Journal of Global Resources
Volume 6 (01)August 2019-January 2020
Page 203-206
UGC–CARE Listed Journal in Group DISSN: 2395-3160 (Print), 2455-2445 (Online)

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MORPHODYNAMICS OF RIVER BHAGIRATHI AT PURBASTHALI BLOCK, BURDWAN
DISTRICT, WEST BENGAL: A CONTEMPORARY PERSPECTIVE
Indrani Mukherjee
Department of Geography, Chandrapur College, Chandrapur, Burdwan, India
Email: indranimukherjee662@gmail.com
Abstract: The Bhagirathi is the principal perennial stream of the Purbasthali Block. It enters
into the study area in the northwestern part, just few kilometers south of Katwa town. Analyzing
the images (1973,1990,2004, 2018 and Google Earth Image) and topographical sheets(1927and 1968-69) it has been found that the river takes a highly meandering course throughout thewhole study area and leaves long loops of disused channels which have become ox-bow lakes,bils and swamps over time. The total length of the river Bhagirathi (within the study area) wasreduced and the number of cut-offs has increased. These morphological aspects reveal that theriver Bhagirathi is in very dynamic condition and having a tendency to shortening its course bystraightening the channel. The study tries to focus on the morphological changes in the course,
probability of generation of cut-offs in future.
Key words: Meander, Cut-offs, Sinuosity index, Morph dynamics
Introduction
The nature of deltaic rivers is to shift their course constantly, varying from one bank to another,
popularly known as ‘reach points’ or ‘meander belt’, over centuries and even over decades.
River channel shifting is a part of nature’s design in forming delta lands. The height of the riverplain rises with the sedimentation carried by the river flow. Gradually, the delta becomes
moribund and river flows towards more low-lying areas. The same process is then repeatedand new channels are formed. The left-out part becomes ox-bow Lake, bil, marshes etc. Thesefeatures are nothing but the salient evidence of frequently changing river courses (Bagchi &Mukherjee, 1978).
About Study Area
Geomorphic Unit
Flood plain (partof moribund
Ganga delta)

Topography
Location: on theright bank of theriver Bhagirathi.

Geology
Composedof recent
deposits ofthePleistocene
period.

ClimateTropicalmonsoonclimaticregion (‘Am’type).

Generalelevation:
ranges from 12
to 15 meters.
Source: Field visit and Survey of India Topo sheets 79 A/2 & 79 A/6

Soil
Surface soil:
recent alluvialformation.
Underlying soil:
older alluvium
formed ofdifferent
materials.
Nature: Soil ismoderate tostrongly alkaline

Vegetation
Tropicalmoist
deciduous
Mango,banana,coconut,palm etc.
arecommon.

Objective of the study
The main objectives of the study are following: To find out the morphological changes of the river Bhagirathi in the study area.
 To identify the areas with most oscillating channel pattern of the river Bhagirathi.
Methodology
Morphometric Measures
 SI = meandering length/ straight length Meander cut off: For the study of the cut-offs an angle is taken between the meandercurves. The angle is said to be “ѳ”. The “ѳ” value when reaches 5° or less and the distance203between two tangents are 1km or less the meander reaches the breaking point (Basu,2005).
Channel Change
Topographical sheets of 1927, 1968-69, LISS-III satellite image of 2008 and 2018 are georectified and processed to identify the nature of channel oscillation and major areas of change.
Analysis of Morphological Changes of the River Bhagirathi
The Bhagirathi is the principal perennial stream of the study area. It enters into the study areain the northwestern part, just few kilometers south of Katwa town. The total length of the river
within the study area is about 33.62km. The river takes a highly meandering course throughout
the whole study area and leaves long loops of disused channels which have become ox-bow
lakes, bils and swamps over time. The Bhagirathi, in its upper reaches (the reach upward theNabadwip town) is at present a comparatively insignificant stream, but surrounding country
gives evidence of the vast size which it attained when it formed the main bed of the Ganges(Gazetteers, Nadia, April 1978). Alterations are continually taking place, loops being formed,
cut through and reformed throughout the whole stretch of the Bhagirathi in its seaward course.
So the traces of old channels in the form of semi-circular bils or lakes are frequent along thebanks.
Table 01: Some Aspects of Fluvial Morphology
Morphological PropertiesBhagirathi(within study area)
1927
1968-69
Actual length of river
45.68
36.97
Number of meander loops
67
Number of cut-offs
45

2018
33.62
77Source: Raw Data obtained from Topographical Sheets No. 79 A/2, 79 A/3, 79 A/6, 79 A/7 and 79ASurvey of India, LISS-III image of November2008 and 2018, and compiled by researcher

Table 01 depicts some important morphological aspects of the river Bhagirathi in thestudy area. The total length of the river Bhagirathi (within the study area) was 45.7 km during
1927, which reduced to 37 km in 1968-69 & now it is 33.62 km. However, the number of cutoffs has increased from four in 1927 to seven in 2018. These morphological aspects reveal thatthe river Bhagirathi is in very dynamic condition and having a tendency to shortening its course
by straightening the channel.
Figure 01: Sinuosity Index of the River Bhagirathi within the Study Area

Temporal Change in the Sinuosity Index of River Bhagirathi
3.5
3Sinuosity Index

2.5
2
1.5
1
0.5
0YearsSI1927
3.12SI1968
1.71

Dampal to Mertala

1.3

1.25

1.4

Mertala to Samudragarh

1.52

1.981.74

Agradwip to Dampal

SI2018
2.27

From the fig. 1 the sinuosity index of the river Bhagirathi at some particular stretches
have clearly depict that the river has a winding course, due to flat gradient on which it flows andalso due to the amount of sediment it is carrying. In these parts (fig.2) sinuosity ranges from1.25 to 3.12. In 1927 the river in the Agradwip to Dampal stretch was flowing through a very204

winding or torturous course, the index was 3.12, due to which Agradwip loop (fig.1 and 2) now
became a cut-off namely Chara Ganga. The sinuosity index is still very high (2.27) in this area.
In Mertala to Samudragarh stretch the river is flowing through a meandering course, index
ranging from 1.52 to 1.98. The loop near the Nabadwip became very acute in 1970 to 1980
period, during the 1985 monsoon (year got from the respondents during door-to-door survey)
the river by-passed the loop which now became an ox-bow lake namely Chupi bil (fig. 2). The
channel deposition sometimes enhances the intensity of erosion in certain portions. In the study
area, formation of mid-channel bars (near the village Nawapara, kamalnagar, Charkasthasali)
and several point bars have become the sites of cultivation. In course of time, these will bestabilised making the existing channel narrower and enhances the energy level of the fluvialsystem. The immediate impact is severe erosion few kilometres downstream in the villages like
Mertala and Majida, where the flow vectors would naturally be accelerated.
Figure 02: Oxbow Lake

Formation of Cut-offs or Bils
The cut-offs or the bils are nothing but the former river courses, left-out as a part of dynamic
fluvial condition. These cut-offs are mainly formed due to loose texture of the soil and thevariation in the amount of discharge in the rivers. Continuous extension of the meander bends
when riches at the breaking point, the river by-passed the meander loop with ultimate formationof cut-offs. The formation of cut-offs have led to the sudden increase in gradient because of thestraitening of the channel and the increasing the hazard of river bank erosion (Basu, 1972).
For the study of the cut-offs an angle is taken between the meander curves. The angle
is said to be “ѳ”. The value of “ѳ” is defined to be the angle made between two tangents in theoutward direction and the tangents being drawn from such two points on the curvature of themeanders so that the angle between the tangents just shifts from inward to outwards direction.
The “ѳ” value when reaches 5° or less and the distance between two tangents are 1km or lessthe meander reaches the breaking point. It was observed that at Purbasthali-Mayapur reach theangle made between two tangents were 4º-5° and the distance were 0.75 km which reached at
the breaking point and cut-off had occurred namely Chupi bil (Basu,1972). In 1927 the loop
near Agradwip was reached near the breaking point where the angle remained 5º and distancewas 1.4 km (fig 3). This loop became a cut-off namely Chara Ganga about 1950s. With thisidea, the author tried to find out the possibility of the formation of the cut-offs which will occur innear future in the study area. It is seen from the study of the meander curves near Patuli andDampal that during the year 1968-69 (fig.3) for both of the curves the tangents remained
parallel and divergent respectively. In 2008 (fig.5) the angle of Patuli loop became 11º withdistance 0.70km and Dampal loop with 7º angle and distance 0.65km. From the study of thesemeanders it can be assumed that both of the loops have changed in between the year 1968-69
and 2008 but they not yet reaches up to the breaking point, so they will not form a cut-off in205

very near future. The tangents remained parallel in case of other loops like Per Media andSamudragarh, so there have no chance of cut-off formation in near future (fig.6).
Figure 03

Figure 04

Figure 05

Figure 06

Conclusion
The discussion in the preceding reveals that the river Bhagirathi has an oscillating course since
the past. On the basis of the records available and observations made. The river Bhagirathi isflowing in a highly meandering channel throughout the whole study area. From the fig.2 it isclear that in most of the stretches the river Bhagirathi is following in a meandering course since
Rennells time to 2018. Concave banks of the river are the maximum erosion prone zones
which have been observed during the field study and from the maps of the Bhagirathi
floodplain. Continuous shifting of the river course threatens the railway lines and roads,
settlement, schools, agricultural lands etc. The life of people in the area is highly insecure anduncertain. Bank erosion affects people, irrespective of farm sizes. Riverbank erosion causes
setback for village agriculture. Along with homestead settlements, it erodes farmland,
infrastructure and the communication system. The big farmers are the worst affected, followedby medium farmers, and marginal groups. The affected people lose their assets and are forced
to draw on savings and often fall into further debt. Most of the environment-induced refugees
turn mainly into labourers or rickshaw pullers. A large proportion of the victims remain
unemployed due to lack of work opportunities. Moreover, women head many of these families.
The female-headed households displaced by riverbank erosion and residing on embankments
are the most deprived group. Fortunately, nowadays, social workers are focusing on theseproblems and also suggesting strategies of survival to these people
References
1. Bagchi, K. and Mukherjee, K. N. (1978) Diagnostic Survey of Deltaic West Bengal. Calcutta:
The Project from Geography Department, Calcutta University.
2. Basu, S. R. and Chakravorty, S. C. (1972) Some considerations over the decay of the
Bhagirathi drainage system. In K. G. Bagchi (Ed.), The Bhagirathi-Hooghly Basin (pp. 5977). Calcutta: R. D. Press.
3. Garrett, G. H. E. (1910, 2001) Bengal District Gazetteers, Nadia. Calcutta: Bengal
Secretariat, Book Depot.

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