Four decades of Baksan River Channel adjustment in the context of climatic and hydrological change

River basins draining the mid- and high-mountain belts of the North Caucasus, exemplified by the Baksan River, are prone to periodic debris floods in their headwaters. These events deliver substantial volumes of clastic sediment to main valleys, driving significant channel transformations downstream. The catastrophic flood generated by the September 1, 2017 outburst of Bashkara Glacial Lake in the Adyl-Su valley provided a pivotal opportunity to assess such impacts on the receiving Baksan River. In this study, morphometric changes were quantified along a middle-course reach upstream of Tyrnyauz. The analysis spans a 40-year period starting from 1984, selected in the immediate aftermath of a preceding major flood, and extends to cover conditions immediately following and six years after the 2017 event. The aim was to elucidate channel dynamics and evaluate system resilience to impulsive disturbances within the context of climatic shifts over the past four decades. Multi-temporal satellite imagery was employed to segment the river network into homogeneous reaches, with a suite of morphometric parameters subsequently derived for each segment. Controlling factors were identified through Spearman’s rank correlation analysis. The immediate geomorphic response to the 2017 flood was characterized by substantial channel widening, averaging a factor of 1.6, and a shift toward more complex planform morphologies. During the subsequent six-year period without extreme floods, divergent trajectories were observed: continued widening (averaging a factor of 1.3) was detected along 27% of the study reach, while recovery through channel narrowing (20–25%) and simplification toward straighter patterns occurred along one-third of its length. Pre-flood channel geometry was found to be a critical control. Narrower, highly confined reaches exhibited the greatest sensitivity and a meta-stable resilience at the studied timescale. In contrast, initially wider reaches located within valley constrictions not only absorbed the impulsive disturbance but were characterized by a positive recovery trajectory, underscoring the fundamental role of antecedent valley morphology in determining long-term channel response and resilience.