NWT RESEARCH DATABASE

Regions: Dehcho Region, South Slave Region

Tags: physical sciences, wood transport, river current, driftwood

Objective(s): To examine the sources of wood within the Mackenzie River drainage, transport of wood toward the Arctic Ocean, and the potential implications of global warming for wood recruitment and transport.

Project Description: The research team propose to examine the sources of wood within the Mackenzie River drainage, transport of wood toward the Arctic Ocean, and the potential implications of global warming for wood recruitment and transport. The primary objectives are to (i) evaluate fundamental controls on wood dynamics within the Mackenzie and (ii) develop an empirical predictive model to estimate future wood dynamics. The teams conceptual model of the Mackenzie drainage basin includes three primary regions of wood recruitment, multiple transport and storage zones, and measurement sites near stream discharge gages. This study will include three parts over three field seasons: (i) wood transport and storage along the drainage network, (ii) wood recruitment from banks and hillslopes and (iii) wood transport and storage through the delta. The research team hypothesize that wood is transported above a threshold flow depth and discharge. The team will examine 37 years of repeat aerial photographs at the rapids through Parks Canada and the Pelican Advisory Circle. These photographs have been taken twice a year since 1975 and individual logs are clearly visible. The team will use GIS to analyze changes in wood volume through time, and relate these changes to discharge at the Slave River Fitzgerald gage (1921-present). The team will collect field data on the vertical structure, composition and density of logjams where these are present, and measure flow depth and channel geometry around jams. These data will be used with hydraulic models to determine potential flow thresholds for wood transport. A permanent time lapse camera will be set up near the gage to enable the team to generate wood discharge curves and estimate wood volumes during floods. During the 2012-2013 academic year, the research team will analyze remote imagery at adequate resolution and time intervals to quantify changes in wood storage within Great Slave Lake, and along transport limited reaches near the mouth of the Liard and Hay rivers. The research team will use high resolution remote imagery at 5 yr intervals to discern landslides and bank failures along the drainage network. Landslides and bank failures were easily discernable during a preliminary analysis of existing photography. The team hypothesize that wood recruitment is dominated by landslides and debris flows in areas of high topographic relief and by bank erosion in areas of low relief. The research team also hypothesizes that, for uncohesive banks, wood recruitment will be higher in the southern portions of the drainages beyond the extent of continuous permafrost. Forest type and permafrost are already mapped throughout the region. Size of individual trees and spatial density of forest stands can be assumed based on forest type, allowing them to estimate wood recruitment from landslides using remote imagery. Once the research team quantitatively estimate wood inputs, outputs, and storage within the major components of the Mackenzie drainage, components of the total wood budget that are likely to be most sensitive to changing climate can be identified, as expressed through changes in permafrost extent, forest type, and river dynamics (flow regime, bank erosion). The research team can also identify the likely direction of change in these components associated with warming climate (e.g., greater wood recruitment through accelerated bank erosion). Existing simulations of changes in discharge in response to warming, facilitate the teams ability to evaluate changing scenarios of wood dynamics. The research team will be providing local opportunities for (i) Environment Resources and Technology Program (ERTP) students at Aurora College to assist with field work (ii) the team will conduct community outreach by giving community and educational talks, and include local groups in fieldwork and keep them informed of results. The research team will inform the results of this study to communities via local journalism, community talks, educational talks, direct communication with local groups and agencies, peer reviewed journal publication, and conferences (both Northern and international). The fieldwork for this study will be conducted from April 1, 2014 to September 1, 2014.