6 raquibul amin pedrr workshop session 2
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•
• Issues Options and Strategies for Flood Management : • Shifts in approaches for flood Management in
Bangladesh
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INTERNATIONAL UNION FOR CONSERVATION OF NATURE
Raquibul Amin
Regional Coordinator
Ecosystem Management
IUCN Asia
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• Extent area that
goes under water during a
major flood event
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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?
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• 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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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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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,
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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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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.
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• Total “flood control” is neither possible nor desirable.
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Types of Flood
Flash Flood
Monsoon Flood
Drainage Congestion
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Tidal Flood
• Each type of flood demands different approach for its management
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Damages due to Flood
• In rural areas:
– timing
– extent
– duration
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– duration
• In urban areas:
– duration
– depth
• Flood in urban areas and flood in rural areas has to be studied separately.
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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
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• 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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Structural Options
• Reservoir or Detention basin for impounding excess
runoff.
• Retarding basins to lower the level of flooding
downstream.
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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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What is a Non-structural measure?
• A measure to reduce loss or damage by administrative measures.
• It does not control the process of inundation.
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• It may not foster any economic growth.
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Non-structural measures
• Flood forecasting and warning
• Flood fighting
• Flood proofing
• Evacuation and shelter management
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• Evacuation and shelter management
• Flood insurance
• Floodplain zoning
• Changes in cropping pattern
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Why embankments/polders are selected as
the key option!
• Cheap to construct
• Easy to build
• Easy to maintain
• Acts as road
• May create drainage congestion
• Obstructs silt movement
• Obstructs fish movement
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• Acts as road
• Labor intensive
• Simple to design
• Obstructs movement of boats.
• Increases floodplain occupancy
• Rise in river bed level
• Rise in water level elsewhere
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Flood Forecasting and Warning
• Lead time – for urban areas---short term forecast.
– for rural areas to support agricultural practices ------- long term
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forecast required.
• Dissemination – Language.
– awareness raising.
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Planning for Flood Management
• As a disaster management measure– non-structural measures.
� Pre-disaster preparations
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� during disaster measure
� post disaster recovery
• As a part of development projects� structural measures.
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Climate change and floods !!
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Flood Inundation Depth Map Existing Condition
No Sea Level Rise Upstream flow: Average Year (Year 2000 flow)
Upstream flow: Average Year (Year 2000 flow)
Upstream flow: Average Year (Year 2000 flow)
Upstream flow: Average Year (Year 2000 flow)
Upstream flow: Average Year (Year 2000 flow)
Flood Inundation Depth Map: Projection Year 2015Sea Level Rise 10 cm
Flood Inundation Depth Map: Projection Year 2030Sea Level Rise 14 cm
Flood Inundation Depth Map: Projection Year 2050Sea Level Rise 32 cm
Flood Inundation Depth Map: Projection Year 2100Sea Level Rise 88 cm
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Land Level (m PWD)
Inundation Depth (m)
7.00-19.004.00- 7.002.00- 4.000.00- 2.00
0.00- 0.15
0.15- 0.30
0.30- 0.60
0.60- 0.900.90- 1.801.80- 3.60
Above 3.60
Land Level (m PWD)
Inundation Depth (m)
7.00-19.004.00- 7.002.00- 4.000.00- 2.00
0.00- 0.15
0.15- 0.30
0.30- 0.60
0.60- 0.900.90- 1.801.80- 3.60
Above 3.60
Land Level (m PWD)
Inundation Depth (m)
7.00-19.004.00- 7.002.00- 4.000.00- 2.00
0.00- 0.15
0.15- 0.30
0.30- 0.60
0.60- 0.900.90- 1.801.80- 3.60
Above 3.60
Land Level (m) PWD)
Inundation Depth (m)
7.00-19.004.00- 7.002.00- 4.000.00- 2.00
0.00- 0.15
0.15- 0.300.30- 0.60
0.60- 0.900.90- 1.801.80- 3.60
Above 3.60
Land Level (m PWD)
Inundation Depth (m)
7.00-19.004.00- 7.002.00- 4.000.00- 2.00
0.00- 0.15
0.15- 0.30
0.30- 0.60
0.60- 0.900.90- 1.801.80- 3.60
Above 3.60
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Warning Dissemination
��������Meghalaya, India
����
�
��
��Volunteer DISSEMINATION
IMD Website
GENERATION
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��
�
� �UDMC
��CNRS
Sunamganj
CNRSTahirpur
↸UNO,
PIO
↸DC, DRRO
FILTRATION
�CNRSDhaka
�DMIC
↸BWDB, FFWC
Internet connectivity
��CNRS
Sunamganj
CNRSTahirpur
↸UNO,
PIO
↸DC, DRRO
FILTRATION
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There is possibility of a low flash flood (WL 4 -5
meter) during the next 4 days. Water level may
increase by one hand.
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.
Green Flag
Yellow Flag
Early Warning Flag
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Yellow Flag
Red 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
possibility of crop damage).
There is no possibility of a flash flood during the
next 4 days. No Flag
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Flood Severity Pillar
9
8
7
6
2004
2001
Severe Flood
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5
4
3
2
1
2001
1976
1985
Moderate Flood
Low Flood
Flood Severity WL (meter) WL (haat) Flood History
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Encourage shifting to crops other than rice as a
coping measure to flash floods
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Summing up
• Floods may be due to natural as well as anthropogenic factors.
• Solution for any flood problem has to based on proper
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• 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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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
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without the non-structural measures the structural option will not
achieve sustainability.
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Thank You
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