Developing models to estimate the benefits from flood warnings

Flood forecasting and warning systems have a significant role to play within integrated flood risk management, either in combination with mobile structural flood defences or as part of an approach which combines a number of non-structural measures. In theory the benefits of flood warnings, in terms of community security, protection of life and flood damage reduction, should be large. The theoretical benefit potential is being driven upwards by important advances in the predictive sciences, and in the application of information and communication technologies to rapid flood warning communication. However, in practice the full benefit potential of flood warnings is rarely maximised, and currently in some circumstances it falls well below the theoretical potential. Often this happens because warning response strategies are inadequately conceptualised, developed and implemented. The objectives of Activity 2 of Task 10 were therefore to: 1. To collect new information and available data on the damage-reducing effects of flood warnings and on those factors affecting people’s propensity to act upon receipt of a warning and to refine the existing UK FHRC model of the economic benefits of warnings. 2. To calibrate a simple model developed by MU/FHRC for a range of flood circumstances so that this model can become a standard method for evaluating flood damages and the effect that warnings can have on these values. 3. To produce a modified FHRC model and data on: a) how people respond to flood warnings; b) what actions people take to protect people and property; c) what features of flood warning systems would be best to enable people to do more; d) some insights into what factors encourage, limit or inhibit the ability of households and others to respond to flood warnings; and e) some estimates of the actual damages saved according to key variables (e.g. type of warning and warning lead time). 4. To apply the flood loss reduction model to some FLOODsite case studies to demonstrate the viability of warnings as a major non-structural flood mitigation option. 5. To review and refine methods for collecting data on the damage reducing actions taken by households upon receipt of a warning. The research presents three approaches for estimating the benefits of flood warnings in terms of flood loss savings. The first approach, a refinement of the MU/FHRC model for use within continental Europe, focuses in detail on household flood warning response and benefit. Quantitative data are presented for the case studies in the UK, the River Elbe in the Czech Republic and the River Mulde in Germany. A second model reconceptualises flood warning response strategies within a portfolio approach, and develops a comprehensive model of flood warning response which may be applied to a wide range of flooding conditions and socio-economic circumstances. This broader approach considers eight flood response and benefit pathways and moves beyond merely considering householder-level responses by adding the savings that can be accrued through; business contingency planning; the operationalisation of flood defences; contingent flood-proofing; search and rescue, evacuation, the deployment of community-based options and through effective watercourse maintenance. The benefits of flood warning are, therefore, not only assessed for householders, but for all sectors of the economy. The model has been applied to data from a number of case studies; for a synthetic simulation of flood warning response and benefit in three urban areas; for England and Wales; and for Grimma on the River Mulde, Germany. These demonstrate the potential of the reconceptualised flood warning response strategies, and the comparative scale of monetary benefits associated with each. The factors which have been found in the research to encourage improved flood warning response, and thus warning benefits, are also presented and discussed. A third method is applied to the example of Grenoble in France. This case study presents an approach to the estimation of damage savings attributable to flood warnings when few data are available. The models, data and findings from this research are now ready to be applied throughout Europe, and are capable of significantly increasing the value of flood forecasting and warning systems. Despite progress some significant data gaps still remain and provide an agenda for future research in this area.