1WMO: Climate and Water Department www.apfm.info

WMO

Training Workshop on Integrated Flood Management for the Nile Basin Countries

Effects and limits of traditional flood management options in light of future challenges

23-27 November 2009-09-16 Nairobi, Kenya

Armin Petrascheckformer member of

Federal Office for Environment

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Content1. Changing world and changing

society2. Problems and objectives of

traditional flood management3. Possibilities of intervention4. Discussion of structural measures5. Summary

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Traditional Flood ManagementTradition is something positive, since it is related to old values and

has often proofed effective during centuries.

Modern techniques are not necessarily positive just because they are recently developed

Its not the question if a method is modern or old

it is the question if the method is adequate or inadequate to solve the problem

Problems are changing

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We are living in a changing world

Change of temperature in Switzerland (observed)

Climate changes and with the climate the floods

Very high damage

High damage

Important floods in Switzerland

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Changing climate is one problem, but more important are demographic and social changes

Population of Egypt

3 619

3750

73

0

20

40

60

80

1750 1800 1850 1900 1950 2000 2050M

io. o

f inh

abita

nts

The resources remain the same, but demand increases

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Changes in social structures Urbanization

• Mega-cities and urban aglomerations– Economic growth driver’s– Loss driver’s– Vulnerability hotspots

• Root causes of Urbanization are not adressed through flood management

• Disparity of investment between Urban Development & flood management infrastructure in the entire catchment

• Sustainability of urban growth

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What is the result of the traditional flood management in a changing world

Dramatically increasing damages

We need a change

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Main aspect of traditional flood management is flood control by structural measures

Objectives:• Flood control: is a myth - possible only for a limited

range of floods• impend flooding: separates flood plain and river

neglects needs of the river (nature)• minimize damages: possible for existing land use

future development must be controlled by other means

These are reactive objectives

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The objective is not to avoid losses

You can loose only if you have.

The driving force of human activity is to generate benefits.

Everybody must earn enough to survive today, before he cares about tomorrow

Tolerable losses are a constraint but not a goal .Thus flood management must be embedded in the overall

economy (IFM)

Examples:• Rio Paraguay

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Jan T.L. Yap

–Ad-hoc and stand alone

–Reactive rather than proactive– Wrongly defined objective–Emphasis on structural measures thus shortfall of environmental aspects

–Monodisciplinary

–Lessons from past failure not learnt

Problems of traditional flood control

Traditional flood control is a part of integrated flood management (IFM) but insufficient for planning the future

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Mountainous areaRunoff controlSediment control

River corridorRegulating flowRetaining waterFlashing flowFloodplain

Retaining waterDiverting water

Traditional flood management measuresWhatever strategy is selected one has to understand the floods and the

damages

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Chain of effects

Damageg

Risk of damage

Emergencyplanning

Vulnerability

Risk of inundation

Hydrologic hazard

Meteorology

Catchmentarea

Riverbed

Damage is not directly dependent from rainfall. Several conditions mustbe fulfilled, before damage occurs.

Generation of flood damages

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Influencing damage

Damage

gRisk of damage

Emergencyplanning

Vulnerability

Risk of inundation

Hydrologic hazard

Meteorology

Catchmentarea

Riverbed

Retention in the areaForestation, Retention basins, Increase of infiltration,...

Structural protection measuresIncrease of river bed capacity, Dikes, Sills, Bank protection, ….

Appropriate land useRetention areas, Protection of single structures,….

Emergencymeasures Forecast, Rescue, Temporary measures

Flood protection measuresFlood plain management

Definition of intervention possibilities

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Dam

Additional aspects-Multi purpose utility

Issues-Deterioration of environment-Longitudinal disconnection -Capturing sediment-Possibility of dam failure-Confined geographic area-Unpopularity-Complexity of land acquisition -Social issues of resettlement

Functions-Attenuating flood peak-Generating hydro power-Regulating flow-Storing water

H

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Retention Pond

Additional aspects-Diverting flood damage torural / agricultural area-Efficient use of limited plain-Artificial wetlands (habitatand recreation)

Issues-Compensation for inundation-Uncertainty of efficiency

Functions-Attenuating flood peak duringflood events

H

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Embankment

Additional aspects-Can be combined with transport infrastructure or civil Defence infrastructure (shelters)

Issues-Lateral disconnection (water,sediment, aquatic species…)-Increase of flood damagepotential- »Design for failure »-Maintenance intensive

Functions-Blocking inflow to floodplain

E

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Functions-Reducing bank erosion-Sediment control-Flow concentration (navigation)

Groyne

Issues-In case unpopular due to aesthetic aspects

E

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Watergate

Functions-Preventing backwater frommain stream to tributary

Issues-Increase risk of inundationon the tributary

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High Standard Levee

Functions-Decrease of possibility offailure-multipurpose land use

Issues-Difficulty in securing space for levee (negotiation, cost)

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Diversion channel

Sea

Issues-High cost due to creatingnew channel (land acquisition)-Technical difficulty-Impact on environment-Full controll structure required on inflow to manage environmental flows/low flows

Function-Diverting river flow from main stream(reducing risk in urban area)

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Underground channel

Additional aspects-Less issues of land acquisition-possibility of multipurpose use

Issues-High cost -Technology requirements

Functions-Storing water-Diverting water

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Channelization

Issues-Deterioration of environment-Increase flow velocity (increase riskto downstream)

Functions-Regulating water flow-Reducing space requirements of natural water course

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Functions-Increase/maintainconveyance capacity

Channel maintenance

Issues-Deterioration of environment inriverbed-Natural recovery of sedimentcontinued maintenance Requirements-Effectiveness depends on theshape of the flood hydrograph-Sediment disposal/polution

H

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Sabo dam

Issues- Longitudinal disconnection-Deterioration of landscape-Maintenance and continued function

Functions-Blocking mud flow-Sediment control

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Summary• Traditional flood control tries to separate

human activity and floods instead of integrating them.

• Minimizing damages is only a partial objective.

• The driving force of human activity is to generate net benefits.

• Structural measures will remain an important tool in IFM

Discussion of IFM and its measures will follow later

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Changes leading to IFM• From defensive to pro-active approaches;• From Ad-hoc to Integrated Flood

Management (IFM);• Towards a culture of prevention by

managing flood risk & living with floods;• Balancing flood risk and achieving

sustainable development needs;• Change in decision making processes to

include risk management approaches.

International Seminar on River & Development

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Where are we going?IFM should lead to a brighter future

Thank you for your attention