Study of the Environmental Seomorpholosy in the Balason Basin, Darjeelin6
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STUDY OF THE ENVIRONMENTAL SEOMORPHOLOSY IN THE BALASON BASIN, DARJEELIN6 A Ph. D. Thesis Submitted lay Indira Lepcha (nee) Lama, Department of Geography and Applied Geography University of North Bengal District: Darjeeling West Bengal, India 734430 2003 1680_53 1 6 Alio PREFACE Understanding the natural environment and its relationship with the ecological processes is an essential pre-requisite for undertaking any developmental planning. The escalating anthropogenic activities, coupled wth poor management of land and water resources are placing tremendous stress on the environment, resulting in the steady increase of soil erosion, floods and drought, escalating urisan congestion and disturbing the ecological balance of the environment. Remedies to these maladies lie in the study of the causes of these aspects and providing the prescription for sustainable development. Consequently, the Balason fluvial environment, as part of the physical environment demanding considerable attention vis-a-vis development and planning, has been selected for detailed study. The fluvial environment, as a synthesis of geological, pedological, hydrological and geomorphological conditions and processes, includes a wide spectrum of aspects pertaining to these fields. Incorporating these aspects in the proper perspective will contribute greatly towards a better understanding of the fluvio-environmental adjustments and ecological balance in the study area. This present study therefore correlates the various aspects of the fluvial environment with the existing geo-enviranmental scenarios of the basin for evolving a suitable strategy for environmental planning and resource management. 0i/Uii and Icmamoat, 3 vlotu^ uJkc to- extend in au aince/iittt, Vhe. de^eoeat Aenoie. cl tvtaXiluide. to !ui. Qiuhivt, e>a«lcat, \mA^ x)vLe*Acvi. 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L-oulUnfto, lo/ime/i OxlncipaX., Jtoteto y^Mleae, Jja^eeunch La/i he/i camaaa&ionaJLe. enuuiinu an^ totr coruUcuvuiL ntoti/iatina me- ta comaiete- mu ttotJL yiu* hea/ittelt atatilUiBe ta zJiUaa. xJoandana iJvat, (Suuualant Q>£oietcw^ Ulanle/tA CUiAociation, ZfcuieeUna, uu. net. UvialuaJole help ani co-^taetaiionr 3utina mu iota caUeclian. (I.F.S.), Ian tuA help, auidanoe, ani duppott. Di. UJnutia naa. hai an. impanXant imSUience. in. Vne. camptetian a£ ttuA tneaia~ J am. oiAo atiitelM ta zJiLv,. &a/uimani. <Jv<u, *nu. oiuJuneJiAnHa'Ay ton. ma- ^Sioe counaei- ana loa. cutoiotiaa. tne, in. me an^/uuxua, uciatiipa^ encompaaaina Vne, le^uJCn, and meo^tn. oj, ntu. aXuau. oiea. Special VnanJka. axe due ta ZMMI.. ^Jvanta. OzaMian, z)iLi. XJOan Onamuuv (CompiiAet) a*i3 i/JLt. XJOA (Xjaa. e>'tii^MV, UM. taJKlna time out lUom tneit ouau acnedtaea. ta help deaian tfie co/iex and txe/uuc t*ie niapa~ .UxuU^ out not t*ie teaat., ta cut mu Vuenida. and •fMt-'fiAMiieaA, vmooA namea. mau not oe ptinted he/ie. — nut cue OMxetu ca/cded in mu heait liiith azatitud^. C} viauld liXcc ta thank, them att UM. helpina me. fUtcSti ntu. ^fi^KLon ta a. atoA, and t£ctXize that tne MM in. Ine limit ! ^v><. QQsedS^^^ne. 8003 ^tu&nz, ^>eAa, Gm) Q^^M. Ill CONTENTS Page Number INTRODUCTION 1-6 A. Problems 1 B. The Study Area 2 C. Methodology 3 CHAPTER 1: PHYSICAL BACKGROUND OF THE STUDY AREA 7-26 1.1 Geology 7-11 1.2 Topography 11-13 1.3 Climate 13-15 1.4 Soil 15-20 1.5 Natural Vegetation 20-23 1.6 Landuse 24 1.7 Conclusion 24-25 Reference 25-26 CHAPTER 2 : GEOMORPHOLOGY OF THE BASIN 27-42 2.1 Introduction 27 2.2 Slope 27-28 2.3 Relative Relief 29-30 2.4 Dissection Index 30-31 2.5 Drainage Density 31-33 2.6 The Ms^ Geomorphic Units 33-35 2.7 Major Geomorphic Forms 35-38 2.8 Case Study of Bungkulung Debris Fan 38-41 2.9 Conclusion 41-42 Reference 42 CHAPTER 3 : MORPHOMETRIC ANALYSIS OF THE BALASON BASIN 43-58 43 3.1 Introduction 43-56 3.2 Motprmmetnc Analysis of the sub-basins 56-57 3.3 Conclusion 58 Reference CHAPTER 4 : PEDOGEOMORPHIC RELATIONS WITHIN THE BASIN 59-71 4.1 Introduction 59-60 IV 4.2 Pair wise Relations 60-64 4.3 Multiple Relations 64-65 4.4 Pedogeomorphic Relations in different environmerrtai setup 65-69 4.5 Conclusion 69-71 Reference 71 CHAPTER 5 : SOIL EROSION: ASSESSMENT AND STRATEGIES FOR 72-68 CONSERVATION 5.1 Inbxxiuction 72 5.2 ^sessment of Soil Erosion Hazard 72-83 5.3 Strategies for Soil Erosion Corrtrol 83-86 5.4 Conclusion 86-87 Reference 87-88 CHAPTER 6 : LANDSLIDES: PROBLEM AND STRATEGIES FOR ITS CONTROL 89-109 6.1 Introduction 89-90 6.2 The Occurrences of Landslides 90-91 6.3 Nature and Processes 92-93 6.4 Major types of Slope Failure 93-95 6.5 Identification of Landslide Prone Areas 95-98 6.6 Case study of Pankhabari Landslide 98-101 6.7 Case study: Ambootia Landslide 101 -106 6.8 Preventive Measures for stabilization of Landslides and Landslide prone areas 106-107 6.8 Conclusion 107-108 Reference 108-109 CHAPTER 7 : FORMS AND PROCESSES OF THE RIVER BALASON 110-132 7.1 Introduction 110-111 7.2 Study of the Cross-Section 111-113 7.3 Progressive Changes of Hydrological Parameters 113-126 7.4 Study of Bed load and Bed materials 126-128 7.5 Analysis of Braid plain Formation in the River Balason 128-130 7.6 Conclusion 130-131 Reference 131-132 CHAPTER 8 : WATER RESOURCE OF THE BALASON BASIN 133-144 8.1 Introduction 133-134 8.2 Study (^ Rainfall - Runoff 134-138 8.3 Study of Evaporation 138-139 8.4 Estimation of Runoff of the Basin 139-142 8.5 Estimation of Surface Water Resource of the Baiason basin 142-143 8.6 Conclusion 143-144 Reference 144 CHAPTER 9 : ENVIRONMENT IMPACT ASSESSMENT 145-158 9.1 Introduction 145-146 9.2 Impact Identification 146-151 9.3 Case Studies 151-156 9.4 Conclusion 156-157 Reference 157-158 Abstract 159-164 Bibliography 165-173 Appendix 174-186 VI LIST OF FIGURES Page Number Figure 0.1 Location of the study area 2-3 Figure 1.1 Geological setup of the Balason basin 7-8 Figure 1.2 Contour map of the Balason basin 11-12 Figure 1.3 RepreserTtative rainfall and t«Ttperature of thr^ broad regions of 14-15 the Balason basin Figure 1.4 Soil map of the Balason basin 17-18 Figure 1.5 Landuse map of the Balason basin 24-25 Figure 2.1 Slope Morphology of the Balason basin 27-28 Figure 2.2 Relative relief of the Balason basin 29-30 Figure 2.3 Dissection index of the Balason basin 30-31 Figure 2.4 Drainage density of the Balason basin 31 -32 Figure 2.5 Geomorphic units of the Balason basin 33-34 Figure 2.6 Geomorphological map of the Balason basin 35-36 Figure 2.7 Contour plan of the Bungkulur^ debris fan 39-40 Figure 2.8 Geomorphological Map of the Bungkulung debris fan 39-40 Figure 2.9 Cross-section across the Bungkulung debris fan 40-41 Figure 3.1 Index map for the third order basins 43-44 Figure 3.2 Frequency distribution curves for various basin morphomorphetric 47-48 properties of the third order Figure 3.3 Third order basins of the Balason basin plotted on arithmetic 48-49 probability paper Figure 3.4 Regional dispersion of morphometric variables of third ord^ 48-50 basins Figure 3.5 Linear regression analysis of some morphometric variables of the 53-54 55 third order basins Figure 3.6 Groups of highly inter correlated variables found by resorting the 54-55 data of table 3.5 Figure 4.1 Index map for sample sites for pedogeomorphic studies 59-60 Figure 4.2 Linear relationships among the various pedogeomorphic 61-62 parameters in the Balason basin Figure 4.3 Groups of highly inter-correlated variables found by resorting the 63 data of table 4.2 Figures.! Factors in soil erosion by water 73 Figure 5.2 Soil Erodibility Nomograph 74-75 Figure 5.3 Rain erosivity zone of the Balason basin 76-77 Figure 5.4 Soil erodibility zones of the Balason basin 78-79 Figure 5.5.