Anatomy of Flood Risk
In this chapter, the notion of flood risk is interpreted and factors influencing flood risk: hazard, exposure, and vulnerability are examined. A holistic perspective on changing flood risk is provided. Economic losses from floods have greatly increased ov
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Abstract In this chapter, the notion of flood risk is interpreted and factors influencing flood risk: hazard, exposure, and vulnerability are examined. A holistic perspective on changing flood risk is provided. Economic losses from floods have greatly increased over last decades, principally driven by the growing exposure of assets at risk. It has not been found possible to attribute observed rain-generated peak streamflow trends to anthropogenic climate change, generally. Based on physical reasoning, increases in the frequency and intensity of heavy rainfall should contribute to increase in risk of precipitation-generated local flooding (e.g., flash flooding and urban flooding) in many areas. Keywords Flood risk
Hazard Exposure Vulnerability
Z.W. Kundzewicz (&) Institute for Agricultural and Forest Environment, Polish Academy of Sciences, Poznań, Poland e-mail: [email protected] Z.W. Kundzewicz Potsdam Institute for Climate Impact Research, Potsdam, Germany M. Stoffel Climatic Change and Climate Impacts, Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland e-mail: [email protected] M. Stoffel Department of Earth Sciences, University of Geneva, Geneva, Switzerland M. Stoffel Dendrolab.ch, Institute of Geological Sciences, University of Bern, Bern, Switzerland © Springer International Publishing Switzerland 2016 Z.W. Kundzewicz et al. (eds.), Flood Risk in the Upper Vistula Basin, GeoPlanet: Earth and Planetary Sciences, DOI 10.1007/978-3-319-41923-7_3
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Z.W. Kundzewicz and M. Stoffel
1 Introduction Flood is a damaging presence of water in areas which are not normally submerged (e.g., outside of a river bed or of normal confines of a body of water), where damage potential, however, exists. Hence a flood is a combination of two elements —coincidence of the damaging element (abundant water) and of loss potential. Intense and/or long-lasting rainfall may cause a river (fluvial) flood, a flash flood, an urban flood, a pluvial flood, a groundwater flood, or a sewer flood. In moderate and cold climates, floods can be also caused by snowmelt (sometimes enhanced by rain and/or ice jams). Important to flood generation are antecedent conditions, e.g., saturation of natural storage in the catchment (surface water storage and soil moisture), resulting from earlier precipitation and/or snowmelt. Should storage be limited because groundwater levels are elevated and soil moisture is at maximum capacity, then even moderate amounts of rain can generate a large flood (such as was the case in Poland in May/June 2010). However, the development of a very dry, crusted soil after a prolonged period without rain, can rapidly convert heavy rainfall to runoff (because the runoff coefficient is higher) as well, and would usually result in a flash flood. A combination of factors can contribute to the generation of a large event (e.g., the joint occurrence of rainfall and snowmelt). Other natural factors that may induce fluvial floods include landslides, reducing conveyance (obstructing riv
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