Interannual spatial distribution and dynamics of large wood in a meandering river

Abstract

Meandering rivers are widespread fluvial systems, yet surprisingly little is known about the quantity and spatiotemporal patterns of large wood (LW; pieces of dead wood ≥ 1 m long with ≥ 0.1 m in diameter) storage in these environments. This study aims to evaluate the interannual storage and dynamics of LW from 2016 to 2024, focusing on 13 meander bends within a 4 km actively meandering reach of the Odra River in Czechia. Data were collected using a multifaceted approach, including field inventories, drone imagery, and time-lapse cameras. Significant variations in LW counts (179–287) and volumes (7.91–9.82 m³/ha) were observed over the 8-year period, which were not directly related to flow variations alone, indicating that river morphodynamics and other disturbances influencing LW recruitment must also be considered. The presence of woody vegetation at the outer meander bank was a significant predictor of average LW volume at the bend scale. Despite the occurrence of a flow close to the 1-year recurrence interval, many LW pieces three to four times shorter than the channel width remained stable, resulting in a 50 % mobility rate during a closely monitored year. This flow, however, transported a significantly larger quantity of LW compared to the total inventoried LW in the entire study reach, suggesting intensive LW recruitment even during frequent low-magnitude events. LW length was an important predictor of mobility, while factors such as incorporation into jams, complex shapes with preserved branches (indicating freshly recruited wood), and initial channel position (with jammed LW in the middle of the channel being more frequently mobilized) also played roles. Understanding the interaction between vegetation, channel morphology, and LW dynamics can inform strategies to enhance habitat complexity and improve floodplain connectivity, while also providing valuable guidelines for assessing potential LW mobility during floods.