River floods Finland
Finland: Vulnerabilities – Floods in the past
Overview studies covering many Scandinavian rivers show no statistically significant trend in river peak discharge over the last century (33).
An increasing trend in streamflow magnitude and a trend in the timing of floods have been detected in annual and seasonal flows in near-natural catchments in Denmark, Finland, Norway and Sweden, given that they tend to arrive earlier in spring (32).
The current extreme phenomena are not necessarily caused by climate change, but the impacts of climate change can nevertheless be estimated on the basis of the extremes of the current climate. In the turn of July and August 2004, for example, exceptionally high precipitation in Finland caused floods that resulted in intestinal bacteria entering wells and tapwater systems, stormwater and wastewater had to be pumped to bodies of water without treatment, lots of nutrients and decomposing organic substances were conveyed to bodies of water from arable lands and shores, fish populations died in certain sections of rivers, buildings became surrounded by water, basements were filled with water in several towns, many households lost their electrical supply, there were interruptions in rail traffic, roads had to be closed and different parts of the country suffered crop damages (21).
Finland: Vulnerabilities – Future flood probability
Changes in dry and wet spell characteristics in Europe have been projected for 2021–2050 compared with 1961–1990, based on Regional Climate Model simulations under the A1B emission scenario. From the results it can be concluded that significant changes in dry and wet event characteristics are expected with high confidence in the southernmost (mainly France, Italy, and Spain) and northernmost (mainly Iceland and Scandinavia) regions of Europe, respectively. Southern Europe is most probably facing an increased risk of longer, more frequent, severe, and widespread droughts, while northern Europe is facing increased risk of intensified wet events. For precipitation, the most pronounced changes are found for the Iberian Peninsula in summer (−17.2%) and for Scandinavia in winter (+14.6%) (31).
Winter floods are expected to become more common in Southern and Central Finland, while spring floods will decline in Southern Finland. The heaviest floods in Southern Finland will be caused by heavy rain in the summer or autumn and may significantly increase in line with the increase in major rainfall. The heaviest floods in Northern Finland will still be caused by melting snow. Their magnitude will remain unchanged or decline slightly, as the decrease in floods caused by melting snow will be replaced by increases in precipitation and rain-induced floods. However, the level of snow and spring floods may temporarily increase in Northern Finland in the initial phase of climate change, but they will decline at a later stage (21,28).
In surveys on extreme floods values corresponding to the 100-year and 250-year, and sometimes even 1000-year flood have commonly been used. As for more frequent floods, return periods of 20 and 50 years are the main interests (22).
The risk of large-scale flooding is real in Lapland, because the amount of precipitation is expected to increase. When rivers are in flood, water and ice floes can damage electricity poles and transformers (23).
Finland: Vulnerabilities – Dam safety
Flood risks and dam safety are affected by climate change. According to climate change projections, the one, five and 14-day design precipitation values may go up by 35–65% by the end of this century compared to 1961–1990 (24). The increase is the largest in the period from January to June. This would lead to a dramatic increase of design flood; e.g. for a 2,000 km2 sub catchment of the Kyrönjoki River in Ostrobothnia the increase of peak discharge was estimated to be 70% (25). Major problems look unlikely because most dams have quite large spillways (28).
Finland: Benefits from climate change
In principle, the reduction in snow cover and extension of areas that remain open in winter may have positive impacts, because these events will ease spring floods and balance the seasonal variations in water systems. The period of groundwater absorption will be extended and the groundwater resources will increase (21).
Changes in the timing of floods will affect hydroelectric power production and water regulation practices. The reduced need for diversion caused by increased winter runoff and reduced spring floods will increase the amount of energy produced by hydroelectric power. In lake systems, the time of the design flood will move from spring to summer or, in the central lakes of the largest systems, to winter. In order to ensure flood prevention and the resistance of dams, reservoir space must be left in these lakes in order to prepare for autumn floods or even winter floods. If the design floods of dams do increase, this could require expensive investments in dams, for example, in floodgate structures, spillway crests or diversion channels (21).
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 (29).
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
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 (29).
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 (26).
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 (30). 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 (30).
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 (27).
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 (27).
Adaptation strategies – Contingency Planning
Particularly the environment centres located in Western and Northern Finland, in whose area floods occur regularly every year, possess the know-how and professional skill associated with preparing for floods, flood protection and operational flood prevention. Good cooperation with rescue services is important for flood prevention. Finland is relatively well prepared for floods. For example, the most significant agricultural regions, such as the region of the River Kyrönjoki, are protected against flooding up to certain limits (21).
However, climate change may cause unpredictability. In the flood areas of Ostrobothnia, for example, people have known for decades how to prepare for spring floods because the annual rhythm of floods is fairly regular. Preparation for major floods at other times, for example in the winter, is still challenging because it is difficult to predict situations of this kind. Prediction is easier in lake districts, for example in Saimaa and Päijänne, where flood waters move more slowly down the lake routes and where there is enough time to make room for floods caused by the melting of snow in particular. The prediction of floods caused by the melting of snow and their consequences is also usually possible in Lapland. Preparing for floods caused by heavy rains is the most difficult task (21).
Private citizens can try to prevent flood damage by monitoring flood warnings and following the instructions from the authorities given in connection with them, such as protecting properties with sand bags, sealing doors, blocking sewers and underdrains, moving valuable items to a safe location, etc. (21).
It is important to prepare safety plans and, if necessary, risk assessments of dams taking the occurrence of extreme floods into consideration. Plans and regular drills are needed to secure flood prevention and rescue operations (21).
A traditional way of preparing for un expected catastrophes has been to take out insurance. However, real estate insurance or home insurance policies do not generally cover damage caused by the flooding of water systems; only damage caused by heavy rain is covered in some cases. There are some insurance products on the market that will compensate for damage comparable to that caused by climate change in certain situations specified in their terms and conditions. In addition to this, the Government has created various schemes to compensate for damage caused by exceptional weather either in part or within the framework of available appropriations. Flood compensation can be paid for damage caused by extraordinary flooding of water systems and for costs arising from the prevention of damage using an annual appropriation in the State budget. Damage caused by flood to growing crops can be compensated for on the basis of the Crop Damage Act (21).
The Finnish environmental administration together with the Finnish rescue service authorities are responsible for flood prevention and protection in Finland. Regional environment centres (REC) look most after flood management and regional rescue services will take charge in the case of hazardous flood. Finnish Environment Institute's (SYKE) role is to do flood research, support regional authorities in and supply tools for flood prevention and protection. It is also responsible for national hydrological monitoring and flood forecasting. At regional level, the municipalities are responsible for land use planning, which indeed is an important means for flood damage prevention (22).
Adaptation strategies – Spatial Planning
A task force on extreme floods has considered flood problems caused by climate change. The task force has identified 65 of the most significant targets of flood damage where the possibilities to reduce flood damage have to be surveyed. According to the task force’s proposal, general plans will be drawn up for the regions to limit damage. Flood maps will also be required for flood damage targets in order to improve the planning of land use, operational flood prevention and rescue operations (21).
The surveying of risk sites suffering from floods, as well as general plans for risk sites proposed by the task force on extreme floods, are important planning methods for reducing the flood risks of the existing functions. Alternatives for suitable flood protection structures, temporary flood control structures, changes in regulation practices, etc. should be separately considered for each risk site. The impacts of climate change should be taken into consideration in the general plans. The fact that climate change may result in increased flooding and increase the risk of extreme floods can lead to the further requirements for flood protection for settlements and risk sites, and it may also be necessary to change the design of existing flood protection structures and, for example, construct higher banks (21).
The reduction of flood risks, and the avoidance of construction in flood risk areas in particular, can be influenced by land use planning. Land use planning and concentrating construction outside flood risk areas are the cheapest ways to avoid flood damage. Advance planning of functional cooperation between rescue and water services authorities and the restriction of damage is essential (21).
In Finland the Land Use and Building Act emphasizes the importance of taking the risk of flood or landslide into account in land use planning and building projects. Regional environment centres give recommendations for the lowest permissible building site levelswith respect to floods for inland shores and shores of the Baltic Sea. The recommendations regarding inland waters are typically based on the flood level of the watercourse concerned recurring only once in 50 years on average, added by a discretionary additional height (0.3 m to 1.0 m) and a wave margin. In some cases a recommendation can be based on the highest observed flood level or upper limit for reservoir operation. A recommendation can be given as a guideline for an entire lake, or in more specific sense for an individual building site (22).
Adaptation strategies - 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 Finland.
- Hoyois and Guha-Sapir (2003), In: Anderson (ed.) (2007)
- Anderson (ed.) (2007)
- Mitchell (2003)
- Barredo (2009)
- Höppe and Pielke Jr. (2006); Schiermeier (2006), both in: Barredo (2009)
- Höppe and Pielke Jr. (2006), in: Barredo (2009)
- 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)
- EEA, JRC and WHO (2008)
- Wang et al.(2005), in: EEA, JRC and WHO (2008)
- Milly et al. (2005), in: EEA, JRC and WHO (2008)
- Hisdal et al. (2007), in: EEA, JRC and WHO (2008)
- Ramos and Reis (2002), in: EEA, JRC and WHO (2008)
- Barnolas and Llasat (2007), in: EEA, JRC and WHO (2008)
- Lehner et al.(2006); Dankers and Feyen (2008b), both in: EEA, JRC and WHO (2008)
- Christensen and Christensen (2003); Kundzewicz et al.(2006), both in: EEA, JRC and WHO (2008)
- Palmer and Räisänen (2002), in: EEA, JRC and WHO (2008)
- Kay et al. (2006); Dankers and Feyen (2008), in: EEA, JRC and WHO (2008)
- Andréasson, et al. (2004); Jasper et al.(2004); Barnett et al.(2005), all in: EEA (2009)
- Arnell (2004); Milly et al. (2005); Alcamo et al. (2007); Environment Agency (2008a), all in: EEA (2009)
- Dankers and Feyen (2008), in: EEA (2009)
- Marttila et al. (2005)
- Dubrovin et al. (2006)
- Kirkinen et al. (2005)
- Tuomenvirta et al. (2000), in: Ministry of the Environment (2006)
- Vehviläinen (2001), in: Ministry of the Environment (2006)
- Ciscar et al. (2009), in: Behrens et al. (2010)
- Kundzewicz (2006)
- Ministry of the Environment and Statistics Finland (2009)
- IPCC (2012)
- Feyen et al. (2012)
- Heinrich and Gobiet (2012)
- Wilson et al. (2010), in: Mediero et al. (2014)
- Bering Ovesen et al. (2000); Forland et al. (2000); Hyvarinen (2003); Lindström and Bergström (2004); Thodsen (2007), all in: Kwadijk et al. (2016)