FLOOD RISK MANAGEMENT

IIHR Seminar (December 3 2010)KYUTAE LEE

Flood Risk Management1. The need for assessing Flood Risk?2. Risk analysis/assessment – general overview3. Issues in current practice of Flood Risk Management4. Role of uncertainties in flood risk management5. Example: Multicriteria Risk Mapping Approach (MCA)

1. The need for assessing Flood Risk?Providing information for rational decision making to

PeopleInformation on individual flood riskraising awareness & preparedness

Insurance industry calculation of probable maximum loss (PML)

calculation of insurance rates

Government investments in flood protection:

- Financial needs for protection measures- Evaluation and selection flood protection measures

2. Risk analysis/assessment – general overview

Past / today: Safety-Standard ApproachMainly structural measures (e.g., levees, dikes)Provides same safety level for all inundated area

(neglecting the different damage potential, hence inefficient allocation of resources)

Emerging: Risk management ApproachConsideration of the whole spectrum of risk reduction

measuresEfficient allocation of funds based on a cost-benefit analysis

(by using multi criteria, estimating the damage function)

Approaches

Framework

(Modified from Schanze (2006))

Framework

(Plate (2002))

Damage evaluation

Damage evaluation – necessary information (Adapted from Meyer, 2007))

1. Risk Analysis2. Hazard Determination3. Inundation maps by hydrological and hydraulic model

1. Risk Assessment2. Vulnerability

Determination3. Flood Damage model

Flood Risk maps

Evaluation of Annual Average Damage

3.Current Issues in flood risk management

1. Uncertainty estimationFlood risk assessment is always to some degree uncertain, but these uncertainties in the results should be documented in order to provide decision makers with information on the quality of the data they are using as a decision support. 2. Evaluation of the Social & Environmental Risks- Social & Environmental Risks are often neglected since they are not (easily) measurable in monetary terms.- Focusing on only economic damages makes often the results of Flood Risk Assessment incomplete, biased. 3. Spatial distribution of RisksThe spatial distribution of risks is rarely considered. E.g. One area might be more vulnerable than other areas for 100 yr flood.

4. Uncertainties in Flood Risk Management

Uncertainties in Risk ManagementUpper bounds representing Maximum expected AAD

Lower bounds representing Minimum expected AAD

5. Example (Floodsite-Project)Multicriteria Risk Mapping Approach (MCA) Incorporates all relevant types of risks (Social, Economic & Environmental) without measuring them on a monetary scale.1. Economic

Annual Average Damage

2. EnvironmentalErosion potential (of material)Accumulation potential (of material)Inundation of oligotrophic biotopes

3. SocialAnnual average affected populationProbability of social hot spots (hospitals, schools etc.) of being

affected

5. Example (Floodsite-Project)Multicriteria Risk Mapping Approach (MCA) (Cont.)

Question?