Quaternary International 227 (2010) 81e86
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Quaternary International
journal homepage: www.elsevier.com/locate/quaint
Shallow sub-surface stratigraphy of the Ganga basin, Himalayan foreland: Present
status and future perspectives
R. Sinha a, *, S.K. Tandon b, M.R. Gibling c
a
Engineering Geosciences Group, Indian Institute of Technology Kanpur, Kanpur 208018, India
Department of Geology, University of Delhi, Delhi 110007, India
c
Department of Earth Sciences, Dalhousie University, Halifax NS, B3H 3J5 Canada
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 15 July 2010
The Ganga basin in northern India is one of the world’s largest fluvial basins and has attracted enormous attention from earth scientists across the globe with a view to understanding large river
processes and landforms. Despite the scarcity of hydrological data from the Ganga basin, some
important studies have been carried out in the last several decades. However, the unavailability of deep
sections in this vast alluvial tract has always limited understanding of the sub-surface stratigraphy of
these plains. During the last decade, some important developments have taken place in integrating
exposed cliff section data with the drill cores in pre-defined transects and with targeted geophysical
investigations. Additionally, new areas of the basin have been studied for understanding landscape
evolution including the effects of active tectonics. This special issue of Quaternary International
highlights some of these developments from the stratigraphic archives of this large basin. This
collection of papers covers a wide gamut of subjects including terrace development in the frontal parts
of the Ganga basin, resistivity-based mapping of sub-surface stratigraphy, micromorphology of soils
from plains drill-core samples, historical-scale avulsion of large dynamic system such as the Kosi,
active tectonics and landform development in southern Ganga plains and finally some policy issues for
management of dynamic river systems. This introductory paper provides a background and present
status of research in the Ganga basin. It attempts to summarise some of the recent research developments in the Ganga basin research and highlights the unresolved issues, some of which have been
addressed through the contributions in this special issue.
Ó 2010 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction
In order to improve our understanding of large river basins,
a holistic approach is necessary, an approach that relies on multidisciplinary analysis and synthesis of surface and sub-surface data
that includes geological, geophysical, pedological, mineralogical,
geochemical, mineral magnetic and geomicrobiological results. The
Ganga basin of northern India contains several kilometres of alluvial strata and constitutes one of the world’s most extensive alluvial
plains e home to hundreds of millions of people, mostly dependent
on agriculture. The plains constitute a fluvial region traversed by
large rivers such as the Ganga (length: 2510 km; catchment area
980,000 km2) and Yamuna (length 1376 km; catchment area
366,223 km2) that are sourced in the Himalayan orogen, as well as
rivers such as the Betwa, Chambal, Ken, and Son that are sourced in
* Corresponding author. Tel.: þ91 5122597317.
E-mail address: [email protected] (R. Sinha).
1040-6182/$ e see front matter Ó 2010 Elsevier Ltd and INQUA. All rights reserved.
doi:10.1016/j.quaint.2010.07.015
the central Indian Craton. Additionally, many smaller plains e fed
rivers are sourced within the plains. The Ganga plains are of great
significance as they constitute an important link now and during
the earlier Quaternary between the Himalayan Orogen and the
Indian Ocean. Additionally, understanding the landforms of the
Ganga Plains e their origin, development and dynamic imprints e
is of critical significance to plan effectively for sustainable development of the region. For comprehensive future strategies for
utilization of the Ganga plains resources, it is necessary to study the
plains to track changes in the alluvial landscape on different time
scales e for example decadal, century, millennial and higher order
time scales of 104e105 years. Multiple approaches must be adopted
that combine modern process studies, Holocene environmental
change, and alluvial stratigraphic development in the shallow subsurface (w100 m depth).
Evolutionary history of most landforms (mega- and mesoscale)
in the Ganga Plains remains poorly understood because of the
methodological difficulties associated with the study of sub-surface
deposits. This aspect, notably the general non-availability of sub-
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R. Sinha et al. / Quaternary International 227 (2010) 81e86
surface geological data and drill cores, has been a serious impediment in elucidating the history of alluvial plain sedimentation. The
Department of Science and Technology (DST), Government of India
initiated a research programme on the Science of Shallow Subsurface (SSS) in 2005 with the objective of developing strategies
and a data base for the shallow sub-surface zone of different parts
of India. This was an outcome of the long-felt realization that major
Indian river basins and deltas that support extensive agricultural
activities should be studied on a priority basis. A coordinated multidisciplinary program in several major river basins has emphasized
the evolutionary history of mega- and mesoscale landforms that
require an integration of surface and sub-surface data. This special
issue of Quaternary International focuses on the Ganga basin and
presents a collection of papers dealing with new approaches to
understand shallow sub-surface stratigraphy, surface processes and
the integration of the two.
This special issue is dedicated to Arthur Geddes who was
a Professor in Geography at Edinburgh, UK and contributed
significantly to the advancement of physical as well as human
geography. He produced one of the first detailed geomorphic maps
of the Ganga plains along with topographic contours of the
monotonously flat plains (Geddes, 1960). These maps provided the
first perception of the major landscape elements of these plains. He
described a series of ‘cones’ and ‘intercones’ across the entire
Gangetic plains. Although the terms cones and intercones have now
been replaced by fans and interfans in the geomorphic literature,
the identification of these landscape-scale elements in the plains
was an important development which later led to more systematic
investigations of these areas not just in terms of geomorphology
and landscape development but also in terms of understanding the
alluvial stratigraphy below these plains. The following sections
highlight some of the important recent developments in Ganga
Basin research.
2. Ganga basin research e where do we stand?
Academic interest in the Ganga basin has been focused along
four major lines; (a) sediment discharge budgets (e.g., Metivier,
1999), (b) description of the geomorphic and sedimentologic
features (e.g. Geddes, 1960; Sinha and Friend, 1994; Singh, 1996), (c)
geophysical prospecting to describe the sub-surface mainly for
hydrocarbon exploration (e.g., Sastri et al., 1971; Raiverman et al.,
1983), and (d) alluvial stratigraphic development (Gibling et al.,
2005; Sinha et al., 2007, 2009). Fluvial geomorphology, sedimentation history and basement tectonics associated with the basin
were discussed extensively through to the 1990s (Geddes, 1960;
Sastri et al., 1971; Joshi and Bhartiya, 1991, Raiverman et al., 1983;
Sinha, 1995; Singh, 1996).
In tackling the complex geomorphic organization of the Ganga
basin drainage, a fundamental point is the recognition of distinct
types of fluvial system, each characterized by different source area
characteristics, viz. mountain-fed, foothills-fed and plains-fed
(Sinha and Friend, 1994). Each of these “systems” has characteristic
geomorphic ‘units’ and these units themselves consist of different
geomorphic ‘elements’. The mountain-fed rivers such as the Ganga,
Gandak and the Kosi (Fig. 1) act as efficient conduits for the
transport of a great quantity of sediments, derived from their
source areas of high relief, and consequently form large depositional areas (fans, in some cases) in the plains. The foothills-fed (e.g.
Baghmati, Rapti) and plains-fed (e.g. Burhi Gandak, Gomati) rivers
drain the interfan areas and derive their sediments partly from the
foothills and mostly from within the plains, and a large proportion
of this sediment is deposited back into the plains after local
reworking. The interfan areas, therefore, essentially consist largely
of overbank sediments and represent mud-dominated intervals in
the Quaternary alluvium, although they locally include the deposits
of rivers draining the interfluve surface such as the Baghmati (Sinha
et al., 2005a). Apart from developing a strongly ‘hierarchical’ sense,
this approach allows examination of drainage and geomorphic
heterogeneity from very large to small scales. This is a significant
departure from previous work in which spatial homogeneity in
geomorphic development was implied, based on the inference that
correlatable geomorphic surfaces were present across vast regions
of the Ganga plains (Singh et al., 1990; Singh, 1996).
Studies on facies distribution of near-surface fluvial deposits in
the Ganga plains have concentrated mainly in the major channel
areas (Singh, 1972; Singh and Kumar, 1974; Singh and Bhardwaj,
1991; Shukla et al., 1999), as well as on channel dynamics of the
nearby Brahmaputra river (Bristow, 1987; McLelland et al., 1999).
Fewer studies have focused on megafan systems. Research on the
Kosi megafan in north Bihar plains (Singh et al., 1993) reveals
a dominance of sandy facies in the plains with a very narrow zone
of gravel restricted to the reaches close to the mountain front
(10e20 km downstream of the mountain front). Limited studies on
sub-surface stratigraphy of the megafan deposits (Singh et al., 1993)
suggest that they consist of multi-storied sand-sheets (generally
gravel in upper reaches), interbedded with overbank muddy layers.
In contrast to the channel deposits, which have received wide
attention, the information available on the stratigraphy of the
extensive interfluve areas, which form the overwhelming majority
of the Ganga plains surface, has until recently been very limited.
Shallow alluvial architectural studies in the GandakeKosi interfluve
(Sinha, 1995; Sinha et al., 1996; Jain and Sinha, 2003; Sinha et al.,
2005a) showed that the top 2e3 m of the interfluve predominantly consist of muddy sequences, with narrow sand bodies
defining former channel positions and very minor sandy layers
defining crevasse splays. In the ShardaeGandak interfluve area, the
top 10e20 m of sediments are characterized by muddy sequences
alternating with thick medium-grained sand layers. The coarse
sand layer was interpreted as a possible marker for a Rapti palaeochannel with high-energy fluvial regime.
The GangaeYamuna interfluve in Uttar Pradesh has attracted
much recent attention, and initial work on this area focused on
geomorphic mapping using aerial photos coupled with sub-surface
analysis based on water well data (Bajpai, 1989; Singh and Bajpai,
1989). Singh et al. (1999) provided a brief description of the
important Kalpi cliff section along the Yamuna river with evidence
(worked bone artifacts) of human occupation of the region since
w30 ka. A provisional stratigraphic framework for the section and
a small amount of chronological data was presented, and an
interplay of climate and tectonics was implied in the deposition of
this 33 m thick section (Singh et al., 1999). Later research (Sinha
et al., 2002, 2005b; Gibling et al., 2005; Tandon et al., 2006) has
led to significantly different interpretations. Using an integrated
approach involving geomorphic analysis aided by remote sensing,
and followed by rigorous stratigraphic and sedimentologic analysis
of the exposures in cliff sections, these workers have recognized
prominent stratigraphic discontinuities. These discontinuities form
the basis for a stratigraphic framework that can be dated and
compared against proxy records for controlling factors (tectonics,
climate, and relative sea-level). This work was followed up by
raising a series of drill cores from the Ganga valley and the adjacent
interfluve to the south, which has further extended and improved
our understanding of the region (Sinha et al., 2007).
Some workers advocated the importance of preferentially
aligned, tectonically-controlled lineaments on the channel pattern
of the Ganga river, and also suggested that lineaments have caused
preferential cliff incision along the southern bank near Kanpur
(Singh and Rastogi, 1973; Singh et al., 1997, 1999; Srivastava et al.,
2003). No support was provided for this argument from sub-
R. Sinha et al. / Quaternary International 227 (2010) 81e86
83
Fig. 1. The Ganga plains in the Himalayan foreland basin. The plains are fed by the rivers originating in the Himalaya to its north as well as the Craton to its south. The Ganga river
forms the axial drainage with a total length of 2510 km and catchment area 980,000 km2.
surface data. Shallow sections below geomorphic surfaces near
Kanpur were dated by Srivastava et al. (2003) and yielded early
Holocene ages, although these surfaces are separated vertically by
w10 m. In view of these dates, the suggestion of major tectonic
activity at w6 ka to trigger valley incision (Srivastava et al., 2003)
does not seem plausible. On the contrary, a climatic control is
strongly supported by the regional distribution of incision events at
sites across the Ganga plains and in western India, as well as by
a general correlation with the available climatic proxy records for
the region (Sinha et al., 2002; Gibling et al., 2005; Tandon et al.,
2006). The early to mid-Holocene was marked by high precipitation, and our own further work in this region using shallow drill
cores suggests significant valley aggradation during these times
(Sinha et al., 2007), as well as southward migration of the Ganga
river. It has been argued that major phases of valley incision took
place during transitions between humid and less humid conditions
(for example, following the Last Glacial Maximum and during the
mid-Holocene). Conditions during such transitions are especially
able to trigger incision due to changes in runoff intensity, as suggested by recent modelling (Rinaldo et al., 1995; Tucker and
Slingerland, 1997).
3. Unresolved issues and recent developments
The controls of alluvial architecture below the Ganga plains
continue to be investigated, and the need for a comprehensive data
set on the sub-surface stratigraphy of the Ganga plains is enormous.
Furthermore, the Ganga river system has experienced large fluctuations in discharge and sediment yield induced by variations over
the last 150,000 years in the strength of the monsoon (Goodbred,
2003; Gibling et al., 2005), which is known from modelling and
field-based studies to have varied greatly over the past 100,000
years and beyond (Prell and Kutzbach, 1987; Overpeck et al., 1996;
Clemens and Prell, 2003). Some of the important questions which
remained unanswered over several decades of research in the
Ganga basin include: (a) how long have the axial Ganga and Yamuna
rivers been near their present positions, and have they ever inundated the interfluve between them? (b) how have the Himalayan
and cratonic rivers competed in the geological past to generate the
Ganga plains stratigraphy? (c) is the modern geomorphic setting of
considerable antiquity, or have the major rivers been more mobile in
the past and able to migrate more freely? (d) what has been the rate
of river migration and what has been the role of thrusting and
deformation along the Himalayan Front to the north in promoting
river avulsion? (e) how are variations in monsoonal intensity
reflected in the sediment record of valleys and interfluves? (f) can
distinctive stratigraphic patterns be used to test models of landscape evolution across the vast expanse of the Ganga plains?
Most of these questions required an in-depth analysis of subsurface stratigraphy which was not previously possible due to
limited exposures across the plains. Apart from the incised river
sections in the western Ganga plains, there are few natural exposures that allow researchers to examine and understand spatial and
temporal variability in stratigraphy of the plains and link them to
forcing functions. Systematic drilling and coring in this region has
been non-existent until recently. A major research programme was
therefore launched by us in 2000 and a decade of research has
involved cliff section stratigraphy, drill-core stratigraphy, resistivity-based sub-surface mapping, geochemistry, sedimentology
and magnetic mineralogy. These studies have added to our
understanding of the Ganga basin’s stratigraphic development, its
response to monsoonal forcings, and competition between Himalayan and cratonic supply of sediments, among many important
issues. We summarise below some of the important contributions
and suggest some possible future lines of enquiry.
The stratigraphic record for the upper 50 m of the alluvial cover
in the western Ganga plains has been studied through river-bank
sections (Gibling et al., 2005, 2008; Sinha et al., 2005b; Tandon
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R. Sinha et al. / Quaternary International 227 (2010) 81e86
et al., 2006) and drill cores (Sinha et al., 2007, 2009). These strata
cover a period of w100 ka, revealing a complex history of dynamics
of large and small river systems, and a strong climatic control. A
marked geomorphic diversity from north to south, as well as east to
west across the Ganga plains (Sinha et al., 2005c), adds further
complexity in terms of the response of the river systems to external
forcing.
An important finding is the recognition of major discontinuities
in the late Quaternary interfluve sequences (Gibling et al., 2005)
separating aggradational sequences. Such discontinuities are
manifested as pedogenic events, gully fills, non-fluvial deposition,
and carbonate cementation/calcrete development. The valley fills
of the Ganga record two major aggradational phases (pre-LGM and
middle Holocene) in drill cores penetrating down to about 25 m
(Sinha et al., 2007). A major river (paleo-Ganga) was located near its
present position since at least 26 ka BP, with indications of southward migration between 11e6 ka. Our chronological work on the
cliff sections and cores from the Ganga plains suggest that some
‘aggradationedegradation rhythms’ follow monsoonal fluctuations
during the Late Quaternary (Prell and Kutzbach, 1987, 1992;
Clemens and Prell, 2003). Repeated cycles of valley aggradation
occurred particularly during transitions between humid and dry
climates, in accord with the available chronological and climatic
proxy data and modelling results for the region. Where geochronological results are available, valleys in the western Ganga plains
manifest late glacial/early Holocene incision in response to
monsoonal intensification, and this regional phase of incision was
primarily responsible for generating the modern landscape in this
region. Floodplain degradation and intra-valley floodplain accumulations mark the weak summer monsoon periods. High-resolution studies of lake sediments from the Ganga plains (Sharma
et al., 2004) have provided an important proxy record for climate,
with which fluvial events may be compared.
A more recent work by Rahaman et al. (2009) has demonstrated
that the relative proportion of sediment supply from the Higher
and Lesser Himalaya has varied through time in consequence of
monsoonal fluctuations. In the 87Sr/86Sr and 3Nd profile from
a Ganga plains core, two major excursions at w20 ka and w70 ka
were identified, coinciding with periods of precipitation minima
and larger glacial cover. It was suggested that these excursions
resulted from a decrease in the proportion of sediment transported
from the Higher Himalaya due to decrease in monsoon precipitation and increase in glacial cover, which in turn are caused by lower
solar insolation.
Another important question tackled recently is the competition
between the Himalayan and cratonic sources of sediment to
generate a distinctive stratigraphic architecture below the plains
(Sinha et al., 2009). Contrary to the general belief that the Himalayas have been the dominant contributor of sediments in the
Ganga plains through most of the Quaternary (Burbank, 1992),
Sinha et al. (2009) argued that the contribution from cratonic
sources has been significant during the Late Quaternary. The subsurface alluvial stratigraphy in the Gangetic plains reflects such
competition between the Himalayan and cratonic sources. Based on
framework grains and dense minerals of drill-core sediments and
modern river sands, a wedge of cratonic sediment extended well
beyond the modern line of the axial drainage in the southwestern
part of the foreland basin, at both shallow and deep levels. It was
concluded that the dynamic cratonic rivers have been underestimated as contributors to the Himalayan foreland basin. The
Yamuna river may have occupied its present position in the Ganga
plains only after w6 ka, prior to which cratonic rivers may have
contributed a considerable amount of sediment to the Ganga River
and Bay of Bengal, although the Himalayan contribution has
probably always predominated.
4. In this issue
The present issue has a set of seven papers including the
introductory paper which provides an overview of the Ganga plains
research. Sinha et al. focus on the stratigraphic sections along
a 50 km stretch of the Ganga valley in the frontal parts of the
Himalaya. The authors recognize four levels of fluvial terraces, both
strath and fills, and alluvial fans, and argue that these terraces
developed as a result of tectoniceclimate coupling during the Late
Pleistocene and Holocene. Based on OSL chronology, these terrace
surfaces formed through river incision at w11 ka, 9.7 and 6.9 ka,
and were most probably climatically induced. The incision events at
w11 ka and w7 ka are analogous to those recorded across the
Himalaya and in the Ganga plains (Pratt et al., 2002; Goodbred,
2003; Pratt-Situala et al., 2004; Tandon et al., 2006). The fact
that, even in the tectonically active Himalayan mountain front,
terrace formation is driven by climate is a significant input for the
general understanding of landform development in this region,
although tectonics has influenced terrace elevation and gradient
(Lavé and Avouac, 2000; Singh and Tandon, 2007).
Yadav et al. demonstrate the application of Vertical Electric
Sounding (VES) for inferring shallow sub-surface stratigraphy in
parts of the Ganga plain. This study fills a significant gap in terms of
reliable stratigraphic sections in an area where cliff sections are
limited and drill-core data is scarce. Resistivity sounding data for
a stretch of w150 km in the interfluve areas between the Ganga and
Yamuna rivers and Yamuna and Betwa rivers in the western Ganga
plains clearly exhibit the vertical extension of the valley fills and
interfluve sequences down to w100 m. Apart from locating distinct
boundaries between sandy and muddy strata, very high and very
low resistivity layers were interpreted as calcrete layers and saline
aquifers, respectively. The study not only provides support for the
interfluve stratigraphy models proposed in earlier studies (Gibling
et al., 2005; Sinha et al., 2007, 2009) but extends the stratigraphic
data to w100 m (w200 ka). The authors suggest that the
GangaeYamuna interfluve is a stable and long-lived feature of the
Ganga plains and that the antiquity of the present valleyeinterfluve
configuration extends to more than 200 ka. Significant sub-surface
heterogeneity is noted across the valleyeinterfluve setting as well
as within the interfluves themselves.
Sahu et al. have investigated the parts of the Middle Ganga valley
in Bihar plains and report a classical example of tilt-induced avulsion
and channel migration during the Holocene. The study focuses on
one of the important southern tributaries of the Ganga, the Son
River, and parts of the GangaeSon confluence. Although tilting of
alluvial surfaces has been documented in the tectonically active
region of north Bihar (Jain and Sinha, 2005), this is the first detailed
documentation of active tectonics and its influence on landscape
evolution from a region south of the Ganga river. Although several
active sub-surface faults reported from the northern part (Dasgupta,
1993; Jain and Sinha, 2005) have been thought to extend south of the
Ganga, their influence on river morphology and processes has
remained unknown. The authors have identified 9 avulsion events in
the Son river and have attributed these to high lateral tilt related to
its proximity to one of the important faults, the East Patna Fault
(EPF). The Ganga river is located in the lowered part of the tilted
block away from the line of uplift, and has migrated in the down-tilt
direction. Various fluvial anomalies such as gradient reversals in the
longitudinal profile of channels, sinuosity variations, channel incision, frequency of braid-bar distribution, and variation in the crosssectional parameters of the channels were identified on satellite
images and using topographic data to reconstruct the tectonic
history. The authors conclude that the rate of lateral tilt has
controlled the style of channel movement, with gradual migration
occurring at low tilt rates, and avulsion at higher rates.
R. Sinha et al. / Quaternary International 227 (2010) 81e86
Srivastava et al. have presented a detailed documentation of soil
micromorphology of core sediments from the GangaeYamuna
interfluve in the Himalayan foreland basin. Two cores, w50 m deep,
were used for this study, one each from the northern (IITK core) and
southern (Bhognipur core) parts of the interfluve. Despite the cores
being separated by only w60 km, they show significant variability
in terms of distribution and nature of paleosols, and are characterized by a set of micromorphological features that include
microstructures, rhizocretions, FeeMn features, pedogenic
carbonate, illuvial clay coatings and relict pedofeatures. These
paleosols range in character from simple ones having weakly
developed pedofeatures to mature paleosols with strongly developed pedofeatures, and are similar to modern Entisols, Inceptisols,
Alfisols and Vertisols of the Ganga Plains. The authors note
a significant difference in the pedosedimentary evolution in the
two cores representing northern and southern interfluves in terms
of stratigraphic stacking of paleosols, types of paleosols, and
heterogeneous nature of sediments. In the northern part (IITK
core), a thick mature paleosol with a strongly developed argillic (Bt)
horizon at 41e45 m depth is striking, while the remaining core has
only weakly developed paleosols. In the southern part (Bhognipur
core), a mature palaeosol with well-developed argillic (Bt) and
vertic (Bss) horizons is noted at a shallower depth (10e14 m). The
mature paleosol is interpreted to represent a major discontinuity
during MIS 5e4 transition when prolonged pedogenic activity took
place following regional degradation and local gullying in response
to climate change from sub-humid to semi-arid conditions. The
authors conclude that the pedosedimentary evolution of the
interfluve was controlled by climatic transitions from humid to
drier phases and also by supply and availability of sediments.
The Kosi river in the eastern Ganga plains is one of the most
avulsive river systems in the world and has often generated interest
among geomorphologists and stratigraphers alike, the former in
terms of understanding the avulsion process (Wells and Dorr, 1987;
Sinha et al., 2009) and the latter in terms of a distinctive alluvial
architecture below the Kosi megafan (Singh et al., 1993). Chakraborty et al. have revisited the Kosi river and have examined the
historical records to question the hypothesis of unidirectional
westward migration of the Kosi River over the last two centuries.
On the contrary, the Kosi channels have occupied a narrow zone in
the east-central part of the megafan. The channel position did,
however, oscillate randomly within this zone. Further, the authors
argue that, based on examination of the upper 2e3 m of succession
in the north-central part of the megafan, there is an overwhelming
dominance of meandering stream deposits across the fan surface
and not deposits characteristic of a sweeping braided river. Three
accretionary lobes identified on the fan surface and their relative
chronology, determined from channel discordances between lobes,
suggest avulsive behaviour of the trunk channel which is in line
with other fans across the world such as the Tista in the eastern
Ganga-Brahmaputra plains and Taquari in Pantnal wetland, Brazil.
The most recent avulsion of the Kosi river by w120 km to the east in
August 2008 (Sinha et al., 2009) is also in line with the avulsive
behaviour of the Kosi. The authors reiterate the inefficacy of engineering solutions for large rivers through high embankments and
large dams, and argue that these measures have enhanced the
avulsive tendency of the river. Co-existence with floods and avulsions and an integrated catchment management may be better
strategies than a ‘command and control’ approach.
The last paper by K. Rudra deals with the science-policy interaction of river dynamics with special reference to the Ganga in
West Bengal. This stretch of the Ganga river is perhaps the least
studied stretch and there is very little understanding of
the processes controlling river dynamics. Almost no data exists on
the sub-surface stratigraphy of the alluvial plains in this region. The
85
author has compiled the data on historical movements of the Ganga
river in West Bengal since the second half of the 18th century from
rather inaccessible sources of maps. Reconstruction from sequential maps suggests that the Farakka barrage, since its construction
in 1971, has influenced the morphology and position of the Ganga
River in a major way. The Ganga has migrated eastward appreciably
since 1971 and has formed a mighty bend upstream of the barrage.
The impact of the barrage on the river flow and morphology
extended to more than 150 km upstream of the barrage. The author
argues that river aggradation upstream of the barrage has been the
primary factor influencing the change. Downstream of the Farakka
barrage, the river has been unstable and bank erosion has been
a serious problem. Several villages have shifted to the opposite
banks due to rapid channel migration. Apart from causing damage
to the local people, such rapid migration has serious political
implications at interstate as well as international level. Adjoining
the Ganga river, the state of West Bengal shares its boundaries with
Bihar and Jharkhand states and Bangladesh; the river migration at
a decadal scale has posed problems such as land reallocation,
population displacement, and border disputes. These issues need
serious policy interventions, and the existing laws and constitutional amendments are not adequate to handle these problems,
neither at interstate nor at international level. The author has
emphasized that, “...the river management in India was guided by
a colonial legacy and a ‘business-as-usual’ engineering approach
without any concern for holistic eco-hydrology. A paradigm shift is
needed from a narrow sectoral outlook of ongoing river management
strategy to the ecological engineering approach.”
5. Future perspectives
Having evolved strategies for geomorphic mapping of some
parts of the Ganga plains, these need to be applied uniformly
through the entire length of the dispersal system from the Himalayan Orogen to the ocean sink(s). This is imperative for understanding the landscape connectivity in conjunction with
hydrological and sediment connectivity. The assessment and
analysis of the connectivity structure(s) in a multi-scale context
will serve as a pre-requisite for exploring ideas related to the time
scales of propagation of signals at different scales, both in spatial
and temporal contexts, across the length of the dispersal system.
Yet another gap in the holistic understanding of the Ganga
source-to-sink dispersal system is insufficient surface and subsurface data in the downstream reaches of the Ganga (south and
east of the Kosi river). Such data would eventually enable a better
understanding of the stratigraphic development of the Ganga
plains as governed by the interaction of fluvial and marine
processes.
The geomorphic diversity and heterogeneity in landscape
compartments of the Ganga plains needs to be explored further.
Such data need to be collected particularly in the landscape
compartments occurring to the south of the axial rivers, in addition
to intensifying efforts in all the other compartments as well. Finally,
good practices in river management depend strongly on an integration of rigorous geomorphological, hydrological and ecological
data collected at different scales. Such experimental studies need to
be undertaken in strategically chosen reaches. Results from these
studies could then be of general applicability not only for
management of the Ganga river but also for the optimal management of the natural resources of the river basin.
Acknowledgements
Several studies reported in this special issue were supported
through a large programme on the Science of Shallow Subsurface
86
R. Sinha et al. / Quaternary International 227 (2010) 81e86
(SSS) funded by the Department of Science and Technology (DST),
Government of India. We sincerely thank DST for their generous
support for this programme. We would also like to thank all authors
who contributed to this special issue and have waited patiently for
the issue to be finalized. This research is a contribution to IGCP 582
on Tropical Rivers.
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