Environ Earth Sci
DOI 10.1007/s12665-011-1324-1
ORIGINAL ARTICLE
Drainage morphometry of Himalayan Glacio-fluvial basin, India:
hydrologic and neotectonic implications
Rameshwar Bali • K. K. Agarwal • S. Nawaz Ali
S. K. Rastogi • Kalyan Krishna
•
Received: 6 June 2010 / Accepted: 16 August 2011
Ó Springer-Verlag 2011
Abstract Morphometric analysis, being widely used to
assess the drainage characteristics of the river basins, has
been found to be a useful tool to delineate the glacial till
covered overburden material as well as to identify areas
prone to flash floods in present studies. A number of
parameters including the stream frequency, drainage density and drainage texture suggest that the unconsolidated,
unstratified and highly permeable glacially deposited
overburden till material facilitates the infiltration of
snowmelt and rainwater in the Pindari glacio-fluvial basin,
Eastern Kumaun Himalaya, India. Likewise, other till
overburden covered glacial and proglacial areas of Higher
Himalayan regions have been contributing to the groundwater budget. The shape parameters further suggest that the
sub-basins with higher form factor are more prone to flash
floods. Besides this, the anomalies in the morphometric
parameters have been found to be a useful tool to delineate
zones of active tectonics in such areas.
Keywords Morphometric analysis Glacio-fluvial Basin Himalaya Water infiltration Flash flood Neotectonics
Introduction
Morphometry has been defined as quantitative measurements of landscape shape (Keller and Pinter 1996). The
morphometric descriptors represent relatively simple
R. Bali (&) K. K. Agarwal S. Nawaz Ali S. K. Rastogi K. Krishna
Centre of Advanced Study in Geology,
University of Lucknow, Lucknow 226007, India
e-mail: [email protected]
approach to describe basin processes and to compare basin
characteristics. Geology, relief and climate are the primary
determinants of running water functioning, at the basin
scale (Lotspeich and Flatts 1982 and 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, slope and the surface relief tend to reach a steady
state in which the morphology is adjusted to transmit the
sediment and excess flow produced. Morphometric studies
also delineate physical changes in drainage system over
time in response to natural disturbances or anthropogenic
activity (Thompson et al. 2001). In the classic review of
drainage basin morphometry, Gardiner and Park (1978)
have argued that basin morphometry affords a simple way
of measuring landforms which further has several applications. Drainage basin morphometry has been of use in
attempting to explain and possibly predict longer term
aspects of basin dynamics resulting in morphological
changes within the basin. The geometry of fluvial landforms was earlier not considered to be significant; however,
Jennings (1973) has suggested that morphometry is a basic
component of contemporary geomorphology. Similarly,
Chorley (1969) suggested that fluvial processes and forms
are of utmost significance in virtually all landscapes.
Morphometric analysis has of late been used for applied
purposes. The original Horton formulation of basin morphometry was carried out partly with a view of deriving a
hydrological method by which discharge events could be
predicted for ungauged rivers. Despite the large number of
indices proposed by various workers, often for different
purposes and in different geographical areas and scientific
disciplines, relatively few aspects of basin forms are
measured by available indices (Gardiner and Park 1978).
123
Environ Earth Sci
Fig. 1 Location map of the
Pindari Glacio-fluvial Basin
The present studies have been carried out along the
NE–SW elongated Pindari glacio-fluvial basin. The basin
(Fig. 1) located in the upper reaches of Bageshwar district
of Uttarakhand, has an area of 632.67 km2. It lies between
latitude 30°160 1500 –30°190 1000 N and longitudes 79°590 0000 –
80°010 5500 E and is located in the Survey of India (SOI)
Toposheet Nos. 62 B/3, 62 B/4, 53 N/15 and 53 N/16. It
can further be divided into glaciated (126.02 km2) and nonglaciated areas. The main glaciers of the basin include the
Pindari glacier, Kaphni glacier and Sunderdunga glacier,
which drain into the Pindari River (Fig. 1). The basin is
constituted of the Central Crystalline rocks of the Higher
Himalaya in the upper reaches and the Lesser Himalaya in
the lower reaches. The Precambrian metamorphic rocks of
the central belt of Himalaya have been designated as the
Vaikrata Group (Valdiya 1973, 1979, 1981) and as the
‘‘Central Crystalline Zone’’ by Heim and Gansser (1939).
123
The Vaikrata group, made up of coarse mica-garnetkyanite and sillimanite-bearing psammitic metamorphic
rocks are divisible into Joshimath Formation, Pandukeshwar Formation, Pindari Formation and Budhi Schist
(Table 1; Fig. 2). Geologically, the area under investigation consists of the rocks of Pindari Formation.
During the present study, various aspects of drainage
characteristics of Pindari River Basin have been studied in
order to evaluate their hydrological characteristics and the
geomorphic modifications in the river channel under the
influence of various factors.
Morphometric analysis
The drainage network of the Pindari glacio-fluvial basin
and its sub-basins has been digitized using the SOI
Environ Earth Sci
Table 1 Litho-tectonic
subdivision of the study area
(after Valdiya 1973; Valdiya
and Goel 1983)
topographical maps and quantitative analysis of various
morphometric parameters of the basin has been calculated using Arc View 3.2 software. The development
of drainage depends upon the subsurface geology, precipitation, exogenic and endogenic forces operating in
the area (Reddy et al. 2004; Agarwal and Sharma 2011).
123
Environ Earth Sci
Fig. 2 Geological map of the study area (Modified after Valdiya and Goel 1983)
Fig. 3 Drainage map of the
study area
The overall drainage pattern of basin is sub-dendritic in
the lower reaches and deranged towards upper reaches
(Fig. 3). The entire basin has been subdivided into 27
sub-basins (Fig. 3). The morphometric parameters have
been divided into three categories viz. Basic parameters,
123
Derived parameters and Shape parameters. The overall
morphometric analysis of the drainage network
(Tables 2, 3, 4) has been carried out following the
common laws of morphometry (Horton 1945; Strahler
1964).
Environ Earth Sci
Table 2 Basic parameters of the Pindari drainage basin
S. no.
A (km2)
P (km)
L (km)
R Nu
Stream order (Nu)
N1
N2
N3
N4
N5
Stream length (km) (Lu)
L1
L2
L3
L4
1
2.85
7.06
2.71
9
2
1
12
4.93
0.93
1.59
2
4.50
9.75
3.27
12
3
1
16
7.31
2.04
1.85
3
6.12
10.22
3.86
15
4
1
20
10.53
4.21
2.11
4
1.60
5.36
2.28
7
2
1
10
4.25
0.37
1.19
5
1.43
5.96
2.28
6
2
1
9
2.76
1.19
1.08
6
64.00
39.78
14.94
144
27
4
176
93.63
22.62
8.31
7
8
2.34
3.32
7.93
7.76
3.57
3.23
8
9
3
3
1
1
12
13
4.32
4.49
1.84
2.81
2.12
1.27
9
82.58
39.00
10.39
35
5
1
41
35.51
8.58
3.18
10
6.82
11.03
4.25
7
2
1
10
5.23
1.46
0.62
11
7.49
11.36
4.53
26
5
1
32
18.69
3.95
2.70
12
3.63
8.99
3.11
16
4
1
21
9.53
2.02
2.44
13
2.49
6.48
2.77
11
2
1
14
6.72
1.14
1.46
14
1.77
5.50
2.01
8
2
1
11
5.06
1.14
0.80
15
3.40
7.67
3.36
19
3
1
23
8.81
3.13
1.70
16
3.60
7.99
3.16
9
3
1
13
6.67
2.47
1.26
17
5.61
10.98
3.94
11
3
1
15
6.38
1.64
1.62
18
48.24
28.43
8.90
25
9
1
35
22.57
8.03
2.30
19
77.97
39.77
14.61
74
8
1
83
51.27
5.05
5.50
20
3.15
8.38
3.52
7
2
1
10
6.37
0.61
2.06
21
4.45
9.64
4.07
13
2
1
16
8.38
2.24
1.06
22
23
8.83
6.03
14.56
10.91
5.31
4.65
22
15
5
4
1
1
28
20
16.04
9.59
3.83
1.38
3.36
2.73
24
6.19
10.29
3.79
12
3
1
16
8.95
2.17
2.32
25
24.31
22.19
9.04
64
15
3
1
83
41.67
9.96
3.15
26
16.32
18.65
7.30
69
17
5
1
92
36.39
9.26
5.78
3.45
27
102.05
48.30
17.72
324
74
19
4
45.95
21.51
9.07
1
1
422
202.4
L5
5.62
6.88
13.8
Basic parameters
Stream order (Nu)
Area, perimeter and basin length
Stream ordering refers to the determination of hierarchical
position of stream within a drainage basin. Classification of
streams based on the number and type of tributary junction
has proven to be a useful indicator of stream size, discharge
and drainage area. Ordering of stream begins from the
fingertip tributaries, which do not have their own feeders
(Strahler 1952). Such fingertip streams are designated as
first order streams. Two first order streams when join
together, form second order stream just below the junction.
Similarly, two second-order streams meet to make stream
of third-order and this process continues till the trunk
stream is given the highest order. The number of streams
(N) of each order (u) for Pindari basin is given in details in
Table 2. The details of the stream characteristics confirm
Horton’s first law of stream numbering (1945) which states
that the number of streams of different orders in a given
The Pindari basin covering an area (A) of 632.67 km2 has a
perimeter (P) of 119.60 km. In case of sub-basins, the area
ranges from 102.05 (for sub-basin no. 23) to 1.43 km2
(sub-basin no. 5). Similarly, the perimeter for these subbasins ranges between 48.30 (sub-basin no. 27) to 5.63 km
(sub-basin no. 4). The area and perimeter of all the subbasins is given in Table 2. The basin length (L) corresponds to the maximum length of the basin and sub-basins
measured parallel to the main drainage line (Mesa 2006).
The main basin length for Pindari basin is 40.55 km and
the basin lengths of all sub-basins are shown in the Table 2.
Sub-basin no. 27 has a maximum length of 17.72 km,
while sub-basin no. 14 has a minimum length of 2.01 km
(Table 2).
123
Environ Earth Sci
Table 3 Derived parameters of the Pindari drainage basin
Table 4 Shape parameters of the Pindari drainage basin
Subbasin no.
Rb
Rl
RHO
Stream
frequency
Drainage
density
Texture
1
3.25
0.94
0.28
4.21
2.61
10.90
2
3.50
0.58
0.16
3.55
2.48
3
3.87
0.44
0.11
3.26
4
2.75
1.64
0.59
5
2.50
0.66
6
5.36
7
8
Sub-basin no.
Elongation ratio
Circularity ratio
Form factor
1
0.26
0.71
0.38
2
0.21
0.59
0.42
8.80
3
0.17
0.73
0.41
2.75
8.96
4
0.24
0.69
0.30
6.25
3.63
22.68
5
0.27
0.50
0.27
0.26
6.29
3.51
22.07
6
0.07
0.50
0.28
0.42
0.07
2.75
2.03
5.58
7
0.21
0.46
0.18
2.83
3.00
0.78
0.53
0.27
0.17
5.12
3.91
3.53
2.58
18.07
10.08
8
0.24
0.69
0.31
9
0.22
0.68
0.76
9
6.00
0.30
0.05
0.49
0.57
0.27
10
0.40
0.70
0.37
10
2.75
0.34
0.12
1.46
1.07
1.56
11
5.10
0.44
0.08
4.27
3.38
14.43
11
12
0.12
0.15
0.72
0.56
0.36
0.37
12
4.00
0.70
0.17
5.78
3.85
22.25
13
0.19
0.74
0.32
13
3.75
0.72
0.19
5.62
3.74
21.01
14
0.21
0.73
0.43
14
3.00
0.46
0.15
6.21
3.95
24.52
15
0.15
0.72
0.30
15
4.66
0.44
0.09
6.76
4.01
27.10
16
0.21
0.70
0.36
16
3.00
0.44
0.14
3.61
2.88
10.39
17
0.28
0.58
0.36
17
3.33
0.61
0.18
2.67
1.71
4.56
18
0.24
0.74
0.60
18
5.88
0.31
0.05
0.72
0.68
0.48
19
0.16
0.61
0.36
19
8.62
0.59
0.06
1.06
0.79
0.83
20
0.22
0.56
0.25
20
2.75
1.73
0.62
3.17
2.86
9.06
21
0.20
0.60
0.26
21
4.25
0.36
0.08
3.59
2.62
9.40
22
0.14
0.52
0.31
22
23
4.70
3.87
0.55
1.05
0.11
0.27
3.17
3.31
2.63
2.27
8.33
7.51
23
0.20
0.63
0.27
24
0.21
0.73
0.43
24
3.50
0.65
0.18
2.58
2.17
5.59
25
0.09
0.62
0.29
25
4.08
0.90
0.22
3.41
2.53
8.62
26
0.08
0.58
0.30
26
4.15
0.48
0.11
5.63
3.36
18.91
27
0.04
0.54
0.32
27
4.25
0.65
0.15
4.13
2.86
11.81
Rb ¼ Nu =Nu þ 1
drainage basin tends closely to approximate an inverse
geometric ratio.
Stream length (Lu)
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 SOI topographical maps. The total stream
length of the Pindar basin is 912.81 km, while the stream
lengths of the sub-basins are given in Table 2.
Derived parameters
Bifurcation ratio (Rb)
This parameter expresses the ratio of number of streams of
a given order (Nu) to the number of stream segments of the
higher order (Nu ? 1) (Horton 1945). It is expressed as:
123
Strahler (1952) demonstrated that Rb shows only a small
variation for different regions on different environment
except where powerful geological control dominates. The
present study shows that the entire Pindari basin has the
mean Rb value of 4.02, while for the sub-basins it varies
from 8.62 to 2.50 (Table 3). The sub-basin no. 19 shows
higher value of Rb when compared with the others.
Stream length ratio (Rl)
Stream length ratio (Rl) has been defined as the ratio of the
mean length of the higher order to the next lower order of
stream segment (Horton 1945). The stream length ratios
have been calculated as:
Rl ¼ Lu =Lu 1
where Lu = stream length of an order u, Lu - 1 = stream
segment length of next lower order.
Environ Earth Sci
The mean stream length ratio of the Pindari River Basin
is 1.44. The Rl between streams of different order in the
study area reveals that the Rl for sub-basins varies between
0.30 and 1.73 (Table 3). 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).
RHO coefficient (RHO)
RHO coefficient is the ratio between the stream length ratio
(Rl) and the bifurcation ratio (Rb) (Horton 1945):
RHO ¼ 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 Pindari basin is 0.18 while the RHO of
the sub-basins varies between 0.5 and 0.62 (Table 3). Subbasins with higher values of RHO have higher water
storage during flood periods and as such attenuate the
erosion effect during elevated discharge (Mesa 2006).
Stream frequency (Fs)
Stream frequency (Fs) or channel frequency is the total
number of stream segments of all orders per unit area
(Horton 1932):
Fs ¼ RNu =A;
where RNu = total number of stream segments of all
orders, and A = area of the basin.
The stream frequency is related with permeability,
infiltration capacity and relief of the sub-basins (Vijith and
Sateesh 2006). The Fs of Pindari basin is 3.82 km-2, while
the Fs for the sub-basins varies between 0.49 and 6.76
(Table 3). 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.
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 Sateesh
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 expressed as:
Dd ¼ RLt =A;
where RLt = 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/km2 in
humid regions with an average density of 1.03 km/km2
(Langbein 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 Pindari River Basin is 2.63 km/km2, while
the Dd of all the sub-basins is given in Table 3.
Drainage texture (T)
It is the ratio between total numbers of stream segments of
all orders to the perimeter of the basin (Horton 1945).
Horton 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, the 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 (Smith 1950).
T ¼ Nu =P
where Nu = total no. of streams of all orders, P = perimeter (km).
Based on the values of T, it is classified (Smith 1950) as:
very coarse ([2), coarse (2–4), moderate (4–6), fine (6–8),
very fine (\8).
Texture of the entire Pindari River Basin is 11.54. For
the individual sub-basins T ranges from 0.27 to 27.10
(Table 3). Some of the sub-basins like 9 and 18 show very
coarse texture (Fig. 3) while a few others, e.g. 14 and 15
show a very fine texture.
Shape parameters
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:
123
Environ Earth Sci
p
Re ¼ D=L ¼ 1:128 A=L
where A is the area of the basin.
The values of elongation ratio vary from zero (highly
elongated shape) to one (circular shape). Values close to
1.0 are typical of regions of very low relief whereas that
of 0.6–0.8 are associated with high relief and steep
ground slope (Strahler 1964). The Re of the Pindari basin
is 0.66 and indicates it to be elongated with high relief
and steep slope. The value of Re for the sub-basins is
shown in Table 4. A circular basin is more efficient in the
discharge of runoff than an elongated basin (Singh and
Singh 1997).
Circulatory ratio (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 expressed as:
Rc ¼ 4pA=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 significant ratio, which
indicates 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 Pindari River Basin is 0.63, while
that of other sub-basins ranges between 0.46 and 0.74
(Table 4).
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 expressed as:
Ff ¼ 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 Pindari
River Basin is 0.354, while the Ff of sub-basins ranges
from 0.18 to 0.76 (Table 4).
123
Evidences of active tectonics
The 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). Glacio-fluvial landforms formed
during the Late Quaternary are thus one of the best
repositories for recording the evidences of ongoing active
tectonics in the Himalaya. The proglacial areas of higher
Himalayan region usually experience precipitation dominantly in the form of snow and lesser amounts of rainfall.
These areas thus escape the major denudational processes
that are encountered in abundance in the southern part of
the Himalaya. The anomalies present in the geomorphic
disposition of such areas indicate the control of active
tectonics on their evolution (Bali et al. 2003). In the recent
investigations in the Pindari Glacier valley a number of
features like fluvial terraces, entrenched stream courses,
inclined sedimentary beds etc. clearly indicate that the
area is neotectonically active. Some of the important
morphological evidences of neotectonism are given as
under.
Seismic activity
The area comes under the Zone IV in the Seismic
Zonation map of India (1996). The neotectonic activity in
the area is well documented by the occurrence of a
number of seismic events in the form of earthquakes.
Historic and recent seismic activity of the region around
the study area, reveals that the region has experienced a
number of seismic events and at least three major earthquakes of magnitude around 7 (Rajendran et al. 2000;
Joshi 1998) e.g. the Uttarkashi earthquake of 1991
(magnitude 6.8 with epicenter at a depth of 15 km) and
the Chamoli earthquake of 1999 (magnitude 6.4 with
epicenter depth of 21 km).
Khattri et al. (1989) indicated that moderate earthquakes
occur in this region due to the reactivation of low angle
thrust faults. The study area is bound by two well-known
thrust systems, i.e. by Trans-Himadri Fault on the northern
side and Pindari Thrust on the southern side. Moreover, the
area is dissected by a number of smaller faults and thrusts,
many of which may be active.
Environ Earth Sci
Fig. 4 a Inclined sedimentary layers present in the left lateral moraine. b Asymmetrical river terraces and entrenched river channel near Amula
village. c Skewed fan deposit present near the Zero point
Inclined sedimentary layers, asymmetrical fluvial
terraces and river entrenchment
The Pindari basin is a NE–SW trending basin of Pindari
River, a tributary to the Alaknanda River. Just from the
downstream of the Pindari Glacier snout, a silty to sandy
glacio-lacustrine deposit is found well preserved at the
summit of the left lateral moraine that formed during the
last phase of glacial recession. This deposit disposed
almost 100 m above the valley floor shows tilting (*25°
due east) of the layers within it (Fig. 4a). Such a disruption
of the bedding is being attributed to neotectonic activity in
the area.
At least two levels of terraces are present just downstream of the snout. Moreover, near Amula village,
asymmetrical terraces are present on the sides of the Pindari River (Fig. 4b). The Pindari River flowing along a
NW–SE running Phurkia fault has incised through the fan
deposits resulting into the formation of terraces. At Malia
Doar, the Pindari River shows entrenchment resulting into
the formation of narrow gorge.
Anomalies in the drainage morphometry
In the Pindari River Basin it has been observed that the
lower order streams are abundant and show high bifurcation ratio. The morphometric analysis of the area reveals
that the bifurcation ratio between the first and second order
stream is 4.40, while that of second and third order stream
is 3.71. These higher values suggest that the area is tectonically active.
Skewed fans
The occurrence and distribution of the fan deposits on the
two sides of the valley seems to be controlled by the neotectonic activity. In the present study, it has been noticed
that the concentration of the fan deposits as well as the
landslides is more on the left side of the valley while, there
is a very less concentration of fan deposits on the right side
of the valley and nearly no landslide zones are present.
Skewing of the fan deposits is a result of the neotectonic
activity (Bali et al. 2003). After a detailed investigation, it
123
Environ Earth Sci
Fig. 5 MSS image of the study
area. Glacial, proglacial and till
covered areas lie north of the
dotted line
has been observed that the debris fans near zero point show
a very high degree of skewness caused due to active tectonics (Fig. 4c).
Discussion and conclusions
Morphometric analysis of Higher Himalayan regions
(presently under the domain of fluvial processes) has been
found to be a useful tool to understand the geomorphic
evolution pro-glacial terrains (Bali et al. 2003). During the
present study, besides the neotectonic implications, it has
also been effectively utilized to delineate the present day
till covered areas of the region. It is evident that the
unconsolidated, unstratified and heterogeneous till material
is highly impervious. As such, these areas show a poor
development of drainage network and thus a very low
Drainage density (Dd). Drainage density affects the concentration time and hence the magnitude of peak flow.
Timing of discharge events in the form of lag time has also
been related to the basin morphometric characteristics
(Kennedy and Watt 1967). Increase in drainage density
suggests increasing flood peaks. Similarly, decrease in
drainage density generally suggests decreasing flood volumes (Pallard et al. 2009).
123
One of the important controls on drainage density is
exerted by the infiltration capacity of the overburden
material. A long concentration time implies more opportunities for water to infiltrate. It controls the amount of
water available for the surface runoff and in turn affects the
development of stream pattern. As the unconsolidated,
unstratified, heterogeneous angular till deposits covering
the glaciated and the deglaciated region have high infiltration capacity, there is little overland flow and the
channel development is inhibited (Figs. 3, 5). Because of
this characteristic feature of the overburden material of
glacial and proglacial terrain located in the Higher Himalayan region, the water derived by slow melting of snow
covered areas is unable to move down the slopes for long
distances as surface runoff. It rather gets infiltrated through
the highly porous overburden material. The surface
expression of such a phenomenon is the profound development of deranged drainage in such areas. The infiltrated
subsurface water moves down and contributes to the
groundwater budget of the area rather than moving down
the slopes as surface runoff.
Although, the surface runoff is encouraged on steep
slopes as most of the glaciated regions have a high relief.
However, it can be seen that even with the steep slopes, the
highly porous overburden till material does not allow much
Environ Earth Sci
of the melt water as well as the precipitated rainwater to
flow on the surface. The nature of the overburden material
rather compels them to infiltrate.
The overall drainage density (Dd) for the Pindari River
Basin is 2.63/km. It, however, varies between 0.57 to 4.01
for the different sub-basins. The values being appreciably
less than 5.0 indicates that the Dd falls in the category of
coarse to very coarse drainage. The drainage density
increases for the sub-basins located in the lower latitudes as
these areas have relatively lesser and thinner overburden
material. Also, in these areas the rain water moves down
the slope for some distance partly as surface runoff, thereby
giving rise to a relatively higher Dd.
A close examination of various shape parameters suggests that the Pindari Glacio-fluvial basin as a whole is
moderately elongated in nature while, some of its subbasins, e.g. 9 and 18 show a higher value of elongation
ratio and circulatory ratio. Similarly, these basins also
show a relatively higher value of form factor (Ff). These
two sub-basins (Fig. 3) incorporate the Sunderdunga and
the Pindari glacier. As suggested earlier (Chopra et al.
2005), these sub-basins have higher values because from
time to time these must be experiencing high peak flows
(flash floods), due to the bursting of the supra glacial and
englacial water bodies. Not only this, the circularity has
further been enhanced by broadening of glacial valley
during glacial movement. Delineating the sub-basins on the
basis of higher values of these indices thus becomes an
important tool to decipher the areas prone to short high
peak flows during flash floods.
Palaeoglacial reconstruction in the Himalayan region as
well as geomorphological evidences suggest that there was
a much thicker ice cover in the region than what has been
perceived. The recession and melting of the glacial ice
mass caused as a result of climate change, resulted in the
unloading of the valley floor and hence unstraining of the
area. This process along with the present stress regime
resulted in the reactivation and formation of new set of
fracture planes (Bali et al. 2003). It has been observed that
the Bifurcation ratio (Rb) varies between 2.52 to 8.62 while
the circulatory ratio of the sub-basins ranges between 0.46
to 0.74. The higher variation of the Rb and the values less
than 0.60 for circularity ratio suggests the presence of
youthful streams in the sub basins. Thus, the presence of
various characteristic geomorphological features as well as
anomalies in various drainage morphometric parameters of
various sub-basins suggests the control of active tectonics
on the geomorphic evolution of the area.
Acknowledgments Authors are thankful to the Head of Department, Centre of Advanced Study in Geology, University of Lucknow,
Lucknow, for providing working facilities. Thanks are also due to
Department of Science and Technology, Government of India, New
Delhi, for funding the project vide project no. ESS/91/29/2004.
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Elsevier Editorial System(tm) for Geomorphology
Manuscript Draft
Manuscript Number: GEOMOR-2918
Title: Morphostructural development of a part of the Garhwal Himalaya: Insight from morphometric
studies of a strike-parallel river
Article Type: Research Paper
Keywords: Keywords: Morphometric analysis, Nandakini River Basin, Neotectonics, Garhwal Himalaya,
Rivers and Tectonics.
Corresponding Author: Prof. A.R. Bhattacharya, Ph.D.
Corresponding Author's Institution: University of Lucknow
First Author: A.R. Bhattacharya, Ph.D.
Order of Authors: A.R. Bhattacharya, Ph.D.; Yogendra Bhadauriya, Ph.D.; Pankaj Sharma, M.Sc.; S.
Nawaz Ali, Ph.D.; Biswajeet Thakur, M.Sc.; S. K Pandey, M.Sc.
Abstract: A part of the Garhwal Himalaya has been studied for neotectonic activities in relation to
geological and structural setup of the area. A strike-parallel major river basin-the Nandakini River
Basin- has been selected for morphometric analysis, mainly because similar work is absent in the
Himalayan region. The area has been found to show a variety of neotectonic features. The major rivers
and streams are structurally controlled and are neotectonically active. Detailed morphometric analysis,
including preparation of DEM and SRTM maps, has been carried out by subdividing the basin into 27
sub-basins that are dendritic to sub-dendritic drainage pattern. In general, most of the structurally
disturbed zones of the area are also the zones of neotectonic activities, thus suggesting that structural
and neotectonic processes are related to each other. It appears that the processes of Himalayan
deformation that had initiated during the Himalayan orogeny are active even today.
Suggested Reviewers: S. P. Singh Ph.D.
Professor, Geology, Bundelkhand University, Jhansi, Uttar Pradesh India
[email protected]
V. N. Bajpai Ph.D.
Professor, Geology, University of Delhi, New Delhi, India
[email protected]
T. K. Biswal Ph.D.
Professor, Department of Earth Science , Indian Institute of Technology, Mumbai, India
[email protected]
Cover Letter
To:
Editor,
“Geomorphology”
Subject: Re-submission of manuscript after minor corrections as per your suggestion.
Dear Sir,
Kindly refer to our manuscript entitled “Morphostructural development of a part of the
Garhwal Himalaya: Insight from morphometric studies of a strike-parallel river” (vide
GEOMOR 2918).
We are happy to inform you that we have considered all the five points that you have
suggested as minor corrections.
We are sorry that the Tables and Figures could not be included as continuation of the text
at the end of the manuscript because the computer is not accepting differently formatted items.
As such Figures and Table 1 are being sent separately.
Thanking you.
Yours sincerely.
Prof. A.R. Bhattacharya
Department of Geology
University of Lucknow
Lucknow-226007
India
Email: [email protected], [email protected]
Tel. +91-522-2740015
Fax- +91-522-2740037
Responses to Technical Check Results
To,
Editor
“Geomorphology”
Ref. Our manuscript entitled “Morphostructural development of a part of the Garhwal
Himalaya: Insight from morphometric studies of a strike-parallel river” (GEOMOR
2918).
Dear Editor,
Thank You for your useful comments and suggestions on the structure of our
manuscript. We have modified the manuscript accordingly, and detailed corrections are
listed below point by point:
1) The order of the figure caption page, figures and tables at the end of the
manuscript should be: figure caption page, tables and figures. Please revise.
We have revised our manuscript by entering figure caption page, tables and
figures as per your suggestion.
2) All figures and tables put at the end of the manuscript should be labeled as, e.g.,
Figure 1, Figure 2, Table 1, etc.
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Figure 2, etc. Table 1.
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Manuscript
Click here to view linked References
1
Morphostructural development of a part of the Garhwal Himalaya: Insight from
2
morphometric studies of a strike-parallel river
3
4
A.R. Bhattacharya1, Yogendra Bhadauriya2, Pankaj Sharma1, S. Nawaz Ali1, Biswajeet
5
Thakur3 and S.K. Pandey3
1
6
7
2
8
3
Department of Geology, University of Lucknow, Lucknow-226 007, India
Present Address: Mahan Coal Limited, Waidhan, Singrauli- 486 886, (M.P.), India
Present Address: Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow-
9
226 007, (U.P.), India
10
Corresponding author: A.R. Bhattacharya.
11
Email: [email protected], [email protected]
12
Tel: +91-522-2740015; Fax: +91-522-2740037
13
14
Abstract: A part of the Garhwal Himalaya has been studied for neotectonic activities in
15
relation to geological and structural setup of the area. A strike-parallel major river basin-
16
the Nandakini River Basin- has been selected for morphometric analysis, mainly because
17
similar work is absent in the Himalayan region. The area has been found to show a
18
variety of neotectonic features. The major rivers and streams are structurally controlled
19
and are neotectonically active. Detailed morphometric analysis, including preparation of
20
DEM and SRTM maps, has been carried out by subdividing the basin into 27 sub-basins
21
that are dendritic to sub-dendritic drainage pattern. In general, most of the structurally
22
disturbed zones of the area are also the zones of neotectonic activities, thus suggesting
1
23
that structural and neotectonic processes are related to each other. It appears that the
24
processes of Himalayan deformation that had initiated during the Himalayan orogeny are
25
active even today.
26
27
28
Keywords: Morphometric analysis, Nandakini River Basin, Neotectonics, Garhwal
Himalaya, Rivers and Tectonics.
29
30
1. Introduction
31
Most young mountains are characterized by their internal instability which is a
32
reflection of the ongoing structural and tectonic processes – active tectonics - of the
33
mountain. The Himalayan mountain range constitutes one of the best examples of active
34
tectonics. It is believed that the mountain building processes that had started with the
35
collision of Indian and Asian plates are still going on and are manifested by numerous
36
geomorphological features. One of the best manifestations of active tectonics of a
37
mountain is basin morphology/configuration and the associated drainage pattern. Since
38
the latter (drainage pattern) is highly susceptible to active tectonics, study of the
39
morphological features and morphometric analysis of the drainage pattern of an area
40
throw significant light on the nature of ongoing tectonic processes.
41
In the Himalayan region, the major rivers flow from north to south. Till date, a
42
few such river systems have been studied from the viewpoints of river morphology,
43
morphometrics and neotectonics. East-west flowing rivers, on the other hand, are very
44
rare and also as yet we do not have any detailed study of their basins. Undoubtedly,
2
45
information from such east-west flowing river systems should advance our knowledge on
46
the state of present-day activity of the mountain chain. One such major river is Nandakini
47
River of Garhwal Himalaya. The present work incorporates a detailed study of
48
geomorphology, neotectonic behaviour and morphometric analysis of the Nandakini
49
River Basin.
50
2. Geological Set-up
51
The Garhwal Himalaya represents all the four major lithotectonic subdivisions
52
(Figure 1) of the Himalaya (Gansser, 1964), from S to N, these are: (1) Outer Himalaya,
53
mainly represented by Siwalik Supergroup of rocks and their equivalents (Upper
54
Tertiary), and is bounded to the north by the Main Boundary Thrust (MBT) and the
55
Himalayan Frontal Thrust to the south. (2) Lesser Himalaya that exposes a widespread
56
sedimentary belt of upper Precambrian ages and a few outcrops of ancient crystalline-
57
metamorphic rocks that are believed to have come to rest by tectonic transport from the
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Greater Himalaya; it is delimited to the south the MBT to the south and the Main Central
59
Thrust (MCT) to the north. (3) Greater Himalaya with a persistently north-dipping thick
60
pile of crystalline-metamorphic rocks that are bounded to the south by the MCT and by
61
the Dar-Martoli Fault (DMT) or the South-Tibetan Detachment. (4) Tethys Himalaya that
62
exposes a massive pile of sedimentary rocks of Cambrian to Lower Eocene ages and is
63
bounded by the DMT to the south and by the Indus Suture Zone to the north.
64
The study area (Fig.1) falls in the northern part of the sedimentary belt of the
65
Garhwal Lesser Himalaya and exposes a widespread sedimentary belt of Upper
66
Precambrian ages. An area covering about 350 sq km has been geologically mapped
3
67
(Figure 2) (Bhadauriya, et al. 2009). In the southern part of the area, a crystalline unit –
68
Nandprayag Crystalline Unit – is exposed with ancient crystalline-metamorphic rocks.
69
The latter (Nandprayag unit) tectonically rests over the younger sedimentary belt and is
70
believed to have been tectonically transported from the Central Crystalline Zone of the
71
Greater Himalaya in the form of thrust sheets during Himalayan deformations.
72
The area studied (Figure 2) falls in Garhwal Lesser Himalaya and is represented
73
by a sedimentary belt and a crystalline rock unit (Nandprayag Crystalline Unit). In recent
74
years, a large number of workers have studied the structure of the Lesser Himalayan
75
rocks from several angles (e.g. Bhargava, 1972, 1981; Jain, 1971; Jain et al., 1971;
76
Agarwal and Kumar, 1973; Ahmad, 1975; Bhattacharya, 1972, 1976, 1979A,B, 1999;
77
Ghose, 1973; Kumar and Agarwal, 1975; Mehdi et al., 1972; Ramji, 1979; Rupke, 1974;
78
Valdiya, 1979, 1980). In the light of the available work, the megascopic structure of the
79
Lesser Himalaya is represented by km-scale synclines and anticlines with vertical/sub-
80
vertical axial planes trending E-W to ESE-WNW. The rocks are affected by numerous
81
steep to vertical faults. The mesoscopic structures of these rocks are however more
82
complicated suggesting complex structural history in the internal domain of the rocks and
83
generally show at least three generations of folding. The earlier (possibly earliest) folds
84
(F1) are represented by tight isoclinal, recumbent folds generally with E/ESE-W/WNW
85
axial trends, followed by the second generation (F2) folds that are commonly developed
86
on the limbs of F1 folds and are usually coaxial to the F1 folds. The third generation (F3)
87
folds are open folds with N/NNE-S/SSW axial trends.
4
88
Megascopically, the rocks of the area constitute a large synform (Figure 3) –
89
Nandprayag synform – that involves both the crystalline unit as well as the sedimentary
90
belt (Bhadauriya et al. 2009). Both the northern and southern contacts of this crystalline
91
unit with the sedimentary unit are tectonic and have been named as North Nandprayag
92
Thrust (NNT) and South Nandprayag Thrust (SNT) respectively.
93
The area is characterized by the presence of two major rivers: Alaknanda flowing
94
north to south and its tributary, Nandakini that flows from east to west and meets
95
Alaknanda at Nandprayag (Latitudes 79015‟E and 79025‟E and longitudes 30015‟N and
96
30025‟N). In the paper we have made a detailed study of the Nandprayag basin. Since
97
Nandakini meets Alaknanda at Nandprayag, we have also studied the various neotectonic
98
features of the confluence area.
99
100
Field studies reveal that the major geomorphic features of the study area are
structurally controlled and are at present tectonically active.
101
An important highlight of the geology of the area is that both the major rivers of
102
the area- Nandakini and Alaknanda – are tectonically controlled. The Nandakini River
103
follows the South Nandprayag Thrust for a large distance while the course of the
104
Alaknanda River is affected by a N-S trending fault system (Bhadauriya, et al. 2009,
105
Bhadauriya, 2010). This aspect has drawn our attention for conducting a detailed
106
morphotectonic study of the area, as presented in the paper.
107
3. Neotectonic Features
108
Field studies reveal that the several parts of the study area are structurally
109
controlled and are neotectonically active. Several evidences of neotectonics as well as
5
110
structures in the Quaternary sediments have been noticed in various parts of the study
111
area. The Quaternary sediments occasionally show structures like normal faults, ramp
112
and flat geometry, fault bend fold, etc. Some common neotectonic features of the area are
113
described below.
114
3.1
Landslides
115
Landslides are very common features in the area (Figure 4), especially along the
116
Alaknanda valley; in the Nandakini valley, these are less frequently developed. In the
117
present work all forms of “Slides” involving downhill movement of rock masses or
118
weathered debris along discreet shear surfaces have been taken together as landslides. In
119
the area, landslides usually occur in the form of a localized zone containing at least one
120
well-developed landslide. The width of the toe region is highly variable ranging from
121
about 8 m to about 500 m or so.
122
3.2
River Terraces
123
In the study area, river terraces (Figure 5 A-D) are developed at a number of
124
places in the Alaknanda and Nandakini River valleys. These are commonly developed
125
where the river valley shows steep slopes in the lower part and gentle slopes in the upper
126
part; sometimes these are seen in strongly incised valleys also. These are both paired and
127
unpaired. The number of terraces at a particular spot is highly variable and up to 5
128
terraces have been noticed viz. T0, T1, T2, T3, T4 (Figure 5 A and B), though at some places
129
only three levels of terraces are present (Figure 5C). At places, e.g. about 1.6 km SW of
130
Sunla (Figure 5D), the terraces have been affected by a later fault that brings the terraces
131
adjacent to the undulating rugged topography of the associated hill. There is a distinct
6
132
diversity in the vegetation of the two fault blocks. This fault plane is occupied by a
133
tributary which flows almost W to E, and this trend is parallel to the E-W trend of the
134
Nandprayag Fault System. Significantly, the fault plane affecting the above terraces is not
135
straight but shows an „S-shaped‟ geometry suggesting that this fault plane has witnessed
136
some N-S directed compressive stresses thus resulting to the present-day „S‟-shape
137
geometry. Also the tributary flows incised in its valley which, together with its S-shaped
138
geometry, suggests that uplift of this block is still going on or was active till Recent.
139
At about 600 m N of Nandprayag, terraces are developed on a segment of
140
Alaknanda River where it takes a right angle turn. Here the Alaknanda river with an
141
earlier NW-SE trend suddenly takes a sharp turn and flows almost N-S where it follows a
142
lineament. All this indicates that the terraces are directly related to the neotectonic
143
responses of the river. A Digital Elevation Model of the area, described later, has been
144
prepared that shows that at many places the Alaknanda and Nandakini rivers have been
145
incised within the valley.
146
3.3
Triangular Facets
147
Triangular facets have been defined as a physiographic feature having a broad
148
base and an apex pointing upward specifically the face on the end of a faceted spur, or,
149
triangular shaped steep sloped hill or cliff formed usually by the erosion of a fault
150
truncated hill (Summerfield, 1991). Presences of well developed triangular facets are a
151
signature of a fresh fault scarp. Therefore, the presences of triangular facets are believed
152
to be indicators of neotectonics. Dissection by many gullies or valleys causes a scarp to
7
153
be segmented into a series of triangular facets and planar surfaces with their bases aligned
154
or parallel to the fault trace.
155
Triangular facets are noticed at several places in the study area with their apex
156
angle- the angle between the two hill faces- ranging from 600 to 1020. Three triangular
157
facets are developed at 1.6 km NW of Nandprayag on the left bank of Alaknanda River
158
(Figure 6A). These facets have possibly been subjected to some later tectonic activities
159
that resulted in their shearing. This can be clearly noticed in facets B and C in which the
160
apex line is not straight but it has been sheared suggesting the influence of some later
161
deformation after their formation. Similarly 1.2 km N of Nandprayag on the left bank of
162
the Alaknanda River (Figure 6B) another prominent triangle facet can be seen along the
163
road section and a fault scarp (below the road section) is seen. The apex angle of this
164
facet is 600. The fault scarp is parallel to the arm AB of this facet.
165
3.4
Shattering of Rocks
166
At a few places, heaps of broken rocks can be seen all along the hill slopes
167
(Figure 7). The shattered rocks are of varying sizes, up to about 8 m. All this could be
168
related to some neotectonic activity in the region.
169
3.5
Sudden Turn of Rivers
170
Both the major rivers as well as the various streams of the area show sudden turns
171
in their courses at a number of places. In most cases, these turns are associated with
172
terraces (Figure 8). These features are indicative of neotectonic activity in the region.
173
3.6
Instability of Slopes
8
174
At several spots of the study area (Figure 9), group of trees are noticed with their
175
bent trunks. The bending of the trunks is towards down slope suggesting down slope
176
ground motion or instability. Since the ages of the tress are very young, may be up to a
177
few hundred years only, it is possible that this phenomenon is a signature of present-day
178
activity and hence of neotectonics. Although this could be a soil creep, we consider this
179
process as some manifestation of ground instability and hence of neotectonics also.
180
3.7
Structures in Quaternary Deposits
181
In the study area, both the major river valleys i.e. Alaknanda and Nandakini, are
182
associated with Quaternary deposits (Figure 10A). These deposits commonly occur as
183
massive pack of loose materials as well as well bedded layers. Field studies reveal that
184
the Quaternary sediments occasionally show some structures such as normal fault and
185
some thrust geometries.
186
(a)
Tilting of Beds
187
Tilting of Quaternary deposits has been observed at many places especially in the
188
Alaknanda Valley. Theoretically, it is believed that all beds are deposited horizontally,
189
and any tilt of such beds implies uplift of the ground. Thus occurrence of tilted beds in
190
several places of the Alaknanda valley suggests that the region is neotectonically active.
191
The tilting of beds in the area varies from 30 to 150 (Figure 10B). At a place 500 m NW of
192
Maithana a cliff section is exposed on the right bank of Alaknanda River. In the lower
193
part of this cliff the bedding is almost horizontal whereas in the upper part it is tilted and
194
dips towards south. It makes an angular relationship with the horizontal beds and the
195
amount of tilt is about 150. This angular relationship thus appears to be the result of late
9
196
tilting in the block suggesting that area has witnessed neotectonic activities after their
197
deposition. Tilting of beds in an area emphasizes the influence of tectonics on usually
198
horizontally or gently dipping layered sediments.
199
(b)
Normal Fault
200
At a place 1.9 km NE of Langasu on the left bank of Alaknanda River, the
201
Quaternary deposits appear to show a normal fault (Figure 11). The sediments
202
predominantly comprise of medium size sand particles. The primary bedding can be seen
203
in the form of lithological layering.
204
(c)
Ramp and Flat
205
About 700 m ESE of Langasu on the left bank of the Alaknanda river, the
206
horizontally disposed Quaternary layers show structures resembling ramp and flat
207
geometry (Figure 12) within about 10 m. A bedding plane can be seen affected by a
208
thrust (AB in the photograph that cuts the layering up-section (BC) and then again it
209
follows another bed (CD).
210
(d)
Fault-Bend Fold
211
Close observation in the layering pattern of the Quaternary deposits has also
212
revealed the presence of structures resembling a fault-bend fold (Figure 12). The
213
structure appears to have formed when a bedding thrust EC is obstructed by a ramp
214
(BC). Because of continued motion along the bedding thrust (EC) and its continuous
215
forward push simultaneously with movement along the ramp (BC), the portion of the
216
bedding plane thrust (EC) at the contact of the ramp (C) may have accommodated
217
stresses that have been accommodated by the formation of a small, open fold.
10
218
219
220
221
4.
Morphometric Analysis
222
The drainage network in the young mountain chains is believed to represent a
223
good indicator of active tectonics and drainage. Basin morphometric analysis therefore
224
reflects the steady state condition of rocks during active deformation (Seeber and
225
Gornitz, 1983; Ouchi, 1985; Marple and Talwani, 1993; Koons, 1995; Hallet and Molnar,
226
2001; Arisco et al, 2006). A simple approach to describe such adjustments of drainage
227
network against lithological variations during the ongoing tectonic processes is to
228
calculate a few parameters. It is therefore possible to describe the physical changes in
229
drainage system over time in response to natural disturbances or human impact by
230
identifying a few morphometric parameters. All this is mainly based on the fact that for
231
the given conditions of lithology, climate, rainfall and other relevant parameters of the
232
basin, the river net, the slope and the surface relief tend to reach a steady state in which
233
the morphology is adjusted to transmit the sediment and excess flow produced (Horton,
234
1945; Strahler, 1952; Rzhanitsyn, 1960 and Thompson et al., 2001).
235
A morphometric analysis of drainage basin can be considered as a simple
236
approach to describe the various morphotectonic processes of the basin and also helps to
237
compare the geomorphic attributes of different basins. The sub-basins of the Nandakini
238
River Basin are of third, fourth and fifth-orders. All the sub-basins exhibit dendritic to
239
sub-dendretic drainage pattern. The morphometric data of sub-basins is summarized in
11
240
the Table1. For morphometric analysis, as incorporated in the present work, a “basin” has
241
been defined as “a natural hydrological entity from which surface run off flows to a
242
defined drain, channel, stream or river at a particular point ” (Vittala et al., 2004).
243
Nandakini River is a right (left) bank tributary of the Alaknanda River. The river
244
originates from Sili Samudra Glacier and runs almost parallel to the Himalayan strike for
245
most of its course. The Nandakini River forms an elongate basin with an area of 542.12
246
km2. The direction of the river shows abrupt changes in its course from origin to
247
confluence. The Basin in its present form appears to have developed, and is associated
248
with, various neotectonic activities. We present here a detailed morphometric analysis to
249
manifest the neotectonic activities. Lineament analysis and preparation of a DEM and
250
contour map of the basin have also been done, as highlighted below.
251
The drainage network is digitized and a quantitative analysis of the various
252
morphometric parameters of the basin such as stream number, stream length, and stream
253
order etc. have been calculated by using Arc View 3.2 software. In order to enable a
254
systematic quantitative analysis, the Nandakini river basin has been subdivided into
255
several sub-basins (Figure 13). The morphometric parameters have been divided into
256
three major categories viz. basic parameters (area, perimeter, basin length, stream order,
257
stream length and maximum and minimum height), shape parameters (elongation ratio,
258
circulatory index and form factor) and derived parameters (bifurcation ratio, stream
259
length ratio, RHO and drainage density).
260
261
The overall drainage network has been analysed as per Horton‟s (1945) laws and
the ordering of streams has been followed after Strahler (1964).
12
262
263
264
265
4.1
Basic Parameters
266
4.1.1 Area and Perimeter
267
The Nandakini basin covers an area of 542.12 km2 and a 127.30 km. The highest
268
values of the area among the sub-basins has been recorded in sub-basin 11 (89.73 km2),
269
and lowest in sub-basin no 24 (1.93 km2). The highest value of perimeter is 43 km as
270
shown by sub-basin 11 while the lowest value is shown by sub-basin 24 (6.03 km) (Table
271
1).
272
4.1.2
Basin Length (L)
273
The basin length corresponds to the maximum length of the basin and sub-basin
274
as measured parallel to the main drainage line (Mesa 2006). The basin length for
275
Nandakini basin is 48.64 km and the basin lengths of the various sub-basins are shown in
276
Table 1.
277
4.1.3
Stream Order (Nu)
278
Classification of streams based on the number and type of tributary junction
279
constitutes an useful indicator of stream size, discharge and drainage area (Strahler,
280
1959). The number of streams (Nu) of each order (U) for the Nandakini basin is given in
281
detail in Table 1. The details of the stream characteristics confirm Horton‟s first law
282
(1945), i.e. “law of stream numbering” which states that the number of streams of
283
different orders in a given drainage basin tends closely to approximate an inverse
13
284
geometric ratio. It is evident that the total number of streams gradually increases as the
285
stream order decreases and vice-versa. The higher degree of variation as noticed in the
286
order and size of the tributary basin is largely due to the physiographic conditions of the
287
area. The higher number of the streams in the Nandakini basin indicates a juvenile
288
topography of the area and the topography is still under erosion.
289
4.1.4 Stream Length (Lu)
290
The stream length of all the sub-basins of various orders has been measured on
291
the Survey of India topographical maps. The stream length characteristics of the sub
292
basins conforms Horton‟s Second law (1945), “Laws of Stream Length”, which states
293
that the average length of the streams of each of the different orders in a drainage basin
294
tends closely to approximate a direct geometric ratio. The total stream length of the
295
Nandakini basin is 1,179.95 km, and the stream length of the sub-basins is given in detail
296
in Table 1.
297
4.2 Shape Parameters
298
4.2.1
Elongation Ratio (Re)
299
Schumm (1956), defined the term Elongation Ratio (Re) as the ratio between
300
the diameter of a circle of the same area as that of the basin (D) and basin length (L).The
301
Re is calculated by using the following formula:
302
Re = D/L = 1.128 √A /L
303
Where, A = area of the basin,
304
L = basin length and
305
1.128 is a constant
14
306
The Re of the Nandakini basin is 3.76. The values of Re for the sub-basins have been
307
shown in Table 1. These ratios indicate that Nandakini basin as well as all sub-basins are
308
elongated in shape.
309
It is possible that the variations of the elongated shapes of the sub-basins are controlled
310
by the effects of thrusting and faulting in the basin.
311
4.2.2
Circulatory Index (Rc)
312
The circulatory Ratio (Rc) is expressed as the ratio of the basin area (Au) to the
313
area of a circle (Ac) having the same perimeter as that of the basin (Miller, 1953;
314
Strahler, 1964) and it is expressed as:
315
Rc = 4 π A/ P2
316
Where Rc = the circulatory ratio,
317
4π = constant,
318
A = area of the basin and
319
P= perimeter of the basin
320
The ratio is more influenced by length, frequency (Fs) and gradients of streams of various
321
orders rather than slope condition and drainage pattern of the basin. It is in facts, a
322
significant ratio that indicates the dendritic stage of the basin. Its low, medium and high
323
values are indicative of the youth, mature and old stages of the life cycles of the tributary
324
basins (Sreedevi et al., 2004). The Rc of the Nandakini basin is 0.41, while the values of
325
the other sub-basins are given in Table 1.
326
4.2.3 Form Factor (Ff)
15
327
Horton (1945) introduced this parameter to predict the flow intensity of a basin of a
328
defined area. The Ff of a drainage basin is expressed as a ratio between the area of the
329
basin (a) and the squared of the basin length (L2), and expressed as:
Ff = A / L2
330
331
The Ff of the Nandakini basin is 0.23, while the Ff for the sub-basins are shown in the
332
Table 1.
333
4.3
334
4.3.1 Bifurcation ratio (Rb)
Derived Parameters
335
According to the Strahler (1964), the ratio of number of streams of a given order
336
(Nu) to the number of segment of the higher order (Nu+1) is termed as Rb and expressed
337
as:
338
Rb = Nu / Nu+1
339
In the Nandakini basin the mean Rb is 3.95 and varies from 2.00 to 7.83 (Table
340
1). After closely examining the two sides of Nandakini valley, the mean Rb has been
341
calculated for both the sides and it has been found that the mean Rb value for the left side
342
is 3.91, and for the right side is 3.99.
343
4.3.2
344
345
346
347
348
Stream Length Ratio (Rl)
The basin and sub-basin stream length ratios are calculated by applying the
following formula given by Horton (1945)
Rl = Lu / Lu-1
Where Rl = Stream length ratio
Lu = stream length of order u
16
349
Lu-1 = stream segment length of next lower order
350
The mean stream length ratio of the Nandakini basin has been found to be 0.76 while Rl
351
for other sub basins varies between 0.32 and 2.4 (Table 1).
352
Rl between successive stream orders varies due to difference in slope and topographic
353
conditions, and has an important relationship with the surface flow discharge and
354
erosional stage of the basin (Sreedevi et. al, 2004).
355
4.3.3 RHO Coefficient
356
357
358
Horton (1945) defined RHO coefficient as the ratio between the stream length
ratio (Rl) and the bifurcation ratio (Rb):
RHO = Rl / Rb
359
It is an important parameter that determines the relationship between the drainage density
360
and the physiographic development of the basin, and allows the evaluation of the storage
361
capacity of the drainage network (Horton 1945).
362
The mean RHO coefficient of the Nandakini basin is 0.20, while the RHO of the sub
363
basins is shown in Table 1.
364
4.3.4 Stream frequency (Fs)
365
366
Horton (1945) introduced the term stream frequency as the ratio between total
number of stream segments of all orders in a basin and the basin area:
367
Fs = ΣNu /A,
368
Where ΣNu =total number of stream segments of all orders,
369
A = area of the basin
17
370
The mean Fs of Nandakini basin is 3.74 km-2, while the Fs for all the sub-basins are
371
shown in Table 1.
372
373
374
4.3.5 Drainage Density (Dd)
375
376
Horton (1945) defined the drainage density (Dd) as the total length of streams per
unit area divided by the area of drainage basin and is expressed as:
377
Dd = ΣLt /A,
378
Where ΣLt = total length of all the ordered streams,
379
A = area of the basin
380
Dd is a measure of degree of fluvial dissection and is influenced by numerous factors,
381
among which resistance to erosion of rocks, infiltration capacity of the land and climatic
382
conditions rank high or (Verstappen, 1983). The density value less than 5 indicate the
383
coarse drainage which reveals permeable subsurface strata (Sreedevi et al., 2004). The
384
Dd of the Nandakini basin is 2.74 km-1 while the Dd for the sub-basins and the main sub
385
basin are shown in Table 1.
386
4.4
Drainage Texture (T)
387
The drainage texture (T) is an expression of the relative channel spacing in a
388
fluvial dissected terrain. It depends upon a number of natural factors such as climate,
389
rainfall, vegetation, rock and soil type, infiltration capacity, relief and stage of
390
development of a basin (Smith, 1950). The soft and weak rocks unprotected by
18
391
vegetation produce a fine texture, whereas massive and resistant rocks cause coarse
392
texture (Dornkamp and King, 1971). The drainage texture (T) is given by
393
T= Dd X Fs
394
Where Dd = drainage density,
395
Fs = stream frequency
396
Based on the values of T, the drainage texture is classified as (Smith, 1950):
397
Very Coarse
(>2)
398
Coarse
(2-4)
399
Moderate
(4-6)
400
Fine
(6-8)
401
Very Fine
(<8)
402
403
The T of Nandakini basin as a whole has been found to be 10.77, thus falling under “very
404
fine texture” as the values are greater than 8, while for the sub-basins values of T are
405
shown in Table 1.
406
407
5.
Lineament Analysis of the Nandakini River Basin
408
In the present work, features like ridge, valley structural alignments or river
409
courses have mapped to the direction pattern of lineament (Figure 14A), and their
410
azimuth were plotted to obtain their Rose diagram (Figure 14B). Lineaments have been
411
marked on the Satellite image and their directions noted in the ERDAS imagine software.
412
The Enhanced Thematic Mapper (ETM+) and Panchromatic (PAN) data of Landsat 7
19
413
have been used in the identification and marking of lineaments. The different spectral
414
bands were used to make false color composite (FCC) images. In the present study Band
415
2 (Green), Band 3 (Red) and Band 4 (Near infra-red) has been used to make FCC. The
416
merged PAN and FCC images of Landsat 7 gives very good resolution of 15 m, which is
417
very helpful in the delineation of lineaments in the study area. The 145 path and 39 row
418
of Landsat 7 image have been used in the present study.
419
Quantitative study of the lineaments of the Nandakini River Basin reveals that the
420
majority of them are confined in the NE-SW sector while a few are aligned almost NW-
421
SE.
422
423
6.
DEM and SRTM
424
A digital elevation model (DEM) is a digital representation of ground surface
425
topography or terrain. Generally it has been termed as a digital terrain model (DTM). The
426
accuracy of this data is determined primarily by the resolution (the distance between
427
sample points). Other factors affecting accuracy are data type (integer or floating point)
428
and the actual sampling of the surface when creating the original DEM. A DEM is
429
represented as a raster (a grid of squares) or as a mesh of triangular irregular network
430
(TIN). It generally refers to the representation of the earth‟s surface heights (or subset of
431
this), including natural and man made features, above the datum. The DEM often
432
comprises much of the raw dataset, which may have been acquired through techniques
433
such as photogrammetry, land surveying or from various satellite programmes.
20
434
A Digital Elevation Model of the Nandakini River Basin (Figure 15) has been
435
prepared from the Survey of India (SOI) toposheets of 1:50,000 scale on the
436
measurement made from the contours and their values. The study area lies between
437
3015‟ to 30 25‟N latitude and 7915‟ to 70 25‟E longitude. The contours were
438
digitized from the SOI toposheets in Arc View 3.2 and the measured interval of the each
439
contour was 40 m in the map. A contour map of the Nandakini River Basin (Figure 16)
440
has thus been prepared. In order to provide the elevation information for the DEM, a
441
Shuttle Radar Topography Mission (SRTM) map for the Alaknanda River Basin (Figure
442
17) has also been prepared. For a better interpretation of the morphometry, a slope map
443
of the area (Figure 18) has also been prepared.
444
The DEM shows coloured sloping elevation starting with the light bluish colour
445
that represents the lowest elevation of the area. The area is typically marked by the
446
presence of a number of streams. As the elevation increases, the topography changes
447
according to the heights and all these have been assigned by different colours like yellow,
448
green, orange, red, etc. with grey to white representing the maximum heights in the study
449
area.
450
451
7.
Terrain Characteristics: Insight from DEM and SRTM maps
452
The Nandakini River Basin lies between 3010‟ to 30 23‟N latitudes and 7918‟
453
to 79 48‟E longitudes. The river marks its origin from 30 19‟N latitude and 7944‟ E
454
longitude from the glaciated terrain of Nanda Ghoogti. Right from the point of origin, the
455
first order streams are seen very well exposed. From the origin, the river initially flows in
21
456
the N to S direction for about 5 km where it takes a 900 turn and then starts flowing in the
457
W to E direction. The whole basin, in general, is characterized by many upwarps and
458
downwarps as is well indicated in the DEM. The spatial distribution of the elevation data
459
of the Nandakini River in this region clearly shows that the region exhibits highly
460
variable contours suggesting that the region is highly susceptible to neotectonic activity.
461
In the upper part of the Nandakini River, the DEM is marked by higher values of
462
elevation in the N to S direction which continues for 5 to 6 km where there is a sharp fall
463
of 61m possibly suggesting some structural movement because from here the river
464
changes its direction from N-S to W-E until it debouches in the Alaknanda River. The
465
contours in this region are very dense and closely packed which is a direct evidence of
466
the steep slope of the terrain. Numerous smaller tributaries and streams can be seen
467
associated with the Nandakini River as soon as it changes its course form N-S to W-E.
468
Here the number of first order streams becomes significant because it suggests that the
469
denudational processes have increased and this has subjected the terrain to higher
470
erosional activity. Further it can also be said that due to the active tectonics in the
471
Himalayan region later on, the area has been opened to successive deformation. This in
472
turn may have developed a highly dissected nature of the terrain that imparts highly
473
undulatory elevations to the DEM.
474
The W to E movement of the Nandakini River is marked by swinging of the river
475
with significant bends and steep slopes at several points. Along the river valley, steep
476
slope is observed with higher angles and very small valleys that mark the different
477
colouration to the DEM. The streams of the first order that join the river are mostly
22
478
straight and linear thus reflecting the role of tectonics in their formation. This may be due
479
to the local tectonics but gives a clear indication for a larger tectonic activity as the
480
Himalayan region is known for neotectonic activities.
481
A number of smaller tributaries join the Nandakini River in the left bank, e.g.
482
Lamu Gad, Andharyi Gad, Goli Gadhera, Mani Gadhera, Pubgarh Gadhera, etc. An
483
interesting observation on these tributaries, as noticed in the DEM, is that the flow of all
484
these tributaries, i.e. SE to NW, is nearly parallel to each other and this can be considered
485
to constitute a set of parallel lineaments in the region. This is an important feature as it
486
suggests that the river flowing from W to E direction is subjected to a later linear
487
deformation in the SE-NW direction, indicating the release of stresses in the inclined
488
plane of deformation. The DEM in this respect projects a view of the linearity of the
489
streams and ridges that can be collectively said to impart to the elevation with respect to
490
the topography of the region. A similar view, as evident in the DEM, is also provided by
491
the smaller tributaries of the right bank, e.g. Tamin Gad, Lumuti Gad, Galphi Gad,
492
Bhoriya Gadhera, Peri Gadhera, Sik Gadhera, Ala Gadhera, etc., when when viewed from
493
the left bank. However, the direction of the stream flow in this case is from NE to SW.
494
Further, as the latter tributaries meet the Nandakini River, the inclination of the stream
495
steepness is similar to that of the left bank tributaries and the straightening of these
496
streams also follows the same trend.
497
Within the Nandakini Reserve Forest zone near Gankholi and Sutol, the
498
Nandakini River shows a typical meandering pattern within a narrow stretch of 7 to 8 km
499
in W to E direction. The troughs and sinks of the river, as developed due to its
23
500
meandering, are well marked in the DEM. The inclination of the stream is in the direction
501
from SE to NW with an inclination of 450 thus projecting a parallel set of linear elements,
502
or tectonic elements, in this section of the river. Here the valley of the Nandakini River
503
has broadened possibly due to the shifting and stretching of the valley in this realm that
504
might reflect lateral and inclined stresses of the region.
505
The highs and lows of the study area mainly depicts that the terrain is very rough
506
and the flat tops present in some parts indicate that the region has been weathered due to
507
heavy precipitation and various types of land-use practices by the inhabitants.
508
The DEM shows that in the SW part of the map, the terrain is marked by a sharp
509
and steep gradient that allows the Nandakini River to join the Alaknanda River with a
510
sloping direction towards NW–SE. Here, the straightening of the course of the Nandakini
511
is due to structural control (presence of the South Nandprayag Thrust in the near-by
512
area). The valley, though appear broad, is rather confined in this area but the total
513
gradient is highly sloping which is well reflected in the DEM. The Alaknanda River, as
514
indicated in the DEM, shows that the sharp turn near Chamoli could be a reflection of
515
adjustment of the river with the lithology and tectonics of the terrain.
516
The higher frequency of the first order stream in the entire basin could be the
517
result of neotectonic activity and/or deformation of the local settings and this enhances
518
the great role of the stresses prevailing in the region.
519
The undulating topography of the Alaknanda River is a reflection of the
520
presence of many smaller to medium level of rivers and nalas (smaller streams) which
521
flow either from NW to SE or from SW to NE directions. These are the regions which
24
522
have been mainly subjected to tectonic activities that prevail along the entire terrain of
523
the Alaknanda watershed.
524
Another major stream of the area, in addition to the Alaknanda and Nandprayag
525
Rivers, is Birahi Ganga sloping in NW direction and meeting the Alaknanda River with
526
almost a straight trend. The DEM also indicates that near the confluence point of the
527
Birahi Ganga with Alaknanda, there is a sharp fall in the elevation suggesting that the
528
region may have adjusted itself so as to mandate the higher relief of the region.
529
The grid of the numerous streams of smaller extent and intensity is well-marked
530
in the DEM suggesting that the area is subjected to high rate of erosion and weathering.
531
The general trend of these streams is dip towards the major streams of the study area.
532
These smaller units in the DEM mark a great impression as they are the building units
533
that show greater resemblance to the lithology and structural setup of the region. The
534
elevated regions of the DEM are unique as they are mainly the sites of the water divide.
535
These smaller units of the elevated portions of the DEM show differential levels in their
536
heights.
537
The entire terrain of the study area shows a rugged and highly undulating
538
topography with different lithotypes that can be inferred from the different shaded relief
539
of the DEM on the outcrop. It thus appears that the undulatory signature of the region is
540
due to the presence of varying lithology and their association with the tectonics that may
541
have played a vital role in controlling the elevation in terms of the spatial and temporal
542
variability.
543
25
544
8.
Rivers and Tectonics
545
8.1
River Valley Pattern
546
A river system is governed by many parameters like channel width and depth,
547
dissolved sediment load, suspended load, bed load, channel slope and sinuosity, flow
548
velocity, channel roughness, and many others. The delicate balance between all of these
549
parameters in a river system means that rivers are very sensitive to any kind of change;
550
therefore fluvial geomorphology has become an important tool in our understanding of
551
the ongoing active tectonics in an area. Study of the patterns of river and major streams
552
of the area reveal some irregularities that might reflect the influence of some active
553
tectonics. These irregularities in the river/stream patterns suggest some recent changes in
554
the otherwise normal flow patterns of the rivers/streams. These irregularities can thus be
555
considered as signatures of neotectonic activity in the study area. Two major
556
irregularities have been noticed in the Alaknanda and Nandakini rivers: (a) Right angle
557
turn, and (b) Straightness of the stream.
558
559
8.1.1 Right-angle Turns
560
There are some points in the study area, where the Alaknanda River suddenly
561
swerves nearly at right angles. In a Google Earth image (Figure 19), we have selected a
562
few points, shown as Block A, B, C, etc. where the Alaknanda and the Nandakini rivers
563
take almost right-angle turns. Blocks A,B,C,D are for the Alaknanda River, while Blocks
564
E,F,G,H are for the Nandakini River. Further, at about 500 m N of Nandprayag, the SE
565
flowing Alaknanda suddenly changes its flow towards N. All these sudden changes in
26
566
these river courses within such short distances could be related to some recent tectonic
567
movements.
568
In the study area, as we have mentioned earlier, the Alaknanda River constitutes
569
an almost N-S trending fault/fracture system which is affected by a later set of almost E-
570
W trending faults, as noticed at least 6 different spots. It is quite possible that this E-W
571
swing of the Alaknanda River is related to the development of a fault system along which
572
the river could find an easy passage to flow through. Thus, in the area the entire strip of
573
Alaknanda River could be considered to be under the influence of active tectonics.
574
8.1.2 Straightness of the streams
575
In the area there are certain sectors where both the Alaknanda and Nandakini
576
rivers follow a straight course (Blocks A and D). This sudden straightening of the river
577
course could possibly be linked to some faults. Several workers (e.g. Schumm, 1986)
578
have pointed out that sudden straightening of the river channel might indicate the
579
presence of a fault. In both the cases, i.e. Blocks A and D, the river valley also shows
580
sudden swings to E-W. It is therefore possible that there are at least two generations of
581
faults in the area in which the E-W fault system is relatively younger.
582
A general look at the overall geomorphological pattern of the Alaknanda and
583
Nandakini rivers (Fig. 19) as well as that of smaller steams reveals that the courses of the
584
rivers show swings or bends in several directions e.g. towards E, W, NW and SE. In
585
general, all these sudden swings could represent the signatures of some recent activities
586
of the fault systems.
587
8.2.1 Longitudinal Profile
27
588
Rivers are very sensitive to tectonically induced changes (e.g., varying uplift
589
rates, etc.) along their courses. Longitudinal profile (Figure 20 A,B) is an important
590
geomorphic tool to understand the signatures of neotectonics and other geological
591
perturbations in the underlying area (Hack, 1973; Seeber and Gornitz, 1983; Schumm,
592
1986; Rhea, 1993; Schumm, 1993; Merritts et al., 1994; Demoulin, 1998; Holbrook and
593
Schumm, 1999). In steady-state conditions, where rock uplift is balanced by river
594
incision, the form of the river profile may contain information on spatial variations in
595
rock uplift rate (Whipple and Tucker, 1999; Snyder et al., 2000; Kirby and Whipple,
596
2001; 2002). Alternatively, in transient conditions when rock uplift and incision rates are
597
not in equilibrium, departures from the expected longitudinal river profile can be used to
598
infer recent or ongoing tectonic activity (Burbank and Anderson, 2001; Kirby et al.,
599
2007; Oskin and Burbank, 2007). The fact that rivers are sensitive to tectonic forcing-
600
and hence are capable of recording spatial variations in rock uplift rates in their
601
longitudinal profiles- has been demonstrated in experimental studies (Ouchi, 1985) as
602
well as in studies on rivers in tectonic settings with known uplift rates (Merritts and
603
Vincent, 1989; Kirby and Whipple, 2001; Duvall et al., 2004).
604
In the present work, we have studied longitudinal profiles of two strike-parallel
605
(i.e. E-W) rivers- Nandakini and Birahi Ganga- as similar studies are lacking for the
606
Himalayan region. The longitudinal profiles are drawn by plotting elevation of the river
607
bed against their respective downstream distance. The elevation of river bed is
608
determined by contour lines crossing the river on 1:50,000 scale topographic maps. Both
609
these rivers are tributaries of the Alaknanda River and flow in almost E to W directions.
28
610
The profile of Birahi Ganga River starts at 4000 m and ends at 980 m, while that of the
611
Nandakini River starts at 3800 m and ends at 860 m. Both these rivers meet the
612
Alaknanda River. Longitudinal profile of the both rivers (Nandakini and Birahi Ganga)
613
shows an irregular curve with convex and concave surfaces, the concavity of which
614
increases towards the headwater area. The profile of the Birahi Ganga shows prominent
615
knick points at 15 m and 23.4 m, while the Nandakini River shows knick points at 31m
616
and 42 m in the downstream direction from origin. (A knick point is defined as a steep
617
region along a river profile and can vary in form from a single waterfall to a high-
618
gradient region extending for many kilometers).
619
When a river passes through zones of active tectonics, its longitudinal profile
620
shows perturbations. The most prominent and fundamental effect crossing a site of
621
deformation, is the upwarping in longitudinal profile of the river relative to average
622
valley gradient (Holbrook and Schumm 1999). The profiles of both the Nandakini and
623
Birahi Ganga rivers show convex upwarping in their middle part. It is an indicative of
624
tectonic activity in the form of upliftment or the presence of a fault zone across the course
625
of the river.
626
627
9.
Discussion
628
9.1
Evaluation of Morphometric Parameters
629
The morphometric analysis of the drainage basin of a river is a simple approach to
630
describe the various morphotectonic processes associated with the basin; this also helps
631
to compare the geomorphic attributes of different basins. The sub-basins of the Nandakini
29
632
River Basin are of third, fourth and fifth orders. All the sub-basins exhibit dendritic to
633
sub-dendritic drainage patterns. The morphometric data of sub-basins is summarized in
634
the Table 1. The implications of the various basic, derived and shape parameters of the
635
sub-basins, as presented above, is highlighted below.
636
The stream characteristics in general confirm Horton‟s first law (1945), i.e. “law
637
of stream numbers,” (Figure 21A) which states that the number of streams of different
638
orders in a given drainage basin tends closely to approximate an inverse geometric ratio.
639
The inverse relationship between stream order and stream number of all the rivers and
640
streams of the basin is shown graphically in the form of straight lines where log values of
641
stream numbers (Nu) and stream lengths (Lu) are plotted against their respective orders
642
(Figure 20). The plots clearly suggest that the total number of streams gradually increases
643
as the stream order decreases and vice-versa. The higher degree of variation in the order
644
and size of the tributary basins is largely due to the physiographic conditions of the area.
645
The higher number of the streams in the Nandakni basin indicates a juvenile topography
646
of the area and that the topography is still under erosion. The stream length
647
characteristics of the sub-basins confirm the Horton‟s second law (1945), i.e. the “laws of
648
stream length,” (Figure 21B) which states that the average length of streams of each of
649
the different orders in a drainage basin tends closely to approximate a direct geometric
650
ratio. This geometric relationship of all basins is shown graphically where log values of
651
stream lengths (Lu) are plotted against their respective orders. Most drainage networks
652
show a linear relationship with small deviations from a straight line (see Chow, 1964).
30
653
The bifurcation ratio is related to the branching pattern of drainage network. It is a
654
dimensionless parameter of the drainage basin controlled by drainage density, stream
655
entrance angles (junction angle), lithological characteristics, basin shape, and basin area.
656
The bifurcation ratio thus expresses the degree of ramification of drainage. The
657
bifurcation ratio of the Nandakini River sub-basins ranges between 9 and 2. Because of
658
chance irregularities, bifurcation ratio between successive pairs of orders differs within
659
the same basin even if a general observance of a geometrical series exists (Schumm,
660
1956). A bifurcation ratio greater than 5 indicates structurally controlled development of
661
the drainage network (Strahler, 1957). Most of the sub-basins of the Nandakini River
662
Basin show bifurcation ratios for different stream orders as greater than 5. This suggests
663
that in every sub-basin, development of drainage is strongly controlled by faults,
664
lineaments and other structural features.
665
The stream length ratio, an important morphometric parameter gives a general
666
idea of the relative permeability of the rock formations of the basin. The stream length
667
ratio between successive stream orders varies due to differences in slope and topographic
668
conditions, and bears an important relationship with the surface flow discharge and the
669
erosional stage of the basin (Sreedevi et al., 2005).
670
The RHO Coefficient determines the relationship between the drainage density
671
and physiographic development of a basin, and allows the evaluation of the storage
672
capacity of the drainage network (Horton, 1945). This parameter is influenced by
673
climatic, geologic, geomorphologic, biologic, and anthropogenic factors. The RHO of the
674
sub-basins of the Nandakini River varies from 0.04 to 0.80 (Table 1). The highest value
31
675
of RHO is shown by sub-basin No. 24 (0.8), suggesting that it will have higher
676
hydric/water storage during flood periods and it attenuates the erosional effects during
677
elevated discharge.
678
The stream frequency of the Nandakini River sub-basins ranges between 6.27
679
(sub-basin 22) and 0.25 (sub-basin 2). The lower values of stream frequency indicate
680
gentle ground slope while the higher values suggest steep ground slope in the basin.
681
The drainage density is the measure of the degree of fluvial dissection and is
682
influenced by numerous factors, among which resistance to erosion of rocks, infiltration
683
capacity of the land and climate conditions rank high (Verstappen, 1983). The drainage
684
density in the Nandakini River sub-basins ranges between 3.99 (sub-basin 18) and 1.71
685
(sub-basin 11). Higher drainage density may be due to the presence of impermeable
686
subsurface material, sparse vegetation and high relief of the basin.
687
The drainage texture (T) is an expression of the relative channel spacing in a
688
fluvial dissected terrain. It depends upon a number of natural factors such as climate,
689
rainfall, vegetation, rock and soil types, infiltration capacity, relief and stage of
690
development of a basin (Smith, 1950). The drainage texture can be defined in terms of
691
relative spacing of the drainage lines and includes drainage density and stream frequency.
692
The values of T are classified (Smith, 1950) below:
Very Coarse
(<2)
Coarse
(2-4)
32
Moderate
(4-6)
Fine
(6-8)
Very Fine
(>8)
693
The drainage texture of the Nandakini River sub-basins ranges between 24.29 (sub-
694
basin 18) and 0.72 (sub-basin 2). This suggests very coarse to very fine drainage
695
development in different parts of the Nandakini Basin. The mean drainage texture of the
696
Nandakini basin is 10.77 that suggests a very fine drainage texture for the Nandakini
697
Basin.
698
The shape parameters such as elongation ratio and circularity index indicate the
699
general shape of a basin. The values of elongation ratio vary from zero (highly elongated
700
shape) to unity, i.e. one (circular shape). Thus, the higher are the values of elongation
701
ratio, more is the circular shape of the basin and vice versa. The elongation ratio of the
702
Nandakini River sub-basins ranges between 0.41 (sub-basin 9) and 0.84 (sub-basin 3).
703
Thus sub-basin 3 is the most circular and sub-basin 9 is most elongate among all. This
704
also indicates that the areas with higher elongation ratio values have high infiltration
705
capacity and low runoff; low values are indicative of high erosion and sedimentation load
706
(Reddy et al., 2004).
707
The values of circularity index varies from zero (a line) to unity (a circle). The
708
higher are the values of circularity index, the more is the circular shape of the basin and
709
vice versa. The circularity index of the Nandakini River sub-basins ranges between 0.35
710
(sub-basin 9) and 0.82 (sub-basin 3). Values approaching 1 indicate that the basin shapes
33
711
are nearly circular and as a result, it gets scope for uniform infiltration and takes long
712
time to reach excess water at basin outlet; however this further depends on the existing
713
geology, slope and land cover (Reddy et al., 2004).
714
The form factor predicts the flow density of a basin of a defined area (Horton,
715
1945). It reveals that the basins with low form factor have less side flow for shorter
716
duration and high main flow for longer duration and vice versa (Reddy et al., 2004). The
717
form factor shows inverse relationship with the square of the axial length and a direct
718
relationship with peak discharge (Gregory and Walling, 1973). The higher values of form
719
factor in the sub-basins 3 and 22 indicate high side flow for longer duration.
720
9.2
Morphostructural Evolution
721
In the area, the trends of the major structural elements e.g. thrusts (North
722
Nandprayag Thrust and South Nandprayag Thrust) and fold axial planes (Nandprayag
723
synform and the megascopic folds of the sedimentary belt) are subparallel to each other
724
(ESE-WNW to NW-SE). At the same time, the flow directions of the major rivers, viz.
725
Nandakini and Birahi Ganga, also closely follow this trend. This possibly suggests that
726
the flow directions of these two rivers are structurally controlled. The Alaknanda River,
727
on the other hand, flows across the above structural trends as well as across the general
728
strike of the rocks of the area. As we have mentioned above, the western margin of the
729
Nandprayag Crystalline Zone is delimited by the Nandprayag Fault System, it is therefore
730
possible that the course of Alaknanda River has been tectonically controlled by the
731
Nandprayag Fault System.
34
732
In the light of our field studies, as described above, the area appears to be
733
neotectonically active as revealed by a number of features such as landslides, river
734
terraces, tilting of beds, triangular facets, etc. Some of these features are developed along
735
the Alaknanda River valley which closely follows the Nandprayag Fault System. This
736
fault system thus appears to be active at the present time. Our morphometric analysis of
737
the Nandakini River Basin also suggests that this basin is neotectonically active.
738
Longitudinal profiles of the Nandakini and Birahi Ganga rivers, both of which flow
739
almost parallel to each other, show a major break at 29 km in the Nandakini River and at
740
14 km in Birahi Ganga River from origin. All the three major tributaries of the Alaknanda
741
River, viz. Birahi Ganga, Nandakini and Pindar, flow from E to W direction from their
742
origin and suddenly change their course to NW-SE for a few km and again follow their
743
general E-W course; all these suggest that the above-mentioned breaks in their profiles
744
are expression of a regional fault which has increased the gradient of the river.
745
From above, it is can be said that the localization of the neotectonic features of the
746
area is closely related to the structural features of the rocks. Our structural studies
747
(Bhattacharya 1999; Bhadauriya et al. 2009; Sharma, et al. 2008) suggest that the area
748
has undergone at least three major deformational events. An early megascopic major
749
folding event with N-S to NNE-SSW compression was followed by at least two more
750
folding events with lesser intensities as the signatures of the latter two folding episodes
751
are generally noticed on the mesoscopic scales. These deformational events were part of
752
the Himalayan orogeny and their signatures are noticed in the various rock types of the
753
area. Development of the N-S trending Nandprayag Fault is a later event. This fault is
35
754
again affected by an E-W system of faults thus constituting the Nandprayag Fault
755
System. It is important to note that at Nandprayag not only the course of the Alaknanda
756
River follows this fault but is also strongly affected by this fault system including the E-
757
W trending faults. All these suggest that Nandprayag Fault System is genetically linked
758
to the development of the Alaknanda valley, and all these could be a Quaternary process.
759
Occurrence of the various neotectonic features in the entire area also could be linked to
760
this Quaternary process. All these indicate that the deformational processes that had
761
initiated during the Himalayan orogeny are possibly still going on and are presently
762
manifested by the neotectonic features developed in the study area. That the area is
763
regionally active, can also be gauged from the fact that it has witnessed two major
764
earthquakes measuring more than 6.0 on the Ritcher scale in the last decade only viz.
765
Uttarkashi earthquake (1991) and Chamoli earthquake (1999)
766
767
10.
Conclusions
768
(1)
A part of the Garhwal Himalaya has been studied for understanding the
769
relationship between the structural setting and neotectonic activities. A strike-parallel
770
river basin- Nandakini River Basin- has been selected because similar studies are lacking
771
for the Himalayan region. Our studies reveal that the major geomorphic features of the
772
study area are structurally controlled and are neotectonically active. Several evidences of
773
neotectonics such as landslides, river terraces, vertical down-cutting of the rivers, deep
774
gorges of rivers, triangular facets and tilting of beds, sudden changes in the river courses,
775
etc. have been noticed in various parts of the study area.
36
776
777
(2)
An important highlight of the geology of the area is that both the major rivers of
778
the area- Nandakini and Alaknanda – are tectonically controlled. The Nandakini River
779
follows the South Nandprayag Thrust for a large distance. Another major stream, Birahi
780
Ganga, follows a path parallel to the North Nandprayag Thrust. Both these rivers follow
781
the general strike of the rocks formations of the area. The Alaknanda River follows the
782
N-S trending Nandprayag Fault System, at least in the study area. Most of the structurally
783
disturbed areas are therefore also the locale of neotectonic activities, thus suggesting that
784
structural and neotectonic processes are related to each other.
785
786
(3)
The Nandakini River Basin has been subdivided into 27 sub-basins which are of
787
third, fourth and fifth orders. All the sub-basins exhibit dendritic to sub-dendritic
788
drainage pattern. The river shows abrupt changes in its course from its origin to the
789
confluence (with Alaknanda). The basin is associated with various neotectonic activities.
790
791
(4)
Morphometric analysis of the Nandakini River Basin indicates that it is an
792
elongate basin with an area of 542.12 km2. The basin length is 48.64 km. The stream
793
length characteristics of the sub-basins confirm Horton‟s Second law, i.e. “Law of Stream
794
Length”. The total stream length of the basin is 1,179.95 km, Circulatory Index (Rc) 0.41,
795
Form Factor (Ff) 0.23, Bifurcation ratio (Rb) 0.41, the mean stream length ratio (RI)
796
0.76, RHO Coefficient 0.20, the mean stream frequency (Fs) 3.74 km-2, and Drainage
37
797
density (Dd) 2.74 km-1. The Drainage texture (T) of the Nandakini basin as a whole has
798
been found to be 10.77, that falls under “very fine texture”.
799
800
(5)
Quantitative study of the lineaments of the Nandakini River Basin reveals that the
801
majority of them are confined to the NE-SW sector while a few are aligned almost NW-
802
SE.
803
804
(6)
DEM and SRTM maps prepared for the Nandakini River Basin help in unraveling
805
the terrain characteristics as well as the neotectonic behaviour of the basin. The DEM
806
indicates that the streams of the first order that join the river are mostly straight and linear
807
thus reflecting the role of tectonics in their formation. This may be due to the local
808
tectonics but gives a clear indication for a larger tectonic activity as the Himalayan region
809
is known for neotectonic activities. The higher frequency of the first order streams in the
810
entire basin could be the result of neotectonic activity and/or deformation of the local
811
settings and this indicates the great role of the stresses prevailing in the region.
812
813
(7)
A number of smaller tributaries join the Nandakini River from both the left and
814
right banks. The left bank tributaries flow from SE to NW and all are nearly parallel to
815
each other while those of the right bank flow from NE to SW and these are also parallel
816
to each other. All this can be considered to constitute a set of parallel lineaments in the
817
region. This is an important feature as it suggests that the river flowing from E to W
38
818
direction is subjected to a later linear deformation thus indicating the release of stresses in
819
the inclined plane of deformation.
820
821
(8)
The undulating topography of the Alaknanda River is a reflection of the
822
presence of many smaller to medium level rivers and streams that join the main river. The
823
traces of these rivers/streams are possibly the areas that have been mainly subjected to
824
neotectonic activities that prevail along the entire terrain of the Alaknanda watershed.
825
826
(9)
Patterns of rivers and major streams of the area occasionally show some
827
irregularities, mainly right angle turn and straightness; these irregularities might reflect
828
the influence of some active tectonics in the area. Sudden swings in the E-W direction in
829
the Alaknanda River could be related to some faults. In general, the swings or bends of
830
the rivers and streams in several directions (E, W, NW and SE) could represent the
831
signatures of recent activities of the fault systems of the area. Further, the longitudinal
832
profiles of the Nandakini and Birahi Ganga rivers show convex upwarping in their
833
middle parts thus suggesting tectonic activity in the form of upliftment or the presence of
834
some fault zone across the course of these rivers.
835
836
(10)
The present study thus clearly indicates that this part of the Himalaya is
837
neotectonically active. It is therefore possible that the processes of Himalayan
838
deformation that have started from the emplacement of the crystalline rocks over the
39
839
younger sedimentary belt, followed by a few episodes of intense deformation, during the
840
Himalayan orogenic cycles, are active even today.
841
842
843
Acknowledgements
844
ARB, PS and SNA express their sincere thanks to the Head of the Department of
845
Geology, University of Lucknow, for providing working facilities. For financial
846
assistance in the form of fellowships, YB and SKP thank CSIR, New Delhi, and PS
847
thanks University Grants Commission, New Delhi while SNA to the Department of
848
Science & Technology, Govt. of India, New Delhi. Dr. Alok Thakur, Oil and Natural Gas
849
Corporation, Nazira, Assam, and Mr. Pranay V. Singh, NHPC, Dhemaji District, Assam,
850
are thanked for his help in several ways.
851
852
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853
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854
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856
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861
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874
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875
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1001
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1002
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1004
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1006
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1007
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1008
674.
1009
1010
1011
1012
48
1013
1014
1015
1016
1017
Figure Caption Page
1018
Figure 1: Geological sketch map of the Himalaya (After Gansser 1964) showing location
1019
of area studied. A- Outer Himalaya, B- Lesser Himalaya, C- Greater Himalaya,
1020
D- Tethys Himalaya.
1021
1022
1023
1024
Figure 2: Geological Map of the Ramni-Wan area showing the distribution of various
lithological units of the area. (After Sharma, et al. 2010).
Figure 3: Geological section of the study area showing the structure of the area. MCTMain Central Thrust, NNT- North Nandprayag Thrust.
1025
Figure 4: An example of landslides in the study area. Loc. About 2 km N of Nandprayag.
1026
Figure 5: Development of river terraces in the study area. (A) Four terraces, T0, T1, T2,
1027
T3. Loc. 1.1 km SW of Sunla. (B) Four terraces, T0, T1, T2, T3. Loc. About 1.5
1028
km N of Nandprayag. (C) Three terraces (T0, T1, T2,). Loc. 500 m NW of
1029
Nandprayag. (D) River terraces at about 1.6 km SW of Sunla. A fault F-F is also
1030
developed in the area cutting across the terraces.
1031
Figure 6: (A) Three triangular facets A, B, C can be seen with apex angle of 920, 1020,
1032
730 respectively. It may seen that the apex line of B and C is not straight,
49
1033
possibly due to the effect of some later deformation. Loc. 1.6 km NW of
1034
Nandprayag. (B) A fault scarp can be seen on the bottom right corner of a
1035
triangular facet. Apex angle of this facet is 600. The trend of the fault scarp and
1036
trace A-A‟ of triangular facets are parallel to each other. Loc. 1.2 km north of
1037
Nandprayag.
1038
Figure 7: Shattering of rocks. Heaps of broken rocks can be seen all along the hill slopes.
1039
Figure 8: Sudden turn in the course of the Alaknanda River. Here the SE flowing
1040
Alaknanda River suddenly takes a sharp bend to flow almost towards N. At least
1041
three terraces are also seen developed along the right bank. Loc. About 500 m
1042
north of Nandprayag.
1043
Figure 9: Instability of slopes. One can notice that the trunks of the large trees are bent in
1044
the direction of the ground slope. Although this could be a soil creep, we
1045
consider this process as some manifestation of ground instability and hence of
1046
neotectonics also.
1047
Figure 10: Quaternary deposits showing tilting of beds. (A) Tilting of beds as seen on the
1048
right bank of the Alaknanda River. The beds have been tilted by 100 towards
1049
South. Loc. 500 m NW of Maithana. (B) Tilting of beds by 50 on the right bank
1050
of the Alaknanda River Valley. Loc. 1 km N of Langasu.
1051
Figure 11: Normal fault in the Quaternary Deposits. Loc. 1.9 km NE of Langasu.
1052
Figure 12: Quaternary deposits showing structures resembling ramp and flat. In the
1053
photograph AB represents flat, BC ramp and CD again the flat part. A structure
50
1054
resembling a fault-bend fold (EC) can also be seen in the photograph. Loc. 700
1055
m ESE of Langasu.
1056
Figure 13: Drainage Basin map of the Nandakini River Basin.
1057
Figure 14: (A) Lineament map of the Nandakini River Basin. Lineaments are drawn on
1058
merged ETM+ and PAN images of the Landsat 7 remote sensing image. (B)
1059
Rose Plot of the Lineaments.
1060
Figure 15: Digital Elevation Model (DEM) of the Nandakini River Basin.
1061
Figure 16: Contour Map of the Nandakini River Basin.
1062
Figure 17: Photograph showing Shuttle Radar Topographic Mission (SRTM) Data of the
1063
Study area.
1064
Figure 18: Slope Map of the study area.
1065
Figure 19: Google Earth image showing sudden changes in the flow directions of the
1066
major rivers of the area, mainly the right-angle turn and straightness of the
1067
rivers.
1068
1069
1070
Figure 20: (A) Longitudinal profile of the Birahi Ganga River. (B) Longitudinal profile of
the Nandakini River.
Figure 21: Plots to show the verification of Horton‟s laws for the various sub-basins of
1071
the Nandakini River Basin. A- First law of stream numbers, B- Second law of
1072
stream lengths.
51
Table
Table 1: Morphometric parameters of sub-basins of the Nandakini River Basin.
Stream order
Subbasin
. no.
N4
N1/N2
N2/N3
Bifurcation Ratio
N1
N2
N3
1
8
2
1
11
4
2
29
6
1
36
3
79
20
6
2
1
4
166
48
15
3
1
5
82
16
4
1
6
12
3
1
7
22
5
1
8
107
22
5
9
14
4
1
10
82
18
4
2
11
131
29
6
2
12
28
5
13
24
6
14
37
9
2
15
13
2
1
16
18
5
2
1
17
29
10
2
1
18
16
3
1
19
60
9
1
N5
Total
no. of
Strea
m
(Nu)
N3/N4
L1
L2
L3
2
5.62
1.10
4.83
6
17.67
108
3.95
3.33
3
2
233
3.45
3.2
5
3
103
5.12
4
4
16
4
3
28
4.4
5
135
4.86
4.4
19
3.5
4
1
107
4.55
4.5
2
1
169
4.51
4.83
3
1
34
5.6
1
31
4
49
4.11
4.5
16
6.5
2
26
3.6
42
20
70
6.66
1
1
20
25
6
2
1
21
106
18
5
2
22
12
2
1
23
79
17
4
24
8
2
1
25
4
2
1
1
1
Stream Length (Km)
N4/N5
L4
Length Ratio
L5
L4/L3
Mean
Rb
Mean
Rl
RHO
(Rl/Rb)
L2/L1
L3/L2
L5/L4
1.55
0.19
1.40
3.00
0.79
0.26
5.12
4.15
0.28
0.81
5.41
0.54
0.09
46.60
15.30
7.73
2.25
2.35
0.32
0.50
0.29
1.04
3.07
0.53
0.17
112.78
39.60
10.02
8.90
7.09
0.35
0.25
0.88
0.79
3.66
0.56
0.15
54.41
18.43
3.94
6
0.33
0.21
1.52
4.37
0.68
0.15
7.12
3.26
1.17
0.45
0.35
3.50
0.40
0.11
0.32
0.92
4.70
0.62
0.13
0.17
1.30
4.75
0.62
0.13
0.24
3.33
3.75
1.78
0.47
11.73
3.79
3.51
59.32
10.51
13.73
6.75
1.63
5.44
2
48.59
11.92
11.33
1.99
2.83
0.24
0.95
0.17
1.42
3.26
0.69
0.21
2
103.16
26.95
12.09
4.10
7.37
0.26
0.44
0.33
1.79
3.58
0.70
0.19
5
19.13
5.61
4.66
0.29
0.83
5.30
0.56
0.10
6
14.70
6.77
3.94
0.46
0.58
5.00
0.52
0.10
2
17.74
5.01
2.72
0.28
0.54
3.53
0.85
0.24
5.51
2.76
2.58
0.50
0.93
4.25
0.71
0.16
2.5
2
10.58
2.65
5.15
0.53
0.25
1.94
0.10
2.7
0.76
0.28
2.9
5
2
18.76
7.02
1.90
2.82
0.37
0.27
1.48
3.30
0.70
0.21
5.33
3
9.34
2.78
0.99
0.29
0.35
4.16
0.32
0.07
9
47.75
16.79
5.75
0.35
0.34
7.83
0.34
0.04
14.33
2.07
2.31
2.00
0.14
1.11
0.86
3.05
0.70
0.22
77.18
17.60
7.01
2.78
0.22
0.39
0.39
3.49
0.60
0.17
5.54
0.61
1.70
0.11
2.78
4.00
1.44
0.36
5
5.68
4.77
0.41
1.75
34
4.16
3
2
132
5.88
3.6
2.5
15
6
2
101
4.64
4.25
43.75
14.36
4.28
0.32
0.29
4.29
0.68
0.15
11
4
2
3.51
0.32
1.51
0.09
4.71
3.00
2.40
0.80
7
2
2
5.28
0.60
0.55
0.11
0.91
2.00
0.51
0.25
4
2
6.16
3.95
1.43
1.42
Total stream
length
Stream frequency
(Fs)
Drainage density
(Dd)
Texture
(T)
Basin Length
Form Factor
(Ff)
2.42
8.27
4.54
3.41
15.48
2.84
0.30
7.42
9.10
26.24
0.25
2.88
0.72
4.85
0.38
13.19
25.89
74.23
4.17
2.86
11.92
6.79
0.56
19.81
69.46
178.39
3.40
2.56
8.70
14.24
0.34
37.32
5
29.75
82.78
3.46
2.78
9.61
10.38
0.27
26.19
6
4.34
11.55
3.68
2.66
9.78
3.36
0.38
8.77
7
6.62
19.03
4.22
2.87
12.11
4.93
0.27
11.43
8
30.29
89.24
4.45
2.94
13.08
7.88
0.48
24.80
Subbasins
Area
(A)
1
2
3
4
Perimeter
(km)
9
5.38
13.82
3.53
2.56
9.03
6.16
0.14
13.72
10
32.73
76.66
3.26
2.34
7.62
11.29
0.25
28.93
11
89.73
153.67
1.88
1.71
3.21
16.22
0.34
43.58
12
13.45
29.40
2.52
2.18
5.49
5.91
0.38
15.46
13
12.41
25.41
2.49
2.04
5.07
5.13
0.47
15.06
14
13.08
30.24
3.74
2.31
8.63
6.30
0.32
17.47
15
5.49
10.85
2.91
1.97
5.73
4.76
0.24
11.00
16
9.97
18.91
2.60
1.89
4.68
4.82
0.42
13.07
17
12.09
30.50
3.47
2.52
8.74
5.10
0.46
14.29
18
3.28
13.11
6.09
3.99
24.29
2.68
0.45
7.28
19
19.29
70.29
3.62
3.61
13.06
7.52
0.34
19.00
20
5.63
20.71
6.03
3.67
22.13
4.65
0.26
11.23
21
35.33
108.52
3.73
3.07
11.45
10.52
0.31
27.23
22
2.39
7.85
6.27
3.28
20.56
2.16
0.51
7.31
23
22.11
68.55
4.56
3.10
14.13
9.46
0.24
23.83
24
1.93
5.32
5.69
2.75
15.64
3.14
0.19
6.03
25
2.31
6.43
3.03
2.78
8.42
2.80
0.29
7.02
Elongation
Ratio
(Re)
Circularity
Index
(Rc)
0.61
0.69
0.84
0.65
0.58
0.69
0.58
0.78
0.41
0.50
0.65
0.69
0.76
0.63
0.54
0.72
0.76
0.75
0.65
0.57
0.62
0.80
0.54
0.49
0.60
0.55
0.66
0.83
0.63
0.54
0.71
0.64
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0.54
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0.78
0.67
0.56
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0.56
0.49
0.67
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Figure Captions
Figure Captions
Fig.1: Geological sketch map of the Himalaya (After Gansser 1964) showing location of area studied. AOuter Himalaya, B- Lesser Himalaya, C- Greater Himalaya, D- Tethys Himalaya.
Fig.2: Geological Map of the Ramni-Wan area showing the distribution of various lithological units of the
area. (After Sharma, et al. 2010).
Fig. 3: Geological section of the study area showing the structure of the area. MCT-Main Central Thrust,
NNT- North Nandprayag Thrust.
Fig. 4: An example of landslides in the study area. Loc. About 2 km N of Nandprayag.
Fig. 5: Development of river terraces in the study area. (A) Four terraces, T0, T1, T2, T3. Loc. 1.1 km SW of
Sunla. (B) Four terraces, T0, T1, T2, T3. Loc. About 1.5 km N of Nandprayag. (C) Three terraces
(T0, T1, T2,). Loc. 500 m NW of Nandprayag. (D) River terraces at about 1.6 km SW of Sunla. A
fault F-F is also developed in the area cutting across the terraces.
Fig. 6: (A) Three triangular facets A, B, C can be seen with apex angle of 920, 1020, 730 respectively. It
may seen that the apex line of B and C is not straight, possibly due to the effect of some later
deformation. Loc. 1.6 km NW of Nandprayag. (B) A fault scarp can be seen on the bottom right
corner of a triangular facet. Apex angle of this facet is 600. The trend of the fault scarp and
trace A-A’ of triangular facets are parallel to each other. Loc. 1.2 km north of Nandprayag.
Fig. 7: Shattering of rocks. Heaps of broken rocks can be seen all along the hill slopes.
Fig.8: Sudden turn in the course of the Alaknanda River. Here the SE flowing Alaknanda River suddenly
takes a sharp bend to flow almost towards N. At least three terraces are also seen developed
along the right bank. Loc. About 500 m north of Nandprayag.
Fig. 9: Instability of slopes. One can notice that the trunks of the large trees are bent in the direction of
the ground slope. Although this could be a soil creep, we consider this process as some
manifestation of ground instability and hence of neotectonics also.
Fig.10: Quaternary deposits showing tilting of beds. (A) Tilting of beds as seen on the right bank of the
Alaknanda River. The beds have been tilted by 100 towards South. Loc. 500 m NW of
Maithana. (B) Tilting of beds by 50 on the right bank of the Alaknanda River Valley. Loc. 1 km N
of Langasu.
Fig.11: Normal fault in the Quaternary Deposits. Loc. 1.9 km NE of Langasu.
Fig.12: Quaternary deposits showing structures resembling ramp and flat. In the photograph AB
represents flat, BC ramp and CD again the flat part. A structure resembling a fault-bend fold
(EC) can also be seen in the photograph. Loc. 700 m ESE of Langasu.
Fig.13: Drainage Basin map of the Nandakini River Basin.
Fig.14: (A) Lineament map of the Nandakini River Basin. Lineaments are drawn on merged ETM+ and
PAN images of the Landsat 7 remote sensing image. (B) Rose Plot of the Lineaments.
Fig.15: Digital Elevation Model (DEM) of the Nandakini River Basin.
Fig.16: Contour Map of the Nandakini River Basin.
Fig.17: Photograph showing Shuttle Radar Topographic Mission (SRTM) Data of the Study area.
Fig.18: Slope Map of the study area.
Fig.19: Google Earth image showing sudden changes in the flow directions of the major rivers of the
area, mainly the right-angle turn and straightness of the rivers.
Fig. 20: (A) Longitudinal profile of the Birahi Ganga River. (B) Longitudinal profile of the Nandakini River.
Fig. 21: Plots to show the verification of Horton’s laws for the various sub-basins of the Nandakini River
Basin. A- First law of stream numbers, B- Second law of stream lengths.
Arab J Geosci
DOI 10.1007/s12517-010-0155-9
ORIGINAL PAPER
Is the recessional pattern of Himalayan glaciers suggestive
of anthropogenically induced global warming?
Rameshwar Bali & K. K. Agarwal & Sheikh Nawaz Ali &
Purnima Srivastava
Received: 19 June 2009 / Accepted: 1 December 2009
# Saudi Society for Geosciences 2010
Abstract Following the Intergovernmental Panel on Climate
Change report of 2001, a hype regarding the future of
Himalayan glaciers, flooding of Indo-Gangetic plains and
coastal areas and drying of glacially fed rivers has been created.
However, the recent studies of some of the Himalayan glaciers
indicate that the rate of recession of most of the glaciers in
general is on decline. These observations are in contradiction to
the widely popularized concept of anthropogenically induced
global warming. It is believed that the rise of temperature of
around 0.6°C since mid-nineteenth century is a part of decadal
to centennial-scale climatic fluctuations that have been taking
place on this Earth for the past few thousands of years.
Keywords Himalayan glaciers . Glacial recession .
Global warming . Climatic fluctuations
Introduction
The Himalayan region has one of the most spectacular
valley glaciers of the world. The glacial inventory carried
out by the Geological Survey of India reveals the existence
of over 9,000 valley glaciers in India and at least about
2,000 glaciers in Nepal and Bhutan (Raina 2006). Their
size ranges from small (e.g., 5-km long Pindari glacier in
R. Bali (*) : K. K. Agarwal : S. N. Ali : P. Srivastava
Centre of Advanced Study in Geology, Lucknow University,
Lucknow, India
e-mail: [email protected]
K. K. Agarwal
e-mail: [email protected]
S. N. Ali
e-mail: [email protected]
P. Srivastava
e-mail: [email protected]
Kumaun Himalaya) to very large (e.g., the 70-km long
Siachin glacier in the Kashmir and the 30-km long Gangotri
glacier in the Garhwal Himalayan region). Globally, it is
now being acknowledged that glacier regime is one of the
best repositories for understanding the ongoing climatic
changes. In spite of the Himalayan region having such huge
number of valley glaciers, very few glaciers of the Indian
subcontinent have been studied in detail so far. This is
mainly because of inaccessibility, as well as due to lack of
trained manpower. However, with the increase of scientific
awareness, infrastructural facilities, and more recently with
the availability of satellite data and GPS, emphasis is being
made to carry out high resolution studies of these glaciers.
Following the alarmist approach of the Intergovernmental
Panel on Climate Change (UN 2001), a number of reports
related with the bleak future of the Himalayan glaciers have
come up mainly through the media (Chengappa 2002;
Hasnain 2002). These suggest that almost all Indian glaciers
including the Gangotri glacier will vanish from this Earth in
next few decades. Initially, there would be flooding followed
by the drying of glacial fed rivers of Indian subcontinent,
desertification, rise of sea level, submergence of the coastal
areas, spread of diseases, drop in the production of food
grains, etc. (Hasnain 2002).
The Intergovernmental Panel on Climate Change (IPCC)
report has argued that such a chaotic situation to be
experienced by future generation is basically due to the
ongoing anthropogenically induced global warming (UN
2001). The human population on the planet Earth has been
increasing in exponential progression. There has been an
ever increasing industrialization and modernization in
different parts of the world. Direct and precise measurements of global temperatures suggest that the temperature
has been rising, more or less, since the 1850s, with a dip
from the 1940s to the mid-1970s. There has been an
average increase of around 0.6°C rise of temperature during
Arab J Geosci
the last 150 years or so (Jones and Moberg 2003).
Correspondingly, there has been a constant increase of
around 15 cm of sea level during past 150 years (Johnston
2002). The recent projections made regarding the future
climatic changes makes everyone believe that the twentieth
century warming has been unprecedentedly high and is
unique during the last millennium. The atmospheric CO2,
believed to be one of the important green house gases, has
been rising too. The computer modeling based on these
measurements makes one feel that with the current trend,
the Earth is very soon going to “Burn down.”
Such reports have in general been believed by the
common man, bureaucracy, policy makers and the politicians alike. A sense of insecurity and uncertainty over the
bleak future of Himalayan glaciers—the source of most of
the rivers of the fertile Indo-Gangetic plain has been
looming large in the minds of common man. The present
paper incorporates the results of the field studies carried out
by the authors as well as by other glaciologists, which very
firmly negate the alarmist views being put forward.
Past climatic changes
There is no doubt that the global temperature has risen by
about 0.6ºC during the last 150 years. The famous “Hockey
stick curve” (Mann et al. 1998; Mann et al. 1999; UN 2001)
has been plotted and predictions made regarding the future
climatic changes on the basis of measured values of
temperature. However, if one views the climatic fluctuations with an eye of a geologist or a palaeoclimatologist,
one does not get amused, but finds them to be relatively
very small changes that are comparable to the many that
have been taking place at regular intervals on this Earth.
Based on the geological records, it has been observed that
the climate on the planet Earth is and has been variable
ever since its birth. There have been periods of intense
glaciation (cooling) and interglaciations (warming) in the
geological past. The Earth has experienced more extreme
and hostile climatic fluctuations in geologic past as
compared to the one it is experiencing presently.
Three major periods of glaciation are recorded at around
600–700 million years, 280 million years, and during the
last 2 million years. Similarly, there have been periods of
warmer climate at around 400 million years and between
240 and 20 million years. Presently, the temperature is
almost 6°C less than what was 100 million years before.
The CO2 level too has come down appreciably (Marshak
2004). There have been appreciable temperature fluctuations as well as sea level changes. Large global glacial–
interglacial climate change oscillations have been recurring
at approximately 100,000 years periodicity for the last
900,000 years (Berger et al. 1993). Significant rapid
climatic change occurred during the Holocene interglacial
with cold and dry phases occurring on a 1,500-year cycle
(Adams et al. 1999). The last glaciation peaked about
18,000–21,000 years ago (LGM), with the ice sheets
retreating rapidly over just a few thousand years. There is
evidence that 9,000–10,000 years ago, glaciers in many
parts of the world were similar in size to those of today
(Kotlyakov et al. 1991). Surface temperatures were on an
average about 5°C lower than today, and much lower in the
polar regions. Through the last 10,000–11,000 years, we
have been in the Holocene interglacial, a warm episode
between the last glaciation and the next one, which will
likely occur in the near geologic future. At around 5,000–
6,000 years back (Holocene maxima) global temperatures
were warmer by at least 2°C. The Earth has been
experiencing regular warmer and cooler periods over the
past 4,000 years (Carter 2007 and Holland et al. 2007).
Palaeoclimatologists, after examining several climatic proxies argue and postulate that during the “Little Ice Age”
(1300–1850 AD), the planet experienced one of the coldest
periods in the last 1,200 years (Bradley et al. 2003). During
this episode, synchronous glacial advance occurred with
certainty in all the mountainous region, and this was a
major climatic event of the Holocene and not a minor
oscillation as believed earlier (Kotlyakov et al. 1991).
Before that, during the widespread Medieval Warm period
(1000–1300 AD), the different regions on Earth were around
1–3°C warmer than the present time (Villalba 1994; Soon and
Baliunas 2003). However, there were some offsets between
the intensity and timing and extent of warming in different
parts of the globe (Crowley and Lowrey 2000). Presently, we
are in a time of interglaciation and the present one has been
found to be less warm than the last four experienced during
the Late Quaternary times (Petit et al. 1999). It has also been
closely observed that the period between 20,000 and
13,000 years before present witnessed high-amplitude/lowfrequency climatic fluctuations between warmer and cooler
conditions in the Central Himalaya (Kotlia et al. 1997 and
Juyal et al. 2004). Palynological studies in the upper Spiti
region of Himachal Pradesh shows that since 900 years BP,
mountain glaciers and the tree line have descended and there
has been a return of cold climate. Earlier, between 1,500 to
900 BP, the climate changed to warm and most of which
resulted in the retreat of glaciers and shift of tree line towards
the higher elevation (Chauhan et al. 2000).
It has been observed that the warming in the Antarctica
began approximately 3,000 years before the onset of warm
period in the Greenland (Sowers and Bender 1995). Better
understanding of the nature of variability of South Asian
summer monsoon over the past 150,000 years shows that
there was warming during the Marine Isotope Stage (MIS)-3,
(60–25 ka before present). The greater monsoon precipitation
during MIS-3 compared to the time of LGM caused
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Himalayan glaciers to be more extensive during the former
time. This, along with the dating of the moraines in the
Garhwal Himalaya (Sharma and Owens 1996), further
suggests that the maximum extent of glaciation in Himalaya
occurred earlier than the worldwide LGM (Benn and Owen
1998; Owen et al. 2002). Thus, there has been a marked
difference in the timing and nature of glaciation in Himalaya
(located at higher altitudes and lower latitudes) compared to
that of polar regions (located at lower altitudes and higher
latitudes).
Causes for past climatic changes
A number of long-term and short-term causes have been
suggested for the climatic fluctuations experienced by the
Earth. The most significant ones include the relative change
in position of Earth with respect to the sun due to the
combined impact of eccentricity in Earth’s orbit around sun,
change in the tilt of Earth’s axis, and the wobbling action
due to precession (Milankovitch cycles; Marshak 2004),
regular fluctuations in the solar radiations or the sun spot
cycle, and change in albedo. The environmentalists blame
anthropogenically produced CO2 and other green house
gases for the increase of global temperatures. Emission of
CO2 due to anthropogenic activities has been cited to be
one of the major causes of rise of global temperature.
However, it has been suggested that water vapor constitutes
98% of all the green house gases (Patterson 2005). While
analyzing the Vastok (Antarctica) ice core samples, Petit et
al. (1999) have found that changes in temperature precede
change in CO2 concentration by about 400 to 4,000 years. The
circulation of the North Atlantic Ocean probably plays an
important role in triggering as well as amplifying rapid
climatic changes in the historical and recent geological records
(Jones et al. 1998). The centennial-scale abrupt change in the
monsoon variability has been attributed to the result of albedo
changes in the Himalaya and the Tibetan Plateau (Juyal et al.
2008). Nearly all the ice sheets were at their LGM positions
from 26.5 to 19 to 20 ka in response to decrease in northern
summer insolation, tropical pacific sea surface temperature,
and atmospheric CO2. The onset of northern hemisphere
deglaciation between 19,000 to 20,000 years was induced by
an increase in the northern summer insolation providing
source for an abrupt rise in sea level (Clarke et al. 2009).
of India, through the Department of Science and Technology,
launched a massive program for the study of few selected
glaciers. Since last 20 years, a number of National Institutes
and Universities have taken up studies related to different
aspects of glaciology of few selected Himalayan glaciers. The
recessional behavior of three glaciers viz. Gangotri glacier
(the largest in the Central Himalayan region), Dunagiri glacier
(medium size), and Pindari glacier (small glacier) are being
exemplified in Tables 1, 2, and 3.
It is observed that in Garhwal Himalaya, Gangotri
glacier (Raina 2003; Sharma and Owen 1996; Naithani et
al. 2001; Srivastava 2003), which was earlier receding at a
rate of around 26 m/year between 1935 and 1971 (Table 1,
Fig. 1), has shown a gradual decline in the rate of recession. It
has come down to around 17 m/year between 1974 and 2004
and lastly showed a recession of about 12 m/year during 2004
and 2005 (Kumar et al. 2008). The Dokriani glacier too has
maintained an overall constant rate of recession (around 16–
18 m/year) between the year 1962 and 1995 (Dobhal et al.
2004). Similarly, monitoring of the Pindari glacier in
Kumaun Himalaya by the authors suggested that the rate of
recession has come down to almost 6.5 m/year (Table 2,
Fig. 2) between 1966 and 2007 (Bali et al. 2009), as
compared to around 26 m/year between 1845 and 1906
(Tewari 1973). Milam glacier in the Goriganga valley,
Pithoragarh district has shown a rate of recession of around
16.5 m/year since last 150 years (Shukla and Siddiqui 2001).
The snout of Donagiri glacier has shown signs of moderate
recession along with intermittent advances (Table 3; Srivastava and Swaroop 2001; Swaroop et al. 2001). Similarly, the
Satopanth glacier, which had earlier been receding at the rate
of 22.86 m/year, has lately shown a recession rate of 6.5 m/
year during 2005–2006 (Nainwal et al. 2008).
Most conspicuously, the 70-km long Siachin glacier, too,
has been standing steady for the last several decades. The
snout has been almost stable and has even shown signs of
advancement during the last decade (Sinha and Shah 2008).
Recent studies have shown that the glacier has receded by
only 8–10 m between 1995 and 2008 (Ganjoo and Koul
2009). Recent studies by researchers at England’s Newcastle University also show consistent growth among the
glaciers of Karakoram, Hindu Kush, and Western Himalayan mountain ranges.
Table 1 Recession rates of Gangotri glacier (modified after Kumar et
al. (2008))
Behavior of Himalayan glaciers
Duration
(years)
Geologists from the Geological Survey of India have been the
pioneers of Himalayan glaciological research. Realizing that
the glacier regime is one of the best repositories for
understanding the ongoing climatic changes, the Government
1935–1971
1971–2004
2004-2005
Total recession (m)
Period (years)
Rate (m/year)
954.14
564.99
12.10±0.041
36
33
1
26.50
17.15
12.10
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Table 2 Annual variation in
snout of Dunagiri glacier
(modified after Srivastava and
Swaroop 2001)
Duration (years)
Recession (m)
Advance (m)
1985–1986
1986–1987
1987–1988
1988–1989
1989–1990
1990–1992
225
16,325
4,875
1,875
4,300
9,175
22,250
375
–
2,275
2,000
7,125
Discussion
The palaeoclimatological data of recent historical past derived
out of several proxies suggests that the appreciable temperature deviation during the Medieval Warm period and the Little
Ice Age were undoubtedly natural occurrences. That was a
time when there were no emissions of CO2 and other green
house gases and least interference of the humans with the
natural system.
Of late, the environmentalists have been alarmed by the rise
in global temperatures since mid-nineteenth century. A
geologist, on the other hand, has a broader perspective and
knows for sure that our planet has been much warmer in the
past. There are evidences that even around 9,000–10,000 years
before present, glaciers in many parts of the world were
similar in size to those of today. Also the climatic fluctuations
have not been uniform throughout the globe and that there
have been short-lived (decadal and century level) warming
and cooling phases (Crowley and Lowery 2000). Similarly,
there have been sudden decadal-scale climatic transitions
from cold events to warm periods and vice versa, even
during the Holocene at around 8,200, 3,800, and 2,600 years
BP (Adams et al. 1999). Even the CO2 levels during the
Holocene have been variable on a decadal to centennial
scale. It had reached the present day level of 380 ppm at
around 400 AD (Kurschner et al. 1996; Kouwenberg et al.
2005).
Following the famous “Hockey stick curve” (Mann et al.
1998 and Mann et al. 1999), a hype has been created by the
IPCC resolution (UN 2001), which suggests that we are in a
phase of anthropogenically induced global warming (Carter
2007). The United Nations’ graph for temperature change
for the past 1,000 years does not include the globally
Table 3 Recession rates of Pindari glacier
Duration (years)
Total recession (m)
Period
(years)
1845–1906
1906–1958
1958–1966
1966–2007
1600
1040
61
262
61
52
8
41
Rate (m/year)
26.23
20.00
7.62
6.39
Net area evacuated/occupied (sq. m)
+
−
−
+
−
−
22,025
15,950
4,875
400
2,300
2,050
recorded Medieval Warm period as well as the Little Ice
Age. This view seems to have been blindly followed and
carried forward in context to the melting of Himalayan
glaciers too. An undue sensation has been made in the
media, and the people in general have been made to believe
of the bleak future. However, the field monitoring of glacial
snout in the Central Himalayan region is not in correspondence with the above views (Sangewar 1998; Bali 2009). It
is very much evident from the above that the glaciers in the
Indian subcontinent, although are showing a recessional
trend in general, however, the rate of recession is steadily
coming down in most of the cases (Tables 1–3). They are
receding at a much slower pace in comparison to what they
were about a few decades back. The much talked about
Gangotri glacier, which has been accused of being on the
verge of extinction, still needs around 2,500 years to perish
at the current recessional rate. The glacial fed rivers are thus
not going to die an immediate death. The scientists who are
involved in the glaciological and hydrological studies,
however, point out that even at the foot hills, the
contribution of glacial melt water is only around 10–15%,
the rest being the rain and ground water. The glacial melt
and the snowmelt contribute maximum during the summer
time. Thus, even if a time comes that there are no glaciers
around, the rivers will still flow. The situation thus is in no
circumstances alarming. In addition to the above observations, the dendrochronological studies of the Western
Himalaya show that the first three decades of the eighteenth
century were warm with the warmest anomaly of (+) 0.52°C.
This was subsequently and closely followed by cooling (−)
0.58°C at the beginning of the second half of the eighteenth
century (Yadav et al. 1997). However, this reliable proxy data
provides no evidence of warming during recent decades
of the twentieth century that could be associated with
anthropogenic global warming (Yadav et al. 1999). In
fact, closer study reveals that the anthropogenic activities
are responsible for the recent decrease in minimum
temperature of the Western Himalaya (Yadav et al.
2004). Thus a number of proxy records reveal that the
twentieth century is probably not the warmest nor a
uniquely extreme climatic period of the last millennium
and that too has not been caused by global human impact
(Soon and Baliunas 2003). In fact Medieval Warm period
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Fig. 1 Recessional pattern of Gangotri glacier (simplified after Srivastava 2003)
has been considered to be a much warmer period than the
current warm period (Villalba 1990, 1994; Soon and
Baliunas 2003).
Lately, the hockey stick curve (Mann et al. 1998; Mann
et al. 1999) has been critically reviewed, and it has
gradually been acknowledged that this curve has been
Fig. 2 Recessional pattern of Pindari glacier (modified after Tewari
1973)
deduced using poor mathematical and statistical calculations (McIntyre and McKitrick 2003, 2005; Muller 2004).
Thus, the entire concept of anthropogenically induced
global warming of IPCC, on the basis of which melting
of Himalayan glaciers and future calamities for the Indian
subcontinent have been forecasted, is debatable.
Although one should not defend the environmental
degradation due to industrialization and other anthropogenic
activities. However, if anthropogenically produced CO2 is of
such critical importance to warming, then we have to think
deep as to why there was a large temperature rise prior to the
early 1940s, when 80% of the human produced carbon
dioxide was produced after World War II. For the past
1,000 years, CO2 has remained at 280 ppm. It started rising
due to industrial revolution and rose sharply in 1945.
However up to that time, the global temperature fell by
0.5% in the northern hemisphere. There was a time gap of
30 years in the increase of CO2 and rise of temperature
(Patterson 2005; Easterbrook 2008).
Predictions related to the future climatic changes are
largely based on the statistically developed general circulation models (GCMs). Diandong et al. (2007), using the
GCMs, have predicted an additional melting rate for the
glaciers of the Greater Himalaya for the period between
2001 and 2030. It has been suggested that the Himalayan
glaciers especially those below the 4,000 m altitude are
under a greater threat of rapid melting as compared to those
located at higher latitudes (polar regions). In reality, the
situation is the other way round where the polar glaciers
and the ice caps of Greenland and Antarctica are melting at
a faster rate than the Himalayan glaciers (Raina 2009). It
has thus to be kept in mind that we still lack knowledge on
the glacial interaction with the aerosols and that too for the
entire length of the Himalaya. It is also argued that the
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feared dust cover is likely to serve more as an insulator
rather than a conductor of heat (Raina 2009). Moreover, for
the Himalayan glaciers located in different microclimatic
zones from east to west, no generalizations can be made.
The statistically simulated GCMs lacking data on atmospheric feedback mechanisms are likely to end up with
biased results. They need to be validated before being
believed. It thus seems to be wiser to critically analyze the
field observations and try to correlate them with the
climatic changes of recent geologic past. It is most likely
that we are in a phase of decadal to centennial-scale lowamplitude/high-frequency climatic fluctuation that has
taken place on this Earth for the last few thousands of
years (Juyal et al. 2004).
It is likely that the present scale of warming (very small
as compared to those of the geological past) may not have
any serious impact on the Himalayan glaciers. In view of
the warming and insolation changes, glaciers in the
Himalaya may advance rather than retreat (Owen et al.
2002). The contradictions in the recorded recessional
pattern of Himalayan glaciers and the statistically generated
futuristic climatic models further bring extra responsibility
on the shoulders of earth scientists to precisely determine
the deviations being caused due to anthropogenic activity.
Long-term high resolution data are required for better
understanding and correlation of natural climate variability
and anthropogenic impact. These are all the more important
for climatically sensitive Himalayan region, which in turn
influences the regional and extra regional circulation
system (Prell and Kutzbach 1992; Singh and Yadav
2005). By observing the geological past with the eye of a
geologist and closely understanding the present behavior
and recessional pattern of Himalayan glaciers, it is more
logical to assign the current rise of 0.6°C temperature since
mid-nineteenth century, to global temperature cycle, rather
than accuse the mankind.
Acknowledgments The authors are thankful to the Head, Centre of
Advanced Study in Geology, Lucknow University for providing
infrastructural facilities. Grant from Department of Science and
Technology (DST) Project No. ESS/91/29/2004 is thankfully
acknowledged.
References
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Monitoring recessional pattern of Central Himalayan Glaciers:
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CORRESPONDENCE
Joshi and Upreti1 have not considered
published values of Himalayan glaciers
and have calculated their dates on the
basis of growth rate (without considering
the colonization delay), as calculated by
Hansen6 in a study of the Mittivakkat
Glacier on Ammassalik Island, South
East Greenland. According to him, the
average radial growth of Rhizocarpon
geographicum is about 12 mm/century or
0.2 mm/yr under optimum conditions in
the proglacier valley. The species is
rather indifferent as regards the aspect of
the rock facets in the study area.
According to Joshi and Upreti1, the
boulders located 1 km away from the
terminus of the glacier with lichen thallus
diameter ranging between 110 and
120 mm resulted in the calibration of
minimum age of exposure of the boulders as 550–600 yrs. According to the
values of colonization delay and growth
rate of the two Himalayan glaciers, as the
Pindari Glacier is also a part of it, the
dates of the lichens measured by them
turns out to be:
110/0.66 + 72 = 239, 120/0.66 + 72 =
254 yrs (according to the values
of Dokriani Glacier),
110/1 + 85 = 195, 120/1 + 85 = 205 yrs
(according to the values of Chorabari Glacier).
Since Pindari is also a south-facing glacier like the Chorabari Glacier, the dates
calculated by parameters of the latter
appear to be more correct compared to
the values for the Dokriani Glacier. This
suggests that the boulders of these
moraines are the part of second phase of
advance and retreat of the Himalayan
glaciers.
1. Joshi, S. and Upreti, D. K., Curr. Sci.,
2010, 99, 231–235.
2. Chaujar, R. K., Curr. Sci., 2006, 90(11),
1552–1554.
3. Chaujar, R. K., Curr. Sci., 2009, 96(5),
703–708.
4. Chaujar, R. K., In Proceedings of the
Seminar – 6th European Congress on Regional Geoscientific Cartography and
Information System, 2009, vol. 2, pp. 89–
92.
5. Winchester, V. and Chaujar, R. K., Geomorphology, 2002, 47, 61–74.
6. Hansen, E. S., Geogr. Tidsskr. Dan. J.
Geogr., 2008, 108, 143–151.
RAVINDER KUMAR CHAUJAR
Wadia Institute of Himalayan Geology,
Dehradun 248 001, India
e-mail: [email protected]
Dynamics of Pindari glacier during the last 600 years
A recent publication1 dealing with the
lichenometric study of Pindari glacier
suggests that the Pindari glacier has not
advanced since the last 600 years. This
has been inferred on the basis of growth
of lichen Rhizocarpon geographicum,
along a traverse from Babaji’s Kutia up
to Zero Point. We have been working on
the palaeogeographic reconstruction and
glaciogeomorphic evolution of Pindari
glacier area since the last three years.
Based on our field observations and relationships, we have established the chronology of glaciations in the Pindar valley
in time and space2. The article suggests
the presence of Pindari glacier at the
location of Babaji’s Kutia around 550–
600 yrs BP. On the contrary, our detailed
geomorphic studies aided with optically
stimulated luminescence and 14C dates
have helped in understanding the dynamics of Pindari glacier in time and space.
Our studies show that the Pindari glacier
had vacated the Lichenometric traverse
path1 long ago around 7.0 ka BP. The
misidentified moraines of Pindari glacier
(referred to as substrate) are in fact much
recent reworked glacial till material that
has been brought by the debris cones
coming out of the tributary hanging valleys.
Lichenometry, no doubt is a good tool
for determining the age of morainic
deposits3. However, one must have a
thorough understanding as to what we
are dating! In the present work1, the geomorphic disposition of the area has not
been considered. The authors inadvertently seem to have followed an earlier
terminology4 and have carried out their
studies on reworked glacial till material
of the tributary glaciers rather than the
moraine of Pindari trunk glacier. The inferences based on such studies are bound
to further complicate the issues of Himalayan glacier dynamics.
Our studies2 based on the presence of
set of recessional moraines in the Pindari
CURRENT SCIENCE, VOL. 99, NO. 10, 25 NOVEMBER 2010
trunk valley further show that the Pindari
glacier had advanced during the Little
Ice Age (around 400–500 yrs BP). Thereafter, it has been receding at a steady rate.
1. Joshi, S. and Upreti, D. K., Curr. Sci.,
2010, 99(2), 231–235.
2. Bali, R., Agarwal, K. K., Nawaz Ali, S.,
Rastogi, S. K. and Kalyan, K., In Indian
Science Congress, Thiruvananthapuram,
2010.
3. Awasthi, D. D., Bali, R. and Tewari, N. K.,
Spl. Publ. Palaeontol. Soc. India, 2005, 2,
201–206.
4. Rao, T. A., Bull. Bot. Surv. India, 1960, 2
(1 & 2), 61–94.
RAMESHWAR BALI*
S. NAWAZ ALI
Centre of Advanced Study in Geology,
Lucknow University,
Lucknow 226 007, India
*e-mail: [email protected]
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