Rapid geomorphic adjustment to anthropogenic vegetation removal and meander cutoffs: Evidence from a lowland meandering river

Human interventions, such as vegetation removal and engineering structures, can significantly alter river dynamics, often increasing erosion and flood risk. While many studies have examined the role of vegetation, flood regimes, and channel geometry in river morphodynamics, long-term, reach-scale analyses of channel response to abrupt riparian vegetation removal remain scarce. This study examines channel changes in the meandering Orljava River, Croatia, over the past 55 years, focusing on its response to floods before and after anthropogenic removal of riparian vegetation in 2011. Channel morphometric parameters were measured using aerial images, orthophotos, and topographic maps. To assess factors influencing lateral migration rates, data on flood magnitude, duration, riparian vegetation, and channel geometry were analysed using linear mixed models. The results showed a fourfold increase in migration rates and a 40 % increase in channel width after vegetation removal. Statistical analysis revealed that migration rates were negatively related to riparian vegetation cover and positively related to the duration of geomorphically effective discharges, channel slope, and width. The most geomorphically dynamic sections were located downstream of mill weirs and artificial meander cutoffs, which locally modify channel slope and increase stream power. These findings suggest that human interventions have been the primary drivers of intense bank erosion, channel migration, and agricultural land loss. To mitigate lateral erosion and flood risks in actively meandering rivers like the Orljava, restoring riparian vegetation is crucial for stabilizing riverbanks. Additionally, preserving natural sinuosity can enhance geomorphological diversity and improve channel stability by reducing slope and stream power.