Springer Natural Hazards Sujit Mandal Ramkrishna Maiti Semi-quantitative Approaches for Landslide Assessment and Prediction Springer Natural Hazards More information about this series at http://www.springer.com/series/10179 Sujit Mandal • Ramkrishna Maiti Semi-quantitative Approaches for Landslide Assessment and Prediction 123 Sujit Mandal Ramkrishna Maiti Department of Geography Department of Geography and Environment Raja N.L. Khan Women’s College Management Paschim Medinipur, West Bengal Vidyasagar University India Paschim Medinipur, West Bengal India ISBN 978-981-287-145-9 ISBN 978-981-287-146-6 (eBook) DOI 10.1007/978-981-287-146-6 Library of Congress Control Number: 2014951664 Springer Singapore Heidelberg New York Dordrecht London © Springer Science+Business Media Singapore 2015 This work is subject to copyright. 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Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Preface In the present time, our natural environment is frequently associated with a number of destructive hazards such as flood, earthquake, storm surge, drought, landslide, volcanic eruption, etc., worldwide. All these environmental problems may bring about a tremendous change in the geomorphic system over the land surface and may also divide a system into a number of subsystems. It is the task of Physical Geographers to study natural hazards and their destructive impacts over the earth’s surface in a scientific way. Here, we studied in detail geologic, geomorphic, and hydrologic processes responsible for landslides in a representative mountain watershed, Shivkhola of Darjiling Himalaya, where landslides are very much active and have destroyed communication lines, settlements, and tea estates. A quantita- tive understanding of all the triggering landslide inducing parameters can provide a clear vision of the changes and evolution of landforms. The aim of this book is to provide an integrated knowledge and understanding of the application of semi- quantitative approaches in evaluating various landslide triggering factors and assessment of landslide susceptibility as well as landslide risk, which can help planners and policymakers to check the magnitude of landsliding in mountain terrains. The concerned area, Shivkhola, is badly affected by slope instability jeopar- dizing the economy and social systems; taking a toll of lives, lands, and properties; promoting road blockage and hampering flow of tourists; destroying pipelines of water; and causing subsidence of road and rail cut benches. The effects are con- veyed over a long distance, both upslope and downslope, by disruption of transport and hydrological systems and thus invites instability into both physical and social systems. Most landslides of this trouble-torn district of Darjiling are concentrated in this area where most of the torrential jhoras (Hill Streams) at their upper catchments develop a potential sinking zone, and the Hill Cart Road and Narrow gauge Rail when traversing through these zones invite catastrophic slides. The present work tries to identify the zones of potential slides by investigating into the systematic interaction among the number of prominent physical and human triggering factors. The geotechnical attributes, viz., major principal stress, minor principal stress, normal stress, shear stress, angle of internal friction, angle of rupture, cohesion, v vi Preface shear strength, and safety factor of the Shivkhola watershed have been determined using the Tri-axial Compression Test from the geotechnical laboratory, Geological Survey of India (Kolkata). There is every possibility for the generation of geo- morphic thresholds for initiation of slides due to hydrologic factors. Thus debris slide occurs and the slope on scar face is reduced to that of repose angle to attain temporary stability through internal feed back in a process of homeostatic adjust- ment. Remote Sensing and GIS-based Landslide Susceptibility Zone Map reveals that Paglajhora, Shiviter, Gayabaria, and Tindharia are more susceptible in terms of slope instability. The prepared Landslide Hazard Risk Map also states that Tin- dharia, Gayabari, Shiviter, and Paglajhora are prone to landslide risk because of prevalence of risk elements such as road network and settlements. As most land- slides occur along Hill Cart Road (NH-55), and a huge amount is spent on Post Slide Management, an attempt toward pre-slide management of the susceptible areas has to be introduced with immediate effects with less efforts and investment. A sector-wise job assignment has to be made for regular supervision of the slope stability and a serious drive for pre-slide management of potential slope failure zones should be introduced; these should be considered as emergency as in post- slide condition. In such a highly instable region the protection of slope and soil is a great challenge through rational use of these resources for harnessing greater utility over a long time. Midnapore, India, August 2014 Sujit Mandal Ramkrishna Maiti Acknowledgments It is a moment of jubilance and euphoria to me because of the candid endeavor so far made, be it small or large in this book, in illuminating the unexplored domain of knowledge in “Semi-quantitative Approaches for Landslide Assessment and Pre- diction”. We would like to pay our humble regards, indebtedness, and immense sense of gratitude to our respected Teacher, Professor Late Subhas Ranjan Basu, Ex-Head of the Department Geography, University of Calcutta, who had shared with us a lot of his experiences, suggestions, and encouragement till his last breath so that we always bear his fragrance of affection and bliss showered on us. His prudent direction, all sorts of support, and sleepless effort for preparation of this book can never be forgotten. We also acknowledge the financial support of University Grant Commission, New Delhi, through granting a research project that helped in data collection and subsequent analysis involved in this research work. We would like to express our appreciation and thanks to Mr. Manik Das Adhikari, Project Fellow, IIT, Kharagpur for his immense support throughout the work. We wish to record our sincere gratitude to all the officials of all Departments, including Geological Survey of India (GSI), Kolkata, Tea Research Centre, Department of Agriculture, Department of Forest of Kurseong, Government of West Bengal who had provided valuable information in the study area. Thanks are due to Department of Geography and Environment Management, Vidyasagar University, Paschim Medinipur, West Bengal, India, and the authority of Raja N.L. Khan Women’s College, Paschim Medinipur, W.B., India and especially the department of Geography and Zoology for offering logistic support and fulfilling all sorts of lack occurred in that institution for involvement in this research work. It is difficult for us to fully express our gratitude to our families, parents, brothers, sisters, relatives, and students for their sacrifice, constant love, cordial affection, and inspiration throughout the work. Midnapore, India, August 2014 Sujit Mandal Ramkrishna Maiti vii Contents 1 Introduction......................................... 1 1.1 Key Concepts on Landslide . 1 1.2 A Brief Account of Some Destructive Landslides Occurrences. 3 1.3 Relevance of the Landslide Study. 3 1.4 Landsliding in Darjiling Himalaya . 17 1.5 Mechanism and Causes of Landslides . 23 1.6 Types and Classification of Landslide . 30 1.7 Objectives of the Present Work . 34 1.8 Applied Methodology . 35 1.9 Data Used for Quantitative Study on Landslide . 39 1.10 Existing Literature on Landslide Inducing Parameters . 39 1.11 Slope Stability Models . 43 1.11.1 Hydrological Models and Slope Stability. 44 1.11.2 Landslide Susceptibility Zonation Models Concept . 44 1.12 Study on Landslide Management . 48 References . 50 2 Geo-spatial Variability