LANDSLIDE PROBLEMS AND MANAGEMENT IN HIMALAYA
Dr. Ravinder Singh
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First Edition : 2018
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(ii) DEDICATED TO My Immortal Father & in the Memory of those People Who Lost their Lives in Landslides
(iii) (iv) PREFACE
It was the best of times, it was the worst of times, It was the age of wisdom, it was the age of foolishness, It was the epoch of belief, it was the epoch of incredulity, It was the season of light, it was the season of darkness, It was the spring of hope, it was the winter of despair. Excerpt from “A Tale of Two Cities” (Charles Dickens) In 1859, Charles Dickens wrote this phrase in his famous novel “A Tale of Two Cities” which also truly describe disaster scenario of today’s world. Every year, landslides are the common story in the Himalaya. During the monsoon season, the life of a common man is threatened and affected by it. The socio-economic losses are very high due to the frequent occurrences of landslides. Studies have shown that on an average, one landslide occurs at almost every 2 km along the highways in Himalayan terrain. Although individual landslides in these areas do not result in mass casualty and damages yet the cumulative losses over a particular period of time are comparable to other disasters like earthquakes, floods, etc. Average annual losses are estimated to approximately 3-4 billion rupees (INR) besides loss of hundreds of lives and other intangible damages. Landslide is the disaster that knows no geographical boundaries and affects irrespective of race, religion, caste, creed or color all over the world. However, it is not the landslide which kills people but the unplanned development and ill-conceived strategies are responsible for the damages. This book is an attempt to develop landslide zonation with the application of Remote Sensing (RS) and Geographical Information System (GIS) and suggest the proper management techniques for the affected areas. This volume will be indispensable to scholars and researchers of landslide disaster management, environment and development studies as well as policymakers and those in administrative, governmental and development sectors. This book is divided into the six chapters and their subdivisions. Chapter 1 is dedicated to the research problem, understanding of problem with the help of slope instability mechanisms, review of
(v) previous work done, formulation of hypothesis and objectives, source of data and methodology for solving these problems. Chapter 2 emphasizes upon the vital role played by the geological and structural setting in triggering the mass movement. Most of the landslides are found in the vicinity of the weak shear zone, faults, lineaments and fractured lithology in the study area. Chapter 3 deals with the importance of the drainage control over the area and landforms formed by different geomorphologic processes with their distribution. It also provides extensive coverage to mass wasting and weathering, and describes the elements of slope (slope aspect and slope morphology) in the study region. Analysis of soil depth, soil texture and in situ examination of soil samples with the help of laboratory testing is the subject matter of Chapter 4. The distribution of soil is uneven; therefore the contribution of soil in the occurrence of landslide is very important. Chapter 5 gives detail description of land use types and their distribution in the investigation area. Land use is also affected by the anthropogenic activities which plays a significant role in the occurrence of mass movements in this region. Chapter 6, the last chapter, highlights the factors responsible for the triggering of landslides, importance of the parameters (geology, drainage, weathering, slope, soil, land use, etc.) in the Landslide Hazard Zonation (LHZ) and Management (LHM). It also focuses on the level of awareness amongst the local community and the miserable situation faced by them due to landslides. The socio-economic impact assessment and assessing the awareness level towards landslides in investigation area is done with the help of questionnaire. The study will be summarized in conclusion and suggestions, in which the future strategy for making the region safe will attempted to be chalked out. Author
(vi) ACKNOWLEDGEMENTS
It is my privilege to acknowledge all those persons who helped me enormously in completing this work successfully. During the past years, I have been helped by many people and this manuscript is the result of their help. I would like to express my gratitude towards them. I am extremely grateful to my mentor and Ph.D. supervisor Prof. R.K. Pande, (Head, Geography Department, Kumaun University) for his precious and remarkable supervision during research work. My interest in Disaster Management was kindled at the postgraduate level by his interesting lectures and it ultimately made me pursue a doctoral thesis in the subject to delve deeper into the enigmatic world of disaster management. His constructive criticism and critical reviewing have greatly helped me to complete this book. I want to sincerely appreciate the guidance and motivation provided by Lt. Gen. (Retd.) Shri N.C. Marwah, Member, NDMA in official work and to transform my research work into book. During the course of my doctoral thesis, I have been to Department of Chemistry, Pant Nagar University. I am profoundly grateful to Prof. A.K. Pant (Chemistry Department, Pant Nagar University) for providing me the laboratory facilities for the analysis of soil samples. I am especially thankful to my friends and colleagues during research and official work who offered me valuable advice and suggestions. I am heartily thankful to my parents and wife for being supportive to accomplish this task and for being a pillar of strength in moments of despair, and all my family members for encouraging me that made all the difference. Their optimism and enthusiasm have always helped me to think positively. Last but not the least, I record my sincere thanks to Shri Ajay K. Gupta and Dr. G.S. Saun, ICSSR because this book is a result of the financial support provided by ICSSR, New Delhi. Author
(vii) (viii) CONTENTS
Preface (v) – (vi)
Acknowledgement (vii)
List of Tables (xii)
List of Table in Conclusion and Recommendation (xii)
List of Figures (xiii) – (xiv)
List of Figures in Conclusion and Recommendation (xiv)
List of Plates (xv) – (xvi)
List of Plates in Conclusion and Recommendation (xvi)
Acronyms and Abbreviations (xvii) – (xviii)
Landslide Glossary (xix) – (xx)
1. INTRODUCTION 1 – 44 1.1 Objectives 1.2 The Study Area 1.3 Data Used 1.4 Methodology 1.4.1 Procurement of Satellite Data 1.4.2 Visual Interpretation of Satellite Data 1.4.3 Ground Truth Data Collection 1.4.4 Cartographic Work 1.4.5 GIS Analysis 1.4.5.1 Base Map 1.4.5.2 Lithological Map 1.4.5.3 Rock Weathering 1.4.5.4 Soil Map 1.4.5.5 Geomorphological Map 1.4.5.6 Slope Map 1.4.5.7 Slope Aspect Map 1.4.5.8 Slope Morphology Map 1.4.5.9 Lineament Maps 1.4.5.10 Fault Map 1.4.5.11 Land Use Map
(ix) 1.4.5.12 Anthropogenic Factor Map 1.4.5.13 Landslide (Active and Old Landslide) Map 1.4.6 Questionnaire Survey Data Analysis 1.4.7 Landslide Hazard Zonation (LHZ) Modeller 1.4.7.1 Developing the Analytical Hierarchical Process (AHP) Hierarchy 1.4.7.2 Comparing the Decision Elements on a Pair Wise Base 1.4.7.3 Constructing an Overall Priority Rating 1.4.8 Landslide Hazard Zonation (LHZ) and Landslide Hazard Management (LHM) Modelling Procedure
2. GEOLOGY OF THE AREA 45 – 64 2.1 Structural Setting of the Area 2.2 Lithology 2.3 Lineaments
3. GEOMORPHOLOGY OF THE AREA 65 – 111 3.1 Drainage 3.2 Landforms 3.2.1 Denudational Structural Hill 3.2.2 River Terraces 3.2.3 Flood Plain 3.2.4 Valley 3.2.5 Toe Removal 3.2.6 Glacio-fluvial 3.3 Mass Wasting and Weathering 3.3.1 Types of Mass Wasting 3.4 Slope 3.4.1 Slope Aspect 3.4.2 Slope Morphology
4. SOIL OF THE AREA 112 – 125 4.1 Soil Depth and Soil Texture 4.1.1 Soils on the Ridge Top 4.1.2 Soils on Side Slopes
(x) 4.1.3 Soils on Fluvial Valley 4.1.4 Soils on Cliffs
5. LAND USE/LAND COVER OF THE AREA 126 – 140 5.1 Types of Land Use/Land Cover 5.1.1 Dense Vegetation 5.1.2 Medium Vegetation 5.1.3 Degraded Vegetation 5.1.4 Scrubs/Grassland 5.1.5 Forest Blank 5.1.6 Barren Land (Rocky) 5.1.7 Barren Land (Non-rocky) 5.1.8 Agricultural Land 5.1.9 Built-up Area 5.1.10 Snow Covered Area 5.1.11 River/Water Body 5.1.12 Anthropogenic Activities
6. LANDSLIDE HAZARD ZONATION 141 – 166 6.1 Factors Causing Landslides 6.2 Importance of the Parameters 6.3 Landslide Hazard Zonation and Management Maps 6.3.1 Socio-economic Impact of the Landslides on the Communities 6.3.2 Awareness and Capacity Building Measures to Minimize the Impact of Future Landslides CONCLUSION AND RECOMMENDATION 167 – 200 BIBLIOGRAPHY 201 – 209 ANNEXURES 210 – 225
(xi) LIST OF TABLES
Table No. Description Page No. Table 1.1 Classification of Slope Movement (Abbreviated 6 Version, Varnes, 1978) Table 1.2 Causes of Landslides 6 Table 1.3 Average Monthly Rainfall (in mm) and Temperature 20 of Agustmuni Table 1.4 Monthly Rainfall (in mm) over the Years at Okhimath 21 Table 1.5 Average Monthly Rainfall (in mm) and Temperature 22 (in ºC) of Okhimath Table 1.6 Average Monthly Rainfall (in mm) and Temperature 23 – 24 (in ºC) of Gopeshwar Table 1.7 Types of Parameters 38 Table 2.1 Litho-Tectono-Stratigraphic Succession/Setting of the 54 – 55 Mandakini Valley Table 3.1 Spatial Distribution of Geomorphological Units in the 68 Study Area Table 3.2 Types of Landslide Class and their Areal Coverage 79 Table 3.3 Detail Inventory of Active Landslides in the Study 81 – 83 Area Table 3.4 Bheti-Paundar Landslide Study 89 – 91 Table 3.5 Byung-gad Landslide Study 94 – 97 Table 3.6 Silli Chatti Landslide Study 100 – 104 Table 3.7 Weathering Level in the Study Area 107 Table 3.8 Slope Categories 108 Table 3.9 Slope Aspect 109 Table 3.10 Slope Morphology Category 110 Table 4.1 Soil Depth Class 114 Table 4.2 Soil Texture Class 115 Table 4.3 Analysis of Soil Samples Collected during Field Work 117 – 119 Table 5.1 Land Use Pattern in the Study Area 138 Table 6.1 Hazard Zone Classification 150 Table 6.2 Hazard Zone Wise Classification of Villages 152 – 159 Table 6.3 Number of Villages under Different LHZ Categories 159 Table 6.4 Types of Management Practices 161 Table 6.5 Survey of Village Representative (Gram Pradhans) 162 Table 6.6 Administrative Survey 163
LIST OF TABLE IN CONCLUSION AND RECOMMENDATION
Table 1.00 Guidelines for Applying Bio-engineering Techniques 191 – 192 to All Slopes
(xii) LIST OF FIGURES
Fig. No. Description Page No. Fig. 1.1 Contour map of the study area 8 Fig. 1.2 Slope aspect map of the study area 8 Fig. 1.3 HSV shader map of the study area 9 Fig. 1.4 Gradient shader map of the study area 9 Fig. 1.5 Digital Elevation Model (DEM) of the study area 10 Fig. 1.6 Location map of the study area 19 Fig. 1.7 (a) Average Monthly Rainfall (in mm) of Agastmuni 20 Fig. 1.7 (b) Average Monthly Temperature (in ºC) of Agastmuni 21 Fig. 1.8 Monthly Rainfall (in mm) of Okhimath 22 Fig. 1.9(a) Average Monthly Rainfall (in mm) of Okhimath 23 Fig. 1.9(b) Average Monthly Temperature (in ºC) of Okhimath 23 Fig. 1.10(a) Average Monthly Rainfall (in mm) of Gopeshwar 24 Fig. 1.10(b) Average Monthly Temperature (in ºC) of Gopeshwar 24 Fig. 1.11 Flow Chart Depicts the Impact of Precipitation on 25 the Mass Movement Fig. 1.12 Analytical Hierarchy Process (AHP) Method 37 Fig. 2.1 Structural Map of the Study Area 49 Fig. 2.2 Geological Map of the Study Area 55 Fig. 3.1 Landforms of the Study Area 69 Fig. 3.2 Glacio-fluvial Geomorphological Map of Kedarnath 75 Area Fig. 3.3 Schematic Diagram of Mass Wasting 77 Fig. 3.4 Types of Landslides 79 Fig. 3.5 Mass Wasting as Open System 87 Fig. 3.6 (a) Profile and 92 (b) Morphology of Bheti-Paundar Landslide Fig. 3.7 (a) Profile and 98 (b) Morphology of Byung-gad Landslide Fig. 3.8 (a) Profile and 105 (b) Morphology of Silli Chatti Landslide Fig. 3.9 Level of Weathering in the Study Area 107 Fig. 3.10 Slope Categories in the Study Area 109 Fig. 3.11 Slope Aspect 110 Fig. 3.12 Slope Morphology 110 Fig. 4.1 The Stress Imposed by Gravity at a Point in a Soil 113 Mass
(xiii) Fig. 4.2 Soil Depth Class 114 Fig. 4.3 Soil Texture Class 115 Fig. 4.4 Erodibility Analysis of Soil Samples 119 Fig. 4.5 Hardness and Penetration Capability of Slope 120 Fig. 5.1 Land Use in the Himalayan Region 128 Fig. 5.2 Land Use Pattern of the Study Area 138 Fig. 6.1 Pictorial Depiction of Landslide Hazard Zonation and 143 Risk Map Fig. 6.2 Hazard Zone Classification 150 Fig. 6.3 Villages Vulnerable towards Landslide 160 Fig. 6.4 Management Practices in the Study Area 161 Fig. 6.5 Awareness Level of the Women in Comparison to Men 162
LIST OF FIGURES IN CONCLUSION AND RECOMMENDATION
Fig. No. Description Page No. Fig. 1.00 The Components of the Landslide Disaster 169 Management Process Fig. 2.00 Location of Interceptor Drain Where Slope Changes 176 Abruptly from Steep to Flat Fig. 3.00 Location of Interceptor Drain where Impervious Layer 177 Comes Close to Ground Surface Fig. 4.00 Location of Interceptor Drain at the Foot of a Slope 177 Fig. 5.00 Location of Interceptor Drain where Pervious Layer is 178 Sandwiched between Poorly Pervious Layers Fig. 6.00 Location of Interceptor Drain where Seepage from 179 Water Channels Occurs into Flow Lands Fig. 7.00 (a) Drainage of Steep Land with All Flow Originating 179 – 180 from Foreign Source Upslope and (b) Drawdown Effect of Interceptor Drains When Source is Local Rainfall Fig. 8.00 Type of Retaining Wall – (a) Gravity Wall, (b) Tie 182 – 183 Back Wall, (c) Driven Cantilever Wall, (d) Reinforced Earth Wall and (e) RCC Fig. 9.00 Arrangement of Retaining Wall and Breast Wall for: 184 (a) Road and (b) Building Complexes Fig. 10.0 Stepping Foundation 186 Fig. 11.0 Dry stone Masonry Wall – (a) Very Small Strength, 187 (b) Poor Strength, (c) Unstable Filling and (d) Good Filling Fig. 12.0 RCC Bonding Element 188 Fig. 13.0 Slope Stability and Bio-engineering Techniques 190
(xiv) LIST OF PLATES
Plate No. Description Page No. Plate 2.1 (a) Quartzite (Jagibagwan) and (b) Quartzite Weathered 47 (Phata) Plate 2.2 (a) Biotite-Schist (Okhimath) and (b) Chlorite-Mica- 48 Schist (Gopeshwar) Plate 2.3 Gneissic-Quartzite (Kalimath) 48 Plate 2.4 (a) Nappe and (b) Parasitic/Satellite Fold in Tungnath 49 Area Plate 2.5 (a) Micaceous-Quartz (Lanco Tunnel Site) and 50 (b) Garnet-Mica-Schist (Agastmuni) Plate 2.6 Fault Breccia (Kedarnath Way) 52 Plate 2.7 Gneiss (Bhadaj) 54 Plate 2.8 (a) Muscovite-Quartzite (Tungnath) and (b) Quartz- 56 Muscovite (Vijaynagar) Plate 2.9 (a) Salt Paper Type-Sandstone (Tal Formation-Sankari) 57 and (b) Sandstone-Quartzite (Chandrashila) Plate 2.10 Muscovite (Byung) 57 Plate 2.11 Schist (Tungnath) 57 Plate 2.12 (a) Micaceous-Schist (Raun-Lekh) and (b) Phyllite 58 (Phata) Plate 3.1 Debris Slide along the Mandakini River near 67 Rudraprayag Plate 3.2 Highly Dissected Denudo-structural Hill in Tungnath 70 Plate 3.3 Moderately Dissected Denudo-structural Hill of 72 Jagibagwan Plate 3.4 Low Dissected Denudo-structural Hill near Raun-Lekh 72 Plate 3.5 River Terraces of Mandakini River in Agastmuni 73 Plate 3.6 Flood Plain of Madhyamaheswar Ganga 73 Plate 3.7 V-shaped Valley of Madhyamaheswar Ganga 74 Plate 3.8 Toe Removal by the Madhyamaheswar Ganga 75 Plate 3.9 Rock Fall on the Way to Kedarnath 80 Plate 3.10 Some Old Landslides in the Study Area 86 Plate 3.11 Bheti-Paundar Landslide Struck the Opposite Bank 88 Plate 3.12 Growth of Mosses over the Rock 106 Plate 4.1 Equipments for Soil Sample Analysis 120 Plate 4.2 Chopta (Tungnath-Chandrashila) Showing Slumping 123
(xv) Plate 5.1 Dense Vegetation of the Gaurikund Forest 131 Plate 5.2 Medium Vegetation of the Nala Village 131 Plate 5.3 Degraded Vegetation near the Kuntha Village 132 Plate 5.4 Scrub/Grassland of the Tungnath 133 Plate 5.5 Forest Blank near Tungnath 133 Plate 5.6 Barren Land (Rocky) Area on the Way to Raun-Lekh 134 Plate 5.7 Barren Land (Non-rocky) Hill from Tungnath 134 Plate 5.8 Agricultural Land near: (a) Nala and (b) Kuntha Village 135 Plate 5.9 (a) Kalimath, (b) Okhimath, (c) Guptkashi Towns and 135 – 136 (d) Gopeshwar Plate 5.10 Snow Peaks from Tungnath 136 Plate 5.11 (a) Mandakini, (b) Madhyamaheswar, (c) Kaliganga and 137 (d) Alaknanda Rivers Plate 5.12 Anthropogenic Activities by: (a) Lanco and (b) L&T 137 Plate 6.1 (a) Mr. Aditya Ram Jamloki and Mrs. Narmada Jamloki 164 and (b) Mr. Premlal Rehabilitated to Village Nala
LIST OF PLATES IN CONCLUSION AND RECOMMENDATION
Plate No. Description Page No. Plate 1.00 Retaining Wall Practices in the Study Area 185 Plate 2.00 Rock Fall Zone NH 109 189 Plate 3.00 Afforestation under the Development Working Plan 194
(xvi) ACRONYMS AND ABBREVIATIONS
AP Arithmetic Progression AHP Analytical hierarchical Process ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer AWS Automatic Weather Station BIS Bureau of Indian Standard BPL Below Poverty Line CBDM Community Based Disaster Management DEM Digital Elevation Model GIS Geographical Information System GOI Government of India GoUA Government of Uttarakhand GP Gram Panchayat GP Geometric Progression GPS Global Positioning System ICS Incident Command System HDDSH Highly Dissected Denudo-Structural Hill HSV Hue Saturation Value IR Infra Red IRS Indian Remote Sensing IS Indian Standard ISDR International Secretariat for Disaster Reduction LDDSH Low Dissected Denudo-Structural Hill LHEF Landslide Hazard Evaluation Factor
(xvii) LHZ Landslide Hazard Zonation LHM Landslide Hazard Management LISS Linear Imaging Self-scanning System LRRD Linking Relief and Rehabilitation with Development LSZ Landslide Susceptibility Zonation LNSF Landslide Nominal Susceptibility Factor L&T Larsen and Tubro MMDDSH Moderately Dissected Denudo-Structural Hill MCT Main Central Thrust NCCF National Calamity Contingency Fund NDMA National Disaster Management Authority NDRF National Disaster Response Force NGO Non-Governmental Organisation PAN Pancromatic RCC Reinforced Concrete Cement RS Remote Sensing UNESC United Nations Educational, Scientific and Cultural Organization
UR&RP Uttarakhand Relief and Rehabilitation Policy
(xviii) LANDSLIDE GLOSSARY
Avalanche – a large mass of snow, ice, soil, rock, or mixture of these, which falls or slides very rapidly under the force of gravity. Bed – a layer of rock, usually sedimentary or volcanic. Bedrock – a term used to describe the solid rock that underlies soil or other unconsolidated material. Creep – the gradual movement of soil and other materials down a slope. Fall – a landslide in which material free falls. Flow – viscous to fluid-like motion of debris down a slope. Geotechnics – the use of engineering principles to understand how earth materials, such as soils and rocks, behave. This knowledge is applied to better design engineering structures. Ground water – water which occurs underground, as opposed to surface water. Joint – a fracture or parting in rock without any apparent displacement. Landslide – a general term used to describe the downslope movement of soil, rock and organic materials under the influence of gravity. It also describes the landform that results. Metamorphic – rocks which have formed from pre-existing rocks rocks due to changes in temperature, pressure, stress or chemistry. Sedimentary – rocks formed by the accumulation of fragments, or rocks the precipitation of dissolved material, that result from the weathering of pre-existing rocks. Slide – the movement of rock or unconsolidated material parallel to planes of weakness and occasionally parallel to slope. Slump – the complex movement of materials on a slope; includes rotational slump.
(xix) Topple – the end-over-end motion of rock down a slope. Torrent – a sporadic and sudden channelized discharge of water and debris. Unconsolidated – loose sediment that has not been cemented or otherwise converted to solid rock. Volcanic – rocks which result from volcanic action at, or near, rocks the surface of the Earth such as lava flows or ash deposits. Weathering – the disintegration of rocks on the Earth’s surface by the action of rain, frost, heat, wind, etc.
(xx) 1 INTRODUCTION Chapter
Structure
1.1 Objectives 1.2 The Study Area 1.3 Data Used 1.4 Methodology 1.4.1 Procurement of Satellite Data 1.4.2 Visual Interpretation of Satellite Data 1.4.3 Ground Truth Data Collection 1.4.4 Cartographic Work 1.4.5 GIS Analysis 1.4.5.1 Base Map 1.4.5.2 Lithological Map 1.4.5.3 Rock Weathering 1.4.5.4 Soil Map 1.4.5.5 Geomorphological Map 1.4.5.6 Slope Map 1.4.5.7 Slope Aspect Map 1.4.5.8 Slope Morphology Map 1.4.5.9 Lineament Maps 1.4.5.10 Fault Map 1.4.5.11 Land Use Map 1.4.5.12 Anthropogenic Factor Map 1.4.5.13 Landslide (Active and Old Landslide) Map 2 Landslide Problems and Management in Himalaya
1.4.6 Questionnaire Survey Data Analysis 1.4.7 Landslide Hazard Zonation (LHZ) Modeller 1.4.7.1 Developing the Analytical Hierarchical Process (AHP) Hierarchy 1.4.7.2 Comparing the Decision Elements on a Pair Wise Base 1.4.7.3 Constructing an Overall Priority Rating 1.4.8 Landslide Hazard Zonation (LHZ) and Landslide Hazard Management (LHM) Modelling Procedure The study and analysis of landslides have become the most burning topics of today in disaster management of mountainous terrain. Because of landslides every year, thousands of people lose their life all over the world, and hence, it deserves intensive study to save lives through better prediction, management, and warning procedures (Bloom, 1978). In many developing countries like India, slope failures constitute a continuing and serious impact on the social and economic structure, of which the true measure is not in monetary units but rather in disruption and attendant misery of human lives (Varnes, 1984). The frequency of landslides in the Garhwal Himalaya varies from one place to another, depending on the underlying structures, physiographic setting and anthropogenic changes taking place. Every year, the road network in the region sustains damages at hundreds of locations, due to incidence of big or small magnitude. The past history of landslides (before 1998) in this region clearly brings out the damages to life and property from these hazards (Joshi et al., 2001). Generally, landslide is defined as the rapid downward and outward movement, under the influence of gravity, of a mass of rock, earth or artificial fill on a slope. Landslide occurs due to natural processes as well as anthropological activities. Both of them play a major role as the triggering factor in the occurrence of landslides. We cannot control the natural process but we can undoubtedly manage our anthropological activity in a sustainable relation with the nature. It is not wrong to say that landslides fall in the category of natural as well as man-made disaster. Introduction 3
Mechanism of Landslide There are some fundamental laws which are not only helpful in understanding the natural and physical processes active in our surroundings, but also in understanding the mechanism of landslide in a more logical way. Some of the most famous fundamental laws are applied to understand the processes more clearly which are discussed below: 1. According to “Law of Conservation of Mass”, the total mass of the reactant (slope) must be equal to the total mass of the product (landslide) and several other factors play a role of catalyst in this exothermic reaction. Such reactions which occur with the liberation of energy are known as exothermic reactions. A vast amount of energy is liberated when a mass movement happens, as a result of which destruction occurs. The magnitude of destruction depends upon the amount of energy released due to mass movement. Slope + Rain + Other Factors → Landslide/Mass Movement = –H Reactant Product where, Slope, rainfall (water) and other factors = Reactant, Landslide/mass movement is the result of reaction between reactants = Product, and ∆H = Exothermic reaction or release of energy at the end of reaction. In our nature, so many chemical reactions are going on and one of the crucial example of this is the reaction of water with the rocks (limestone, shale, dolomite, phyllite, etc). Both, water and limestone act like a reactant in the chemical reaction, degrade the slope, make them more prone or leads to landslides which act as a product. In this reaction, when sometimes the landslide of huge block takes place, an enormous amount of energy is released (∆H) like the one which happened during Raun and Lekh (1998) in which one whole village was destroyed by the block of big boulders which crossed the Madhyamaheshwar Ganga river and hit the village situated on the other side of the river bank. It has been observed that the amount of destruction is dependent on the energy released in the mass movement. 4 Landslide Problems and Management in Himalaya
2. According to “Law of Gravitational Force of Attraction”, the force of resistance is directly proportional to gravity and mass of the rock. m m F g 1 2 where, F = Force of resistance, g = Gravity,
m1 = Mass of the slope and m2 = mass of the external factors (i.e., water, tree, buildings, etc.) and α = Angle of the slope.
When F < m1, m2 and g, landslide will occur. When the precipitation occurs, the water percolates in the soil. If it crosses the saturation limit of the soil, then the mass of soil or slope (m1) and mass of water (m2) have combined effect under the gravitational pull (g) which causes landsliding. The duration of landslide also depends upon the angle of the slope (α). If the angle of slope is high, then it will take less time to slide down to overcome extra pressure put by the external factors on the slope. Such type of cases happened in the study area during 1998 in Jagasu-Mansuna, Byung, Phata, Gaurikund, Kalimath and Vijaynagar. 3. According to Albert Einstein’s equation, which states that energy released by the mass movement is equal to the mass of the rock and velocity of displacement. E = mc2 where, E = Energy, m = Mass of slope/rock, and c = Velocity of displacement of slope. The heavy rainfall is responsible for the occurrence of landslides in the mountainous terrain. When the raindrop hits the earth surface with the extreme velocity (c), then the soil particles are detached from the Introduction 5 soil (also known as splash erosion). When the block of rock falls due to gravity, then the velocity will increase twice due to two factors: weight of slope/rock (m) and gravitational pull (g). The amount of energy (E) released due to landslide is dependent upon the mass of the slope or rock (m) and velocity of displacement of slope or rock (c). The extent of damage depends upon the mass of the rock and the velocity with which it hits the settlements like in the case of Raun and Lekh. 4. The principle of ‘limiting equilibrium’ is found applicable in the landslide mechanism when the forces driving the ground mass are greater than the forces resisting ground movement (Bhagwan, 2005). Gravity (g) Resistance (r) When g > r, landslide will occur. The equilibrium between the gravity and resistance is very important factor in the slope stability. If the equilibrium between them is disturbed due to the external factors (i.e., water, tree, buildings, etc.) which decreases the resistance force, the slope moves downward under the gravity. Hence, the condition of slope instability is formed and mass movement will occur. 5. The principle of “past and present are keys to the future” is also found applicable in the study of slope failure. Slope failure in the past gives the evidences of the most important governing factors which lead to the present-day slope failure and related problems in the area.
Classification of Landslides In general, landslides are classified into falls, topples, slides, lateral spreads, flows and complex movements. The categories are further sub- divided according to the type of material (rock, debris, earth, soil) that constitutes the landslide (Bhagwan, 2005). This classification is illustrated in the Table 1.1. There are many factors or elements which are responsible for the occurrence of landslides. These factors are divided into four types on the basis of the causes of landslides (Table 1.2). 6 Landslide Problems and Management in Himalaya
Table 1.1: Classification of Slope Movement (Abbreviated Version, Varnes, 1978) TYPE OF MOVEMENT TYPE OF MATERIAL BEDROCK ENGINEERING SOILS Mostly coarse Mostly fine FALLS Rock fall Debris fall Earth fall TOPPLES Rock topple Debris slump Earth topple SLIDES Rotational Few Rock slump Debris slump Earth slump units Translational Many Rock block slide Debris block slide Earth block slide units Rock slide Debris slide Earth slide LATERAL SPREADS Rock spread Debris spread Earth spread
FLOWS Rock flow Debris flow Earth flow (Deep creep) (Soil creep) COMPLEX Combination of two or more principal type of movement Source: Bhagwan, J., 2005. Table 1.2: Causes of Landslides Ground Morphological Physical Anthropological Causes Causes Causes Causes 1. Weak, sensitive, or 1. Tectonic 1. Earthquake 1. Excavation weathered upliftment materials 2. Ground structure 2. Erosion 2. Rainfall and cloud 2. Loading of slope (joints, fissures) (wind,water) burst crest and structural discontinuities
3. Physical property 3. Scour 3. Weathering (thawing, 3. Deforestation variation freezing) (permeability, plasticity) 4. Deposition 4. Artesian pressures 4. Artificial vibration loading in the slope crest. 5. Vegetation 5. Water impoundment removal (forest and leakage from fire, drought) utilities The term ‘Zonation’ applies in general sense to division of the land surface into area and ranking of these areas according to degrees of actual or potential hazard of landslides or other mass movements on slopes (Varnes, 1984). Landslide Hazard Zonation (LHZ) map depicts division of land surface into zones of varying degree of instability based on the estimated significance of the causative factors in inducing Introduction 7 instability. It is a rapid, simple and economical mapping technique incorporating the major causative factors of slope instability such as lithology, structure, slope morphometry, relative relief, land use/land cover and hydro geological conditions (Gupta et al., 1993). The LHZ maps have an important role in planning and implementation of development schemes in mountainous areas. The landslide hazard zonation (LHZ) maps identify and delineate unstable hazard prone area; therefore, environmental regeneration programmes can be initiated by adopting suitable mitigation measures. These maps are of great help to the planners and field engineers to choose favourable locations for development schemes such as building and road constructions.
Advantages of Remote Sensing and Geographical Information System (GIS) in the Study of Landslides The remote sensing and GIS are broad subjects, and in today’s world, they have proved to be very helpful. The application of remote sensing and GIS is very vast and can been applied in the different fields of study. Also in the disasters, it proved very beneficial and essential tool in all the three phases of disaster management, i.e., Pre-disaster, During-disaster and Post-disaster. The remote sensing is an important factor in detecting landslides because it is not always easy to access the place of mishap by commuting to the place. The use of remote sensing is very important at that time. The remote sensing based landslide studies mainly deal with the detection, mapping, monitoring and the GIS has the application potential to integrate a variety of data sets at different scales to generate landslide hazard zonation map which is very beneficial for the management at the time of disaster and also for the development activities (Arya et al., 1994). This is the efficient and effective tool of landslide analysis in this technological world. The satellite images like Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) of 15 m resolution is quite beneficial in understanding the topography and physiography of the study area (Figures 1.1 to 1.5). 8 Landslide Problems and Management in Himalaya
Contour Interval 100 m
Fig. 1.1: Contour Map of the Study Area
Fig. 1.2: Slope Aspect Map of the Study Area Introduction 9
7,000 m
6,000 m
5,000 m
4,000 m
3,000 m
2,000 m
1,000 m
1 : 300,000 0 3 6 12 18 24 Kilometers Fig. 1.3: HSV Shader Map of the Study Area
7,000 m
6,000 m
5,000 m
4,000 m
3,000 m
2,000 m
1,000 m
1 : 300,000 0 3 6 12 18 24 Kilometers Fig. 1.4: Gradient Shader Map of the Study Area 10 Landslide Problems and Management in Himalaya
LEGEND 53006300 --7100m7100 m
55005500 -- 63006300mm
47004700 - 55005500mm
39003900 - 4704700m0 m
3100 -- 39003900mm
2300 -- 31003100mm
1500 - 23002300mm
700 -- 15001500mm
1 : 300,000 0 3 6 12 18 24 Kilometers Fig. 1.5: Digital Elevation Model (DEM) of the Study Area Figure 1.1 represents the contour map of the investigation area having a contour interval of 100 m. Figure 1.2 clearly demarcates that the maximum area is covered under the west facing slope (212.240 km2), south-east facing (205.590 km2), and south-west facing (194.474 km2). However, the minimum area coverage is found under the north-east facing (188.720 km2), south facing (167.398 km2), north-west facing (159.586 km2), north facing (138.712 km2), east facing (92.526 km2), and flat (40.754 km2). Hue Saturation Value (HSV) shader map (Fig. 1.3) of the study area is based on the elevation onto the HSV colour space. The mapping can be configured on the basis of intensity of colour. The gradient shader (Fig. 1.4) moderates the colour with elevation between the low elevation and the high elevation. The slope gradient in the study area varies from 700 m to 7100 m. The digital elevation model (DEM) in Figure 1.5 gives the bird’s eye view of the study area. The DEM clearly depicts that the altitude of the study area is divided into eight classes, i.e., 700-1500 m, 1500-2300 m, 2300-3100 m, 3100-3900 m, 3900-4700 m, 4700-5500 m, 5500-6300 m, and 6300-7100 m. According to the altitudinal variation, the study area is divided into two geographically regions, i.e., Greater Himalaya (3000-7000 m) and Lesser Himalaya (800-3000 m). The slope having an altitude from 6300- 7100 m comes under the perpetual snow clad mountains such as Introduction 11
Kedarnath Peak (4940 m) and valley glaciers (Chaurabari and Companion glaciers).
Why Management of Landslide is Necessary? The damages caused by landslides and related consequences cost more than US $ 1 billion, causing more than 200 deaths every year, which is about 30% of the total of such losses worldwide (Li, 1990). The maintenance expenditure on landslides and for keeping roads open to vehicular traffic costs the Government exchequer approximately ` 100 crore per year for the Himalayan region (Thakur, 1996). The destructive landslides can take away the entire chunk of fertile land, cluster of hamlets and dense forest down to the valley. Cloud burst is one of the natural disasters associated with the mass wasting triggering process in Himalaya. Several areas in Himalaya are severely damaged by cloud burst followed by debris flow, and consequently, the death of human and animal lives (Joshi and Maikhuri, 1997). The recent event of Nachani (La-Chekla) Munsiyari area of Pithoragarh and Bari, Balta and Devali (Almora) are current example of such type of activities.
The Problem Garhwal Himalaya is very sensitive towards slope failure in the entire Himalayan belt. Every year, large number of landslides occurs in this area. Landslide hazard zonation (LHZ) is a method to evaluate the risk where there is the potential for landslide occurrence. Landslide hazard zonation (LHZ) is classifying an area into several zones according to the probability of occurrence of landslides and related hazards in the particular area. Landslide hazard zonation (LHZ) is an effective technique by which a suitable index is taken into consideration to classify the landslide, mitigation planning and management. The study area is the small but important stretch of Himalaya which is very vulnerable towards landslides. Every year, during monsoon, landslides are frequent in this area which is responsible for the loss of human life and property. In the study area, five major river valley projects are running in the Mandakini valley under the two private companies: Lanco and Larsen & 12 Landslide Problems and Management in Himalaya
Tubro (L&T). These kind of river valley projects are not only destructing or deteriorating our mountain ecosystem but are also dangerous for the people living in the area. These types of activities may also trigger the mass movement and related problems in the near future. During the extensive field work of the area, some old and active landslide prone sites were studied. It is noted that some new vulnerable sites are formed most probably due to the anthropogenic activities such as hydroelectric project construction activities of Lanco and Larsen & Toubro (L&T), road cutting and house construction.
Past Tragedies 1. Madhyamaheshwar Ganga Basin In 1998, catastrophe caused due to landslides in Madhyamaheshwar Ganga and Kaliganga watersheds of Ukhimath area in the inner belt of Central Himalaya took place mainly due to the torrential downpour for more than seven days. As per the available reports, 107 people and 723 livestocks lost their lives along with a huge loss to the agricultural land, forest land and property. This calamity took place in the month of August 1998 in four events: (a) Raun village on 9.8.1998, (b) Uniyana village and its adjoining areas on 11.8.1998, (c) Kalimath area on 12.8.1998, and (d) village Pondar and Bhenti on 18.8.1998. Pondar village was situated approximately 500 m vertical distance from the riverbed on the right flank of the river Madhyamaheshwar Ganga, a tributary of river Mandakini. The huge slided mass glided from the opposite side (left side of the river) of Pondar village and buried the entire Pondar and Bhenti villages. Due to this phenomenon, a lake was formed on Madhyamaheshwar Ganga. On August 22, stray houses splintered like match boxes and gigantic swathes of raw earth and boulders gashed the green hillside of the Madhyamaheshwar valley where landslides of August 11 and 18 claimed 109 lives, wiped out three villages and destroyed a 80 m steel bridge. The landslide on August 18 when the spur of a hill on the left bank of the Madhyamaheshwar broke off and slided into the river, it killed 39 people and wiped out Bheti, Sem and Tongar villages (Pande, 1998). Introduction 13
Apart from natural factors such as the high level of seismicity in the region and the heavy rainfall, there were man-made factors such as deforestation, indiscriminate construction of roads and buildings, mining and excavation activities which have caused such havoc. It is observed that the proper and scientific management of landslide will certainly reduce the miseries of the community living in this region (Pande, 2006). 2. Phata Byung Area near Mandakini Valley On the fatal morning of 16 July 2001 (00.45 to 3.00 a.m.), heavy rainfall killed 27 persons and left several others homeless. The detailed survey of the area has revealed that 52.67 km2 of the area received very heavy precipitation. The cloudburst caused more than 200 landslides and disturbed the entire communication and transport network, and completely damaged the water supply system of the area, which paralyzed the life of this region. The losses assessed are: 27 human lives, 64 heads of cattle, 22 houses and 43 hectares of agricultural land. In all, 15 villages and 3924 people were affected. Memories of the 1998 tragedy in Okhimath, very close to this area, that took the lives of 103 persons are still fresh, although this time the tragedy occurred only in this part of Mandakini valley (Naithani et al., 2002).
Previous Work Done Mass movement is one of the most prominent disaster which act over the surface of the earth from the ancient time till this earth will remain. In the ancient time, our ancestor (homo sapiens) were also aware about the natural disasters, but they had no consciousness towards the understanding or knowing the causes of their happening and they were, therefore, afraid of it. But now,time is changing people/ researchers are interested in the study of disasters and want to manage or mitigate it in a sustainable manner. Landslide occurs due to natural processes as well as anthropogenic activities. Both of them are the triggering factors in the occurrence of landslides. We cannot control the natural process but we can manage our anthropogenic activity in relation to the local ecological and environmental conditions. 14 Landslide Problems and Management in Himalaya
Many researchers have worked in the field of landslide from the eighteenth century onwards and many studies were done and published in this field of interest. 1970s saw pioneering work in the field of landslide studies with the help of remote sensing techniques. However, the use of remote sensing data started in two phases; first, by using aerial photographs and latter by imagery from the satellite. Tanguay and Chagnon (1972) worked on the ‘Thermal Infrared Imagery at the St.- Jean-Vianney-Landslide’ by using aerial thermal IR imagery and 70 mm colour IR and black-and-white photographs on 1:5,000 scale and Alfoldi (1973) used aerial stereo-pairs at 1:20,000 scale to carry out the studies for Chelsea landslide. Gagnon (1975) studied ‘Land Hazards on Quick Clays of Eastern Canada’ and Sauchyn and Trench (1978) used 1:2,50,000 scale paper prints produced from Landsat 70 mm negative transparencies to map landslides in Colorado. Varnes (1984) presented a monograph of general review of various methods for landslide hazard zonation in the UNESCO publication titled ‘Landslide Hazard Zonation: A Review of Principles and Practice’. Jiang-Huang et al. (1984) carried out a study on the landslide of the Sale mountain in Dongxiang autonomous county, using remote sensing techniques. Their works were supported by Blanc and Cleveland (1968), Radbruch and Crowther (1973), Swanson and Dyrness (1975), Rodriquez et al. (1978), Nilsen et al. (1979), Veder (1981), Takei (1982), Kawakami and Saito (1984), Heara and Fultan (1986), Koirala and Watkins (1988), Brown (1990), McKean et al. (1991), Guerricho (1992), Leroi et al. (1992), Van Westen and Kruse (1992), Carrara et al. (1992), Dai et al. (2002), Ville et al. (2002), Carrara et al. (2003), Keim et al. (2003), Montety et al. (2006), Rastrepo et al. (2006), Schipper and Pelling (2006), and Xilin (2006), Mathew et al. (2007). All of them contributed in the quantitative as well as in the qualitative study of slope instability problems on the earth surface (Arya et al., 1994). In India, a large number of literature were published on the landslide. Some of these are discussed below: Choubey and Litoria, (1990) carried out a study on terrain classification and land hazard mapping in Kalsi Chakrata area, Garhwal Himalaya (Arya et al., 1994). Introduction 15
Gupta and Joshi (1990) studied on ‘Landslide Hazard Zoning using GIS Approach – A Case Study from the Ramganga Catchment, Himalayas’ (Arya et al., 1994). Mehrotra (1991) carried out the study on environmental development of Garhwal Himalaya with particular reference to landslide hazard zonation and efficacy of innovative control measures (Arya et al., 1994). Anbalagan (1992) used a quantitative approach for numerical rating called landslide hazard evaluation factor (LHEF) rating scheme. Arya et al. (1993) worked on geo-environmental study of landslides using remotely sensed and ancillary data in Tehri reservoir rim (Arya et al., 1994). Gupta et al. (1993) worked on the landslide hazard zonation (LHZ) maps. Kimothi et al. (1999) studied the slope activation and its impact on the Madhyamaheshwar and the Kaliganga sub-watersheds, Okhimath, using IRS-1C/1D data. Saha et al. (2002) examined the GIS based data integration for landslide hazard zonation in the Garhwal Himalayas in their study on GIS based landslide hazard zonation in the Bhagirathi (Ganga) valley, Himalayas. Bhandari (2004) did the landslide hazard zonation by dividing a territory into several zones, indicating the progressive levels of landslide hazard. The number of zones into which the territory is divided is fairly arbitrary. Landslide hazard zoning entails mapping of required details of all possible landslides and landslide-induced hazards. Graded landslide hazard maps are required by, among other, developmental planners as tools for efficient management of land. Landslide hazard maps are also essential to assess damage potential, and to quantify risks. The scientific forecasting of a landslide for early warning finds its first clue in the landslide hazard map of the area. Saha et al. (2005) attempted an approach for GIS-based statistical landslide susceptibility zonation with a case study in the Himalayas. 16 Landslide Problems and Management in Himalaya
Landslide susceptibility zonation (LSZ) is necessary for disaster management and planning development activities in mountainous regions. A number of methods, viz., landslide distribution, qualitative, statistical and distribution-free analysis have been used for the LSZ studies. In his work, he applied two methods, the Information Value (InfoVal) and the Landslide Nominal Susceptibility Factor (LNSF) methods that are based on bivariate statistical analysis. Relevant thematic maps representing various factors (e.g., slope, aspect, relative relief, lithology, buffer zones along thrusts, faults and lineaments, drainage density and land cover) that are related to landslide activity have been generated using remote sensing and GIS techniques. The LSZ derived from the LNSF method has been compared with that produced from the InfoVal method and the result shows a more realistic LSZ map from the LNSF method which appears to conform to the heterogeneity of the terrain. Rautela (2005) explained the role of vegetal covers in reducing and even checking the pace of mass wastage. In order to avert mass movement in the event of exceptionally high rainfall event, the local people resorted to the maintenance of specially designed stone-lined waterways in the upper reaches of the critical locations. These structures drained the excess water directly into the mainstream and helped in maintaining pore water pressures within the threshold limits and avoiding mass movement. Kimothi et al. (2005) worked on landslide problems in ancient religious Uttarkashi town of Garhwal Himalayas. They studied the upper Lesser Himalayan zone of Garhwal Himalayas which has a long history of various kinds of disasters, the recent being the September 2003 Varunavat Parvat landslides. Haritashya et al. (2006) studied the hydrological importance of an unusual hazard in a mountainous basin. The Bhagirathi River, a glacial fed stream of the Gangotri Glacier, is the principal source of the Ganges river system. The upper part of the basin lies in the high altitude region of the Garhwal Himalayas and is extensively covered by glaciers. They provided hydro-meteorological insight into a severe storm that produce unusual high rains in June 2000 in the uppermost part of the Bhagirathi Introduction 17
River. This storm was concentrated upstream of Gangotri town and triggered landslides/rockslides at several locations between the glacier snout and Gangotri town. One of the major rockslide blocked the Bhagirathi River at Bhujbas, about 3 km downstream of the Gangotri Glacier snout, creating an artificial lake at this location. High stream flow in the river, generated by rapid runoff response from mountain slopes along with melt runoff from the glacier, quickly increased the level of water stored in the artificial lake. Till now, a large volume of work has been done by the Indian researchers on the landslides, but the application on the ground is still remaining untouched. In a country like India, making of rules, regulation and policies are easy but applying them is a very difficult task.
1.1 Objectives
The study focuses on the following seven major objectives: 1. To detect, identify and map active and old landslides through the analysis of remote sensing satellite data, e.g., ASTER, etc. 2. To prepare various thematic maps from satellite data for lithology, landforms, structural lineament, land use/land cover, soil, drainage, slope, settlement and road network. 3. To collect ground truth data related to landslides and various natural resource related themes. 4. To integrate various thematic maps through GIS and generate landslide hazard zonation map and to prepare a landslide hazard management map. 5. To prepare landslide inventory showing villages prone to landslides. 6. To study the socio-economic impact of the landslides on the communities inhabiting the areas prone to landslides. 7. To suggest awareness and information disseminating measures among the local population to minimize the impact of future landslides. 18 Landslide Problems and Management in Himalaya
1.2 The Study Area
In India, Himalaya the highest mountain range of the world, extends between 72º 30' to 97º 26' E and 26º 26' to 37º 0' N in an arc shape. Garhwal Himalaya, a part of Central Himalaya, is also known as the “Valley of Gods”. The region have many beautiful/splendid places and important Hindu religious shrines such as Kedarnath, Trijuginarayan, Guptkashi, Okhimath, Madhyamaheshwar, Tungnath, Rudranath, Gopeshwar, Ansyia Devi, etc. More than three-fourth part of the Central Himalaya are covered by the Garhwal Himalaya which includes many of the high altitudinal snow covered peaks and glaciers. Most of the physiographic structures/landforms present in the Garhwal Himalaya are sculptured/formed due to the action of glacial activities in the northern and fluvial activities in southern portion. Geographically, the study area lies between the 79º 00' to 79º 25' E and 30º 20' to 30º 45' N and covers an area of 1400 km2. The study area is situated in parts of Rudraprayag and Chamoli districts in Mandakini valley on the upstream of Agastmuni. The lower catchment of Madhyamaheshwar and Kaliganga rivers also fall in the study area. These were worst affected during August 1998 landslides. This region has a great importance not only as a tourist but also as a sacred religious place. Tourists and pilgrims visit this place during summer-monsoon season, which is also the vulnerable period for the occurrence of most of the landslides. The frequency of landslide in the Garhwal Himalaya varies from one place to another, depending on the underlying structures, physiographic setting and anthropogenic changes taking place (Joshi et al., 2001). Roads are affected by slope instability due to unplanned engineering construction. The landslides are frequent during the monsoon season of the year. Every year, the road network in the region registers damages at various locations (Joshi et al., 2001). Also, this area is seismically very active and is more prone/vulnerable to landslides or landslides related disasters. So, there is a need to make a well planned strategy for the management of the disaster in the future. Introduction 19
Fig. 1.6: Location Map of the Study Area
Climatic and Physiographic Condition Climatic conditions are diverse and vary according to the altitudes and are governed by monsoon in the region. The altitude is extended from 670 m to 6000 m (snow-covered area). The high peaks (> 3000 m) are covered by perpetual snow. Below this altitude, snow lasts for three to four months in winter and temperature falls below freezing point. Rainy season is restricted between mid-June to mid-September and receives > 60% rain of mean annual rainfall of about 1734 mm. In the study area, the maximum rainfall recorded at Ukhimath is 2257 mm and minimum at Rudraprayag, i.e., 1210 mm (Joshi et al., 2001).