Salient Features of India constitution especially power and functions
Lecture 1 flood
1. Presentation on
FLOOD IN BANGLADESH:
VIEW AS A DISASTER
Composed by
H.M.A. Mahzuz
Assistant Professor (PhD Fellow),
Department of Civil and Environmental
Engineering,
Shahjalal University of Science & Technology
Sylhet,
Bangladesh.
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2. Lecture OutlineLecture Outline
1) Major river system in Bangladesh
2) Definition, types and periods of Flood
3) Flood Affected area
4) Causes and impacts of flood
5) Impacts on some major floods in Bangladesh
6) Flush Flood in Sylhet
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3. Introduction:
Bangladesh is a land of rivers & cannels. Their
number is more than 250. The total river area is about
9380 Km2, which 6.3% of the total area of our country.
According to the geological point of view Bangladesh is
located in such a zone that can be affected by flood easily.
Bangladesh is a low plane level country. Its geological
& climatological situations along with the existence of
immense rivers & canals have combinedly made it more
flood prone. About 15-20% of the total land area is hilly.
The rest of the country is almost plane & mainly originated
from river carried alluvium soil.
Over this country three large river systems are flowing:
1) Ganges-Padma system,
2) Brahmaputra-Jamuna system, &
3) Meghna system.
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6. The drainage areas of the three major rivers areThe drainage areas of the three major rivers are
mentioned belowmentioned below::
Name of river Length in
miles
Area covered
in sq miles In
Bangladesh
Area covered
in sq miles
Out of
Bangladesh
Total covered
area in sq.
miles
Ganges 1600 19000 3,78,000 3,97,000
Brahmaputra 1800 18000 2,06,000 2,24,000
Meghna 590 14000 17000 31,000
Total drainage area
652000
This area is 11.64 (=652000/56000) times higher than the area of Bangladesh
During the annual monsoon period, the rivers of Bangladesh flow at about 140,000
cubic meters per second, but during the dry period they diminish to 7,000 cubic meters
per second.
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7. 77
Basin areas of the three major rivers:Basin areas of the three major rivers:
12. Definition of Flood:Definition of Flood:
From the ancient time, flood has been viewed as a natural calamity
caused mainly by overflowing of banks of river due to excessive rainfall in
a river basin or in the upstream of river basin. The flood normally moves
from the upstream to the downstream of a river in the form of solitary
wave. Therefore, it has an advancing front, a pick & the recession limb. As
a flood wave moves down the river channel, the depth of water increases
gradually at a station & water spreads over the section of the station so
long the peak of Floods may be categorized as:
1)Flash flood
2)General (monsoon) flood
In case of flash flood which normally occurs in hilly rivers, does
not give enough time for evacuation or transfer of valuable properties &
lives to safe places. As a result most of the damage are done by advancing
front of such flood. Once the initial damage is done, the rate of damage
slows down. Flash floods usually have short duration, supercritical velocity
& very high degrading effects. 1212
13. General floods normally advance quite slowly
contrary to flash floods. So, it might be possible for people to
get enough time for moving out from the flooded area to safe
places with their movable properties, animals & family
members. As such flood advances gradually, it attains peak
height slowly & also recedes from a place quite slowly.
Therefore the devastating effect of general flood not only
depends on advance, but also on the peak height & on the
duration of flood.
There are also some other forms of flood such as:
a) Flood from tides,
b) Flood from cyclone
c) Flood from Tsunami
1313
14. Periods of flood:
Flood can be seen three times in a year in Bangladesh:
1)During April-May the melted water from the Himalayas & the
rain water from Assam & Tripura are conveyed by the river Surma
(mainly) may effect Sylhet division & some other river bank areas (also
called flush flood).
2)During July rainy season exists. Moreover the rain water from
India conveyed by the rivers Padma, Jamuna, Surma & others can
combined to give the birth of any dangerous flood. Examples: Floods of
1998 & 2004.
3)During August-September water carried over by the Padma,
Meghna can also cause flood. Example: Flood of 1988.
1414
18. Low elevation of coastal
communities (LECZ)
The average land
elevation is about 7.62
meters (25 ft.) above
mean sea level whereas
for coastal and offshore
island is about 1.5 meters
(approx.) above mean sea
level and as such major
portion of the waterways
are under tidal influence.
1818
19. Causes of Flood in Bangladesh:Causes of Flood in Bangladesh:
1919
20. 1.1. Low general topographyLow general topography::
2.2. High monsoon flood through principle channelsHigh monsoon flood through principle channels
3.3. Siltation of the principal distributaries:Siltation of the principal distributaries:
4.4. Overbank spilling of the rivers:Overbank spilling of the rivers:
5.5. Flood control measures in upper reaches:Flood control measures in upper reaches:
6.6. High rainfall:High rainfall:
7.7. Backwater effects of tides of Bay of Bengal:Backwater effects of tides of Bay of Bengal:
8.8. Rise of the mean sea level (MSL):Rise of the mean sea level (MSL):
9.9. Topographic features controlled by geological factors:Topographic features controlled by geological factors:
10.10. Earthquake:Earthquake:
11.11. Peak flood synchronization in the Ganges & the Brahmaputra:Peak flood synchronization in the Ganges & the Brahmaputra:
In brief:In brief:
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21. Risk Factors with respect of WaterRisk Factors with respect of Water
Induced DisasterInduced Disaster
Low lying area, 80% area below 9.0m
Flat topography, mild to low slope (10-20cm/km)
Located at the outfall of 3 mighty rivers
Large coastal exposures, east to west along the south
High population density
Infrastructure development, rapid/ unplanned urbanization
Limited coverage of flood forecasting
Limited disaster preparedness capability, e.g limited flood shelters
2121
Because of geographical location, low topography, deltaic plain, complex
river system, high population, agriculture dominated economy, huge losses
due to flood, present level of preparation etc International bodies including
UNDP has identified Bangladesh to be the most vulnerable country in the
world with respect to climate change and disaster
23. In the following section a step is made to represent theIn the following section a step is made to represent the
impacts of flood in brief:impacts of flood in brief:
Names Tangible Intangible
Direct losses • Loss in lives & crops.
• Loss in transportation &
hydraulic structures.
• Loss in business
• Scarcity of food &pure
drinking water
• Sanitation problem
• Social life is injured.
Indirect losses • High price of daily used goods
• Losses in business &
production
• Closing of educational
institutions
• Damage to biodiversity
• Foreign dependency.
Direct gains • Relief
• Reconstruction of structures &
communication
• Foreign aid.
• Soil fertility
• Breeding place of fish.
Indirect gains • Experience.
• Better flood forecasting.
• New thinking for future flood
protection.
• Foreign sympathy.
• Implementation of better
technology.
2323
24. The following table can also help us to understand what amount of damage
is done by the floods of recent years:
Year Loss (in brief) Comment
1954 1)0.6 million metric tons of crop is
damaged,
2)total estimated loss is 1200 cores of taka
85,300 Km2
of the country was flooded
1963 -------- 29.04% of the country was flooded
1969 ------- 27.89% of the country was flooded
1974 1)30000 people had died. 35.44% of the country was flooded
1987 1)1700 people had died,
2)1.5 million metric tons of crop is
damaged,
3) total estimated loss is 10,000 cores of
taka
38.61% of the country was flooded
1988 1)1600 people had died,
2)2.5 million metric tons of crop is
damaged,
3) total estimated loss is 12,000 cores of
taka
60.62% of the country was flooded
1998 1)918 people had died,
2)2.2 million metric tons of crop is
damaged,
3)total estimated loss is 20,000 cores of
taka
60.6% of the country was flooded
2004 See below 38%of the country was flooded
2424
25. Flood: As a natural disaster
Flood of 1988: Its range & hazards at a glance:
1) Affected district: 52 (out of 64)
2) Affected upazila: 318 (out of 460)
3) Affected area: 84059 sq. km (60.62% of total country area)
4) Death: a) By flood: 1410 b) By diarrhea: 387
5)
6) Affected people: 30 million
7) Crop damage:
8) Full: 3.97 million ha
9) Partial: 3.17 million ha
10) Seed bed damaged: 13000 ha
11) Loss of cattle: 172000
12) Road damaged: 1) Paved: 2935 km & 2) Earthen: 65892 km
13) Bridge/ culvert damaged: 2754
14) Affected railway & rail bridge:
15) Meter gage:359 km & 28 in number
16) Broad gage: 279 km & 6 in number
17) Educational institutes: 1) Full: 1367 & 2) Partial: 7114
18) Industrial damage: About 14000 industrial enterprises have been reported to be damaged
19) Foreign aid was needed to rescue, rehabilitate & health care.
2525
26. About Flood of 2004: Its range & hazards at a glance:
After the independence Bangladesh had faced several
dangerous floods such as flood of 1974, 1988, 1998 & 2004.
Though the flood of 1988 was the most dangerous but in
many areas in terms of loss, existence period, distress, the
flood of 2004 has crossed the above. Though the flood of 2004
has started from the north-east part of the country at the end
of July about 43 districts have been flooded.
Generally disastrous floods are expected to appear at
an interval of 10 years based on past observation, but the
flood of 2004 has occurred just after 6 years of the flood of
1998.
2626
27. A brief picture of the flood of 2004:
1. As flow has increased at the same time in Brahmaputra,
Meghna & Padma so the last three days of July were the
most dangerous. The height of flood level in some areas
has been reported to be more than the height of a one
storied building.
2. The highly affected districts are 12 in number, they are
Sylhet, Sunamgang, Habigang, Shirajgang, Pabna,
Manicgang, Dhaka, Narayangang, Munshigang,
Brammanbaria, Kumilla, Narshingdi.
3. The amount of total loss according to the Government is
42,000 crores of taka.
4. The amount of total loss according to the United Nation
(UN) is 39,500 crores of taka.
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28. o In an estimation of the Agricultural Ministry crops of about 8.3 lacs
of hectors have been damaged.
o The number affected farmers is 46.50 lacs.
o Total agricultural loss is 1,780 crores of taka.
o Total fishery loss is more than 606 crores of taka.
o About 1500 industries including 20 lacs of workers are affected.
o For the mitigation of infrastructure loss 600 crores of taka is needed.
o About 18,684 educational institutes are injured due to flood.
o The affected length of road is 41,000 Km.
o Number of affected culvert is 3500.
o In roads & highways sector the total loss is about 893 crores of taka.
o In railway sector the total loss is about 127 crores of taka.
o There occurs the scarcity of pure drinking water & according to the
Government about 1 lac 20 thousand people have been affected by
diarrhea.
o There occurs the increment of Typhoid, Dysentery, Pneumonia,
Dangue, other skin & water related diseases.
o Number of death due to flood is 638 according to Government..
2828
31. Why the flood of 2004 was theWhy the flood of 2004 was the
most dangerous??most dangerous??
The Kushiyara, Meghna, Surma, Balu and Lakhya
flowed above their respective danger levels at several
points for a duration varying from 1 to 27 days
The water levels at the Padma at Bhagykul and the
Betna at Kalaroa also flowed above the danger level.
The major rivers especially the Jamuna, Ganges and
Old Brahmaputra flowed just below the danger level
at several points during that period.
3131
32. Flood: Some positive effectsFlood: Some positive effects
It is well known that flood is the part of natural
cycle and it has got both positive and negative
impact on the environment. The negative
impact of flood is very much understandable
to all but the positive impact is still relatively
unfamiliar.
3232
33. 1) Revives ground water:1) Revives ground water:
Many countries like Bangladesh depend on
ground water and underground aquifers for
fresh water. Floodwater is absorbed into the
ground and infiltrates down through the rock
to recharge these underground aquifers that
supply natural springs, wells, rivers and lakes
with fresh water.
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34. 2) Renews the wetlands:2) Renews the wetlands:
Flood balances the health of ecology of the
wetlands. Healthy wetlands promote healthy
water supplies and improve the surrounding air
quality. Flood contributes fresh water and
waste to the wetlands that carry and deposit
nutrient-rich sediments that support both plant
and animal life of the wetlands.
3434
35. 3) Returns nutrients to soil:3) Returns nutrients to soil:
Flood distributes and deposits river sediments
over large areas of land. These river sediments
replenish nutrients in topsoil and make
agricultural lands more fertile. The populations
of many ancient civilizations concentrated
along the floodplains of rivers such as the
Nile, the Tigris and the Yellow because
periodic flooding resulted in fertile, productive
farmlands.
3535
36. 4) Recovers natural fish stock:4) Recovers natural fish stock:
Flood provides fresh water, nutrients and
larva, removes waste from to the wetlands. As
a result the wetlands get chance to renew its
environment. It helps to recover the natural
fish stock and increase the population of
fishes. Flood also adds nutrients to lakes and
streams that help support healthy fisheries.
3636
37. 5) Works on anoxia and hypoxia5) Works on anoxia and hypoxia
of wetlands:of wetlands:
A variety of physical, chemical and biological
changes occur in floodwater. Because of high
currents, waste accumulation minimized by
hydrodynamic spreading and water movement
also helps to replenish anoxic (absence of
oxygen) or hypoxia (low level of oxygen)
water with oxygen-rich water from enormous
flooding and upgrade the environment.
3737
38. 6) Prevents erosion and6) Prevents erosion and
maintains land mass elevation:maintains land mass elevation:
Soil deposited by floodwaters prevents erosion
and helps maintain the elevation of landmasses
above sea level. The rapidly receding land of
the Mississippi River delta is a direct result of
man-made flood controls and levees that
prevent topsoil-replenishing sediments from
being deposited in the delta.
3838
39. 7) Other effects:7) Other effects:
Flood brings fresh water for irrigation and
domestic use, increases fishery resources,
improves navigation of transport, kills insect,
washes out acid water, pushes salt water
toward the sea, etc.
3939
41. Several causes of flood in Sylhet:Several causes of flood in Sylhet:
1) Major portion of flood water comes from
India (about 92%), so if the upstream rainfall in
high serious damage may occur.
2) Sedimentation, bank erosion in rivers raises
the normal water levels.
3) Unauthorized construction upon river &
river banks, same case for drains & canals.
4) Deforestation in river beds.
5) Extraction of stones from hills.
6) Lacking of flood forecasting
4141
42. Definition of flash flood
A flood, which is caused by heavy or excessive rainfall in a
short period of time over a relatively small area, is referred as
flash flood. In flash flood, water level rises and falls quite
rapidly with little or no advance warning.
Typically, flash floods occurs in areas where the upstream
basin topography is relatively steep and the concentration time
of the basin is relatively short.
In Bangladesh flash floods generally occurs in the north-east,
south-east and Chittagong region. But devastating and
extended flash flood is a recurrent phenomenon for the north-
east region of Bangladesh.
In the haor area, flash flood comes from the very steep uplands
adjacent to the region in Asam and Meghalaya hills range in
India causing immense damage to the standing boro crops,
lives and properties every year. 4242
43. Characteristics of flash flood in north–east region of BangladeshCharacteristics of flash flood in north–east region of Bangladesh
This floodwater not only carries the water but also carry a huge
amount of sediment originated mainly from hill. Over the time this
sediment has deposited on the rivers and canals bed and has reduced
the conveyance capacity more or less all of the water resources
system with in the Haor area.
As a result, when flash flood due to sudden heavy rainfall creates
pressure on the water resources system, water easily overtopped and
creates breaching at several locations on the submersible
embankment eventually water quickly enter into the haor.
Most of the cases, flood water comes into the haor very early in the
monsoon and farmers are not get sufficient time to harvest their
standing boro crop.
4343
44. In North-east region of Bangladesh, normally first flash flood came
between middle of April to end of April.
Over the years, sediment has deposited mainly on the river bed and
depressed portion of the haor. In some places about 4 to 5 m
sediment has deposited on the river bed, which not only created
obstruction for water flow but also hampered the navigation system
in the north east region. Internal khals and canals have lost their
carrying capacity due deposition of sediment on the bed and in some
cases created drainage problem for the haor area.
Sand carpeting is another problem induced from flash flood. This
problem is normally found in haor very adjacent to the hill such as
Matian haor, Angurali Haor.Karchar haor and Kalner haor under
Sunamganj district.
4444
45. ASSESMENT OF DAMAGE OF BWDB’s INFRASTRUCTUREASSESMENT OF DAMAGE OF BWDB’s INFRASTRUCTURE
(ZONE-WISE, Due to flood of 2004)(ZONE-WISE, Due to flood of 2004)
LOCATION:PS
& DISTRICT
EMBANKMENT
(KM)
WCS (NOS) PROTECTIVE WORKS
(KM)
OTHERS
(NOS)
TOTAL
REHABILITATION
(IN LAKH TK)
Full Part Tk Full Part Tk Full Part Tk Items Tk
PS-Zakigahl, 2.808 60.59 548.0 --- 1 45.0 0.615 1.328 767.0 --- --- 1358.0
PS-Sadar --- 7.5 50.0 --- 1 2.0 0.2 0.5 260.0 Plinth rising of
SDE’s office &
residential
building- 2 Nos
10.0 322.0
PS-Golapganj 0.600 5.1 25.0 --- --- --- --- 0.225 110.0 --- --- 135.0
PS-Beanibazar 2.116 27.59 239.4 --- --- --- --- --- --- --- 239.40
PS-Companiganj --- 15.0 38.0 --- --- --- 0.2 0.04 60.0 --- --- 98.0
PS-Goyainghat 0.324 0.3 3.80 --- --- --- 0.533 0.48 210.0 1 No. X-bundh
(full)
90.0 303.80
PS-Kanaighat 2.060 14.15 174.0 --- --- --- --- --- --- 1.196 km
(Embankment
protection)
575.0 749.0
PS-Balaganj 0.600 15.7 100.0 --- --- --- --- --- --- --- --- 100.0
PS-Bishwanath --- 3.6 12.0 --- --- --- --- --- --- --- --- 12.0
PS-Jointapur --- 5.00 20.0 --- 2 1.5 --- 0.30 20.0 --- --- 451.50
TOTAL 8.508 154.531 1208.2 0.0 4 48.5 1.548 2.873 1427.0 --- 675.
3358.70
4545
49. AssignmentAssignment
Discuss on any public health related
issue in disaster. Discuss based on your
personal and professional context.
• Maximum number of participants = 02/ AssignmentMaximum number of participants = 02/ Assignment
Presentation and Submission of soft copy or a hard copyPresentation and Submission of soft copy or a hard copy
should be made to the course teacher before the finalshould be made to the course teacher before the final
term.term.
