1Flood Defence Toronto, May 6-8, 2008

Risk assessment in trans-boundary cooperation between the

Netherlands and Germany

Jan Stijnen

Toronto, May 6-8, 2008Flood Defence 2

Presentation overview

• Introduction

• Study area

• Risk-assessment method

• Sensitivity analysis

• Summary and future plans

Toronto, May 6-8, 2008Flood Defence 3

Introduction

• Flood protection in boundary area of Germany and

the Netherlands

• Identify and reduce flood risk for 2 dike ring areas

along the Rhine

• Cooperation!

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Introduction

• Project initiation: 2005

• Three phases

1. Communication and identification (2006)

2. Risk-analysis of right-hand side dike ring (2007)

3. Risk-analysis of left-hand side dike ring (2008)

• Joint method, based on existing software/techniques

• Time horizons: 2006, 2015 and 2015+

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Study area

Transboundary

dike rings along the

river Rhine

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Study area

Dike ring 48

Dike ring 42

12.5 miles

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Scope of the project

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Failure mechanisms

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Computation of failure probabilities

– Overflow

– Wave overtopping

– Bursting of the soil & piping

– Stability of the slope

– No structures

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Failure mechanisms / probabilities

• Identification of 10 weak spots, based on Dutch

deterministic assessment method and local expert

knowledge

• Probabilistic computation of failure probabilities every

100 meters for wave overtopping only

• Detailed probabilistic computation of failure

probabilities for 10 weak spots

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Differences in dike design

T = 1250 years

T = 500 years

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Difference in maintenance

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Breach and flood simulation

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Breach and flood simulation

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Damage assessment

Flood simulationDamage and

loss of life moduleDamage function for agriculture and recreation

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

Flood depth [m]

Dam

age

fact

or

Land use

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Flood risk

Risk=

probability

consequence

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Cost-benefit analysis of measures

Types of (structural) measures:

– Dike strengthening

– Compartment dikes

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Compartment dike

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Compartment dike

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Sensitivity analysis

Verification of sensitivity to assumptions

– Critical overtopping discharge

– Breach development (width, water level, moment

of breach)

– Flood wave (shape and height of discharge wave)

– Correction of damage and costs

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Summary and future plans

• Cooperation very successfull as a result of the

communication and identification phase

• Much added value because of different partners

• Project in last phase

• Final results this summer (symposium)

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Thank you for your attention!