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Begusarai : Geography and Geology |
A Note on the Geography and Geology of Begusarai
By Ashutosh Shandilya,
Geologist, ONGC
( E
mail-ashandilya2001@yahoo.com)
Background
The district Begusarai, an important district in the state of Bihar lies on the
northern bank of river Ganga. Earlier it was a part of the greater Munger
district. Begusarai district was carved out of it as a separate district on. 2nd
October 1972 (A handnote on Begusarai district census-1991). Now it is a part of
the Munger commissionery. Geographically, lying between latitudes 25015’N
& 25014’N
and longitudes 85045’E & 85045’E, it covers an area of 1918km 2.
In the north, it shares its boundaries with Samastipur district; in the east and
NE it is surrounded by Khagaria district. In the southeastern part lies the
Munger district. In the south is Lakhisarai and in the southwestern side, along
the banks of River Ganga, it is shares its boundaries with Patna district. It is
situated in a part of Middle Gangetic plains, locally known as North Bihar
plains. Administratively it is divided into five subdivisions- Begusarai,
Teghara, Balia Manjhaul and Bakhri and eighteen blocks namely
Begusarai, Mattihani, Teghra, Samho, Bachhwara, Barauni, Bhagwanpur, Balia,
Sahibpur Kamal,
CheriaBariarpur, Khudabandpur, Bakhari. Mansurchak, Birpur, Dandari, Nawkothi,
Garhpura, and Chhaurahi The average population density is app. 900 persons per
square kms. The economy is mainly agriculture based and the major crops are
wheat, maize, chilli, sugarcane etc.
 : The
views presented in this article belongs to the author and in no case represent
the views of the organization to which he belongs or the website which hosts the
article.
Two big
industries mark the skyline of the district i.e. Thermal power station and Petro-Chemicals
factory and Oil refinery complex at Barauni. Earlier Barauni Fertilizer was also
an important industry which is now non functional. Rajendra Bridge across Ganges
at Barauni forms an important link way connecting north and south Bihar, Resting
spot for migratory birds in a wetland known as Kanwar tal and the Ghats of Ganga
at Simaria possessing religious importance, exists as a potential tourist spots.
Climate
Being a part of Gangetic plain of Indian subcontinent, the district experiences
three climatic seasons – summer from late March to mid time rainy season from
mid June to October and the winter season from November to February. The month
of February & March fall in the transitional season from winter to summer
described as spring or “Basant”. Similarly the months of September & October
falls in the transitional season from rainy season to winter season described as
“Shishir”.
Temperature Data (1993)
Source: Meteorological Dept., Patna
During summer due to high temperature this becomes an area of low pressure.
During this period Bay of Bengal, due to its geographical characteristics,
serves as homeland for cyclones. Being on area of low presser, the plains of
Begusarai and associated areas attract these cyclonic winds. This leads to the
dust storms. These dry, hot, dusty storms are locally termed as ‘Loo’. These are
prevalent in the month of May-June.
The rainfall is
average in this area. The average annual rainfall in this belt of Ganga- Burhi
Gandak is 1384mm of which 83% falls between Mid June and & Mid-October. Monsoon
normally starts in June and lasts till October. The early monsoon currents,
channeled to he NW are the principal source of rainfall of the region. 17 % of
pre monsoonal rains, which is spread in the different months of the year
(specially in the months of November- December-January) have been
explained as due to Norwester affect and rest during monsoons due to Himalayan
affect. Heavy rains, supplemented by physiographic/geomorphic features lead to
heavy flood.
The chilling winter
starts in mid-october and continues till initial periods of March. Most part of
the winter is dry except some sporadic rains as mentioned above.
Physiography and
Relief
North Ganga plain is a major
physiographic unit of the Indian landmass. It extends from the Himalayan terrain
in the north to the river Ganga in the south covering about 56980 km2.
a roughly quadrilateral shape. Generally recognized as "a water-surplus area",
this quadrilateral region is bounded by a northern piedmont belt where water
oozes to the surface, followed by a broad belt of swampy lands, depressions and
lakes, and finally an aggregation of alluvial fans as all these northern streams
bend to form confluence points with the Ganga (Singh & Kumar, 1970).Hence, the
surface is characterized by palaeo levees, swamps or flood basins locally called
"Chaurs", relict palaeo channels aggraded in varying degrees, meander belts,
ox-bow lakes and cut-of loops (Ahmad,1971). Its fluvial geomorphology is
dominated from west to east by the Ghagra-Gandak Interfluves, the Gandak-Kosi
Interfluves and the western Kosi Fan Belt. Some of
these rivers frequently change their channels. Their channels are called by
different names in different parts of their courses. According to a study
in 1976 on Wetlands in Bihar, by Govt. of Bihar, natural wetlands of more than
100 ha each covered about 46828 ha (Directory of Wetlands, Govt. of Bihar)
The district of Begusarai
lies in the middle part of this great plain known as mid Ganga plain. In
general, it is a low-lying flat terrain (MSL45m-32m) having a southerly to
southeasterly slope. This factor governs the flow of streams. Geomorphologically
it is a part of the Gandak- Kosi inerfluve (please refer subheading
Geomorphology given below). The southern part of the district, except those of
low-lying flood plains of Ganga, appears to be an elevated landmass when
compared to the adjoining districts of Khagaria and Samastipur. Hence, being a
safer destination amidst the flood drained region, it supports the human
activities in a better way.
The district Begusarai is divided into three flood plains namely
i. Kereha-Old Bhagmati flood plains,
ii. Burhi Gandhak Flood plain and
iii. Ganga Flood plain
The first two flood plains of the district are very low lying areaS and are
prone to the flood. The floods owe their origin to the complex interplay of
fluvial geomorphic elements in the upstream sections of the Kosi,
Bagmati-Kareh-Budhi Gandak and related rivers. These two flood plains
converge in the southeastern
part of the district, which is lowland. The streams flowing in the region show a
shifting tendency. In the course of their shifting, the rivers leave behind
their scars of their previous channels. Thus due to shifting nature of streams
and physiographic characteristic, this part is full of wetlands, backswamps and
oxbow lakes. However, in the southern part, the flood plains of Ganga are least
prone to flodd. Interestingly the Railway track passing through the district
marks a prominent divider line for Ganga flood plain and Kereha- old Bhagmati
flood plains & Burhi Gandhak flood plain. The Flood plains of Burhi Gandak and
Kareha are marked by the presence of paleo levees, oxbow lakes, paleochannels,
relict streams and chaurs viz Kaulachaur and Bhagwanpur chaur. These chaurs
serve as excellent fertile agricultural lands duing summer and are submerged
during rains. Also the areas around these chaurs face the problem of submergence
for around three-four months a year. Kawar lake, a large fresh water lake
which is basically a huge wetland is present as an important physiographic
feature of this part.
In the Gangaflood plain,
which is approaximately 50-55km long and 5-6kms wide,in the southern part of the
district, except those low lying areas of “Taals and chaurs”, the typical
fluvial characteristics of North Bihar rivers are not visible, which are
prominent in the north of Railway track. This is the least flood prone area of
the district, which gets drowned only in cases of exceptional floods in Ganga
and Burhi Gandak. This relatively upland area appears to be the levee of river
Ganga.
Geomorphic Setup
The mid-Ganga plains may be
broadly divided into a number of major geomorphic units(Fig-).The northernmost
part is the region of the Siwalik ranges and is followed by the piedmont fan
surface fringing the foothills, 10-30km wide, built up by coalescing fan
surfaces of major Himalayan rivers. This surface includes both the bhabar and
tarai land. Built upon these surfaces are fluvial regimes classified into
megafans (f) and interfluves, characterised by upland terraces (T2), river
valley terraces (T1) and active flood plain surfaces (T0). The entire district
of Begusarai falls in this T0 surface. The southern and northern banks of the
Gangain and around Begusarai are charactersied by tributaries that flow parallel
to the Gangafor long distances over the floodplain itself, before it joins at
deferred junctions. This belt is named as the Gangayazoo belt (Sinha and
Friend,1994).The Gandak-Kosi interfan has been divided into an upper area of
gently converging rivers that flow SE , Perpendicular to the mountain front and
a downstream area (the district of Begusarai and neighbouring area)where the
more sinuous channels of the Burhi Gandak ,Baghmati,Kamla and Balan systems flow
gently to the SE.
Drainage
The district is drained by a no of rivers viz. Ganga, Burhi Gandak, Bagmati and
Balan rivers and in addition, small rivulets, dhars, nalas which are originated
locally and preserve rain water, mark the landscape. Among the rivers, Ganga,
Burhi Gandak, Kosi, Kareha and Bagmati are perennial, whereas Channa River,
Bainti nadi, Kachna nadi, Monrya nadi and Malti nadi are seasonal.
All the types of streams i.e. the mountain fed, foothill fed, plain fed and
mixed fed, drains the district. Ganga is a mountain fed river while Bagmati is a
foothill fed river. Burhi Gandak, Baya, Balan, Baintia, Chanha etc are
originated in the plains and present examples of plain fed rivers. The small
rivulets serve as tributaries to the streams of higher order. These rivulets are
often dry lowlands during summer and flooded during rainy season.
In general, the drainage pattern of the rivers of this region forms a part of
the greater Gangetic Plain, which is characterized as dendritic drainage
pattern. However, locally they exhibit their typical characteristics. The Ganga
River here shows Yazoo pattern of drainage and the area is known a Ganga Yazoo
belt. Yazoo pattern of drainage is defined by the streams, which travel in a
parallel fashion before confluence. Burhi Gandak, Bagmati, Kareha and Balan,
Baintia, shows very high sinuosity and are typically meandering rivers.
River Ganga enters into the
southwest part draining the Chamtha block in the district. This river along with
its flood plains, “Chaurs” and “Tals” determines the boundary of the district in
the southern part.
The Burhi Gandak, the 2nd
most important river, also known as Sirkahana in its upper reaches, enters the
district near Parihara about 10 km upstream of its confluence with the Balan
River. It forms the boundary with Samastipur district in Khodawandpur and
Cheriabariyarpur blocks. This is a river showing very high sinuosity and has
characteristically low slit content than other Himalayan rivers. After
traversing a distance of approximately 100 Km. it drains in Ganga near Khagaria
.The river cause periodic floods in the western part of the district.
River Balan enters the
district in the Bachhwara block. After taking a course of app 30kms km. it
drains into Burhi Gandak River 5 km west of Manjhaul. This is also a highly
sinuous stream
Bagmati – A very Juvenile
stream of North Bihar plains, drains only the northeastern corner of district.
It enters into the district near Bakhri and is well known for its unstable
nature and spill channels. After traversing the low-lying valley areas, it meets
the Kosi near Sankosh outside the territories of the district. It is responsible
for floods in the northern part of the district.
Baintia River is a plain fed stream originated in the adjoining district of
Samastipur and enters in Bhagwanpur block of the district. Upstreams, in the
Samastipur district, it is known as Jamwari Nadi. This drains into Burhi Gandak
after joining the Balan River. It is also a stream having water round the year.
Baya Nadi drains the district Teghra, Bachhwara and Barauni block. It merges
with river Ganga at Roopnagar near Barauni fertilizer factory. This is a
stream which does not show any sinuosity in the Begusarai district and is a
perrennial stream. In the mid of the Burhi Gandak flood plain lies a vast fresh
water lake known as Kawer Tal, which is basically a wetland formed by shifting
of river BurhiGandak. Kawartal gets its water either due to rains or due
to near-by overflowing rivers such as Burhi
Gandak, Bagmati
Kawar Tal
Kawar Tal is one of the examples of excellent wetlands, which are found in the
flood plains, and is the largest freshwater lake in Northern Bihar. It lies
between Burhi Gandak, Old Bhagmati and Kareh rivers. The lake is formed by the
meandering action of Gandak River and is now a residual ox-bow lake, one of the
thousands in Bihar and Uttar Pradesh flood plains. In years of high rainfall,
vast areas of these two states get flooded. This causes coalescing of wetlands
and forms one huge expanse of water. During these times the wetlands of the
Kawartal region may cover hundreds of sq. kms. The floods leave behind deposits
of sand, slit and clay in layers of varying thickness. In years of
average rainfall, Kawartal gets connected with Burhi
Gandak (a tributary of River Ganga) and with nearby Nagri Jheel and Bikrampur
chaurs, unite to form a lake of about 7400 ha. By late summer however, the water
is confined to the deeper depressions and only about 300-400 ha of Kawartal
remains flooded and cut off from the adjacent floodplains (chairs). As the water
level recedes, over 2800 ha of the exposed mudflats are converted into rice
(paddy) fields. In 1951, a drainage channel was excavated to expose additional
areas for agricultural purposes, but the channel silted up in few years, and the
lake reverted to its former condition. In recent years, further siltation of the
overflow channel has resulted in sight fluctuation in water levels throughout
the lake. There is a permanent island (Jaimangalgarh) of about 130ha in the
Southeast corner of the lake. The Kawar and its adjoining lakes are probably
oxbow lakes fed by highly meandering river, the Burhi Gandak that once flowed
through these areas. As this lake area remains wet and submerged for a longer
period, it has developed specially adopted wetland vegetation and organisms. The
emergent, submerged and floating plants present some unique type or
representative flora and fauna particularly of this lake and its adjoining
areas. Hence, it is a spectacular wetland habitat and perhaps one of the largest
freshwater inland wetlands in the country.
DRAINAGE AROUND KAWAR TAL
(From Kumar, Sanjeev,
2004)
Drainage Characteristics of the Gandak Kosi
interfan
The district of Begusarai lies in the southern part of the Gandak Kosi interfan
area.
The region between the Gandak and the Kosi megafans is a vast plain with a
south-easterly slope reflected in the drainage directions. The major interfan
rivers are the foot-hill-fed and the plain-fed Burhi Gandak, Bagmati, Kamla and
Balan. These rivers determine the architecture of the flood plains. However,
numerous interconnected minor channels participate in carving out the features
of the plains by reworking and redistributing the sediments deposited by the
major tributaries of the river. All the channels constitute low-lying areas and
remain waterlogged during the monsoon. Channel avulsion and overbank flooding
are the two most important factors controlling the floodplain development of the
region (Sinha,1996).
Avulsion is the sudden diversion of a part or whole of a river channel to a new
course at a lower level on the flood plain. There is also a paucity of cut-offs,
consistent with their moderate sinuosities.
The Burhi-Gandak river system has developed along the palaeochannel of the
Gandak (Mahadevan 2002). Its channel has, however, become much smaller and
highly sinuous and provides an example of river "metamorphosis". The river has
however, been changing its course locally through avulsion, leaving extensive
floodplain scars such as sinuous abandoned channels, "neck cut-offs" and ox-bow
lakes, unmatched in their scale and abundance by any other part of the North
Bihar Plains. Such cut-offs have resulted in reduction of channel lengths and
sinuosity. Distinct topographic levels similar to what has been described
earlier in the Kosi channel characterize the Burhi-Gandak floodplains near
Muzaffarpur. The development of the different levels is attributed to local
fluctuations in discharge and sediment load resulting in downcutting by the
channel and lateral migration.
The Bagmati avulsive system is characterized by abandoned channels to the east
of the present mid-reaches of the river. These are "underfit" channels and are
activated and recaptured from time to time(Sinha1996) .A westward shift of the
river is ,however, still evident. The Baghmati system encompasses what are
turned "chute cut-offs", that may be a reflection of the "active migration where
loop development and floodplain erodability during brief overbank flows are such
as to allow the creation of new short-circulating channels". The Kamla and Balan
systems show less evidences of avulsion. The westward shift of the Balan river
is linked with the growth of the Kosi megafan. The Kamla river,however,is
outside the influence of the growth of the Kosi megafan.
The
transformation of channels, their metamorphosis, and the development of underfit
channels, according to Sinha (1996), are both not due to climatic changes, as
often assumed, but due to channel avulsion and channel-floodplain relationships.
The development of "cut-offs" in the
river systems is not so sudden an event and has taken place over a period of
time, which, therefore, opens up scope to investigate the phenomenon more
thoroughly. Some of the cutoffs have also evolved into ox-bow lakes. Other
features of interest in understanding the evolution of the floodplains include
features developing from lateral accretion, such as point bars and bedding
structures and featured resulting from vertical accretion as natural levees,
crevasse splays, backswamps, wetlands and lakes.
Controls in
Shifting Courses
The rivers of this area
exhibit a migrating tendency. The migration of rivers has to be viewed in the
context of the fluvial evolution of the Indo-Gangetic plains. Brubank et
al.(1996 in Mahadevan, 2002) address this question. A plausible model that helps
to view the course changes is that the Himalayan provenance for the foreland
rivers changed from a period tectonically dominated by thrust–loading and uplift
in the Miocene to an erosionally dominated climatic-unloading, causing isostatic
uplift. This concept is supported by the onset of suggested monsoonic climate
due to Himalayan uplift around 8 Million years back.
As mentioned in the Geology
subtitle, this MidGangaplain is a forelend basin which is subsiding with
continous sedimentation in front of rising Himalayas. The cross-sectional
geometry of the foreland and the patterns of fluvial deposition, inferred from
the limited data now available, also support a dichronous evolution. In the
Miocene period, when thrust loading dominated, the Indo-Gangetic foreland had an
axial river system across its medial and distal parts flowing over its own
accumulated sediments. With the onset of climate, induced erosional unloading of
the Himalaya, transverse river systems started, dominating. The medial foreland
pushing the medial axial river southwards to almost the featheredge of the
foreland basin, even as the proximal part of the foreland was witnessing uplift.
In the context of the fluvial
setting outlined above, channel shifting has been attributed to regional
tilting, depletion of flow by fanhead tilting, derangement of drainage by
earthquakes, the coriolis effect and auto cyclic mechanisms (Wells and Dorr.Jr.
1987 and references there in, from Mahadevan 2001).
Recent
publications have emphasized the role of neotectonic changes in shifting river
courses. Mohindra et al. (1992) and Mohindra (1995) attribute the shifting of
the river Gandak to neotectonic tilting of the megafan eastward. However, the
recent shifting of the Gandak River to its present channel from the Burhi Gandak
channel westwards, suggests that there are also other factors (?autocyclic)
which play an important role. A detailed analysis of the causes of shifting of
the Kosi river by Wells and Dorr Jr. (1987 in Mahadevan 2002) leads to the
conclusion that the
major shifts are "stochastic
and autocyclic " and they do not well correlate with many severs earthquakes and
floods, though they may have primed the system for shifts.
Diverse avulsion mechanisms
have been inferred from the channel systems in the Gandak- Kosi interfluve. The
Burhi Gandak shifts its channel eastwards due to paleotopography and
sedimentological readjustment. The Baghmati shifts westward through the same
mechanisms. The avulsion of the Balan river channels, however, is attributed to
neotectonic response and the westward shift of the Kamla to the expanding growth
of the Kosi megafan, on whose fringes the channels of Balan flow. The widely
differing explanations of the shifting behaviors of North Bihar Rivers underline
the complexity of the problem and the need for further research.
GeologyaandbSoil
The geology of the area constitutes the highest alluvial plain in the domain of
the Himalayan Rivers to the north of the Ganga. It is a part of the Great
Gangetic Basin. The basin was formed during late Paleogene-Neogene times and is
related to the upheaval of the Himalayas vis a vis flexural downwarp of the
Indian Lithosphere under the supracrustal load of the Himalayas (Wadia, 1961).
The entire segment abounds in buried faults and grabens. The basin came into
existence as a result of the collision of India and China continental Plates (Dewcy
and Bird, 1970 in Parkash) during the Paleocene. Collision resulted in
intraplate subduction along the MCT(Main Central Thrust lying in the Himalayas)
raising the Higher Himalaya to form source rocks and “popping through” of the
more southerly part of the Indian plate to form the basin. This “popping
through” might have lead to the development of longitudinal and transverse
lineaments thougout the basin. With time more southerly areas were raised and by
mid-Paleocene subduction also started along the MBF(Main Boundary Fault lying in
the Himalayas). These phenomena are reflected in the presence of a coarsening up
megacycle with at least two superimposed minor cycle and in the composition of
the sandstone and conglomerates of the basin. Later folding of the northern edge
of basin to form the Siwalik Ranges during the Early Pleistocene led to
cannibalism of this part of the basin.
The basin had east west elongated shape and started with a shallow marine
environment, which changed to estuarine and deltaic one with time. By
mid-Miocene, continental sedimentation marked by fluvial environment dominated
the scene and this set up has continued to the recent with minor modifications.
The basin had predominantly transversal pattern controlled by southerly flowing
rivers emerging from the Himalaya and during Neogene period, a master stream
along the southern margin of the basin drained into the Bay of Bengal. The
fluvial sedimentation took place the form of mega-alluvial cones. Sedimentation
in the basin was influenced by tectonism through out its evolution.
The Indogangitic Basin, still an active one, needs to be studied for detailed
stratigraphic correlation, sedimentary facies relationship, change in climate
through space and time and modern sedimentation.
A
Quaternary fault system has been identified in the region. This is an echelon
pattern of surface faults associated with Begusarai fault (Fig). Within this
fault zone, various geomorphic features are found which have their origin in
both the lateral and vertical movement of fault-bounded slices, as well as in
the persistent strike-slip. In regions where tectonic activity is less
pronounced, streams generally flow more or less perpendicular to the adjacent
highlands
The Quaternernay sediments of the Indogangetic plains have been traditionally
subdivided into the older and younger alluvium and locally called Bhanger and
Khader. Entire area of Begusarai falls in the domain of “Khader” sediments
The soil of this land unit is primarily unaltered alluvium, which is yet to
undergo pedogenesis (process of soil formation). Texturally it varies from sandy
loam to loam in the meander scroll and levee(the upland bounding the flood
plains of the river) areas, to silty loam and silt in flood basin areas of the
Himalayan rivers and from loam in the levees of Ganga to clayey loam and clay in
the basin of Burhi Gandak and Bhagmati river. The soil of the area is sandy loam
rich with humus and is also very fertile.
Referances:-
1.
The subsurface Geology of the Indo-Gangetic plains M.B.R
Rao,1973,no:-3,vol-14,journal of Geological Society of India,pp-217-242.
2.
Geological Evolution of Gangaplains an overview, Indra Bir singh,Journal
of Paleontological Society of India vol-41,1996,pp-99-137
3.
The Indogangetic Basin- B.parkash and Sudhir Kumar,Sedimentary burins of
India,Tectonic contest.
4.
Study of spatio-temporal changes in the weltands of North Bihar through
Remote Sensing,A.K.Ghosh,N.Bose.K.R.P.Singh and R.K.Sinha July
204,ISCO-204,International soil conservation organisation conterence Brisbane
5.
kanwar lake wetlands, strategies for conservation Sanjeev Kumarhttp//sndp.nic.delhi..in,
downloaded in March 2004
6.
Tectonic Zonation using Multi-Criteria Decision-Making (MCDM) Techniques:
A case study of Kosi Fan, India Ajay Srivastava ,
www.gisdevelopment.net/application/geology, downloaded in March 2004
MAP SHOWING LINEAMENTS AND MAJOR FAULTS AROUND BEGUSARAI
(from
Srivastava, A, 2004 )
Regional geomorphic elements of the
Mid-Ganga Plains of Bihar. T1
– River valley terrace surface; T0 – active floodplain surface. MP – Marginal
plain upland surface; PF Piedmont fan surface (Geomorphic elements after I.B.
Singh, 1996).(from
Geology Of Bihar And Jharkhand,T.M.Mahadevan,2002 )
Geodynamic
setting of in the three geomorphic domains of Bihar.Projected profile along 850
E longitude.
(from
Geology Of Bihar And Jharkhand ,T.M.Mahadevan,2002)
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