Karlstad is a medium-sized Swedish municipality with a population of approximately 88,000 inhabitants. The city of Karlstad is located on a river delta, where the river Klarälven flows into Lake Vänern. The delta area is continuously affected by processes of erosion and sedimentation.
The municipality can be flooded both by the river and by the lake. The highest flows usually occur during spring in connection to snow melting and/or ice plugs, and during fall, as a result of frequent or intense rains. While high flows in Klarälven may occur rapidly and last for relatively limited time, high flows in Lake Vänern occur more slowly and may last for months. The landscape around the river is relatively flat which means that floods can result from heavy rains. Finally, in the event of a dam failure in Klarälven, the water would reach Karlstad approximately 26 hours after, and affect about 23 000 residents. The return period of such an event is more than 10 000 years. Flood risks in Karlstad are higher than in many other municipalities in Sweden and climate change is expected to increase these risks.
Karlstad is one of areas with significant flood risk identified in the first step of the implementation of EU Floods Directive. The most vulnerable social functions in the municipality in case of floods are the water and sewerage system, the hospital, telecommunications, the railways and parts of the electrical power supply. All of these are affected in their functions at relatively low water levels. Figure 1 illustrates Karlstad at a so-called 100 year flood (red areas are flooded). According to the municipality’s flood management program a 100 year flood would imply costs of 10,5 billion SEK and about 25 000 people would have their homes flooded.
Karlstad municipality works actively to reduce flood risk. Most notable is the above mentioned local flood management program from 2010 for Karlstad, where a common approach to flood risks is taken. The overall aim of the program is to establish how the municipality is to work in order to face present and future flood risks. This will be achieved by:
- Building up knowledge about the effect of different water levels on various social services.
- Working to prevent flooding through technical adaptation measures.
- Preparing organizationally and operationally to minimize the consequences of floods.
- Planning Karlstad’s continued expansion on the basis of an informed risk assessment.
- Together with other actors, working on increasing drainage of Lake Vänern.
- Disseminating knowledge and information to help property owners and operators reduce the risks in their respective areas.
The program also emphasises the need for organizational coordination and well-functioning cooperation. The municipality even has a flood risk manager who is responsible for coordinating the work with flood risk within the municipal departments and for annually following up and reporting on the progress made with the implementation of the program.