NWT RESEARCH DATABASE

Tags: physical sciences, prediction models, wood transport, 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 proposes 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 team’s 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 (Figure 1). 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 hill slopes and (iii) wood transport and storage through the delta. The team hypothesizes 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 Geographic Information Systems (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 and the team will 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 year intervals to discern landslides and bank failures along the drainage network. Landslides and bank failures were easily discernible during a preliminary analysis of existing photography. The team hypothesizes 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 will be providing opportunities for: (i) Environment and Natural Resources Technology Program (ENRTP) students at Aurora College to assist with field work, GIS and remote imagery analysis (ii) summer interns at Parks Canada to digitize past analog photography and conduct community outreach, and (iii) local band members, who will be kept informed of the project and will be given the opportunity to participate as the need arises. Studying the wood flux through the Slave will provide baseline environmental data that should be considered in future environmental assessments for large hydroelectric projects in the region. The research team will communicate information on this study through the Slave River Journal (and other local papers), Northern radio interviews, Through Parks Canada Community Outreach. The fieldwork for this study will be conducted from June 27, 2012 to November 1, 2012.