The Role of Floods in Urban Environments

Floods are the natural hazard that affects the largest population in the world. In addition, the demographic evolution moves from a population majority located in rural areas to urban areas and changes toward the city. Many of the main European cities, such as Paris, Vienna and Budapest, are located in fluvial plains alongside more or less mighty rivers. This geographical situation contributes to floods taking on a more localized impact, no longer solely determined by river discharge. Instead, the evolving flood patterns are increasingly influenced by the interaction between the discharge resulting from torrential rainfall and the soil’s sealing, leading to a greater runoff. This means that the potential risk for loss of life is much higher than it was just a few decades ago. In this chapter, we analyze the evolution of urban flooding, and how the effects of large river floods have changed, and which mitigation measures have been taking place, together with the demographic increase that has occurred in these populations in recent centuries.