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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10


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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

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.

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

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.

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.

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.

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.

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

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

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.

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.

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)




Flood Inundation Depth Map: Projection Year 2015Sea Level Rise 10 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)


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)


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)


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)


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

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

Flood Severity Pillar

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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

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.

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.

Thank You

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6 raquibul amin pedrr workshop session 2

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