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24. Last, W. M. and Vance, R. E., The Holocene history of Oro Lake,
one of the western Canada’s longest continuous lacustrine records.
Sediment Geol., 2002, 148, 219–238.
25. Wasson, R. J., Smith, J. I. and Agarwal, D. P., Late Quaternary
sediments, minerals and inferred geochemical history of Didwana
lake. Palaeogeogr. Palaeoclimatol. Palaeoecol., 1984, 46, 345–
372.
26. Sharma, S. et al., Late glacial and Holocene environmental
changes in Ganga plain, Northern India. Quat. Sci. Rev., 2004, 23,
145–159.
ACKNOWLEDGEMENTS. The work was carried out under a collaborative project of Geological Survey of India (GSI) and Department
of Geology, University of Delhi for which the Director General, GSI
and Head, Department of Geology, University of Delhi are acknowledged. We are grateful to J. K. Bhalla, Director, EPMA Laboratory,
GSI for facilitating this collaboration. U. K. Bassi, Dy. Director General,
GSI provided support and encouragement. Sheo Prasad, Director, GSI,
provided support, especially for work in the eastern sector. Thanks are
due to A. K. Bajaj, GSI, and Hemant Singh and Ajay Kumar, Department of Geology, University of Delhi for help in the field.
Received 23 August 2004; revised accepted 1 April 2005
Alluvial geomorphology and
confluence dynamics in the Gangetic
plains, Farrukhabad–Kannauj area,
Uttar Pradesh, India
N. G. Roy and R. Sinha*
Engineering Geosciences Group, Indian Institute of Technology,
Kanpur 208 016, India
Remote sensing images and topographic maps have been
used to understand the geomorphic processes in parts
of the Gangetic plains of Uttar Pradesh. Detailed geomorphic mapping suggests that the confluences of the
Ganga–Ramganga–Garra rivers have moved both upstream and downstream during the last 30 years in response to river capture, local cut-offs and aggradation.
There is a remarkable difference in the fluvial dynamics
of this region compared to the eastern Gangetic plains
from where rapid and frequent channel avulsions have
been reported. We do not observe any definite trend
in the movement of the confluence points and our work
departs from earlier suggestions of regional controls
such as choking up of rivers due to sea-level rise or increased erosion in the catchment areas.
THE Gangetic plains are the surface expression of the
Himalayan foreland basin and form one of the largest
areas of Quaternary sedimentation in the world. Running
*For correspondence. (e-mail: [email protected])
2000
roughly E–W, they cover varied climatic zones and are
underlain by complex subsurface geology with variable
tectonic history. These variations are remarkably manifested
in the surface geomorphology of the terrain and river systems. The morphological expression of the rivers in the
alluvial plains is related to their source area1; some rivers
are either braided (mountain-fed, e.g. Ganga, Brahmaputra) or
meandering (plains-fed, e.g. Burhi Gandak, Gomti) throughout their entire reach, while others show systematic variation
from braided to meandering from upstream to downstream
reaches (foothills-fed, e.g. Rapti, Baghmati). Rivers of the
western and southern Gangetic plains in Uttar Pradesh
(UP) show narrow active flood plains and are incised in
nature, whereas rivers of eastern Gangetic plains in north
Bihar have much wider flood plains and are not incised.
Such geomorphic diversity has been attributed to differences in stream power and sediment supply from the
catchment areas2,3. Besides the variation in geomorphology,
the dynamics of river systems also varies both spatially
and temporally. Several remote sensing-based studies have
been carried out in the Gangetic plains, which highlight fluvial dynamics in the eastern Gangetic plains of north Bihar4–8
as well as the western plains of UP9–11, albeit with significant variations in frequency and rates of migration. In
places, the shift of the river has been slow, gradual and
continuous, while in others, the change is rapid occurring at a
decadal scale (hyperavulsive rivers)7,8. In addition to the
migration of single-river systems, confluences of river systems have also shifted with time, although any definite
trend (upstream/downstream) as described by some workers10
may be unfounded. This communication presents a detailed
geomorphic investigation of the Ganga river and its alluvial
plains in Farrukhabad–Kannauj area of UP based on multitemporal analysis of remote sensing images (IRS LISS III
and Landsat) and maps with a view to understand the
landscape development and confluence dynamics.
The Farrukhabad–Kannauj area, located in the western
part of middle Ganga Plains (Figure 1), covers around
2756 km2 of area between 27°05′ and 27°33′N lat. and
79°25′ and 79°50′E long. The area is drained by the major
trunk river Ganga and its three tributaries, Ramganga, Garra
and Kali Nadi. The Ramganga and Garra flow southward
and take a SE turn just before joining the river Ganga.
The Kali Nadi flows southeast ward almost parallel to
Ganga and joins the Ganga further downstream.
Figure 2 shows a detailed geomorphic map of the area.
Based on the distribution of various geomorphic elements,
such as active and inactive channels, floodplains, waterlogged
patches and lakes, sand hills, etc. the terrain is divisible into
five major geomorphic units, namely (i) major active channel
belt, (ii) active flood plains of major channels, (iii) active
minor channels and flood plains, (iv) inactive minor
channels and floodplains, and (v) slightly dissected surface.
Present-day channel belt of the major rivers (Unit 1) of the
Ganga and Ramganga are distinctly braided, but the Ramganga shows significant sinuosity as well, particularly in
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reaches before its confluence with the Ganga. The Ganga
with a higher braiding index flows in nearly straight
reaches around Farrukhabad and a remarkable change in
flow direction occurs downstream of Fatehgarh from almost
NW–SE to nearly E–W trend down to its confluence with
the Garra river, after which it resumes its NW–SE trend. The
active flood plains of the major rivers (Unit 2) along both
banks of the Ganga and Ramganga are marked by sandy areas
having high reflectance and lower Normalized Difference
Vegetation Index (NDVI) values. The floodplain of the
Ganga is generally wider than that of the Ramganga, but
their widths vary significantly along the channel. At
places such as Fatehgarh, this unit is very wide, marked
by several abandoned threads of the multi-channel Ganga
river due to its movement towards southwest. Active minor channels and their flood plains (Unit 3) consist of a single meandering channel of relatively small width and its
associated floodplains characterized by relict fluvial features like abandoned channel, meander loops, etc. Among
the active minor channels, the sinuous Garra river is the
most important and is slightly migratory in nature. The other
two minor active channels, viz. Kali Nadi and Ramganga–
Gambhiri have not shown any migration or shifting of
their courses over the last 30 years. The Kali Nadi is encased in a much wider (28 times) valley with a much larger wavelength (11 times) than the present-day meander of
the Kali river (Figure 3 a). This river therefore provides an
example of a ‘misfit’ river12 (discussed later). A large part of
the study window is occupied by numerous inactive channels and flood plain features such as meander scroll bars,
cut-offs (both neck and chute cut-offs), and abandoned
Figure 1. Location map of study area showing major rivers and two
confluences, namely the Ganga–Ramganga (box W1) and Ganga–Garra
(box W2) which have been studied in detail.
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channel belts (Unit 4). In the NE part of the window, there
are a number of sand ridges, the origin of which cannot
be ascertained at this stage. The slightly dissected surface
(Unit 5) has been mapped mainly in the area south of the
Ganga river. This unit is generally featureless, except for
some isolated drainage lines and minor dissected areas parallel to both banks of the Kali river.
The description of the major geomorphic units follows our
earlier work in the adjoining Ganga–Yamuna interfluve
between Kanpur and Kalpi3,13,14 and some variations are
noted in the spatial distribution of the units. The Ganga river
flows in a much narrower valley in the study area compared
to the reaches downstream of Kanpur. Further, a major
difference is the absence of highly dissected badlands in
this region, which is particularly well-developed along the
Yamuna and Sengar rivers further south. It has been suggested that these badlands developed due to floodplain
degradation in response to the incision of major rivers
during latest Pleistocene and early Holocene14–16. Although
the Ganga river is also incised, the total incision (12–15 m)
is much less than in the Yamuna (> 30 m) to its south. Also,
the annual precipitation in the study area is ~ 200 mm
higher than in the southern Yamuna plains. We suggest
that such climatic variation and differential incision may
be responsible for a lesser degradation of the floodplains
in the Ganga plains.
As mentioned above, the study window shows a special
feature of the misfit channel of the Kali river. Further
analysis of this feature from the digital elevation model
shows that the palaeomeander is bound by 3–4 m high
valley wall all along and the Kali Nadi (2–3 m deep) is
encased in the valley (Figure 3 b). Using the relationship
between meander wavelength and bankfull discharge17
(Q/q = (L/l)2), the bankfull discharge of the former larger
stream (Q) works out to be 126 times higher than that of the
present-day Kali river (q). The ratios of wavelength, valley
width and bankfull discharges of the former stream and the
present-day Kali match closely with those of the misfit
rivers described from lowland England and USA17. Such
misfit or underfit channels have also been described from
north Bihar plains6, although they were interpreted to result
from avulsion events.
Geomorphic mapping clearly reflects that the area has
undergone significant channel movements. Two windows
were selected to study the fluvial dynamics for a period of
30 years (1970–2000), and special attention was paid on
the two confluences, namely the Ganga–Ramganga and the
Ganga–Garra. Figure 4 shows significant variation in plan
form geometry, position of channels and the exact location of
the Ganga–Ramganga confluence over the period of study.
Between 1970 and 1990, two large meanders developed in
the Ramganga river, and the one just upstream of its confluence with the Ganga was cut-off before 1990 (Figure 4 b),
thereby moving the confluence part upstream (from A to B).
The other meander in the upstream reach was also cut-off by
1998 and both cut-offs are easily picked up on the satellite
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Figure 2. Geomorphic map of the study area prepared from satellite image and Survey of India topographic sheets. Numbers 1–5 mark the distribution of geomorphic units as per the legend. Boxes W1 and W2 mark the Ganga–Ramganga and Ganga–Garra confluences respectively.
imagery of 1998 (Figure 4 c). These changes are well reflected
in the sinuosity variation of the Ramganga (Figure 5 a). The
Ganga has undergone minor changes between 1970 and
1998, moving slightly southward accompanied with an increase in braid-channel ratio18 (1.07 to 1.43; Figure 5 b). Between 1990 and 1998, the Ganga has moved further
southward leaving behind a wide belt of abandoned channels
and consequently moving its confluence point with the
Ramganga downstream to point C (Figure 4 c). Both rivers
show further increase in sinuosity as well as braid-channel
ratio between 1998 and 2000 (Figure 5 a and b), and the
confluence moved further downstream (point D).
Figure 6 shows the dynamics in the Ganga–Garra confluence region. The Ganga river shows significant change in
its plan form between 1970 and 2000 and its braid-channel
2002
ratio has decreased by about 20% during this period (Figure 5 b). There is no major change in the position of the
Ganga, except some movement within its multi-channel belt.
On the contrary, the Garra river not only shows significant
changes in sinuosity during the period (Figure 5 a), but also
shows interesting channel dynamics. Between 1970 and 1990,
the Garra river shows a dominant southeast movement
accompanied by increase in sinuosity and a downstream
shifting of its confluence with the Ganga (Figure 6 b).
The river was running nearly parallel to the Ganga in 1990.
Between 1990 and 1998, the Ganga ‘captured’ a part of the
Garra, developing a short-lived anabranch and a large island
(Figure 6 c). As a consequence, the Ganga–Garra confluence effectively shifted ~ 8 km upstream (from H to J).
The flow of the Ganga was clearly divided at point J as
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a
b
148
146
A
A’
Former meander valley
144
B’ L/l=13
B
142
140
W/w=28
Q/q=126
Kali Nadi
138
0
1
2
3
4
5
6
7
8
9
10 11 12
Distance (km)
Figure 3. a, Kali river, a tributary of the Ganga provides an example of ‘misfit’ river. Note the encased channel in a much wider valley. b, Crossprofile across the line AA′ shown in (a). Ratios of wavelength, width and bankfull discharge of the former larger channel (L, W, Q) and the presentday Kali channel (l, w, q) are also listed.
well, perhaps due to coalescence of channel bars. Between
1998 and 2000, however, the Ganga became confined to its
main channel (nearly the 1970 course). The Ganga river
developed a small meander just upstream of the confluence,
which shifted further upstream to point K (Figure 6 d).
It may be worthwhile here to point out the differences
in river dynamics in the region with that of the eastern
Gangetic plains from where rapid and frequent avulsions
on a decadal scale have been reported in the large rivers
such as the Kosi4 and Gandak19, as well as smaller interfluve rivers such as Baghmati7,8 and Burhi Gandak5. These
avulsions have been considered to have been triggered by
neotectonic movements, regional subsidence and local
sedimentological adjustments. On the contrary, rivers draining
the western Gangetic plains have witnessed local cut-offs
and river capture through minor avulsions, as evidenced from
surface geomorphology. Although the effects of Holocene
tectonic movements20 and tilting cannot be ruled in this
region, we need to test this through a more rigorous analysis
of elevation data, basement configuration and subsurface
faults.
The confluence dynamics in the region is intricately related
to the local movements of the channels in the confluence
region in response to fluctuation in water and sediment
budget. Although a net upstream or downstream migration
can be inferred over a period of time, it is apparent that
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there is neither any definite trend nor any synchronicity
and the confluence points have repeatedly moved both
upstream and downstream. In fact, opposite trends are
noted at the two confluence points in the study window
during the period of study. A simple mechanism which
effects the upstream migration is an increase in sinuosity
of one of the channels near the confluence and then a cutoff, for example, the Ganga–Ramganga confluence between
1970 and 1990 (Figure 4 a and b). Another mechanism which
frequently operates is the ‘river capture’ by lateral bank
erosion and migration. The major river encroaches and
beheads the smaller river thereby shifting the confluence
position upstream, as has happened in the case of the
Ganga–Garra confluence between 1990 and 2000 (Figures
6 and 7 a). A similar example has been reported in the Rapti
river, east of the study area, where the Rapti captured the
river Bhakhla between 1959 and 1974 due to a large-scale
avulsion upstream11.
The downstream migration of the confluence point in most
cases appears to be related to aggradation in the confluence
area and local avulsions of the primary channel in a multichannel system. Such a process is evident in the Ganga–
Ramganga confluence between 1990 and 2000 (Figures 4
and 7 b). We speculate that these processes are the manifestation of local fluctuations in water and sediment budget. An
increase in water budget increases the power to erode its
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Figure 4. Reconstruction of the dynamics of the Ganga–Ramganga confluence for the period 1970–2000 (a through d).
Points A through D mark the positions of the confluence during different times.
b
Figure 5. Temporal variation of sinuosity (a) and braid channel rivers (b) of the major rivers in the two windows, W1 and W2. G, Ganga; RG,
Ramganga; GR, Garra.
2004
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Figure 6. Reconstruction of the dynamics of the Ganga–Garra confluence for the period 1970–2000 (a through d). Points F through K mark the
positions of the confluence during different times.
a
b
Figure 7. a, A true colour composite of the Ganga–Garra confluence showing river capture of the Garra by the Ganga. b, A False Colour Composite of
the Ganga–Ramganga confluence showing the aggradational area in the confluence causing avulsion of the Ganga.
bank, produces cut-offs and encourages local capture. An
increased sediment budget due to bank erosion in the upstream reaches would encourage aggradation in the confluence area downstream due to reduced velocity and
gradient. Local channel–floodplains adjustment may cause
CURRENT SCIENCE, VOL. 88, NO. 12, 25 JUNE 2005
switching of channels away from the confluence point,
thereby moving the confluence point downstream. Such
degradational and aggradational regimes may alternate in
a large river system such as the Ganga, and this may explain
the opposite trends of migration (upstream and down2005
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stream) of the two confluences studied. This explanation
also negates the earlier belief that the major confluences
in the Gangetic plains have been migrating upstream due
to the choking of rivers with sediments in response to increased erosion in the Himalayan catchment and base
level changes due to sea-level fluctuations during Late
Pliestocene–Holocene10,21. We believe that this is a simple
morphological adjustment to local gradient and hydrological
fluctuations, and no regional interpretation may be sustainable. On a longer timescale, hydrological changes induced by climatic changes in the late Quaternary would
produce more significant movements of the confluence
points in a similar manner. The existence of the misfit
channels of the Kali river, several meander scars in inactive
flood plain unit both in south of the Ganga and east of
Garra (Figure 2), vouch for hydrological changes in the past.
In the vicinity of the confluence, the repeated movements
of the channels should cause interfingering of the deposits
of the adjoining rivers. Additional data, sub-surface stratigraphy, accurate elevation models, and mechanisms related to adjustments of stream junction angle would be
necessary to test the validity of our model on a long-term
basis and our ongoing work is focussed on some of these
issues.
1. Sinha, R. and Friend, P. F., River systems and their sediment flux,
Indo-Gangetic plains, northern Bihar, India. Sedimentology, 1994,
41, 825–845.
2. Jain, V. and Sinha, R., River systems in the Gangetic plains and
their comparison with the Siwaliks: A review. Curr. Sci., 2003, 84,
1025–1033.
3. Sinha, R., Jain, V., Prasad Babu, G. and Ghosh, S., Geomorphic
characterization and diversity of the fluvial systems of the Gangetic
Plains. Geomorphology, 2005, 70.
4. Wells, N. A. and Dorr, J. N., Shifting of the Kosi river, northern
India. Geology, 1987, 15, 204–207.
5. Philip, G., Gupta, R. P. and Bhattacharya, A., Channel migration
studies in the middle Ganga basin, India using remote sensing. Int.
J. Remote Sensing, 1989, 10, 1141–1149.
6. Sinha, R., Channel avulsion and floodplain structure in the Gandak–
Kosi interfan, north Bihar plains, India, Z. Geomorphol. N.F.
Suppl., 1996, 103, 249–268.
7. Jain, V. and Sinha, R., Hyperavulsive-anabranching Baghmati river
system, north Bihar plains, eastern India. Z. Geomorphol., 2003,
47/1, 101–116.
2006
8. Jain, V. and Sinha, R., Fluvial dynamics of an anabranching river
system in Himalayan foreland basin, Baghmati river, north Bihar
plains, India. Geomorphology, 2004, 60, 147–170.
9. Hedge, M., Mathur, V. K. and Mandal, P. S., Erratic meander shift
of the river Ganga at Kanpur. In Proc. Third International Workshop on Alluvial River Problems, Oxford and IBH, New Delhi,
1989, pp. 239–246.
10. Tangri, A. K., Satellite remote sensing as a tool in deciphering the
fluvial dynamics and applied aspects of Ganga Plain. In Gangetic
Plain: Terra Incognita (ed. Singh, I. B.), Geology Department,
Lucknow University, 1992, pp. 73–84.
11. Richards, K., Chandra, S. and Friend, P., Avulsive channel systems: Characteristics and examples. In Braided Rivers (eds Best, J.
L. and Bristow, C. S.), Geol. Soc. London, Spl. Pub., 1993, vol. 75,
pp. 195–203.
12. Dury, G. H., Tests of a general theory of misfit streams. Inst. Br.
Geogr., Trans. Pap., 1958, 25, 105–118.
13. Sinha, R., Khanna, M., Jain, V. and Tandon, S. K., Mega-geomorphology and sedimentation history of parts of the Ganga–Yamuna
plains. Curr. Sci., 2002, 82, 562–566.
14. Gibling, M. R., Tandon, S. K., Sinha, R. and Jain, M., Modern interfluves and their expression in the Late Qaternary record of the
southern Gangetic Plains. J. Sediment. Res., 2005, 75, 373–389.
15. Srivastava, P., Singh, I. B., Sharma, M. and Singhvi, A. K., Luminescence chronometry and Late Quaternary geomorphic history of
the Ganga Plain, India. Paleogeogr. Paleoclimatol. Paleoecol.,
2003, 197, 15–41.
16. Tandon, S. K. et al., Alluvial valleys of the Gangetic Plains, India:
Causes and timing of incision. SEPM Spl. Vol. (in press).
17. Dury, G. H., Contribution to a general theory of meandering valleys.
Am. J. Sci., 1954, 252, 193–224.
18. Friend, P. F. and Sinha, R., Braiding and meandering parameters.
In Braided Rivers (eds Best, J. L. and Bristow, C. S.), Geol. Soc.
London Spl. Pub., 1993, vol. 75, pp. 105–111.
19. Mohindra, R., Parkash, B. and Prasad, J., Historical geomorphology
and pedology of the Gandak megafan, Middle Gangetic plains, India.
Earth Surf. Process. Landforms, 1992, 17, 643–662.
20. Parkash, B., Kumar, S., Someshwar Rao, M., Gori, S., Suresh Kumar,
C., Gupta, S. and Srivastava, P., Holocene tectonic movements
and stress field in the western Gangetic plains. Curr. Sci., 2000,
79, 438–449.
21. Singh, I. B., Sedimentological history of Quaternary deposits in
Gangetic Plain. Indian J. Earth Sci., 1987, 14, 272–282.
ACKNOWLEDGEMENTS. We thank the Director, UP Remote Sensing
Application Centre for allowing us to use the archive of remote sensing
images.
Received 17 September 2004; revised accepted 5 January 2005
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