Risk and uncertainty in flood management

This lecture provides an overview of uncertainty and risk assessments applied to flood management. First of all some concepts are introduced with a model of risk based upon the identification of sources, pathways and receptors and the components as the hazard, the exposure and vulnerability. Methods for assessing and managing risk are discussed ranging from broadscale qualitative assessment to the detailed methods. The public tolerance and acceptance of risk depends upon several factors and an example is given of the so-called "F-N curve". Uncertainty is an important component of risk assessment when decisions must be made. The discussion of uncertainty draws a distinction between natural variability which cannot be controlled and knowledge uncertainty which may be reduced through improved knowledge and understanding. The issues are illustrated through case studies in the flood defence sector. Much of the language of risk assessment needs careful definition and the chapter contains a glossary prepared by HR Wallingford for Risk and Uncertainty in the flood defence sector. The material draws heavily upon research undertaken at HR Wallingford for the UK Environment Agency, the Department for Environment, Food and Rural Affairs (DEFRA) and the former Ministry of Agriculture, Fisheries and Food (MAFF). Much of the text for this Chapter has been compiled from other documents, specifically the report by HR Wallingford (2002) and the paper by Burgess et al. (2000).