Uncertainty analysis of risk-based flood safety standards in the Netherlands through a scenario-based approach

ABSTRACT

Flood risk quantification is a complex process involving a chain of models. The approach contains many uncertainties which accumulate in the calculated flood risk. Risk-based flood safety standards are therefore prone to large uncertainty. This study aims to quantify the uncertainty of risk-based flood safety standards for a Dutch riverine case study. Through a systematic approach using expert elicitation, the key uncertainty sources in the Dutch safety standard derivation are identified. Uncertainty magnitudes are quantified for five main sources of uncertainty, after which these uncertainties are propagated through the model chain in a scenario analysis to derive flood safety standards. The results show that the Dutch risk-based flood safety standards are highly uncertain given the relative uncertainty bandwidth of 70%. The flood safety standards are found to be most sensitive to damage function and evacuation uncertainty. Also, we show that the impact of uncertainty strongly depends on local characteristics.

KEYWORDS:

• Flood protection
• coupled models
• uncertainty analysis
• scenario analysis
• economic risk
• individual risk

Acknowledgements

We would like to express our gratitude to the 6 experts in the field of flood risk & the Dutch flood safety standards for their willingness to cooperate in the expert elicitation carried out in this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data and software

The data that support the findings of this study are available from the corresponding author (S.G. Westerhof) upon reasonable request. Within this study, three main software packages have been used to perform flood risk calculations and derive flood safety standards, following the Dutch flood safety standard derivation method:

• Delft-FLS Version 2.55: Delft-FLS is a 2D hydrodynamic simulation package used for flood simulations in this study. It was developed by WL Delft-Hydraulics and was released in 2001. The program requires Windows XP or earlier versions of Windows as operating system.

• HIS-SSM Version 2.5: HIS-SSM is a Dutch software package used for quantification of flood consequences, based upon flood characteristics in ASCII files (such as from Delft-FLS) and damage functions. The program was developed by Geodan IT and HKV. Version 2.5 becames available in 2007. It requires Windows 95 or a more recent windows version as operating system.

• Esri Arc-GIS Desktop, Arc-Map version 10.5: Esri Arc-GIS is a software program used for viewing and editing spatial data, used in this study for the calculation of flood risks to people based on flood characteristics from Delft-FLS. Arc-GIS Desktop was developed by Esri and version 10.5 became available in 2018. It requires Windows 7 or more recent Windows operating systems.