Cold-region rivers, many of which are seasonally ice covered, are undergoing rapid hydroclimatic change as rising air temperatures alter precipitation phase, snow accumulation, freeze–thaw cycles, and river-ice regimes. These changes modify discharge seasonality and flow and sediment processes that have traditionally been dominated by spring snowmelt and stable winter ice cover. Despite their importance, flow conditions and sediment transport beneath river ice remain poorly understood, particularly in natural rivers. This thesis examines climate-change-driven alterations in cold-region river systems by integrating watershed-scale analyses of long-term discharge records with reach-scale field observations of under-ice flow and sediment processes. It is based on two long-term time series and applies three complementary approaches: (1) statistical analyses of multi-decadal discharge records from unregulated Finnish rivers, (2) multi-year in situ measurements of near-bed flow and sediment transport beneath ice cover in a subarctic meander bend, and (3) near-bed turbulence analyses to assess hydraulic controls on ice-covered flow processes. Results show that climate change is redistributing river discharge within the hydrological year across Finland. Spring flood peaks are occurring earlier, while winter and autumn flows are increasing, whereas annual total discharges remain largely unchanged. Reach-scale observations demonstrate that the ice-covered period is morphodynamically active, even during the lowest midwinter discharges, with sediment transport occurring year-round. Turbulence analyses reveal that water-column height beneath the ice is the primary regulator of near-bed turbulence and shear stress, with ice thickness, discharge, and channel morphology further modulating bedload transport. Overall, wintertime processes play a key role in cold region sediment dynamics. As warming continues, flow and sediment transport are likely to become less concentrated during spring floods and increasingly distributed across winter and autumn events. The impacts of their changes must be considered when assessing the effects of climate change in cold-region rivers.