Vulnerabilities – Dams and Reservoirs

There are around 10,000 dams of varying size, type and age spread across Sweden. Most of the larger dams are hydropower dams, but there are also some large tailings dams to deal with mining waste. Most of the dams of interest in terms of safety are in Norrland. Most were built before the 1980s and are power plant dams (1).

About 200 power plant dams and a few mining dams have the highest consequence classes. Failure at one of these dams can have very serious consequences for life, infrastructure and the environment (2). These largest dams have been built to withstand very extreme flows. Climate change entails a risk of the flow for which these dams are designed increasing in parts of the country, but there is considerable uncertainty. Measures are needed at about two-thirds of the 120 risk class I installations. The costs of adaptation to the Swedish Flow Committee’s guidelines are estimated at SEK 2 billion (3).

At maximum water level it is recommended that high risk class dams are able to handle an inflow with a return period of at least 100 years. The 100-year flow will increase substantially, particularly in westernand northeasternGötaland and south-western Svealand (4).

From an international review of hydropower station dams experts concluded that dam failure due to surface erosion on embankment dams is possible with overflows with flows of considerably shorter return periods than the flows for which they are designed (5).

The climate issue adds an extra uncertainty factor that motivates continued studies into the effects on maximum flows and increased safety margins in specification work (3). The Swedish Commission on Climate and Vulnerability (1) states that dam safety ought to be examined in view of both today's climate and climate change.

The impact of recent flooding on dams

In the mid-1980s, several high flows and floods took place in various locations across the country. During a high flow in autumn 1985, a dam structure collapsed at the Noppiskoski power station in Dalarna. Other dam damage occurred in Sysslebäck in 1973 and Aitik in 2000. The damage was due to a combination of heavy precipitation, overflowing and technical problems (1).

No major damage occurred to dam structures during the high flows (estimated as flows with a return period of 100 years) in southern Norrland in July 2000, but around 50 incidents involving dam structures were reported. In almost half of them, the flows were greater than the maximum discharge capacity from the spillways which can be used without extraordinary measures being taken (1).

The July flows of 2000 in Norrland were exceeded several times in the 20th century in the affected areas. The likelihood of them being repeated in the near future is judged to be great (6). The intensive and persistent rain in the Sundsvall area in August/September in 2001 resulted in a minor dam breach that caused the flooding of minor roads. Other dams in risk class 2  or lower also ran the risk of overcapacity.

Vulnerabilities – Transport – Shipping

Climate change will probably not affect shipping and aviation to any great extent (7).

Vulnerabilities – Infrastructure – Telecommunications

Telecommunications with overhead power lines and masts will be affected by a changed climate. In particular there will be an increased risk of storm felling due to reduced occurrence of ground frost and increased extreme wind speeds. Work to replace overhead power lines with buried cables for electricity distribution has been intensified since the storms of 2005 and 2007 (7).

Vulnerabilities – Transport - Road

Climate change may have significant consequences for road networks. These are often constructed close to water, and the expected increase in precipitation and increased flow rates will bring with it flooding, the washing-away of roads and road verges and damaged bridges. High flow rates pose increased risks of landslides, which in turn increase the risk of damage to roads (7).

The road networks are also affected by increased temperature and reduced depth of ground frost. A reduced depth of ground frost means reduced deformations in road superstructure and road surface. Increased maintenance may be required where road construction is based on ground frost. A higher temperature and higher groundwater levels may, however, result in increased rutting. Overall, measures are shifted from being related to ground frost to being related to heat and water load (7).

A few major incidents have occurred since 2001 (1):

• Several high road embankments were washed away in Hagfors in 2004 after heavy rain. The total costs exceeded SEK 20 million.
• In the summer of 2006 a road embankment near Ånn was washed away after heavy rain and an accompanying high flow. The road was repaired after two weeks at a cost of SEK 6 million.
• In December 2006 there was a large landslide south of Munkedal. The landslide encompassed an area measuring 550 metres by 250 metres in a depression through which the E6 trans-European road runs. The repairs took almost two months. The direct costs for repairing the road network, including the restoration of bypass roads and ferry services provided during the disruption, totalled some SEK 120 million, excluding the cost of restoring the Taske river. Costs for diversions and other incidentals comprised more than 50 percent of the direct costs. The indirect consequences were extensive. The two allocated diversion routes for long-distance traffic entailed extra journeys of 40 and 55 km respectively. The indirect costs have been estimated at the same magnitude as the direct costs.

The costs of all major incidents due to high flows and landslides the past 12 years are estimated at SEK 1,200 million. Landslide frequency is expected to increase in areas already at high risk, namely western Götaland and western Svealand, as well as along most of the east coast. The situation is judged to be particularly serious in the Göta valley, Bohuslän and along some of the tributaries to Lake Vänern, although the situation can also turn serious in other parts of the country. Major landslides resulting in damage costs in excess of SEK 100 million are expected to increase in the future (1).

The Swedish Road Administration estimated the costs of preventing serious erosion and flood damage at SEK 150−500 million in the short term. The corresponding cost to prevent landslide totals at least SEK 200 million. Cost estimates for the longer term are less certain, and depend on whether the measures can be taken in conjunction with normal alterations. One assessment estimates measures to prevent damage from erosion, flooding and landslide at SEK 1,000−2,000 million in the long term (1).

Road safety

As one of the most common reasons for slippery roads in wintertime, hoar frost can reduce surface friction and affect traffic safety. The risk of winter road hoar frost is subjected to changes in the warming climate. Observations over the period 2000 – 2016 show that hoar frost risks have decreased in the south of Sweden and increased in central Sweden. This is mainly due to the strengthened winter North Atlantic Oscillation (NAO) over the last few decades, which resulted in warmer and wetter winters in Sweden. The reduction in hoar frost risk in the southern part of Sweden is mainly due to an increase in road surface temperature, while the increasing hoar frost risk in central Sweden is dominated by the increase in relative humidity, which favours the occurrence of hoar frost. The latter shows that hoar frost risk does not necessarily decrease in a warming climate, due to the wetting tendency of the region (9).

Over the next 30 years, the NAO will continue to strengthen and lead to warmer and wetter winters for most of Sweden. The warming may increase the mean road surface temperature in central Sweden, eventually leading to a decrease in the winter road hoar frost risk. However, the winter road hoar frost risk may continue to increase into the near future in the mountainous area in the central and northern parts of Sweden, due to the much lower mean road surface temperature and the increase in humidity in these regions (9).

Traffic accidents involving personal injury or death due to slippery conditions account for up to 50% of the over 27,000 injuries in recent years in Finland, Norway and Sweden, and result in annual medical costs and economic production losses up to €16.2 billion yearly (11). Also, pedestrian slip injuries are a major contributor to social costs. The climate change impacts on driving and walking conditions in Finland, Norway and Sweden have been assessed for a worst-case climate change scenario (RCP 8.5) for 2050. According to this assessment, snowy and icy road surface conditions strongly decrease during the cold season. In autumn and spring, the number of zero-degree-crossing days decrease, and sidewalks show a decrease in slipperiness. In winter, this number increases, and sidewalks become more slippery (10). 

Vulnerabilities – Transport – Rail

Increased and more intensive precipitation means flooding and washing-away of bank structures, with the risk of accompanying landslides and landslips. The expected rise in temperature during the summer brings an increased risk of sun kinks. Stronger winds, particularly in Southern Sweden, may bring an increased risk of storm felling of forest and of damage to the power supply for the railway network (7). The increased temperature reduces the risk of rail failure in the winter, but increases maintenance needs in the summer.

In the summer of 2006 a railway embankment in Ånn collapsed after heavy rain upstream caused a high flow with accompanying erosion then collapse. A train passed the incident site shortly before the collapse. An incident involving mortal danger or personal injury is therefore not far off (1).

Vulnerabilities – Damages due to permafrost thawing

The thawing of the permafrost in the Arctic is causing damage to the infrastructure and buildings of the Arctic states. According to model projections, the costs of this damage will be $182 billion for all Arctic states combined by mid-century, under a moderate scenario of climate change. Under a high-end scenario of climate change the costs may rise to $276 billion by mid-century. Russia is expected to have the highest burden of costs, ranging from $115 to $169 billion depending on the scenario. For Scandinavia and Iceland, the estimated costs are $36.4 billion (moderate scenario) to $53.9 billion (high-end), while the range for North America is $30.4 - $53.1 billion. These are the mean values for the estimates; the uncertainty range of these costs is tens of percent (12).

In these model projections mid-century is defined as the period 2055–2064, and the damage is compared to the reference period 2015–2024. The results show that under the moderate scenario of climate change 29% of roads, 23% of railroads, and 11% of buildings will be affected by permafrost degradation. Under the high-end scenario, these numbers are 44% of roads, 34% of railroads, and 17% of buildings.

Adaptation strategies – building

In the area of legislation, the Planning and Building Act was amended in 2008 so that buildings may only be erected at suitable places and account has to be taken of the risk of accidents, flooding and erosion in municipal comprehensive plans and detailed development plans. Guidance has been prepared on how clearer and stronger consideration should be given to these risks, and methods have been developed for adapting planning and construction to prevent, avoid and minimise the adverse effects of climate change (7).

It is the municipalities that are responsible for physical planning, contingency planning and emergency services (7). The Swedish Commission on Climate and Vulnerability (1) consider it important to assist municipalities and clarify how flooding, erosion and landslides due to climate change are to be taken into account in the municipal planning process. The National Board of Housing, Building and Planning, should therefore, with the support of other affected authorities, draw up guidelines for the planning, location and elevation of new building development, including wastewater systems, with respect to the risks of flooding, landslides and erosion.

When carrying out town planning, the increasing temperatures during the summer should also be taken into consideration when designing buildings. Buildings have a very long lifetime, and a change-over should therefore be initiated early in order that the adaptation can be carried out when building new properties and when carrying out renovation and conversion work (1).

Adaptation strategies - Dams and Reservoirs

Activities are underway to improve dam safety (e.g. via spillway dimensioning) and to re-design major dam discharges (8). Development is underway to coordinate dam failure contingency planning for the major hydropower rivers (1).

Adaptation strategies – Transport – roads and rail

The risks to the road and rail networks of landslides, washing-away and flooding have been analysed and remedial action has been taken where necessary. An extensive tree-securing project is also underway for the railway network, where trees are felled to enhance safety in the event of strong winds. Knowledge on the consequences of climate change and options for action is passed on to forest owners and farmers (7).

The obligation of the municipalities to take account of the risks of floods and landslides in physical planning should become clearer in legislation and guidelines should be drawn up. Funds should be earmarked for the climate adaptation of the transport infrastructure. The risks, particularly in the road and rail networks, should be mapped and measures implemented (1).

References

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

1. Swedish Commission on Climate and Vulnerability (2007)
2. Swedenergy (2002); SveMin (2007), both in: Swedish Commission on Climate and Vulnerability (2007)
3. Svenska Kraftnät (2007), in: Swedish Commission on Climate and Vulnerability (2007)
4. Carlsson et al. (2006), in: Swedish Commission on Climate and Vulnerability (2007)
5. Swedish National Audit Office (2007), in: Swedish Commission on Climate and Vulnerability (2007)
6. SMHI (2001), in: Swedish Commission on Climate and Vulnerability (2007)
7. Ministry of the Environment (2009)
8. Kundzewicz (2009)
9. Hu et al. (2018)
10. Freistetter et al. (2022)
11. Several sources in: Freistetter et al. (2022)
12. Streletskiy et al. (2023)