Data description: Surface flow velocity dataset was created using Hydro-STIV software (Hydro-STIV v.1.2.2, Hydro Technology Institute co.), which uses Space-Time Image Velocimetry (STIV) for velocity estimation, a method derived from Large-Scale Particle Image Velocimetry (LSPIV) developed by Fujita in 2007 (Fujita et al., 2007). The videos were georeferenced using known GCPs and the software performed orthorectification and calibration. The data has been used for publication "Surface flow and ice rafting velocities during freezing and thawing periods in Nordic rivers". Data consists of videos and daily stil images from Pulmanki, Koita and Sävar Rivers from Autumn freezing and Spring thawing periods. The data from Koita River is from 2020-2021 and from Pulmanki and Sävar Rivers from 2021-2022. The original raw data based on which the STIV analysis was performed was collected with Burrel time-lapse RGB cameras. Acknowledgements: The river-ice related measurements were initiated at Pulmankijoki River in 2014 under the post-doctoral research project of Dr Lotsari, funded by the Research Council of Finland (ExRIVER: grant number 267345), and this study is a continuum in the series of these winter season studies. The work for this study was financially supported by four other projects funded by the Research Council of Finland (DefrostingRivers: 338480; HYDRO-RDI-Network: 337394; Digital Waters [DIWA] Flagship;359248). In addition, the work was funded by The European Union – NextGenerationEU Recovery instrument (RRF) through Research Council of Finland projects Hydro RI Platform (346167) and Green-Digi-Basin (347703). The Department of Geographical and Historical Studies, University of Eastern Finland, supported financially the field work done at Koita River. The work by Dr Lina Polvi-Sjöberg at the Sävar River was financed by a grant (2023-01513) from the Swedish Research Council Formas.

2024