The Brahmaputra River in Assam: Geomorphology, Hazards, and Natural Resources

Description

This holistic book covers the richest area in North East India in terms of both explored and foreseen reserves of fossil fuels and other natural resources. Using a multidisciplinary approach, GIS, and geospatial data gathered from different case studies included, this book helps readers develop a thorough understanding of a highly dynamic big river, the Brahmaputra, and use it as a comprehensive resource for further understanding the science of rivers. It discusses the causal factors of decadal-scale fluvial dynamics, the nature of fluvial dynamics, lateral variability of the older flood plains and neotectonics in the shallow subsurface, and the overall trend of basin evolution at different depths. Cover Half Title Title Page Copyright Page Dedication Table of Contents List of Figures List of Tables Preface Acknowledgements Author 1. Introduction The Upper Reach of the Brahmaputra Valley Precipitation and Hydrology Natural Hazards Essential Objectives 2. A Quick Review: Geoscientific Understanding of the Brahmaputra Valley General Geology and Geomorphology Stratigraphy Archaean Precambrian Mesozoic Tertiary Paleogene Strata Neogene Strata Quaternary Deposits Structural and Tectonic Setting Seismicity Tectonic Setting of the Brahmaputra Valley Limitations of 'Geosynclinal Theory' Implications of 'Pop-Up' Theory Different Collision Models and Their Influence on the Basin Evolution Neotectonic Elements Geomorphic Evidence Structural Evidence Fluvial Dynamics and Morphotectonics 3. Tools and Methods: A Brief Appraisal Common Geological Problems Questions of Usual Concern in Geophysical Exploration Inverse Nature of Geophysical Problems Effect of Size and Depth of the Causative Body Planning Geophysical Investigations 'Noise' and the Problems of Enhancing 'Signal' Resolution Data Reduction Data Presentation Geological Objects and Their Geophysical Generalizations Geophysical Data Integration Gravity Data Bouguer Anomaly Regional–Residual Separation Seismic data analysis and basic principles of interpretation The 'Seismic Data' Noise Reduction 2D Seismic Data Interpretation Shallow Subsurface Geophysical Field Data Samples Uphole Data Shallow Refraction Data Remote Sensing and GIS Data Used Data Integration 4. Fluvial Dynamics and the Changing Interfluves Data and Approach Dynamics of the Main Brahmaputra River Bank-Line Shift Basin Asymmetry and Bank-Line Shift Planar and Temporal Variability of Width Trend Analysis of the Bank-Line Shift and Width Variation Channel Avulsion and Migration Morphodynamics of the Brahmaputra River Major Changes in River Islands Majuli Island Geomorphology, History, and Mechanism of Erosion of Majuli Island Thalweg Migration Subansiri Effect Effect of Erosion of Majuli Island on BB Formation Erosion of Majuli Island and the Aggradation Tendency Existing Hypothesis for the Genesis of Majuli Island and Related Questions Dibru-Saikhowa Island – the New Majuli Bank erosion in Rohmoria Dynamics of the Brahmaputra Tributaries South Bank Tributaries North Bank Tributaries Morphotectonic Zonation of the Upper Reach of the Brahmaputra Valley Recent Seismicity and Fluvial Dynamics Morphotectonic Model for Morphodynamics 5. Quaternary Geomorphology, Shallow Subsurface Stratigraphy, and Neotectonics Theoretical Aspects A 'Layer' Velocity as an Attribute for Basin Analysis Micro-Zonation of the Basin Significance of Tectonogeomorphic-Type Areas Type 1 Areas [V[sub(3 (High))] V[sub(2 (High))] V[sub(1 (High))]] Type 2 Areas [V[sub(3 (High))] V[sub(2 (High))] V[sub(1 (Low))]] Type 3 Areas [V[sub(3 (High))] V[sub(2 (Low))] V[sub(1 (High))]] Type 4 Areas [V[sub(3 (High))] V[sub(2 (Low))] V[sub(1 (Low))]] Type 5 Areas [V[sub(3 (Low))] V[sub(2 (High))] V[sub(1 (High))]] Type 6 Areas [V[sub(3 (Low))] V[sub(2 (High))] V[sub(1 (Low))]] Type 7 Areas [V[sub(3 (Low))] V[sub(2 (Low))] V[sub(1 (High))]] Type 8 Areas [V[sub(3 (Low))] V[sub(2 (Low))] V[sub(1 (Low))]] Multi-Parametric Attributes for Basin Analysis Choosing 'Threshold' Values Study 'Windows' Window 1: Amguri The Amguri Data Fluvial dynamics in Amguri Window Oldest Channel Belt in Layer 3 Older Channel Belt in Layer 2 Old Channel Belt in Layer 1 Tectonic Controls and the River Dynamics Neotectonics and Oil Migration Multi-Parametric Micro-Zonation Window 2: Namrup–Sapekhati Namrup–Sapekhati data Landform Variability and Quaternary Geomorphology Fluvial Dynamics and Quaternary Basin Evolution Neotectonics and Valley–Range Relationship Multi-Parametric Micro-Zonation and the Oil Fields Window 3: Matikhana Matikhana Data Salient Features in Window 3 Window 4: Mechaki Window 4 Mechaki Data Salient Features in Window 4 Discussion 6. Basin Evolution and Fluvial Dynamics Seismic Sections Profile A-A' Profile B-B' Profile C-C' Profile D-D' Profile E-E' Profile F-F' Discussion Generalized Lithostratigraphy and Basin Evolution Basin-Forming Tectonics Sequence 1: Margin Sag (MS-321) Sequence 2: Margin Sag–Interior Sag (MSIS-321) Sequence 3: Interior Sag (IS-31) Sequence 4: Shear or Wrench Initiation (LL1) Sequence 5: Wrench Deformation (LL3) Sequence 6: Basin Upliftment (LL3) Basin-Modifying Tectonics Tectonics and Sedimentation Unconformity in the Fluvial Sediments Basin Evolution and Directional Shift in the Major Fluvial System Accommodation Space Generation and Residence Time of Rivers Morphotectonic Evolution of Majuli Island 7. Bed–Bank Relationship and Flood Vulnerability Bed–Bank Relationship Assumptions for Flood Characterization Data and Interpretation Flood Characterization 8. The Golden Corridor Surface Resources Gold on the Surface Hydropower Alternative Energy Resources like Using Solar Power and Wind Power Shallow Subsurface Resources Gold in the Shallow Subsurface Coal in the Shallow Subsurface Coal Bed Methane (CBM) Deep Subsurface Resources Gold in the Deep Subsurface Deeper Oil Prospects 9. Epilogue Morphodynamics of the Brahmaputra River and Tributaries Erosional and Evolutionary History of Majuli Island Multi-Parametric Micro-Zonation in the Shallow Subsurface: Implications for Palaeo-Fluvial Dynamics Cyclic Evolution of the Poly-History Basin Characterization of Changing Bed–Bank Relations Natural Resources of Geological Significance Major Conclusions Scope for Further Work Appendix 1: Field Visit Appendix 2: Tables (Additional for Chapter 4) Glossary References Index