A COMPARATIVE STUDY OF LANDSLIDES AND GEOHAZARD ...

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CHAPTER SEVEN: ANALYSIS OF LANDSLIDE CAUSES, AND CONTRIBUTING FACTORS 113 7.1 Physical Properties of Soil 113 7.1.1 Liquid Limit, Plastic Limit and Plasticity Index Analyses Results 114 7.1.2 Hydraulic Conductivity Test Results 117 7.1.3 Aggregate Stability Analysis Results 118 7.1.4 Bulk Density Tests Results 118 7.1.5 Total Porosity Results 120 7.1.6 Particle size Analysis Results 122 7.2 Rainfall Data Analysis 125 7.2.1 Annual Rainfall Totals for Rumphi and Ntcheu 125 7.2.2 Analysis of Daily Totals Which Triggered the Landslides 126 7.2.3 Analysis of Monthly Totals from 1977 to 2005 for Rumphi and Ntcheu 128 7.3 Results of Vegetation Survey 130 7.4 Land Use Analysis 130 7.5 Results of Slope Angle Analysis 132 7.5.1 Results of the Determination of Slope Angle Using Hoek’s Critical Angle 133 7.5.2 Results of the Determination of Slope Angles Using Fernandes’s Critical Ranges 133 7.6 Mechanisms of Landslides Generation 134 7.6.1 Liquefaction of the Soil 134 7.6.2 High Pore Pressure 136 7.6.3 Cleft Water Pressure 136 7.7 The Role of Slope Angle in the Occurrence of Landslides 137 7.8 Vegetation and Slope Stability 138 7.9 Degree of Aggregation and Slope Instability 142 7.10 Geology, Slope Remodelling and Slope Instability 143 7.10.1 Ntchenachena Area 143 7.10.2 Mvai/Livilivi Catchments 144 7.10.3 Chiweta Area 146 7.11 Conclusion 148 CHAPTER EIGHT: TRADITIONAL KNOWLEDGE, AND THE OCCURRENCE OF LANDSLIDES: PEOPLE’S PERCEPTIONS AND THEIR COPING STRATEGIES 149 8.1 Analysis of Socio-Demographic Aspects of Respondents 149 8.1.1 Sample Size and Duration of Residence 149 8.1.2 Age Structure of Respondents 150 8.1.3 Education Attainment of Respondents 150 8.1.4 Economic Status of Respondents 151 8.1.5 Type of Housing 152 8.1.6 Determination of the Location of Houses 153 8.1.7 Reasons for the Location of Houses 153 8.2 People’s Knowledge on Landslide Occurrences 154 8.3 Perceived Weather Conditions Prior to the Landslide Events 156 8.4 Repetition of Landslide Occurrences 157 xviii
8.5 Cross Tabulation of Perceived Contributing Factors and Level of Education 158 8.6 Cross Tabulation of Knowledge of Landslides and Education 159 8.7 Traditional Beliefs and the Occurrence of Landslides 159 8.8 Age of Respondents and Traditional Beliefs 160 8.9 Level of Education, and Traditional Beliefs 161 8.10 Perceived Causes and Contributing Factors to Landslides 161 8.10.1 Level of Education, and Causes of Landslides 162 8.10.2 Perceived Danger-Prone Areas 163 8.11 Impacts of Landslides 164 8.12 Action Taken During and After the Landslides, and External Support to the Victims 168 8.13 Landslides Occurrences and Coping Strategies 169 8.14 Measures Taken to Combat Landslides 170 8.15 Slope Stability Management, and Government/NGOs Perceived Roles 172 8.16 Gender Perspective on the Occurrence of Landslides 174 8.16.1 Gender and Knowledge of Past Landslides 175 8.17 General Synthesis 177 8.17.1 Vulnerability of Society to Landslides 177 8.17.1.1 Low Incomes 177 8.17.1.2 Location of Settlements 178 8.17.1.3 Production Systems and Land-Use 180 8.17.1.4 Government Policy 181 8.17.2 Knowledge of Landslides 181 8.17.3 Role of Traditional Knowledge 182 8.17.3.1 Education and Traditional Beliefs 184 8.18 Conclusion 184 CHAPTER NINE: ANALYSIS OF LANDSLIDE STUDIES IN MALAWI AND GEOHAZARD MITIGATION MEASURES 185 9.1 Analysis of Landslide Occurrences in Malawi 185 9.2 Recommendations-Hazard Mitigation 190 9.2.1 Vulnerability Reduction 190 9.2.1.1 Alteration of the Environment 190 9.2.1.2 Improving of Stability by Geometric Methods 191 9.2.1.3 Stabilisation by Drainage 192 9.2.1.4 Stabilisation by Plugging 193 9.2.1.5 Rehabilitation by Afforestation 194 9.2.1.6 Stabilisation and Rehabilitation of River Banks 195 9.2.2 Mitigation by Vulnerability Avoidance 195 9.2.2.1 Economic Incentives 195 9.2.2.2 Limiting Activities in Hazard Areas 195 9.2.2.3 Community Participation in Developing Mitigation Measures 196 9.2.2.4 Public Awareness and Outreach 196 9.2.2.5 Government Participation 197 9.2.2.6 Establishment of Early Warning System 197 xix
Page 1 and 2: A COMPARATIVE STUDY OF LANDSLIDES A
Page 3 and 4: DECLARATION I declare that this the
Page 5 and 6: It was found that 131 landslides ha
Page 7 and 8: OPSOMMING In 2003 het ‘n aantal g
Page 9 and 10: verminder, gemeenskapsdeelname in n
Page 11 and 12: ACKNOWLEDGEMENTS I would like to ex
Page 13 and 14: us all that determination and commi
Page 15 and 16: 2.2.2.5 Climate 31 2.2.2.6 Vegetati
Page 17: 5.10.1.3 Crown Width 78 5.10.1.4 Ve
Page 21 and 22: LIST OF FIGURES Figure 2.1a : The P
Page 23 and 24: Ntchenachena Area by goats, contrib
Page 25 and 26: Table 8.10 : Repetition of Landslid
Page 27 and 28: 1.1 Background CHAPTER ONE INTRODUC
Page 29 and 30: these factors. It also aimed at est
Page 31 and 32: Msilimba and Holmes, 2005). Norther
Page 33 and 34: 1.7 Organisation of the Thesis This
Page 35 and 36: Figure 2.1a: The Physiography of th
Page 37 and 38: To these divisions, may be added th
Page 39 and 40: Figure 2.2: Erosion surfaces of Mal
Page 41 and 42: Figure 2.3: The Geology of Malawi.
Page 43 and 44: Figure 2.4: Land use and land cover
Page 45 and 46: seasonal maximum and minimum temper
Page 47 and 48: Figure 2.5: Location of the Ntchena
Page 49 and 50: Figure 2.6: Part of the Ntchenachen
Page 51 and 52: 2.2.1.5 Climate The temperatures on
Page 53 and 54: Figure 2.10: Tobacco curing shed in
Page 55 and 56: sequence includes beds of modular l
Page 57 and 58: 2.2.2.3 Topography The Chiweta Area
Page 59 and 60: 2.2.3 Mvai/Livilivi Catchment Areas
Page 61 and 62: 2.2.3.3 Geology The rocks of the ca
Page 63 and 64: CHAPTER THREE LANDSLIDES: CLASSIFIC
Page 65 and 66: 1982). Topples have been observed t
Page 67 and 68: 3.4 Classification of Slopes In slo
Page 69 and 70:
angle and hence greater values of g
Page 71 and 72:
3.6.5 Implications of Joints and Ro
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movement (Crozier, 1984). Preparato
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containing a high percentage of cla
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largest landslides occur most frequ
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Mshali, 1989; Gondwe and Govati, 19
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avalanche Abefan, Wales 21/9/1966 F
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environmental problems (Taun, 1974)
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Malawi, emphasise only the causes.
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short of the identification and con
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Ingaga et al., 2001; Msilimba, 2002
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CHAPTER FOUR LANDSLIDES INVENTORY I
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4.2 Analysis of the Previous Studie
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4.4 Proposed Mitigation Measures fr
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CHAPTER FIVE METHODOLOGY The curren
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Ground reference data was acquired
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density of drainage network, and th
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weathered. Samples were collected f
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5.11 Soil Analyses Soil samples wer
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5.11.1.4 Determination of Bulk Dens
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5.11.1.8 Determination of Liquid Li
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The questionnaire was coded for eas
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and impacts of landslides and seeki
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CHAPTER SIX LANDSLIDE DISTRIBUTION,
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Ntcheu Livilivi Chiweta Lutowo 8c 2
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distribution was evenly among SE (3
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Figure 6.4: Mapped landslides in th
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6.3 Classification of the Mapped La
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Table 6.2: Landslides Classificatio
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Table 6.4: The Determination of the
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6.6 Discussion of the Landslides Ma
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Catchment where the rocks hang loos
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and the 1991 Phalombe landslides (G
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In Ntcheu District, the Livilivi/Mv
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Figure 6.12: Position where landsli
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CHAPTER SEVEN ANALYSIS OF THE LANDS
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constructed, in the Ntchenachena Ar
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Chiweta Livilivi Mvai 3 53.29± 10.
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was confirmed by ANOVA test (p=0.00
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Table 7.9: Results of the Analysis
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Table 7.11: Medium/Fine Sand Test R
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Mvai 55.8±6. 41 1 69.2±9. 34 67.8
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Rainfall (mm) 200 150 100 50 0 Dail
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The landslides of the Ntchenachena
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customary land tenure. Most of the
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Hoek’s critical angle for sliding
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esistance for these soils was proba
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acting as a lubricant (Crozier, 198
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cover of grasses and shrubs, record
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with major structural rock weakness
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disturbance caused by deforestation
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Figures 7.14 and 7.15). This has pa
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Figure 7.16: Highly weathered Chiwe
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CHAPTER EIGHT TRADITIONAL KNOWLEDGE
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majority of the respondents had att
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Table 8.3: Types of Housing Distric
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Table 8.6: Knowledge of Past Landsl
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Table 8.9: Weather Conditions Befor
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Table 8.11: Level of Education and
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Table 8.13B: Age of Respondents and
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with tertiary education were observ
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construction during the rainy seaso
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Figure 8.3: Degraded agricultural l
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out an assessment of the damage. La
Page 197 and 198:
2005). The results from these studi
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Table 8.23: Responsibility for Slop
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This study, therefore, realises tha
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wanted the NGOs/Government to rehab
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difficult and also reduces the area
Page 207 and 208:
8.17.1.4 Government Policy The majo
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noise from drums. These spirits are
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CHAPTER NINE ANALYSIS OF LANDSLIDE
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true for the entire East Africa reg
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This explains why the majority of l
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damage from landslides. In areas wh
Page 219 and 220:
embankments may result in a build u
Page 221 and 222:
continued destruction of the vegeta
Page 223 and 224:
Furthermore, future research should
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esults have been encouraging (Mikke
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landslides. Gender perceptions towa
Page 229 and 230:
The destruction of vegetation in al
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stabilisation can also be achieved
Page 233 and 234:
knowledge on landslides in Malawi a
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Badshah, A.: 1994, The Mega-Cities;
Page 237 and 238:
Briggs, J. Badri, M. and Mekki, M.:
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Cooke, R.U and Doornkamp, J.C.: 199
Page 241 and 242:
Fairhead, J. and Scoones, I.: 2005,
Page 243 and 244:
Harlford, S. and Leonard, P.: 2001,
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Jibson, R.W. and Keefer, D.K.: 1968
Page 247 and 248:
Ludman, A. and Koch, N.I.: 1982, Ph
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Mwafongo, K.W.M.: 1996, Rural Devel
Page 251 and 252:
Pitty, A.F.: 1984, Geography and So
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Tsukamoto, Y. and Kusakabe, O.: 198
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Yamamuro, J.A and Lade, P.V.: 1998,
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v = volume of slope material involv
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APPENDIX 3: HOUSEHOLD QUESTIONNAIRE
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5. Are you employed? Yes (proceed t
Page 263 and 264:
15. What are the traditional belief
Page 265 and 266:
26. Which crops were affected by th
Page 267 and 268:
36. What was the most important for
Page 269 and 270:
APPENDIX 4: DISTRICT COMMISSIONERS,
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13 How long does it take for inform
Page 273 and 274:
6. How far have you gone with lands
Page 275 and 276:
APPENDIX 6: MULTIPLE COMPARISON TES
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
APPENDIX 9: TESTS FOR THE EQUALITY
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Hydraulic conductivity cm/hr (>100
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Litowo 8 Pit 9 0615288 8819034 1445
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Mvai 2 Pit 8 0675274 8355428 1379 M
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RAINFALL DATA FOR MVAI/LIVILIVI FRO
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PIT 3 LUT 3 0-100 69..80 34.31 35.4
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KASFOR PIT 1 KASFOR >100 43.06 30.9
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PIT 4 CHIKWE 0-100 81.42 43.45 37.9
Page 297 and 298:
PIT 5 MVAI 1 0-100 51.99 36.07 15.9
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NTCHEU FIELD DATA APPENDIX 15: RESU
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Mchenje 167 130 5.7 4.1 Shallow ro
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CHIWETA U1-11 Dsh (mm) Dbh (mm) H (
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AVERAGE 125 93 5.5 3.6 LITOWO 1a-3
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LITOWO 7a-u Dsh (mm) Dbh (mm) Mnthu
Page 309:
Mnthunu 50 Chi 1l 0615438 8819106 1
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A COMPARATIVE STUDY OF LANDSLIDES AND GEOHAZARD ...

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