Image above: Alatna River and Malamute Fork Confluence.
Photo Credit: Erica Lamb.
This presentation will provide an overview of suspended sediment transport in the Koyukuk, Alatna and Reed Rivers on the south side of the Brooks Range in Arctic Alaska. Methods used included depth-integrated suspended sediment samples, grab samples, automatic pump-style samplers, discharge measurements, bed sediment grain size analysis and a variety of meteorological measurements. With slightly less than three years of data collected from July 2012 to September 2014, an initial analysis of suspended sediment transport was completed. Suspended sediment rating curves were developed, revealing a strong correlation between suspended sediment concentration (SSC) and discharge. In addition, suspended sediment discharge and annual yields were calculated, showing a large percentage of transport occurs during spring melt on these rivers. Turbidity was also analyzed.
In addition, confluence dynamics were examined; the confluence of two streams clearly modifies the hydraulic and sedimentologic flow conditions present, and there has been relatively little research done on this in arctic regions. If the difference in streams’ sediment load and water temperature (upstream of the confluence) are significant, the formation of a well-defined interface within the confluence area is possible. Downstream of the confluence, the mixing processes are significant and eventually the interface disappears. Preliminary results will be discussed of a study focused on the hydro-sedimentological conditions of the Alatna River and Malamute Fork confluence. This work examines the spatio-temporal evolution of water temperature and suspended sediment concentration in the confluence zone. Magnitude of vorticity is also reported along river transects.