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River floods

Hungary: Vulnerabilities - Present flood risk

The regularly inundated area due to floods and the so-called excess waters is large, about one third of the territory of the country. In the Hungarian Great Plains large areas have no natural drainage (23).

About one quarter of the country is exposed to floods, which is exceptional in Europe. Flood dykes of 4200 km length protect 700 settlements, 2.5 million people, 2000 industrial plants and indirectly about 30% of the GDP. Flood protection has been successful in the past, but recently the Tisza Basin has exhibited new signs of increasing risks: peak flood levels show a clearly increasing trend. Reasons are manifold: primarily impacts of land uses changes primarily in upstream countries and climate alterations are speculated to which siltation of the flood plain bed should be added. Further increases in peak water level are anticipated which could hardly be tolerated by the existing protection system (23).

The height of the levees (the design flood level) was calculated as the hundred-year flood level plus 1.0 metre safety height. In the case of floods exceeding the design flood level the opening of emergency storage reservoirs facilitated the reduction of flood peaks (27).

Flood levels have increased considerably in the past decades. This was due to the weather’s becoming more extreme, due to the reduction of discharge capacity of the channel, and due to anthropogenic impacts on the catchment basin (27).

In Hungary, draining of the Tisza wetlands began in the 19th century and today some 500,000 people, 5% of Hungary's population, live on land reclaimed from the Tisza. As a result of efforts to reduce flood impacts by building higher dikes and continued river bed regulation, there is a deposit of silt within the main bed, which has inadvertently increased flood risks (21).

In addition to the altered nature of floodplains, the reduction in upper and mid-catchment water retention leads to more flood events downstream where river channels and small floodplains no longer contain peak water levels, even from minor flood events. The lack of coordinated mechanisms for mitigating flooding already in the upper catchment may lead to compounded impacts downstream (21).

Contaminated and toxic waters

When flooding occurs, industrial sites, mining areas, agricultural fields and municipal waste facilities become inundated and spill bio-hazards into the Tisza waters. This is a major problem because several Hungarian communities receive their drinking water from bank-filtered wells. The trans-boundary impacts of flooding are cumulative, especially for those countries further downstream. Within the Hungarian plain, disruptive downstream flooding and consequent disruption of economic activity has been frequent over the last years. For example, during the serious floods of April 2000, the level of the Tisza River in the city of Szolnok was 10.4 meters higher than the mean water level (21).

Many Eastern European cities that are prone to floods are in close proximity to industrial areas, mining operations, or are host to brownfield sites. As a result, people and settlements in the region run a significant risk to be exposed to contaminated and toxic waters. For instance, in 2000, a flood in Romania (Baia Mare) resulted in the breach of a tailings pond and of cyanide-laced waste from a gold mining operation being wasted into the Tiza and Danube Rivers. The accident not only affected the ecosystems of these rivers, but the drinking water of approximately two million people in Hungary. Similarly, flooding of a chemical plant in the Czech Republic in 2002 resulted in chlorine and other chemicals being washed into the Elbe and the deposition of dioxins on the shores of the River (29).

Hungary: Vulnerabilities - Future flood risk

The frequency and intensity of large precipitation volumes are projected to increase. Rain related drainage increases in winter, the snow related delayed drainage comes earlier, and floods can come earlier. The rivers will peak at higher levels, with high uncertainty. … Intensity and frequency of floods at inhabited areas are expected to increase (22).

It is highly probable that climate change will affect the high flows of the rivers to some extent, but it cannot yet be justified that these changes will be dominating. Another two affecting factors are the anthropogenic changes on the catchment and the occurrence of weather situations that have not yet been recorded. Therefore the level of flood protection must be anyway increased. It is highly probable that more and more extreme floods will occur, although their time of occurrence cannot be assessed (27).

Europe: casualties in the past

The annual number of reported flood disasters in Europe increased considerably in 1973-2002 (1). A disaster was defined here as causing the death of at least ten people, or affecting seriously at least 100 people, or requiring immediate emergency assistance. The total number of reported victims was 2626 during the whole period, the most deadly floods occurred in Spain in 1973 (272 victims), in Italy in 1998 (147 victims) and in Russia in 1993 (125 victims) (2).

Throughout the 20th century as a whole flood-related deaths have been either stable or decreasing while economic burdens of flooding and related societal disruptions have become decidedly worse. 20th century flood disaster death tolls have been typically averaging fewer than 250 per year (3).

Europe: flood losses in the past

The reported damages also increased. Three countries had damages in excess of €10 billion (Italy, Spain, Germany), three in excess of 5 billion (United Kingdom, Poland, France) (2).

Expressed in 2006 US$ normalised values, total flood losses over the 1970–2006 period amounted to 140 billion, with an average annual flood loss of 3.8 billion (4). Results show no detectable sign of human-induced climate change in normalised flood losses in Europe. There is evidence that societal change and economic development are the principal factors responsible for the increasing losses from natural disasters to date (5).

Policy makers should not expect an unequivocal answer to questions concerning the linkage between flood-disaster losses and anthropogenic climate change, as this field will very likely remain an important area of research for years to come. Longer time-series of losses are necessary for more conclusive results (6).

Europe: flood frequency trends in the past

In 2012 the IPCC concluded that there is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at a regional scale because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes. There is low confidence (due to limited evidence) that anthropogenic climate change has affected the magnitude or frequency of floods, though it has detectably influenced several components of the hydrological cycle such as precipitation and snowmelt (medium confidence to high confidence), which may impact flood trends (31).

Despite the considerable rise in the number of reported major flood events and economic losses caused by floods in Europe over recent decades, no significant general climate‑related trend in extreme high river flows that induce floods has yet been detected (7).

Hydrological data series do not indicate clear upward trends in the frequency and magnitude of floods in Europe. The direct anthropogenic causes include land use change, river channel modifications and increased activities in areas vulnerable to floods. Thousands of square kilometres of impermeable surfaces have been created, coastal urbanization has been extensive. The overall impact of these changes probably exceeds the impact of trends in meteorological variables in today's Europe (8).

In western and central Europe, annual and monthly mean river flow series appear to have been stationary over the 20th century (9). In mountainous regions of central Europe, however, the main identified trends are an increase in annual river flow due to increases in winter, spring and autumn river flow. In southern parts of Europe, a slightly decreasing trend in annual river flow has been observed (10).

In the Nordic countries, snowmelt floods have occurred earlier because of warmer winters (11). In Portugal, changed precipitation patterns have resulted in larger and more frequent floods during autumn but a decline in the number of floods in winter and spring (12). Comparisons of historic climate variability with flood records suggest, however, that many of the changes observed in recent decades could have resulted from natural climatic variation. Changes in the terrestrial system, such as urbanisation, deforestation, loss of natural floodplain storage, as well as river and flood management have also strongly affected flood occurrence (13).

Europe: projections for the future

IPCC conclusions

In 2012 the IPCC concluded that considerable uncertainty remains in the projections of flood changes, especially regarding their magnitude and frequency. They concluded, therefore, that there is low confidence (due to limited evidence) in future changes in flood magnitude and frequency derived from river discharge simulations. Projected precipitation and temperature changes imply possible changes in floods, although overall there is low confidence in projections of changes in fluvial floods. Confidence is low due to limited evidence and because the causes of regional changes are complex, although there are exceptions to this statement. There is medium confidence (based on physical reasoning) that projected increases in heavy rainfall would contribute to increases in rain-generated local flooding, in some catchments or regions. Earlier spring peak flows in snowmelt- and glacier-fed rivers are very likely, but there is low confidence in their projected magnitude (31).

More frequent flash floods

Although there is as yet no proof that the extreme flood events of recent years are a direct consequence of climate change, they may give an indication of what can be expected: the frequency and intensity of floods in large parts of Europe is projected to increase (14). In particular, flash and urban floods, triggered by local intense precipitation events, are likely to be more frequent throughout Europe (15).

More frequent floods in the winter

Flood hazard will also probably increase during wetter and warmer winters, with more frequent rain and less frequent snow (16). Even in regions where mean river flows will drop significantly, as in the Iberian Peninsula, the projected increase in precipitation intensity and variability may cause more floods.

Reduction spring snowmelt floods

In snow‑dominated regions such as the Alps, the Carpathian Mountains and northern parts of Europe, spring snowmelt floods are projected to decrease due to a shorter snow season and less snow accumulation in warmer winters (17). Earlier snowmelt and reduced summer precipitation will reduce river flows in summer (18), when demand is typically highest.

For the period 2071-2100 the general feature is a decrease of extreme flows in areas where snowmelt floods are dominating in the present climate. The hundred year floods will attenuate by 10-50% in northern Russia, Finland and most mountainous catchments throughout Europe. An increase by similar amount is projected in large areas elsewhere, whereas a mixed pattern is likely in Sweden, Germany and the Iberian Peninsula (2).

Increase flood losses

Losses from river flood disasters in Europe have worsened in recent years and climate change is expected to exacerbate this trend. The PESETA study, for example, estimates that by the 2080s, some 250-400 million Europeans could be affected each year (compared with 200 million in the period between 1961 and 1990). At the same time, annual losses due to river flooding in Europe could rise to €8-15 billion by the end of the century compared with an average of €6 billion today (24).

From an assessment of the implications of climate change for future flood damage and people exposed by floods in Europe it was concluded that the expected annual damages (EAD) and expected annual population exposed (EAP) will see an increase in several countries in Europe in the coming century (32). Most notable increases in flood losses across the different climate futures are projected for countries in Western Europe (Belgium, Denmark, France, Germany, Ireland, Luxembourg, the Netherlands and the United Kingdom), as well as for Hungary and Slovakia. A consistent decrease across the scenarios is projected for northern countries (Estonia, Finland, Latvia, Lithuania and Sweden). For EU27 as a whole, current EAD of approximately €6.4 billion is projected to at least double or triple by the end of this century (in today’s prices), depending on the scenario. Changes in EAP reflect well the changes in EAD, and for EU27 an additional 250,000 to nearly 400,000 people are expected to be affected by flooding yearly, depending on the scenario. The authors stress that the monetary estimates of flood damage are uncertain because of several assumptions underlying the calculations (only two emission scenarios, only two regional climate models driven by two general circulation models, no discounting of inflation to future damages, no growth in exposed values and population or adjustments, estimates of flood protection standards); the results are indicative of changes in flood damage due to climate change, however, rather than estimates of absolute values of flood damage (32).

Large differences across Europe

Annual river flow is projected to decrease in southern and south-eastern Europe and increase in northern and north-eastern Europe (19).

Strong changes are also projected in the seasonality of river flows, with large differences across Europe. Winter and spring river flows are projected to increase in most parts of Europe, except for the most southern and south-eastern regions. In summer and autumn, river flows are projected to decrease in most of Europe, except for northern and north-eastern regions where autumn flows are projected to increase (20). Predicted reductions in summer flow are greatest for southern and south-eastern Europe, in line with the predicted increase in the frequency and severity of drought in this region.

Climate-related changes in flood frequency are complex and dependent on the flood generating mechanism (e.g. heavy rainfall vs spring snowmelt), affected in different ways by climate change. Hence, in the regions where floods can be caused by several possible mechanisms, the net effect of climate change on flood risk is not trivial and a general and ubiquitously valid, flat-rate statement on change in flood risk cannot be made (25).

Flood risk tends to increase over many areas owing to a range of climatic and non-climatic impacts, whose relative importance is site-specific. Flood risk is controlled by a number of non-climatic factors, such as changes in economic and social systems, and in terrestrial systems (hydrological systems and ecosystems). Land-use changes, which induce land-cover changes, control the rainfall-runoff relations in the drainage basin. Deforestation, urbanization and reduction of wetlands diminish the available water-storage capacity and increase the runoff coefficient, leading to growth in the flow amplitude and reduction of the time-to-peak. Furthermore, in many regions, people have been encroaching into, and developing, flood-prone areas, thereby increasing the damage potential. Important factors of relevance to flood risk are population and economy growth, flood protection strategy, flood risk awareness (or flood risk ignorance) behaviour and a compensation culture (25).

Adaptation strategies - Current measures

Further rising of the height of flood levees will not provide an efficient means of flood control. Extreme weather events of the past years and the associated floods and droughts unambiguously indicated that the earlier water management practices couldn’t be continued. Instead of the approach of  “fighting the floods” the concept of “living with the floods” should be followed. Similar changes in the approach are needed in handling excess water and drought problems, which should be aimed at changing land uses and thus reducing the potential damage. Sufficient spaces should be secured for waters and as much water should be stored as possible, diverting these waters to places in water shortage (27). In the Tisza River Basin, for instance, diversification of agricultural land use, and the inclusion of agro-tourism, may help to reduce climate related risks (28).

Following the severe floods of the Tisza between 1998 and 2002, the Hungarian government has adopted an ambitious flood safety plan, the New Vásárhelyi Plan. This plan includes the diversion control of peak flood flows, the retention, use and subsequent return of water to the river, and a further water emergency storage (for a total volume of 1500 million m3),  the cleaning up of the floodplain, and transfer to areas with short supply. In parallel to enhancing flood safety, the plan is oriented to the development of agro-ecological farming practices, ecotourism and nature conservation, in which the constructed water reservoirs play an essential role in changing the landscape structure and land uses (21,23).

Along the Tisza River, in the case of a flood of 1000 years return period, five flood peak storage reservoirs will be able to affect the entire Hungarian Tisza reach. The planned 60 cm reduction of the flood peak will be achieved both locally and also along the whole course of the river. The reservoirs will be activated in each 30th – 40th year and the probability that all reservoirs will be filled simultaneously is less than 1% (27).

Adaptation strategies - Contaminated and toxic waters

Development of cities should be prevented in areas that are vulnerable to toxins, contaminants, or other health hazards that may arise as a consequence of the flooding of industrial and mining operations or brownfield sites. At the same time, concerted efforts need to be made to relocate existing industrial plants out of floodplains and to remediate brownfield sites (30).

Adaptation strategies - General

Non-structural measures are in better agreement with the spirit of sustainable development than structural measures, being more reversible, commonly acceptable, and environment-friendly. Among such measures are source control (watershed/landscape structure management), laws and regulations (including zoning), economic instruments, an efficient flood forecast-warning system, a system of flood risk assessment, awareness raising, flood-related data bases, etc. As flood safety cannot be reached in most vulnerable areas with the help of structural means only, further flood risk reduction via non-structural measures is usually indispensable, and a site-specific mix of structural and non-structural measures seems to be a proper solution. As uncertainty in the assessment of climate change impacts is high, flexibility of adaptation strategies is particularly advantageous (26).

EU Directive on flood risk management

The new EU Directive on flood risk management, which entered into force in November 2006, introduces new instruments to manage risks from flooding, and is thus highly relevant in the context of adaptation to climate change impacts. The Directive introduces a three-step approach (2):

  • Member States have to undertake a preliminary assessment of flood risk in river basins and coastal zones.
  • Where significant risk is identified, flood hazard maps and flood risk maps have to be developed.
  • Flood risk management plans must be developed for these zones. These plans have to include measures that will reduce the potential adverse consequences of flooding for human health, the environment cultural heritage and economic activity, and they should focus on prevention, protection and preparedness.


The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Hungary.

  1. Hoyois and Guha-Sapir (2003), In: Anderson (ed.) (2007)
  2. Anderson (ed.) (2007)
  3. Mitchell (2003)
  4. Barredo (2009)
  5. Höppe and Pielke Jr. (2006); Schiermeier (2006), both in: Barredo (2009)
  6. Höppe and Pielke Jr. (2006), in: Barredo (2009)
  7. Becker and Grunewald (2003); Glaser and Stangl (2003); Mudelsee et al.(2003); Kundzewicz et al.(2005); Pinter et al.(2006); Hisdal et al.(2007); Macklin and Rumsby (2007), all in: EEA, JRC and WHO (2008)
  8. EEA, JRC and WHO (2008)
  9. Wang et al.(2005), in: EEA, JRC and WHO (2008)
  10. Milly et al. (2005), in: EEA, JRC and WHO (2008)
  11. Hisdal et al. (2007), in: EEA, JRC and WHO (2008)
  12. Ramos and Reis (2002), in: EEA, JRC and WHO (2008)
  13. Barnolas and Llasat (2007), in: EEA, JRC and WHO (2008)
  14. Lehner et al.(2006); Dankers and Feyen (2008b), both in: EEA, JRC and WHO (2008)
  15. Christensen and Christensen (2003); Kundzewicz et al.(2006), both in: EEA, JRC and WHO (2008)
  16. Palmer and Räisänen (2002), in: EEA, JRC and WHO (2008)
  17. Kay et al. (2006); Dankers and Feyen (2008), in: EEA, JRC and WHO (2008)
  18. Andréasson, et al. (2004); Jasper et al.(2004); Barnett et al.(2005), all in: EEA (2009)
  19. Arnell (2004); Milly et al. (2005); Alcamo et al. (2007); Environment Agency (2008a), all in: EEA (2009)
  20. Dankers and Feyen (2008), in: EEA (2009)
  21. Burnod-Requia (2004)
  22. Hungarian Ministry of Environment and Water (2009)
  23. Somlyódy and Simonffy (2004)
  24. Ciscar et al. (2009), in: Behrens et al. (2010)
  25. Kundzewicz (2006)
  26. Kundzewicz (2002)
  27. Farago et al. (2010)
  28. Werners (2010)
  29. Gautam and Van der Hoek (2003), in: Carmin and Zhang (2009)
  30. Carmin and Zhang (2009)
  31. IPCC (2012)
  32. Feyen et al. (2012)

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