Wood export varies among decadal, annual, seasonal, and daily scale hydrologic regimes in a large, Mediterranean climate, mountain river watershed

• Three episodic flood events produced ~ 50% of wood export over a 30-year period.
• Annual peak discharge explained 79% of variance in interannual wood export.
• Video monitoring revealed wood transport at 15% bankfull flow during snowmelt diurnal hydrographs.
• Conceptual model and framework explain linkages between climate, hydrology, and wood processes in a large, Mediterranean climate, mountain river watershed.

The dynamics that move wood through and out of watersheds are complex and not yet fully understood. In this study, climatic conditions, hydrologic responses, and watershed processes were explored to better understand variations in wood export using aerial imagery, event-based video monitoring, and field measurements from the 1097 km2 mountainous Mediterranean climate North Yuba River, California, watershed and its reservoir near the downstream outlet. Over a 30-year study period, 198\5–2014, volumetric estimates of annual wood export into the reservoir, available for a subset of years, were used to investigate watershed-scale wood export dynamics. Variations in annual peak discharge explained 79% of the variance in interannual wood export, with 84% of total observed wood export (ca. > 10,000 m3 of wood per event) delivered by three discharge events of 19-year, 21.5-year, and 60-year flood recurrence intervals. Continuous video monitoring conducted during snowmelt season periods in 2010 and 2011 yielded wood discharge observations at minima 15% of statistical bankfull flow, while maximum daily discharge explained 55% of observed daily wood piece variation. No statistically significant wood discharge differences were found in snowmelt season observations, likely because of domination of the hydrograph by diurnal pulses within the seasonal cycle. A conceptual model and functional framework are introduced in support of a watershed-scale explanation of wood export, transport, and storage processes applicable to large, Mediterranean-climate, mountain watershed settings.