Results of the EGU Workshop "Validation in Flood Risk Modelling"

On 9 and 10 December, 2014, an expert workshop was held in Delft, The Netherlands, to discuss the often-neglected topic of flood risk model validation. This meeting was held under the auspices of the European Geosciences Union (EGU), and the Panta Rhei Working Group "Changes in Flood Risk" of the International Association of Hydrological Sciences (IAHS). Over 50 experts from 10 countries covered all the elements of flood risk analysis: (1) hazard and inundation modelling, (2) failure and reliability modelling of flood defences, (3) flood consequence modelling, and (4) the know-how to integrate hazards, failures, and consequences to compute risk.

The workshop

The workshop was organized in four sessions, covering the four elements outlined above, with a half-day allotted to each session. The sessions began with some short presentations, after which participants split into four groups of about 10 people each, to discuss in-depth the aspects of validation that were relevant for the current topic. Driving questions for these discussion groups were:

  • Why do we need validation?
  • What techniques for validation are available?
  • What is the quality of our flood risk estimates?
  • How large is the uncertainty of the risk component (hazard, failure, impact) in relation to the total accuracy?


The most important general conclusions from this workshop are:

  • Validation is a good practice in flood risk research, in order to demonstrate the predictive quality of our models, and assess whether we need further improvement
  • The development of a platform to share data for flood risk model validation (for all the four components) is highly desired.
  • Collection of data on hazard, failure and impacts after events should be promoted, standardized and become common practice.
  • Benchmarks for the set-up of hazard, failure and impact analysis should be proposed.
  • On the relative importance of the three elements: The uncertainty of hazard/hydraulic models is smaller than those in models for flood defence reliability, breach, and impacts. Still, for certain applications -such as preparing evacuation plans- accuracy of hazard/hydraulics can be critical. Many held the opinion that failure models are the weakest part, as it can have a substantial impact on the risk estimate, but is so highly uncertain.


The workshop report summarizes the main findings from the workshop, which came largely out of the fruitful discussion sessions on hazard modelling, failure modelling, flood damage assessment and integration. Finally it summarizes the main conclusions and proposed next steps of the closing session of the meeting. The full report is available for download from here.

Workshop Impressions

Jaap Kwadijk, scientific director of Deltares, opens the EGU workshop
Edmund Penning-Rowsell from Middlesex University (UK) gives a key lecture on the need of model validation
Experts are discussing validation techniques for hydrology and hydraulics
The second session focussed on failure models
The groups are rearranged after each session
On the second day, the first session focussed on damage modelling
In the fourth session experts discuss the overall impact of uncertainties in the flood risk model chain
Participants prepare the plenary discussion on way forward, wrap-up and conclusions of the workshop