Surface Environments and Human Interactions: Reflections from Asia 9819701112, 9789819701117

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Rajat Mazumder Rajib Shaw   Editors

Surface Environments and Human Interactions Reflections from Asia

Surface Environments and Human Interactions

Rajat Mazumder  •  Rajib Shaw Editors

Surface Environments and Human Interactions Reflections from Asia

Editors Rajat Mazumder Department of Applied Geosciences German University of Technology in Oman Halban, Muscat, Oman

Rajib Shaw Graduate School of Media and Governance Keio University Fujisawa, Kanagawa, Japan

ISBN 978-981-97-0111-7    ISBN 978-981-97-0112-4 (eBook) https://doi.org/10.1007/978-981-97-0112-4 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore Paper in this product is recyclable.

Preface

Surface environment is a manifestation of complex phenomena of natural and human-induced actions. While there is a regular geological process of the earth, the climate phenomena make additional changes to that. The result is the natural hazards and events which we see around us in mountain, land, sea, and rivers. Human activities, especially unplanned growth, have even additional pressure to this complex natural changes. Population pressure in Asia is one of the key drivers to that. To address this complex phenomenon, this book presents a series of analysis from Hindu Kush Himalayan Mountain range to major rivers and delta regions. The chapters make detailed data- and evidence-based analysis to show the interlinkages of the complex mechanism and suggest some policy interventions as well as technology evolution. The book is organized into 12 chapters, each of which will emphasize the use of advanced analysis on surface environment-related issues. Each chapter is written by scholars and/or practitioners with acknowledged expertise in the field and with adequate experience of working in Asian region. The book is intended to cover different dimensions of surface environment. Let us end with a personal note. Both the editors started their journey in geology and were classmates in undergraduate and postgraduate studies. While RM stuck to the original subject on geology, RS moved to more environment, climate change, and disaster risk reduction areas. A recent conversation between two of us found that there is a strong connection to geology, surface environment, climate change, and built environment. Therefore, we decided to start this book as the first step to understand geology and society relationship. We are thankful to several of our mentors, and we would like to dedicate this book to Professor Alok K. Gupta of University of Allahabad, India, and Professor Makoto Arima of Yokohama National University. Professor Gupta and Arima helped us in shaping our research career, and we are ever indebted to them for all the learnings. We sincerely hope and believe that this book will connect the core geology-­related research to more society and policy-related research. We will be happy if the readers find the book useful. Halban, Muscat, Oman Fujisawa, Kanagawa, Japan 

Rajat Mazumder Rajib Shaw v

About the Book

There exists a complex interplay between Earth surface processes (erosion and sedimentation) and human interactions. Intensive as well as extensive research has been undertaken to infer modern sedimentation processes and the mode of stratigraphic sequence building. However, the effort to understand the influence of sedimentation processes on society and the human impact on sedimentation is long overdue. There exists one special issue devoted to these surface environments and human interplay. There is no book/edited volume on this topic. This is a new upcoming multidisciplinary research field that is beyond the scope of leading traditional earth and environmental science journals. To fill in the prodigious gap in knowledge base, this book will include in-depth reviews as well as new data-based case studies from Asia, involving multidisciplinary research. This book covers case studies of risk management of various hazards and risk management systems at regional, national, and local levels. It aims to propose a comprehensive approach to reduce future risks by collaborating with various stakeholders and preparing for the most effective responses toward complicated hazards, minimizing social damage.

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Contents

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 arth Sciences and Society (ESS)����������������������������������������������������������    1 E Rajat Mazumder, Rajib Shaw, and Sreelekha Mazumder

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Land Cover, Land Use Change and Its Implication to Disasters in the Hindu Kush Himalayan Region ��������������������������������������������������    7 Basanta Raj Adhikari, Suraj Gautam, Til Prasad Pangali Sharma, and Sanjaya Devkota

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 patio-Temporal Dynamics of Land Use Land Cover and S Its Impact on Flood-­Prone Drainage Basin of River Swat, Eastern Hindukush����������������������������������������������������������������������������������   29 Haseeb-Ur Rahman, Abdullah Khan, Atta-Ur Rahman, and Rajib Shaw

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 roactive Adaptation to Climate Change in the Mekong Delta P in Vietnam: A Socio-­ecological Approach����������������������������������������������   41 Huy Ngoc Ha, Rajib Shaw, Thi My Thi Tong, and Thi Tuyet Tran

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Surface and Underground Water Challenges in the Delta Region of Bangladesh������������������������������������������������������������������������������   65 Md. Hosenuzzaman, Mohammad Golam Kibria, and Md. Anwarul Abedin

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Human Interactions and Earth Processes: Case Studies of Landslide-Generated Tsunamis in Indonesia ����������������������������������   95 Farah Mulyasari and Harya Dwi Nugraha

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Study of Lithofacies, Radar Facies and Satellite Images of the River Bars: Implication for Regulation Structures on the Tista River of Eastern Himalaya������������������������������������������������  105 Kausik Ghosh and Tapan Chakraborty

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Interplay of Sediment Transport and Urbanization in Wadi Environments ����������������������������������������������������������������������������  139 E. Holzbecher, M. Ebeid, A. Hadidi, and E. Agirbas

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A Practical Approach to Understanding Urban Ground Conditions: A Case Study from the City of Varanasi, India����������������  153 Ashok Shaw, Martin Smith, Prerona Das, Mrinal Kanti Layek, Probal Sengupta, and Abhijit Mukherjee

10 S  usceptibility Modelling for Building Climate Resilience in Cities: The Kuala Lumpur Multi-Hazard Platform for Disaster Risk Reduction��������������������������������������������������������������������  177 Joy Jacqueline Pereira, Ng Tham Fatt, Nurfashareena Muhamad, Elanni Affandi, and Julian Hunt 11 A  nalysis of Flood Intensifying Condition and Associated Socio-Economic Damages: A Case Study from Undivided Paschim Medinipur����������������������������������������������������������������������������������  195 Kishor Dandapat and Uday Chatterjee 12 F  uture Perspectives of Surface Environment and Human Interactions�������������������������������������������������������������������������  223 Rajib Shaw and Rajat Mazumder

Editors and Contributors

About the Editors Rajat Mazumder  received his M.Sc. in applied geology in 1991 from the University of Allahabad, India, and his Ph.D. from Jadavpur University, India, in 2002. He was a Postdoctoral Fellow of the Japan Society for the Promotion of Science (JSPS) at Yokohama National University (2002–2004), Alexander Von Humboldt Foundation (2005–2006) at Munich University, Germany, and was a recipient of JSPS short-term invitation fellowship for experienced researchers in 2008. He taught sedimentary petrology, mineralogy, and Precambrian stratigraphy at Asutosh College, University of Calcutta (1999–2002), Indian Institute of Technology Roorkee (2006), and was an Associate Professor of Geology at the Indian Statistical Institute (2006–2013). He was a Research Fellow at the University of New South Wales, Australia (2012–2014) and an Associate Professor at Curtin University, Malaysia (2015–2018). Currently, he is an Associate Professor at German University of Technology in Oman. He was one of the global coleaders of UNESCO-IGCP 509 research project (2005–2009) on the Paleoproterozoic supercontinent and global evolution. He is currently editorial board member of Geology (Geological Society of America) and Sedimentology (journal of the International Association of Sedimentologists, Europe). His research is mostly focused on the Earth’s surface processes during its early history. Rajib Shaw  is a Professor in Graduate School of Media and Governance of Keio University, Japan. He is the Cofounder of a Delhi (India) based social entrepreneur startup Resilience Innovation Knowledge Academy (RIKA) and RIKA Institute. He is the Cochair of the United Nations Asia-Pacific Science Technology Advisory Group (AP-STAG) and was CLA for IPCC’s 6th Assessment Report. He is the recipient of the prestigious “Pravasi Bharatiya Samman Award (PBSA)” in 2021 for his contribution in education sector. He also received United Nations Sasakawa Award in 2022 for his lifetime contributions in the field of disaster risk reduction. He is the Editor-in-Chief of Progress in Disaster Science, a high impact factor Elsevier journal. He has published 66 books and over 450 research papers. More about his work can be found in www.rajibshaw.org. xi

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Contributors Abdullah  Department of Geography and Geomatics, University of Peshawar, Peshawar, Pakistan Md. Anwarul Abedin  Laboratory of Environment and Sustainable Development, Department of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh Basanta  Raj  Adhikari  Department of Civil Engineering, Pulchowk Campus, Institute of Engineering, Tribhuvan University, Kathmandu, Nepal Elanni  Affandi  Department of Geology, University of Malaya, Kuala Lumpur, Malaysia E. Agirbas  Department of Urban Planning and Architecture, German University of Technology in Oman (GUtech), Muscat, Sultanate of Oman Tapan  Chakraborty  Geological Studies Unit, Indian Statistical Institute, Kolkata, India Uday Chatterjee  Department of Geography, Bhatter College, Dantan (Vidyasagar University), Paschim Medinipur, West Bengal, India Kishor  Dandapat  Department of Geography, Seva Bharati Mahavidyalaya, Kapgari (Vidyasagar University), Jhargram, West Bengal, India Prerona Das  Department of Geology, North Eastern Hill University, Shillong, India Sanjaya  Devkota  Forum for Energy and Environment Development (FEED) P. Ltd., Lalitpur, Nepal M. Ebeid  Department of Urban Planning and Architecture, German University of Technology in Oman (GUtech), Muscat, Sultanate of Oman Ng  Tham  Fatt  Department of Geology, University of Malaya, Kuala Lumpur, Malaysia Suraj Gautam  Institute of Himalayan Risk Reduction, Lalitpur, Nepal Forum for Energy and Environment Development (FEED) P. Ltd., Lalitpur, Nepal Kausik  Ghosh  Department of Geography, Faculty of Science, Vidyasagar University, Midnapore, India A. Hadidi  Department of Applied Geosciences, German University of Technology in Oman (GUtech), Muscat, Sultanate of Oman Huy  Ngoc  Ha  Vietnam Institute of Economics, Vietnam Academy of Social Sciences, Hanoi, Vietnam E.  Holzbecher  Department of Applied Geosciences, German University of Technology in Oman (GUtech), Muscat, Sultanate of Oman

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Md.  Hosenuzzaman  Laboratory of Environment and Sustainable Development, Department of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh Julian Hunt  Trinity College, University of Cambridge, Cambridge, UK Mohammad  Golam  Kibria  Laboratory of Environment and Sustainable Development, Department of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh Mrinal  Kanti  Layek  Department of Civil Engineering, Changwon National University, Gyeongsangnam-Do, South Korea Rajat  Mazumder  Department of Applied Geosciences, German University of Technology in Oman, Muscat, Sultanate of Oman Sreelekha  Mazumder  Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan Nurfashareena Muhamad  Southeast Asia Disaster Prevention Research Initiative (Seadpri), Universiti Kebangsaan Malaysia, Selangor, Malaysia Abhijit  Mukherjee  Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, India School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India Farah  Mulyasari  Center for Sustainable Geoscience and Outreach (CSGO), Universitas Pertamina, Jakarta, Indonesia Harya Dwi Nugraha  Center for Sustainable Geoscience and Outreach (CSGO), Universitas Pertamina, Jakarta, Indonesia Joy  Jacqueline  Pereira  Southeast Asia Disaster Prevention Research Initiative (Seadpri), Universiti Kebangsaan Malaysia, Selangor, Malaysia Atta-Ur  Rahman  Department of Geography and Geomatics, University of Peshawar, Peshawar, Pakistan Haseeb-Ur Rahman  Institute of Space Technology, Islamabad, Pakistan Probal  Sengupta  Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, India Til  Prasad  Pangali  Sharma  Central Department of Geography, Tribhuvan University, Kathmandu, Nepal Ashok  Shaw  Ontario Agricultural College, School of Environmental Sciences, University of Guelph, Guelph, ON, Canada Rajib Shaw  Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan

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Martin Smith  British Geological Survey, Lyell Centre, Research Avenue South, Edinburgh, UK Thi My Thi Tong  Vietnam Institute of Economics, Vietnam Academy of Social Sciences, Hanoi, Vietnam Thi  Tuyet  Tran  Institute of Human Geography, Vietnam Academy of Social Sciences, Hanoi, Vietnam

Chapter 1

Earth Sciences and Society (ESS) Rajat Mazumder, Rajib Shaw, and Sreelekha Mazumder

Abstract  Human-surface environment interaction refers to how humans interact with the environment to fulfill their requirements and how the environment responds to these interactions. Tectonic and climatic forces, when combined with the action of wind, water, glacier, and ocean currents on the Earth’s surface, landforms evolve. Understanding the surface processes and their rate of changes is extremely important to infer natural system behavior, variability, and resiliency, for predicting future changes, risk assessment, and mitigation of natural hazards. Humans also affect the Earth’s surface processes and climate through emissions and modification of the land surface through agriculture and urbanization. The interplay between the Earth’s surface processes and human interactions is therefore at the core of many global economic, environmental, and security issues. Notwithstanding this, our understanding of the Earth’s surface environment and human interactions is inadequate. There are inherent problems in Earth Science communication. We conclude that active collaboration between Earth and Social scientists is an essential prerequisite for preventing the loss of major geoscientific concerns among wider social, economic, and political concerns. Keywords  Surface environments · Human interactions · Sustainability · Resiliency · Earth Sciences

R. Mazumder (*) Department of Applied Geosciences, German University of Technology in Oman, Muscat, Sultanate of Oman e-mail: [email protected] R. Shaw · S. Mazumder Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan e-mail: [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Mazumder, R. Shaw (eds.), Surface Environments and Human Interactions, https://doi.org/10.1007/978-981-97-0112-4_1

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1.1 Introduction The Earth’s surface that separates the atmosphere from the lithosphere produces a global topography. The topography is strongly influenced by the tectonic and climatic processes. The rocks are disintegrated into sediment through weathering and erosion, followed by transportation and deposition of sediment, primarily from the continents to the oceans (Dietrich and Perron 2006; Leeder 2011; Hay 1998; Hayes et al. 2021; Fig. 1.1). The controls on this flux and its temporal evolution are among one of the most important aspects of Earth Sciences. This holistic understanding of the Earth’s surface environments requires multidisciplinary research, involving geomorphology, sedimentology, stratigraphy, tectonics, paleoclimate, and large-scale geochemical cycling (Carter et al. 2002; Dietrich and Perron 2006; Sinclair 2014; Hayes et al. 2021). Surface environments have strong influences on the society. Pollution and climate change are challenging for humans around the globe (Shindell et  al. 2012; Masselot et al. 2018; Kumar 2021). Frequent shift in river course and strong earthquake often causes many injuries and the loss of lives (Molla et al. 2019; Tang et al. 2017; Yeow et al. 2020; Das and Samanta 2022). Extensive research on environmental impact on human society has been done in the past and is being undertaken in many countries. On the contrary, the impact of human society on surface environments is a relatively new but rapidly emerging field of research (Liverman and Cuesta 2008; Owen et  al. 2020; Tortell 2020). The surface environments are impacted by human society in many ways: pollution, overpopulation, burning fossil fuels, and deforestation. These changes, in turn, induce climate change, soil erosion, poor air quality, and poor drinking water. In many Third World countries, poverty,

Fig. 1.1  Major modes of sediment delivery from continents to oceans (after Hay 1998)

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rapid population growth, and environmental degradation can turn natural hazards into major disasters (Owen et al. 2020; Tortell 2020; Wijkman 2021; Capello et al. 2023). Herein we discuss the problems in Earth Science communication and the need for effective communication with society in order to convey major concerns of the Earth scientists within major socio-economic and political concerns.

1.2 Earth Sciences and Society (ESS) The 2030 Agenda for Sustainable Development that was defined in the United Nations General Assembly in September 2015 was adopted by all United Nations member states. There were 17 sustainable development goals (SDGs; Fig. 1.2) recommended for social inclusion, environmental protection, and economic growth in all parts of the globe (United Nations 2015; Gill 2017; Gill and Smith 2021; Capello et al. 2021, 2023). As Earth scientists study the physical, chemical, and biological parameters that influence our planet on different scales and dimensions through time, they are very well qualified and can significantly contribute to investigate the past to predict the future, a sustainable future. As pointed out by Stewart (2016), excessive use of the Earth’s natural resources has adverse consequences on “our survival, sustaining the economy, safeguarding national security, and maintaining the natural environment”. As Tortell (2020) mentioned, the past five decades reveal “significant triumphs of environmental protection, but also notable failures”, that ultimately led to deterioration of the Earth’s natural systems (Fig. 1.2). Earth scientists are trained in a range of practical skills and offer flexible mindsets, and hence are advantageous in developing a more sustainable environmental practice (Stewart 2016; Capello et  al. 2023). Notwithstanding this, most Earth

Fig. 1.2  United Nation’s SDGs for 2030 (after United Nations 2015; Gill 2017; see also Capello et al. 2021)

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scientists have very little involvement in the growing societal shift toward sustainable development (Stewart 2016; Tortell 2020; Rodrigues et  al. 2023). There are problems associated with Earth Science communication (Rodrigues et  al. 2021, 2023). Unlike researchers in medicine, health, or climate science, Earth scientists generally have less opportunity of engagement with society (Rodrigues et al. 2021). Although modern scientific approaches and technologies, designs based on empirical experience and laid on didactical approaches are frequently used in Earth Science communications, lack of societal involvement is the major impediment to disseminate the knowledge. It is of paramount importance to establish a commitment between society and Earth scientists; common public should not be treated as a “single entity with a knowledge deficit” (Rodrigues et al. 2023). Geoscience communication is one of the very modern branches of Earth Sciences (Liverman 2008). It is supposed to incorporate social science, behavioral science, and science communication. However, it still lacks a clear and formal definition. To understand the complexity of contemporary human–environment relations, Earth scientists must go for efficient collaboration with the social sciences. Although Earth System Science is supposed to bridge natural science and social science (Butz 2004), the social aspect is under focused. Stewart (2016) pointed out that “the more effectively a potential threat is made public by the scientist, the more readily the scientific message becomes normalized into the complex and chaotic discourses of daily life”. Otherwise, there is every chance that important scientific concerns get lost within wider social, economic, and political concerns. Earth scientists thus need to be more society oriented, and an effective communication between Earth scientists and society is an essential prerequisite for a sustainable Earth. To encourage active research collaboration between Earth and social scientists with a focus on sustainability and how Earth Scientists can help to solve the global challenges facing modern society, the Geological Society of London has launched an open access journal Earth Science, Systems and Society (ES3; https://www.escubed.org/journals/ earth-­science-­systems-­and-­society).

1.3 The Asian Perspective Asia (and Oceania) currently holds the largest population of the world and is vulnerable to natural disasters. Around 80% of people lost their lives globally in this region. It is thus extremely important to discuss natural hazard-related issues through multidisciplinary research involving geoscientific, social, and technical approaches. The Asia Oceania Geosciences Society (AOGS) was established in 2003 to promote application of geosciences for mankind with emphasis on Asia and Oceania (https://www.asiaoceania.org/society/public.asp?page=home.asp). The AOGS has partnership with several renowned scientific bodies, including the American Geophysical Union, Japan Geoscience Union, International Union of Geodesy and Geophysics, Society of Exploration Geophysicists, European Geoscience Union, etc. The AOGS has two scientific research publications

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(Geoscience Letters and Advances in Geosciences). However, more research is urgently required to address issues related to surface processes, natural hazards, and human interaction. In this book, we have attempted to present several case studies on surface processes and human interactions from an Asian perspective.

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Chapter 2

Land Cover, Land Use Change and Its Implication to Disasters in the Hindu Kush Himalayan Region Basanta Raj Adhikari, Suraj Gautam, Til Prasad Pangali Sharma, and Sanjaya Devkota Abstract  The 3500  km long Hindu-Kush Himalaya (HKH) region is one of the dynamic regions of the world. Natural and human-induced hazards impose threats to lives and infrastructures in this region. This region has four of the five most crucial yet vulnerable water towers in Asia. The ten major river basins in the HKH have a population of around 1.9 billion in the year 2015 with about 240 million in the mountains and hills. The existing geo-climatic characteristics of the region, rapidly increasing urbanization, environmental degradation, anthropogenic activities, and socioeconomic conditions, are increasing citizens’ exposure to and risk from natural hazards and resulting in more frequent, intense, and costly disasters. Moreover, this region is extensively experiencing the negative effect of climate change, i.e., glacier melting forming glacial lakes. The formation of glacial lakes due to permafrost melting poses a high threat of Glacial Lake Outburst Flood (GLOF). This region has already witnessed a number of GLOF events in recent decades. It is found that one large event, i.e., GLOF can change the whole mountain landscape along with land use and land cover (LULC) changes. Similarly, the existing topography, roads excavated at the higher gradient, and the agricultural lands on the steeper slopes have been the hotspots for the large number of landslides There is a significant contribution of anthropogenic activities for LULC change. Therefore, this study aims to analyze the changing pattern of LULC due to human interferences B. R. Adhikari (*) Department of Civil Engineering, Pulchowk Campus, Institute of Engineering, Tribhuvan University, Kathmandu, Nepal e-mail: [email protected] S. Gautam Institute of Himalayan Risk Reduction, Lalitpur, Nepal Forum for Energy and Environment Development (FEED) P. Ltd., Lalitpur, Nepal T. P. P. Sharma Central Department of Geography, Tribhuvan University, Kathmandu, Nepal S. Devkota Forum for Energy and Environment Development (FEED) P. Ltd., Lalitpur, Nepal © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Mazumder, R. Shaw (eds.), Surface Environments and Human Interactions, https://doi.org/10.1007/978-981-97-0112-4_2

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and natural processes. This study will be helpful to understand the mountain dynamics and its relationship with increasing disasters in the HKH region. The number of pixels with a population density of over 100,000 per square KM was 122 in 2000, which was increased to 960 pixels in 2020. Overall, the data shows that the population density has increased in recent years in the HKH region. The HKH region had almost 20.85% (4075 of 19,547) major disaster events recorded in the past 32 years (between 1990 and 2022) in the Em-DAT global database, with death tolls of more than 28.71% in the region. Keywords  LULC · Human · HKH · Landslides · Climate change

2.1 Introduction The Hindu Kush Himalaya (HKH) spreads about 3500 km across eight countries: Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan, covering an area of almost 4.2 million sq. Km. It is one of the greatest mountain systems in the world. Similarly, this region consists of ten major river basins where more than 1.9 billion people are using the water resources (Sharma et al. 2019). The region is also known for its rich biodiversity, unique cultural heritage, and important water resources. It has a high concentration of snow and glaciers outside the polar region also known as Third Pole and it is a freshwater tower of South Asia. The region is also characterized by its fragile geology, geo-climatic conditions, average socio-economic conditions, rapidly increasing urbanization, and increased anthropogenic activities because of which the citizen’s exposure toward the disasters has been more frequent and intense resulting in costly disasters (Vaidya et al. 2019). The population density in the HKH region varies greatly across different areas, with some areas being densely populated while others are sparsely populated. Though this region is urbanizing rapidly, still a large portion of the population in the HKH lives in rural areas, practicing subsistence agriculture and traditional livelihood (Qasim et al. 2011). The HKH region has one of the most dynamic, fragile, and complex mountain systems in the world as a result of tectonic activity and rich biodiversity of climates, hydrology, and ecology (Lambin et al. 2003; Rana et al. 2021). Further, the central and eastern sub-region of this HKH receives more than 80% of annual precipitation during the summer monsoon season (Sabin et al. 2020). The HKH region is also home to ten major river basins and is often referred as the “water tower for Asia” as summarized in Table 2.1 (Scott et al. 2019). The region gets a bulk amount of precipitation from the East Asian and Indian monsoon system during the summer months of June to September (Singh and Ranade 2010; Yihui and Chan 2005). Similarly, the region also receives winter precipitation often called western disturbances from the Mediterranean region (Dimri et al. 2015). Alongside this, the events of cloudbursts, snowstorms, flash floods, and landslide blockages are also the reasons for flooding in the HKH region. Studies

2  Land Cover, Land Use Change and Its Implication to Disasters in the Hindu Kush… Table 2.1  River basins in the HKH region

S.n. 1

River basin Amu Darya

2

Brahmaputra

3

Ganges

4 5 6

Indus Irrawaddy Mekong

7 8 9 10

Salween Tarim Yangtze Yellow

9

Countries Afghanistan, Tajikistan, Turkmenistan, and Uzbekistan China, India, Bhutan, and Bangladesh India, Nepal, China, and Bangladesh China, India, and Pakistan Myanmar China, Myanmar, Laos, Thailand, Cambodia, and Vietnam China, Myanmar, and Thailand Kyrgyzstan and China China China

have found that the ongoing climate change has highly impacted the HKH (Dhimal et al. 2021) region which has resulted in frequent and intense disaster loss in the region. As a result of which, the HKH region is highly exposed making it vulnerable to the impacts of multiple hazard events, impacts of climate change, and changes in land cover and land use can exacerbate these impacts (Adhikari et al. 2022a; Rusk et al. 2022).

2.2 Status of Land Cover, Land Use in the HKH Region The land cover and land use in the HKH region have undergone significant changes in recent years (Dai et al. 2021). The recent changes include forest cover loss, agricultural expansion, urbanization, and climate change. The HKH region is well known for its diverse biodiversity. However, deforestation and forest degradation are major challenges in the region. Studies have confirmed that the accelerated deforestation rate has been observed over different parts of HKH in the last few years (Lele and Joshi 2009; Pandit et al. 2007; Panta et al. 2008). Deforestation is mainly attributed to agriculture area expansion and urbanization. Agriculture is a key economic activity in the HKH region and farmers have traditionally relied on shifting cultivation and subsistence farming (Kafle 2011). However, with increasing population pressure and changing market demands, there has been a shift toward more intensive and commercialized forms of agriculture, which has led to land use changes and soil degradation. Ongoing rapid urbanization is also a major trend observed in the HKH region, with many cities experiencing significant population growth and expanding infrastructure (Singh et al. 2020). This has led to land use changes such as the conversion of agricultural land into urban areas, and has put pressure on natural resources such as water and forests. Further, deforestation has also increased the risk of landslides and floods, while changes in agricultural

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practice have also led to affect soil erosion and water quality (Veldkamp et al. 2020). Hence, the HKH region is undergoing significant changes and addressing these challenges that require a coordinated effort from government, civil society, and other stakeholders. Strategies that promote sustainable land use practices to protect forests, and support local livelihood can help to ensure that the region’s natural resources are used in a way that benefits both people and the environment.

2.2.1 LULC Changes Over Last 20 Years in the HKH Region Studies have shown that land use and land cover of the HKH region has changed over time (Kafle 2011; Panta et al. 2008; Paudel et al. 2016). The availability of satellite remote sensing data helps to assess the land use and land cover change over time. Moderate Resolution Imaging Spectroradiometer (MODIS) provides complete daily coverage of earth surface which is much beneficial to study large geographical areas (Friedl et al. 2002). MODIS itself has so many data products, for example, snow cover products, land cover products, and so on. In order to see the land cover change, we have used MODIS land cover data products for the years 2001 and 2021. Google Earth Engine (GEE) platform was used to access the data and the Q-GIS has been used to visualize the land cover data. The MODIS LC type 1, which has been used in this study, consists 17 land cover classes from which we reclassified those classes based on their broad properties, for example, we named Forests for LC type categories 1 to 5, i.e., Evergreen Needleleaf Forests, Evergreen Broadleaf Forests, Deciduous Needleleaf Forests, Deciduous Broadleaf Forests, and Mixed Forests (Sulla-Menashe and Friedl 2018). Comparison of two different MODIS land cover images shows that the permanent wetland has reduced by 69% followed by cropland (reduced by 14%). Similarly Barren land has also decreased by 10% and the least decrement observed in Savannas by 2%. On the other hand, Shrubland, Forest, Water bodies, Permanent snow cover, and urban built-up area have increased by 21%, 10%, 12%, 16%, and 4%, respectively (Table 2.2 and Fig. 2.1).

2.2.2 Drivers for LULC Changes Land is a crucial natural asset that has high economic, social, and biophysical practice. Therefore, LULC is under constant change mainly because of social development and natural process. In other words, this is one of the fundamental processes of earth surface that has its impact on human society and natural environment. On the other hand, the human activities that are happening on earth surface have altered the landscape. The human activities are shaped by the surroundings, hence the LULC change is different over different territory. Similarly, drivers of LULC change in the HKH region are complex and interconnected, and they vary across different

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Table 2.2  Land cover area change in HKH region of last 20 years (2001–2021) (Source: MODIS land cover data) Year LC type (MODIS) 1 to 5 6 and 7 8 and 9 10 11

2001 Area (km2) 526,313.5 94,689.75 444,589.3 1,613,540 17,578.25

2021 Area Percent (km2) 12.52 578,502 2.26 114,886 10.57 435,182.3 38.37 1,700,591 0.42 5346.5

Percent 13.75 2.73 10.35 40.44 0.13

Change area (km2) 52,188.5 20,196.25 −9407 87,050.5 −12,231.75

13

6037.75

0.14

0.15

237.25

12 and 14 15

137,145.8 3.26 41,634 0.99

117,406.3 2.79 48,366.75 1.15

−19,739.5 6732.75

16 17 Total

1,290,630 30.69 33,140 0.79 4,205,298 100

1,161,562 27.62 37,181 0.88 4,205,298 100

−129,068 4041 0

6275

Description Forest Shrubland Savannas Grasslands Permanent wetland Urban and built-up Cropland Permanent snow cover Barren land Water bodies

Fig. 2.1  Land cover map of HKH region (Data source: MODIS land cover product)

countries and regions within the HKH (Paudel et  al. 2016). The present LULC change has attributed to various human activities that include population growth, economic development, infrastructure development, climate change, and policy and institutional frameworks. Increasing population in the HKH region has put pressure on the available land resources. This has resulted in the expansion of agricultural and grazing land as well as the conversion of forests into croplands (Singh et al. 2020). The pursuit of economic growth has led to the expansion of urban and industrial areas in the region. This has resulted in the conversion of agricultural and forest lands to built-up areas. Similarly, infrastructure development such as road, highways, and hydropower projects has led to the fragmentation and degradation of natural habitats in the HKH region. This has also contributed to the conversion forests and agricultural lands to

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built-up areas. In addition to that, the climate change has had a significant impact on the HKH region, resulting in changes in temperature, precipitation, and the frequency and intensity of extreme weather events (Dhimal et al. 2021). Along with properties loss, the climate extreme events like flood and landslide also modify the existing land use and land cover pattern of the particular river basin (Khan et al. 2015). In addition to that, these changes have affected the availability of water resources and agricultural productivity, which further led to changes in land use practices. The policy and institutional frameworks in the HKH region have also played a crucial role on LULC change. For example, policies that promote the expansion of agriculture or the development of infrastructure can contribute to the conversion of natural habitats.

2.2.3 Influence of Population Growth in This Region Importance of human activities remained central discussion while studying landscape change. Many forests were cleared and agricultural land was transferred into built-up area, which has altered the local biodiversity. Therefore, ongoing population growth is the major threats to environment and drivers of LULC change. Although urban area covers relatively small fraction of the total earth surface, the urban area drives global environmental change (Grimm et al. 2008). Studies have confirmed that the rapid population growth has increased in the Himalaya region (Tiwari et al. 2018). Once the human population rises, many other connected activities increase automatically, that ultimately change the existing LULC, where HKH region is not an exception. The HKH region is home to a diverse range of cultures, and human activities such as agriculture, grazing, and infrastructure development have contributed to significant changes in LULC.  Some of the ways in which humans have influenced LULC changes in HKH region are: Agriculture, Deforestation, Grazing, urbanization, infrastructure development, and mining (Tiwari et al. 2018). Agriculture is a major land use practice in the HKH region. High population growth increases demand for food that led to an expansion of croplands in the region. Traditional agricultural practices have been replaced with modern techniques, including the use of agrochemicals and irrigation, which have resulted in environmental degradation and water pollution (Grimm et  al. 2008). Similarly, grazing is also a significant land use practice in the region especially in high-altitude areas. Increased human population leads to overgrazing (Kafle 2011). Overgrazing has led to soil erosion and degradation, which has impacted the productivity of the grasslands. Forests have been cleared at an alarming rate for agricultural expansion, timber extraction, and fuelwood collection. This has led to a loss of biodiversity, soil erosion, and reduced water availability. Rapid urbanization has led to the conversion of agricultural and forest land to built-up areas, resulting in a loss of biodiversity and natural habitats (Grimm et al. 2008). Besides that, construction of roads, highways, and hydropower projects led to the fragmentation and degradation of natural

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Fig. 2.2  Population density map of HKH region (Data source: https://sedac.ciesin.columbia.edu/ data/collection/gpw-­v4/sets/browse)

habitats. This has also contributed to the conversion of forests and agricultural lands to built-up areas. Having rich minerals in HKH region, mining activities have led to the loss of forests, degraded water quality, and soil erosion.Population density denotes the number of people living per square kilometer that shows population pressure on available resources. Gridded population density data derived from the Socioeconomic Data and Applications Center (SEDAC) with spatial of 1 km shows that the population density in the HKH region has increased significantly over the last 30 years. The number of grids that contain high population density (i.e., 1000 persons per square kilometer) has increased by 17% over the last 30  years. The number of pixels that have population density of 10,000 people per square kilometer has increased by 156%. The number of pixels with population density over 100,000 per square KM was 122 in 2000, which was increased to 960 pixels in 2020. Overall, the data shows that the population density has increased in recent years in the HKH region (Fig. 2.2 and Table 2.3).

2.3 Major Disasters and Their Impact in the HKH Region The HKH region had almost 20.85% (4075 of 19,547) major disaster events recorded in the past 32 years (between 1990 and 2022) in the Em-DAT global database, with death tolls of more than 28.71% in the region. The decade-wise distribution of disasters in the HKH region and across the world is shown in Table 2.4. Similarly, the total number of disaster events and fatalities accounted for geophysical, hydrological, meteorological, and climatological hazards in the countries of HKH region in the past 30 years (between 1991 and 2022) from the EM-DAT (Fig. 2.3). China accounted for more than 40.7% of the disaster events followed by India with 27.1% while Bangladesh, China, and India accounted for more than 20% of the overall fatalities in the HKH region in the past 32 years.

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Table 2.3  Population density of two different times of HKH region Code 1 2 3 4 5

Pixels 2000 3,549,643 1,690,245 484,729 12,295 122 5,737,034

Percent 61.872 29.462 8.449 0.214 0.002 100

Pixels 2020 3,289,288 1,844,762 570,480 31,545 960 5,737,034

Percent 57.334 32.155 9.944 0.550 0.017 100.000

Description Up to 10 persons per square KM 10 to 100 persons per square KM 100 to 1000 persons per square KM 1000 to 10,000 persons per square KM More than 10,000 persons per square KM

Table 2.4  Comparison of events and impacts of disaster in the HKH region and whole world in the past 32 years (1991–2022) No. of events

World HKH % of HKH Total no. World of deaths HKH % of HKH Total no. World of injured HKH % of HKH Total World affected HKH % of HKH Total World damages HKH (′000 % of US$) HKH

1991–2000 5408 1209 22.36%

2001–2010 7437 1628 21.89%

2011–2020 5549 1080 19.46%

2021–2022 1153 158 13.70%

1991–2022 19,547 4075 20.85%

1,189,875 279,599 23.50%

1,245,188 428,014 34.37%

247,458 67,665 27.34%

57,387 11,483 20.01%

2,739,908 786,761 28.71%

1,572,101 898,351 57.14%

4,087,134 1,163,305 28.46%

2,575,603 265,815 10.32%

321,470 23,620 7.35%

8,556,308 2,351,091 27.48%

2,117,935,177 2,383,775,728 1,615,283,870 298,113,692 6,415,108,467 1,751,198,842 1,971,023,935 966,892,049 84,781,196 4,773,896,022 82.68% 82.68% 59.86% 28.44% 74.42% 702,830,409 149,079,299 21.21%

1,012,289,787 1,764,709,418 482,285,585 3,962,115,199 258,698,553 337,721,847 69,039,000 814,538,699 25.56% 19.14% 14.31% 20.56%

Fig. 2.3  No. of disaster events and fatalities in the countries of the HKH region between 1991 and 2022 (Sources: EM-DAT 2022)

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The assessment of different hazards such as geophysical, hydrological, meteorological, and climatological hazards will support in the identification of the exposure and underlying risk to the elements-at-risk such as the population, infrastructures, and so on. In addition to this, the spatial scale of the assessment ranging from local to the national or across different administrative boundaries is also vital to assess the underlying risk in the region. The level and scale of assessment will help to identify the impacts to the elements-at-risk such as the exposed population, livelihoods of the communities, roads in kilometers, and so on. The assessment approaches can be either qualitative or quantitative, which will eventually contribute to determine the nature and extent of disaster risk. This can be done by analyzing potential hazards, evaluating the underlying conditions of exposure and vulnerability of the elementsat-risk. Hence, the assessment of disaster risks will contribute toward the identification and characterization (location, intensity, frequency, and probability) of hazards; the analysis of exposure and vulnerability, including the physical, social, health, environmental, and economic dimensions; and the evaluation of the effectiveness of prevailing and alternative coping capacities with respect to likely risk scenarios. Some of the major hazards in the HKH region are summarized below:

2.3.1 Earthquake The HKH region is well known for its complex topography and geomorphology. The existing collision between the continents, continuous mountain-building process, existing series of thrusts and faults are the major driving forces for the seismicity of the Himalaya. The dynamics of the collision between the southern Indian plate and northern Eurasian plate has been the major driving factor for the earthquake (Molnar and Tapponnier 1977; Tandon and Srivastava 1975). The convergence between the continuously northward-moving Indian plate and Eurasian plate is about 35–50 mm annually (Jade et al. 2017; Upreti et al. 2005). The HKH region is home to a number of developing countries and the rapidly urbanizing scenario in the HKH region is aggravating the exposure of population toward the earthquake. The existing vulnerable buildings and infrastructures are the major contributors for resulting in the losses of lives and properties (Bilham 1999). Interestingly, more than three-quarters of all the earthquake fatalities across the world have been found in the countries where the mean per capita income is less than 3200 per year (Bilham 2014). Based on the analysis of data from 1990 to 2015, He et al. (2021) ascertained a significant relationship between the urbanization ratio, population growth, and earthquake-related fatalities. The urbanizing terrains of HKH region have a significant population growth and interestingly more than 75% of the fatalities due to earthquake was found on the similar terrain signifying that the region is vulnerable, yet the exposure toward the earthquake is increasing significantly. The HKH region has been suffering massive losses due to the earthquake which includes a destructive 8.0 magnitude Shaanxi Earthquake of China on January 23, 1556 resulting in about 830,000 death tolls (Feng et al. 2020). Similarly, the 8.1

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Magnitude Nepal-Bihar Earthquake of January 15, 1934 resulted in the loss of more than 15,700 death tolls (Sapkota et al. 2016). The recent Gorkha Earthquake of 2015 suffered a collapse of 498,852 buildings and partial damage of more than 256,697 buildings (Gautam 2017). Some of the major earthquakes observed in these regions alongside the fatalities number are summarized from EM-DAT (Fig.  2.4 and Table 2.5). Almost 27% of the earthquake events recorded across the world are found in the HKH region as suggested by the data from the past three decades. Similarly, the majority of the deaths and injuries that occurred due to the earthquakes in the last three decades across the world are found significant and increasing trend in the HKH region (Table 2.6).

2.3.2 Flood The events of flooding have been a recurrent event with higher mortality rate as compared to other water-induced disasters in this region. Almost 76 number of flood events are found to be occurring annually in the HKH region which has been claiming thousands of lives and affecting millions of people (Shrestha et al. 2015). It is difficult to forecast flash floods as compared to riverine (floodplain) floods due to their rapid onset nature due to the intense rainfall. Such flash floods are

Fig. 2.4  Country wise Spatial Distribution of earthquake fatalities and total affected population

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Table 2.5  List of major earthquakes in the HKH region Date April 4, 1905 August 15, 1950 30 Sep 1993 30 May 1998 January 26, 2001 October 8, 2005 May 12, 2008 September 24, 2013 April 25, 2015

Earthquake 7.8 magnitude, Kangra Earthquake, Himachal Pradesh, India 8.6 magnitude Assam-Tibet Earthquake 6.4 Magnitude, Latur Earthquake 6.9 Magnitude, Afghanistan Earthquake 7.7 magnitude Gujarat Earthquake 7.6 Magnitude Kashmir Earthquake, Muzaffarabad 7.9 Magnitude Wenchuan Earthquake 7.7 Magnitude Balochistan Earthquake, southwestern Pakistan 7.8 Magnitude Gorkha Earthquake

Approx. death toll 20,000 1500 9748 4700 20,005 73,338 87,476 462 8831

Data Source: D. Guha-Sapir, R. Below, Ph. Hoyois—EM-DAT: The CRED/OFDA International Disaster Database—www.emdat.be—Université Catholique de Louvain—Brussels—Belgium Table 2.6  Impact of earthquake events in the HKH countries in the last 32 years (1991–2022) No. of events

Total no. of deaths

Total no. of injured

Total affected

Total damages (′000 US$)

World HKH % of HKH World HKH % of HKH World HKH % of HKH World HKH % of HKH World HKH % of HKH

1991–2000 250 60 24.00%

2001–2010 259 70 27.03%

2011–2020 248 74 29.84%

2021–2022 59 17 28.81%

1991–2022 816 221 27.08%

58,422 19,759 33.82%

451,439 187,070 41.44%

16,924 11,566 68.34%

4368 1267 29.01%

531,153 219,662 41.36%

233,859 74,300 31.77%

1,214,126 701,037 57.74%

201,507 143,501 71.21%

27,968 3925 14.03%

1,677,460 922,763 55.01%

2,448,6576 15,193,769 62.05%

81,454,787 65,693,095 80.65%

27,597,825 15,408,901 55.83%

4,945,619 757,341 15.31%

138,484,807 97,053,106 70.08%

186,303,765 179,812,448 159,997,871 23,801,291 549,915,375 1,597,343 96,213,174 23,254,820 3,899,000 124,964,337 0.86% 53.51% 14.53% 16.38% 22.72%

Source: D.  Guha-Sapir, R.  Below, Ph. Hoyois—EM-DAT: The CRED/OFDA International Disaster Database—www.emdat.be—Université Catholique de Louvain—Brussels—Belgium

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generally catastrophic resulting in disastrous impacts on lives and properties. The cloudburst event (540 mm in 24 h) of July 1993 in central Nepal with more than 62 fatalities and loss of 52 houses, 2010 flooding incident in Pakistan with more than 2000 fatalities, 2013 Uttarakhand flooding with more than 5000 fatalities are some of the major severe floods in the HKH region (Champati Ray et al. 2016; Dhital 2003; FFC 2010; Upreti and Dhital 1996). Some of the major impacts of the flood events in the HKH (Fig. 2.5 and Table 2.7). The data from the past three decades signify that 17% of the flooding events recorded across the world are inherent in the HKH region. Further, the majority of the deaths resulted by the floods in the last three decades across the world are found significant in the HKH region with almost 50% of the fatalities in the HKH region (Table 2.8).

2.3.3 Landslide The topography plays a significant role in the spatial variation of attributes such as soil moisture, groundwater flow, and slope stability. More than 40% of the terrain in the HKH region is characterized by the steep (i.e., terrain slope of 15° or more) topography

Fig. 2.5  Country wise Spatial Distribution of flood fatalities and total affected population

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Table 2.7  Impact of flood events in the HKH Countries in the last 32 years (1991–2022) Country Afghanistan Bangladesh Bhutan China India Myanmar Nepal Pakistan Grand Total

No. of events 5468 6189 232 30,352 46,282 775 5741 13,756 108,795

Total deaths 1853 21,890 745,226 7706 110 1847 25,158 803,790

Total injured 872,035 157,477,238 1600 1,902,888,207 629,257,192 3,959,467 5,048,898 98,791,599 2,798,296,236

Total affected 87,000 9,893,800

Total damages (′000 US$)

303,211,200 86,400,309 257,655 1,213,929 36,421,378 437,485,271

Source: D.  Guha-Sapir, R.  Below, Ph. Hoyois—EM-DAT: The CRED/OFDA International Disaster Database—www.emdat.be—Université Catholique de Louvain—Brussels—Belgium Table 2.8  Impact of flood events in the HKH countries in the last 32 years (1991–2022) Descriptions No. of events

Region World HKH % of HKH Total no. of World deaths HKH % of HKH Total no. of World injured HKH % of HKH Total affected World HKH % of HKH Total World damages HKH (′000 US$) % of HKH

1991–2000 958 168 17.54%

2001–2010 1747 314 17.97%

2011–2020 1549 285 18.40%

2021–2022 399 42 10.53%

1991– 2022 4653 809 17.39%

99,167 44,827 45.20%

56,217 28,754 51.15%

48,490 27,863 57.46%

12,228 7351 60.12%

216,102 108,795 50.34%

817,130 536,755 65.69%

236,995 216,592 91.39%

66,036 35,687 54.04%

22,341 14,756 66.05%

1,142,502 803,790 70.35%

1,463,855,808 1,066,385,233 539,859,728 87,189,965 1,370,469,681 957,455,670 408,622,200 61,748,685 93.62% 89.79% 75.69% 70.82% 232,907,657 109,019,177 46.81%

189,454,085 86,680,879 45.75%

3.16E + 09 2.8E + 09 88.63%

394,125,611 120,885,240 9.37E + 08 195,451,715 46,333,500 4.37E + 08 49.59% 38.33% 46.67%

Source: D.  Guha-Sapir, R.  Below, Ph. Hoyois—EM-DAT: The CRED/OFDA International Disaster Database—www.emdat.be—Université Catholique de Louvain—Brussels—Belgium

(Vaidya et al. 2019). The factors resulting in the generation of the landslides can be categorized into causative and triggering factors (Guzzetti et al. 2012). Causative factors mostly include the conditioning factors such as slope, aspect, land-use-land-cover, geology, drainage density, and so on. The triggering factors include either sliding or the

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factors like earthquake, cloudburst/excess precipitation, and anthropogenic activities. The HKH region is also dominated by the monsoon. The precipitation from the southwest monsoon, originating from the Bay of Bengal, results in the longer summer rainy season in the Eastern Himalayas as compared to the Central and Western Himalayas. The anthropogenic activities such as formal/informal construction of roads, inappropriate agricultural practices, poor drainage, and improper debris management have been the primary reasons for the generation of landslides and LULC changes (Adhikari et al. 2022b; Gautam et al. 2019; McAdoo et al. 2018). The Chittagong Hilly Areas of Bangladesh received an excess rainfall of 510 mm in just 48 h (12–14 June 2017) thereby triggering the landslides and resulting in the death toll of 170 and affecting 15,000 families (Bajracharya and Maharjan 2018). Further, the Jure Landslide 2014 with 156 death tolls, Darjeeling Landslide 2015 with 38 death tolls, Catastrophic mass movement of 1998 monsoon at Malpa-­ Kumaun in 1998 with 221 fatalities, and Debris flow at Ukimath-Uttarakhand in 2012 with more than 50 death tolls are some of the rainfall-induced landslides in the HKH region (Acharya et al. 2016; Biswas and Pal 2016; Islam et al. 2014; Paul et al. 2000). The Gorkha Earthquake 2015 resulted in the generation of more than 20,000 earthquake-triggered landslides among which the Langtang Avalanche was the most destructive with 350 death tolls (Kargel et al. 2016). Similarly, the tragic Attabad Landslide of 2010 resulted in more than 20 death tolls and loss of properties (Hayat et al. 2010). Though landslide susceptibility maps have been developed in the different regions of the HKH to assess the susceptible zones and plan for the intervention measures (Khatun et al. 2022; Mahmood et al. 2015; Meena et al. 2022; Saha et al. 2005; Sarkar et al. 1995), the interaction between the landslides and anthropogenic activities has resulted in the re-activation or generation of new landslides. Further, the active seismo-tectonic activities coupled with complex topography and climatology have been resulting in a number of landslide events (Stäubli et al. 2018). Glacial Lake Outburst Floods (GLOF) HKH region consists of a significant number of glacial lakes. The accumulation of huge amount of water through the blockage of moraines and melting of ice and snow has been creating a number of glacial lakes and is a source of the major rivers in the HKH region. These glaciers are found near the down valleys close to the glaciers. These lakes when have a sudden breach result in the generation of huge amount of water and debris ultimately resulting in flooding. It is dependent on a number of time-dependent variables such as melting process, glacier movements, water level alteration/fluctuations, seepages, etc. alongside the hydrological and climatological conditions. GLOFs are known to be the dangerous phenomena often triggered by increased temperature that weaken the loose moraine dams (Sabin et al. 2020). Impact of GLOF is considerably high in the downstream areas where the population is also high. GLOFs are not just imposing the risk to the downstream population but also modifying the geomorphology of the river basin.

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Maharjan et al. (2018) mapped about 25,614 glacial lakes covering in the five major river basins—Amu Darya, Indus, Ganges, Brahmaputra, and Irrawaddy, including Mansarovar Interior Basin—in the HKH. The rate of glacier retreat has been increasing due to the rise in global temperature thereby leading to the run-off and GLOF events (Bolch et al. 2012). Some of the major GLOF events in the region are the 1981 GLOF originating from TAR, China, 2000 GLOF originating from the Hushe River of Pakistan, 2008 GLOF events in Hunza basin of Karakoram (Ashraf et al. 2012; Ives et al. 2010; Mool et al. 2001). The GLOF event of Uttarakhand in 2013 affected more than 100,000 people in the region and resulted in the catastrophic losses of infrastructures like hydropower dams (Champati Ray et al. 2016; Schwanghart et al. 2016). Forest Fire Forest almost covers 25% of the area in the region and is hence an integral part of the ecosystem (Kotru et al. 2015). Forest fire has been one of the major factors for forest degradation and has been resulting in the overall productivity of forest ecosystem, biodiversity, and other ecosystem services. The events of forest fire have been evolving as a serious concern in the HKH region mainly because of the changing climatic conditions and underlying factors (Kumar and Kumar 2022; Sharma et al. 2012). The events of forest fire are triggered by both natural and anthropogenic reasons. Further, the urbanization pressure at the wildland and urban interface has also been increasing the frequency and destructiveness nature of the forest fire (Vilà-Vilardell et al. 2020). It is thus essential to understand the susceptibility of wildfires in the different landscapes for the reduction of adverse consequences of wildfires (Hong et al. 2019). Hazard Interaction In a given geographical region, there can be multiple hazards acting in silos or even together. The existing topography, complex geology, climatic conditions, and anthropogenic interaction have made the HKH region prone to multiple hazards and often the interaction of hazards results in the prevalence of cascading and compounding multi-hazards. There has been a significant increase in exposure toward multiple hazards with the increase in anthropogenic activities. Assessing such hazards singly may not reflect the true ground realities as the region is complex and there are evidences of interaction among the hazards in the region (Byers et  al. 2019; Gautam et al. 2022; Mahmood et al. 2015; Shugar et al. 2021). The mountain regions are subjected toward the cascading consequences of flooding, debris flow, landslides, and other events due to the triggering factors such as precipitation, earthquakes, and so on (Arias et al. 2021). Further, this region also requires the need of transboundary approaches for solving the existing hazard complexity. Some of the notable hazard events are mentioned in Table 2.9.

Kashmir EQ 2005 Earthquake

Wenchuan EQ 2008 Earthquake

>73,338 >128,309 Collapsed buildings, infrastructure, communication

Mahmood et al. (2015); Sato et al. (2007)

Deaths Injuries Impacts

Source

>87,476 >366,596 Agriculture, livestock, highways, public infrastructure, hydropower, industries, telecommunication Yin et al. (2009)

Cascading hazards Secondary More than 2424 More than 15,000 events of hazards landslides triggered geohazards (rockfalls, With an area debris flow, landslides, etc.) greater than 7500 sq. km.

Name of event Trigger

Table 2.9  Some transboundary hazards and their impacts Uttarakhand flood 2013 Landslide lake outburst flood, cloudburst

>200 >12 Hydropower

Flooding

Chamoli flood 2021 Rock and ice avalanche

Gautam and Houze et al. Shugar et al. Chaulagain (2016); (2017); Ziegler (2021) Gnyawali and et al. (2014) Adhikari (2017); McAdoo et al. (2018)

Avalanches on Mt. Flash floods Everest, Langtang, etc. More than 19,332 earthquake triggered landslides >8790 >6054 >22,300 >4473 Buildings, heritages

Gorkha EQ 2015 Earthquake

Panthi (2021)

>156 >47 Hydropower, road, households

Damming Sunkoshi River

Bikash Maharjan et al. (2021); Gautam et al. (2022); Pandey et al. (2021)

>5 >6 Hydropower, bridges, road, agriculture, households

Debris flow deposition

Jure landslide Melamchi flood 2014 2021 Landslide dam Landslide damming outburst flood

22 B. R. Adhikari et al.

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2.4 Conclusion The Hindu-Kush Himalayan region is a seismo-tectonically active area with a strong influence of the Asian monsoon. This coupling effect has resulted in lots of damages and loss of lives and properties. Therefore, this region experiences many trans-­ boundary hazards affecting the population, agricultural land, and critical infrastructures. The existing topography, increasing urbanization, excavation of roads in the mountainous area, and inappropriate agricultural practices create high stresses on the human population. The change in LULC over the years due to population increase and rural-urban migration increases the vulnerability in this region. This vulnerability further exacerbates with the multiple hazard interactions. The increasing climate change scenarios will further increase the hazards and vulnerability of this region.

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Chapter 3

Spatio-Temporal Dynamics of Land Use Land Cover and Its Impact on Flood-­Prone Drainage Basin of River Swat, Eastern Hindukush Haseeb-Ur Rahman, Abdullah Khan, Atta-Ur Rahman, and Rajib Shaw Abstract  This chapter deals with the spatio-temporal dynamics of land use land cover (LULC) and its impact on the flood-prone drainage basin of River Swat, Eastern Hindukush. In the study area (Swat River Basin), the population is increasing at a rapid pace and there is a consistent change in LULC. Swat River Basin is famous for eco-tourism and falls in the high flood hazard zone, wherein the upstream area has flash flood characteristics and the low-lying plain areas are exposed to riverine floods. In order to achieve the study objectives, data were obtained from both primary and secondary sources and were analyzed using geospatial techniques. It was found from the LULC analysis that river Swat is gradually changing its course. In the study area, the population is increasing at a rapid pace and as a consequence, there is a gradual human intervention in the flood-prone areas and encroachments over the farmland. The analysis revealed that after the disastrous flood events of 2010 and 2022, an exponential change has occurred in the flood-prone areas of Swat River Basin. In order to check such human-induced environmental challenges, planners and decision-makers should formulate land use regulations to check unprecedented interference over ecologically important land. Keywords  Land use land cover · Flood · Swat drainage basin · Hindukush

H.-U. Rahman Institute of Space Technology, Islamabad, Pakistan A. Khan · A.-U. Rahman (*) Department of Geography and Geomatics, University of Peshawar, Peshawar, Pakistan e-mail: [email protected] R. Shaw Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Mazumder, R. Shaw (eds.), Surface Environments and Human Interactions, https://doi.org/10.1007/978-981-97-0112-4_3

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3.1 Introduction Historically, humans have been modifying the earth’s surface, but the use of mechanization and population pressure has significantly changed the land use land cover (LULC) during the past three decades. However, only a few landscapes on the earth are in their natural state (Roy and Roy 2010). Land use and land cover are often used interchangeably (Rahman and Khan 2012; Ellis 2007), but they have distinct differences. Land cover encompasses the physical and biological characteristics that cover the land surface, such as water bodies, vegetation, bare areas, and man-made structures. It includes the natural and human-made features found on the Earth’s surface (Rahman et  al. 2012). On the other hand, land use applies to the human actions and practices carried out in a particular area, which transform the natural environment into a developed environment, such as agricultural, commercial, residential, recreational, and industrial activities (Lambin et al. 2001). Land cover can be assessed both qualitatively and quantitatively through remote sensing techniques. On the other hand, studying land use and its changes necessitates combining natural and scientific methods to discern the particular human activities occurring in various landscape regions, even when the land cover appears similar (Abbas et al. 2010). The alteration of LULC has a significant impact on biodiversity reduction, which, in turn, affects the climate in a region both locally and regionally (Yohannes et al. 2020). The determination of LULC is largely based on examining the ecological conditions, geological structures slope, and altitude in combination with technological, institutional, and socio-economic factors that significantly influence the land use patterns in an area. Changes in the landscape can bring about significant environmental transformations at large scales (Mishra et al. 2020). Humans have been rapidly disrupting the natural environment to meet their resource needs (Berihun et al. 2019; Rawat and Kumar 2015). Rapid changes in the LULC pattern, particularly in developing nations are resulting in the depletion of essential resources, such as soil, vegetation, and water bodies (Cheruto et al. 2016; Twisa and Buchroithner 2019). Additionally, these human-induced disruptions are significantly altering the climate, exposing slopes to precipitation, increasing water runoff, and triggering disasters (Haindongo et al. 2020). The erosive power of water also rises, as runoff increases downslope; as a result, the bare slopes act as catalysts for triggering disasters such as floods and landslides (Bibi et al. 2019). LULC affects the consequences and probability of a flood in several ways. Changes in land use and land cover, such as the expansion of impervious surfaces, can transform the landscape’s features and have a significant impact on the dynamics of water flow within a watershed. These modifications to water flow can affect vital hydrological processes, including infiltration, runoff, evapotranspiration, and erosion rates (Sugianto et  al. 2022; Gautam et  al. 2003; Mustafa et  al. 2012). Significant shifts in the hydrological balance in a watershed can have adverse impacts on ecological diversity, leading to declines in aquatic populations, as well as negative effects on human health and general welfare resulting from droughts and food shortages (Bhaduri et al. 2000). Human activities such as increased population,

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changes in LULC, and the expansion of residential areas contribute to flooding by affecting the hydrological cycle and water availability (Gan et al. 2018). There are various techniques available to collect information on LULC conditions, such as field surveys, aerial photography, and satellite remote sensing. While each method has its own benefits and drawbacks, field surveys can offer highly accurate data but are time-consuming and not practical for large areas. On the other hand, aerial photography can offer precise mapping but is subject to the availability of photographs at a suitable scale. Satellite remote sensing can effectively cover vast areas and offers different spatial resolutions to choose from (Zhu and Woodcock 2014; Mustafa et al. 2012). It offers cost-effective, all encompassing, and streamlined spatial assessments that are valuable for decision-making in hydrology and water resource development (Patel et al. 2013; Galford et al. 2008).

3.2 Floods in Pakistan Floods are the most common natural disasters worldwide (Ochani et al. 2022). In 2021, the Center for Research on the Epidemiology of Disasters (CRED) recorded 432 catastrophic events, with floods accounting for 223 occurrences. Global flood disasters have resulted in a substantial rise in illness and fatalities, rendering human life more susceptible to various hazards and disasters. Epidemics and outbreaks are common during floods, affecting a significant portion of the population. Flood-­ affected individuals encounter numerous challenges, including infectious diseases, reproductive health complications, and even mental health disorders (CRED 2022). According to the Climate Risk Index, Pakistan holds the seventh position in the list of the most vulnerable countries to climate change globally. Additionally, the Global Risk Index has ranked Pakistan 18th out of 191 countries in terms of its susceptibility to climate change impacts (Eckstein et al. 2019). Pakistan witnessed a total of 21 notable floods from 1950 to 2011, averaging one flood every 3 years. However, the most devastating flood in Pakistan’s recorded history transpired in 2010, concurrently impacting almost all four provinces of the country. The economic toll of the 2010 flood was staggering, with a total loss estimated at USD 9.7 billion. Tragically, the flood also resulted in the loss of 1985 lives and affected approximately 20 million people throughout the country (Shah et al. 2022; Rahman and Shaw 2015). The occurrence of disasters such as the 2010 flood has significantly influenced the perception and attitude of the community toward risk. As the flood swept through the country from north to south, it severely affected several sectors critical to the development of the nation (Khan and Ali 2014). In 2022, heavy rains and flooding caused a catastrophic disaster in Pakistan from June to August. This event was unprecedented and resulted in 33 million people being affected, including almost 8 million displaced individuals. Sadly, over 1700 people lost their lives, with one-third being children. The floods caused by the rainfall, as well as accelerated glacial melt and landslides, destroyed millions of homes and crucial infrastructure. Entire villages were submerged, and many people lost

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their livelihoods. Preliminary estimates suggest that the floods will push between 8.4 and 9.1 million people into poverty, resulting in a 3.7–4 percentage point increase in the national poverty rate. As of October 11, 2022, more than half of the country’s districts, were declared “calamity hit,” with the majority being in the provinces of Baluchistan, Sindh, and Khyber Pakhtunkhwa. Additionally, 19 out of the 25 poorest districts in the country were affected by the disaster (NDMA 2022).

3.3 The Study Area The Swat Valley is situated in northern Pakistan, Eastern Hindu Kush region, between 34° 2′ to 35° 53′ North latitude and 71° 0′ to 72° 47′ East longitude (Fig. 3.1). The study area is characterized by rugged terrain with high peaks ranging from 230 m in the south to about 5801 m above sea level (Rahman and Khan 2013). The Hindu Kush region comprises a number of productive valleys that are irrigated by rivers and streams, among which is the Swat Valley, famous for its picturesque scenery and aesthetic significance. Bordered by mountains on its eastern and western sides, this extended valley is traversed by the meandering Swat River in a north-­ south direction (Rahman et al. 2017). The Gabral and Ushu Rivers in the Kalam region are the primary source of the Swat River, one of the major tributaries of the

Fig. 3.1  Location and digital elevation of the study area, Swat River Basin

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Kabul River. The river initially flows southward through a relatively narrow gorge until it reaches Madyan, situated at an altitude of 4300 feet. Beyond Madyan, the Swat Valley widens, and as it approaches Kalagay, the river changes its course to the west, where the Panjkora River, which commands a vast area, joins it. Eventually, the Swat River departs from the northern uplands and flows into the plain area of the Peshawar basin (Dawood et al. 2021). The Swat Valley experiences a highland climate characterized by cold winters and cool summers. Usually, snowfall occurs during winter that accumulates in the high mountains and eventually serves as a source for river recharge during the summer season. Similarly, summer rains typically begin in July and persist until September. These rains are typically plentiful, leading to increased river runoff and faster snowmelt in catchment areas. The Swat River exhibits a complex drainage pattern, characterized by numerous streams converging from both the left and right banks. The main river flows in a southerly direction, and near Mingora, it takes a syntoxic right bend. According to peak discharge data, the high-flow season in the Swat River typically begins in May and continues through the end of August. The high discharge of the Swat River during the summer season is primarily attributed to the heavy melting of snow/ice and glaciers in the headwater region. Additionally, the summer monsoonal rainfall also contributes to the increased river discharge, leading to recurrent floods (Rahman et al. 2017).

3.4 Flood in Swat Drainage Basin Khyber Pakhtunkhwa has been the epicenter of natural disasters such as floods, leading to adverse impacts on its infrastructure, land, education, health, modern development, and human lives to an extreme extent. Despite the province’s efforts toward recovery, it still lags behind other provinces, with minimal construction research being conducted compared to others. Nestled in the Karakoram, Himalayas, and Hindu Kush Mountain ranges, Khyber Pakhtunkhwa is home to glaciers and other high-peak ice reserves. These high and steep mountains also contribute to the major rivers of Pakistan, with the Indus River in the Khyber Pakhtunkhwa plains being joined by Swat, Kabul, and Panjkora. The area and its inhabitants frequently experience year-round flooding due to these factors, which have led people to adapt their lives to seasonal and unpredictable rainfall. As a result, poverty levels have risen significantly at both the provincial and national levels (Khayyam and Noureen 2020). Swat Valley is a region where flooding occurs frequently. In the upper reaches of the valley, flash floods are common, whereas downstream in Madyan, river flooding is more prevalent. Swat River, which flows through the valley, widens into a basin and splits into several channels, frequently changing course. Each summer, the river’s peak discharge causes it to overflow its natural levees, resulting in damage to various sectors including agriculture, housing, and others. In some areas, deep riverbank erosion is a prevalent issue, posing a threat to farmland and built-up areas.

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Despite the region’s history of floods, the growing population has utilized the active floodplain for development and cultivation without adequate consideration for the risk of floods. Consequently, the vulnerability to floods has escalated, with little emphasis on land use regulation and zoning. Land use regulations are often employed as a non-structural approach to mitigate floods by minimizing exposure to people and property. Analysis indicates that the encroachment of human activities onto flood channels and the lack of land use regulations are key factors contributing to significant flood-related losses. In order to conduct a comprehensive flood risk assessment and develop effective spatial land use plans, it is imperative to consider fluvial morphology and rainfall-runoff models, while understanding the challenges associated with land use planning (Rahman et al. 2017).

3.5 Spatio-Temporal Dynamics of Land Use Land Cover in Swat Drainage Basin Changes in land use and land cover are recognized as the primary drivers of flooding, as they can significantly impact hydrological processes (Zhao et al. 2013). The current study investigates the land use and land cover changes over a 12-year period (2010–2022). Parallel to this, a detailed spatial analysis of pre- and post-flood 2010, and pre- and post-flood 2022 was also carried out. The Landsat and Sentinel 2-A satellite images used in this study were obtained from the website of the United States Geological Survey (USGS). A total of four satellite images were acquired, capturing the pre- and post-flood conditions for both the years 2010 and 2022. After acquiring the images, it was processed in ArcMap 10.8. The downloaded images were then classified using maximum likelihood supervised classification. The images were classified in such a way that 600 training samples (120 from each class) were taken, and based on these training samples the images were classified into five LULC classes, i.e., water, vegetation, build-up area, snow cover, and barren land (Figs. 3.2 and 3.3). The results of the analysis reveal that in the 2010 pre-flood, the area under barren land was 2254  km2 (14.94% of the total land), built-up occupied 2088.63  km2 (13.84%) area, snow covered an area of 1445.26 km2 (9.58%), vegetation covered area was 8726.31 km2 (57.84%), and 573.62 km2 (3.80%) was occupied by water bodies. Whereas the 2010 post-flood classified image result shows that the area under barren land and water bodies has increased from 2088.63 to 2834.02  km2 (18.78%), and from 573.62 to 1428.62 km2 (9.47%) respectively. On the other hand, the built-up, snow-covered area, and vegetation have decreased from 2088.63 to 2032.63 km2 (13.47%), from 1445 to 1011.26 km2 (6.70%), and from 8726.31 to 7781.31 km2 (51.57%) respectively (Table 3.1). The results of the analysis reveal that in the 2022 pre-flood, the under-barren land was 1874.02  km2 (12.42% of the total land), built-up occupied 3718.63  km2 (24.65%), snow-covered 1635.26 km2 (10.84%), vegetation occupied 7446.31 km2

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Fig. 3.2  Classified images of pre- and post-flood 2010, Swat River Basin (Source: classification of Landsat ETM+ 2010)

Fig. 3.3  Classified images of pre- and post-flood 2022, Swat River Basin (Source: classification of Sentinel 2-A)

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Table 3.1  LULC 2010, change detection (Area) (Source: classification of Landsat ETM+ 2010) Area in km2 LULC pre-flood Land cover 2010 Barren land 2254.02 Built-up 2088.63 area Snow cover 1445.26 Vegetation 8726.31 Water 573.62 Total 15,088

LULC post-flood 2010 2834.02 2032.63 1011.26 7781.31 1428.62

Area %age LULC pre-flood 2010 14.94 13.84 9.58 57.84 3.80 100

LULC post-flood 2010 18.78 13.47

% Change 3.84 −0.37

6.70 51.57 9.47

−2.88 −6.27 5.67

Table 3.2  LULC 2022 change detection (area) (Source: classification of Sentinel 2-A) Area in km2 LULC pre-flood Land cover 2022 Barren land 1874.02 Built-up 3718.63 area Snow cover 1635.26 Vegetation 7446.31 Water 413.62 Total 15,088

LULC post-flood 2022 1924.02 3647.63 1014.26 6927.31 1574.62

Area %age LULC pre-flood 2022 12.42 24.65 10.84 49.35 2.74 100

LULC post-flood 2022 12.75 24.18

% Change 0.33 −0.67

6.72 45.91 10.44

−4.12 −3.44 7.7

(49.35%), and water covered 413.62  km2 (2.74%). Whereas the 2010 post-flood classified image result shows that the area under barren land and water bodies has increased from 1874.02 to 1924.02 km2 (12.75%), and from 413.62 to 1574.62 km2 (10.44%) respectively. However, the built-up land, snow-covered area, and vegetation have declined from 3718.63 to 3647.63  km2 (24.64%), from 1635.25 to 1014.26  km2 (10.84%), and from 7446.31 to 6927.31  km2 (45.91%) respectively (Table 3.2).

3.6 Impact of LULC on Flood-Prone Drainage Basin of River Swat The amount of runoff produced during a precipitation event is determined by the LULC pattern, which affects the balance of water in a region. Thus, LULC may influence both the likelihood of flooding and its effects (Bryndal et al. 2017; Kabeja et  al. 2020). Although extreme hydro-meteorological conditions are a significant factor in flood losses, unplanned land use practices can significantly intensify property damages during floods (Lee and Brody 2018). LULC changes can have a significant impact on the flood-prone drainage basin of River Swat. The River Swat

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basin is located in the northern part of Pakistan and is known for its scenic beauty and unique ecological features. However, over the years, human activities such as deforestation, urbanization, agriculture, and infrastructure development have resulted in significant LULC changes (Awotwi et al. 2018). As a result, the river may overflow its banks during periods of heavy rainfall, leading to more frequent and severe floods (McColl and Aggett 2007). On the positive side, certain LULC changes can help mitigate flooding in the River Swat basin. Afforestation and reforestation efforts can increase vegetation cover, reduce soil erosion, and improve infiltration, which can help regulate river flows and reduce flood risk. Additionally, sustainable agricultural practices, such as terracing and contour farming, can reduce soil erosion and surface runoff, thereby mitigating flood risk (Szwagrzyk et al. 2018).

3.7 Impact of LULC on Flood Occurrence in Swat Drainage Basin The growth in human population and living standards has led to a higher demand for agricultural production and utilization of land resources. However, increasing the per unit production rate is challenging in many societies, resulting in an expansion of arable land at the cost of natural land cover. Natural resources and land cover are integral components of balanced ecosystems. Disturbing this balance can result in an increase in surface run-off, reducing the soil’s ability to retain moisture can lead to an increase in surface run-off, destruction of natural habitats, and an increase in the occurrence of flash and riverine floods, as well as changes in rainfall frequency and intensity (Panahi et al. 2010; Lambin and Meyfroidt 2011). Scientific literature also attributes the adverse consequences of land transformation to global climate change and its subsequent modifications (Mahmoudi et al. 2020). The increasing concentration of greenhouse gases in the atmosphere has caused a rise in global land temperatures, leading to a rise in sea levels, increased snow and glacier melting, and a rising trend of hydro-meteorological disasters (Aduah and Baffoe 2013).

3.8 Conclusion The Swat River Basin is at a high risk of flooding owing to its mountainous topography. Each year, heavy monsoon rains, as well as the melting of snow, ice, and glaciers cause the Swat River to flood. Additionally, changes in land use and land cover (LULC), coupled with construction and encroachments in rivers and torrents in downstream areas carrying more discharge than usual, can have a variety of effects on the probability and severity of floods. LULC changes from human activities such as agricultural expansion, deforestation, and urbanization, represent the

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influence of humans on natural landscapes and have resulted in continued pressure on various ecosystems due to population growth worldwide. The illegal construction in the study region has aggravated the situation by increasing the vulnerability of the communities, ultimately exposing them to an extreme level of risk. This has led to a significant increase in flood damages as the encroachments have added to the velocity and ferocity of the floods, causing unprecedented erosion and rapid runoff into streams. The rapidly flowing water has picked up more and more sediments, resulting in raised river channel levels. Therefore, downstream villages, cities, agricultural fields, and other infrastructure are frequently subjected to flooding, particularly during the rainy season. Unfortunately, in Swat Valley, there is a lack of land use planning and building codes to effectively regulate the utilization of active floodplains. Additionally, there is an absence of integrated land use planning that takes into account all natural resources. Proper recording of community and public lands is also inadequate, with limited information available regarding the extent of such lands.

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Chapter 4

Proactive Adaptation to Climate Change in the Mekong Delta in Vietnam: A Socio-­ecological Approach Huy Ngoc Ha, Rajib Shaw, Thi My Thi Tong, and Thi Tuyet Tran

Abstract  The MeKong Delta has experienced a lot of impacts of climate change; however, ongoing solutions have mainly focused on the approach of minimization with priority of irrigation works but their results have been limited, and work of response is still passive. Therefore, in order to proactively adapt to climate change is necessary to have a more reasonable approach; in particular, the approach of socio-ecology is concentrated on analyzing mutual relationship among systems in specific territory integrating the factors of modern time which will provide scientific and harmonic information to choose development model in accordance with the viewpoint “respecting and taking advantage of nature”, especially proposing policy framework with feasible approach to propose a long-term development vision. The main factors that greatly affect the natural differentiation of the Mekong Delta territory include water source, the simultaneous impacts of the sea-ocean process combined with the dependence on the water source upstream of the Mekong River, the yearly rainfall in the Mekong Delta, the exploitation and utilization of the territory from upstream to coastal areas leading to the peculiarity of the territorial divergence and differentiation. It is the differentiation of social-ecological characteristics that creates this diverse territory formed of four sub-regions (the mainland). Each sub-­ region has its own functions, hence different management and utilization solutions are needed towards the goal of sustainable development of the study area. Keywords  The Mekong Delta · Vietnam · Climate change · Adapting to climate change · Approach of ecological-social region · Territorial zoning

H. N. Ha · T. M. T. Tong Vietnam Institute of Economics, Vietnam Academy of Social Sciences, Hanoi, Vietnam R. Shaw Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan e-mail: [email protected] T. T. Tran (*) Institute of Human Geography, Vietnam Academy of Social Sciences, Hanoi, Vietnam © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Mazumder, R. Shaw (eds.), Surface Environments and Human Interactions, https://doi.org/10.1007/978-981-97-0112-4_4

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4.1 Introduction Climate change is one of the most enormous challenges with mankind in the twenty-­ first century; impacting significantly on the socio-economy and environmental security of the world as well as the sustainable-developing processes of nations (IPCC 2007, 2012; WB 2018; Amanda et al. 2016; Holly et al. 2012). International community has been more and more aware of expressions and potential influences of climate change through many research works in various scales; at the same time, proposed responding measures in diminishing-effect ways (UNDP 2004; IPCC 2007; Mertz et al. 2009); however, those are usually incompatible with the complicated happening of climate change; demanding researches that are more systematic and in a long-term way. Accordingly, adaptation is a process finding responding measures to the influences of climate change basing on the basics of principles: interim adaptation is considered the start of pain-relieving process in long-term one; adaptation takes place in different levels, including local one; appropriate to the development context according to the phases strategy; adaptation strategy requires the participation of relating sides (UNDP 2004; Interview 1, 9, 10); adaptation is the adjustment in natural or human system in order to respond to climate conditions in the past or in the future or their influences or consequences— may be advantages or disadvantages; is the self-organizing process to optimize functions of the system, creating new necessary figures or modifying structure to be proper to events and impacts (Smit et  al. 2001; Chrisna 2008; IPCC 2012; Sam 2016); adaptation needs integrating in development activities of all branches and fields; not merely one subject or a specific field or a country but requiring every country’s cooperation (Barnett et al. 2008; Godefroy and William 2014; Interview 1, 9). However, it is vital to ensure the peculiarity of each regions, for example: South Korea has implemented policies in up-to-down approach by enacting relating policies, like: Framework Law of Low Carbon and Green Growth, response plan and the establishment of the Executive Board from the Government and National Assembly (Jung et al. 2012; Kim 2013; Norton Rose Fulbright 2011; Niederhafner 2014). The Japanese Government focuses on constructing a low-carbon society, reducing emissions in transportation, building greenhouses, renewable energy, and green energy (Okazumi 2008; Notomo 2013). Communities can proactively adapt to changes; however, at present, policymaking is dominated by competitive priorities and beneficial group that is less relating to climate change in view of the long process of adaptation, demanding strategy developments with suitable pathways, continuously and repetitively, not a simple agreement (Smit et al. 2001); adaptation is growingly put into awareness since the consciousness of human combined with advances of technology have contributed significantly to enhancing the precision of climate-change forecasts, especially in developing countries—most vulnerable demanding integrated strategies in development plans, programs (Mertz et al. 2009; Interview 1, 9, 10). Developing countries desiring reducing poverty, performing sustainable targets wonderfully depend on executing successfully responding measures to climate change (Davidson et  al.

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2003); because production methods and livelihood activities depend on natural resources, agriculture takes up a large proportion in the economy, the majority of residents join in agricultural-livelihood activities, therefore, any natural changes, climate especially will have a severe impact on income, economy (Barbier et  al. 2009; Mertz et al. 2009; Interview 1, 10). Vietnam is categorized into one of 10 nations that have been and will be impacted severely by climate change (Dasgupta et  al. 2007). Climate change influences remarkably on regions, especially on deltas, in which the Mekong Delta is considered to be one of the most seriously affected (Dasgupta et al. 2007; Nguyen 2007; Le and Suppakorn 2011; Long et al. 2017); figure which challenges substantially rural livelihood with major livelihood activities that are agriculture and aquaculture (Long et al. 2017; Ngo 2016; Interview 1, 2, 10, 11). To respond to erratic, complex changes of climate phenomena, regulatory agencies, organizations, and residents have performed measures in diminishing-effect ways; however, achieved results remain limited, solutions to events and status are temporary, not lasting; residential communities are having to withstand against the developments of climate change and disasters (World Bank, ADB 2018; ADB 2017; Ngo 2016; Interview 1, 10). In addition, in the current developing context, Mekong delta is facing both opportunities and challenges from the developments lacking internal sustainability and external challenges. Therefore, it is necessary to attain more suitable approach in responding works to climate change; combine the historical elements with forecasts of climate hazards in plan; approach synthetically regions, including natural—ecological and social components in order to research affects from both challenges and opportunities for developments (Delta Programme 2017; Amanda et al. 2016; Holly et al. 2012; Matthew J. Colloff et al. 2017). This research, whose analysis clarifies the socio-ecological approach with core which is to analyze relationship among systems in specific region combined with chronological figures will provide information ensuring the science and harmony of systems, which later become the basis to propose responding framework appropriate to the viewpoint “respect, utilize nature” while choosing development paradigm.

4.2 Research Methods 4.2.1 Approach to Socio-ecological System (SES) Socio-ecology is a research method that first appeared in the 1990s with the birth of ecosystem-service definition, and theory of recovering ability, and has been gradually developed, and completed through research works applied to different territories (Folke et al. 2003; Glaser et al. 2008; Ostrom 2009; Hamann 2016; Fikret et al. 2016; WCS 2017; Stefan 2018); in which, must-be-mentioned conception of Ostrom 2009, supposes: “Socio-ecology system is an intricate integrated system including social system, ecological system having mutual support together”, with

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approach connotation featured by a coherent system of natural and social elements, always exist the interactive relationship hierarchically in dynamic equilibrium, ensure the formation of important resources to develop, all in nature, socio-­ economy, culture; concurrently possessing adjustment ability to continuously adapt (Ostrom 2009; WCS 2017). Or, a geophysical entity combined with social actors and organizations, having intricate, adaptive features and mutual-support relationships. The transformation of socio-ecological system may commence from the changes of ecological figures owing to the impact of climate change or others, then is the shift of ecological system leading to adaptations of social figures, including changing in the use of ecological system, livelihood, and resource-administration services (Matthew J. Colloff et al. 2017). Administration of territorial adaptation requires access to system of subjects in the proper context to wisely make decision, especially concerns the link, mutual support of ecological system and social system (Russell Gorddard et al. 2016; Fikret et al. 2016). Russell et al. (2016) have suggested decision-­making paradigm based on research results of mutual support of variables of value, rules, and knowledge. The interaction of them will limit selected solutions that are practical or possible on the basis of motivation of context, decide, and overcome the disadvantages of the process of order administration according to rules form. This method will assist administrators recognize and analyze critically the essence of society in a specific territory, concern enough the social system in the process of proposing adaptation framework. Administration activities contribute to addressing social issues and creating social opportunities, including: establish and apply regulations modifying suitable interaction. The most important figure in analytical framework is “interaction”—central position, it is a specific action, performed by subjects; institution holds a significant role in harmonizing relationships of mankind and nature (Kooiman et al. 2005; Scott L Collins et al. 2010; WCS 2017). Approach to socio-ecological system is regarded as an efficient territorial management tool through research on the two-way connection between human and nature, which emphasizes that human is an inseparable part of nature (Berkes and Folke 1998; Marta and Janet 2016). Socio-ecology is the approach in system thinking, the component structures have a mutual interaction, always in dynamic equilibrium with continuous adaptation; is determined in different territorial scales, may be connected according to classes; consists of a set of resources important for development, maintenance and adjustable; however, this approach requires resource for remarkable research in order to clearly analyze variables, motivations based on the interdisciplinary basis, integrated different qualitative, quantitative methods (Redman et al. 2004; WCS 2017; Stefan 2018; McGinnis and Ostrom 2014; Juan et al. 2020); hence, assess, recognize more clearly subjects in the interaction relationship for managers to determine proper management method, so that at the same time satisfy the demand of development and ensure maintenance as well as promote ecological services; simultaneously, determine more efficient development resources of territory in the way of sustainability, proactive response to challenges of environment based on the basis of the principle “ensure the specificities and characteristics”, enhance the defensive ability appropriate to the threshold limit of

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territory through analyzing the essence of socio-ecological system (Chrisna 2008; Ostrom 2009; Michael et al. 2014; Fikret et al. 2016; Stefan 2018; Juan et al. 2020). The approach of socio-ecological system has been, by many scholars, applied in different scales, fields to achieve the target of territorial sustainable development on the spirit of respecting rules of nature-society, differences in order to seek for the most proper and efficient territorial management method. This post concentrates on analyzing the structure of socio-ecological system and the mutual interaction within the territorial region of the Mekong delta in Vietnam; research result is the rudiment to propose the framework of proactive adaptation to climate change.

4.2.2 Influences of Climate Change on Mekong Delta The Mekong Delta is at the end of Indochinese peninsula with the natural space of approximately 40,000 km2, population about 17.3 millions of people, accounting for 12.3% natural space and 17.9% population of the whole country, in which 75% inhabitants chiefly reside in rural area of 13 administrative province units (General Statistics Office 2020); has a 736 km-long coast, taking up 23% of national total coast, and many islands, archipelagos bordering Eastern Sea and Thailand Gulf, has important international water and air traffic between South Asia and East Asia, Indian Ocean and Pacific Ocean, near Southeast Asian countries—a dynamic economic area with plenty of link potentials for developments (Vu 2004; Vaidyanathan 2011; Ministry of Construction 2016). The Mekong Delta is one of large and fertile deltas of Southeast Asia and the world; located in the downstream of Mekong river with two branches Tien Giang and Hau Giang, pouring to the sea through 9 estuaries; hydrological regime varying seasonally is fairly thoughtful, flood season occurring from June to November accounts for 90% of overall water annual which causes floods, immersing roughly 35–48% space; dry season happening from December to May takes up 10% of total water, in which, March and April have the driest flow, with the climate characteristic of humid subtropical climate, high temperature, unlikely to differ in year has facilitated to develop important agricultural production, one of two main agricultural production areas of Vietnam, especially producing rice (Le et al. 2004; Ziv et al. 2012; Anthony et al. 2015) with area accounting for 54.48%; quantity for 55.9%, the major source for rice export (General Statistics Office 2020). Nevertheless, in the process of territorial development, this region is also having to struggle with several challenges, for instances: influence of benefiting water from upstream; ­cultivation methods have not ensured the harmony with natural environment…, most severely the consequences of climate change, all of which have contributed to the increase of harsh weather phenomena, causing adversities for residential lives and whole-region development (Anthony et  al. 2015; Le 2016; Ministry of Construction 2016; Ha 2020; Interview 1, 9, 10). Climate change and raising sea level are reasons for serious disadvantages of the development process, along with the practices of more and more erratic and

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unpredictable flooding, saltwater intrusion and drought (Ministry of Natural Resources and Environment 2016; Ministry of Construction 2016; Interviews). According to the average emission script, in the middle of this century, the temperature rise is 1.3 °C ÷ 1.4 °C; at the end, it becomes 1.8 °C ÷ 1.9 °C; the middle-­ century average rainfall increases by 5.8% ÷ 20.6%; annual rainfall tends to rise but mainly in rainy season, in dry season the tendency is 3% ÷ 15% decrease; droughts are more severe due to that; sea level rises by approximately 22 ÷ 23 cm in 2050 and 53 ÷ 55 cm in 2100. If it becomes 100 cm, 38.9% of region space will be affected, in which the locals suffered the most are Hau Giang (80.62%), Kien Giang (76.9%) with the most considerable level of saltwater intrusion in April, May annually then falling off from March, February, January, June, July, August, September and most weakened in October; in June, saltwater is pushed far to coastal regions because of the freshwater boost from upstream (Le 2016; Ministry of Natural Resources and Environment 2016). In recent years, the effects of saltwater intrusion phenomenon are promoting because the flow in dry season is low, which contributes to the quite serious saltwater intrusion, simultaneously the underground water sources decrease remarkably; estimation that at the peak—from the middle to end of April, roughly 45–50% of Mekong Delta space will be salty. The disparity of underground water level between rainy and dry season may reach 12–15 m. This is a tremendous challenge to water supply for residential living and producing in coastal plains (Le 2015). Together with temperature rise, it has broken the nature laws of seasons, increased the frequency, intensity of hot, drought, flooding; Droughts lead to saltwater intrusion, only in Mekong Delta, the space of farming land regularly salty is 676,000  ha, accounting for 40% of total 1.7 million ha agricultural land. In dry season, the space of land in Mekong Delta affected by tides causing saltwater intrusion may reach nearly 1 million ha. Typically the saltwater intrusion and drought in the period of 2015–2016 due to consequences of El Nino is one of the reasons for shortage of total average flow amount in years, leading to almost every estuary salty from 50  km to 70  km; 11/13 locals announced the drought, saltwater intrusion disasters status; this period is reviewed as most serious within 100 years, surpassing the salinarity forecast to 2050 (Ministry of Natural Resources and Environment 2019; FAO 2016; Interview 1, 9) (Fig. 4.1). Threats and risks from water resources due to adverse effects of climate change and sea level rise have damaged notably with damage extent increasing day by day, about 21.9 thousand billion VND in the period of 2010–2020. Of all disaster types, drought and saltwater intrusion hold the most severe, for example: in year-on-year 2015–2016 period, all locals within the region declared disasters of drought and saltwater intrusion on a large scale with nearly 140 thousand ha of rice damaged, over 50% of space totally lost revenue; approximately 400 thousand households equivalent to 1.5 million people suffered living water shortage; damage calculated by money was up to 7.5 thousand billion VND; the most severely affected locals were: Ca Mau, Kien Giang, Ben Tre, Bac Lieu (Ministry of Agriculture and Rural Development 2016a, b; Interviews). Recently, drought and saltwater intrusion have continued to impact on the region; in which, saltwater intrusion has reached 70 km, estimated damage is 8 thousand billion VND; 230 thousand ha of rice and fruit trees

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Fig. 4.1  Inundation map with a sea level rise of 100 cm in the Mekong Delta. Source: [Ministry of Natural Resources and Environment 2016]. If sea level rises 100 cm, approximately 38.9% of Mekong River Delta would be at risk of flooding. Among them, the provinces having the highest risk of inundation are Hau Giang (80.62%), Kien Giang (76.86%) and Ca Mau (57.69%)

influenced; roughly 100 thousand households are at risk of living water shortage, estimated damage in economy will be over the ones in 2015–2016 period (Ministry of Agriculture and Rural Development 2020). If the sea level rises above 1 m, without responding activities, most of Mekong Delta space will be immersed for long in a year and the estimated asset damage may come up to 17 billion USD (Ha 2020; Interview 1, 9) (Fig. 4.2). On the other hand, in the period of 2016–2020, the Mekong Delta region continues to suffer the erosion of river and coastal banks with unprecedented frequency and scale in over 300 years of its development. Erosion directly threatens people’s lives and property, seriously affects the safety of coastal natural disaster prevention and infrastructure and degrades coastal mangroves. The total damage caused by bank erosion of the Mekong Delta in March 2020 was more than 130 million USD (Nguyen et al. 2020) (Fig. 4.3). The article focuses on the territorial area on the mainland of the Mekong Delta and conducted field surveys in the two provinces of Soc Trang and Ben Tre in the coastal sub-region to: (1) Clarify assumptions from the secondary data on the natural and social system characteristics of the sub-region; (2) Understand the challenges of climate change to natural systems, social systems, especially production modes of communities and people; (3) Evaluate strategies to adapt to climate change of communities and residents in maintaining production modes. Data was collected

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Fig. 4.2  Map of salinity distribution in the Mekong Delta from 01-05/5/2020. Source: [National Centre for Hydro Meteorological Forecasting 2020]. The salinity level of four grammes per liter is forecast to evade 67–120 km deep into the Vam Co Dong and Vam Co Tay rivers, 18 km into the Cua Tieu and Cua Dai rivers, 10–30 km into the Ham Luong River, 17–32 km into the Co Chien and Hau rivers, and 35 km into the Cai Lon River

through 17 in-depth interviews with 84 people (60 residents and 24 local officials) in October 2020 (Table 4.1).

4.3 Outcomes and Discussions 4.3.1 Socio-ecological System of the Mekong Delta Socio-ecology is proven to be a possible approach in management thanks to its suitability to territorial practice, ensuring the quick-adapting ability, social approvals, especially in deltas, such as the Mekong Delta—climate change is determined a figure increasing the variability of the ecological and social systems of the region with majorly negative impacts leading to defensive degradation of ecosystem, increasingly serious hurt, specifically whereas the conditions of management capacity, responding ability of authority, community and residents remain limited and depend on natural resources—ecology. In which, water is regarded as emblem,

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Million USD

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Province/City Fig. 4.3  Total damage due to the riverbank and coastal erosion in the Mekong Delta period 2010–2020 in USD. Source: Authors’ calculations based on the report on riverbank and coastal erosion by the General Department of Water Resources and the report on river erosion in 13 provinces of the Mekong Delta (2020). There is a difference in the extent of damage caused by erosion in different provinces. The coastal provinces (Soc Trang, Ben Tre, Bac Lieu, Kien Giang and Ca Mau) suffered greater damage than others with damage from 7.8 to 38.6 million USD

attached to human activities. The characteristic of water distribution is the ground to form using methods, association patterns, and populations community. The history of community development and water control are significant components of national administration with conventions, statutes of water management together with disaster mitigation from community to central level. Nowadays, with increasing consequences of climate change, water control is gradually urgent (Le 2016). The socio-ecological system of research area is determined based on the characteristics which have the peculiarities of ecological conditions—the combination of natural conditions and resources, interacting each other creating natural power-­ source in a specific area for socio-economic development (Tran 2015); social characteristics are determined according to the features of culture, society expressed through the major production method—use of territory. From the basis of signs of the (relative) uniformity of socio-ecological characteristics along with those of spatial and time differentiation, of development motivation, the relation and the reciprocal impact among figures and components, the research area is divided into four sub-regions, which are: Dong Thap Muoi sub-region (16.1%), Long Xuyen quadrangle sub-region (10.8%), Central sub-region (30.5%) and Coastal sub-region (42.6%) (Table 4.2, Fig. 4.4). From the general characteristics of the sub-regions, it shows that: Basically, it is created from low ground, recent silt in Dong Thap Muoi, Long Xuyen quadrangle, central sub-regions; the coastal one stands out for its dunes, mangroves with an elevation high of terrain is 0.7–1.2 m, descending along the Cambodia border to coastal region (0.3–0.7 m) (Interview 1, 9). Settlement form attaches to terrain conditions, rural residents distribute along rivers, traffic roads; urban population disperses on the whole region, majorly distributes in alluvial regions and high mounds,

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Table 4.1  Information of interviewees Interview number I 1

3

Interviewee Soc Trang Province Soc Trang provincial People’s Committee (1 male), Department of Natural Resource and Environment (2 male, 1 female), Department of Planning and Investment (1 male, 1 female), Department of Labour, Invalids and Social Affairs (1 male, 1 female), Department of Agriculture and Rural Development (1 male, 1 female) Cu Lao Dung District People’s Committee, Department of Agriculture and Rural Development (1 male); Cu Lao Dung Town People’s Committee (1 male); An Thanh Nam Commune People’s Committee (1 male, 1 female) Farmers (1 male, 4 female)

4

Farmers (5 male)

5

Farmers (3 male, 2 female)

6

Farmers and Aquaculturist (5 male)

7

Farmers and Aquaculturist (5 male)

8

Aquaculturist (5 male)

II 9

12 13 14 15

Ben Tre Province Department of Natural Resource and Environment (3 male); Department of Planning and Investment (2 male, 1 female) Department of Agriculture and Rural Development (3 male, 2 female) Ba Tri District People’s Committee (3 male); Ba Tri Town People’s Committee (1 male, 1 female); Bao Thuan Commune People’s Committee (2 male) Farmers (3male, 2 female) Farmers (1 male, 4 female) Farmers (5 female) Farmers and Aquaculturist (2 male, 3 female)

16

Aquaculturist (5male)

2

10 11

Location

Number of people interviewed

Soc Trang City

4

Cu Lao Dung Town

4

Cu Lao Dung Town Cu Lao Dung Town Cu Lao Dung Town An Thanh Nam Commune An Thanh Nam Commune An Thanh Nam Commune

5

Ben Tre City

5 5 5

5

5

6

Ben Tre 5 City Ba Tri Town 7

Ba Tri Town Ba Tri Town Ba Tri Town Bao Thuan Commune Bao Thuan Commune

5 5 5 5 5 (continued)

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Interviewee Aquaculturist (5male)

Location Bao Thuan Commune

Number of people interviewed 5

Source: Authors’ research results (2020) [NAFOSTED—Vietnam’s National Foundation for Science and Technology Development 2019]

between urbans distancing 60 km. The soil of the research area predominantly is acid sulfate soil group accounting for 41.1% of region’s space; distributes in all sub-­ regions, yet holds the majority in Dong Thap Muoi and Long Xuyen quadrangle. Next, the alluvial group takes up 30.4%, and has terrain basically higher than those of acid sulfate soil group and saline soil group; distributes mainly in central sub-­ region. Saline soil is 19.1% of space; distributes largely in coastal and a part of Long Xuyen quadrangle sub-regions; the remainder are types of grey soil, yellowish red soil (Ton et al. 1991). About the likelihood of flood and saltwater intrusion, there are two sub-regions: Dong Thap Muoi and Long Xuyen quadrangle primarily flooded by flooding, possibly above 3 m in comparison to sea level; barely affected by saltwater intrusion phenomenon, only the coastal area of Long Xuyen quadrangle can be salty up to 12 g/L; the sub-region flooded by tides with level of 1.5 Acid sulfate soil, alluvial soil 10.8 1.6–2 Acid sulfate soil, saline soil

Characteristic values Ecological featuresa

Table 4.2  Characteristics and values of the socio-ecological sub-regions of the research area

8.4

20.57

Proportion of fishing-­ aquaculture area 2.03

19.8

23

31.8

30

Proportion of agricultural Urbanization income rate 19.6 17.6

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Saltwater Flooded intrusion Production level (m) (g/L)c method ≤1 (tides) ≥20 – Aquaculture – Coastal protection forests – Agriculture: fruit trees

Social featuresb Proportion of agricultural-­ production area 22.9

Proportion of fishing-­ aquaculture area 69

Proportion of agricultural Urbanization income rate 28.5 22

Source: Authors’ research results (2021) a  Ministry of Construction (2016); Ton et al. (1991); Soils and Fertilizers Research Institute (1991); Primer Minister (2012); Pham et al. (2011); Vu (2004) b  Ministry of Agriculture and Rural Development (2016a, b); General Statistics Office (2020); Bong et al. (2018) c  Ministry of Natural Resources and Environment (2016)

Terrain Area Percentage altitude No Sub-region (km2) (%) (m) Soil 4 Coastal 16,745.6 42.6 60 m and is interpreted as periodic for a long distance and may be over the entire bar exposure bar abandonment surfaces marked by concave upward to downcurrent mud deposition and incipient soil dipping development

Description Gentle (50 m; poor internal reflections are typical of these zones and are common TNL and TOL bars

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7.4 Results 7.4.1 Radar Facies Reflections RF1 (High Amplitude, Discontinuous Trough-Shaped Reflections) Small-scale, concave-up, discontinuous reflections are superposed on one another in an en échelon fashion forming a laterally extensive zone. Some of the smaller surfaces are confined within the concave up surfaces. Rarely some asymmetric, convex-up surfaces are also present. The concave-up reflections are about 2.5  m wide and 0.5 m deep. The zones marked by superposed concave-up reflections form zones that are on an average 1.5 m thick and can be traced over the entire GPR section for more than 70 m. Usually, these zones of trough-shaped reflections are alternately placed with reflection-free zones (Table 7.2). Interpretation The concave-up discontinuous, superposed reflection surfaces represent tough cross strata formed due to migration of 3-D dunes and, less common, weaker reflections confined within these trough-shaped surfaces represent reflection from the foresets. The asymmetric convex-up surfaces represent preserved top surfaces of the 3-D dunes (Woodward et al. 2003; Sambrook Smith et al. 2005). As evident from the GPR data the trough cross-stratified sands form laterally extensive zones and lack surfaces typical bar accretion surfaces (c.f., RFA 2, 3, 7, Table 7.2). The prominent reflection from trough cross-set bases may be due to moisture saturation of these zones whereas the alternating zones of sediment characterized by poor reflections or absence of it, plausibly represent drier, more homogenous fine sandy units. RF2 (Series of Low-Angle Inclined Reflections) Each of the reflections dip less than 10° and such reflection sets are laterally extensive for more than 20 m and spans over a depth of 1.2–1.6 m. In some cases, dip of the reflection surfaces becomes gentler at the distal end of the set; the basal bounding surface of the low-angle reflection set is slightly undulating. Some of the south-­ dipping low-angle reflection surfaces show off-lapping geometry. Interpretation The lateral and vertical extent of the sets of low-angle reflections indicate they are much larger than the individual medium-scale planar cross sets encountered in the exposures of the Tista modern sediments and clearly represent the bar accretion

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surfaces enclosing between them smaller cross strata (Best et al. 2003; Lunt and Bridge 2004; Sambrook Smith et al. 2006; Ashworth et al. 2011). Off-lapping pattern and gradual decrease in the accretion surface slope are common in many reported ancient and modern braid bars (Allen 1983; Chakraborty 1999; Bridge 2003, p. 233; Sambrook Smith et al. 2006; Reesink et al. 2015) and denote progressive aggradation and advancement of the bar margin into flanking pools that becomes shallower in the distal margin of the pool resulting in gentler inclined surfaces. RF3 (Low-Angle Upstream Dipping Reflections) These are comparatively uncommon but continuous high amplitude reflections that dip at low angle (≤6°) to the upstream (northern) direction. Laterally they merge with sub-horizontal or downstream dipping surfaces and are mainly recognized in TOL bars (Figs. 7.2a, b and 7.3).

Fig. 7.2  Riverbank section of a pre-dam bar. (a) TOL bar with major bounding surfaces marked highlighted by pink line. (b) A cleaned and scrapped section of a part of the same bar and schematic representation of the internal structures of the bar. (c) A flow parallel GPR profile of the above bar. (d) Interpretative sketch prepared from the GPR tracing. Solid bold concave up lines  =  channel scours; dash-dot-dash lines and dotted lines  =  low angle downstream accretion surfaces; dashed lines = upstream dipping reflections; bold continuous lines = probable mud layer; red convex up surfaces  =  diffraction hyperbola produced due to presence of vegetal matters (stem, wood)

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Fig. 7.3  A ~ 2 m high cut bank section of a TOL bar near village Padamati. ‘C’ represents the downcurrent dipping cross strata in the bar front; note sigmoidal cross strata and associated low-­ angle strata. ‘B’ represents the upstream dipping sets of parallel strata on the bar back. ‘A’ represents the bar top fines

Interpretation Upstream dipping accretion surfaces are common features of many braid bars that denote climbing of the smaller bedforms over the upstream dipping stoss surface of the bars (Miall 1987; Bridge 2003; Lunt and Bridge 2004; Reesink et al. 2015). RF4 (Isolated Larger Concave Reflections) These concave surfaces are distinguished with the RF1 concave-up reflection sets because of their larger dimension and isolated occurrences. These concave up reflections cut through several sub-horizontal surfaces. These reflections are 5–15 m wide, 0.5–1.6 m deep. One more important feature of this reflection surface is that its hollow is filled up with either reflection-free sediments or sediments that shows few weakly developed reflections. Interpretation Erosive downcutting into earlier deposits, isolated occurrences and larger dimensions indicate these are small channels. Minor channels, anabranches or low-stage cross-bar channels are associated with all types of braided fluvial bars (Miall 1987, 1992, 1996; Bristow 1993; Bridge 2003; Lunt et  al. 2004). The diffused

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reflection in the channel-filling sediments is probably related to well-sorted finegrained sand with smaller bedforms below the resolution of the 200 MHZ GPR antenna. RF5 High Amplitude Isolated Low-Angle Surfaces These surfaces are laterally extensive for more than 50 m and usually show a sub-­ horizontal dip. Although these surfaces are very prominent, they are represented by one or two reflection surfaces. These surfaces at place show a broad concave up geometry (Fig. 7.2). Such reflections are uncommon and occur in two places among the studied bars of the Tista River. Interpretation These deposits possibly reflect thin mud layers occurring over extensive surface. Probably these muddy reflectors were deposited after bar abandonment (Fig. 7.2). A shallow bar top pond after bar abandonment can produce thin concave-up mud drapes over extensive surface. RF6: Reflection-Free Zones In many places, a zone of river sediment is visible that lacks well-developed radar reflection surfaces. These zones can be tabular, laterally extensive or confined above a concave up surface. The zones vary from 0.5 to 1.5 m in thickness and can be laterally traceable for 5 to 50 m. Interpretation Strong reflection surfaces, marked by sharp contrast in the lithology of the overlying deposit, may cause attenuation of signals immediately below (Sambrook Smith et  al. 2006, 2009). However, concave channel-fill zones with indistinctive reflections may also be related to finer, uniform grain size and smaller bedforms in the channel fills. In some cases, the top of the exposed succession in the river cutbanks, comprising fine sandy material, may be homogenized due to pedoturbation and can result in such reflection-free zones (top of Fig. 7.2). RF7: High Amplitude Convex-Up Reflections These are isolated high amplitude continuous reflection surfaces with a convex-up profile shape and extend laterally for 4 to 12 m, having an elevation varying from 0.5 to 1.0 m. In contrast to similar convex-up reflections of RF1, RF7 reflections are

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larger in dimension, nearly symmetrical to weakly asymmetrical in profile shape and occur as isolated features in the GPR profiles. Interpretation The height and extent of the isolated surfaces indicate that these mimic the preserved top of the macroforms rather than that of smaller individual bedforms. Similar surfaces have been assigned fourth-order bounding surfaces in the classification of architectural elements (Miall 1987). The bars when abandoned probably had a draped fine muddy material at places that helped GPR to pick up these reflections from the top of the macroform. However, as in the ancient rock record, preservation of the bar top surface is rare in Tista sediments. RF8: Set of High Amplitude Parallel Reflections This radar facies is differentiated from the other low-angle reflections mainly on the basis of the thickness and high lateral continuity of the reflection set. Low angle discordances between sets of reflection are observed at places. Similar thick parallel stratified sedimentary facies are also observed in some of the exposed bar sections. The succession of parallel reflections is underlain by tough-shaped, inclined, and channelled reflection pattern of RF1, 2, and 4 (Fig. 7.6). Interpretation The dimension of the parallel reflection indicates that these represent extensive, sheet-like units of strata, and as revealed by their correlative surface exposures these radar facies represent extensive sheet of parallel stratified deposits (Fig. 7.7). The broad scours at the top represent low stage channelized flow. The underlying units represent other radar facies of trough cross-bedded, down current accreting or scour channel facies (RF1, 2, 4).

7.4.2 Facies Analysis Based on the combination of the sedimentary structures, lithology and geometry of the lithosome, eight (8) sedimentary faces have been identified in the Tista River deposits (Table 7.3). Based on the repeated occurrences of a preferred combination of some of these facies, four facies associations have been defined (Table 7.4). The characters of the facies associations and their interpretations are described below.

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Table 7.3  Facies recognized in Tista River sedimentary deposits Name (F1) Mud-silt beds

Description It consists of mud/clay beds with interlayered current or wave-rippled silt layers; thickness of muds varies from 10–46 cm and silt layers 5–15 cm thick; mud is massive with abundant iron-encrusted root traces and rare desiccation features; burrows (mostly Skolithos and Taenidium) occur locally; thin mud layer at one section is continuous for more than 60 m

Fine sandy layers (F2) Ripple laminated very occurring on top of the fine sand succession of cross-­ stratified sandy beds; ripples are mostly unidirectional, trough shaped and range in size from 0.5–2 cm Swarms of trough-shaped (F3) Large cross strata occur trough cross-stratified commonly within the fine-grained sand, cross fine sand strata 20–55 cm thick; cosets up to 1.9 m thick; may occur as isolated sets (F4) Medium Planar cross strata usually to large planar occur in coarse to medium cross-stratified sand, vary in thickness fine to pebbly from 20 to 65 cm; at places pebbles concentrate coarse sand near the bottom boundary of the sets (Fig. 7.5); sets may occur over upcurrent or downcurrent inclined bounding surfaces

Geometry and other features Usually, these beds occur at the top of the section forming a sheet-like unit and grades upward into vegetation-rich incipient soil layers; at places the facies fill-up shallow scours with lenticular geometry

Interpretation Mud beds deposited under sluggish water during abandonment of the bars; presence of roots and upward gradation to insipient soils corroborate this; presence of wave rippled silt beds, insect burrows at places indicate presence of pool of water as is common in abandoned bar tops/ floodplains (Griffing et al. 2000; Bridge 2003); extensive mud layer indicate large pool of ponded water Resulting from migration Broad lenticular of 3-D ripples in sluggish geometry; migration direction variable and low-stage cross channels at places at high angle as evident from their to the large cross beds geometry and grain size in the associated sand beds Usually occur in swarms forming a sheet-like sand body; paleocurrent is dominantly to SE, locally variable

Result from migration of large 3D dunes; fine grain size is a function of grain-size limited sand supply; usually common in TNLs

In many cases planar cross strata grades into sigmoidal cross strata and low-angle strata

Deposited from migrating 2D dunes that form at shallower depth as compared to trough cross strata; coarser grains were concentrated near the base of a set through gravel overpass in a mixed load supply (Allen 1983). Lateral transition indicates increasing flow velocity (continued)

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120 Table 7.3 (continued) Name (F5) Large sigmoidal cross-stratified sand

(F6) Parallel stratified sand

(F7) Fine to medium sand with centroclinal cross strata

Description These generally comprise medium to very fine-­ grained sand with sigmoidal cross beds, interlayered and grading into low-angle cross beds or low-angle parallel strata; in rare instances they form in pebbly sand as the pebbles concentrate near the base of the set; sigmoidal cross strata are 35–55 cm thick, often occurs in successive sets forming a coset of sigmoidal strata

Geometry and other features Upstream-downstream gradation to parallel strata common, also upward gradation to the same; paleocurrent directions tightly clustered around SSE

Interpretation Sigmoidal cross strata are the product of downcurrent accretion of humpback dunes forming at the transition between lower and upper regime flow condition (Bridge and Best 1988). The sigmoid cross strata with pebbles concentrated in the steep foresets is similar to that recorded by Allen (1983); similar bedforms have been recorded from many fluvial successions experiencing high-velocity flow (Røe 1987; Fielding et al. 2011) Parallel stratification result Closely associated Parallel stratification is common in most TOL bars with sigmoidal cross from the migration of low-relief bed waves beds but in many but are also seen in TNL under upper flow regime bars, comprising mostly of places occur as independent extensive (Best and Bridge 1992); fine-grained sand; lateral transition with unit; shallow scours thickness of the parallel stratified units varies from often mud-filled occur sigmoidal strata confirms at places on top of the close to upper flow regime 15 cm to 75 cm and the conditions; extensive units thicker units can be traced plane bedded units of parallel stratification laterally over few 100 m; record a high energy flood slight change in the grain in the river; scouring at the size and proportion of top by low-stage channels biotite defines the strata The symmetrical The inclined strata formed Closely associated trough-like structures around decayed plants and with low-angle formed as the sediments laminated strata may apparently be filled-up the depression misidentified as deformed created by the in situ trough cross strata. The plants roots/trunk (now invariable relation with the only decayed trace) and in situ vegetal matters, are known as centroclinal scour-filling geometry and cross strata; forms a part isolated nature is notable; of a broad group of these strata vary in structures named VISS thickness from 10–42 cm (vegetation-induced and are associated a host sedimentary structures) of other deformational (Underwood and Lambert features 1974; Rygel et al. 2004) (continued)

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Table 7.3 (continued) Name (F8) Fine sand- to mud-filled scour structures

Description Trough-shaped scours frequently occur on top of the bar successions; the size of the troughs varies from a few to 50 cm in depth; the scours are variously filled with sandy foreset layers, ripple laminated silt or thinly laminated mud

Geometry and other features In many cases the axis of the scour is at right angle to the dominant southward flow of the other structures

Interpretation The incising nature of the scour, their variable fill character and their axis orientation at high angle to the paleoflow indicated by other associated structures imply origin of the scours from sluggish, small, late-stage channels flowing over the bars (Bluck 1979; Chakraborty 1999)

Table 7.4  Facies association of Tista River deposits

Facies associations FA1: River bar succession

Constituent facies F4, F5, F6; subordinate F1, F2, F8; locally F7

Bed geometry, paleocurrent and trace fossils Description In large Planar/trough cutbank cross beds and sections, FA1 parallel stratification form succession shows a a succession of dominantly sand sheet-like to convex-up that shows both geometry; upstream and downstream paleo-­ inclined patterns transport (Figs. 7.2 and direction is 7.3); the parallel grossly stratification is towards SE, closely parallel to the interrelated with direction of sigmoid cross dip of the strata; small to coset medium-sized bounding scours fills surfaces intervene the coset of cross strata; centroclinal x-strata and other deformations related with vegetation common; gradationally passes into mud-silt beds through rippled fine sands units towards the top of the succession

Interpretation of depositional setting The downstream accreting beds indicate accretion of the bedforms into deeper water in front of a topographic high (a unit or compound bar); similarly upcurrent dipping cosets indicate climbing bedforms on the stoss side of the bars (Bluck 1980; Haszeldine 1983; Reesink et al. 2015; Sambrook Smith et al. 2009, among many others); high proportion of parallel and sigmoid cross strata indicate periodic high discharge; growth of in situ vegetation and centroclinal x-beds denote seasonal character of the monsoon-­ affected stream where most of the precipitation-discharge is concentrated in 4 months of the rainy seasons (Biswas and Bhadram 1984; Ghosh and Chakraborty 2022)

(continued)

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122 Table 7.4 (continued)

Facies associations FA2: Sheet flood deposits

Constituent facies Almost exclusively F6, with some F4 near the base of the succession, grading upward into F8, F2 and F1

Bed geometry, paleocurrent and trace fossils Description The set of parallel The lateral stratification that extent of the is laterally parallel extensive over stratified unit many sections is remarkable spread over and contrast 100 s m, and with FA1 and varies in thickness FA3 deposits between 55 and 230 cm; grain size varies from very fine to medium sand, grades upward into mud-silt layer via ripple laminated fine sand; scour structures are common at top and filled up by rippled, scour-­ filling silty lamination and massive mud

Interpretation of depositional setting Laterally extensive parallel strata indicate upper flow regime condition in shallow, wide channels as reported from modern sheet-flood deposits and their inferred ancient counterparts (McKee et al. 1967; Tunbridge 1984; Abdullatif 1989; Carling and Leclair 2019); the erosive scouring at the top indicate declining flow stage of the river; high stage flow is relatable to the infrequent event of intense monsoonal precipitation and river flood (Basu and Sarkar 1990; Samui 1994; Chakraborty and Ghosh 2010; cf., Fielding et al. 2011)

(continued)

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Table 7.4 (continued)

Facies associations FA3: Monotonous succession of trough crossstratified fine sand

Constituent facies Dominantly F3, subordinate F2, F4 and F6

Bed geometry, paleocurrent and trace fossils Description Form The facies sheet-like association units in the comprises a exposed TNL monotonous bars; succession of remarkably large trough cross-bedded fine lack downcurrent sand; FA3 or upcurrent particularly dipping coset characterize the boundaries or most recent any other (TNL) bars; in large-scale spite of substantial length, architectural elements of width and bars in FA1; thickness, these paleocurrent bars consist of direction is vertically broadly aggrading large trough cross-beds SE-ward but varies locally that show either no discernable change in set thickness and grain size upward or in some cases show a weak thinning and fining upward trend; in a few sections minor planar cross beds and parallel lamination or rippled very fine sand is encountered

Interpretation of depositional setting Coset of trough cross strata are typical of interbar channel areas (Cant and Walker 1978; Sambrook Smith et al. 2006); However, this facies association related to TNL bars that emerge about 2 m above the low-flow level, shows only cosets of troughs and lack any such organization related to the river bars; GPR reflection profile shows that all these bars have similar organization of monotonously vertically aggrading trough beds dominated succession over an area of 80 × 40 m area (Fig. 7.9). We postulate the facies association developed in deeper channels under uniform flow condition carrying fine sand, and the flow stopped abruptly without allowing the bedforms to adjust to the reducing flow depth and velocity, or deposition of low-stage fines

(continued)

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124 Table 7.4 (continued)

Facies associations FA4: Bar top mud-silt

Constituent facies Dominantly F1 with subordinate F2 and F8

Description The succession can be up to 70 cm but are typically 30–40 cm thick; these are often interlayered with few cm thick wave or combined flow rippled silt/ fine sand; scour fill structures of F8 occur at places; mud beds are usually marked by iron encrusted thin rootlets near the top, below the vegetated exposed surface

Bed geometry, paleocurrent and trace fossils Burrows of Skolithos and Taenidium are locally abundant

Interpretation of depositional setting These deposits represent typical abandonment facies of the bars and amalgamation with the flood plain; muddy sediment is deposited in shallow pools; the emergent surfaces were covered by vegetation or incipient soils (Miall 1996; Kraus and Aslan 1999; Griffing et al. 2000)

Facies Association 1 (River Bar Succession) The facies association is best exposed in a riverbank section of a TOP bar (Fig. 7.2). The upstream dipping bounding surfaces in the northern part of the section grades into subparallel bounding surfaces in the central part and further south it changes into gently downstream dipping accretion surfaces (Fig. 7.2a). The upstream part is dominated (between first order surfaces) by parallel and low-angle strata (Fig. 7.3), whereas middle part has some trough cross strata, small channel scours as well as low-angle strata. Larger planar sets dominate the southern part of the section (Figs.  7.2b and 7.3). Well-developed sigmoidal cross strata are common in this facies association (Fig. 7.3); centroclinal cross strata are present at places (Fig. 7.4). Locally, discontinuous, up to 60 cm thick bands of muddy silt with insect burrows are present. In some of the sections, large planar cross strata with sigmoidal foresets of coarse pebbly sand occur (Fig. 7.5). The pebbles are concentrated in the lower part of the cross strata. The facies association grades upward into finer-grained muddy deposits, at places altered to inceptisols with preserved rhizolith structures (Fig.  7.3). The GPR profile of one of the FA1 section (Fig. 7.2c, d) shows all these features including upstream dipping and downstream dipping accretion surfaces and small channel scours.

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Fig. 7.4  Centroclinal cross strata in TOL bar depicted in Fig. 7.2. The decayed tree stem is shown by a dotted line

Fig. 7.5  Coarse grained planar cross strata in a TOL bar. Note sigmoid shape of the foreset and gravel concentration near the bases of the cross strata

Interpretation The upstream and downstream dipping surfaces are inferred as braided bar head and bar front accretionary deposits (Haszeldine 1983; Chakraborty 1999; Lunt and Bridge 2004; Sambrook Smith et al. 2006; Reesink et al. 2015). The smaller channels recognized in the cutbank exposures as well as in GPR sections represent bar top or anabranch channels associated with the low flow stage of rivers. Paucity of

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floodplain deposits, domination of downcurrent accretion elements and evidence of upper stage flow structures (parallel stratification, sigmoid cross strata) are all consistent with a braided bar interpretation. Centroclinal cross strata indicate synsedimentary growth of in situ vegetation (Underwood and Lambert 1974; Rygel et al. 2004). The upper flow regime bedforms together with centroclinal cross strata imply major flow stage fluctuations and a seasonal nature of the river system. All the foothill Himalayan Rivers, including the Tista River receives >80% of its annual discharge within 3–4 months of the monsoon (Biswas and Bhadram 1984; Basu and Sarkar 1990; Samui 1994; Ghosh and Chakraborty 2022) resulting in high discharge flood times interspersed with prolonged periods of low flow, when much of the alluvial plain and bars were exposed allowing vegetation to grow on them. Facies Association 2 (Sheet Flood Deposits) This facies association is dominated by parallel stratified units that vary in thickness from 55–230 cm and can be traced for more than 100 m in the field (Figs. 7.6 and 7.7), and is associated with a subordinate scour-fill silt-mud at the top and rare planar cross strata of facies 4 at the base of the succession. On closer inspection within each few mm-scale parallel laminae, low-angle inclined strata are observed at places; strata thickness varies from 2 to 6 mm. Low-angle discordances are observed between sets of plane parallel strata; different packages of subhorizontal parallel strata are distinguished by variation in the thickness of the laminae (Fig. 7.7). Overlying scours are up to 50 cm thick and show at places multiple episodes of complex filling character and the grain size of different fill-episodes vary from mud to rippled very fine sand. Interpretation Infrequent association with planar cross beds at the base and gradation to ripple laminated scour-fills on the top indicate these are records of waning flood flow with the major stage of the flood depositing upper stage plane beds. Low-angle intra-­stratal cross laminations confirm that these parallel laminations developed in the upper flow regime condition through migration of low-amplitude bed waves (Best and Bridge

m 0 0

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Fig. 7.6  GPR profile of a TOL bar in the downstream part of the study area. Note thick parallel radar reflections, their lateral extent, and trough-shaped reflections at the top. Note the lower part of the succession shows a complex organization observed in other TOL bars (c.f., Fig.  7.2). Orientation of the profile is 150–330°

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Fig. 7.7  Surface exposure of the TOL bar section illustrated in Fig. 7.6

1992). Low-angle discordance between sets of parallel strata and variation in the thickness of the strata probably indicate pulsating surges of events in a sheet flood. Similar planar laminated sheet flood deposits have been reported from both Holocene and ancient fluvial deposits (McKee et al. 1967; Tunbridge 1984; Abdullatif 1989; Chakraborty and Ghosh 2010; Carling and Leclair 2019). The occurrence of the association in TOL bars (pre-dam) and overall extent of the facies indicate that they are the product of one of the major monsoonal flood events that overwhelmed the Tista River occasionally prior to the establishment of the barrage and dams in this valley. Upward gradation into scour-filled finer deposits indicates reworking of the sheet flood deposits by late-stage channelized flow carrying finer material.  acies Association 3 (Monotonous Succession of Trough Cross Stratified F Fine Sand) The facies association is characterized both in cutbank sections as well as in GPR profile, by a monotonous succession of large trough cross strata (Figs. 7.8 and 7.9). The trough sets range in thickness from 20 to 55 cm, can be more than a meter wide in transverse profile and forms coset up to 2 m thick. The trough cross-stratified layers develop into a tabular unit that can be traced along the entire study exposures or all throughout the 80 m long GPR profiles (Figs. 7.8 and 7.9). There is a lack of well-developed gradation of the size of the cross strata and sandy sediment in this facies association, though a weak thinning of the cross-set size and in rare instances a rippled fine sand bed at the top denote a weakly thinning- and fining-up trend. Large planar cross beds are found to occur as isolated and uncommon features. The facies association is typical of youngest or TNL bars that formed after 2010 (as seen

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Fig. 7.8  Coset of trough cross stratified fine sand of TNL bar. Note lack of fining and thinning upward trend in the bar, and lack of downdipping compund cross sets as shown in Figs. 7.2 and 7.3 S m 0 0 1 2 3 m 0 0 1 2 3

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Fig. 7.9  A flow parallel GPR profile of TNL bar that has been illustrated in Fig. 7.8. Thickness of lines in the tracing reflects the intensity of radar reflections in the radar profile

from the satellite image analysis, c.f., Ghosh and Chakraborty 2022). The successions of this facies association lack a significant proportion of other bedforms (F2, F4, F5, F6) or any other architectural elements, like downcurrent or upcurrent inclined surfaces or bar top channel scours of FA1. Interpretation Trough cross beds are generally formed in a higher flow velocity as compared to the planar cross beds in a similar grain size and flow depth (Southard and Boguchwal 1990). The deeper thalwegs in the channels are, therefore, marked by coset of 3-D dune cross strata (Cant and Walker 1978). However, more recent studies demonstrate that 3-D dunes can form on channel as well as in bar deposits depending on

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the flow depth and flow velocity and the mode of growth of the channel bars (Sambrook Smith et  al. 2006). The available data demonstrate that most of the sandy braided rivers (as in South Saskatchewan River) have nearly 10%–30% of the bedforms are high-angle planar cross strata. It is rather unusual that the facies association 3, most commonly encountered in the TNL bars, are almost devoid of planar cross strata or fine sand near the top of the succession. On the other hand, this facies association is typified by monotonous aggradation of trough cross strata and lack complex architecture of the fluvial bars (c.f., Sambrook Smith et al. 2006; Reesink and Bridge 2011). Bar architectures of similar kinds are not commonly reported from fluvial deposits, rather they are believed to have formed in intra-bar channels. It is interpreted that this facies association formed in controlled, steady uniform velocity with significant depth, but the flow stopped abruptly so that the bedforms could hardly adjust to the falling flow depth and velocity, and the bars were exposed rapidly depriving the finer sediment to settle in bar top pools or slough channels. Facies Association 4 (Bar Top Mud-Silt) The facies are essentially fine-grained deposits occurring on exposed bar tops (Fig. 7.3) and have in many cases suffered pedoturbation due to the growth of vegetation. Incipient soil profiles are developed at places with abundant root structures preserved (Fig. 7.10). The lower part of the facies association is often interlayered with wave-rippled silt layers. Insect burrows of Skolithos and Taenidium are present at places. The deposits of this association are usually 30–40 cm thick but may reach a thickness of 70  cm. In some cases, the bar top successions are marked by the occurrences of shallow scours filled up with stratified silt-mud units (Fig. 7.7). Interpretation These sedimentation units represent the abandonment facies of the bars or the deposit when some of the floodplain as older bars accreted to the floodplain. Fine sediment could be deposited in small late-stage cross-bar channels or in shallow ponds that develop on the abandoned tract of the river. Presence of wave-rippled silt or insect burrow indicates submergence under shallow ponded water (Griffing et al. 2000; Zaleha 1997) whereas pedoturbated fine-grained deposits are common in many of the floodplain deposits (Miall 1996; Kraus 1999).

7.4.3 Grain Size of the Tista Bar Sediments We chose two sets of data, one from the pre-dam bars (TOL) and the other set from postdam and barrage bars (TNL) based on our study of the chronology using a temporal succession of LANDSAT images. For both the bar types, samples were taken from both

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Fig. 7.10  A bar top succession in a TOL bar. Note wave rippled silt beds and root penetrated mud deposit at the top

upstream and downstream reach of the study area. We collected 39 samples from the upstream TOL bars and 56 samples from the downstream bars that preceded the Gazaldoba Barrage. Similarly, we collected 12 upstream samples from TNL bars and 16 samples from TNL bars located in the downstream part of the study stretch. Using the dry sieving methods, we determined the D50 and D84 of both the sets of bars and plotted them in the box diagram (Fig. 7.11). In both the sample sets and for both D50 and

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Fig. 7.11  Box plot of the grain size data from TOL and TNL bars

D84 fraction of the samples, the grain size of the downstream is finer than the upstream one. Also, despite overlap and some outlier values, the pre-dam bars are coarser than the post-dam bars. This trend between the pre- and post-dam bars is more prominently displayed by D84. The result of newer sampling and analysis of the pre- and post-dam barrages tends to indicate the fining of the grain size transported by the river in the postdam period. We suggest two principal reasons that may be responsible for this grain size change: (1) The coarser grains transported by the river were trapped by the upstream dams. Thus, the sediment supply in the post-dam stream is overall finer being devoid of the of the coarser components. One indirect evidence of this comes from the gravelly sand deposit present in the old bars exhumed a few km upstream of the barrage. (2) The other reason could be the changing flow pattern of the river in the post-dam period. Our facies analysis data shows that the extreme flow velocities that resulted in the formation of extensive parallel stratified bed or sigmoidal cross strata are common in pre-dam (TOL) bars but are absent in the TNL bars. This would imply that the peak flow velocity of the river was significantly reduced disabling the river to transport the coarse bedload. It is more reasonable to emphasize that both the processes were operating simultaneously to bring about the change in the grain size.

7.5 Discussion By employing the methodology of using satellite images established by Ghosh and Chakraborty (2022), it was possible to identify broad temporal cluster of the bars in the study stretch of the Tista River. In this study we focused on the detailed sedimentological examination of two clusters of bars: (1) The bars that developed (and are still preserved at least in part) before 1998 and were not affected by any major engineering structures; these bars have been nicknamed TOL (Ghosh and Chakraborty 2022), and (2) The youngest bars that developed after 2010 when all the upstream dams and the alluvial plain Gazaldoba Barrage were in operation (nicknamed TNL bars by Ghosh and Chakraborty 2022). The study involved facies analysis of cutbank or trench sections and GPR survey of the selected TOL and TNL bars.

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The study reveals that these two types of bars are distinctly different. The TOL bars are characterized by a variety of sedimentary structures and a complex architecture involving upcurrent and downcurrent accretion surfaces, channel scours, locally developed vegetation-induced structures, evidence of upper flow regime or transitional to upper flow regime bedforms, and generally a fining upwards succession. In contrast, the cutbank sections of the young TNL bars show a monotonous aggradation of trough cross-stratification. The GPR profiles of the TOL and TNL bars show contrasting radar facies emphasizing the differences between the two. The surface exposures of the pre-dam bars reveal the presence of upper flow regime plane beds and sigmoidal cross strata that develop under critical flow (Froude number 0.84 to 10 million. In 2019 the Ministry of Housing and Urban Affairs launched a National Smart Cities agenda (2019–2023) that identified 100 cities across India as part of an urban renewal and retrofitting programme. Within this programme, the retrofitting of India’s ancient cities with modern mass transport and sewerage systems is a major challenge. Whilst thematic geology maps of Indian cities were widely developed in the late 1970s by the Geological Survey of India these were primarily single topic studies for example on water, pollution, soil contamination, flood vulnerability, and engineering (e.g., Kolkata). Multi-theme research was generally not considered one exception being the study of Shimla in the ‘green’ Himalaya by Kumar and Biswas (2013). The study area of Varanasi, situated in the central part of the Gangetic foreland basin (Fig. 9.1), holds significant historical and religious importance as one

Fig. 9.1  Geological map of Gangetic basin (modified after Sinha et  al. 2005) along with the marked study area, Varanasi

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of the oldest and holiest cities in Southeast Asia, associated with Hinduism, Buddhism, and Jainism. Inhabited continuously since, around 1000  BCE, Varanasi has witnessed rapid urbanisation over the past six decades, with its population increasing fivefold and built-up areas expanding sevenfold (Singh 2017). With an annual growth rate of 1.57% since 2015, as reported by the UN, the city’s Master Plan for 2041 (Crisil Infrastructure Advisory 2015) focuses on sustainable strategies to align with SDG 11 and India’s ‘Smart City Development Plan’. In particular, the complex stratigraphic architecture of fluvial systems including overbank flood deposits, meandering channels, and localised lacustrine deposits gives rise to significant lateral and vertical heterogeneity often over relatively short distances (a few 10 s of metres). This has major implications for major underground development projects as highlighted by the problems encountered during the construction of the Kolkata metro system (Banerjee and Sikdar 2020) but also for the understanding of groundwater quality and interaction between shallow and deep aquifers and the River Ganges (Das et al. 2021. Furthermore, the lack of comprehensive published information on underground resource parameters in Varanasi poses risks to construction projects. Unexpected ground conditions can lead to delays, cost overruns, and additional expenses. Therefore, thorough consideration of subsurface geological conditions is crucial to achieving the city’s development goals and mitigating potential risks. In this chapter, we present an approach to developing an urban development vulnerability map for Varanasi that aims to inform city planners and engineers at the preliminary stages of project development. The approach combines cost-effective data measured during shell and auger boring and in the laboratory to calculate various standard parameters that are integrated with the geological investigation. The research aims to underpin the sustainable development of the subsurface by examining the relationship between the quality of the urban underground space (UUS) and the corresponding aboveground conditions.

9.2 Geological Background The late Quaternary geology of the central Gangetic basin at Varanasi comprises unconsolidated sand, silty clay, and occasional gravel deposits. These deposits represent three distinct cycles of deposition (Pathak et  al. 1978; Bhartiya et  al. 1995) (Table  9.1). On the east bank of the River Ganges opposite Varanasi at Ramnagar, Shukla et al. (2012) have described three sedimentary units in the riverbank section and subsequently interpreted core samples from three deep boreholes within the city. More recently, Shaw (2021) has described the complex interaction of climate and tectonically driven fluvial processes as recorded in the geology at Varanasi. The oldest strata are the Banda Group, which range from late

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Table 9.1  Lithostratigraphic sequence of Quaternary sediment fill basin in and around the study area, Varanasi, central Gangetic basin (compiled from Joshi and Bhartiya 1991; Kumar et al. 1996; Shah 2013) Age Holocene

Group Newer alluvium

Middle to late Pleistocene

Older alluvium

Late Pliocene to Banda early–middle Group Pleistocene

Litho-Unit Recent floodplain deposits Older floodplain deposits (terrace deposits) Disconformity Varanasi alluvium

Unconformity Banda Alluvium

Lithology Unoxidised, grey, micaceous, fine to medium sand of active channel deposit, associated overbank silty sand or sandy silt Unoxidised, grey, silty clay and clayey silt underlain by fine to medium-grained, mica-rich sand

Polycyclic sequences of oxidised, yellowish brown to brownish yellow, silty clay to clayey silt (upper part) and yellow to very pale brown coloured micaceous sand (lower part), calcrete nodules and occasional Fe-Mn nodules are common Reddish to deep brown quartzo-feldspathic medium-coarse sand with gravel lenses, silt and clay

Pliocene to early to mid-­Pleistocene (insert age range) in age and include distinctive reddish yellow to brown quartz and feldspar-rich sands and gravels with variegated clays. Mineralogy and geochemical data suggested that the source material was derived from the Cratonic mass of Central India (Bundelkhand Gneiss and Vindhyan terrain) (Shaw 2021). The overlying Older Alluvium, dating from the middle to upper Pleistocene, consists mainly of yellow-brown sandy and muddy deposits containing nodular concretions of calcrete that are typically situated above the highest flood level of the River Ganges and its tributaries. The youngest deposits of the Newer Alluvium were deposited during the Holocene period and include the older terraces, floodplain deposits, and point bar systems primarily located along the banks of the present-day River Ganges. The terrace deposits are characterised by grey micaceous sand, overlain by muddy overbank deposits with subordinate laminated lacustrine muds. In contrast, the floodplain deposits consist of grey sands and muddy sands derived from the river channels (Shah 2013 and references therein). Both the Older and Newer Alluvium sediments have their sources in the Himalayan region. The mineralogy and provenance of the alluvial sediments in Varanasi have been investigated and discussed by Singh (1996), Shukla and Raju (2008), Shukla et al. (2012), and Shaw (2021). These authors differentiate shallower Himalayanderived grey micaceous sub-greywacke sands (up to 60 m depth) from the deeper pink to reddish non-micaceous sub-arkosic sands (beyond 60 m depth), which are interpreted to be of cratonic origin.

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9.3 Methodology and Techniques As part of PhD study (Shaw 2021), a total of 71 boreholes were selected for geological and geotechnical investigations, reaching depths of up to 50 m below ground level (bgl) (Fig. 9.2a). Drilling was conducted using a shell and auger rig, employing rotary mud circulation and operated by a mechanical winch to create boreholes with a diameter of approximately 150 mm, following the guidelines outlined in IS 1892 (1979) (Fig.  9.2b). Undisturbed samples were extracted at regular intervals (ranging from 1.5 to 3 m) along the borehole profiles using a standard penetrometer with a split spoon sampler measuring 450 mm in length, following the specifications outlined in IS 2131 (1981) (Fig. 9.2c). To maintain a continuous record of the encountered strata, disturbed samples were also collected from drill rods and flushings (Fig. 9.2d). However, it should be noted that the hydraulic feed rotary drilling method resulted in a mixture of disturbed sediment in the circulating fluid, which will introduce inaccuracies in determining the exact depth of lithological change. In this study, these sediments were collected at 1 m depth intervals and used only primarily to provide a general indication of the encountered geology. The undisturbed split spoon samples were examined and recorded on-site before being carefully stored in sealed containers. Detailed descriptions of the lithology and graphical logs were created, considering the physical characteristics such as colour, mineral composition, texture, and structural features of the sediments. Hand specimens were also analysed using a binocular microscope for mineralogy and sedimentological features. In order to determine the different geological-geotechnical parameters for each lithological unit two approaches were employed. Firstly, direct measurements from in-situ boreholes and laboratory-derived parameters and secondly, empirical techniques based on Indian standard codes were applied to indirectly derive the properties of the sediments. During the drilling process measurements of Standard Penetration Test (SPT) and of standing water levels were taken. The standing water levels were recorded in the boreholes after removing the casings, specifically between December 2014 and June 2015, though it is acknowledged these will vary throughout the year, particularly in relation to the Monsoon. The collected water level data was then used to create a groundwater table depth map for the study. The laboratory tests applied to determine the index properties of the sediments included grain size analysis (IS 2386 Part 1 1963) and Atterberg’s Test (IS 2720 Part 5 1985). In heterogeneous soft alluvium deposits, the use of deep foundations is preferred over shallow foundations (IS 2911 2010) to minimise the risk of structural failure caused by differential settlement and movement during ground shaking (Cubrinovski and McCahon 2011). Moreover, bored cast in-situ piles are a practical and efficient technique for densely populated urban areas (Karandikar 2018). The types of soil (cohesive or cohesionless) within the upper 30 m bgl at Varanasi were determined empirically by combining lithological observations with the fine and coarse contents obtained from grain size analysis data and then estimating the capacity of single piles for deep foundations.

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Fig. 9.2  Sample collection procedures at the field: (a) Location of Varanasi geotechnical borehole network; (b) Shell and Auger Drilling Rig; (c) core retrieved from split corer and (d) sediment samples from water flush

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An outline of the methodologies employed to determine the key geotechnical parameters and calculate their values to create the urban development vulnerability map is described below. For further details on investigation procedures readers are referred to the relevant codes. To identify the most suitable or vulnerable zones for urban expansion at Varanasi the geotechnical data for the sediments were then combined in a GIS platform and an Analytical Hierarchical Process (AHP) technique (e.g., Nath 2004; Maiti 2016) was applied to the data. The AHP technique, as described by Saaty (1980), is a decision-making tool based on multiple objectives and criteria, which relies on expert judgment. In this technique, experts assign ratings or weightings to each parameter through pair-wise comparisons. Using this method, thematic maps of the individual parameters are classified into smaller attributes or factors based on their relative importance. All the thematic maps are overlaid to generate a final map.

9.3.1 Standard Penetration Test (SPT) To obtain the field-based SPT value, a split barrel sampler is driven into the sediment using a 63.5 kg hammer dropped freely from a height of 0.76 m (as per IS 2131). The sampler is initially driven to a depth of 15 cm below the bottom of the pre-bored hole. Then, the number of blows required to further drive the sampler by 30 cm into the sediment, known as the N30 count, is recorded. The soil encountered during the first 15 cm of penetration is disturbed, so the SPT value is based on the last 30 cm of penetration (Maiti 2016), which represents the standard penetration resistance of the sediment. However, the penetration resistance is affected by the stress conditions at the test depth and requires correction before it can be utilised for further empirical relationships. To correct the SPT value, several factors including the hammer energy ratio (CE), the overburden pressure (CN), the borehole diameter (CB), the rod length (CR), and the presence or absence of liners in the samplers (CS) are multiplied with it using the following expression provided by Youd et al. (2001):

 N1 60  SPT?CN ?CE ?CB?CR ?CS

where CN = 0.77 × log10 (20/P′), P′ is the effective overburden pressure; CE and CB value is taken as 1; CR is 0.8 for 3 m rod length. A further adjustment is made to the N1 value to eliminate the impact of dilation in sandy soils, which can temporarily increase the effective stress by generating negative pore water pressure, leading to inaccurate SPT values. Therefore, the following considerations should be taken into account for this correction: (1) the presence of a sand or silty sand layer below the water table, and (2) ensuring that the N1 value is greater than 15.

Corrected  N1 60  15   N1 ?15  / 2 

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Table 9.2  Scale of consistency and compactness for cohesive and cohesionless soils respectively in terms of SPT value For clay and sand Consistency N30 blows /0.30 m For sand and gravel Relative density N30 blows /0.30 m

Very soft