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Chapter 7

Causes of Flood

7.1 Causes of Flood

7.1.1 Natural Causes

Flood is such a natural phenomenon that is uncontrollable and, to some extent, unpredictable.

Flood basically a natural fluvial event especially in the late mature and old stage of the cycle of

erosion. From such statement it needs not to be interpreted that no flood events are experienced

by the youth or early mature stage of the fluvial cycle. In most of the periods the upper part of

this basin remains flood free. In lower part of Mayurakshi basin including eastern part of

Birbhum and entire Murshidabad district, there is a well bred geo-physical environment to invite

and nourish the flood devastations. Moribund deltaic morphology, poor drainage condition,

bifurcation of river Mayurakshi, huge deposition in the river bed, large number of braids, highly

winding channel, lack of forest coverage, long standing siltation within the wetland command

area, effect of external drainage morphology, poor infiltration capacity of the soil, highly

concentrative rainfall etc. collectively responsible for intensive flood situation. As soil remains

already saturated with moisture before peak monsoon, any additional input of heavy rain is

enough to create a devastating flood (Bandyopadhyay, 1992).

Key Words: Natural Flood Vectors, Anthropogenic Flood Vectors, Impact of

Dam, Barrage and Embankment on Flood

Chapter -7, Causes of Flood

126

7.1.1.1 Huge Rainfall within Very Short Range of Time

The most important meteorological and climatic factor, inducing run off processes on earth is

precipitation (rain and snow), propelled by large scale (macro and synoptic scale), small scale

(meso and storm scale) precipitation processes (Hirschboeck et al., 2000).

Out of total rainfall almost 85% rainfall occurred within 3 to 4 monsoon months of the

year. About 60 to 70% rainfall was happened within very short period of time e.g. 3-4

days during 1956, 1970, 1973, 1978, 1999, 2000, and 2007.

Arrhythmic short range outburst interleaved by long lean period is recent trend of Indian

monsoon. For example during 23rd

to 25th Sept., 2007 amount of rainfall was 174.8 mm.

recorded by Kandi Meteorological Station (at Lower catchment) and large amount of rainfall in

the Chottanagpur area and the Rarh region of West Bengal (Upper catchment) were mainly

responsible for flood.

About 872.4 mm. or more rain within 3 days (19th

to 21st Sept. 2000) was happened only in the

lower segment of the basin area which is highly responsible for acute flooding in the lower and

middle catchments ever seen by the present dwellers. About 358.2 mm. rainfalls between 9th

to

11th July of 2006 and 435.4 mm. between 9

th to 13

th July of 2007 had beaten the region with

black and blue in shape of flood surge.

In figure 7.1 rainfall pattern during two devastating flood years 1978 and 2000 have been shown

in relation to average rainfall. Very high concentration is noticed in September which is far

greater than average rainfall and massive flood were recorded on that period.

Chapter ‐7, Causes of Flood

127

Figure 7.1

7.1.1.2 Poor Drainage Condition

It has been observed that lower part of Mayurakshi river basin has been suffering under poor

drainage. Large number of rivers like Kuya, Banki, Hizuli, etc. have concentrated in Hizole

wetland and influxed with Dwarka Babla river within very short range of space. So, in general

situation, Mayurakshi itself becomes brimful with its own huge volume of water as well as it

doesn’t have any further ability to carry out any extra water debouched by the tributaries like

Kuya. Average gradient of the confluence region is 1: 400 which is further reasonably low. Due

to such poor physiographic slope swift water movement is beyond expectation.

Banki, Hizuli, Mor, Kyua, Beli etc. river are mixing with Mayurakshi near to confluence area.

Cross sectional area of the tributaries are 563.65 sq.m. more than master Mayurakshi river (table

7.1). The slope of the confluence streams in this region is almost same but cross sectional

differences create difference in flow volume. If cross sectional area of some other micro streams

those exist in this region is calculated the surplus cross sectional area will be 476.13 sq. m.

greater than master stream. Therefore, the water of the tributaries is not freely influxes into the

main river and flood situation is getting appeared.

0

100

200

300

400

500

600

700

J F M A M J J A S O N D

Rai

nfal

l in

mm

.

Month

Rainfall Pattern in Flood Years

19782000Average

IndexRainfall distribution


128

Table 7.1: Comparative Cross Sectional Area of Master Mayurakshi and its Confluence

Stream Tributaries

Inceptor river Area (sq.m.)

W x D

Tributary

rivers

Area (sq.m.)

W x D Remarks

Mor or

Mayurakshi

22.5x3.89

=87.52

Banki 17×2.77 = 47.09

(563.65-87.52) =

476.13 sq. m.

Extra cross sectional

area of the

tributaries than

master Mor

Hizuli 13×1.83 = 23.79

Dwarka 39.5×7.78 = 307.31

Kuya 35×3.78 = 132.30

Beli 15.5×3.43= 53.16

87.52

563.65 High flood

possibility

Moreover, large number of river segments has narrowly spaced and interwoven manner in the

confluence zone of Mayurakshi river in such a fashion that no one could find their paths other

than disappear to the extensive Hizole wetland area.

7.1.1.3 Effect of Bhagirathi and Uttrason

Mighty Bhagirathi River (master stream of Mayurakshi river) is flowing 2 to 4 km. eastern off

course of Dwarka Babla river (after mixing with Dwarka, the channel known as Dwarka Babla

river) like a Yazoo pattern of flow. Uttarasan river connects Dwarka-Babla river with Bhagirathi

river, which flowing few km. south east of Dwarka confluence point. This pattern of river

network influences the flood intensity in different ways (Pal, 2010).

i. There is very little relief variation (1 m. to 1.5 m.) between Dwarka-Babla river and

Bhagirathi river as well as very meager differences of water level. So, during monsoon

period as the elevation of water level in Bhagirathi rises up, huge water carried by the

tributary (Dwarka-Babla) does not get free access to meet with master river. Similarly,


129

swelled water level in Dwarka-Babla river does not facilitates Mayurakshi river to pour

huge volume of water and therefore inundate the lower catchments.

ii. Uttarasan is an excellent bypass route of river Dwarka-Babla river which bypasses huge

water directly to Bhagirathi River (fig. 7.2). Due to little relief differences between

source to mouth of Uttarasan river, during monsoon period excess water of river

Bhagirathi or released water from Farakka reversely enters into the river Uttarasan like

back thrust, which hampers the normal bypassing system from Dwrka-Babla river to the

Bhagirathi river. Strong eddying and helical flow in Uttarasan river during monsoon are

the empirical evidences of such flow character. Moreover, this connecting channel today

has become so chocked that its carrying capacity has lost. However, the external effects

to some extent directly responsible for such dreadful, long durated flood.


130

Source: Toposheet of SOI. Fig.7.2

7.1.1.4 Huge Siltation and Sand Deposition in the Wetland and River Bed

Human induced land use change, incremental losses of wetland, urbanization etc. have greatly

augmented runoff and associated risk of flooding (Bandhopadhyay and Mallik, 2005,

Rasmussen, 1994). Lower portion of this basin in Murshidabad is a natural storage unit but

steady deposition has forced it to lose its retention capacity.

Similarly, the rivers like Mayurakshi, Kuya, Bakreswar have lost their carrying capacities and

competencies in substantial degree. Due to deposition in lower portion and loss of carrying

capacity of the rivers are greatly responsible for flood severity. Some places of Mayurakshi river


131

course, point bar and sand bar deposition are so active that river flow often choked. Sand clogged

rejected or kana channel near Narsingpur (Site no.7) clearly makes this argument stronger.

Plate 7.1 at Narsingpur, Birbhum Plate 7.2 at Boipur, Birbhum

Plate 7.3 at Satpolsa, Birbhum

7.1.1.4 Channel Shape

The magnitude, flood frequency, duration of flood flows etc. depend on the valley morphology

(Wohl, 2000). Areal morphmetric analysis reveals that the cross sectional areas of the river

between upper, lower middle and near confluence of the channel with variety of width. Its not a

normal character of a channel as river flows towards its maturity the width generally widening.

But here the abnormality has noticed that at middle part of the basin the channel width is so wide

(at Narsingpur 470.6 m., at Sainthia 519.7 m, at Harishchandrapur 424.9 m) but near confluence

just narrow down (at Nalghosa 16 m), (vide figure 3.16) which is also an important cause for

flood.

Meanders and more sinuosity raised the probability of flood. The sinuosity index of this basin is

4.145 which is quite high as we know that sinuosity index more than 1.5 means meandering river

course. So, here we found a positive relation between flood and meandering.


132

Plate 7.4 wide river valey at Harishchandrapur Plate 7.5 narrow river valey at Nalghosa

7.1.1.6 Bottleneck Channel Shape and Channel Sinuosity

Generally the width of the channel gradually increases downstream but the situation is reverse in

case of Mayurakshi river. Noteable to mention that the thalweg of Mayurakshi river has tendency

to shift right ward, that’s why the width of the right bank from thalweg line is lesser than left

bank width (fig. 10). At the middle catchment near Sainthia, Boipur the channel width is 519.9

m. and 437 m and cross sectional area is 2012.013 sq. m. and 1520.76 sq.m. respectively. But at

the confluence area the width and cross sectional area is 15.5m. and 51.615 sq.m. respectively

(table 7.2, fig. 3.16 ). Due to such bottle neck like cross sectional pattern, the huge amount of

water coming from upstream do not getting enough space to drain out during full fledged

monsoon. Therefore, water certainly spreading outward and devastatingly inundates the entire

area.

Table 7.2: Cross-sectional pattern and potential discharge ability along Mayurakshi

downstream.

Do

wn

stre

am

Cross Section Sites Width Depth Cross sectional

area(sq.m.)

Santhia 519.9 m. 3.87 m. 2012.013

Boipur 437 m. 3.48 m. 1520.76

Near Saspara 51.2 m. 2.13 m. 109.056

Confluence 15.5 m. 3.33 m. 51.615

Source: Field Measurement


133

7.1.1.7 Sand Terrace or Sand Shoulder

Thick sand made terrace like features developed at the bank foot is called sand terrace or sand

shoulder. From Sainthia to Boipur there is discontinuous 17 km. lengthy thick sand terrace in

two foots of the River banks. Its witdh is about 5 to 12 m. and thickness is 1.3 m. So, only

within the stretch of Sainthia and Boipur the volume sand in the sand terrace above channel bed

is about 1,87,850 cubic m. sand. These voluminous sand depositions resist the normal flow

character of this River and make the drainage poorer.

Plate 7.6 Sand terrace in Boipur Plate 7.7 Extended sand shoulder (width: 28m.), at Ektala

7.1.2 Anthropogenic Causes

Human induced regulation of flows has a history of about 8000 years, but its extent increased

spectacularly over the last 100 years as well as river behaviour also changed due to intrusive

human activities (Dunbar and Acreman, 2001, Sengupta, 2000). Similarly, modern flood is the

combination of natural system and human interaction system (Kates, 1971). Population pressure

is gradually increasing and to keep parity with the needs of human being, there has been a

parallel attempt to rule the river flow and to force the rivers surrender to the feet of human

civilization. For fulfilling the dream, lofty embankments have built up alongside the rivers or

dam or barrage across the rivers, or sometimes diversion of the river course or canal. Through

dam, barrage or river lift irrigation human beings have attempted to produce substantial volume

of crops. Multipurpose river valley projects like DVC, (Damodar Valley Corporation), Sutlej

project in India have been developed to gain an integrated package of profit in diversified


134

ground. Such apparently beneficial activities today in many cases has been yielding a series of

consequent curse like boomerang effect. Few relevant aspects here have been pointed out briefly.

7.1.2.1 Lofty Embankment Construction

Present day’s river is mostly guided by the arrogant signature of the technological advancement

of the engineers e.g. embankment. In lower part of Mayurakshi and its major tributaries are

regulated by river embankments and most of the embankments are 4.26 m. to >6.40 m. in height.

Almost every 2-3 years interval, elevation of the embankment is getting rise in parity with rising

flood height. During 2007 centre pool of the Mayurakshi and Dwarka-Babla embankments have

been raised up almost about 0.914 m. (vide Plate 7.8 & 7.9).

Plate 7.8 at Sundarpur, Murshidabad Plate 7.9 at Sanspara, Murshidabad

Table 7.3 Breach of embankment

Year No. of breaching point

1991 1

1999 3

2000 5

Source: Directorate of Irrigation and Waterways Department, West Bengal-2008

Noteworthy, (a) Constructional material of the river embankment are very fragile e.g. loose sand

or sandy soil. Huge sands have been employed to erect the embankment along the river. So, how

much venturesome it may be is really perceptible to any common people (Ahmad et al., 2001,

Kale, 1998) (b) Base width of the embankment should be far wider than the apex but in reality

EMBANKMENT

EMBANKMENT


135

there is no significant difference base and apex width therefore vulnerable for collapsing. (c)

Moreover, soil used for embankment, is just collected from the base of the embankments, as a

result deep scours have been developed at the off base of the embankment. These scours contain

water like marshy land almost all through the years and this situation is weakening the basement

of the embankment increase the threats of vulnerability for easy breaching. It again creates

potential hazards for sand splay in the embankment breaching points. (d) Due to embankment as

the geo materials of the river is not getting escape to spread outside the channel, continuous

accretion of sand in the river bed raises the bed level and reduces the carrying capacity of the

channel. Embanked channel even sometimes is not able to retain the water. Therefore by

embankment shifting far from the channel and increaseing the width of embanked channel the

holding capacity of swelling water during monsoon period has increased (see fig. 7.3). If

embankment is the ultimatum its base should be much wider than apex to resist huge water

pressure.

Figure 7.3 shows the cross section pattern across the river Mayurakshi at Sanspara (near Kandi,

Murshidabad). In this cross section old embankment remains as discarded one, because after

breaching of the embankment river has extended its floodplain, so, new embankments are being

constructed with much more height at some distance away from the river.

Fig. 7.3


136

7.1.2.2 Presence of Zamindari Gher Bundh

Before independence Zamindars had built up several zamindari gher bundhs to save their

agricultural farmyard from flood invasion. Few significant gher bundh in the Hizole beel area

and surrounding area are 16 like Bhageer gher, Piprikuri gher, Tharkuramichak, Hazar bigha

gher, Sahebergher, Amtala gher, Nabab-er gher, Naru Seik-er gher, Chorkir gher, Bheramara

gher, Andulia gher, Aarasar gher, Tudur gher, Ahari Moraler gher, Gudurkhola gher, Surya

Khali gher, Bhabanandapur gher, Kaokhali gher Sapmara gher, Babur gher, Charghari gher,

Rahatulla gher, Amtala gher, Naru Seik-er gher, Kodalmari gher etc.

All the parts are not completely present here but the remnant still existing. About 59 km. long

gher bundh was present upto 1970 but latter on more than 50% gher bundh have been eradicated

without any proper safe guard. These remnants are not able to resist the flood rather hinder the

free trespass of water in the lower region as well as drainage quality is very much worst specially

in the Hizole beel area. Moreover these are more influencing for ferocious flood as per the

perception of the people in this region.

7.1.2.3 Construction of Dam and Barrage

Massanjore Dam was established in the year of 1954. Hydrological characters of this dam

depend on the rainfall character of this region. The length of the dam is 661.41m. and height

from the tholweg point is 47.24m. This manmade artificial dam has 21 Sluice gates (width of

every gate is9.14m) and the total water discharge capacity is 35,000 cusec. The highest water

level of the reservoir is 121.31m. and projected flood level is 123.14m.

Massanjore dam sometimes plays vital role to subside flood, but often it itself caused for flood

vector. In September, 1999 (24th

to 26th

Sept.) more than 5,00,000 cusec water released from

Massanjore dam which caused massive flood on Mayurakshi river basin. It was the highest water

were release from this dam within its lst 45 years history. Between 24th

to 26th Sept. upper

catchment of Mayurakshi river received 465.6mm. rainfall. But, in Sept. 2000, (18th to 22

nd Sept.)

it broke all previous records as more than 6,50,000 cusec water were released which caused

flood intensification. It is evident fact that water release all on a sudden and peak water level is

getting raised. Between 18.9.2000 to 21.09.2000 upper catchment of Mayurakshi river received

859mm rainfall. (Ref. Mayurakshi Jaladhar Prakalpa, published in May,2006).


137

Another hydro-engineering evidence on Mayurakshi river is Tilpara barrage, located 49 Km.

downstream from Massanjore dam. Tilpara barrage was established on 1971. The length of the

barrage is 308.76m and having the water discharge capacity of 3,00,000 cusec.

Massanjore dam and Tilpara barrage of Mayurakshi river has significant impact on flood

intensification on Mayurakshi river basin. Here fig. 7.3 (vide Appendix No.4-22) shows the

monthly release of water from Massanjore Dam in different years. Therefore, the discharge

condition of Massanjore dam and Tilpara barrage should be reviewed.

Plate 7.10 Massonjore Dam Plate 7.11 Massonjore Dam

Plate 7.12 Tilpara Barrage Plate 7.13: Tilpara Barrage


138

7.1.2.4 Water Flow Character in Massonjore Dam

Fig. 7.4

It is very clear from fig. 7.4 that maximum water was released from Massonjore dam in the

month of September in different years. In the year of 2000 and 2006 huge amount of water were

released and which caused a devastating flood in lower Mayurakshi basin. From the study it is

also find that the major flood period occurred in different flood years of that basin in the month

of September. So, there is a positive relationship with flood and water release from Massanjore

dam. Here, also an analysis done with the relationship between rainfall and flood discharge from

Massanjore dam. There is a very good positive relationship between flood discharge and rainfall

which is indicated by positive linear regression curve(r= 0.57) (vide fig. 7.6).

Peak discharge graph of 15 years (vide fig. 7.5) has also proved that the abnormal release of

discharge on 21.09.2000 is responsible for massive deluge.


139

Fig. 7.5

Fig. 7.6

y = 2727.x + 29977R² = 0.047

020000400006000080000

100000120000140000160000180000200000

21.0

7.90

15.0

9.93

6.09

.94

28.0

9.95

26.0

8.96

02.0

9.97

11.0

9.98

26.0

9.99

21.0

9.20

00

27.0

9.02

8.10

.04

28.0

7.05

27.0

9.06

27.0

9.07

21.0

8.08

Dis

char

ge in

cu

sec

Date

Peak discharge from Massanjore Dam

Peak discharge in cusec

Linear (Peak discharge in cusec)

y = 372.8x - 49647R² = 0.57

-100000

0

100000

200000

300000

400000

500000

600000

700000

0 200 400 600 800 1000 1200

Flo

od

dis

char

ge in

cu

sec

Rainfall in mm

Relation between Rainfall vs. Flood discharge


140

Fig. 7.7

Massanjore dam across Mayurakshi river, Tilpara barrage across the same river have irrefutable

effects in the downstream area of this river basin. Flood-1999 and flood-2000 are two

memorable floods were happened because of sudden outbreak of dam and barrage discharges.

During 2000, within 5 days (18th

to 22nd

Sept.) Tilpara barrage released 52,49,884 cusec. water

and consequently the residents experienced a satanic, threaten some flood. In this context it can

be cited out that almost 83% of total flood run off generated in the Mayurakshi basin in Sept.,

2000 were the contribution from the unregulated catchment, as against the relatively unassuming

outflow from the spillway of the Massanjore dam and the Tilpara barrage. As reservoirs are filled

to their bursting points during heavy and incessant rains of Sept. 2000, huge volumes of water

are released abruptly from the Massonjore and other barrages traced a similar grim picture of

devastation in the downstream reach of Mayurakshi river basin (Pearce, 2001, Dasgupta, 2002).

Sudden discharge from Tilpara barrage of Mayurakshi river contributed huge water and water

level dramatically raised far above the extreme danger level. Interestingly the water level, again

just after sometimes, had dropped down (Fig. 7.8 & 7.9). It is because of breaching the

embankment at five points (year 2000) along Mayurakshi River and the excess water was being

dispersed through old course of Mor river.

Dam storage not only affects the downstream area but also some parts of upstream areas

neighbouring to the dam. Back thrust of water flows up to 2 km. upstream of Massanjor dam.

15

18

21

24

27

30

33

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

WA

TER

LEV

EL IN

M.

YEAR

Year wise Peak Water Level in Mayurakshi River

NARAYANPUR

PANCHTHUPI


141

This condition encourages flood devastation in the surrounding upstream areas. Another fact is

that deposition rate within the dam and barrage is so high their longevity may not exceed next 75

years. There is 48% shortage in dead storage of Masanjore reservoir and 12.5% shortage in live

stotage (M.K. Saha,2011) . Such growing loss of retention capacity immediately accelerate flood

condition in the downstream as well as some portion of upstream catchment.

Figure 7.8 and figure 7.9 (vide Appendix No. 2) prove that flood level at Narayanpur gauge

station were far above the extreme danger level during 1978 and 2000 which indicates the

massive ferocity of flood character. It is also notable that, during 2000 after recoding flood

height 31.2 m. on 21st September the entire gauge station was collapsed and there was no

possibility for farther recording.

Fig. 7.8

Fig. 7.9

2223242526272829303132

Flo

od

leve

l in

M.

Date & Time

Flood level at Narayanpur guage station in 1978

Flood level (M.)

D.L. (M)

E.D.L. (M)

25.09.78 26.09.78 27.09.78 28.09.78

2223242526272829303132

Flo

od

leve

l in

M.

Date & Time

Flood level at Narayanpur guage station in 2000

Flood levelD.L.

19.09.00 20.09.00 21.09.00 22.09.00


142

7.1.2.5 Loss of Water Bypassing Discharges

Due loss of distributaries of Mayurakshi river, water bypassing system has damaged for a large

extent specially during flood period. Before the construction of embankments flood water could

bypass through the distributaries of the Myurakshi but after that event most of the distributaries

have lost their identities due to channel clogging and less supply of flow from the main stream.

Moreover due to lack of proper maintaining these embankments have broken at many parts and

the remnants of them remain sporadically. Those old channel courses are now using for

cultivation and frequently flooded. A typical example has observed at Sundarpur (254 km

downstream from source) there was a distributor of Mayurakshi river which used to connect with

right hand flowing Kopai or Kuya river. So, during flood period a significant amount of water

used to bypass through it and thereby reduced the pressure of water in Mayurakshi river. But

after making embankment along Mayurakshi river the river unfortunately clogged. So, this

bypass route has totally damaged and has lost its capacity to diverge water to other channel. The

following plates (plate 7.14, 7.15, & 7.16) show some glimpse of sand clogged distributary near

the point of embankment. Vide figure no. 7.9 and 7.10 shows the changing channel form and

landuse pattern.


143

CHANNEL PATTERN OF MAYURAKSHI RIVER AT SUNDARPUR AND SURROUNDING: YEAR 1972

Source: Toposheet of S.O.I. Fig. 7.10

Source: Google Earth, 2012 Fig. 7.11


144

Plate 7.14: lasting channel bed Plate 7.15: channel bed converting Plate 7.16: River bed modified into cultivable land by agricultural field

7.1.2.6 Huge Siltation and Sand Deposition

Huge sand deposition is very common in Mayurakshi river. It is due to embankment with great

height has raised the rate of siltation and gradually flood height also increased. If we consider the

depth pattern of the river, then we see after the Masanjore dam depth of the river has reduced due

to huge sand deposition. After considering perception study of the bank dwellers it is found that

on an average 0.6 meter depth of the river bed has decreased within 50 years.

Table 7.4: Comparative depth pattern of Mayurakshi river.

Site name Distance from

Source

Avg. Depth in M.

(2011)

Avg. Depth in M. (50 years

Before)

Latasore 1 Km 0.61 0.5

Manjura 4 Km 0.85 0.72

Nunihat 46 Km 2.9 2.05

Singari 100 Km 4.1 3.6

Ektala 110 Km 4.1 4.7

Narsingpur 155 Km 2.2 2.9

Sainthia 171 Km 0.94 1.9

Boipur 179 Km 1.83 2.22

Gunutia 198 Km 1.1 1.9


145

Sundarpur 215 Km 0.85 1.4

Harischandrapur 238 Km 1.4 1.95

Sanspara 251 Km 0.78 1.67

Nolghosa 266 Km 1.2 1.64

Ratanpur 288 Km 5.1 5.55

Source: Perception study among the bank dwellers.

Fig.7.12

7.2 Flood Trend and Causes in Victims’ Perceptions

From the analysis of previous flood records it is clear that flood tendency has been increasing

over time (vide fig.6.6, 6.7, 6.8). Now the question what the people are thinking about flood

trend and what are the causes of flood. As per the perception of flood victims and bank dwellers,

in upper catchment the flood is caused by dam and barrage. Due to higher elevation and steeper

slope, possibility of flood is less but back flow from Massanjore dam creates inundation in this

areas. Village like Kuthibari, Amba were inundated for back flow of water from Massanjore

dam. People from any corner of the basin as upper, middle and lower catchment of the river


146

condemn dam and barrage as major flood vectors for Mayurakshi basin. More than 80% people

(with the analysis of 150 questionnaires survey of 16 flood affected mouzas of different

catchment) think the ferocity and frequency of flood in the Mayurakshi river basin is due to

Massanjore dam and Tilpara barrage. Due to sudden discharge of huge volume of water from

dam and barrage the intensity of flood was increased many times more. The loss of property also

increased simultaneously. Near about 42% flood victims of middle and lower catchment of

Mayurakshi river basin also denounce embankment along river bed also a major factor for

intensive flood of Mayurakshi river basin. A detail analysis of village level questionnaire survey

has been done in chapter 9.


147

Major Focusing Points:

1. Massive rainfall within a short range of time on Mayurakshi basin causes flood about

672.4 mm. or more rain within 3 days (17th to 19st Sept. 2000) was happened only in

the lower segment of the basin area which is highly responsible for acute flooding.

2. Retention capacity of Mayurakshi river near confluence is very low than tributaries of

it which also disturb to get free access of water to drain quickly which also increases

the flood probability.

3. Poor drainage network at the lower catchment and channel shape are the major

natural flood vectors.

4. There is 48% shortage in dead storage of Masanjore reservoir and 12.5% shortage in

live storage.

5. Sudden release of huge discharge from Massanjore Dam and Tilpara Barrage has

increased and intensify the spatial extent of flood.

6. Depth of the main channel as well as the tributaries is reducing due to siltation.

7. Embankment cannot resist the massive flow of river during monsoon. So, breaching

of it causes flood.

8. Embankments block the inter-linking channels for free flow of flood water and

consequently long stagnation periods occur.

9. People consider embankment, dam and barrage as the false security to flood.

chapter 7shodhganga.inflibnet.ac.in/bitstream/10603/85044/13/13. chapter 7.pdf · chapter 7 causes...

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