Different climate scenarios almost unanimously predict that warming will be higher than average in the Nordic region. Climate change on the one hand poses a risk of increased flooding, whereas decreasing trends may be expected in regions where precipitation or snow accumulation decreases. Efforts have been made to assess these changes on a continental scale to produce a general overview, but the reliability of such large scale evaluations on the national scale is unknown.

A general overview of changes in flooding caused by climate change in Finland is provided for the periods 2010-2039 and 2070-2099. Changes in flooding were evaluated at 67 sites in Finland using a conceptual hydrological model and 20 climate scenarios from both global and regional climate models. Floods with a 100-year return period were estimated with frequency analysis using the Gumbel distribution. At four study sites depicting different watershed types and hydrology, the inundation areas of the 100-year floods were simulated with a 2D hydraulic model. The future climate change induced morphodynamic river channel changes were also analyzed in one study site.

The results demonstrate that the impacts of climate change are not uniform within Finland due to regional differences in climatic conditions and watershed properties. In snowmelt-flood dominated areas, annual floods decreased or remained unchanged due to decreasing snow accumulation. On the other hand, increased precipitation resulted in growing floods in major central lakes and their outflow rivers. The changes in flood inundation did not linearly follow the changes in 100-year discharges, due to varying characteristics of river channels and floodplains. The changed future discharges also caused noticeable changes in river morphology. The results highlight the importance of comprehensive climatological and hydrological knowledge and the use of several climate scenarios in estimation of climate change impacts on flooding and river morphology.