Believe it or not? The challenge of validating large scale probabilistic risk models

The National Flood Risk Assessment (NaFRA) for England and Wales was initially undertaken in 2002 with frequent updates since. NaFRA has become a key source of information on flood risk, informing policy and investment decisions as well as communicating risk to the public and insurers. To make well informed decisions based on these data, users rightfully demand to know the confidence they can place in them. The probability of inundation and associated damage however cannot be validated in the traditional sense, due the rare and random nature of damaging floods and the lack of a long (and widespread) stationary observational record (reflecting not only changes in climate but also the significant changes in land use and flood defence infrastructure that are likely to have occurred). To explore the validity of NaFRA this paper therefore provides a bottom-up qualitative exploration of the potential errors within the supporting methods and data. The paper concludes by underlining the need for further research to understand how to robustly validate probabilistic risk models.

[1]  Keith Beven,et al.  The uncertainty cascade in model fusion , 2014 .

[2]  T. Kjeldsen.  How reliable are design flood estimates in the UK? , 2015 .

[3]  Paul Sayers,et al.  Representing fragility of flood and coastal defences: Getting into the detail , 2008 .

[4]  Paul Sayers,et al.  RASP - A hierarchy of risk-based methods and their application , 2005 .

[5]  Paul Sayers,et al.  Strategic flood management: ten ‘golden rules’ to guide a sound approach , 2015 .

[6]  James J. Porter,et al.  Flood-Risk Management, Mapping, and Planning: The Institutional Politics of Decision Support in England , 2012 .

[7]  Jim W. Hall,et al.  Robust decision-making under uncertainty – towards adaptive and resilient flood risk management infrastructure , 2012 .

[8]  Kevin Horsburgh,et al.  Quantifying the Uncertainty in Future Coastal Flood Risk Estimates for the U.K , 2011 .

[9]  K. Njau,et al.  Performance of horizontal subsurface flow constructed wetland in the removal of tanninsA paper submitted to the Journal of Environmental Engineering and Science. , 2010 .

[10]  B. Gouldby,et al.  Recent development and application of a rapid flood spreading method , 2008 .

[11]  Jim W. Hall,et al.  Editorial: steps towards global flood risk modelling , 2014 .

[12]  Rob Lamb,et al.  A new method to assess the risk of local and widespread flooding on rivers and coasts , 2010 .

[13]  Edmund C. Penning-Rowsell,et al.  A realistic assessment of fluvial and coastal flood risk in England and Wales , 2015 .

[14]  Bruno Merz,et al.  Development of dike fragility curves for piping and micro-instability breach mechanisms , 2009 .

[15]  Jim W. Hall,et al.  A framework for uncertainty analysis in flood risk management decisions , 2008 .

[16]  Ben Gouldby,et al.  Integrating a multivariate extreme value method within a system flood risk analysis model , 2015 .

[17]  Jim W. Hall,et al.  Towards risk-based flood hazard management in the UK , 2002 .

[18]  R. Dawson,et al.  A methodology for national-scale flood risk assessment , 2003 .

[19]  Edmund C. Penning-Rowsell,et al.  The benefits of flood and coastal risk management: a manual of assessment techniques (Multi-Coloured Handbook 2005) , 2005 .