The pulse of driftwood export from a very large forested river basin over multiple time scales, Slave River, Canada

• Published in: Water resources research 2017-03, Vol.53 (3), p.1928-1947
• Main Authors: Kramer, Natalie, Wohl, Ellen, Hess‐Homeier, Brooke, Leisz, Stephen
• Format: Article
• Language: English
• Subjects: Aquatic ecosystems; Case studies; Catchment area; Catchments; Dams; Deforestation; Depletion; Discharge; Disturbances; Driftwood; Ecosystems; Essential nutrients; Exports; Floating; Floods; Fluctuations; Fluxes; Freshwater; great river; Historic artifacts; History; Ice; Imagery; instream wood; Lakes; Land use; Landscape; Marine ecosystems; Marine environment; Mats; Migration; Migrations; Mineral nutrients; Monitoring; Nutrients; Recruitment; Recruitment (fisheries); River basins; Rivers; Sequencing; Slave River; Slumping; Storage; Time; Transport; Wood; wood flux
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1002/2016WR019260

This study presents a case study of large wood transport on the great Slave River in northern Canada with the objective to better understand the processes of and variability in pulsed wood fluxes from large forested catchments. We use a varied approach, integrating field characterization of wood, historical anecdotes, repeat aerial imagery of stored wood, and time‐lapse imagery of moving wood, for a robust analysis and synthesis of processes behind pulsed wood flux, from yearly uncongested export to rare congested wood floods. Repeat monitoring of known sites of temporary storage with new or historic imagery proved to be a very useful tool for constraining wood flux histories. Pulsed wood export on the Slave River is not an artifact of episodic recruitment from major up‐basin disturbances, but rather reflects decadal‐ to half‐century‐scale discharge patterns that redistribute wood recruited from channel migration and bank slumping. We suggest that the multiyear flow history is of paramount importance for estimating wood flux magnitude, followed in declining importance by the yearly sequence of peaks and the magnitude and characteristics of the rising limb of individual floods. Plain Language Summary Driftwood is an important element of landscapes and ecosystems because it provides essential nutrients and habitat in many water environments. This work describes how driftwood is transported through really big rivers at multiple time scales from days to decades to a half century. We characterize large driftwood floods, which are events of massive floating mats of driftwood, as well as transport of wood within ice from a relatively pristine forested river basin. Describing driftwood transport in a mostly unaltered basin, such as the Slave River, helps scientists understand the impact of driftwood depletion on river, lake, and ocean ecosystems from human land use practices, such as dams and deforestation. Key Points Wood flux is strongly influenced by the shape and patterns of water discharge at varying time scales Flow history is the most important variable for prediction of the magnitude of wood flux Repeat monitoring of temporary storage with new or historic imagery is a very useful tool for constraining wood flux histories