Unravelling the frequency and magnitude of large wood mobility and transport distance across 11 low-order streams over multiple years

Large wood (LW) entrainment and transport observations of naturally occurring wood in rivers are critical for understanding wood dynamics. However, they remain limited and sparse, primarily originating from single-site studies. As a result, broader spatial or temporal variability of wood dynamics may not be adequately captured. We compiled a database of tracked, natural pieces of wood from 11 low-order and relatively steep streams in the Chilean Andes, Swiss Alps, United Kingdom and United States. From decades to single-year studies, we gathered 59,739 observations of tracked wood, which all include at least a recorded length and transport distance. River characteristics varied according to channel width, less than 5 m to wider than 15?m, and gradient, between 0.04?m/m. The meta-analysis enabled us to calculate probabilities and identify general patterns. Wood mobilization varied significantly interannually, reflecting the complex interplay between flood events and wood storage. Overall, a small proportion of tagged wood moved during study periods, primarily during events associated with return periods exceeding 10 years. Most mobile pieces travelled less than 1 km, and longer distances had relatively low probabilities, typically occurring during high-magnitude flood events associated with return periods over 10 years. Results showed that large wood mobility in rivers is generally infrequent and highly variable, influenced by a combination of wood characteristics, river size and flood magnitude. Understanding variability can help inform risk-based flood hazard planning, river management and river restoration projects implementing large wood. Future studies should expand upon the current dataset.
Keywords: displacement distance; entrainment; initial conditions; instream wood; mobility by wood flux