The Frequently Asked Questions listed below provide basic information about floods in Europe.
What is a flood and what causes it?
A flood event in general is any type of situation where water temporarily covers land outside its normal confines. Although every flood is a unique phenomenon, several types of floods can be distinguished, including fluvial, pluvial, groundwater and flash floods. The most common type is where a river overflows its banks due to a large input of rainfall or snowmelt. Floods can result from many causes, including torrential rains and dam and levee breaks. Heavy rainfall is the main cause of large floods. Floods, however, can also occur suddenly or due to conditions built up over days, meaning advance warning is sometimes possible. Note: STAR-FLOOD looks at riverine floods only.
How often do floods occur in Europe?
Floods are the most prevalent natural hazard in Europe. During the period 1950-2005, 240 flood occurred in Europe, 47 of those were major, i.e., the number of registered casualties is greater than 70 and/or the direct damage is larger than 0.005% of the EU GDP in the year of the disaster (Barredo, 2007). For the location of these major floods, see Figure 1, major flood losses in Europe 1950-2005.
Floods are often categorized by how likely they are in a given time period, i.e. their probability. For example, 1:25 means yearly probability of a flood is 4%. This means that on average this flood will occur once in 25 years. Statistically, however, it is possible to have the associated level of flooding more than once in that time period.
© EC Joint Research Centre (used with permission of authors)
Figure 1: major flood losses in Europe 1950-2005. 1 to 23: flash floods, 24 to 44: river floods, 45 to 47 storm surge floods. A triangle feature represents very large regional events. No major flood events were reported during the study period in the EU’s regions not included in the map. Source: Barredo, 2007; JRC; http://floods.jrc.ec.europa.eu/flood-risk/flood-disasters.html
Where do floods occur in Europe?
On the website of the JRC (the Joint Research Centre, the European Commission’s in-house science service) a map with current floods in Europe can be found.
What is flood risk?
There is no unique all-encompassing definition for ‘flood risk’, but in essence, flood risk is the possibility of loss, damage, or any other undesirable event in case of flooding and has two components: the chance (or probability) of an event occurring and the impact (or consequence) associated with that event.
Most countries have set standards regarding to the flood risk that they are willing to accept. Standards are often based on the individual or risk of dying, the total number of fatalities or the expected damage caused by a flood.
Every country has a certain flood risk level which is assessed either by fixing an acceptable number of fatalities or a maximum acceptable total cost of flooding including the expected flood damage. Once the different causes of flooding are identified, the safety standards per cause of flooding can be developed. Flood risk level will be related to these different safety standards.
Safety standards throughout Europe (and the world) differ significantly. This differentiation is caused among others by the large variety of physical and socioeconomic circumstances, the variety in the willingness to accept flood risk and the variety in flood risk management strategies. There is a factor 10 difference between the Netherlands and Germany, for instance. As the potential impacts of fluvial, pluvial, groundwater and flash floods often differ, the safety standards often differ per type of flooding as well.
Will flood risk increase in the future?
Yes. Mainly because of population growth and related increasing urbanization (often in floodplains) , and economic growth, and climate change. In addition, the phenomenon of the safe development paradox, where policies that are intended to make hazardous areas safer actually increase the potential for catastrophic damages. These policies serve to stimulate a greater density of development in floodplains than would likely have occurred in the absence of these policies, which means that more people and property are at risk when a flood event occurs.
Climate change is expected to lead to greater risks of flooding in many areas but the details are very difficult to predict. For the coming decades, it is projected that global warming will intensify the hydrological cycle and increase the magnitude and frequency of intense precipitation events in most parts of Europe, especially in the central and northern parts. This will likely contribute to an increase in flood hazard triggered by intense rain, particularly the occurrence of flash floods. Flood hazard may also rise during wetter and warmer winters, with increasingly more frequent rain and less frequent snow. On the other hand, ice-jam and early spring snowmelt floods are likely to reduce because of warming.
In addition, the growing urban population (in 2030, 60% of the world’s population will be living in cities) invariably increases flood risks as well, as a result of heightened vulnerability, due to the fact that more people live on relatively smaller areas than before.
What were the most devastating floods in Europe in the past 50 years?
Floods occur all around Europe, but the effects on communities differ per location and event. Some events take place in uninhabited areas and have no impact on societies, others are so small that they are not noticeable on an economic or personal scale, and yet others wipe away entire villages.
During the period 1960-2009, 3539 floods (all types) occurred globally, 298 of those (12% of the total) took place in current EU member states (source: www.emdat.be), causing almost 5500 people their lives, and resulting in close to US$ 106 billion in damage. 33 of the floods were categorized as ‘flash floods’, 81 as a ‘flood’, 183 as a ‘general flood’, and there was one storm surge/coastal.
In 1973, a flash flood in Spain (Granada, Almeria, Murcia), killed 500 people and is therefore the deadliest flood in the EU during this period. In 1994, a flood in Italy (Piemont, Ligura, Cuneo, Tuscany, Piacenza) not only took 68 lives, but also caused US $9,300,000,000 in economic damages, making it the most costly flood of the pas 50 years.
Looking at the overall picture, flash floods are the most devastating floods; when it comes to causing casualties and number of affected people – in total, but also on average per event. General floods have caused the most economic damage in total, but again, flash floods on average cause higher damages than other flood events.
How do societies deal with floods?
Throughout the centuries, Europe has suffered from many floods, and urban flooding is a serious and growing challenge. Despite many efforts to protect against floods, from artificial hills to earth dikes covered with seaweed to river dikes and major storm surge barriers, it has proven impossible to eradicate them completely. For this reason attention in Europe has shifted in the past decades from protection against floods, or flood defence mechanisms such as dikes and levees, to managing flood risks, enabling a society to cope with flood risks in a flexible and multifaceted way and to recover to the initial state as quickly as possible after a flood event. In Europe, this shift is reflected in the Flood risk directive of October 2007 (see next question).
Which policies have been specifically designed for floods in the EU and why are they there?
In a globalised world, all societies critically depend on each other in an economic sense. Therefore, it is in the interest of the whole of the EU to make all EU regions resilient to floods. On a European scale, the so-called Flood risk directive went into force in 2007. This is the first European directive that deals specifically with floods, and with it, Europe shifted its flood management from protection against floods to managing the risks of floods. Alongside the Hyogo Framework for Action, a ten-year plan to make the world safer from natural hazards (2005-2015), this Directive guides countries in the process of diversification of flood risk management strategies. Moreover, Member States have to consider many different types of measures and all aspects of flood risk management, but the Directive does not set any priorities: it is up to the Member States what measures they include in their flood risk management plans, so these measures may (and will) differ per country, and per city.
See also: D1.1.3 European flood regulation
What is flood (risk) management?
The effects of floods are extraordinarily complex and include both beneficial (i.e. positive) and adverse (i.e. negative) impacts on society and the environment. Generally, however, flood management is concerned with protecting society and hence risk is typically concerned with the likelihood of an undesirable consequence and our ability to manage or prevent it. The categories of flood management strategies as summarized in the STAR-FLOOD proposal are: prevention, defence, mitigation, preparation and recovery. These categories are umbrella categories under which various measures can be ranked. They can be seen as subsequent steps in a chain of responses to flood risks.
What is flood risk governance?
Lange et al. (2013) define ‘governance’ as a process of—more or less institutionalized—interaction between public and/or private entities ultimately aiming at the realization of collective goals.
STAR-FLOOD aims to support authorities and other stakeholders in vulnerable urban agglomerations in Europe by mapping and evaluating existing flood risk governance, and by designing flood risk governance arrangements that make these agglomerations more resilient to flooding and that are at the same time legitimate, efficient and effective.
 Philipp Lange , Peter P.J. Driessen , Alexandra Sauer , Basil Bornemann & Paul Burger (2013): Governing Towards Sustainability—Conceptualizing Modes of Governance, Journal of Environmental Policy & Planning, DOI:10.1080/1523908X.2013.769414. http://dx.doi.org/10.1080/1523908X.2013.769414