Sediment Dynamics, Heavy Mineral Depletion and Morphological Changes of a Placer Mining Beach of Sw Coast of India
Total Page:16
File Type:pdf, Size:1020Kb
SEDIMENT DYNAMICS, HEAVY MINERAL DEPLETION AND MORPHOLOGICAL CHANGES OF A PLACER MINING BEACH OF SW COAST OF INDIA Thesis submitted to the Cochin University of Science and Technology In partial fulfilment of the requirements for the award of the Degree of Doctor of Philosophy in Physical Oceanography Under the Faculty of Marine Sciences by R. PRASAD National Centre for Earth Science Studies Thiruvananthapuram November 2016 Memories of My Beloved Father Sri. M.K. Ravindran Dedicated To My Beloved Family ACKNOWLEDGEMENTS I wish to place on record my deep sense of gratitude to my Research Guide Dr. N.P. Kurian, Former Director, National Centre for Earth Science Studies (NCESS), who has been a source of inspiration and support to me throughout the course of my research work. I owe him a lot for the constant encouragement and guidance and also for sparing his invaluable time, without which this work wouldn't have taken this shape. I express my immense gratitude to Dr. L. Sheela Nair, Scientist-E, Coastal Processes Group, NCESS for the constant guidance and encouragement received for the research work and for the support in the preparation of this thesis. I am grateful to Dr. T.N. Prakash, Director-in-charge & Group Head, Coastal Processes and Dr. V.M. Tiwari, Former Director, NCESS for providing all the necessary facilities of the institute for the successful completion of my research work. Dr. A.N. Balchand, Dean, Faculty of Marine Sciences & Professor, Dept. of Physical Oceanography, School of Marine Sciences, CUSAT has provided me valuable support and guidance in his capacity as Doctoral Committee member. I am thankful to Dr. R. Sajeev, Associate Professor, Dept. of Physical Oceanography, School of Marine Sciences, CUSAT, for the constant encouragement and support during the course of my research work. It is with great pleasure and gratitude that I acknowledge the valuable guidance received from Dr. K.V. Thomas (former Group Head), Dr. T.S. Shahul Hameed, (Scientist-G, Rtd.), Dr. K.K. Ramachandran (Group Head i/c) and Dr. Reji Srinivas (Scientist-C) of Coastal Processes Group during the course of my work. I acknowledge with thanks the useful and inspiring discussions I had with Prof. T.S. Murty, Adjunct Professor, University of Ottawa, Canada and Prof. Kerry Black, former Professor, University of Waikato, New Zealand. I wish to thank Dr. T. Radhakrishna, Dr. G.R. Ravindrakumar, Dr. G. Mohan Kumar, Dr. D. Padmalal, Dr. V. Nandakumar and Dr. D.S. Suresh Babu for their constant encouragement during the course of this research work. I acknowledge with gratitude the help received from M/s. D. Raju, M. Ramesh Kumar, S. Mohanan, and M. Ajith Kumar, Scientific Officers of NCESS at various stages of this study. I acknowledge with thanks the support provided by the Chief Manager and other officers and staff of the Administrative and Accounts sections of NCESS. Special thanks are due to Librarian and other staff of the library for extending the Library facilities. My special thanks to Mrs. Molly Kurian for the moral support extended during the entire period of my work. It is my pleasure to put on record the support and friendliness I have enjoyed from the company of Dr. C. Sreejith, Dr. V.R. Shamji, Dr. Tiju I. Varghese, Mr. E.K. Sarathraj, Mr. K.C. Vimal, Mr. M.K. Sreeraj, Mr. N. Nishanth, Dr. K.O. Badarees, Dr. C.S. Prasanth, Dr. R. Vishnu, Dr. S.S. Praveen, Mr. S. Arjun, Mr. Anish S. Anand, Mr. V. Noujas., Dr. M.M. Rameshan, Mr. M.K. Rafeeque, Mr. P.B. Vibin, Mr. S.S. Salaj, Mr. T.S. Sreekanth and Mr. K. Eldhose during my tenure at NCESS. I wish to thank my friends Dr. C.K. Unnikrishnan, Dr. K. Haris and Mr. K.A. Abhinav for their constant encouragement during the course of my research work. I express my deep gratitude to my mother (N. Radha), my grandmother (M.K. Madhavikutty Amma), my wife (G.S. Soumya), my brother (R. Dileep) and my sister (R. Shailaja) for their prayers and unflinching support for the completion of this work. Prasad R. ii CONTENTS Acknowledgements.................................................................................. i Contents................................................................................................... iii List of tables............................................................................................ ix List of figures........................................................................................... xi Symbols/Notations................................................................................... xvii Abbreviations/Acronyms......................................................................... xxi List of publications from the thesis......................................................... xxiii Chapter 1 INTRODUCTION 1.1 General............................................................................ 1 1.2 Coastal Zone.................................................................... 1 1.2.1 Coast.................................................................... 1 1.2.2 Shore.................................................................... 2 1.2.3 Shoreface............................................................. 2 1.2.4 Continental shelf................................................. 2 1.3 Coastal Processes............................................................ 2 1.3.1 Waves.................................................................. 3 1.3.1.1 Wave transformation............................ 5 1.3.1.2 Radiation stress.................................... 10 1.3.1.3 Wave spectrum..................................... 12 1.3.2 Currents............................................................... 13 1.3.2.1 Wind-induced current........................... 14 1.3.2.2 Wave-induced current.......................... 15 1.3.2.3 Tidal currents........................................ 17 1.3.3 Beach Erosion / Accretion................................... 18 1.3.3.1 Coastal structures contributing to erosion/accretion.................................. 18 1.3.3.2 Other anthropogenic factors contributing to erosion......................... 20 1.4 Sediment Dynamics......................................................... 20 1.4.1 Modes of sediment transport............................... 22 1.4.1.1 Bed load transport................................ 22 1.4.1.2 Suspended load transport..................... 23 1.4.1.3 Sheet flow............................................. 24 1.4.2 Longshore sediment transport............................. 24 1.4.3 Cross-shore sediment transport........................... 26 1.5 Sediment Budget............................................................. 27 1.6 Beach States.................................................................... 28 1.6.1 Equilibrium beach profile.................................... 29 1.6.2 Beach classification............................................. 30 1.6.2.1 Reflective beach................................... 31 1.6.2.2 Intermediate beach............................... 31 1.6.2.3 Dissipative beach.................................. 32 1.7 Beach Placers.................................................................. 32 1.7.1 Formation of placers............................................ 33 1.7.2 Sorting processes................................................. 33 1.7.2.1 Settling equivalence............................. 33 1.7.2.2 Selective entrainment........................... 34 1.7.2.3 Transport sorting.................................. 34 1.7.2.4 Shear sorting......................................... 34 1.8 Background of the Study................................................. 35 1.9 Aim and Objectives......................................................... 37 1.10 Study Area....................................................................... 37 1.11 Structure of the Thesis..................................................... 40 Chapter 2 REVIEW OF LITERATURE 2.1 Introduction..................................................................... 43 2.2 Coastal Hydrodynamics.................................................. 43 2.2.1 Global scenario.................................................... 43 2.2.2 Indian scenario.................................................... 46 2.3 Nearshore Sediment Transport........................................ 54 2.3.1 Global scenario.................................................... 54 2.3.2 Indian scenario.................................................... 62 2.4 Beach Placers.................................................................. 68 2.4.1 Global scenario.................................................... 68 2.4.2 Indian scenario.................................................... 70 2.5 Beach - Innershelf Morphological Changes.................... 74 2.5.1 Global scenario.................................................... 74 2.5.2 Indian scenario.................................................... 83 2.6 Salient Conclusions from the Literature Survey Relevant to the SW Indian Coast.................................... 90 Chapter 3 DATA AND METHODOLOGY 3.1 Introduction..................................................................... 93 3.2 Instruments Used............................................................. 93 3.2.1 Wave rider buoy.................................................. 93 3.2.2 Automatic weather station................................... 97 3.2.3 Echo-sounder....................................................... 98 3.2.4 Global positioning system..................................