Sulakbahar 0.49 0.08 1.00 0.50 0.52
Vulnerability Assessment
Physical Vulnerability Index
Overall Vulnerability Index
Source: CCC, 2018

Exposure Assessment Analysis with Methodology (Cont.….)
Name of the Ward Average Exposure
Bagmoniram 1631
Lalkhan Bazar 1757
North Pahartali 949
Pahartali 1689
Sulakbahar 1560
 Road and Structure density is
proportional to exposure
 Density – by using ArcGIS 10.4
Exposure Distribution
𝐸𝐼 =
𝑅𝑜𝑎𝑑 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 + 𝑆𝑡𝑟𝑢𝑐𝑡𝑢𝑟𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
2
Average Exposure of Study Area

Analysis with Methodology (Cont.….)Risk Calculation
Risk= LR_2 * VI * EI
(d) (a) (b) (c)

Risk Assessment Analysis with Methodology (Cont.….)
Risk Zone Value
Area
(Acres)
%
Low Risk 0-.1 1225.20 29.87
Moderate Risk .1-.5 2133.05 52.01
High Risk .5-1 743.24 18.12
Total 4101.49 100
Higher Vulnerability
Low Exposure
High vulnerability
High Exposure
 North Pahartali - Low risk zone
 Due to Low Exposure
 Pahartali- High Risk Zone
 Due to High Exposure and High
Vulnerability
Risk Distribution of Study Area
Risk Map

Summary Findings
 Rainfall intensity is increasing
 60% past landslide occurs at 3˚-10˚
 76% past landslide occurs at 20-40m DEM
 Silty sand more vulnerable to landslide
 0-200m from road- all Past LS
 Buildup area is continuously increasing
 Lalkhan Bazar and Pahartali has high exposure to landslide
 Pahartali is more vulnerable than lalkhan bazar
 Around 18% area is found under high Risk Zone
 Pahartali has maximum portion of high Risk Zone.
 More accurate model – logistic regression model which consider all variable

Conclusion and Recommendation
 Explaining the driving factors for supporting emergency decisions & mitigation of future
landslide hazard
 Need to incorporate in development process for prevent, mitigate and avoidance
 Further research is needed to concern the limitations of the study to make the result
more accurate
 Further research is needed to take proper structural and non structural measure to
prevent, mitigate and avoid the landslides

Landslide susceptibility modelling and risk assessment in chittagong city

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