Volume 66, Issue 1, 2022

Journal of Scientific Research

of
The Banaras Hindu University

Flood Risk and Impact Analysis of Varanasi

City Region, India
Mallikarjun Mishra*1, Vikas Dugesar2, and K.N.Prudhvi Raju3

*1Department of Geography, Institute of Science, Banaras Hindu University

Varanasi-221005, Email: mallikarjungeobhu2016@gmail.com; mallikarjun.mishra5@bhu.ac.in

2Department of Geography, Institute of Science, Banaras Hindu University

Varanasi-221005, Email: dugesarvikas@yahoo.com

3Department of Geography, Institute of Science, Banaras Hindu University

Varanasi-221005, Email: knpraju1954@gmail.com

Abstract: Varanasi city has spread from its original place of origin logging too in the cities of India under even moderate rainfall of high
over the natural levee into the flood basin and on to the low-level intensity in a short duration because of very high runoff from urban
floodplain. More often the city of Varanasi suffers due to storm surfaces (Swan, 2010; Ali et al., 2011; Suriya and Mudgal, 2012; Zope,
water logging than due to flood from the Ganga river along the Eldho and Jothiprakash, 2016). Up to about 1970’s heavy rainfall
bank of which it is situated. Especially during 2013 and 2016 there events used to cause water logging in low lying zones of urban areas;
was large scale inundation of many parts of Varanasi city both due but post 1970’s urban spread has increased at a very fast pace at the
to river flood waters as well as storm water logging. With the expense of water bodies, fields and other green patches outpacing storm
knowledge of field observations during these two (2013 and 2016) water drainage network (Gupta, 2007). Existing storm water drainage
flood years using Survey of India topographic maps with 2m in many of our cities, quite often, because of various reasons, is either
(north-western part of the city) and 5m (entire city) contour disconnected or is poorly maintained or is not maintained at all. And, in
interval and with 1m DEM created using 4000 Differential Global many cities, the city sewage almost doubles as storm water drainage
Positioning System (DGPS) points together with several spot aggravating the problem. The cities’ municipal solid waste (MSW)
heights and benchmarks from Survey of India topographic maps, mainly because of polythene bags has turned a major factor choking the
flood zones are digitized on very high resolution remote sensing sewage/drains causing water logging. It is not only due to apathy of
data. Contour flooding is shown at different intervals of elevation. city governing bodies but also due to lack of empathy of the citizens
The flood zones and the expected contour flooding are superposed towards their responsibilities, our cities quite often face the problem of
on the city map showing built up area. The extent of area, the water-logging mostly because of choking of and/or dysfunctional
number of houses and the number of people affected in each of the drains. With the expected climate change looming large over the globe,
flood zones is worked out. extreme rainfall events can become frequent leading to frequent floods
Index Terms: DEM, Flood plains, Flood zones, Storm water (Guhathakurta, Sreejith and Menon, 2011; Yenneti et al., 2016).In the
drainage, Urban Built-up, Urban floods. present paper water-logging and flood are used synonymously unless
I. INTRODUCTION specified and separated depending upon the context. The recent floods
in August 2018 in Kerala, Gujarat, Rajasthan, Uttarakhand, Assam are a
Storm-water logging in urban places of India has become as common as foreboding of what could happen due to extreme rainfall events.
floods in natural river systems due to peak rainfall events. Almost all Mumbai flood with 944mm of rainfall on 26 th of July 2005 and Chennai
large and medium sized cities in India are facing the problem of water flood with 490mm of rainfall on 1st December 2015, are attributed to
logging due to even moderate rainfall of high intensities leave alone exceptional rainfall and the failure and choking of storm water drainage
during peak rainfall events. The situation turns worse when cities along and faulty sewage lines (Gupta, 2007; Rajeevan, Lokanadham, Gupta
the river fronts and within the catchments of hilly torrents, receive and Nikam, 2009; Menon, Levermann and Schewe, 2013; Zope, Eldho
overflowing waters above the banks of streams and rivers. With and Jothiprakash, 2016).Mumbai and Chennai are no exceptions.
extraordinary rainfall events and with no flood prevention measures in Almost all the cities and towns in India suffer from water-logging due
place, floods in cities cannot be stopped. So is the case with water- to choking of drains or because of no drainage system at all. As it is,
the densely populated cities and towns in the Ganga-Yamuna plains
suffer due to floods/water-logging almost every year. The floods during
*
Corresponding Author

DOI: 10.37398/JSR.2022.660103 22
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August 2016due to very high and intense rainfall affected large number detail the geomorphology of Varanasi city and its environs. Varanasi is
of cities, towns and countryside as well causing huge loss of property basically situated over a natural levee and when there is a prominent
and lives. natural levee a prominent flood basin is a consequence. When there is a
The causes of floods are well known but the solutions are very difficult prominent flood basin receiving runoff from the hinterland (from over
to implement. Though floods cannot be stopped and though fool-proof the natural levee and from the high level floodplain in the west)
flood preventive measures cannot be put in place, one thing that can be development of small to large ponds is a natural occurrence. From the
done is management during flood to reach necessary help to the affected river the natural levee rises up starting from around 70m up to about 80-
and to alleviate the loss and suffering. There are many aspects to flood 82mamsl. It shows a prominent linear crest appearing literally as a
management. One of them is demarcation of flood zones as well as the “ridge”. From the crest towards the floodplain, it slopes gently into the
high and dry places and to generate information on the extent of area flood basin at around 75m altitude. After the flood basin, towards
likely to be flooded, number of households and people likely to be inland (away from the river), the floodplain rises up gradually to a
affected in the scenario of various flood levels (Fernández and Lutz, height of about 84m amsl. In the floodplains of large rivers, many
2010; Dewan et al., 2016). Such an information will help to at least plan small to medium affluents to large floodplain tributaries are a common
in advance about various steps to be taken to reduce the suffering and to occurrence. Here, in Varanasi, a medium sized floodplain tributary of
deliver timely help to the affected people. This exactly is the major the Ganga named Varuna flows across the northern part of Varanasi city
objective of the present study. This exercise is an attempt to: (i) map the and joins the Ganga at the city’s northeastern corner. Similarly, a small
flood and water-logging hazard zones in the city of Varanasi and its sized floodplain affluent called Assi passes across the southern part of
environs, (ii) to work out the number of houses and the people likely to the Varanasi city and joins the Ganga at the city’s southeastern corner.
be affected in the scenario of different levels/peaks of floods and finally Varanasi, the city of present study (Fig.1), witnessed second highest
(iii) to explain the various topographic reasons for flooding and water- flood at 72.94m amsl during August 2013 after the highest recorded
logging in Varanasi city. flood at 73.90m amsl in September 1978 (http://india-
Flooding in flood plains is a natural occurrence. Floods were once water.gov.in/ffs/hydrograph/).
considered a boon but have now turned into a bane. They have turned III. DATA AND METHODOLOGY
into a bane because the floodplains have been flooded by human The present exercise basically proceeds with direct field information
habitations. It is with the knowledge of recurring flood problem humans gathered through field observations during 2013 and 2016 floods in
chose to occupy the highest possible places. This has been the thumb Varanasi city. A digital elevation model (DEM) is created(Fig.2) using
rule in the development of human habitations within the floodplains. (i) about 4000 points collected with DGPS (Differential Global
With explosion in population numbers, habitations have gradually Positioning System) in RTK (Real Time Kinematic) mode for the
crawled into flood basins and lower level flood plains. Up to about southern part of Varanasi city,(ii) contours at 5m intervals, spot heights
1950s people forced into lower levels into the floodplains did not forget and bench marks from Survey of India’s map (of 2002)of Varanasi at
the thumb rule and used to construct their dwellings over 10 to 15 feet 1:20,000 scale and (iii) contours of 2m interval from a Survey of India
of piledup earthen elevation. But such a safety measure from flood was map (of 1972-73) of northwestern part of Varanasi city at 1:5,000 scale.
only within the reach of the rich and the poor remained lower down in Finally, from this DEM, contours are created at 1m interval (Fig.2).
the low-level floodplains. Gradually the thumb rule of ‘higher ground’ And, from these contours 8 classes of relief ranges are derived--60-65m,
has been forgotten or is given a go-by by even the rich especially in the 65-70m, 70-74m, 74-75m, 75-76m, 76-78m, 78-82 and 82-84m (Fig.3).
urban areas to reduce the construction cost. This is the paradox of the The first ever map of Varanasi city made by James Prinsep in 1822
times; people occupy the low lands, water bodies and river bed sand cry (Fig.4) has also been taken as one of the bases as it clearly shows the
foul about the flood and make hyper-critical comments against the old ponds, low agricultural (open) fields and estates and gardens along
government not coming to their rescue. with the then city built-up area. Most of these features in due course of
II. AREA OF STUDY time have disappeared under urban cover. In an urban set up, high roads
Varanasi city is locatedon the concave left bank of the river Ganga-- serve as dykes and may cause water-logging. But in case of Varanasi
82o93’E – 83o05’E and 25o24’ N – 25o38’N (Fig.1).A large chunk of the city with the exception of NH2 bypass passing through the southern
old part of the city is located over a natural levee. Prominent natural limit of the city, almost all other roads are low and are not above the
levees along concave banks of large meandering rivers in wide topographic surfaces. Of course, they were once considered as high
floodplains offer the highest possible ground for settlements. Over the roads at a slightly higher elevation than the adjoining built up areas and
years, from over the natural levee Varanasi has spread out into the flood fields. Several large to medium sized ponds present in the past (Fig.4)
basin/plain and, now, including its peri-urban area measures about 145 (as per 1822 map of James Prinsep) which were filled up subsequently
to 150km2. Though most of the floods in Varanasi are due to water and got converted into built up spaces are now flood prone. So, with a
logging because of choked, dysfunctional or no drainage/sewage combination of information from old and new maps, field observations
system, the situation gets aggravated when actually there is flood in the and DGPS points, flood and water-logging hazard zones are digitized
river Ganga and other smaller flood plain streams draining from west to over very high resolution (1m) remote sensing data (Fig.5).
east towards the city. Basically, the surface over which the city of
Varanasi is situated is a floodplain with general slope towards east and
north-northeast. Though floodplains are somewhat flat but they are not
altogether featureless. Prudhvi Raju and Pandey (2014) described in

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Fig.1 Location of Varanasi City Region in India

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Fig.2 Digital Elevation Model (DEM) of 1m resolution and 1m contour of study area

Fig.3 Contour flood zones and topographic profiles

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Fig.4 Digitized map of James Prinsep of 1822 showing flood risk levels of different map features

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Fig.5 Map of Varanasi city and environs showing urban built-up space with three samples showing (A) highly dense; (B) moderately dense; and (C)
sparsely dense urban features.

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Fig.6 Map showing water-logging and flooded areas in Varanasi city during 2013 and 2016.

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Fig.7 General Geomorphic Map of Varanasi City Region

Table I The area of extent, houses and people expected to be affected in

various flood zones
The extent of area, the number of houses and people affected at various Flood zone Area Household Population
levels of contour flooding are worked out from a detailed map of elevation (amsl) (Km2) affected affected
Varanasi urban space in each of the flood zones. Taking an average of 60-65 m 0.35 1459 9046
6.2 (city Census 2011) persons per household, total number of people 65-70 m 1.124 4738 29380
expected to be affected in each of the flood zones has been worked out. 70-74 m 16.99 71384 442582
The number of houses per square kilometer is worked by averaging 74-75 m 08.92 37496 232475
three sample areas (highly dense, moderately dense and sparsely dense) 75-76 m 21.27 89381 554167
of Varanasi urban space (Fig.6). The number of houses per sq. km. is 76-78 m 31.50 132323 820400
4,201. At this density of houses and with 6.2 persons per one house, the 78-82m 58.71 246633 1529123
number of affected people is worked out (Table I). A study on these
82-84m 0.0048 20 125
lines for Varanasi city had not been attempted so far and none has so far
Total 138.87 583435 361729
prepared flood and water logging hazard map for the present study area.

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that have occupied such low-lying parts at the mouths of these streams
IV. GEOMORPHOLOGY OF VARANASI: A FACTOR IN get flooded.
FLOODS V. FLOOD HAZARD MAPS
Two types of flood hazard maps are prepared in the present study. With
The floodplains of large rivers like the plains of the Indus, the Ganga, the understanding of flooded and waterlogged areas during 2013 and
the Brahmaputra etc., are normally prone to floods especially during 2016 floods, a flood hazard map is prepared through on-screen
rainy season in India. The floods could be due to breaching of river digitization over very high resolution data (1m Google Earth Image)
banks and/or due to overflow of water above the banks. Large rivers (Fig.6) Figure 3is a map prepared based on contour flooding. Most of
normally have meandering courses in the flood plains and where there the area of Varanasi city post 19th century has developed around the
are prominent meanders, natural levees are built up along the concave many ponds of Varanasi and within the flood basin. The old city of
banks and point bars on the convex bank side of the meander loops. Varanasi situated over the natural levee is normally not a flood prone
When there is a prominent natural levee, a flood basin on the leeward area. There is no record of river spilling its waters above this natural
side of the levee (away from the river towards the flood plain) is a levee during the20thcentury. Areas higher than 75mamsl remained high
natural occurrence (Fig.7). This elongated depression running almost and dry in the flood of 1916 and the subsequent floods of 1978, 2013
parallel to the main axis of the river is prone to flooding and also to and 2016.From James Prinsep’s map (Fig.4) flood risk levels are
water logging. Prudhvi Raju and Pandey (op cit) have given an inferred based on map features and flood risk level of each map feature
elaborate description of geomorphology of Varanasi city. is indicated in the legend. For example, the built-up spaces and estates
It is a lower level flood plain towards the south and southeast of and gardens are taken as low flood risk zones as they occupied the
Varanasi city which gets flooded by the flood waters of the river Ganga highest possible places and ponds (most of them filled up and covered
(Fig.7). From here water used to flow freely northwards towards the by urban landscape), tanks and marginal lands and water flow paths are
downstream reaches towards the confluence of Varuna river.With a taken as very high-risk zones. Open fields (as given in the legend in
segment of National Highway (NH2) bypass passing through the south Prinsep’s map) which are actually agricultural fields are taken as high-
acting as a flood dyke, the flow of water from the south towards north risk levels.In general, all the open fields, all the marginal lands and
into the flood basin is now reduced; but, still through many under- most of the ponds are covered by urban space and are liable for flood.
passes water flows slowly during high flood events. The railway DISCUSSION AND CONCLUSION
corridor and old NH2 serve as flood dykes on the west of the city which Most of theflood basin area like many other low-lying areas within the
reduce free flow of water into the flood basin from the high level flood city gets inundated during rainy season due to water-logging and not
plain from west. The east-west road running from Lanka towards DLW always because of flood waters of the river entering it. Flood in the city
serves as another flood dyke which prevents the free flow of water is caused mainly by the concentration water from the river Ganga
towards north into and through flood basin. In years 2013 and 2016, the (water coming from south and flowing towards north) and of other
flood waters flowed through many underpasses from under NH2 bypass streams flowing from west in to the flood basin. During heavy rains,
adding to the waters of the Assi and the Varuna rivers. Coupled with the there is backflow of sewage and subsequent water-logging because of
storm water coming from the west into the flood basin, most of the parts addition of storm water collection and concentration in low lying areas
of the flood basin get submerged under flood water. A vast built-up especially the flood basin zone.
tract of Varanasi city falls within this flood basin. There used to be With the flood of 1978 standing at 73.90m there was not much of a loss,
many large ponds within the flood basin (Fig.3). Most of these ponds and not as many houses as the number submerged in 2013 flood, were
have disappeared and occupied by urban built-up space and water submerged. The reason is, many areas submerged under flood of 1978
accumulates into all these occupied spaces during rainy season. There were then empty spaces or very sparsely built up. But, the same empty
used to be around 94 ponds/kunds in 1822 (Prudhvi Raju and Bhatt and sparsely built-up areas were gradually occupied by dense urban
Diva, 2016) and at present only 22 out of these 94 are left within the space by 2013. This is the reason, though the flood of 2013 stood at
area corresponding to the city area in Prinsep’s map. And most of these 72.94m, it resulted in much loss and suffering. The recent flood of
old water bodies left (and are present now) are kunds connected with August 2016 stood at 72.56m. Depending on the situation and location,
temples. As the general slope is towards the north (from south), there is the individual buildings at certain places (south east of Varanasi and
maximum concentration of water towards northern parts of the city along the rivers Varuna and Assi) in 70-74m zone were submerged up
coinciding with the flood basin. to about 2-3m above their plinth level (Plate I). In the same zone (70-
The natural levee gently slopes west towards the flood basin (Fig.3). So, 74m), the houses along the natural levee towards the Ganga river, the
the storm water gradually floods the city parts first in the flood basin waters touched the plinth of buildings. There was widespread water-
and with increase in storm water, flood would gradually submerge the logging in the interior of the city because of the backflow and blocking
crest of the levee too. Fortunately, the Ganga water never spilled over of sewage. As it is, the storm water drainage in the city is very
the natural levee in the recent times whose crestline stands at a general poor and is not properly interconnected. Most of the Indian cities and
elevation of 84masl at some places. There were about six medium to towns do not have separate storm-water drainage system and Varanasi
small streams (now just turned into flow paths)flowing across the city city is no exception. The old sewage doubles for storm water discharge
and cutting through the natural levee and flowing into the river Ganga. also.
Storm/flood water still flows through these paths and concentrates
downstream resulting in flooding of vast tracts of urban space. Where
these streams joined the Ganga there used to be prominent mouths with
moderate slope into the Ganga; and waters of the Ganga enter into these
‘once mouths’ of these streams. The houses and many religious places

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Fig.8 Hydrograph for Varanasi station showing different flood levels

during 4-7 September 2017

Going by contour flooding, a look into Table I shows that flood

standing at 74m would affect about 17 sq. km. of area and about 4.42
lakhs of people. With the expected climate change and a scenario of
extreme rainfall events becoming more frequent, a flood level between
74-75m is a possible occurrence and this just one-meter increase of
flood would alone envelope 2.32 lakhs of people in about 9 sq. km. of
area. In the worst scenario of flood going above 76m and above would
submerge almost three-fourths of the city. The type of flood zone maps
prepared for Varanasi city in this study will be of help in rescue and
Plate I Flood levels in Varanasi—Bhagawanpur in August 2016 (A), relief operations and to have an estimate of people and properties
near Assi in August 2013 (B), near NH2 bypass in August 2013 (C) and affected.
near Mangalagouri temple in August 2013 (D) ACKNOWLEDGMENT
This work is done under UGC SAP DRS-II Programme. We thank
The flood effect in terms of water entering the houses basically depends UGC for awarding this programme to the Department of Geography.
on the plinth elevation of houses. It is advisable to have at least 4-5m of Authors are also grateful to the Head of the Department for providing
plinth elevation from the local ground level in floodplain areas. all facilities to prepare various maps in the labs of Department of
Unfortunately, this general unwritten rule is more flouted than Geography, Institute of Science, Banaras Hindu University.
followed! Water-logging because of sewage backflow and storm water
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