1. •
• Issues Options and Strategies for Flood Management :
• Shifts in approaches for flood Management in
Bangladesh
Raquibul Amin
Regional Coordinator
Ecosystem Management
IUCN Asia
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4. • Extent area that
goes under water during a
major flood event
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5. Flooding: disaster or fact of life ?
• Bangladesh and floods are synonymous; storm surges and
cyclones are not new phenomena.
• Is flood a fact of life and we should “live with flood”?
• Does it mean --do nothing? And where flood management
infrastructures have been built--- pull them down?
• Is flood a “natural disaster” and it should be brought under
“control”? Are all floods natural phenomena? Are flood events on
the rise?
• There is a debate in the country regarding approaches to be
adopted for “flood management”. Should we go for “structural
measures” or we adopt “non-structural measures”.
• Is a combination of the two approaches desirable?
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9. June 22, 2004, Highest Water Level in Sunamganj :
Houses are still above water
June 22, 2004, Highest Water Level in Sunamganj :
Houses are still above water
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12. Definition of Flood
• What is flood?
– An area goes under and remains under water for
some times, it is inundation.
– When inundation causes damage to property and
crops, disrupts communication and brings harmful
effects to human beings as well as to flora and fauna,
we call it flood.
– Inundation supports fish, navigation, soil
fertility,ecosystems, ground water recharge.
• Inundation + damage = flood
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13. What is flood management?
• Flood management measures are aimed at reduction of damage and
harmful effects , and creation of an environment for enhanced
economic activity.
• Total “flood control” is neither possible nor desirable.
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14. Types of Flood
Flash Flood
Monsoon Flood
Drainage Congestion
Tidal Flood
• Each type of flood demands different approach for its management
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15. Damages due to Flood
• In rural areas:
– timing
– extent
– duration
• In urban areas:
– duration
– depth
• Flood in urban areas and flood in rural areas has to be studied
separately.
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16. What is a Structural Measure?
• A measure to control the physical process of flooding.
• It also prevents inundation.
• Protects vulnerable area up to certain level of flooding.
• Creates a better condition for increasing productivity from
land.
• Do we understand the correct implications the term
• “return period”? Risk is always there even immediately
after a major flood event.
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17. Structural Options
• Reservoir or Detention basin for impounding excess
runoff.
• Retarding basins to lower the level of flooding
downstream.
• Embankment, Dykes, Polders, Levees, Bund, or
flood wall.
• Improvement of conveyance capacity by dredging.
• flood-way, flood diversion through flood bye pass.
• Watershed management and afforestation.
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18. What is a Non-structural measure?
• A measure to reduce loss or damage by administrative measures.
• It does not control the process of inundation.
• It may not foster any economic growth.
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19. Non-structural measures
• Flood forecasting and warning
• Flood fighting
• Flood proofing
• Evacuation and shelter management
• Flood insurance
• Floodplain zoning
• Changes in cropping pattern
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20. Why embankments/polders are selected as
the key option!
• Cheap to construct • May create drainage congestion
• Easy to build • Obstructs silt movement
• Easy to maintain • Obstructs fish movement
• Acts as road • Obstructs movement of boats.
• Labor intensive • Increases floodplain occupancy
• Simple to design • Rise in river bed level
• Rise in water level elsewhere
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21. Flood Forecasting and Warning
• Lead time
– for urban areas---short term forecast.
– for rural areas to support agricultural practices ------- long term
forecast required.
• Dissemination
– Language.
– awareness raising.
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22. Planning for Flood Management
• As a disaster management measure
– non-structural measures.
Pre-disaster preparations
during disaster measure
post disaster recovery
• As a part of development projects
structural measures.
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23. Climate change and floods !!
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24. Flood Inundation Depth Map: Projection Year 2015
Flood Inundation Depth Map: Projection Year 2030
Flood Inundation Depth Map: Projection Year 2050
Flood Inundation Depth Map: Projection Year 2100
Flood InundationLevelRise 10Existing Condition
Sea Level RiseMapcm
Sea Depth 32 cm
Sea Level Rise 14 cm
Sea Level Rise 88cm
No Sea Level
Upstream flow:
Upstream flow:
Upstream flow:
Rise
Average Year
Average Year
Average Year
Upstream flow:
(Year 2000 flow)
(Year 2000 flow)
(Year 2000 flow)
Average Year
(Year 2000 flow)
Land Level (m PWD)
Land Level (m PWD)
(m) PWD)
Land Level (m PWD)
7.00-19.00
7.00-19.00
7.00-19.00
7.00-19.00
4.00- 7.00
4.00- 7.00
4.00- 7.00
4.00- 7.00
2.00- 4.00
2.00- 4.00
2.00- 4.00
2.00- 4.00
0.00- 2.00
0.00- 2.00
0.00- 2.00
0.00- 2.00
Inundation Depth (m)
Inundation Depth (m)
Inundation Depth (m)
0.00- 0.15
0.00- 0.15
0.00- 0.15
0.00- 0.15
0.15- 0.30
0.15- 0.30
0.15- 0.30
0.15- 0.30
0.30- 0.60
0.30- 0.60
0.30- 0.60
0.30- 0.60
0.60- 0.90
0.60- 0.90
0.60- 0.90
0.60- 0.90
0.90- 1.80
0.90- 1.80
0.90- 1.80
0.90- 1.80
1.80- 3.60
1.80- 3.60
1.80- 3.60
1.80- 3.60
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Above3.60
Above 3.60
Above 3.60
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26. Warning Dissemination
Meghalaya, India
Volunteer DISSEMINATION GENERATION
IMD Website
↸
Internet
connectivity
UDMC
↸ FILTRATION BWDB, FFWC
CNRS
UNO, Tahirpur DMIC
↸
PIO
CNRS CNRS
DC, DRRO Sunamganj
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27. Early Warning Flag
There is possibility of a low flash flood (WL 4 -5
meter) during the next 4 days. Water level may
increase by one hand.
Green Flag
There is possibility of a moderate flash flood (WL 5
– 6 meter) during the next 4 days. Water level may
increase by 2 -3 hands.
Yellow Flag
There is strong possibility of a severe flash flood
(WL above 6 meter) within the next 4 days. Water
level may increase by more than 3 hands (strong
Red Flag possibility of crop damage).
There is no possibility of a flash flood during the
No Flag
next 4 days.
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28. Flood Severity Pillar
9 2004
8 Severe Flood
7
6
2001
5 Moderate Flood
1976
4
3
2 1985 Low Flood
1
Flood Severity WL (meter) WL (haat) Flood History
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29. Encourage shifting to crops other than rice as a
coping measure to flash floods
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30. Summing up
• Floods may be due to natural as well as anthropogenic factors.
• Solution for any flood problem has to based on proper
understanding of the factors causing the flood and contributing to
damages, limitations of application of each of the options
available, and effective management practices.
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31. Summing up (contd….)
• A combination of structural and non-structural measures may be
the approach for the future; without any bias for any one of them.
• Without structural interventions, growth may not be possible; but
without the non-structural measures the structural option will not
achieve sustainability.
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