In Finland, spring has typically been a time of flooding, when the thick snow cover melts at a rapid pace or spring rains fall during the ground frost period. Flooding usually takes place especially in Lapland, Northern Ostrobothnia and Kainuu. The changing climate has now started to affect floods and their timing. Last winter was unusually varied in Northern Finland and Lapland.
‘Due to mild winters with little snow, spring floods take place earlier and are less powerful. In contrast, flooding in other seasons such as winter has increased along with heavier rain,’ says Linnea Blåfield, Doctoral Researcher at the University of Turku.
Blåfield has studied long-term changes in the rivers Oulankajoki and Pulmankijoki in the north and has seen particularly distinctive changes in Oulankajoki.
‘In Oulanka, the mean annual temperature has risen by more than three degrees in 50 years, as much as seven degrees in December. This affects not only the timing of floods but also the transfer of nutrients and pollutants in water,’ she says.
Digital modelling helps predict the impact of floods
River environments are affected by the changing climate. Researchers are now collecting accurate data on Finland’s rivers to better understand the impact of extreme weather conditions. In the measurements, an elevation model covering the riverbed and catchment area is prepared to help detect erosion and changes after a flood, for example. The movement of sediments, the speed and direction of the water flow, and changes in the riverbed are also measured.
New research data helps build a digital twin to model all the factors that affect waterbodies and all the ongoing changes. Research data can be used to predict the behaviour of rivers in extreme situations, including unexpected heavy rainfall.
‘An accurate three-dimensional model of the riverbed and any changes in it helps understand how floods and the changing snow and ice conditions shape aquatic environments, and what kinds of risks this may pose to both the unbuilt and built environment,’ says Harri Kaartinen, Research Professor at the Finnish Geospatial Research Institute (FGI).
Measurements have been conducted using unique mobile research equipment in the rivers Vantaanjoki, Oulankajoki and Tana, as well as its tributary Pulmankijoki. The measurements have been conducted by the Finnish Geospatial Research Institute (FGI) of the National Land Survey of Finland (NLS), the University of Turku, Aalto University, the Finnish Environment Institute and the University of Oulu.
Further information
• Harri Kaartinen, Research Professor, Finnish Geospatial Research Institute of the National Land Survey of Finland, +35829 531 4756, firstname.lastname@nls.fi
• Linnea Blåfield, Doctoral Researcher, University of Turku, +35850 540 0912 linnea.m.blafield@utu.fi
The study has been conducted as part of the Digital Waters (DIWA) flagship funded by the Research Council of Finland, the Freshwater Competence Centre funded by the Research Council of Finland and the NextGenerationEU RRF programme, as well as the Green-Digi-Bas and Hydro-RI-Platform projects.