The vulnerability of road network and transport routes to climate change impacts depends on the actual state and level of response of road pavements. The most important impacts are considered in the design and construction practice, e.g. frost action, storm rain drainage, etc.
Vulnerability to climate-induced impacts
Recent experience has shown that our current preparedness for extreme climatic events is insufficient. Examples of recent extreme events in Finland include
- Storm rain flooding in central and western Finland in summer 2004
- Sea level rise along the south coast in winter 2005
- Floods due to rains and snowmelt in northern Lapland in spring 2005
The immediate costs of damage to the road network were considerable, up to €1.6 million. This does not include costs incurred by restraints on traffic and transport or the weakening of pavements causing increases in maintenance and repair.
Climate change scenarios for Finland
The climate is expected to become warmer due to increased greenhouse gases in the atmosphere. By 2080, the annual mean air temperature is expected rise by 3–5°C above the average for the period 1871–2000. Rising winter temperatures might increase the need for salting, and shorten the length of the salting period. The character of events needing friction control measures (salting) varies between regions from south to north
and east to west, and the change in friction control will be regional. Annual precipitation is anticipated to increase above the average for 1971–2000 by ten per cent by 2050, and by |
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12–17 per cent by 2080. Maximum six-hour and five-day rain figures would increase by 25 per cent on average, and in some regions by more than 50 per cent. This increases especially the risk of urban flooding and the flood risk in artificial water basins. Water levels in the world’s oceans and in the Baltic Sea are estimated to rise significantly. At the same time, land heaving along the coastline will mainly compensate for the rise of the Baltic Sea. Floods rise when there is a strong low pressure and prolonged heavy winds. Increasing winter rains together with rising air temperatures may exacerbate the distress of freeze-thaw on pavement surfaces and structures.
Climate change and road management in Finland
As winters get warmer, frost penetration in pavements will decrease significantly. Thaw weakening may start earlier in the spring, and develop also during the frost period, causing a shortened period for winter transport which presently benefits from higher bearing capacity of frozen road structure.
Snowfalls are increasing in the north, while winters are getting milder. Although the amount of snowfall and snow cover is likely to decrease, the intensity of shortterm snowfalls disturbing traffic may rise. An increase in repeated freeze-thaw cycling may also exacerbate the frost deterioration of pavement surfaces and structures. In future, the need for raising pavement surface levels and reviewing the design of drainage facilities for flood events should be evaluated in the repair design. A greater intensity of storm rains causes increased watercourse flooding and consequent damage. Rising water on the pavement may block traffic and cause damage to road equipment, and softens the pavement structure with increased risk of damage and shortened lifetime. Storm rains may also worsen damage caused by erosion |
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to side ditches and slopes and at cones of bridge abutments and embankments increasing e.g. the landslide risk and amount of silting.
Preparation for climate change
The type of preparation will differ depending on the purpose:
- Emergency, rescue
- Protection of activities, prevention or limitation of damage, maintenance of service levels
- Improvement of durability of structures and equipment
- Change of building regulations and codes of practice.
Knowing the character and impact processes of an expected weather event is necessary for preparation. Besides the projected change of climatic factors, the response of pavements and the road network to exceptional climatic impacts must be understood. For this, documented and analysed information is needed on climateoriginated damage such as floods, storm rains, snow, ice, etc. This means more reliable information than is currently available on road conditions and service levels in real time, as well as more precise design and planning that take climatic impacts into account.
Seppo Saarelainen, VTT, Finland
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