geology and structural studies of tanakpur-champawat area in
TRANSCRIPT
Geology and Structural studies of
Tanakpur-Champawat area in Kumaun
Himalaya with Special reference to hill
Slope Instability
Thesis
Submitted to the
University of Lucknow
For the Degree of
Doctor of Philosophy In
GEOLOGY
By Chandra Prakash
M. Sc.
Centre of Advanced Study in Geology
University of Lucknow, Lucknow-226007, India
September, 2014
This work is
Dedicated to
My Parents
Contents Page
No.
Acknowledgements i
List of Figures iii
List of Tables
viii
CHAPTER 1 INTRODUCTION
1.1 Location and approach of the study area
1.2 Physiography
1.3 Climate and Rainfall
1.4 Previous work
1.5 Geology of the area
1.6 Field work, Mapping and Sampling
1.7 Laboratory work and Methodology
1.8 The objectives of the present work
1.9 Presentation of the work
1-18
2
4
6
6
9
14
16
17
17
CHAPTER 2 STRUCTURES
2.1 Megascopic structures
2.1.1 Thrusts
2.1.2 Folds
2.2 Mesoscopic Structures
2.2.1 Minor folds
2.2.2 Planar structures
2.2.3 Linear structures
2.3 Shear zones
2.4 Thrust-related structures
19-38
19
20
20
21
23
26
31
35
36
CHAPTER 3 PETROGRAPHY & MICROSTRUCTURES
3.1 Petrography
3.1.1 Siwaliks
3.1.2 Bhimtal Formation
3.1.3 Almora Crystallines
3.2 Microstructures
39-56
39
40
42
44
50
CHAPTER 4 STRAIN ANALYSIS
4.1A Grain Shape analysis of Quartz (Panozzo Plots)
4.1B Deformed Porphyroclasts
57-72
58
59
(a) Fry method
(b) Rf / Ф method
62
66
CHAPTER 5 MORPHOMETRIC ANALYSIS & NEOTECTONICS
5.1 Morphometric Analysis
5.1.1 Linear Parameters
5.1.2 Areal Parameters
5.1.3 Shape Parameters
5.2 Neotectonics
5.2.1 Neotectonic Features
5.3 Lineament Analysis of the study area
5.4 Digital elevation model (DEM) and contour map of
the study area
5.5 Slope and Slope aspect map of the study area
73-105
73
75
83
89
92
93
96
99
100
CHAPTER 6 HILL SLOPE INSTABILITY
6.1 Landslides in the study area
6.2 Landslides vis a vis structural control
6.2.1 Landslide near Shiala village, Sukhidhang
6.2.2 Batna Gad landslide
6.2.3 Chaundakot Landslide
6.3 Landslides along Tanakpur-Champawat highway
6.4 Landslide hazard zonation model
106-124
107
109
110
111
111
112
117
CHAPTER 7 DISCUSSION & CONCLUSIONS 125-132
REFERENCES 133-146
i
Acknowledgements
Ph.D. is like a journey which starts from one station and to end at another station.
This journey never ends without the support and encouragement of many persons,
which include teachers, seniors, friends and various institutions. I would like to
express my sincere thanks to those peoples who have been very helpful to me during
thesis writing.
First of all I want to thank my supervisor Prof. K. K. Agarwal, Head, CAS in
Geology, Lucknow University, Lucknow for his supervision and guidance for
accomplishing the research work. His understanding, patience and untiring
supervision have helped me to complete my thesis work in all respects.
I am highly thankful to Prof. I. B. Singh, Prof. Surendra Kumar, Prof. M. P.
Singh, Prof. A. K. Jauhri, Prof. N. L. Chhabra, Prof. D. D Awasthi, Prof. V. Rai, Prof.
Ajai Mishra, Prof. D. S. Singh, Prof. Munendra Singh, Dr. Sensarma and Dr. Ajay
Arya of our department for their constant moral support and motivation to complete
my Ph.D.
I express my sincere thanks to Prof. A. R. Bhattacharya for critically reading
few chapters of the thesis and making fruitful suggestions & improvements.
I appreciate the help of Prof. R. Bali, Dr. P. Srivastava of our department and
Dr. Desh Deepak from Chemistry Department for their support and generous care to
shape my thesis.
Fruitful discussions, advice and motivation received from Prof. H. B.
Srivastava, Banaras Hindu University, Varanasi, Prof. D. C. Srivastava, IIT,
Roorkee, Dr. Sovanlal Chattoraj, IIRS, Dehradun, Dr. V. K. Sharma and Dr. Atul
Kohli, Geological Survey of India, during the course of this work is thankfully
acknowledged.
I am also thankful to my seniors Dr. Yogendra Bhadauriya, Dr. Biswajeet
Thakur, Dr. Pranay Vikram Singh, Dr. Santosh Kumar Pandey, Dr. S. Nawaz Ali, Dr.
Pankaj Sharma, Dr. Amit Awasthi, Dr. Vikram Bhardwaj, Mr. Ravi Negi, Mr.
Saurabh Rastogi, and Mr. Kalyan Krishna for their intellectual input, unconditional
support and cooperation in all respects during my research work.
ii
I would like to express my special thanks to my friends Mr. Dhirendra Kumar,
Mr. Subodh Verma, Mr. Pawan Kumar Yadav, Mr. Vinay Singh, Mrs. Shalini Maurya,
Mr. Manish Kumar Gupta, Mr. Neelendra Kumar, Dr. Shamim Ahmad, Mr. Saurabh
Verma, Mr. Dharmendra Kumar Jigyasu, Late Dr. Rohit Kuvar, Mr. Shailendra
Kumar Prajapati, Mr. Amit Kumar Verma, Mr. Ankur Dwivedi for their valuable and
fruitful suggestions and help in successfully completing my research.
Special thanks are due to Ms. Nigar Jahan (GSI) and Mr. Amar Agarwal (now
at Karlsruhe University, Germany) for accompanying me in the field on many
occasions and also extending all possible help during the course of this work.
I am thankful to Mr. Parijat Mishra, Mr. Gaurav Joshi, Mr. Deepak Kumar
Rai, Mr. Awadesh kumar Yadav, Mr. Shakti Kumar Yadav, Mr. Hemant Verma, Mr.
Vineet Kumar, Mr. Ankit Gupta, Mr. Chetan Anand Dubey for their support and
cooperation.
I wish to thank all the members of my family for their moral support, patience,
encouragement and general understanding throughout my research work.
Thanks are also due to the non-teaching staff of our department for providing
help whenever is required.
I gratefully acknowledged the Council of Scientific & Industrial Research
(CSIR), Government of India for providing financial support in the form of Junior
Research Fellowship and Senior Research Fellowship,(09/107(0335)/2009-EMR-I)
without which this work would not have been possible.
Chandra Prakash
iii
List of Figures Page
No.
Fig. 1.1: Location map of the study area showing its position in (A) India
and in (B) Himalaya.
3
Fig. 1.2: Field photographs showing generalised view of rugged
topography in the study area, (A) near Sukhidhang, (B) near
Chalthi, (C) near Swala, (D) Ladhiya River in the study area.
5
Fig. 1.3: Geological map of the study area, Kumaun Lesser Himalaya,
modified after Valdiya 1962, 1980.
10
Fig. 1.4: Field photographs (A-F) showing coal beds within sandstone
along Rela ka khola to Hathi khor section.
12
Fig. 1.5: Field photographs showing (A) quartzite rock, Loc. 8 km south
of Chalthi, (B) chlorite schist, Loc. 4 km south of Chalthi.
13
Fig. 1.6: Field photographs showing (A) quartzite rock just after Chalthi
bridge, (B) mylonite, Loc. 2.5 km north of Chalthi bridge.
14
Fig. 1.7: Sample location map of the Tanakpur-Champawat area,
Kumaun Lesser Himalaya, Uttarakhand.
15
Fig. 2.1: Field photographs showing (A) Main Boundary Thrust, Loc.
1.5 km north of Sukhidhang, (B) South Almora Thrust as
exposed along the Ladhiya river valley.
20
Fig. 2.2: Generalised geological cross-section showing the structure of
the Tanakpur- Champawat area, Kumaun Lesser Himalaya.
21
Fig. 2.3: Structural map of the Tanakpur-Champawat area showing the
attitudes of the planar and linear structures.
22
Fig. 2.4: Field photographs showing (A) F1 fold 2 km north of Dhaun
along Dhaun-Diuri road section, (B) sheath fold, Loc. 8 km
south of Swala, (C) chevron fold, Loc. 3 km south of Swala,
(D) recumbent fold near Dhaun.
24
Fig. 2.5: Field photographs (A & B) showing conjugate folds, Loc. 3.8
km north of Bastia and 3 km south of Amori.
25
Fig. 2.6: Field photographs (A & B) showing plunging folds, Loc. 3 km
south of Sukhidhang and near Dhaun.
25
iv
Fig. 2.7: Stereoplot of S0 planes of the study area. 26
Fig. 2.8: Field photographs (A-F) showing primary bedding planes at
different locations in the study area.
27
Fig. 2.9: Field photographs (A-F) showing foliation planes at different
locations in the study area.
28
Fig. 2.10: Stereoplot of S1 plane of the study area. 29
Fig. 2.11: Field photographs (A-F) showing joints at different locations in
the study area.
30
Fig. 2.12: Rose plot showing trend of joints (S2) in the study area. 31
Fig. 2.13: Samples with mineral lineations (A-C) and stretching lineations
(D-F) collected at different locations in the study area.
33
Fig. 2.14: Field photographs (A & B) showing slickensides, Loc. 4 km
south of Amori and near Chalthi.
34
Fig. 2.15: Field Photographs (A & B) showing boudins, Loc. 7 km north
of Diuri.
34
Fig. 2.16: Field photographs showing (A-C) small scale shear zone in
Siwalik rocks near Bastia showing sense of shear 156o,101
o and
320o, (D) sheared sandstone 6 km south of Sukhidhang showing
sense of shear 105o, (E-F) quartz veins in small shear zone
showing sense of shear 115o and 110
o , Loc. 1.8 km north of
Chalthi.
36
Fig. 2.17: Field photographs showing ramp and flat structure, Loc. 3.2 km
north of Bastia.
37
Fig. 2.18: Field photographs (A & B) showing duplex structure in the
study area near Bastia.
38
Fig. 3.1: Photomicrographs (between X polars) showing (A & B) sub-
angular to sub-rounded quartz grains, (C & D) feldspar with
lamellar twining, (E & F) elongated laths of micaceous
minerals.
42
Fig. 3.2: Photomicrographs (between X polars) (A & B) showing fine to
medium sub-grains of quartz and effects of thrusting.
43
Fig. 3.3: Photomicrograph (between X polar) showing chlorite schist
together with biotite which marks the preferred orientation.
43
v
Fig. 3.4: Photomicrographs (between X polars) (A & B) showing fine
grained quartz.
44
Fig. 3.5: Photomicrographs (between X polars) (A & B) showing
recrystallization of quartz grains.
45
Fig. 3.6: Photomicrographs (between X polars) (A & B) showing fine
grain minerals of quartz and mica with alternate banding.
45
Fig. 3.7: Photomicrographs (between X polars) showing (A) schistosity
plane of biotite mineral, (B) stretched garnet porphyroblast and
elongated biotite.
46
Fig. 3.8: Photomicrographs (between X polars) (A & B) showing
protomylonite with mylonitic foliation accentuated by mica.
47
Fig. 3.9: Photomicrographs (between X polars) (A & B) showing
mylonite with porphyroclast of quartz grains and a well
developed mylonitic foliation.
48
Fig. 3.10: Photomicrographs (between X polars) (A & B) showing
ultramylonite with a fine grained matrix (> 90%).
48
Fig. 3.11: Photomicrographs (between X polars) showing (A) shear bands,
(B) recrystallised quartz ribbons.
49
Fig. 3.12: Photomicrographs (between X polars) showing (A) prominent
foliation plane, defined by alternate bands of quartz and biotite,
(B) porphyroclast of plagioclase within fine grained
groundmass of quartz and biotite.
50
Fig. 3.13: Photomicrograph (between X polar) showing θ-type mantled
porphyroclast.
51
Fig. 3.14: Photomicrographs (between X polars) (A & B) showing Ф -
type mantled porphyroclasts showing symmetrical trail.
52
Fig. 3.15: Photomicrographs (between X polars) showing (A) σ-type
mantled porphyroclast gives top to south sense-of-shear, (B) δ-
type mantled porphyroclasts showing sense-of-shear top to
south.
53
Fig. 3.16: Photomicrographs (between X polars) (A & B) showing mica
fish of biotite and muscovite near Swala.
53
vi
Fig. 3.17: Photomicrographs (between X polars) showing (A) micro fold
within quartz vein, (B) S-C structure shows top to south sense-
of-shear.
55
Fig. 3.18: Photomicrographs (between X polars) showing (A) ‘V’-pull-
apart microstructure in mylonite rock, (B) book-shelf structure
is noticed in the gneisses.
56
Fig. 3.19: Photomicrographs (between X polars) (A & B) showing quartz
ribbons in mylonite rocks.
56
Fig. 4.1: Panozzo’s plot of grain-shape analysis of quartz, south to north
along Tanakpur-Champawat highway.
60
Fig. 4.2: Fry plots of the rocks of the study area along Tanakpur-
Champawat highway.
63
Fig. 4.3: Rf / Ф diagram and the chi2 graphs of the rocks of the
Tanakpur-Champawat area.
69
Fig. 5.1: Map showing divisions of sub-basins in Ladhiya & Lohawati
river basins, Uttarakhand.
75
Fig. 5.2: Photographs showing occurrence of landslide in the study area,
(A) near Shyamlatal, (B) near Shiala, (C) near Rela ka Khola,
(D) near Chaundakot, (E) on way to Purnagiri near batna gad,
(F) on way to Purnagiri (near bridge).
94
Fig. 5.3: Field photographs (A-D) showing asymmetric river terraces in
the Ladhiya River Valley.
95
Fig. 5.4: Field photographs (A & B) showing triangular facets at the left
bank of Ladhiya River Valley.
96
Fig. 5.5: Lineament pattern map of the Tanakpur-Champawat and
adjoining areas, Kumaun Lesser Himalaya.
97
Fig. 5.6: Rose diagram of the lineaments of the study area (n=155). 98
Fig. 5.7: Digital elevation model (DEM) of Tanakpur-Champawat and
adjoining areas, Kumaun Lesser Himalaya.
102
Fig. 5.8: Contour map of the Tanakpur-Champawat and adjoining areas,
Kumaun Lesser Himalaya.
103
vii
Fig. 5.9: Slope analysis map of the Tanakpur-Champawat and adjoining
areas, Kumaun Lesser Himalaya.
104
Fig. 5.10: Slope aspect map of the Tanakpur-Champawat and adjoining
areas, Kumaun Lesser Himalaya.
105
Fig. 6.1: Landslide scatter map of the study area. 108
Fig. 6.2: Graph showing year-wise changes in periphery of landslide. 109
Fig. 6.3: Field Photographs showing (A) landslide crown, near Shiala
village (shyamlatal gramsabha), (B) cracks developed along the
water tank at the Shiala village.
110
Fig. 6.4: Field Photographs showing (A) batna gad landslide near the
highway of Purnagiri (Puniagiri) temple, (B) a huge amount of
rock material is derived from the batna gad landslide which
blocked the highway on the way to Purnagiri (Puniagiri)
temple.
111
Fig. 6.5: Field Photographs showing (A) landslide near chaundakot
village, (B) cracks developed on the wall of the house due to
landslide near chaundakot village.
112
Fig. 6.6: Field Photographs (A-D) showing landslide along Tanakpur-
Champawat highway.
112
Fig. 6.7: Map showing grid wise (2.5 km X 2.5 km) distribution of
landslides.
118
Fig. 6.8: Map showing zone wise (5 km X 5 km) distribution of
landslides.
123
viii
List of Tables
Page No.
Table 1.1: Coordinates of the main localities in the study area (from
South to North).
4
Table 5.1: Linear parameters of the Ladhiya river basin, Kumaun
Lesser Himalaya, Uttarakhand.
77-80
Table 5.2: Linear parameters of the Lohawati river basin, Kumaun
Lesser Himalaya, Uttarakhand.
81
Table 5.3: Areal parameters of the Ladhiya river basin, Kumaun
Lesser Himalaya, Uttarakhand.
84-85
Table 5.4: Areal parameters of the Lohawati river basin, Kumaun
Lesser Himalaya, Uttarakhand.
86
Table 5.5: Areal parameters of the Ladhiya river basin, Kumaun
Lesser Himalaya, Uttarakhand.
90-91
Table 5.6: Areal parameters of the Lohawati river basin, Kumaun
Lesser Himalaya, Uttarakhand.
91-92
Table 6.1: Landslide along Tanakpur-Champawat National highway:
Kumaun Lesser Himalaya, Uttarakhand.
114-116
Table 6.2: Grid wise landslide affected areas in percentage. 118-122
Table 6.3: Zone wise landslide affected areas in percentage. 123-124
1
Chapter 1
INTRODUCTION
The Himalaya constitutes the youngest and loftiest mountain chain in the world,
formed due to continental-continental collision of the Indian and Eurasian plates at
around 54-50 Ma (Dewey and Bird, 1970; Dewey and Burke, 1973; Patriat and
Achache, 1984; Searle et al., 1988; Molnar, 1988; Dewey et al., 1989; Le Pichon et
al., 1992; Brookfield, 1998; Rowley, 1998; Hallet and Molnar, 2001; Clark et al.,
2004). The Kumaun Himalaya lying between the River Kali in the east and Sutlej in
the west include around 320 km stretch of mountainous terrain. It represents all the
lithotectonic groups from south to north, which are: Outer Himalaya, Lesser
Himalaya, Greater Himalaya and the Tethys Himalaya. The Outer Himalaya includes
Siwalik Group of Sedimentary rocks of Mio-Pliocene age, characterized by steep
hillslopes and deep valleys with crumbling walls scarred with landslides. The Outer
Himalaya is bounded by Himalayan Frontal Fault (HFF) in the South and Main
Boundary Fault (MBF) in the North. The Lesser Himalaya includes Precambrian-
Early Palaeozoic sedimentary belt over which a few outcrop of crystalline-
metamorphic rocks of varying dimension occured as thrust sheets. The Lesser
Himalaya is bounded by Main Boundary Fault (MBF) in the South and Main Central
Thrust (MCT) in the North. The Greater Himalaya is composed of metamorphic
crystalline rocks of ancient age (Archean-Precambrian) and is bounded by Main
Central Thrust (MCT) in the South and the Dar-Martoli fault in the North. The Tethys
Himalaya exposes fossiliferous sedimentary strata of Cambrian-Lower Eocene age
and is bounded in the north by Indus-Tsangpo Suture Zone (ITSZ).
2
The present work deals with the study of Outer and Lesser Himalaya as
exposed around Tanakpur-Champawat area of Uttarakhand, and comes under the
Survey of India (SOI) toposheets no. 62C/3, 4, 7 and 8.
This study focuses mainly on the geological mapping, structural mapping,
strain estimation, morphometric analysis, neotectonics and landslides activity in the
area.
1.1 Location and approach of the study area
The study area is bounded between the latitude 29o 03’ 56’’ N and 29
o 20’ 00”
N and longitude 80o 00’ 00” E and 80
o 20’ 00” E and comes under the Survey of India
(SOI) toposheets no. 62C/3, 4, 7 and 8. (Fig.1.1). The Tanakpur-Champawat area falls
in the eastern part of the Kumaun Himalaya of Uttarakhand and covering
approximately 717 km2. The Ladhiya River is the major drainage system within the
area. The route from south to north traverses across Bhabhar Formation, Siwalik
Group of rocks, Bhimtal Quartzites and Almora Crystallines. The geological
formations are separated by major tectonic planes viz. Himalayan Frontal Thrust
(HFT), Main Boundary Thrust (MBT) and South Almora Thrust (SAT).
3
Fig.1.1: Location map of the study area showing its position in (A) India and in (B) Himalaya.
4
Table 1.1: Coordinates of the main localities in the study area (from South
to North).
S. No. Locality Longitude Latitude Approximate
Height in
Metres
1 Tanakpur 80o 06’ 45.4” 29
o 04’ 12.7” 245 m
2 Bastia 80o 05’ 09.4” 29
o 07’ 13.58” 406 m
3 Sukhidhang 80o 05’ 19.8” 29
o 10’ 08.4” 1096 m
4 Chalthi 80o 05’ 37.1” 29
o 11’ 52.7” 617 m
5 Amori 80o 03’ 43.8” 29
o 14’ 16.6” 913 m
6 Swala 80o 04’ 12.6” 29
o 15’ 30.4” 1229 m
7 Dhaun 80o 05’ 50.3” 29
o 16’ 35.9” 1450 m
8 Champawat 80o 05’ 44.2” 29
o 17’ 22.1” 1594 m
1.2 Physiography
The Kumaun Himalaya falls into five well defined physiographic belts, each
being a distinct geological unit: the Bhabhar, the Siwalik, the Lesser Himalaya, the
Great Himalaya and the Tethys or Tibetan Himalaya. The topography of the study
area is highly rugged (Fig. 1.2 A, B, C). The submontane Bhabhar is a piedmont belt
in the foothills. The Outer Himalayan Siwalik Range, 900-1500 m high, make up of
late Tertiary sedimentaries, exihibit a rugged and restive topography and is
characterized by steep hillslopes and deep valleys with crumbling walls scarred with
landslides. This youthful mountain range seems to be tectonically active and is
presumably still rising (Valdiya, 1980).
5
The Siwalik Himalaya is covered by thickly dense forest and therefore the
outcrops are sometimes badly weathered and covered by a thick soil. Ladhiya river is
a major and perennial tributary of river Kali (or Mahakali) flowing in SE direction
(Fig.1.2 D).
Fig.1.2: Field photographs showing generalised view of rugged topography in the study area,
(A) near Sukhidhang, (B) near Chalthi, (C) near Swala, (D) Ladhiya River in the study area.
The Lesser Himalaya 1500-2500 m high, made up of Precambrian-Paleozoic
sediments. It has a comparatively mild and mature topography with gentle slopes and
deeply dissected valleys which suggest that the rivers and streams are still furiously at
work.
6
1.3 Climate and Rainfall
The climate varies from Sub-tropical monsoon type (mild winter, hot summer)
to tropical upland type (mild and dry winter, short warm summer). Severe winter and
comparatively higher rainfall are the characteristic features in the northern parts of the
area. The year may be divided into four seasons viz. the cold winter season,
(December to February), the hot weather season (March to May), southwest monsoon
season (June to September) followed by post monsoon season (October to
November). The rainfall reaches its maximal in the monsoon season that occurs
between June to September. Rainfall, spatially, is highly variable depending upon the
altitude. In the Lesser Himalayan Zone (1000-3000 m above mean sea level)
maximum rainfall occurs about 70 to 80% in southern half. July and August are the
rainiest months. Rainfall rapidly decreases after September and it is the least during
November. The overall average annual rainfall of the area is 1085.62 mm (Central
Ground Water Board, 2009).
1.4 Previous work
Captain G. D. Herbert, one among the pioneers of Indian geology, carried out
extensive mineralogical survey of the vast region between the rivers Kali and Satluj
over the period from 1818 to 1825 (Herbert, 1842). His was the first-ever attempt to
undertake geological mapping of the Himalayan realm, and his map was published in
1844 in the thirteenth volume of the journal of the Asiatic Society of Bengal. Captain
Richard Strachey (1851) first crossed the Great Himalayan Range to explore the Ngari
Khorsum region of southwestern Tibet in 1848-49 and thus made the first sound
attempt at the geological study of Himalaya. Initiating in 1859 the systematic survey
7
of the Lesser Kumaun Himalaya, H. B. Medlicott (1864) studied the vast belt between
the rivers Ganga and Ravi and laid the foundation of the stratigraphy of the Lesser
and sub-Himalaya. He was followed by W. Theobold (1881) who carried out a
detailed study of the Siwalik belt between the Kali and Satluj, by R. D. Oldham
(1883, 1888) who furnished an outline of the geology of the Jaunsar-Bawar region in
northwestern Kumaun, and by C. S. Middlemiss (1885, 1887, 1889, 1890) whose
comprehensive exploration in the Lansdowne Hills and adjoining Dudhatoli massif in
the eastern Pauri-Garhwal, dealt with the problem, amongst others, of the intriguing
occurrence of the presumably older high grade metamorphic and granites upon the
unmetamorphosed younger sedimentaries. At about the same time C. L. Griesbach
(1880), who crossed the Nanda Devi massif through the trail passing along
Kathgodam and Bageshwar, was studying in great detail the fossiliferous Tethyan
realm of the Indo-Tibetan border (Valdiya, 1980).
In the easternmost part of the Kumaun foothills, just bordering the Kali river at
the Nepalese frontier, Misra and Valdiya (1961) made a detailed sedimentary and
petrological study of the Siwaliks. In this Tanakpur area the 8 km wide foothill belt
consists of normal sections of northwards dipping beds without repetitions, inversions
or imbrications (Gansser, 1964).
The Almora Crystalline Zone occurs as semi-elliptical outcrop surrounded by
inner and outer sedimentary belt of the Lesser Himalaya. It is constituted of
mylonites, mylonite gneiss, phyllonite, schistose quartzite, garnetiferous quartz
muscovite schist, granitic gneiss, garnetiferous quartz sericite schist, garnetiferous
biotite muscovite schist, biotite gneiss, augen gneiss, chlorite schist, altered basic
rocks, etc. A number of workers have worked on the Almora Crystalline Zone from
8
various angles e.g. regional structure, minor structure, metamorphism and the related
aspects (e.g. Auden, 1934, 1935, 1937; Heim and Gansser, 1939; Gansser, 1964;
Misra and Sharma, 1968; Sharma, 1971; Misra and Bhattacharya, 1972; Valdiya,
1980; Bhattacharya, 1981; Agarwal, 1994; Srivastava and Mitra, 1996; Bali and
Agarwal, 1999; Bhattacharya, 2008; Tripathy et al. 2009).
Kotlia et al. (2008) worked on magnetostratigraphy and lithology between Tanakpur
and Sukhidhang area and estimated the age of the studied section of Siwalik rock is
ca. 12.5 to 4 Ma.
Anbalagan and Singh (1996) worked around Sukhidhang of Tanakpur-
Champawat area in Kumaun Himalaya for landslide hazard and risk assessment
mapping. The risk assessment map of the Sukhidhang area shows that the high risk
(HR) and the very high risk (VHR) slopes are mostly located by the side of the south-
flowing Rela-ka-khola stream and north-flowing Khagota stream. A few isolated high
risk slopes can be seen on the northeastern and the eastern parts of the area. Low to
moderate risk (LR, MR) slopes are uniformly seen throughout the area. The human
dwellings and the agricultural lands are mostly located on the LR slopes and partly on
the MR slopes. The risk of human dwellings generally falls in the LR and at places in
the MR category. The Tanapur-Sukhidhang-Champawat road, passing through the
area, mostly falls on low to moderate risk slopes, except in few locations, where it is
on HR slopes (Agarwal et al. 2009; Agarwal and Sharma, 2011). Kothyari et al.
(2012) has also worked on landslides and neotectonics activities in the Main
Boundary Thrust (MBT) zone around Sukhidhang area.
9
1.5 Geology of the area
In the present research work a geological map of the study area is prepared on
1:50,000 scale (Fig.1.3). It is prepared on the Survey of India (SOI) toposheets Nos.
62C/3, 62C/4, 62C/7 and 62C/8. The study area falls in the Outer Himalaya and some
parts of the Lesser Himalaya. The Tanakpur and the Bastia falls in the Alluvium plain
and the Sukhidhang is in Siwalik group. The Chalthi falls in the Outer Lesser
Himalaya and the district Champawat falls in the Almora Crystalline unit. From
Tanakpur to Champawat, the area is characterized by various units viz. Alluvium
plain, Siwalik Group, Outer Lesser Himalaya and the Almora Crystalline unit. The
rock successions of the study area is mainly exposed in the Bhimtal Formation and the
Almora Group of rocks apart from the Siwalik Group of Tertiary rocks at the southern
part of the area, which is Late Tertiary to Quaternary exposed all along the foothill
belt of the Sub-Himalaya (Ground Water Board, 2009).
The various litho-tectonics subdivisions of the study area are as follows:-
North Almora Crystallines
----------------South Almora Thrust----------------
Outer Lesser Himalaya (Bhimtal Formation)
----------------Main Boundary Thrust----------------
Siwaliks
--------------Himalayan Frontal Thrust--------------
Gangetic Alluvium
South
10
Fig.1.3: Geological map of the study area, Kumaun Lesser Himalaya, modified after Valdiya,
1962, 1980.
Siwaliks
The Siwalik sediments continue laterally throughout the southeastern part of
the Kumaun Lesser Himalaya bounded between Himalayan Frontal Thrust in the
11
South and Main Boundary Thrust in the North. The Siwalik foothill belt consists of
normal sections of northwards dipping beds without repetitions, inversions or
imbrications. Locally, faults are responsible for a sudden change in dip, without,
however, cutting out much of the section. The lowest southernmost outcrops near
Bastia consist of soft and friable brownish to purplish fine grained sandstones, which
indicate oxidizing environment. North of the Bastia village almost 7 km before the
Sukhidhang, alternate bands of sandstone and shales (chocolate colour) are observed
dipping 42o
in the north direction. The overall Siwalik Group is composed of
sandstone, siltstone, clay and pebbles bed.
Upwards the sandstones become coarse with inclusions of yellow and brown
clay pellets. The rocks of the Siwalik group are also characterized by the “salt and
pepper” texture. The outcrops of the Siwalik rocks near Sukhidhang consist again of
fine grained but compact and hard, grey to greenish sandstone indicating a reducing
environment, with subordinate purple clay intercalations. A few coal seams are also
been observed within sandstone at different places along the Rela ka Khola-Hathi
Khor section (Fig. 1.4).
12
Fig. 1.4: Field photographs (A-F) showing coal beds within sandstone along Rela ka khola to
Hathi khor section.
Crystalline Units
Bhimtal Formation
It is bounded by Main Boundary Thrust (MBT) in the South and South
Almora Thrust (SAT) in the North. The quartzite rock in the study area is observed
approximately 8 km south of Chalthi (Fig. 1.5A). It is highly shattered and fractured
13
due to the effect of Main Boundary Thrust (MBT). Here the quartzite rock is pale
white in colour. It is hard and non-foliated formed due to the metamorphism of
sandstone.
The chlorite schist is exposed at 4 km south of Chalthi (Fig. 1.5B). It is
characterized by a foliated, fine to medium grained, low grade metamorphic rock. The
rocks are higly weatherd and fractured due to shearing. Phyllonite is also noticed in
this unit just before the Chalthi bridge.
Fig. 1.5: Field photographs showing (A) quartzite rock, Loc. 8 km south of Chalthi, (B)
chlorite schist, Loc. 4 km south of Chalthi.
Almora Crystallines
The Almora crystalline is bounded by South Almora Thrust (SAT) in the south
and North Almora Thrust (NAT) in the north. It is in the form of a thrust sheet, which
has moved southward from the higher Himalayan crystallines along the Main Central
Thrust (MCT) and covers the Lesser Himalayan sedimentaries (Agarwal, 1994;
Agarwal et al. 2011). It is mainly composed of quartzite, phyllonite, mylonite, gneiss
and schist rocks. The quartzite rock is exposed north of the Chalthi bridge it is highly
jointed, fractured and shattered (Fig. 1.6A). The mylonite rock is well exposed after
2.5 km north of Chalthi bridge (Fig. 1.6B). It is a fine grained compact rock produced
by the dynamic recrystallization of the constituent minerals resulting in a reduction of
14
the grain size of the rock. Small scale shear zones are also observed at different
places, it gives top to south sense-of-shear.
Fig. 1.6: Field photographs showing (A) quartzite rock just after Chalthi bridge, (B) mylonite,
Loc. 2.5 km north of Chalthi bridge.
1.6 Field work, Mapping and Sampling
The detailed geological study of the field area is carried out during four field
visits, to identify and record various rock types and structures. The geological field
studies broadly includes identification of the various rock types, lithological
assemblages, planar and linear structures on both mesoscopic and megascopic scales,
regional structure and the related aspects. A number of traverses have been taken from
south-north; east-west and also radial traverses have been taken to collect a large
number of oriented samples for further geological study in the laboratory (Fig. 1.7).
On the basis of these studies a geological map of the area has been prepared on
1:50,000 scale. The study area falls into two distinct groups Siwalik Group and
Almora Crystalline Group. The area shows a very rugged topography and it not
accessible to reach everywhere.
15
Fig.1.7: Sample location map of the Tanakpur-Champawat area, Kumaun Lesser Himalaya,
Uttarakhand.
Field studies reveal that several parts of the study area are structurally
controlled and neotectonically active. Such neotectonic activities are especially
associated with the configuration and evolution of the present day topography. Ample
evidence of active tectonics such as active landslides, river terraces, vertical down-
cutting of the rivers, deep gorges of rivers, triangular facets (flatirons) and tilting of
beds have been noticed in various parts of the study area (Agarwal et al. 2012).
16
Various planar and linear structures were identified in the field and plotted on
the map. A large number of strain markers are used for detailed strain analysis which
gives a quantitative picture of the amount of deformation undergone by the rocks of
the area.
1.7 Laboratory work and Methodology
Laboratory work mainly includes preparation of thin sections for petrographic
studies, structural analysis and strain estimation with the help of various strain
markers. Oriented rocks samples are cut along XZ and YZ sections and are polished
to enable for a better study of internal structures within the rocks.
For the petrographic studies, about 102 thin sections in the XZ and YZ planes
of the rock types have been prepared and studied under the petrological microscope
and also a number of photomicrographs are taken, showing relevant features of the
thin section. Thin sections of various rock types around Main Boundary Thrust
(MBT) and South Almora Thrust (SAT) as well as Siwalik rocks have been studied in
their XZ and YZ planes corresponding to X, Y, Z axes of the finite strain ellipsoid. A
large number of long and short axes of stretched quartz grains samples are collected in
the field and also observed in the thin sections have been measured mainly for strain
estimation with the help of various geometrical methods and the available softwares.
The data thus obtained have been used for estimation of two- and three-dimensional
strain.
The stretching lineation which defines the X direction of the finite strain is an
indicator of the shear sense direction also. This is mainly studied for the purpose to
identify the transport direction of the block.
17
Remote sensing and modern techniques of GIS is also used for the quantitative
morphometric analysis of the Ladhiya and Lohawati river basins. Lineament pattern
of the whole study area is also been analysed and plotted a rose diagram with the help
of Georient software.
1.8 The objectives of the present work
The main objectives of the present work are as below:
Detailed geological investigations of the area undergoing mass wasting.
The structural and geomorphologic framework of the area.
Study of lineament pattern using Remote Sensing data.
To analyze the hill slope instability that have already occurred and to evaluate
the failure mechanism and influence of geo-environmental parameter.
Propose a landslide Zonation model for future developmental planning in the
area.
1.9 Presentation of the work
The present works has been presented in 7 chapters and are supported by a
geological map, structural map, cross-sections, graphs, line diagrams, field
photographs and photomicrographs of rock thin sections.
Chapter-1 consists of an introduction to the present work mainly location and
approach of the study area, physiography, climate and rainfall, previous work,
geology of the area, laboratory work and the objectives of the present study.
Chapter-2 represents the structures of the study area on megascopic and mesoscopic
scales (linear and planar structure).
Chapter-3 deals with the petrographic study of the rock samples of the area and their
microstructures observed in the thin section.
18
Chapter-4 includes the strain estimation of the study area using different methods
and various strain markers.
Chapter-5 deals the morphometry study of the Ladhiya and Lohawati river basins
and also identify the various neotectonics features present in the study area.
Morphometric study represents that the major part of study area is presently under the
influence of active tectonics.
Chapter-6 includes the hill slope instability of the study area and to find out the
landslides along the Tanakpur-Champawat highway with their causative factors and
their morphometrical details. This chapter also focuses the major landslides present in
the area.
Chapter-7 deals with the general discussion and conclusions of all the studies which
have come out from the previous chapters.
A complete list of all the various references cited in the text is given at the end
of the present work.
19
Chapter 2
STRUCTURES
The present chapter describes the structures of the Tanakpur-Champawat area of the
Kumaun Lesser Himalaya, both on the megascopic and mesocsopic scales. One major
traverse across the strike of the litho-units together with several radial traverses have
been taken to unravel the structure of the area.
The study area is marked by a rugged topography and steep slopes and
therefore several parts are not accessible. The rock succession of the study area
mainly includes the Bhimtal Formation and the Almora Group together with the
Siwalik Group of Tertiary rocks at the southern parts of the area along the foothill belt
of the Outer Himalaya. The area is marked by two major tectonic planes viz. Main
Boundary Thrust (MBT) which separates the Siwalik rocks from those of the Lesser
Himalayan rocks and South Almora Thrust (SAT) that separates the Outer Lesser
Himalaya from the Almora crystalline unit.
The structural framework of the study area is described as:-
Megascopic structures
Mesoscopic structures
2.1 Megascopic structures
The structures developed on large scales (kilometers) are grouped here under the
megascopic structures. These structures are classified under two categories:-
a) Thrusts
b) Folds
20
2.1.1 Thrusts
a) Main Boundary Thrust (MBT)
The Main Boundary Thrust (MBT) is the major thrust in the study area that
separates the rocks of the Siwalik Group from the Outer Lesser Himalaya. In the
study area the MBT is observed north of Sukhidhang, about 8 km south of Chalthi
(Fig. 2.1A). It shows dip of 30o to 45
o towards NNW with a general strike of ENE-
WSW. The rocks of the MBT zone are highly sheared, shattered and pulverized.
South Almora Thrust (SAT)
The South Almora Thrust (SAT) is another major thrust in the study area that
separates the Almora crystalline unit from the Outer Lesser Himalaya. The SAT is
well exposed along the Ladhiya river valley near Chalthi (Fig. 2.1B). It shows
moderate dips around 45o towards NW and general strike direction is NE-SW.
Fig. 2.1: Field photographs showing (A) Main Boundary Thrust, Loc. 1.5 km north of
Sukhidhang, (B) South Almora Thrust as exposed along the Ladhiya river valley.
2.1.2 Folds
The mega-folds of the area are developed during the first phase of deformation
and are represented by a few antiformal and synformal folds. A major synform and an
antiform are observed between Sukhidhang and Amori (Fig. 2.2).The axial trends of
21
these folds are NE-SW, which roughly run parallel to the axis of the Outer Himalayan
folds.
Fig. 2.2: Generalised geological cross-section showing the structure of the Tanakpur-
Champawat area, Kumaun Lesser Himalaya.
2.2 Mesoscopic Structures
The structures which are observed in the hand specimens and also in the
outcrop are named here as mesoscopic structures. They range from a few centimeters
(in hand specimen) to tens of meter (in outcrop). These structures are helpful in
understanding the deformation processes and tectonic transport direction of the rocks.
The various mesoscopic structures observed in the present study area are described
under planar structures, linear structures and minor folds.
A structural map of the area has been prepared on 1:50,000 scale with the help
of Survey of India (SOI) toposheet no. 62C/3, 4, 7 and 8 to show the attitudes of the
various structural elements (Fig. 2.3).
22
Fig. 2.3: Structural map of the Tanakpur-Champawat area showing the attitudes of the planar
and linear structures.
23
2.2.1 Minor folds
In the present study area folds are observed at many places and they range
from a few cm to few meters.
a) F1 folds
The F1 folds are the first generation folds that are generally tight and
characterized by lithological variations. These folds are noticed 2 km north of Dhaun,
Dhaun-Diuri road section by feldspathic veins (Fig. 2.4A) and have thin limb and
thick hinges indicating the mobilization of quartzo-feldspathic material from limb to
the hinge zone and are controlled by lithology and conditions of high ductile strains.
b) Sheath folds
These are tube-shaped non-cylindrical folds formed in zones of high shear
strain. Although the sheath folds are believed to form as a result of shearing of pre-
existing folds bearing a slightly curved hinge (Ramsay, 1980) or double plunging
folds (Williams and Zwart, 1977; Minnigh, 1979; Skjernaa, 1989), a great majority of
sheath folds found in the interior of shear zones are formed by the evolution of folds
nucleated during the shearing event, and thus developed on foliations or layers lying
in close parallelism with the shear zone (Carreras et al., 1977; Rhodes and Gayer,
1977; Bell, 1978; Quinquis et al., 1978; Henderson, 1981; Jiang and Williams, 1999).
Sheath folds have been observed in mylonite rock of the SAT zone 8 km south of
Swala (Fig. 2.4B).
c) Chevron folds
Chevron folds are symmetric or slightly asymmetric folds with straight limbs
and sharp angular hinges. They are common in multilayers of alternating competent
and incompetent layers and thus combine both similar (in incompetent layers) and
24
parallel (in competent layers) fold geometries. Asymmetrical chevron folds are
observed 3 km south of Swala (Fig. 2.4C).
d) Recumbent folds
Recumbent folds are commonly observed along the SAT zone near Dhaun
(Fig. 2.4D).
Fig. 2.4: Field photographs showing (A) F1 fold 2 km north of Dhaun along Dhaun-Diuri road
section, (B) sheath fold, Loc. 8 km south of Swala, (C) chevron fold, Loc. 3 km south of
Swala, (D) recumbent fold near Dhaun.
e) Conjugate folds
A pair of asymmetric folds with opposite senses of asymmetry such that the
axial surfaces dip towards each other is termed conjugate folds. A common type of
conjugate fold is a box fold, where the fold angles are approximately 90o, forming an
almost rectangular structure (Park, 1997). Conjugate folds are observed at two
different locations i.e. 3.8 km north of Bastia and 3 km south of Amori (Fig. 2.5A &
B).
25
Fig. 2.5: Field photographs (A & B) showing conjugate folds, Loc. 3.8 km north of Bastia and
3 km south of Amori.
f) Plunging folds
The attitude of the fold axis is measured as the angle between the axis and the
horizontal. This angle must be measured in a vertical plane (Park, 1997). Plunging
folds are observed in the sedimentary rocks 3 km south of Sukhidhang and also in the
crystalline rocks near Dhaun (Fig. 2.6A & B). The plunge of these folds are 28o and
40o towards NE and SW.
Fig. 2.6: Field photographs (A & B) showing plunging folds, Loc. 3 km south of Sukhidhang
and near Dhaun.
26
2.2.2 Planar structures
The planar structures of the study area include foliation planes in the
metamorphic rocks and bedding planes in the sedimentary rocks. In the study area the
rocks show the following types of planar structures:
a) Primary bedding plane or plane of stratification (S0)
b) Foliation plane (S1)
c) Joints (S2)
(a) Primary bedding plane (S0)
The primary bedding plane (S0) is
commonly noticed in the sedimentary rocks or
less-to un-metamorphosed rocks and is indicated
by colour variations, lithological banding,
compositional layering and sedimentary
structures mostly in the Siwalik group of rocks
between Bastia and Sukhidhang (Fig. 2.8A-F).
The general strike directions of S0 are
NE-SW and dip varies from 30o to 77
o towards NW and SE. Local variations are also
observed at some places and this is due to the local disturbances present in the study
area. The attitudes of the S0 planes are plotted on stereoplot (Fig. 2.7).
Fig. 2.7: Stereoplot of S0 planes of the
study area.
27
Fig. 2.8: Field photographs (A-F) showing primary bedding planes at different locations in the
study area.
b) Foliation Plane (S1)
Foliation planes (S1) are developed due to the first phase of deformation
characterized by the re-alignment of minerals grains of primary bedding plane (S0),
when they are subjected to high pressure and temperature. Individual mineral grains
are aligned themselves perpendicular to the stress direction such that their long axes
are in the direction of these planes. Usually, a series of foliation planes can be seen
28
parallel to each other in the rocks of the study area (Fig. 2.9). Foliation planes (S1) are
characteristic features of the most metamorphic rocks of the area like gneiss and
schist.
Fig. 2.9: Field photographs (A-F) showing foliation planes at different locations in the study
area.
29
In the field the foliation planes are
recognized by alternate bands of dark
(melanocratic-mainly biotite, hornblende,
etc.) and light (leucocratic-mainly quartz
and feldspar) colour minerals present in
the gneiss rock termed “gneissosity”.
Foliation planes are also recognized in the
other rocks- mylonite, phyllonite, and
schist of the present study area.
The general strike direction of the foliation
planes in the study area is NW-SE and the
dip varies from 22o-76
o towards SW or
NE. The overall attitudes of the foliation planes (S1) of the study area are plotted on
stereoplot (Fig. 2.10).
c) Joints(S2)
Joints are fracture surfaces along which rocks or minerals have broken; they
are therefore surfaces across which the material has lost cohesion (Twiss and Moores,
1992). Most outcrops of rock exhibit many fractures that show very small
displacement normal to their surfaces and no, or very little, displacement parallel to
their surfaces. Such fractures are called as joints (Twiss and Moores, 1992). Joints
have been noticed in both sedimentary as well as in crystalline rocks of the study area
(Fig. 2.11A-F).
Fig. 2.10: Stereoplot of S1 plane of the study area.
30
Fig. 2.11: Field photographs (A-F) showing joints at different locations in the study area.
The joints in the study area are developed in sets; two sets of joints are very
common but three sets are also present at some places. The dip of the joint plane
varies from 4o to 78
o towards SSE-NNW direction. The attitudes of these joints have
been plotted on “Georient” ver. 9.5.0 software and thus a rose diagram has been
obtained (Fig. 2.12). The rose plot shows that the orientation of the joint plane is SSE-
NNW direction.
31
2.2.3 Linear structures
Linear structures are the linear features observed on the rock surfaces either in
hand specimens or in thin sections. In the study area the linear structures have been
observed at many places which are described below:
a) Mineral Lineation (L1)
Mineral lineations consist of a preferred orientation of either individual
elongate mineral grains or elongate polycrystalline aggregates. Mineral grain
lineations are formed by the parallel alignment of individual acicular or prismatic
mineral grains such as amphibole, by grains of minerals that have been stretched into
an elongate shape, or by mineral fibres that have grown in a preferred orientation.
Polycrystalline mineral lineations are formed by the preferred orientation of elongate
clusters of grains of a particular mineral measuring at least a few grains in diameter
Fig. 2.12: Rose plot showing trend of joints (S2) in
the study area.
32
(Twiss and Moores, 1992). The crystalline rocks of the study area show an average
trend of mineral lineation direction is NNE (Fig. 2.13A-C).
b) Stretching lineation (L2)
According to Hatcher (1995), stretching lineation (L2) is mainly defined by the
elongation of feldspar, mica aggregates, stretching of porphyroclasts and elongation
of recrystallized trails of quartz and quartzo-feldspathic minerals. Stretching
lineations are used as an important tool to understand the tectonic transport direction
(Brunel, 1986; IIdefonse and Caron, 1987) and is mainly defined by stretched mineral
grains, pebbles, porphyroclasts or aligned elongate crystals. It is easily noticed on
foliation plane, close to thrust and shear zone, direction parallel or less sub-parallel
indicates the direction of motion (Fig. 2.13D-F). The stretching lineations are more or
less sub-parallel close to the thrust or near the thrust contacts but show a gradual
deviation while moving away from the thrust.
33
Fig. 2.13: Samples with mineral lineations (A-C) and stretching lineations (D-F) collected at
different locations in the study area.
c) Slickensides (L3)
According to Hatcher (1995), slickensides are non-penerative linear structures
formed as a direct result of frictional sliding and frictional slip. Slickensides are
commonly noticed in quartzites at two places 4 km south of Amori and near Chalthi
along the SAT zone (Fig. 2.14A & B). Both the slickensides give the transport
34
direction towards SSW and WNW and the plunge amount of the slickenside is 72o and
76o.
Fig. 2.14: Field photographs (A & B) showing slickensides, Loc. 4 km south of Amori and
near Chalthi.
d) Boudins
According to Twiss and Moores (1992), boudins are linear segments of a layer
that has been pulled apart along periodically spaced lines of separation called boudin
lines. Boudins display a wide variety of shapes. In the study area boudins are
observed between Dhaun and Diuri road section 7 km north of Diuri (Fig. 2.15A &
B).
Fig. 2.15: Field Photographs (A & B) showing boudins, Loc. 7 km north of Diuri.
35
2.3 Shear zones
A shear zone is a general term for a relatively narrow zone with parallel to
sub-parallel boundaries in which shear strain is concentrated (Mitra and Marshak,
1988).
According to Twiss and Moores (1992), shear zones show a wide variety of
characteristics ranging from brittle through ductile features. Brittle shear zones,
commonly associated with faulting near the Earth’s surface, are characterized by
pervasive brittle fractures. Brittle-ductile shear zones show features that have
characteristics of both brittle and ductile deformation, such as extensional gash
fractures that are rotated by ductile deformation. Ductile shear zones show features
such as sigmoidally shaped foliation traces that indicate coherent deformation and a
smooth variation of strain across the zone.
In the study area shear zones are noticed at a number of places both in the
sedimentary and metamorphic rock units. Generally the shear zones give the shear
sense direction top-to-south (Fig. 2.16A-F). More commonly the shear zones are
observed mainly in the vicinity of the Himalayan Frontal Thrust (HFT), Main
Boundary Thrust (MBT) and the South Almora Thrust (SAT). The width of the shear
zone are on centimeter to meter scale both in the sedimentary unit as well as in the
crystalline unit.
36
Fig. 2.16: Field photographs showing (A-C) small scale shear zone in Siwalik rocks near
Bastia showing sense of shear 156o,101
o and 320
o, (D) sheared sandstone 6 km south of
Sukhidhang showing sense of shear 105o, (E-F) quartz veins in small shear zone showing
sense of shear 115o and 110
o , Loc. 1.8 km north of Chalthi.
2.4 Thrust-related structures
a) Ramp and Flat
Ramp and flat structures are observed in the sedimentary rocks of the study
area (Fig. 2.17). They are the characteristic features of thrust geometry and form a
step-like-pattern (staircase geometry). Ramp-flat geometry forms in both extensional
37
and compressional environment and can occur in frontal, oblique or lateral positions.
Ramps are oblique to the bedding/foliation plane cuts the hanging wall forming a dip
angle that is typically 30o to 45
o degrees and flats are fault surfaces that form parallel
to the bedding/foliation plane or at an angle of 10o or less. The structures are helpful
in understanding the orientation of thrust movement.
Fig. 2.17: Field photograph showing Ramp and Flat structure, Loc. 3.2 km north of Bastia.
b) Duplex
A thrust duplex is a system of imbricate thrust faults that branch off from a
floor thrust below and curve upward to join a roof thrust at a branch line above,
thereby forming a stack of horses (Twiss and Moores, 1992). The rock body that is
bounded by faults above and below is called a horse. Multiple fault horses form a
duplex (Boyer and Elliot, 1982). Duplex structures are observed in the thrust zone
near Bastia (Fig. 2.18A & B).
38
Fig. 2.18: Field photographs (A & B) showing duplex structure in the study area near Bastia.
39
Chapter 3
PETROGRAPHY AND MICROSTRUCTURES
The present chapter deals with the study of rock types and microstructures of the
present study area. For the present study area around 110 oriented rock samples are
collected covering southern and northern part of the study area. These samples were
cut along XZ and YZ planes for thin section study. The thin section study includes
mineral identification and microstructures of the various rock types in the study area.
Petrographic characteristics of various rock types and their microstructures are
described below:
1. Petrography
2. Microstructure
3.1 PETROGRAPHY
Siwaliks
a) Sandstone and siltstone
Bhimtal Formation
a) Quartzite
b) Chlorite schist
c) Phyllonite
Almora Crystallines
a) Quartzite
b) Phyllonite
c) Garnet-Biotite-Schist
40
d) Mylonites
e) Augen Gneiss
f) Mylonite Gneiss
3.1.1 Siwaliks
Petrographic study is important to know the characters of sandstone such as
degree of compaction, cementation and effect of pressure solution (Blatt, 1967;
Pettijohn, 1975). Lithology and relief, rate of subsidence of depositional basin and
system of sedimentation may also be derived from petrographic study (Pettijohn et.
al., 1973). The petrographic study of various thin sections of sandstone samples
are carried out with the help of petrological microscope. Thin section study shows that
the clastic grains are mostly sub-angular and sub-rounded. The Siwalik Group
consists of greenish to brownish, medium to coarse grained salt and pepper
sandstones. Brownish to greenish nodular siltstones are also present. The framework
grain of middle Siwalik consists more than 90% of quartz, some feldspar and little
amount of biotite and muscovite. Moderately sorted and sub rounded quartz grains
indicate the degree of transportation. Mineralogical and texturally the rocks are
mature but some sandstone show considerable amount of pore spaces (voids) with
poor cementation. Mineralogical and textural characters are the fundamental
properties of any sedimentary rocks it have direct relationship with environment of
deposition and provenance.
41
a) Quartz
The framework grains of sandstone comprise mainly quartz, some feldspar
and few amounts of micaceous minerals. Quartz dominates the major framework
grain of the Siwalik sediment its percentage varies from 80% to 95%. Quartz grains of
the sandstones consists of a single crystal i.e. monocrystalline or an aggregate of
crystals i.e. polycrystalline (Conolly, 1965; Blatt, 1967).
The overall grains texture is equigranular with low relief. The grains are
bounded together with intricate boundaries and usually small quartz crystals
developed randomly between large crystals with appreciable amount of matrix. The
overall thin section of Siwalik rock shows well-sorted, sub-rounded to sub angular,
loosely packed detrital quartz grains (Fig. 3.1A & B). The total majority of clasts of
sandstone are sub-hedral, showing hypidiomorphic texture of the rock.
b) Feldspar
Feldspar constitutes less than 10% of the fragmental grains. The thin section
shows angular to sub-angular feldspar grains. Both types of feldspar, potash feldspar
and sodic feldspar are observed in few thin sections and are characterized by lamellar
twinning (Fig. 3.1C & D).
c) Mica
Micaceous minerals are common in few thin sections of Siwalik rocks; both
muscovite and biotite are observed (Fig. 3.1E & F). Muscovite is colourless appears
as shapeless plates or elongated laths with positive relief and high birefringence. Like
quartz, muscovite is most stable mineral and effectively resists chemical alteration in
the sedimentary environment. Kinking in muscovite is also seen in some thin sections.
42
Biotite appears as plates or laths, coloured and strongly pleochroic in brown, reddish-
brown and yellow (Read, 1970).
Fig.3.1: Photomicrographs (between X polars) showing (A & B) sub-angular to sub-rounded
quartz grains, (C & D) feldspar with lamellar twining, (E & F) elongated laths of micaceous
minerals.
3.1.2 Bhimtal Formation
a) Quartzite
The quartzite rock mainly constitutes fine to medium subhedral grains
of quartz (Fig. 3.2A & B) and some micaceous minerals mainly muscovite and biotite
43
as an accessory mineral. In thin section study it is observed that the larger and
medium grains of quartz are aligned parallel to the micaceous minerals; this is due to
the effect of thrust.
Fig. 3.2: Photomicrographs (between X polars) (A & B) showing fine to medium sub-grains
of quartz and effects of thrusting.
b) Chlorite Schist
It is low grade metamorphic rock with medium to large sheet like grains
arranged in a preferred orientation. It has more than 50% platy and elongated minerals
like mica, chlorite, talc etc. The preferred orientation of flaky minerals marks the
schistocity (Fig. 3.3).
Fig. 3.3: Photomicrograph (between X polar) showing chlorite schist together with biotite
which marks the preferred orientation.
44
c) Phyllonite
The rock is mostly composed of fine grained quartz minerals and some
phyllosilicate minerals muscovite and biotite (Fig. 3.4A & B). In general the thin
section shows alternate bands of quartz and phyllosilicate minerals. The phyllosilicate
mineral represents prominent effect of ductile deformation and occasionally show
minor thrusting, crenulation cleavage and S-C structures.
Fig. 3.4: Photomicrographs (between X polars) (A & B) showing fine grained quartz.
3.1.3 Almora Crystallines
a) Quartzite
The rock is mainly constituted of medium to fine anhedral grains of
quartz. Prominent metamorphic effects are noticed in the rock slide. The quartz grains
show parallel to sub parallel alignment, stretching and effects of recrystallization (Fig.
3.5A & B).
45
Fig. 3.5: Photomicrographs (between X polars) (A & B) showing recrystallization of quartz
grains.
b) Phyllonite
The rock is mainly composed of fine grained mineral of quartz and some
micaceous minerals mainly muscovite and biotite (Fig. 3.6A & B). Alignment of
alternate bands of quartz and micaceous minerals are observed in the thin section
study. Prominent effect of dutile deformation is noticed in micaceous minerals.
Fig. 3.6: Photomicrographs (between X polars) (A & B) showing fine grain minerals of quartz
and mica with alternate banding.
c) Garnet-Biotite-Schist
In thin section study the rock is mainly composed of garnet, biotite, quartz and
some muscovite. The schistosity plane is marked by a preferred alignment of biotite
(Fig. 3.7A). Quartz grains are generally strain-free and appear to have formed by
dynamic recrystallization. Garnet porphyroblasts are present along the biotite minerals
46
(Fig. 3.7B). Occasionally, the biotite layers show micro-folding and effects of intense
shearing.
Fig. 3.7: Photomicrographs (between X polars) showing (A) schistosity plane of biotite
mineral, (B) stretched garnet porphyroblast and elongated biotite.
d) Mylonites
A mylonite is a foliated and usually lineated rock that shows evidence for
strong ductile deformation and normally contains fabric elements with monoclinic
shape symmetry (Bell and Etheridge, 1973; Hobbs et al. 1976; White et al. 1980;
Tullis et al. 1982; Hanmer and Passchier, 1991).
According to Sibson (1977), mylonite is a fine-grained, compact rock
produced by dynamic recrystallization of the constituent minerals resulting in a
reduction of the grain size of the rock. The study of mylonites has developed a great
interest because of its confined to narrow zones of intense deformation. This study
concerned to the mode of rock deformation under extreme condition. Classification of
mylonites is based on the percentage of matrix as compared to porphyroclasts (Spry,
1969; Sibson, 1977; Scholz, 1990; Schmid and Handy, 1991). Mylonites which are
observed in the study area are described below:
1) Protomylonite
2) Mylonite
47
3) Ultramylonite
1) Protomylonite
A coherent crush-breccia composed of megascopially visibly fragments that
are generally lenticular and are separated by megascopic gliding surfaces filled with
finely ground material. The fragments or “megaporphyroclast”, make up more than
about 50% of the rock. Protomylonite commonly resembles conglomerate or arkose
on weathered surfaces. Features of the original rock, such as stratification and
schistosity, may be preserved in the larger fragments (Higgins, 1971). The rock
mainly includes quartz, micacous minerals mainly biotite, muscovite and plagioclase.
Mylonitic foliation is here defined by the alternate bands of quartz minerals and
micaceous minerals which are oriented in a preferred direction (Fig. 3.8A & B).
Fig. 3.8: Photomicrographs (between X polars) (A & B) showing protomylonite with
mylonitic foliation accentuated by mica.
2) Mylonite
A coherent microscopic pressure-breccia with fluxion structure that may be
megascopic or visible only in thin section and with porphyroclasts generally larger
than 0.2 mm. These porphyroclasts make up from about 10 to about 50 percent of the
rock (Fig. 3.9A & B). Mylonites generally show recrystallization and even new
48
mineral formation (neomineralization) to a limited degree, but the dominant texture is
cataclastic (Higgins, 1971).
Fig. 3.9: Photomicrographs (between X polars) (A & B) showing mylonite with porphyroclast
of quartz grains and a well developed mylonitic foliation.
3) Ultramylonite
A coherent, aphanitic, ultra crushed pressure breccia with fluxion structure, in
which most of the porphyroclasts have been reduced to breccias streaks and few
remaining porphyroclasts are smaller than 0.2 mm. These porphyroclasts make up less
than about 10 percent of the rock (Fig. 3.10A & B). In hand specimen and outcrop
ultramylonites are commonly homogeneous appearing rocks (although many have
compositional layering), easily confused with chert, quartzite or felsic volcanic rock.
Ultramylonite represent the highest stage in intensity of mylonitization in the series
protomylonite-mylonite-ultramylonite (Higgins, 1971).
Fig. 3.10: Photomicrographs (between X polars) (A & B) showing ultramylonite with a fine
grained matrix (> 90%).
49
e) Augen Gneiss
Augen gneiss derived from the German word meaning "eyes" is a coarse-
grained gneiss rock resulting from the metamorphism of granite, which contains
characteristic elliptic or lenticular shear-bound feldspar, quartz, and garnet
porphyroclasts are common minerals which form augen (Fig. 3.11A). The thin section
study shows prominent foliation plane defined by micaceous minerals biotite and
muscovite. Shear-bound quartz grains and recrystallization of quartz grains in the
form of quartz ribbon is also noticed (Fig. 3.11B).
Fig. 3.11: Photomicrographs (between X polars) showing (A) shear bands, (B) recrystallised
quartz ribbons.
f) Mylonite Gneiss
The thin section shows prominent development of mylonitic texture formed by
stretching of minerals, recrystallization of quartz grains and pulverization. Foliation is
defined by parallel to subparallel alignment of micaceous minerals. One set of
prominent foliation is observed within this unit which is defined by the alternate layer
of quartz and biotite (Fig. 3.12A). The thin section shows fine to medium grained
matrix of quartz, biotite and muscovite. Quartz occurs both as porphyroclasts as well
as inclusions within the larger grains of alkali feldspars and plagioclases. A prominent
50
porphyroclast of plagioclase is observed within fine grained groundmass of quartz and
biotite (Fig. 3.12B).
Fig. 3.12: Photomicrographs (between X polars) showing (A) prominent foliation plane,
defined by alternate bands of quartz and biotite, (B) porphyroclast of plagioclase within fine
grained groundmass of quartz and biotite.
3.2 Microstructures
Microstructures are the most important tool to understand the tectonic
evolution of the crystalline units. On the basis of detailed thin section studies the
following types of microstructures are noticed in the study area which is as below:
a. Porphyroclasts
b. Mica Fish
c. Micro Folds
d. S-C Structures
e. „V‟-pull-apart Microstructures
f. Book-shelf structure
g. Quartz ribbon structure
(a) Porphyroclasts
A large single crystal is commonly observed in the ductile shear zone known
as porphyroclasts. These are rounded or angular mineral grains of feldspar, quartz,
51
biotite and garnet etc. embedded in the finer crushed matrix of a rock produced by
cataclasis. Both symmetric and asymmetric trails are observed in the thin section
study. The asymmetric trails are used to identify the sense-of-shear in a deformed
rock.
The porphyroclasts are occurring in a variety of shapes with respect to their
trails. In the study area various types of porphyroclasts are noticed which has been
described below:
(a) θ-type
(b) Ф -type
(c) σ-type
(d) δ-type
(a) θ-type: θ-type mantled clasts
lack wings but have a mantle with
orthorhombic symmetry (Passchier
1994). Because of lack of trail (wings)
it is not used for sense-of-shear
indicator. θ-type porphyroclast are
commonly observed in the gneiss rock
after Swala (Fig. 3.13).
(b) Ф-type: This type of porphroclasts has symmetrical trails and it is not used for
sense-of-shear indicator. Ф-type mantled clasts are most common in high-grade
relatively coarse grained mylonites (Passchier and Trou, 2005). Thin section study
shows symmetrical trail porphyroclast, observed in mylonite rock after 2 km Amori
(Fig. 3.14A & B).
Fig. 3.13: Photomicrograph (between X polar)
showing θ-type mantled porphyroclast.
52
Fig. 3.14: Photomicrographs (between X polars) (A & B) showing Ф-type mantled
porphyroclasts showing symmetrical trail.
(c) σ-type: σ-type mantled porphyroclasts are asymmetrical and have wide trails
with a nearly straight outer side. The inner side is usually concave toward the median
plane (the plane parallel to the shear zone and bisecting the porphyroclast). The shape
has been described as stair-step, because the two other sides offset in two directions,
just like a rise and run of a stair. The tail shape is believed to form as the foliation
drags the softer mantle (Winter, 2001). This type of mantled porphyroclasts is noticed
in the mylonite rock of South Almora Thrust (SAT) zone before Swala it gives sense-
of-shear top to south (Fig. 3.15A).
(e) δ-type: In δ-type mantled porphyroclasts both sides of the mantle are curved,
and an embayment is formed on the inner side. δ-types are believed to begin as σ-
types and the curvature probably forms as the core rotates during further (Winter,
2001). The centre line of a crystal and the median line of a tail cut each other in δ-type
porphyroclast. It is noticed in gneiss rock of Almora crystallines 2 km north of Dhaun
and sense-of-shear is top to south (Fig. 3.15B).
53
Fig. 3.15: Photomicrographs (between X polars) showing (A) σ-type mantled porphyroclast
gives top to south sense-of-shear, (B) δ-type mantled porphyroclasts showing sense-of-shear
top to south.
(b) Mica Fish
Mica fish are elongate lozenge or lens-shaped single crystals, which are most
common in mica-quartz mylonites and ultramylonites. They characteristically lie with
their longest dimension at a small angle to the mylonitic foliation (Passchier and Trou,
2005). Mica fish is believed to form commonly in rocks where pre-existing large mica
grains are boudinaged by a combination of brittle and crystal-plastic processes
(Eisbacher, 1970). The mica cleavages may parallel the elongation direction or they
may be oriented parallel to the slip direction of the shear zone (Winter, 2001). The
mica fish is observed in mylonite rock 3 km north of Swala (Fig. 3.16A & B).
Fig. 3.16: Photomicrographs (between X polars) (A & B) showing mica fish of biotite and
muscovite near Swala.
54
(c) Micro Folds
The presence of micro fold is observed in the study area is relatively rare.
Usually it is develop in the schistose and mylonitic layers of the crystalline rocks.
Micro folds have been noticed in some thin sections of crystalline unit. It is well
known that crenulation folds are formed by small scale folding of very thin layers or
laminations within a rock. Here in the thin section it is noticed that the axial plane of
the micro fold is asymmetrical and it suggest that it is formed under strong shear
conditions. In the study area the micro folds of quartz shows top to south sense-of-
shear for crystalline unit (Fig. 3.17A).
(d) S-C Structures
The S-C structures are generally developed in the mylonitic rocks of the study
area (Berthe‟ et al., 1979; Simpson and Schmid, 1983; Lister and Snoke, 1984;
Simpson, 1986; Hanmer and Passchier, 1991). Lister and Snoke (1984) suggested that
any kind of structure that is composed of two planar structures formed during
progressive shearing event be called as S-C structures (S-C fabric). The C-surface is
the „cisaillement‟ (French word, which means Shear) or shear plane defined by the
trails of fine micas commonly connected to the tips of the porphyroclasts and S-
surface is defined by the preferred orientation of mica grains (schistosity plane)
(Berthe et al., 1979). With progressing shearing, the angle between S and C surfaces
tends to reduce progressively due to rotation of the S-surface, whereas the C-surface
maintains an approximately constant orientation. The S- (flattening) foliation is
inclined to the shear zone boundaries, antithetic to displacement sense, whereas the C-
(shearing) foliation is parallel to the shear zone boundaries with synthetic
displacement across it (White et al., 1980; Mawer and White, 1986).
55
S-C structure is more commonly used for shear sense indicator, in the study
area it shows top to south sense-of-shear. It is commonly developed in the South
Almora Thrust (SAT) zone (Fig. 3.17B).
Fig. 3.17: Photomicrographs (between X polars) showing (A) micro fold within quartz vein,
(B) S-C structure shows top to south sense-of-shear.
(e) ‘V’-pull-apart Microstructures
Hippertt (1993) introduced a new potential shear sense indicator in the form of
pull-apart structures that occur in the rim of feldspar porphyroclasts at low
metamorphic grade. Fractures in the edge of the porphyroclasts may open to a V-
shape and are filled with quartz or any another mineral. In some mylonites these V-
pull-apart microstructures have a persistent asymmetry that can be used to determine
sense of shear. „V‟-pull-apart microstructure is observed in thin section of mylonite, it
shows sense-of-shear top to south (Fig. 3.18A).
(f) Book-shelf structure
Book-shelf microfracturing in feldspar is common at low-grade conditions,
splitting the grains up into elongate „book-shaped‟ fragments (Passchier, 1982; Pryer,
1993). According to Pryer (1993) the antithetic fracture sets are more common in the
low temperature range and synthetic fractures at higher temperature. A book-shelf
structure is noticed in the gneiss rock it shows sense-of-shear top to south (Fig.
3.18B).
56
Fig. 3.18: Photomicrographs (between X polars) showing (A) „V‟-pull-apart microstructure in
mylonite rock, (B) book-shelf structure is noticed in the gneisses.
(g) Quartz ribbon structure
It is highly elongated disc- or lens-shaped crystal or aggregate of quartz,
common in mylonites and high-grade rocks. Quartz ribbons form by flattening of
originally equidimensional quartz grains, or possibly by migration of grain boundaries
to form single large grains from more fine-grained parent aggregates. They may
exhibit undulose extinction, or be recrystallised into polycrystalline ribbons (Passchier
and Trou, 2005). Quartz ribbons are observed in thin section of mylonite rocks of
South Almora Thrust zone near Swala (Fig. 3.19A & B).
Fig. 3.19: Photomicrographs (between X polars) (A & B) showing quartz ribbons in mylonite
rocks.
57
Chapter 4
STRAIN ANALYSIS
Introduction
Strain analysis is a useful tool for understanding the deformation pattern of an area. It
is the quantification of magnitudes and histories of strain using measurements on
natural strain markers. The strain analysis is carried out on a number of tectonites and
deformed elements like porphyroclasts, elongated pebbles, etc. The strain data can
help to throw light on the mode of development of a multitude of geological
structures, for instance, discussions on the origin of secondary foliations and
crystallographic fabrics have revolved around their supposed relationship to the finite
strain in the rock. There are various methods to evaluate the strain in deformed rocks
(Cloos, 1947; Flinn, 1956; Ramsay, 1967; Hossack, 1968; Dunnet, 1969, Elliott,
1970; Lisle, 1977, 1985; Ramsay and Huber, 1983).
In recent years a number of workers has been worked on this tool (Flinn,
1962; Ramsay, 1967; Ramsay and Huber, 1983; Twiss and Moores, 1992; Ghosh,
1993; Hatcher, 1995; Yamaji, 2008; Wilson et al., 2009; Galan et al., 2009). A few
workers have worked for strain analysis in some selected areas of the Himalaya
region (Misra and Sharma, 1972; Jain, 1975; Sinha Roy, 1980; Bhattacharya, 1987;
Bhattacharya and Agarwal, 1985, 1989; Bhattacharya and Siawal, 1985; Agarwal,
1994; Bali and Agarwal, 1999; Singh, 1991; Agarwal, 1990; Gairola and Singh, 1993;
Joshi, 1999; Srivastava and Tripathy, 2005, 2007; Agarwal and Bali, 2008; Mamtani
et al., 2009; Agarwal et al., 2010).
58
There are two types of strain:-Homogeneous strain and Heterogeneous strain,
In homogeneous strain distortions are same in everywhere. As a result straight lines
are straight and parallel lines are parallel. In heterogeneous strain distortion or dilation
may vary from place to place. Straight lines may not be straight in general and parallel
lines may not be parallel in general.
The present study is aimed at identifying the strain markers and indicators in
the study area. This study is carried out with the help of few strain markers on
geometric methods. Strain analysis has been carried out along the Siwalik rocks and
the crystalline rock units of the Outer Lesser Himalaya. A traverse has been taken
across the Himalayan Frontal Thrust (HFT), Main Boundary Thrust (MBT) and the
South Almora Thrust (SAT). To carry out strain analysis deformed porphyroclasts
have been identified and the following methods have been employed:
(A) Grain Shape Analysis of Quartz (Panozzo Plots)
(B) Deformed Porphyroclasts
(a) Fry method
(b) Rf / Ф method
4.1A) Grain Shape analysis of Quartz (Panozzo Plots)
The Panozzo plots (Panozzo, 1984) constitute a projection method that give
the shape and orientation of a strain ellipse from particle boundaries (Fig. 4.1). The
grain boundaries either from the thin section or directly from the rock surface are
drawn as closed polygons. These polygons are rotated through at 180o
and are
projected on a reference line. The sum of the lengths of these projections (∑p[α]) is
calculated for each increment angle (Panozzo, 1984). The long axis of the summarised
59
strain ellipse is (∑p[α]) max. The angle θ between (∑p[α]) max and the reference line is
the dip of the ellipse. The ratio (∑p[α]) max / (∑p[α]) min is the ellipticity (R) of the
fabric. The study is done with the help of Fabric 8 software. The fabric 8 software
plots the normalized sums (∑p[α]) of the projected polygon lines versus the rotation
angle α and the maximum is shown by the vertical line. Rose diagram of all the
(∑p[α]) is plotted to carry out the form analysis. The “Strain Ellipse” is thus
calculated from R and θ.
The aim of the study is to understand the effects of stresses on quartz grains.
The Panozzo method has been adopted on 16 thin sections of rock samples. The
outcome values range from 1.07 to 1.65. The values suggest high strain around Swala
and low strain around Bastia.
4.1B) Deformed Porphyroclasts
In recent years, many workers have shown that deformed elements like
porphyroclasts, pebbles etc. are good strain markers (Hofmann, 1965; Nemdec, 1965;
Behr, 1967, 1968; Ramsay, 1967; Dunnet, 1969; Elliot, 1970; Talbot, 1970; Oertel,
1970; Mukhopadhya, 1973; Mathews et. al., 1974; Shimamoto and Ikeda, 1976; Lisle,
1977, 1985; Theoff, 1979; Siddans, 1980; Bhattacharya, 1985; Wenk, 1998). As such,
a few methods are used for measuring strain from such markers, both qualitatively as
well as quantitatively.
In the study area, a number of deformed porphyroclasts of feldspar and quartz
are noticed in the Main Boundary Thrust zone and the South Almora Thrust zone. The
study is based on measurement of the long and short axes of the deformed strain
markers. The following methods are used:-
(a) Fry method
60
(b) Rf / Ф method
Fig. 4.1: Panozzo’s plot of grain-shape analysis of quartz, south to north along Tanakpur-
Champawat highway.
…Contd.
61
62
(a) Fry Method
The Fry technique, devised by Fry (1979), provides an excellent practical
method for finding the best fit solution to the strain ellipse (Fig. 4.2). Bulk rock strain
can be calculated using the center to center method, according to the redistribution of
points in a deformed rock and the distances between these points as extended line
elements (Ramsay and Huber, 1983). The advantage of the Fry method is that it
provides a graphical solution to the centre to centre method which is both rapid and
accurate.
The method can be applied to a plane with markers which changed their mutual
position during flattening or shearing. However this method is inappropriate for
purely grain supported fabrics.
The Fry method procedures are as follows:-
All identified centre points of the objects are plotted on a plain sheet of paper.
Reference line mark on the sheet of paper (e.g. north or the regional stretching
lineation etc.).
Take another sheet of tracing paper and mark and orientation to match that on
the other sheet.
Also mark the reference point on the paper.
Place the reference point on the tracing paper over one of the marked centres,
keeping the two sheets oriented parallel against the same marker.
Trace off the centre points of all the other markers.
Move the reference point onto the next centre and repeat the process, keeping
the two sheets oriented parallel against the same marker.
63
Fig. 4.2: Fry plots of the rocks of the study area along Tanakpur-Champawat highway.
64
…Contd.
65
Repeat the procedure for all centres.
The result is a scatter of points but the area around the reference point is
vacant with an elliptical shape.
The shape (axial ratio) and orientation (with respect to the reference direction)
of this vacant ellipse represents the strain ellipse.
66
The Fry method has been applied on 16 thin sections of rock samples. The output
values of the Fry method are ranges from 1.30 to 2.00. The higher values suggest that
the Dhaun area has more strained than the Bastia.
(a) Rf / Ф Method
The Rf / Ф Method is used to assess the strain characteristics of the rocks (Fig.
4.3). The Rf / Ф Method was devised by Ramsay (1967) and was improved by Dunnet
(1969). Later on, Lisle (1985) gave a detailed description of the complete method.
The Rf / Ф technique is based on calculating the theoretical distribution of
final ellipticities and orientations that result from imposing different strains on objects
that have a known initial ellipticity and orientation. The final ellipticity Rf and
orientation Ф of a deformed object depend on the initial ellipticity, Ri, on the initial
orientation (ϴ) of the undeformed object and on the ellipticity Rs of the imposed strain
ellipse.
A number of studies (Lisle, 1977; Lisle and Savage, 1983) have shown that
marker shapes are related to their size. This indicates a non-passive strain response by
the markers and can be detected effectively by plotting a graph of the long axis and
short axis dimensions (Ramsay, 1967; Elliot, 1970).
Ideally, the direction of the maximum principal axis of strain is chosen as the
reference direction. But, any other direction can also be used as a reference. If the
long axis of an object is parallel to the direction of the maximum lengthening S1 of the
imposed strain, then the final ellipticity Rf of the deformed object is a maximum as
given by
Rf(max)= RiRs
67
On the other hand, if the long axis of an object is parallel to the maximum
shortening direction S3 of the imposed strain, the final ellipticity Rf of the deformed
object is a maximum given by
Rf (min) = Ri / Rs if Rs < Ri
Rs / Ri if Rs > Ri
For any other initial orientation of the objects the final deformed ellipticity is
intermediate between these two values.
In the strain diagram, the open curve means deformed ellipses of any
orientation can occur whereas closed curve indicates that orientation of the deformed
ellipses are restricted to orientations of IΦI < 450.
Ellipticity of the strain ellipse Rs and the maximum initial ellipticity Ri can be
determined analytically by the following equations:
Rs2
= {Rf (max) Rf (min) if Rs > Ri }
{Rf (max) / Rf (min) if Rs < Ri }
Ri2 = {Rf (max) / Rf (min) if Rs > Ri }
{Rf (max) Rf (min) if Rs < Ri }
Where Rf (max) and Rf (min) are maximum and minimum values of Rf, measured
on a set of deformed object (widely scattered and isolated data points are ignored).
If the total fluctuation of long axes of deformed objects in the given plane does
not exceed 900
then, the geometric (Rg) or harmonic mean (H) of the data sets can be
68
obtained (Lisle, 1979). If the fluctuation is more than 900
then the arithmetic mean of
Rfs can be assumed as Rs i.e. Rs is approximately equal to H or Rg or Rf depending
upon the total fluctuation 2 Φ.
Thus the method can be performed in the following steps:-
Measure each of the long and orthogonal short axes of an ellipse.
Calculate the Rf of the ellipse (Rf=long axis length/short axis length).
Draw a reference line.
Measure phi (Φ), the angle between the long axis of the ellipse with
respect to the reference line.
Plot the above values on Rf - Φ graph.
The Rf / Φ technique has been applied on 16 thin sections of rock samples of
the study area and their graphs have been prepared including their chi2 plot. The plots
show that the Rf / Φ values range between 1.7 and 2.2. The result suggest that the
rocks of the vicinity of the South Almora Thrust zone have higher strain values.
69
Fig. 4.3: Rf / Ф diagram and the chi2 graphs of the rocks of the Tanakpur-Champawat area.
70
…Contd.
71
…Contd.
72
73
Chapter 5
MORPHOMETRIC ANALYSIS AND NEOTECTONICS
Morphometric analysis is a quantitative description and analysis of landforms as practiced
in geomorphology that may be applied to a particular kind of landform or to drainage
basins and large regions generally. The morphometric analysis is widely used to assess the
drainage characteristics, watershed development and management plans of the river
basins. These studies have also proved to be very useful tools to study the ongoing
tectonics. Stream frequency, drainage density, drainage texture and other parameters of the
river basin shows the result of the strong structural or tectonic control over the drainage of
the area.
5.1 Morphometric Analysis
The drainage network in the young mountain chains is believed to represent a good
indicator of active tectonics. The drainage basin morphometric analysis reflects steady
state condition of rocks during active deformation (Seeber and Gornitz, 1983; Ouchi,
1985; Marple and Talwani, 1993; Koons, 1995; Hallet and Molnar, 2001; Arisco et al.
2006). A simple approach to describe such adjustments of drainage network against
lithological variations during the ongoing tectonic processes is to calculate the parameters
which describe the physical changes in the drainage system. The overall morphometric
analysis of the drainage network has been carried out following the methods suggested by
Horton (1945) and Strahler (1964). The drainage morphometry of watershed in a terrain is
not only controlled by climatic conditions prevailing in the area but also by the lithology
and the result of release of stresses along the tectonic planes. Geological structures have
great control over the drainage as they influence the nature of flow, erosion and sediment
transport (Nag et al. 2003). The permeability, the structural characteristics and the degree
74
of fracturing also affect the extent to which the material can be detached by fluvial process
(Derbyshier et al. 1981). Therefore, the role of the geological structures in the
development of drainage networks can be better understood by a quantitative
morphometric analysis (Nag et al. 2003). Morphometric analysis has been defined as
quantitative measurements of landscape shape (Keller and Pinter, 1996). Geology, relief
and climate are the primary determinants of running water functioning at the basin scale
(Lotspeich and Flatts, 1982; Frissel et al. 1986). Morphometric analysis of drainage basin
carried out by Horton (1945), Strahler (1952) and others is based on the fact that for the
given conditions of lithology, climate, rainfall and other relevant parameters of the basin,
the river network, the slope and the surface relief tend to reach a steady state in which the
morphology is adjusted to transmit the sediments and excess flow produced. This study
also allows the description of the physical changes in drainage system over time in
response to natural disturbances or human impact. Morphometric studies also delineate
physical changes in drainage system over time in response to natural disturbances or
anthropogenic activity (Thomson et al. 2001).
In the present study, morphometric analysis of the Ladhiya and Lohawati River
Basins has been carried out with the help of Survey of India topographical maps on
1:50,000 scale (Fig. 5.1). The drainage network of the Ladhiya and Lohawati River Basin
and its sub-basins have been digitized and quantitative analysis of the morphometric
parameters of the basin like stream number, stream length, and stream order etc. have been
calculated using ARC VIEW 3.2 and ERDAS 8.5 softwares. The morphometric
parameters have been divided into three categories viz. linear parameters, areal parameters
and shape parameters. The overall drainage network has been analysed as per Horton
(1945) laws and the ordering of streams has been followed as given by Strahler (1964).
75
5.1.1 Linear Parameters
a) Stream Order (Nu)
Stream orderings refers to the determination of the hierarchical position of stream
within a drainage basin. According to Strahler (1952), ordering of stream begins from the
fingertip tributaries, which do not have their own feeders (Fig. 5.1). Such fingertip streams
are designated as first order streams. Two streams when join together, from second order
stream just below junction. Similarly two second order streams meet to make stream of
third Order and process continues till the trunk stream is given the highest order. The
number of streams (N) of each order (U) for Ladhiya and Lohawati basin is given in
details in Table 5.1 and 5.2. The details of the stream characteristics confirm Horton‟s
(1945) first law of stream numbering which states that the number of streams of different
orders in a given drainage basin tends closely to approximate an inverse geometric ratio.
Fig. 5.1: Map showing divisions of sub-basins in Ladhiya & Lohawati river basins, Uttarakhand
(after Agarwal et al. 2012).
76
b) Stream Length (Lu)
It is the total length of streams of a particular order. The stream length
characteristics of the sub-basins conforms Horton‟s (1945) Second law, “Laws of Stream
Length”, which states that the average length of the streams of each of the different orders
in a drainage basin tends closely to approximate a direct geometric ratio. It is the total
length of streams of a particular order. The stream length of all sub-basins of various
orders has been measured on Survey of India topographical maps. The total stream length
of the Ladhiya and Lohawati river basins is 3504.39 km and 634.87 km respectively, while
the stream lengths of the sub-basins are given in Table 5.1 and 5.2.
77
Table 5.1: Linear parameters of the Ladhiya River basin, Kumaun Lesser Himalaya, Uttarakhand (after Agarwal et al. 2012).
Sub-
basin
no.
Stream order Total no.
of
Stream
(Nu)
Bifurcation Ratio Stream Length (Km) Length Ratio Rb RI RHO
N1 N2 N3 N4 N5 N6 N1/N2 N2/N3 N3/N4 N4/N5 N5/N6 L1 L2 L3 L4 L5 L6 L2/L1 L3/L2 L4/L3 L5/L4 L6/L5
1 5 2 1 8 2.5 2 4.28 0.59 2.63 0.13 4.41 2.25 2.27 1.01
2 20 4 1 25 5 4 9.55 3.16 3.16 0.33 1.0 4.5 0.66 0.14
3 15 2 1
18 7.5 2
4.26 1.28 1.53
0.30 1.19
4.75 0.74 0.15
4 14 4 2
20 3.5 2
5.19 0.91 4.21
0.17 4.60
2.75 2.39 0.86
5 7 2 1
10 3.5 2
2.09 0.84 1.67
0.40 1.98
2.75 1.19 0.43
6 40 9 4
53 4.44 2.25
14.52 4.09 3.02
0.28 0.73
3.34 0.51 0.15
7 9 2 1
12 4.5 2
3.09 0.54 1.21
0.17 2.24
3.25 1.20 0.37
8 34 7 3 1
45 4.85 2.3 3
13.70 2.98 1.52 3.08
0.21 0.51 2.02
3.38 0.91 0.27
9 33 9 3 1
46 3.66 3 3
13.81 4.30 2.54 3.22
0.31 0.59 1.26
3.22 0.72 0.22
10 33 8 1
42 4.12 8
9.55 5.53 2.81
0.57 0.50
6.06 0.54 0.08
11 22 5 2 1
30 4.4 2.5 2
6.85 0.92 2.15 0.52
0.13 2.33 0.24
2.96 0.90 0.30
12 30 8 1
39 3.75 8
8.53 3.57 3.00
0.41 0.84
5.87 0.62 0.10
13 46 12 2 1
61 3.83 6 2
13.73 3.37 0.80 2.96
0.24 0.23 3.70
3.94 1.39 0.35
14 41 9 2 1
53 4.55 4.5 2
12.96 4.72 1.74 1.88
0.36 0.36 1.08
3.68 0.60 0.16
15 14 5 1
20 2.8 5
2.71 0.93 2.09
0.34 2.24
3.9 1.29 0.33
…Contd.
78
16 4 3 1
8 1.33 3
0.8
6 0.18
0.5
7
0.21 3.16
2.16 1.68 0.77
17 6 2 1
9 3.0 2 1.0
3 0.36
0.5
5
0.34 1.52
2.5 0.93 0.37
18 44 9 3 1
57 4.8 3 3 11.
93 3.59
1.31
1.21
0.30 0.36 0.92
3.6 0.52 0.14
19 26 5 2 1
34 5.2 2.5 2 6.4
9 1.88
2.0
6
0.1
4
0.29 1.09 0.06
3.23 0.48 0.14
20 7 2 1
10 3.5 2 2.9
6 0.92
0.62
0.31 0.66
2.75 0.49 0.17
21 7 2 1
10 3.5 2 3.2
7 0.76
0.6
9
0.23 0.90
2.75 0.57 0.20
22 11 3 1
15 3.6 3 4.3
8 1.40
1.92
0.31 1.37
3.3 0.84 0.25
23 12 2 1
15 6.0 2 5.5
2 1.54
1.0
5
0.27 0.68
4.0 0.48 0.12
24 13 3 1
17 4.33 3 6.4
4 2.42
1.76
0.37 0.72
3.66 0.55 0.15
25 8 2 1
11 4.0 2 5.2
0 1.01
0.9
7
0.19 0.95
3.0 0.57 0.19
26 31 7 1
39 4.42 7 13.
81 5.46
2.22
0.39 0.40
5.71 0.40 0.07
27 30 7 1
38 4.28 7 16.
72 2.28
4.1
7
0.13 1.82
5.64 0.98 0.17
28 20 4 1
25 5.0 4 8.6
4 2.94
2.98
0.34 1.01
4.5 0.67 0.15
29 85 24 3 1
113 3.54 8 3 37.
85 8.31
6.9
6
3.7
3
0.21 0.83 0.53
4.84 0.53 0.10
30 50 13 1
64 3.84 13 22.
13 6.48
4.64
0.29 0.71
8.42 0.50 0.05
31 36 7 1
44 5.14 7 14.
46 3.72
3.9
3
0.25 1.05
6.07 0.65 0.10
…Contd.
79
32 22 5 1
28 4.4 5 9.4
1 2.43
3.7
1
0.25 1.53
4.70 0.89 0.19
33 23 6 2 1
32 3.83 3 2 10.
58 2.61
1.19
2.10
0.24 0.45 1.76
2.94 0.82 0.27
34 9 2 1
12 4.5 2 3.0
6 2.57
0.5
6
0.83 0.21
3.25 0.52 0.16
35 62 12 3 1
78 5.16 4 3 29.
03 10.94
2.80
3.40
0.37 0.25 1.21
4.05 0.61 0.15
36 35 7 2 1
45 5.0 3.5 2 14.
70 4.71
4.4
7
0.5
4
0.32 0.94 0.12
3.50 0.46 0.13
37 13 3 1
17 4.33 3 5.1
6 1.10
1.53
0.21 1.38
3.66 0.80 0.28
38 22
4 44 12 2
283 5.09 3.66 6 2
113
.54
22.8
5
15.
46
16.
12
1.3
5
0.20 0.67 1.04 0.08
4.18 0.50 0.11
39 59 14 3 1 77 4.21 4.66 3 31.66
7.31 7.81
3.04
0.23 1.06 0.38 3.95 0.56 0.14
40 19 3 1 23 6.33 3 8.9
3 2.35
1.8
6 0.26 0.79 4.66 0.52 0.11
41 5 2 1 8 2.5 2 1.9
7 0.97
0.3
6 0.49 0.37 2.25 0.43 0.19
42 75 14 3 1 93 5.35 4.66 3 31.
88 8.28
7.0
5
1.1
3 0.25 0.85 0.16 4.33 0.42 0.09
43 567
128 28 7 3 1 734 4.42 4.57 4 2.33 3 267.31
83.96
47.47
10.8
20.94
13.83
0.31 0.56 0.22 1.93 0.66 3.66 0.74 0.20
44 65 12 3 1 81 5.41 4 3 39.
20
10.4
8
6.1
4
3.0
3 0.26 0.58 0.49 4.13 0.44 0.10
45 40 10 2 1 44 4.0 5 2 21.54
5.51 4.71
1.52
0.25 0.85 0.32 3.66 0.47 0.13
46 13 2 1 16 6.5 2 5.0
5 2.38
0.9
7 0.47 0.40 4.25 0.43 0.10
47 14 3 1 18 4.66 3 4.9
9 1.19
1.2
6 0.23 1.05 3.83 0.64 0.16
48 32 9 3 1 45 3.55 3 3 9.7
8 3.77
2.3
1
0.8
4 0.38 0.61 0.36 3.18 0.45 0.14
…Contd.
80
49 21
9 50 12 3 1 285 4.38 4.16 4 3
66.
13
17.2
0
8.1
4
4.1
0
5.3
1 0.26 0.47 0.50 1.29 3.88 0.63 0.16
50 12 3 1 16 4.0 3 3.72
1.08 0.97
0.29 0.89 3.50 0.59 0.16
51 7 3 1 11 2.33 3 2.1
2 0.39
0.7
3 0.18 1.84 2.66 1.01 0.38
52 955
203 50 13 3 1 1225 4.70 4.06 3.84 4.33 3 385.24
106.26
54.88
35.83
11.43
17.10
0.27 0.51 0.65 0.31 1.49 3.98 0.65 0.16
53 7 2 1 10 3.5 2 1.7
1 0.34
0.5
7 0.19 1.68 2.75 0.94 0.34
54 14 5 2 1 22 2.8 2.5 2 3.98
1.32 0.84
0.63
0.33 0.63 0.75 2.43 0.57 0.23
55 8 3 1 12 2.66 3 2.3
7 1.66
0.7
1 0.70 0.42 2.83 0.56 0.19
56 16 3 1 20 5.33 3 3.35
1.45 1.23
0.43 0.84 4.16 0.64 0.15
57 29 5 1 35 5.80 5 10.
86 4.40
1.3
3 0.40 0.30 5.40 0.35 0.06
58 36 7 2 1 46 5.14 3.5 2 11.
72 3.87
1.3
2
0.8
7 0.33 0.34 0.65 3.54 0.44 0.12
59 59
7 133 28 7 4 1 770 4.48 4.75 4 1.75 4
183
.20
61.1
5
28.
34
16.
52
9.4
5 4.01 0.33 0.46 0.58 0.57 0.42 3.79 0.47 0.12
60 9 2 1 12 4.50 2.0 2.31
0.33 0.83
0.14 2.52 3.25 1.33 0.40
61 43 11 3 1 58 3.90 3.66 3 14.
74 4.80
1.6
7
2.0
4 0.32 0.34 1.22 3.52 0.63 0.17
62 8 3 1 12 2.66 3.0 1.54
1.10 1.10
0.71 0.99 2.83 0.85 0.30
63 6 2 1 9 3.0 2.0 2.1
1 1.21
0.6
4 0.57 0.53 2.50 0.55 0.22
64 9 3 1 13 3.0 3.0 1.5
8 0.66
0.9
3 0.41 1.40 3.0 0.91 0.30
65 15 4 1 20 3.75 4.0 3.2
7 1.37
1.6
2 0.418 1.18 3.87 0.80 0.20
81
Table 5.2: Linear parameters of the Lohawati river basin, Kumaun Lesser Himalaya, Uttarakhand (after Agarwal et al. 2012).
Sub
-
basi
n.
no.
Stream order Total
no. of
Strea
m
(Nu)
Bifurcation Ratio Stream Length (Km) Length Ratio
Rb Rl RHO
N1 N2 N
3
N
4
N
5
N
6 N7
N1/
N2
N2/
N3
N
3/
N
4
N
4/
N
5
N
5/
N
6
N
6/
N
7
L1 L2 L3 L4 L5 L6 L
7
L2/L
1
L3/L
2
L4/L
3
L5/L
4
L6/L
5
L7/L
6
1 19 4 1 24 4.75 4 12.69 3.90 2.57 0.30 0.65 4.37 0.48 0.11
2 23 6 2 1 32 3.83 3 2 13.67 5.47 3.96 1.08 0.40 0.72 0.27 2.94 0.46 0.15
3 25 7 1 33 3.57 7 15.75 4.27 3.50 0.27 0.81 5.28 0.54 0.10
4 9 1 1 11 9 1 5.16 0.77 1.21 0.15 1.55 5 0.85 0.17
5 28 6 2 1 37 4.66 3 2 13.17 5.34 2.34 1.94 0.40 0.43 0.82 3.22 0.55 0.17
6 14 1 1 16 14 1 9.34 3.05 0.41 0.32 0.13 7.5 0.23 0.03
7 34 8 1 43 4.25 8 20.53 7.19 3.32 0.35 0.46 6.12 0.40 0.06
8 161 31 8 2 1 203 5.19 3.87 4 2 82.77 23.95 8.94 8.08 4.35 0.28 0.37 0.90 0.53 4.35 0.52 0.12
9 26 6 3 1 36 4.33 2 3 13.23 4.33 1.08 2.93 0.32 0.25 2.70 3.11 3.28 1.05
10 76 12 3 1 92 6.33 4 3 31.89 8.13 8.30 1.95 0.25 1.02 0.23 4.44 0.50 0.11
11 42 11 4 2 1 60 3.81 2.75 2 2 20.84 8.47 4.93 1.55 0.90 0.40 0.58 0.31 0.58 2.64 0.47 0.17
12 9 3 1 13 3 3 3.99 0.98 1.64 0.24 1.66 3 0.95 0.31
13 11 5 1 17 2.2 5 5.84 1.96 1.58 0.33 0.80 3.6 0.57 0.15
14 28 4 2 1 35 7 2 2 13.58 5.87 0.86 1.46 0.43 0.14 1.68 3.66 0.75 0.20
15 26 5 1 32 5.2 5 9.99 5.12 2.35 0.51 0.45 5.1 0.48 0.09
16 8 2 1 11 4 2 3.55 1.86 0.63 0.52 0.34 3 0.43 0.14
17 5 2 1 8 2.5 2 2.32 0.33 0.39 0.14 1.17 2.25 0.65 0.29
18 11 2 1 14 5.5 2 5.64 1.62 1.30 0.28 0.80 3.75 0.54 0.14
19 8 2 1 11 4 2 4.73 0.61 1.35 0.12 2.21 2 1.17 0.58
20R 187 29 1 1 218 6.44 1 115.5
4 22.41 8.75
31.1
6 0.19 3.56 6.44 1.87 0.29
82
c) Stream Length Ratio (Rl)
Stream Length ratio (Rl) may be defined as the ratio of the mean length of the
one order to the next lower order of stream segment (Horton 1945) and have been
computed as,
Rl = Lu / Lu-1
Where Rl = Stream length ratio
Lu = stream length of order u
Lu-1 = stream segment length of next lower order
The mean stream length ratio of the Ladhiya and Lohawati River Basin is 0.76
and 0.78 respectively. The Rl between streams of different order in the study area
reveals that the Rl for sub-basins varies between 0.35 – 2.39 (Ladhiya River basin)
and 0.23 – 1.87 (Lohawati River basin) (Table 5.1 and 5.2). It seems that the Rl
between successive stream orders varies due to difference in slope and topographic
conditions, and has an important relationship with the surface flow discharge and
erosional stage of the basin (Sreedevi et al. 2005).
d) Bifurcation ratio (Rb)
The ratio of number of streams of a given order (Nu) to the number of
segment of the higher order (Nu+1) is termed as Bifurcation ratio (Rb) (Horton 1945,
Strahler 1964) and computed as,
Rb = Nu / Nu+1
Strahler (1957) demonstrated that Rb shows only a small variation for different
regions on different environment except where powerful geological control dominates.
83
The present study shows that the Ladhiya and Lohawati river basins have the
mean Rb value of 3.74 and 4.08 respectively, while for the sub-basins it varies from
8.42 to 2.16 (Ladhiya River basin) and 6.44 to 2.0 (Lohawati river basin) (Table 5.1
and 5.2).
e) RHO Coefficient (RHO)
RHO coefficient is the ratio between the stream length ratio (Rl) and the
bifurcation ratio (Rb) (Horton, 1945),
RHO = Rl / Rb
It is considered to be an important parameter as it determines the relationship
between the drainage density and the physiographic development of the basin, and
allows the evaluation of the storage capacity of the drainage network (Horton 1945).
The mean RHO coefficient of the Ladhiya and Lohawati river basins is 0.23 and 0.22
respectively, while, the RHO of the sub-basins varies between 0.05 to 1.10 (Ladhiya
River basin) and 0.03 to 0.58 (Lohawati River basin) respectively (Table 5.1 and 5.2).
5.1.2 Areal Parameters
a) Area, Perimeter and Basin Length (L)
The Area is the entire area considered between the drainage divide line and the outfall
with all sub-basin and inter-basinal area. Perimeter is the total length of the drainage
basin boundary. The Ladhiya and Lohawati river basins covering an area (A) of about
746.83 km2 and 220.51 km
2 respectively and having a perimeter (P) of 159.74 km and
82.83 km respectively. In case of sub-basins of Ladhiya River basin the area ranges
from 159.27 km2 (sub-basin no. 52) to 0.27 km
2 (sub-basin no. 16) and for Lohawati
River basin the area ranges between 41.09 km2 (sub basin no. 8) to 0.95 km
2 (sub
84
basin no.17). Similarly, the perimeter for these sub-basins (Ladhiya River basin)
ranges between 62.77 km (sub-basin no. 43) to 2.50 km (sub-basin no. 17) and for the
sub basins of Lohawati the perimeter ranges between 31.35 km (sub-basin no. 8) to
4.07 km (sub-basin no. 17). The area and perimeter of all the sub-basins is given in
Table 5.3 and 5.4.
The basin length corresponds to the maximum length of the basin and sub-
basin measured parallel to the main drainage line (Mesa, 2006) and basin length is
obtained by measuring the longest basin diameter between the mouth of the basin and
most distinct point on the perimeter (Gregory and Walling, 1973). The main basin
length for Ladhiya and Lohawati River basins is 60.97 km and 28.95 km respectively
and the basin lengths of all sub-basins are shown in the Table 5.3 and 5.4.
Table 5.3: Areal parameters of the Ladhiya river basin, Kumaun Lesser Himalaya,
Uttarakhand (after Agarwal et al. 2012).
…Contd.
Sub- basin
No.
Area
A
(Km2)
Total stream
length
(Lt. in Km)
Stream
frequency
Fs=∑Nu /A
(Km-2)
Drainage
density
Dd=∑Lt/A
(Km-1)
Texture
T=Dd . Fs
(Km-3)
Basin
Length
(Km.)
Perimeter
(km)
1 1.88 7.52 4.32 3.98 17.24 3.79 8.46
2 5.31 15.89 4.70 2.99 14.09 4.10 10.57
3 2.04 7.07 8.79 3.45 30.39 3.02 6.93
4 2.66 10.32 7.51 3.88 29.18 2.92 7.69
5 1.21 4.60 8.25 3.80 31.41 2.59 6.13
6 7.47 21.63 7.09 2.89 20.53 4.96 13.28
7 1.37 4.84 8.75 3.53 30.98 1.96 4.93
8 5.42 21.29 8.29 3.92 32.59 4.30 11.17
9 6.91 23.89 6.65 3.45 22.99 5.21 12.73
10 4.41 17.91 9.51 4.05 38.56 3.39 9.27
11 1.82 10.45 16.48 5.74 94.71 2.71 6.43
12 3.12 15.11 12.48 4.83 60.36 3.30 8.46
13 3.71 20.87 16.41 5.61 92.25 3.91 10.62
14 4.15 21.32 12.77 5.13 65.60 3.95 10.36
15 1.09 5.73 18.19 5.22 95.02 2.53 6.06
16 0.27 1.62 29.41 5.97 175.78 1.12 2.72
85
17 0.29 1.94 31.03 6.70 208.02 1.04 2.50
18 2.83 18.06 20.10 6.37 128.06 2.40 7.48
19 1.94 10.58 17.44 5.43 94.75 1.58 5.62
20 1.18 4.52 8.43 3.81 32.13 1.73 4.97
21 1.23 4.73 8.10 3.83 31.05 1.88 5.04
22 2.39 7.70 6.26 3.22 20.18 2.63 7.30
23 2.13 8.12 7.03 3.81 26.82 2.93 7.16
24 3.02 10.63 5.62 3.52 19.81 2.82 6.63
25 2.17 7.19 5.05 3.30 16.69 2.11 6.45
26 5.99 21.50 6.51 3.59 23.37 3.15 10.61
27 6.82 23.18 5.57 3.39 18.93 4.47 11.46
28 4.33 14.58 5.76 3.36 19.37 5.11 11.57
29 13.80 56.87 8.18 4.12 33.72 5.09 15.98
30 7.07 33.26 9.05 4.70 42.57 4.51 12.06
31 5.37 22.12 8.18 4.11 33.65 4.39 11.09
32 3.70 15.56 7.56 4.20 31.81 4.20 9.80
33 4.25 16.49 7.51 3.87 29.12 3.91 9.80
34 1.57 6.19 7.60 3.92 29.86 2.43 5.64
35 13.19 46.17 5.91 3.50 20.68 4.78 16.60
36 7.24 24.44 6.21 3.37 20.96 5.34 13.00
37 1.76 7.79 9.65 4.43 42.78 2.25 5.66
38 41.31 169.34 6.85 4.09 28.07 9.23 33.63
39 12.85 49.84 5.99 3.87 23.22 6.98 16.12
40 3.71 13.15 6.18 3.54 21.90 2.96 8.15
41 0.60 3.30 13.22 5.45 72.15 1.20 3.52
42 11.57 48.36 8.03 4.17 33.54 4.82 14.48
43 125.89 444.34 5.83 3.52 20.57 13.56 62.77
44 19.17 58.86 4.22 3.07 12.96 5.63 19.37
45 10.89 33.3 4.03 3.05 12.33 4.42 13.88
46 2.42 8.41 6.61 3.47 22.99 2.81 6.80
47 1.77 7.45 10.16 4.21 42.79 1.97 5.96
48 3.87 16.72 11.60 4.31 50.03 3.59 9.72
49 19.38 100.90 14.70 5.20 76.52 8.25 20.74
50 1.07 5.77 14.92 5.38 80.38 1.93 4.66
51 0.45 3.25 24.28 7.18 174.56 1.03 3.38
52 159.27 610.76 7.69 3.83 29.48 19.49 62.41
53 0.37 2.63 27.02 7.12 192.62 1.24 2.86
54 1.05 6.78 20.85 6.43 134.18 1.89 4.71
55 0.83 4.74 14.45 5.71 82.67 1.75 4.44
56 1.23 6.05 16.24 4.91 79.84 2.03 5.41
57 3.06 16.60 11.42 5.42 61.94 2.42 7.39
58 3.28 17.80 13.99 5.41 75.72 2.23 7.80
59 75.45 302.70 10.20 4.01 40.93 9.52 38.41
60 0.61 3.48 19.51 5.66 110.43 1.39 3.47
61 4.24 23.25 13.67 5.48 74.94 3.14 10.73
62 0.72 3.75 16.62 5.19 86.34 1.83 4.90
63 0.68 3.97 13.17 5.82 76.74 1.82 4.49
64 0.44 3.17 29.14 7.12 207.55 1.28 3.46
65 0.93 6.27 21.43 6.72 144.24 1.97 5.16
86
Table 5.4: Areal parameters of the Lohawati river basin, Kumaun Lesser Himalaya,
Uttarakhand (after Agarwal et al. 2012).
b) Stream frequency (Fs)
Horton (1932) introduced the term stream frequency (Fs) or Channel frequency.
The stream frequency is the total number of stream segments of all orders per unit area,
and is calculated as,
Fs = ΣNu /A,
Where ΣNu =total number of stream segments of all orders,
A = area of the basin
The Stream frequency is related with permeability, infiltration capacity and relief
of a basin (Vijith and Satheesh, 2006). The Fs of Ladhiya and Lohawati river basin is
11.51 km-2
and 4.86 km-2
respectively, while the Fs for the sub-basins vary between 4.03
Sub-
basin
No.
Area
A
(Km2)
Total stream
length
(Lt. in Km)
Stream frequency
Fs=∑Nu /A
(Km-2)
Drainage density
Dd=∑Lt/A
(Km-1)
Drainage
Texture
T=Dd . Fs
(Km-3)
Basin Length
(Km.)
Perimeter
(km)
1 8.13 19.17 2.95 2.35 6.96 5.47 13.50
2 9.30 24.20 3.43 2.60 8.93 4.91 13.25
3 8.74 23.53 3.77 2.69 10.14 5.19 13.56
4 2.25 7.14 4.87 3.16 15.43 2.78 6.55
5 6.76 22.80 5.46 3.36 18.41 4.11 11.71
6 3.63 12.80 2.41 3.52 8.49 3.50 8.41
7 10.17 31.05 4.22 3.05 12.89 5.23 14.40
8 41.09 128.11 4.93 3.11 15.39 7.02 31.35
9 7.50 21.59 4.79 2.87 13.80 4.98 11.60
10 16.48 50.28 5.58 3.05 17.02 5.34 16.43
11 12.83 36.70 4.67 2.86 13.37 3.28 16.73
12 1.98 6.62 6.55 3.33 21.88 2.62 6.08
13 3.02 9.39 5.62 3.11 17.51 2.71 7.21
14 7.75 21.79 4.51 2.81 12.69 3.27 11.0
15 5.11 17.46 6.25 3.41 21.34 3.36 9.82
16 2.47 6.05 4.44 2.45 10.90 2.46 7.82
17 0.95 3.05 8.36 3.19 26.76 1.24 4.07
18 2.73 8.57 5.12 3.13 16.09 2.72 7.63
19 2.42 6.70 4.53 2.76 12.51 2.36 6.65
20R 177.87
87
to 29.41 (Ladhiya River basin) and 2.41 to 8.36 (Lohawati River basin) (Table 5.3 and
5.4). In the study area, the sub-basins having relatively higher Fs values are indicative of
relatively higher relief and lower infiltration capacity of the bed rock.
c) Drainage density (Dd)
Drainage density (Dd) is an expression to indicate the closeness of spacing of
channels within a basin (Horton, 1932). Dd is one of the important indicators of the
landform element as it provides a numerical measurement of landscape dissection and
runoff potential (Vijith and Satheesh, 2006). It is measured as the total length of streams of
all orders per unit area divided by the area of drainage basin and is calculated as,
Dd = Σ Lt /A,
Where Σ Lt = Total length of all the ordered streams,
A = Area of the basin
It is considered as a parameter determining the time of travel by water. It varies
between 0.55 and 2.09 km-1
in humid regions with an average density of 1.03 km-1
(Longbein, 1947). It is controlled by climate, lithology, relief, infiltration capacity,
vegetation cover, surface roughness and runoff intensity index. The amount and type of
precipitation influences directly the quantity and character of surface runoff. Low Dd
generally results in the areas of highly resistant or permeable subsoil material, dense
vegetation and low relief (Nag, 1998). High Dd is the resultant of weak or impermeable
subsurface material, sparse vegetation and mountainous relief. Low Dd leads to coarse
drainage texture while high Dd leads to fine drainage texture. Amount of vegetation and
rainfall absorption capacity of soils, which influences the rate of surface runoff, affects the
drainage texture of an area (Chopra et al. 2005). The mean Dd of Ladhiya and Lohawati
88
River Basin is 4.52 km-1
and 2.99 km-1
respectively, while the Dd of all the sub-basins is
given in Table 5.3 and 5.4.
d) Drainage Texture (T)
It is the total number of stream segments of all orders per perimeter of that area
(Horton, 1945). He recognized infiltration capacity as the single important factor which
influences drainage texture and considered the drainage texture (T) to include drainage
density and stream frequency. While, according to Smith (1950) drainage texture depends
upon a number of natural factors such as climate, rainfall, vegetation, rock and soil type,
infiltration capacity, relief and stage of development of a basin.
T= Dd X Fs
Where Dd = drainage density,
Fs = stream frequency
Based on the values of T, it is classified as (Smith, 1950):
Very Coarse (<2)
Coarse (2-4)
Moderate (4-6)
Fine (6-8)
Very Fine (>8)
Drainage texture of the Ladhiya and Lohawati river basins is 59.16 and 14.76
respectively. For the individual sub-basins „T‟ ranges from 12.33 to 207.55 (Ladhiya River
Basin) and 6.96 and 26.76 (Lohawati River Basin) (Table 5.3 and 5.4).
89
5.1.3 Shape Parameters
a) Elongation Ratio (Re)
Elongation ratio (Re) is the ratio between the diameter (D) of a circle of the same
area as the drainage basin and basin length (L) (Schumm, 1956), and is calculated as,
Re = D/L = 1.128 √A /L
Where, A = area of the basin
The values of elongation ratio vary from zero (highly elongated shape) to one
(circular shape). The Re of the Ladhiya and Lohawati River Basin is 0.16 and 0.17
respectively, indicates it to be elongated with high relief and steep slope. The value of Re
for the sub-basins is shown in Table 5.5 and 5.6.
b) Circulatory index (Rc)
The circulatory Ratio (Rc) has been used as a quantitative measure and is
expressed as the ratio of the basin area (A) to the area of a circle having the same
perimeter as the basin (Miller, 1953; Strahler, 1964) and is calculated as,
Rc = 4 π A/ P2
Where, A = area of the basin and
P = perimeter of the basin
The values of circularity index varies from zero (for a line) to unity i.e. one (for a
circle). The higher is the value of Rc, the more circular is the shape of the basin. The
circulatory ratio is influenced by length, frequency of streams (Fs), geological structures,
landcover, climate, relief and slope of the basin. It is a significant ratio, which indicates
90
the stage of the basin. Its low, medium and high values are indicative of the youth, mature
and old stages of the lifecycles of the tributary basins (Sreedevi et al. 2005). The Rc of the
Ladhiya and Lohawati River Basin is 0.56 and 0.64 respectively, while that of other sub-
basins is given in table 5.5 and 5.6.
Table 5.5: Areal parameters of the Ladhiya river basin, Kumaun Lesser Himalaya,
Uttarakhand (after Agarwal et al. 2012).
…Contd.
Sub-basin no.
Elongation Ratio
Re=1.128√A/L
Circularity index
Rc=4πA/P2
Form Factor
A/L2
1 0.20 0.33 0.13
2 0.16 0.59 0.31
3 0.23 0.53 0.22
4 0.18 0.56 0.31
5 0.27 0.40 0.17
6 0.14 0.53 0.30
7 0.27 0.70 0.35
8 0.12 0.54 0.29
9 0.12 0.53 0.25
10 0.13 0.64 0.38
11 0.22 0.55 0.24
12 0.13 0.54 0.28
13 0.10 0.41 0.24
14 0.11 0.48 0.26
15 0.20 0.37 0.17
16 0.36 0.46 0.21
17 0.31 0.58 0.26
18 0.10 0.63 0.49
19 0.15 0.77 0.77
20 0.27 0.60 0.39
21 0.26 0.61 0.34
22 0.23 0.56 0.34
23 0.20 0.52 0.24
24 0.18 0.86 0.37
25 0.23 0.65 0.48
26 0.13 0.66 0.60
27 0.13 0.65 0.34
28 0.16 0.40 0.16
29 0.07 0.67 0.53
30 0.09 0.61 0.34
31 0.12 0.54 0.27
32 0.14 0.48 0.20
33 0.14 0.55 0.27
34 0.23 0.62 0.26
35 0.09 0.60 0.57
36 0.12 0.53 0.25
91
Table 5.6: Areal parameters of the Lohawati river basin, Kumaun Lesser Himalaya,
Uttarakhand (after Agarwal et al. 2012).
…Contd.
37 0.19 0.68 0.34
38 0.04 0.45 0.48
39 0.08 0.62 0.26
40 0.16 0.70 0.42
41 0.26 0.61 0.41
42 0.07 0.69 0.49
43 0.03 0.40 0.68
44 0.08 0.64 0.60
45 0.11 0.70 0.55
46 0.21 0.65 0.30
47 0.20 0.62 0.45
48 0.13 0.51 0.29
49 0.05 0.56 0.28
50 0.20 0.61 0.28
51 0.23 0.49 0.42
52 0.02 0.51 0.41
53 0.26 0.59 0.23
54 0.17 0.59 0.29
55 0.22 0.52 0.27
56 0.21 0.52 0.29
57 0.12 0.70 0.52
58 0.11 0.67 0.66
59 0.11 0.64 0.83
60 0.25 0.63 0.31
61 0.09 0.46 0.42
62 0.25 0.37 0.21
63 0.23 0.42 0.20
64 0.23 0.46 0.27
65 0.17 0.43 0.23
Sub-basin no.
Elongation Ratio
Re=1.128√A/L
Circularity index
Rc=4πA/P2
Form Factor
A/L2
1 0.17 0.55 0.27
2 0.14 0.66 0.38
3 0.14 0.59 0.32
4 0.24 0.66 0.29
5 0.13 0.62 0.39
6 0.17 0.64 0.29
7 0.11 0.61 0.37
8 0.06 0.52 0.83
9 0.14 0.70 0.30
10 0.09 0.76 0.57
11 0.11 0.57 1.19
12 0.24 0.67 0.28
13 0.21 0.72 0.41
14 0.14 0.80 0.72
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c) Form factor (Ff)
The Ff of a drainage basin is expressed as a ratio between the area of the basin (A)
and the square of the basin length (L2) (Horton, 1945), and is computed as,
Ff = A / L2
The value of form factor is always less than 0.7854 (for a perfectly circular basin).
Smaller the value of form factor, more elongated is the basin. The basin with high Ff have
high peak flows of shorter duration, whereas elongated sub watershed with low form
factor have lower peak flow of longer duration (Chopra et al. 2005). The Ff of the Ladhiya
and Lohawati River Basin is 0.35 and 0.46 respectively, while the Ff of sub-basins is
given in table 5.5 and 5.6.
5.2 NEOTECTONICS
Neotectonics, a sub discipline of tectonics, involves the study of the motions and
deformations of the Earth's crust (geological and geomorphological processes) which are
current or recent in geologic time. The term neotectonics was first used by Vladimir
Oruchev in 1948 and he defined as "recent tectonic movements occurred in the upper part
of Tertiary (Neogene) and in the Quaternary, which played an essential role in the origin
of the contemporary topography".
Active tectonics broadly includes the ongoing deformation of the Earth‟s surface
(Wallace, 1985) and is defined as „those processes that produce deformation of the Earth‟s
crust on a time scale of significance to human society‟ (Keller and Pinter, 1996). The
15 0.15 0.66 0.45
16 0.29 0.50 0.40
17 0.36 0.72 0.61
18 0.22 0.58 0.36
19 0.26 0.68 0.43
93
topographic features, geological structures and recurrent seismicity of the Himalaya are a
consequence of the continued northward push and collision of the Indian Plate with
Eurasia (Quereshy et al. 1989). Due to the continuous northward movement of the Indian
Plate, the Himalayan mountain belt is still under the process of crustal adjustments. Such
adjustments are recorded in the form of neotectonic activity experienced in different
segments of the Himalaya and in turn are manifested in the form of distinct landforms
(Valdiya 1986; Bali et al. 2003; Agarwal et al. 2009; Agarwal and Sharma, 2011).
Several evidences of neotectonics such as active landslides, river terraces, vertical
down-cutting of the rivers, deep gorges of rivers, triangular facets and tilting of beds, have
been noticed in the various parts of the study area.
5.2.1 Neotectonic Features
a) Landslides
Like other parts of Himalaya the landslides are very common features observed in
the study area. In the Kumaun Sub-Himalayan region the landslides and slope failures are
the function of several intrinsic and extrinsic factors such as geological, structural,
hydrological, topographical, gravity, poor cementation, tectonic activity, large pore spaces
and mineral composition which may act alone or in combination of all the factors (Varnes,
1978; Olivera, 1993; Singh et al. 1994; Bell and Culshaw, 1993). The susceptibility of the
terrain to landsliding varies considerably depending upon number of factors such as
configuration of slopes, slope forming material, structural discontinuities, climatic factors
and myriad of triggering agents (Sharma et al., 1996).
Mass wasting in the form of major and minor slides along the Tanakpur-
Champawat route is very common. According to Agarwal & Sharma (2011) a total no. of
94
31 major and minor landslides has been observed out of which 16 are of debris type and
15 are rockslides. Most of landslides are present in the area have been found to be
structurally controlled (Fig. 5.2A-F).
Fig. 5.2: Photographs showing occurrence of landslide in the study area, (A) near Shyamlatal, (B)
near Shiala, (C) near Rela ka Khola, (D) near Chaundakot, (E) on way to Purnagiri near batna gad,
(F) on way to Purnagiri (near bridge).
95
b) River terraces
River terraces are bench-like features believed to represent formal valley flows and
flood plains (Keller and Pinter, 1996; Summerfield, 1991). River terraces are formed when
the erosional capacity of a river increases so that it cuts down through flood plain more
rapidly than the normal. When a river valley has been subjected to alternating phases of
aggradation and dissection, a series of terraces are developed and are formed on the both
side of the river. Paired terraces occur at times of elevation or when down cutting is
greater than lateral erosion (Kellar and Pinter, 1996), whereas the unpaired terraces (Fig.
5.3A-D) usually formed when lateral erosion dominates. Both paired (symmetrical as well
as asymmetrical) and unpaired terraces are present in the area suggesting that the rate of
Fig. 5.3: Field photographs (A-D) showing asymmetric river terraces in the Ladhiya River
Valley.
96
incision was rapid in comparison to lateral migration and the rate of uplift was more. The
asymmetrical terraces present in the area further suggest that the rates of movement on the
two sides of river valley were not uniform. At some places (Fig. 5.3 A) up to four terraces
have been observed (T0, T1, T2 & T3).
c) Triangular facets
Triangular facets may be defined as a physiographic feature having a broad base
and an apex pointing upward specifically the face on the end of a faceted spur, or,
triangular shaped steep sloped hill or cliff formed usually by the erosion of a fault
truncated hill (Summerfield, 1991). Presences of well developed triangular facets are a
signature of a fresh fault scarp. Therefore, the presence of triangular facets is believed to
be indicators of neotectonics. Triangular facets have been noticed at a no. of places (Fig.
5.4A & B).
Fig. 5.4: Field photographs (A & B) showing triangular facets at the left bank of Ladhiya River
Valley.
5.3 Lineament Analysis of the study area
A lineament is a pattern (Fig. 5.5) or "figure" in a factual representation
(photograph, map, model) of either the earth's surface or a subsurface datum (whether
stratigraphically, structurally, or geophysically defined) and the figure must be linear
(straight), continuous, reasonably well expressed (having discernible end points, width,
97
and azimuth), and be related to features of the solid earth. Figures are not lineaments by
this definition if they represent either cultural features such as pipeline corridors, roads, or
canals (Caran et al. 1981).
Fig. 5.5: Lineament pattern map of the Tanakpur-Champawat and adjoining areas, Kumaun Lesser
Himalaya.
98
Fig. 5.6: Rose diagram of the lineaments of the study area (n=155).
In the present work, features like ridges, straight segment of a river channel,
straight segment of streams and a river courses are identified and mapped to the direction
pattern of the lineament and their 155 azimuth were plotted to obtain the rose diagram.
Lineaments are marked on the satellite image data and their azimuths were noted by using
ERDAS imagine software. The IRS Resourceset-1, sensor LISS III has been used to
identify the lineaments. For this the different spectral bands were used to make false
colour composite (FCC) images. In the present study area Band 4 (Red), Band 3 (Green)
and Band 2 (Blue) are used to make FCC. The path 099 and row 051 of LISS III image of
24 m spatial resolution has been used for present study.
Rose diagram based on the lineaments direction gives the mean resultant direction
of the study area is NNE-SSW (004-184) (Fig. 5.6). The 155 azimuth datas were used to
plot the rose diagram with the help of GEOrient, version 9.5.0 software. The data
description of the rose diagram gives the sector angle 10o and approximately 95%
confidence interval.
99
5.4 Digital elevation model (DEM) and contour map of the study area
A digital elevation model represents the surface topography of any area with
respect to elevation in digital format. It is also called as digital terrain model (DTM), used
to record the topographical representation of the earth surface in digital number values
(DN). Its accuracy is depending upon the type of data that is primarily used for its
delineation. Vegetation, buildings and other man-made (artificial) features are removed
digitally - leaving just the underlying terrain. A Digital Elevation Model (DEM) is one of
the most useful sources of information for spatial modelling and monitoring, with
applications as diverse as environment and earth science, e.g. catchment dynamics;
landscape simulation (Pike et al. 2007). Shuttle Radar Topography Mission (SRTM) data
are used to make the DEM and contour map with the help of Arc GIS 10 software (Fig.
5.7 & 5.8). One of the most widely used DEM data sources is the elevation information
provided by the Shuttle Radar Topography Mission (SRTM) (Coltelli et al. 1996; Farr and
Kobrick, 2000; Gamache, 2004).
The general topography of the study area shows uneven and even surface
topography with flat or low terrain. Linear features are also noticed in the form of rivers
and gullies, Ladhiya river is the main river in the study area that flows in the SE direction
almost in the middle part of the study area and meet the Kali river. The Kali river
demarcates the western border of Nepal with India. The general trend of the Kali river is
SW direction in the study area but it abruptly changes its course towards NW at 60o and
then it takes turn at right angle and again it also takes sharp turn at right angle. This is due
to some tectonic activity, because it is closer to the South Almora Thrust (SAT) and Main
Boundary Thrust (MBT) zone. The different shades of colour in the digital elevation
model show the height variations in the study area. The highest elevation is varies from
100
1769 to 2198 m (white) and lowest elevation are ranges between 220 m and 354 m (Light
blue).
Contour map is a map showing elevations and surface configuration by means of
contour lines. The distribution of the contour lines in the study area shows how the surface
topography changes in the area. The contour map is developed with the help of SRTM
data using Arc GIS 10 software.
In the present study area the SW portion has gentle slope and the NW portion has
steeper slope it is due to farther and closeness of the contour lines. North of the
Sukhidhang the closeness of the contour line increased up to the northern part of the study
area. The lowest value of the contour line in the study area is 250 m and the highest value
of the contour line is 2150 m. The Tanakpur area is situated on the lower value of the
contour line and the Champawat is on the higher value of contour line in the study area.
Rivers and gullies are also showing lower contour values in the area.
5.5 Slope and Slope aspect map of the study area
The slope and slope aspect map is basically prepared on Shuttle Radar Topography
Mission (SRTM) data with the help of Arc GIS 10 software. The SRTM data is
downloaded from the Global Land Cover Facility (GLCF) and its resolution is 30 m.
The slope map studies of any region or area especially the hilly terrain are very helpful in
the interpretation of the steepness of the elevated terrains. In the present study area the
slope varies from less than 5o to a maximum of 55
o with different shades of colour (green,
yellow, red) (Fig. 5.9). The lowest slope angle is measured around the Tanakpur area that
is less than 5 degree in the southern part and the maximum slope angle is 55o which is
observed in the NE part of the study area. In general Northern part of the study area shows
high slope and the Southern part shows low angle. Sukhidhang, Chalthi, Swala and Dhaun
have intermediate slope angle and the Champawat varies 10 to 20 degree slope angle. The
101
presence of Himalayan Frontal Thrust (HFT) in the southern area makes the lowered slope
angle due to formation of foreland basin as this is the region where high sediments
accumulation takes place.
Slope aspect map identifies the slope direction (0-360) in compass degree
(0=North, 180=South, etc.). Flat areas having no down slope direction are given a value of
-1 (Fig. 5.10).
102
Fig. 5.7: Digital elevation model (DEM) of Tanakpur-Champawat and adjoining areas, Kumaun
Lesser Himalaya.
103
Fig. 5.8: Contour map of Tanakpur-Champawat and adjoining areas, Kumaun Lesser Himalaya.
104
Fig. 5.9: Slope analysis map of Tanakpur-Champawat and adjoining areas, Kumaun Lesser
Himalaya.
105
Fig. 5.10: Slope aspect map of Tanakpur-Champawat and adjoining areas, Kumaun Lesser
Himalaya.
106
Chapter 6
HILL SLOPE INSTABILITY
Introduction
Hill slope instability is a major problem of mountainous terrain. Landslides are the
very common phenomena in the geodynamically active terrain of the Himalaya. The
Himalaya, being the youngest and one of the most dynamic mountain chains is still in
a tectonically active state and to attain equilibrium is undergoing massive degradation
and mass wasting processes. Landslides are major natural hazards in Himalayan
terrain. Susceptibility of the terrain to landsliding varies considerable depending upon
number of factors such as configuration of slopes, slope forming material, structural
discontinuities, climatic factors and myriad of triggering agents (Sharma et al.1996).
The landslides and slope failures in the Kumaun Sub-Himalayan region are function
of several intrinsic and extrinsic factors such as geological, structural, hydrological,
topographical, gravity, poor cementation, tectonic activity, large pore space and
mineral composition which may act alone or in combination of all the factors (Varnes,
1978; Olivera, 1993; Singh et al. 1994; Bell and Culshaw, 1993). Their magnitude
and frequency, however, are a cause of concern where these interfere with human
interest, causing immense loss to human life, infrastructure and natural resources
(Paul et al. 2000). A spatial and temporal analysis of the threat of landslide is difficult
to determine accurately because of variable factors responsible for their occurrences
and areas exposed for risk (Sharma, 2008). The Northeastern Kumaun Himalaya in
general is highly prone to seismotectonic activities (Verma et al., 1977) comes under
seismic zone-IV (Vulnerability atlas of India, 1997). The neo-tectonic activity in the
107
area is well documented by the occurrence of a number of seismic events in the recent
years, including the Uttarkashi earthquake of 1991 & the Chamoli earthquake of 1999
(Rajendra et al. 2000).
The main reasons for increasing landslide disasters are over exploitation of
natural resources, deforestation, and greater vulnerability of the exposed population as
a result of growing urbanization and uncontrolled land-use pattern. On global scale
landslides causes major disaster every year and the frequency of their occurrence is
also rises. Every year uninhabited areas are being utilized for development purposes,
it makes slope more vulnerable to landslide hazards. Increase in road extensions and
widening activities along the roads, lack of proper and timely slope treatments, result
in the development of overhangs, thus making them more susceptible to instability.
6.1 Landslides in the study area
Landslides are very common in the study area. The Tanakpur-Champawat area
is a shrine of famous Purnagiri (Puniagiri) temple where thousands of people visit
every year. The present study investigated the landslides around the study area. This
study is of social importance and would also help in locating safer sites for
constructions.
The Bhabhar Formation, Siwalik Group, Bhimtal Quartzites and Almora
Crystallines are exposed from South to North traverse. These geological formations
are controlled by three major tectonic planes viz. Himalayan Frontal Thrust (HFT),
Main Boundary Thrust (MBT) and South Almora Thrust (SAT). Out of the entire
Himalayan terrain, the outer Himalaya is believed to show excellent signatures of
active tectonics. The Main Boundary Thrust (MBT) that separates the Outer and
108
Lesser Himalaya has a recorded history of tectonic activity in the recent past (Bali et
al. 2009). In such geo-tectonic setting, a high relief terrain traversed by active tectonic
and deformation features such as folds, faults, and shear zones become the loci for
pulverized and fractured rock mass and become highly susceptible to slope instability.
The rocks belonging to Siwalik Group comprises of alternate sequence of sandstone,
siltstone and shale which are exposed up to Sukhidhang. The slope of Siwalik hills
varies from place to place and shows moderate to steep slope (240-68
0), however most
of the landslides in Siwalik range show steep slope 600-70
0 (Kothyari et al. 2012). A
landslide scatter map of the study area (Fig.6.1) is prepared with the help of ISRO-
LISS-III data and ARC GIS-10 software to find out the position and density of a
landslide in the area. The landslide scatter map shows that the middle part of the area
around Sukhidhang and Chalthi is more vulnearable.
Fig. 6.1: Landslide scatter map of the study area.
109
6.2 Landslides vis a vis structural control
The study is based on the landslide zones recorded in the proximity of thrust
zones and detailed examination of three major landslides, studied along the Main
Boundary Thrust (MBF) zone and the Himalayan Frontal Thrust (HFT) zone which
causes many problems to the local inhabitants. Details of peripheral area and
perimeter of all major and minor slides have been collected and data plotted (Fig. 6.2)
in the graph. The A-B line shows the percent change in the periphery of active slide
zones. The data indicate near linear change in the peripheral area of active landslides
with respect to time; whereas the change in the peripheral area of active landslides
away from the thrust zones , as depicted by C-D line is minimal. This indicates that
Fig. 6.2: Graph showing year-wise changes in periphery of landslide (after Prakash et al.
2014).
structural control of landslide activity and/or may be corroborated with that of the
neotectonism along the thrust zones. The distribution as related to distance from
major shear zones have also been observed in Ramganga catchments (Joshi and
Gupta,1989) where maximum number of landslide events (33%) occur within a
110
distance of about 1 km from the tectonic contacts. Away from the tectonic zones, the
percent number of landslide activity gradually decreases.
In addition to the distribution of landslide, three major landslides have also
been studied to analyse the structural control on the landslide periphery and area of
active zone.
6.2.1 Landslide near Shiala village (Shyamlatal Gramsabha), Sukhidhang
One of the biggest landslides of the study area located at Shyamlatal
gramsabha near Shiala village (N 29010’2.6” E 80
007’53.2”) (Fig. 6.3A) which
expanded about 3.00 km in length & 2.00 km in width. In 2006, the perimeter of this
landslide was 8.69 km and covered an area about 1.72 sq km whereas in 2011 it
increases its perimeter and area about 11.48 km and 1.81 sq km respectively. Mainly,
the debris material of this landslide is belongs to Siwalik Group. Due to this landslide
a long narrow shear crack is developed along the present water tank and caused it
subsidence. Houses are also damaged in the area. Water tank are also severely
affected by this landslide (Fig. 6.3B).
Fig. 6.3: Field Photographs showing (A) landslide crown, near Shiala village (shyamlatal
gramsabha), (B) cracks developed along the water tank at the Shiala village (after Prakash et
al. 2014).
111
6.2.2 Batna Gad landslide
The Batna gad landslide is located at lat. N 29o
09’ 05” and long. E 80o
08’
30”, it is also an active landslide (Fig. 6.4A). Its length and width is about 1.00 km
and 0.77 km. In 2006, its area and perimeter was about 0.40 sq km and 2.47 km
respectively. In 2011, it expands his area and perimeter is about 0.50 sq km and 2.83
km respectively. During monsoon of 2010, a huge amount of materials (boulders and
debris) are derived from this landslide, blocked the famous Purnagiri (Puniagiri) road
(Fig. 6.4B). The distance of the road from the landslide is approximately 3.16 km.
Fig. 6.4: Field Photographs showing (A) batna gad landslide near the highway of Purnagiri
(Puniagiri) temple, (B) a huge amount of rock material is derived from the batna gad landslide
which blocked the highway on the way to Purnagiri (Puniagiri) temple (after Prakash et al.
2014).
6.2.3 Chaundakot Landslide
Chaundakot landslide is located at N 29010’17” E 80
004’32” near Chaundakot
village (Fig. 6.5A & B). In 2006, the perimeter and area of landslide were about 2.20
km and 0.28 sq km respectively. This landslide is also an active stage and
continuously increasing his area and perimeter. In 2011, it covers the area about 0.39
sq km and perimeter is 2.85 km.
112
Fig. 6.5: Field Photographs showing (A) landslide near chaundakot village, (B) cracks
developed on the wall of the house due to landslide near chaundakot village (after Prakash et
al. 2014).
6.3 Landslides along Tanakpur-Champawat highway
A detailed study of landslides is carried out along the Tanakpur-Champawat
highway (Fig. 6.6A-D). It is affecting the social life of the villagers, damaging the
road network and also affecting the human life.
Fig. 6.6: Field Photographs (A-D) showing landslide along Tanakpur-Champawat highway.
113
About 18 slides are observed in which most are debris type and rock fall, their
morphological and geological details are given below:
114
Table 6.1: Landslide along Tanakpur-Champawat National highway: Kumaun Lesser Himalaya, Uttarakhand.
Sl.
No.
Location Morphometrical details Geological details Type of
slide
Remarks
(Causative
factor) Length
(m)
Height
(m)
Slope
angle/direction
Geological
formation/grou
p
Lithology Structural
details strike
dip/
1. 29o 08’ 07.8”
80o 05’ 12.5”
12 km before
Sukhidhang
08 15 60o/W45
oN Siwalik Group Sandstone,
Siltstone,
clay
- Debris slide Slide of
road due to
rain
2. 29o 08’ 17.7”
80o 05’ 40.1”
11 km before
Sukhidhang
60 20 55o/S30
oE Siwalik Group Sandstone,
Siltstone,
clay
- Debris slide Due to road
widening
3. 29o 08’ 17.8”
80o 05’ 40.5”
11 km before
Sukhidhang
28 22 52o/S55
oE Siwalik Group Sandstone,
Siltstone,
clay
- Debris slide Due to road
widening
4. 29o 08’ 18.5”
80o 05’ 30.8”
8.5 km before
Sukhidhang
16 26 58o/E25
oS Siwalik Group Sandstone,
Siltstone,
clay
- Debris slide Slide of
road due to
rain
5. 29o 08’ 29.9”
80o 05’ 31.8”
08 km before
Sukhidhang
23 35 60o/E20
oS Siwalik Group Sandstone,
Siltstone,
clay
- Debris slide Due to road
widening
…Contd.
115
6. 29o 08’ 39.3”
80o 05’ 33.7”
7.5 km before
Sukhidhang
18 25 48o/East Siwalik Group Sandstone,
Siltstone,
Shale and
clay
- Debris slide Due to road
widening
7. 29o 08’ 23.3”
80o 05’ 26.4”
7 km before
Sukhidhang
08 18 62o/SE Siwalik Group Sandstone,
Siltstone and
clay
- Debris slide Slide of
road due to
rain
8. 29o 08’ 17.2”
80o 05’ 13.5”
6.5 km before
Sukhidhang
21 28 45o/S70
oE Siwalik Group Sandstone,
Siltstone and
clay
- Debris slide Due to road
widening
9. 29o 08’ 20.2”
80o 05’ 16.7”
6 km before
Sukhidhang
15 21 55o/S65
oE Siwalik Group Sandstone,
Siltstone,
clay
- Debris slide Slide of
road due to
rain
10. 29o 11’ 19.4”
80o 05’ 32.5”
4 km before Chalthi
58 42 58o/SE Bhimtal
formatiom
Sheared
Quartizite
with schist
No preferred
orientation
Debris cum
rock slide
Due to
thrust zone
11. 29o 11’ 11.6”
80o 05’ 27.6”
3 km before Chalthi
18 26 46o/E10
oS Bhimtal
formatiom
Sheared
Quartizite
with schist
No preferred
orientation Debris cum
rock slide
Due to
thrust zone
12. 29o 11’ 31.5”
80o 05’ 20.2”
2 km before Chalthi
21 31 48o/N38
oE Bhimtal
formatiom
Sheared
Quartizite
with schist
No preferred
orientation Debris cum
rock slide
Due to
thrust zone
and road
widening
…Contd.
116
13. 29o 11’ 51.0”
80o 05’ 39.9”
Left bank of Chalthi
bridge
60 40 56o/S46
oE Almora
Crystalline
Group
Highly
sheared and
jointed
Quartzite
42o-222
o
55o/132
o
Rock fall Intense
fracturing
due to thrust
zone
14. 29o 11’ 47.4”
80o 05’ 31.8”
39 km before
Champawat
48 60 42o/SE Almora
Crystalline
Group
Sheared
Quartizite
with
Phyllite
No preferred
orientation
Debris cum
rock slide
Due to
thrust zone
and road
widening
15. 29o 12.5’ 1.2”
80o 03’ 12.3”
20 km before
Champawat
250 80 48o/N53
oW Almora
Crystalline
Group
Schist No preferred
orientation
Debris slide Due to road
widening
16. 29o 12’ 0.5”
80o 04’ 59.8”
7.5 km before
Amori
13 18 42o/W32
oS Almora
Crystalline
Group
Quartzite 0o-180
o
75o/090
o
Rock fall Highly
fractured
and sheared
rock
17. 29o 15’ 35.5”
80o 05’ 33.7”
10 km before
Champawat
8 16 58o/W26
oN Almora
Crystalline
Group
Mylonite 252o-72
o
76o/342
o
Rock slide Toe cutting
from nala
18. 29o 17’ 22.1”
80o 05’ 44.2”
7.5 km before
Champawat
16 21 62o/S45
oE Almora
Crystalline
Group
Mylonite 240o-60
o
36o/330
o
Rock slide Due to
widening of
road
117
6.4 Landslide hazard zonation model
Landslide hazard zonation model is not a landslide hazard zonation mapping
of an area; it is a simple model or method to find out the landslide density or
percentage of landslide hazards which have been already occurred in a particular area
or in a given area on the basis of present landslides, where as the landslide hazard
zonation mapping is a macrozonation approach showing the probabilities of landslide
hazards in an area (Anbalagan 1992). Macro-zonation depicts spatial assessment of
landslide hazards of varying degree based on the estimated significance of the
causative factors of instability (Sharma, 2008). This method helps to find out the safer
zones or safer sites which are not affected by landslide and it is used for future
developmental planning but field visit is also essential to verify the ground truth and
data.
To follow this method, first made the scatter map of the study area with the
help of Liss III data and Arc GIS 10 software and then the whole area is divided into
2.5 km X 2.5 km grid. The 2.5 km X 2.5 km grid covers 6.25 sq km of the study area
(Fig. 6.7). If one grid is calculated as 100 percent then we find out the landslide
affected areas in percentage. Grid wise landslide affected areas are given in table 6.2.
118
Fig. 6.7: Map showing grid wise (2.5 km X 2.5 km) distribution of landslides.
Table 6.2: Grid wise landslide affected areas in percentage and in km2.
Grid
No.
Landslide affected
areas (in
percentage)
Landslide affected
areas (in Sq km)
1 0 0
2 1 .062
3 .5 .031
4 0 0
5 0 0
6 0 0
7 0 0
8 3 .186
9 .5 .031
10 0 0
…Contd.
119
11 0 0
12 0 0
13 0 0
14 1 .062
15 1.5 .093
16 0 0
17 2 .124
18 1.5 .093
19 3 .186
20 .5 .031
21 5 .31
22 0 0
23 .5 .031
24 0 0
25 .5 .031
26 .5 .031
27 0 0
28 0 0
29 1 .062
30 .5 .031
31 9 .558
32 5 .31
33 1 .062
34 .5 .031
35 .5 .031
36 0 0
37 0 0
38 0 0
39 0 0
40 5.5 .341
41 0 0
42 2.5 .155
43 0 0
44 0 0
45 2.5 .155
46 0 0
47 0 0
…Contd.
120
48 0 0
49 0 0
50 0 0
51 .5 .031
52 2.5 .155
53 5.5 .341
54 1 .062
55 15 .93
56 6 .372
57 1.5 .093
58 0 0
59 0 0
60 0 0
61 0 0
62 0 0
63 0 0
64 0 0
65 .5 .031
66 6 .372
67 8 .496
68 15 .93
69 9 .558
70 3.5 .217
71 1.5 .093
72 0 0
73 3 .186
74 0 0
75 1 .062
76 0 0
77 0 0
78 1.5 .093
79 1 .062
80 0 0
81 0 0
82 2 .124
83 0 0
…Contd.
121
84 0 0
85 3 .186
86 0 0
87 0 0
88 3.5 .217
89 15 .93
90 3 .186
91 4 .248
92 2 .124
93 3.5 .217
94 2 .124
95 4.5 .279
96 .5 .031
97 2 .124
98 .5 .031
99 0 0
100 0 0
101 8 .496
102 1.5 .093
103 1 .062
104 2 .124
105 0 0
106 0 0
107 1 .062
108 2.5 .155
109 0 0
110 4 .248
111 1 .062
112 0 0
113 2.5 .155
114 0 0
115 0 0
116 3 .186
117 2 .124
118 1.5 .093
119 2 .124
…Contd.
122
120 0 0
121 0 0
Grid wise distribution of landslide map shows that those areas which lie in grid
numbers 1, 4, 5, 6, 10, 11, 13, 16, 22, 24, 27, 28, 36, 37, 38, 39, 41, 43, 44, 46, 47, 48,
49, 50, 58, 59, 60, 61, 62, 63, 64, 72, 74, 76, 77, 80, 81, 83, 84, 86, 87, 99, 100, 105,
106, 109, 114, 115, 120 and 121 are not affected by landslides and those which lie in
grid numbers 3, 9, 20, 23, 25, 26, 30, 34, 35, 51, 65, 96 and 98 are the least affected
areas that is about .5 percent or .031 sq km in a one grid. The maximum landslide
affected area in a one grid is about 15 percent or .93 sq km. which falls in grid
numbers 55, 68 and 89.
If the study area is divided into 5 km X 5 km i.e. 25 sq km to make 31 zones
(Fig. 6.8) or sector of whole area then it is found that the zone 16 which is near
Sukhidhang is more affected to landslide i.e. about 44 percent or 2.728 sq km. The
least affected zone is 6 and 12 west of Tanakpur and the zone 13, 18 and 31 are not
affected by landslide which is near Tanakpur, Champawat and NE of Shim village.
The data are presented in table 6.3.
123
Fig. 6.8: Map showing zone wise (5 km X 5 km) distribution of landslides.
Table 6.3: Zone wise landslide affected areas in percentage and in km2.
Zone
No.
Landslide affected
areas (in
percentage)
Landslide affected
areas (in Sq km)
1 2 .124
2 2 .124
3 3.5 .217
4 6.5 .403
5 5.5 .341
6 .5 .031
7 1 .062
8 5.5 .341
…Contd.
124
9 4 .248
10 14 .868
11 4 .248
12 .5 .031
13 0 0
14 3 .186
15 13 .806
16 44 2.728
17 15 .93
18 0 0
19 3.5 .217
20 3 .186
21 4 .248
22 5 .31
23 16 .992
24 15 .93
25 8 .496
26 8.5 .527
27 3.5 .217
28 3 .186
29 10 .62
30 6 .372
31 0 0
125
Chapter 7
DISCUSSION AND CONCLUSIONS
The present chapter gives the results of the detailed study of the Tanakpur-
Champawat area. Three thrusts are exposed in the study area i.e. Himalayan Frontal
Thrust (HFT), Main Boundry Thrust (MBT) and South Almora Thrust (SAT).
The major geomorphological features of the area are ridges, steep valleys,
rivers, and rivulets, locally known as Gads and Nalas. The Siwalik rocks continue
laterally throughout the southeastern part of the Kumaun Lesser Himalaya bounded
between Himalayan Frontal Thrust in the south and Main Boundary Thrust in the
north. The Siwalik foothill belt consists of normal sections of northwards dipping
beds without repetitions, inversions or imbrications. Locally, faults are responsible for
a sudden change in dip, without, however, cutting out much of the section. The lowest
southernmost outcrops near Bastia consist of soft and friable brownish to purplish fine
grained sandstones, which indicate oxidizing environment. North of the Bastia village
almost 7 km before the Sukhidhang, alternate bands of sandstone and shales
(chocolate colour) are observed dipping 42o
in the north direction. The overall Siwalik
Group is composed of sandstone, siltstone, clay and pebbles bed. Upwards the
sandstones become coarse with inclusions of yellow and brown clay pellets. The
rocks of the Siwalik group are also characterized by the “salt and pepper” texture. The
outcrops of the Siwalik rocks near Sukhidhang consist again of fine grained but
compact and hard, grey to greenish sandstone indicating a reducing environment, with
subordinate purple clay intercalations. Some coal seams are observed within
sandstone at different places along the Rela ka Khola-Hathi Khor section.
126
The megascopic structures cover the folds and thrusts. The three major thrust
are exposes in the study area i.e. Himalayan Frontal Thrust (HFT), Main Boundry
Thrust (MBT) and South Almora Thrust (SAT). Main Boundary Thrust (MBT)
separates the Siwaliks in the south and Bhimtal formation in the North. South Almora
thrust separates the Bhimtal formation in the south and Almora crystallines in the
north. The Bhimtal formation contains quartzite, chlorite schist and phyllonite and the
Almora crystallines contains quartzite, phyllonite, mylonite, chlorite schist and augen
gneisses. The mesoscopic structures have been noticed in the area categorized under
minor folds, planar structures and linear structures. The plunge amount of the folds
varies from 28o and 40
o towards NE and SW. A variety of planar and linear structures
have been identified and their significance and relations to the major structures have
been pointed out. The various planar structures study includes: Primary bedding plane
(S0), Foliation plane (S1) and Joints (S2).
The general strike directions of the primary bedding plane (S0) are NE-SW
and dip varies from 30o to 77
o towards NW and SE. The foliation planes are also
recognized in the study area. The general strike direction of the foliation plane is NE-
SW and the dip varies from 22o-76
o towards SE or NW.
A variety of microstructures have been noticed in the thin section of study
area. The porphyroclasts occur in a variety of shapes with respect to their trails. In the
study area a various types of porphyroclasts are noticed i.e. θ, Ф, σ and δ type
porphyroclast in the gneiss and mylonite rocks of the crystalline units. A variety of
microstructures are also observed like mica fish, micro folds, book-shelf structure, S-
C structure and quartz ribbon structure. These structures indicates top to south sense-
of-shear.
127
Strain has been estimated by identifying a number of relevant strain markers
with the help of Fabric 8 software. The various strain markers have been identified
and classified under two broad categories: Grain shape analysis of quartz (Panozzo
Plots) and Deformed Pophyroclasts. The deformed porphyroclasts have been
subjected to estimation of strain estimation in two dimensions has been done by
following methods: Fry Method and Rf / Ø Method. The Panozzo method has been
adopted to apply on 16 thin sections of rock samples. The outcome values range from
1.07 to 1.65. The analysis of quartz grains reveals that the area has undergone high
strain conditions. The Fry method has been applied on 16 thin sections of rock
samples. The output values of the Fry method range from 1.30 to 2.00. The higher
values suggest that the Dhaun area has more strained than the Bastia. The Rf / Φ
technique are applied on 16 thin sections of rock samples of the study area and their
graphs have been prepared including their chi2 plot. The plots show that the Rf / Φ
values range between 1.1 and 2.2. The result suggest that the rocks of the vicinity of
the South Almora Thrust zone have higher strain values.
The morphometric analysis of the Ladhiya and Lohawati River Basins has
been carried out with the help of survey of India (SOI) toposheet numbers 62C/3, 4, 7
and 8. The morphometric parameters have been divided into four categories viz.
Linear Parameters (stream order, stream length, stream length ratio, bifurcation ratio,
RHO coefficient), areal parameters (drainage density (Dd), drainage texture, stream
frequency, form factor), Shape parameters (elongation ratio, circularity index) and
Relief and Gradient Parameters (basin relief, relief ratio, gradient ratio) have been
calculated. The important results are as below:
128
• The Ladhiya and Lohawati River Basins are the seventh and sixth order
streams.
• The bifurcation ratio of the Ladhiya and Lohawati sub-basins ranges between
8.42 to 2.16 and 6.44 to 2.0. The mean Rb of the Ladhiya basin is 3.74 and for
the lohawati basin is 4.08.
• The RHO coefficient of the sub-basins of Ladhiya and Lohawati River varies
from 0.05 to 1.10 and 0.03 to 0.58.
• The stream frequency for the Ladhiya river basin varies from 4.03 to 29.41
while, for the Lohawati river basin, it vary from 2.41 to 8.36.
• The drainage density of the Ladhiya and Lohawati sub-basins are 4.52 and
2.99 respectively.
• The drainage texture of the Ladhiya and Lohawati sub-basins ranges between
12.33 to 207.55 and 6.96 to 26.76 respectively.
• The shape parameters like elongation ratio and circularity index indicate
general shape of the basin. The elongation ratio of the Ladhiya and Lohawati
River basin is 0.16 and 0.17 respectively.
• The circularity index of the Ladhiya and Lohawati River basin is 0.56 and
0.64 respectively. Values approaching 1 indicates that the basin shapes are
nearly circular with uniform infiltration.
• The form factor of the Ladhiya basin is 0.35 and 0.46 of the Lohawati basin
indicates lower peak flow for longer duration.
129
Several evidences of neotectonics such as active landslides, river terraces,
vertical down-cutting of the rivers, deep gorges of rivers, triangular facets and tilting
of beds, have been noticed in the various parts of the study area.
The Rose diagram based on the lineaments direction gives the mean resultant
direction of the study area is NNE-SSW (004-184). The 155 azimuth data were used
to plot the rose diagram with the help of GEOrient, version 9.5.0 software. The data
description of the rose diagram gives the sector angle 10o and approximately 95%
confidence interval.
A Digital Elevation Model (DEM) is one of the most useful sources of
information for spatial modeling and monitoring, with applications as diverse as
environment and earth science, e.g. catchment dynamics; landscape simulation (Pike
et al. 2007). Shuttle Radar Topography Mission (SRTM) data are used to prepare the
DEM and contour map with the help of Arc GIS 10 software. The general topography
of the study area shows rugged surface topography with low terrain. Linear features
are also noticed in the form of rivers and gullies, Ladhiya river is the main river in the
study area that is flowing in the SE direction almost in the middle part of the study
area and meet the Kali river. The Kali river demarcates the western border of Nepal
with India. The general trend of the Kali river is SW direction in the study area but it
abruptly changes its course towards NW at 60o and then it takes turn at right angle and
again it also takes sharp turn at right angle. This is due to some tectonic activity,
because it is closer to the South Almora Thrust (SAT) and Main Boundary Thrust
(MBT) zone. The different shades of colour in the digital elevation model show the
height variations in the study area. The highest elevation is varies from 1769 to 2198
m and lowest elevation are ranges between 220 m and 354 m.
130
The contour map of the area shows that the SW portion has gentle slope and
the NW portion has steeper slope. North of the Sukhidhang the closeness of the
contour line increased up to the northern part of the study area. The lowest value of
the contour line in the study area is 250 m and the highest value of the contour line is
2150 m. The Tanakpur area is situated on the lower value of the contour line and the
Champawat is on the higher value of the contour line in the study area.
In the present study area the slope varies from less than 5o to a maximum of
55o with different shades of colour (green, yellow, red). The lowest slope angle is
measured around Tanakpur that is less than 5 degree in the southern part and the
maximum slope angle is 55 degree which is observed in the NE part of the study area.
In general Northern part of the study area shows high slope and the Southern part
shows low angle. Sukhidhang, Chalthi, Swala and Dhaun have slope angle ranges
between 40 to 50 degree and the Champawat ranging between 10 to 20 degree slopes.
The presence of Himalayan Frontal Fault (HFF) in the southern part of the area makes
the lowered slope angle due to formation of foreland basin as this is the region where
high sediments accumulation takes place. Slope aspect map identify the slope
direction (0-360) in compass degree (0=North, 180=South, etc.). Flat areas have no
down slope direction which are given a value of -1.
The overall drainage pattern of the Ladhiya and Lohawati basins is dendritic to
subdendritic. It has been observed that the total number of streams gradually increases
as the stream order decreases and vice-versa. The high degree of variation in the order
and size of the tributary basin is attributed to the physiographic condition of the area.
The higher number of streams indicates a juvenile topography of the area. The
bifurcation ratio that is related to the drainage density, junction angle, lithological
131
characteristics, basin shape and basin area of Ladhiya and Lohawati river basins
ranges from 8.42 to 2.16 and 6.44 to 2.0 respectively. A bifurcation ratio greater than
five is an indication of structurally controlled drainage network (Strahler, 1957).
Therefore it is clear that the sub-basins having bifurcation ratio greater than 5
suggests a strong control of faults, lineaments and others structural features over the
drainage. The stream frequency is an indicative of slope of an area, higher values
suggest steep slopes and vice-versa. In the study area the stream frequency values are
found to be relatively higher suggesting the presence of steep slopes. The higher value
of drainage density is suggestive of the presence of impermeable subsurface material
and high relief of the basin. The drainage texture of the two basins is very fine
suggesting a highly dissected terrain.
The shape parameters indicating the general shape of the basin helpful in
delineating the areas prone to flash flood and high discharge during the monsoon. The
various shape parameters of the Ladhiya and Lohawati river basins suggests an
elongated shape. The higher values of the form factor indicate that the sub-basins
have been experiencing high peak flows (flash flood) from time to time (Chopra,
2005). Delineating the sub-basins on the basis of higher values of shape parameters
thus may form an important tool to locate the areas prone to short high peak flows
during flash floods.
Major landslides are present along the Main Boundary Thrust (MBT) zone and
the Himalayan Frontal Thrust (HFT) zone near the Sukhidhang of Tanakpur-
Champawat area. The evidences show that the landslides increase every year and
cause problems to the local people of the area. In the last five years (2006-2011), the
area of the landslide near Shiala village have increased from 1.72 to 1.81sq km, Batna
132
gad landslide 0.40 to 0.50 sq km and Chaundakot landslide 0.28 to 0.39 sq km. These
landslides have expanded their areas by about 0.019 sq km per year. This is also
affecting the social life of the villagers, damaging the road network and also affecting
the human life. A detailed study of landslides has also been carried out along the
Tanakpur-Champawat highway. About 18 slides are observed in which most are of
debris type and rock fall. The landslide scatter map shows that the middle part of the
area is more affected by landslides i.e. around Sukhidhang and Chalthi. The whole
area is divided into 5 km X 5 km grids to make a zone for better understanding the
landslide affected areas then it is found that the zone 16 is more affected by landslides
i.e. about 44 percent or 2.728 sq. km. The least affected areas that are about .031 sq
km at the west of Tanakpur i.e. zone no. 6 and 12. The areas which are not affected by
landslides are found near Tanakpur, near Champawat and NE of Shim village.
Therefore, it may be concluded that the various geomorphic features of active
tectonism as well as the various drainage parameters of the area suggest a tectonic
control on the geomorphic evolution of the area.
133
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