Morphological response to climate-induced flood event variability in a sub-arctic river

Abstract. This study examined the effects of climate-induced flood event variability and peak sequencing on the morphological response of a sub-arctic river. We classified 32 years of discharge hydrographs of a sub-arctic river in terms of their flood event shape variability and peak sequencing, and linked them to seasonal and annual climate conditions. We utilised morphodynamic modelling to examine the effects of the flood characteristics on the morphological response of the river. The findings highlight the critical role that discharge hydrograph shape and sequencing plays in shaping river morphology and sediment transport dynamics. The increasing frequency of double-peaking floods, associated with higher geomorphic activity and sediment loads due to rising temperature and precipitation amount, points to alterations in the morphological response of the river channel. This suggests a gradual change in long-term morphological adjustment and potentially a gradual shift in sediment transport regime in the future. These shifts could have long-term implications for river stability, sediment connectivity, and ecosystem dynamics. Even in regions where hydroclimatic changes are not yet fully visible, the flood event characteristics can be evolving and re-shaping the morphodynamics of the river channel. The study underscores the importance of catchment-scale assessments and future research into the combined effects of flood sequencing, sediment transport, and changing hydroclimatic conditions.