An Overview of Impact of Flood in Bangladesh and Options for Mitigation

An Overview of Impact of Flood in Bangladesh and Options for

Mitigation

An Overview of Impact of Flood in Bangladesh and Options for

Mitigation

A. N. H. Akhtar Hossain PEngHonorary Secretary General, The Institution of

Engineers, Bangladesh

& Managing Director, Dhaka WASA

A. N. H. Akhtar Hossain PEngHonorary Secretary General, The Institution of

Engineers, Bangladesh

& Managing Director, Dhaka WASA

Points to be highlighted

Causes of Flood

Impact of Flood

History of Flood Management

Mitigation Options

Flash Flood Rainfed FloodRiver FloodStorm Surge and Tidal FloodUrban floods

Types of Flood

Major Causes of Floods in BangladeshLarge volume of flow from transboundary rivers in very short period of time (June-October)

Intensive rainfall within the country

Very flat topography

Higher sea level during monsoon

Synchronization of flood peaks

Siltation of the drainage routes

Breaching and overtopping of flood protection embankments

Human intervention and encroachment of rivers and floodplains

Overview of some historical flood event

1987 Floods:1987 Floods: Heavy rainfall in Northwest Region Heavy rainfall in Northwest Region

1988 Floods:1988 Floods: High floods in Brahmaputra and Ganges High floods in Brahmaputra and Ganges Basins; Flood peaks synchronisedBasins; Flood peaks synchronised

1998 Floods:1998 Floods: Four successive flood peaks in Brahmaputra; Four successive flood peaks in Brahmaputra; higher sea level. higher sea level.

2004 Floods:2004 Floods: High rainfall in northern and northeastern High rainfall in northern and northeastern catchments; high water level at Chandpurcatchments; high water level at Chandpur

More than 68% of the inundated in 1998

More than 38% of the inundated in 2004

Socio-economic Implications

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40,000

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120,000

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1998

2004

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Affected Area Crop Damage

Historical flood events – extent and crop damage

Event 

Impact

1954 floods Affected 55% of country 

1974 flood Moderately severe, over 2,000 deaths, affected 58% of country, followed by famine with over 30,000 deaths 

1984 flood Inundated 52,520 sq-km, cost estimated at US$ 378 million 

1987 floods inundated over 50,000 sq-km, estimated damage US$ 1.0 billion, 2055 deaths 

1988 floods Inundated 61% of country, estimated damage US$ 1.2 billion, more than 45 million homeless, between 2,000-6,500 deaths 

1998 floods 1,100 deaths, inundated nearly 100,000 sq-km, rendered 30 million people homeless, damaged 500,000 homes, heavy loss to infrastructure, estimated damage US$ 2.8 billion 2004 floods Inundation 38%, damage US$ 6.6 billion, deaths 700, affected people nearly 3.8 million

1972, IBRD Plan

National Water Plan 1, 1986

National Water Plan 2, 1991

Flood Action Plan, 1989-95

BWFMS, 1995

National Water Policy, 1999

National Agri. Policy, 1999

National Forest Policy, 1994

National Fisheries Policy,1998

National Env. Policy, 1992

Guidelines for Participatory

Water Management, 2000

Milestones

NWMP, 2004

1964, IECO Master Plan

1957, Krugg Mission

RELATED POLICY, PLAN AND STRATEGY

FLOOD CONTROL MEASURES

• Structural: Dam, Barrage, Regulator, Sluices, Embankment, Channel Improvement, River Training & Bank Protection Works etc.

• Non-structural: Flood Forecasting & Warning System, Flood Proofing, Crop Diversification

Completed FCD Projects – approx. 600

Non Structural MeasuresFlood Forecasting & Warning System since 1972From 1990 FFWS has been developed with Hydrodynamic modelFFWS has the capability to produce Flood Inundation Status on Daily basisFlood Forecasting and Warning System for all flood prone areas having 85 Flood Monitoring Stations of which 46 are real Flood Forecast StationsFlood Proofing has been practiced since time immemorial in the low lying areas through raising the platform for homesteadsCrop Diversification is also been practiced

Benefits from Flood Management Measures

• FFWS plays an important role in reducing losses as well as saves life and property

• Cereals Production (2001-2002)- Incremental 8.535 million MT Equivalent

to appx. US$ 1.0 billion

• Poverty Reduction:Directly - LCS, EMG, CMG

Options for Flood Mitigation

Flood preparedness

Flood Response

Post-floodRehabilitation

Stages

Flood Preparedness MeasuresFlood zoning and risk mapping: A comprehensive approach is required to develop flood zoning and risk maps for coordinated development and risk management in floodplains

Rationalization and adequate maintenance of existing FCD projects

Flood management modeling: to study any development options in the floodplains in an integrated manner based on proper scientific basis

Erosion prediction and monitoring: making use of available modeling integrated with remote sensing and GIS technology a nation-wide erosion prediction and monitoring system should be immediate instituted

Flood Preparedness Measures

Drainage Improvement: The natural drainage need to dredged and made free from encroachment to bring back the original conveyance capacity. Canal Digging program may be strengthened with proper technical guidelines and effective monitoring.

Offtake Maintenance: It is important the offtake of the rivers are regularly dredged to allow flood flow distribution in wider areas.

Integrated Floodplain Management: There should be government guidelines for any development in the floodplains which would pave the way for an Integrated Floodplain Management.

Flood Preparedness MeasuresUrban Flood Management: There is a need for immediate actions to free the natural drainage routes from encroachment, design and implement sustainable drainage management system for each of the urban areas.

Improvement of Lead-time for Flood Forecast: The lead-time of forecasts could be extended using climate forecasts. The CFAB project has paved the way-the development made through CFAB should be carried forward.

Flood Proofing and Shelters: Various flood proofing measures could be adopted deep-flooding areas. One of the options may be to build clustered habitats with all the civic amenities. This may be undertaken on a pilot basis under Asrayan Project for the poor in the Haor areas.

Flood Response Measures

Updating and further development of the Standing Order for Disaster Management

Development and implementation of an ICT based Flood Response system which should also include a nation-wide network of flood information database by connecting databases of various agencies involved in flood response activities. Such a system could be developed based on internet and wireless communication technologies;

Training and capacity building of field officials and community workers, volunteers and NGO staffs in flood fighting and relief activities.

Awareness building: It is imperative that for implementing participatory approach in flood disaster management and to make it effective, awareness about any disaster event and the role of all concerned should be clearly understood. For this purpose the government, NGOs and others concerned should undertake concerted efforts.

Flood Response Measures

Post Flood Reconstruction and Rehabilitation

Methods and tools for damage assessment: One of the constraints in responding to any disaster and mobilizing resources for reconstruction and rehabilitation is reliable data on flood damage. There are no methods or tools available in the country. Measures should be taken to develop such tools and methods

Coordination: The limited resources of the government should be properly mobilized and coordinated. For this all agencies working in the post-flood rehabilitation and reconstruction should carry out their activities in a transparent and coordinated manner. There should be central flood rehabilitation body to coordinate such activities.

General Recommendations

Regional cooperation: As more than 90% of the flood flow originate from outside the country, Bangladesh alone cannot solve the flood problem. For effective flood management basin wide approach with concerted regional participation may be pursued. A regional flood management initiative should be initiated with participation from all co-riparian countries.

The Indian River Link Project: The proposed Indian river link project would be a disaster for the society, economy and the ecology of Bangladesh. Immediate actions are required in the following areas’

• to foster dialogue with the Indian side on this issue.

• Initiative from people to build awareness

• Scientific studies to understand the impacts

Thank you for your kind attention

80% in 5 months

Average inflow

Total Basin Area 1.72 million sq km

Only 7% of basin area lies within Bangladesh

India

Annual Variation of Major River Discharge

Brahmaputra-Jamuna

Ganges-Padma

Meghna

Bay of Bengal

India

Myanmer

Ganges

Max Q 78,000 m3/ s

Min Q 200 m3/ s

Jamuna

Max Q 100,000 m3/ s

Min Q 4,000m3/ s

Lower Megna

4,000 m3/ sMin Q

180,000 m3/ sMax Q

Cherapunji (in INDIA)Worlds highest rainfall

• Annual Ave. Rainfall: 2300mm• Annual Maximum > 4500mm

(northeast Bangladesh)

46004200

2600

2200

1500

1700

1900

2100

2000

2800

2900

Topography of Bangladesh

-Land elevation of 50% of the country is within 5 m of MSL

-68% of the country is vulnerable to flood

-20-25% of the area is inundated during normal flood

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10

15

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24-Feb 15-Apr 04-Jun 24-Jul 12-Sep 01-Nov 21-Dec 09-Feb 31-Mar 20-May

Wat

er L

evel

, mP

WD

Synchronisation of Flood Peaks on Sept 10

Jamuna River at Bahadurabad

Ganges River at Hardinge Br.

Meghna River at B Bazar

1998 Floods

Monsoon

Higher sea level in monsoon

River siltationThree river systems carry about 1.8 ~2 billion tons of sediment every year. A large volume of this sediment flow is deposited within the country on river beds and flood plains.

Breach/failure of Embankments

Ichamati

Betna

Kobadak

Beel Dakatia in 1998

Satkhira in 2000

Human Interventions

Moderate floodingSevere flooding Dry

Flood zoning & Risk Mapping

Beyond Probable Flood

Suggest Flood

Proofing

Flood Proof existing

infrastructureHigh risk zone

Flood Proof existing

infrastructure

Suggest Flood

Proofing

Beyond Probable Flood

100 year flood50 year flood10 year flood

Risk Mapping & Development Guidelines

Erosion Prediction Using Morphological Models

Jamuna Brdige Site

SirajganjBhuapur

Monitoring &Measurement

Forecasting

Policy issues

Decision SupportSystems

KnowledgeInformation

Feedback

Watersystem

Management/support

Stakeholders

Kn

ow

led

ge

Info

rmat

ion

Fee

db

ack

DecisionStudiesProjects

Investment

ICT based Flood Response System

Knowledge provider

Knowledge Consumer

StakeholdersUser community

Knowledge Consumer

Knowledge provider

InteractionConsultationSharing

•An assessment of the cost if a certain phenomenon were to occur with a particular intensity

•This may be quantified to provide the cost of occurrence of a phenomenon

Probabilities of a particular event occurring at a particular time at a particular intensity

Forecaster

Dredging & Canal Diggingfor Drainage Improvement

Gorai

Ganges River

Offtake Management

B a y o f B e n g a l

Old Brahmaputra Offtake

Dhaleswari offtakeGorai offtake

- Drainage Projects

- Flood Control

- Flood Control & Drainage

- Flood Control, Drainage & Irrigation

- Irrigation & Drainage

- Irrigation Projects65% of flood prone lands now under flood management

Rationalisation of FCD/FCDI Schemes

617 projects so far completed

Before After

Flood Proofing in Haors & Low Lands

Country R/S River R/S

Normal Embankment Section

Top Width

Modified Embankment Section

Berm

Top Width

Awareness Building & Motivation

Integrated Management of Transboundary River Basins: From the Mountain top to the

Sea

Flow Augmetation

Net potential 5339 m3/s

Flood ManagementFlood ForecastingFor around 400,000 Km2

Potential 233,800 MwPresent 22,722

Hydropower

Navigation

Opening up Nepal, Bhutan and the Northeast to the sea

Fragmented DevelopmentIntegrated Water Resources Management

Private Public Partnership

Participatory Water Management

Environmental Conservation & Restoration

Water a Medium of Cooperation in GBM BasinsWater a Medium of Cooperation in GBM Basins

Climate Forecast Application in Bangladesh (CFAB)

Partners: Georgia Tech University, Univ. of Colorado, Asian Disaster Preparedness Centre, FFWC, BMD, DAE, IWM, CEGIS and

others

Develop forecasts schemes for Short (1-6 days), medium (20-30 days) and long (1-6)months time scales

Incorporate these schemes into the Bangladesh’s flood and weather/climate forecasting systems

Produce systems that are transportable in the short-term to Bangladesh institutions

CFAB presently focuses on making available the forecast products for agriculture sector which accounts for nearly 30% of

the country’s GDP

Short-range forecasts of Basin Discharge1-6 days

Short-range forecast schemes use rainfall over the Ganges and Brahmaputra catchment areas provided by ECMWF. Statistical Analysis. Provides river discharge into Bangladesh 1-6 days ahead. Schemes will increase FFWC forecast in Bangladesh to 8-10 days

Meghna Basin82,000 sq.km

Brahmaputra Basin552,000 sq.km

Ganges Basin1,087,000 sq.km

B A Y O F B E N G A LB A Y O F B E N G A L

N E P A L

BHUTAN

I N D I A

C H I N A

MYANM

AR

BANGLADESH

I N D I A

X 1

04 m3 /

sForecasting with Longer Lead-time

5-day Hindcasting For 1998

date of forecast: 04-09-2003

Observed Series 1

Lower Bound

Upper Bound

5-day Forecasting For 2003

20-day Forecasts in 2004

Bahadurabad on Jamuna R.

Hardinge Br. On Ganges R..

B a y o f B e n g a l

Ingress of salinity far inlandIngress of salinity far inland

Destruction to Sunderbans Mangrove Forest

B a y o f B e n g a l

Ingress of salinity far inlandIngress of salinity far inland

Increase of soil & groundwater salinity

B a y o f B e n g a l

Ingress of salinity far inlandIngress of salinity far inland

Salinity in Ilsha & Tentulia System will destroy

agriculture in Barisal and Patuakhali

B a y o f B e n g a l

Ingress of salinity far inlandIngress of salinity far inland

Coastal and marine eco-system will be significantly

disturbed

Water Availability 

0

10000

20000

30000

40000

50000

60000

30-Mar-01 19-May-01 08-Jul-01 27-Aug-01 16-Oct-01 05-Dec-01 24-Jan-02 15-Mar-02

Flo

w (

cu

me

c)

Base Withdrawal Scenario

Ganges dry

0

10000

20000

30000

40000

50000

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70000

30-Mar-01 19-May-01 08-Jul-01 27-Aug-01 16-Oct-01 05-Dec-01 24-Jan-02 15-Mar-02

Flo

w (

cu

me

c)

Base Withdrawal Scenario

Brahmaputra dry

Hardinge Br.

Bahadurabad

Ref. IWM Study on Indian River Link

Impact Area      Impact Parameter

Predicted Status

Supplemental Irrigation

Groundwater Recharge

Wetland Refreshing

Fisheries

Soil Nutrition

Brackish Water Zone

Bagda Shrimp Culture

Surface Water Availability                

Flood Regime                

Salinity Intrusion                

Ground-water Availability                

Sediment Transport                

Flushing of Contaminants                

Nutrients for Aquatic Life                

Impact Matrix…

  Negative

  Positive   Decrease   Increase

Impact Area      Impact Parameter

Predicted StatusSurface Water

Availability 

Flood Regime  

Salinity Intrusion  

Ground-water Availability

Sediment Transport

Flushing of Contaminants

Nutrients for Aquatic Life

Galda Shrimp culture

Agriculture

Sundarban ecology

Drinking water availability

River Bank Erosion

Offtake siltation

Flood depth-area-duration

Navigation

Surface Water Ecology

River Water Quality

Impact Matrix

  Negative

  Positive   Decrease   Increase

Dwarf Embankment in the Haor Areas