Since its development in early 2000 (through a combination of industry and Research Council funding) RASP (Hall et al, 2003, Meadowcroft and Sayers, 2005) has had a significant impact on the way flood risks are assessed. The underlying methods, and various associated developments (e.g. Gouldby et al, 2008), have repeatedly been used to assess flood risk in England and Wales and determine the national investment need. Other sectors, particularly the reinsurance sector have also made considerable advances in broad scale probabilistic risk analysis. The context of flood risk management has also changed in recent years; with a greater local responsibility of flood related issues. In response more bottom-up approaches (based upon more detailed local analysis) are increasingly seen as one way of assessing the accuracy of '˜top-down'™ approaches. FoRUM seeks to consolidate and compare the detail of the alternative 'top down' and 'bottom up' methods and associated uncertainties together with more empirical assessments of the credibility of associated national risk estimates. This will promote a common appreciation of the issues by both the stakeholders and research community and help address the lack of understanding that is restricting further innovation.
This Workshop provides the first stage of this process and focuses on the approaches used to assess flood risks at a national scale at present. The approaches adopted within RASP (that underlie NaFRA) and Catastrophe models (that underlie insurance industry approaches JBA, AIR) will be discussed together with the approaches to validating national scale assessments. The way source (storm loads, spatial and temporal coherence etc) and pathway (e.g. channels, flood defences, floodplains etc) terms are handled will be compared in detail. The approaches to assessing receptor impacts (both direct and indirect damages) will also be explored. Differences in data, model structure and model components will be discussed. The workshop will be an in-depth exploration of the methods used.