| Abstract/Description or Keywords |
In May 2011 the Ministry of Forest, Lands and Natural Resource Operations placed substrate in two locations in the Nechako River at Vanderhoof, BC to improve the availability of clean coarse gravelcobble substrate that White Sturgeon can use to spawn. The substrate is intended to provide interstitial spaces that sturgeon eggs can fall between and larvae can hide in, thereby reducing predation (McAdam et al., 2005). If the interstitial spaces become filled with fine sediment the effectiveness of the substrate is reduced. In 2011 and 2012 substrate assessments were completed to assess the condition of the placed substrate (NHC, 2012, 2013a). During these assessments it was observed that the inside corner of the placed substrate patches was more prone to infilling with gravel and coarse sand than the outside portion of the pads. It was also observed in 2012 that coarse sand was mobile at the Burrard Street Bridge despite relatively low flows. These observations, and other information was subsequently compiled and reviewed as part of a Geomorphology Charette held on February 28th, 2013 in Vancouver BC. An outcome of the Charette was the identification of a series of important research questions to guide future studies (NHC, 2013b). This report and the associated field studies are intended to partially address some of these research questions. In particular: 1. The pattern of sediment transport past the placed substrate was investigated to determine if sediment was overpassing and being flushed out of the interstitial spaces, or if the areas that were remaining clear were not exposed to the mobile bedload. 2. Methods of measuring and assessing sediment transport through the Vanderhoof reach were evaluated and a first order assessment of sediment transport rates at a low and high flow were completed. During the October, 2013 fieldwork underwater images were also used to assess the substrate condition at the two patches (Figure 1). The work was completed with support from Ministry of Forests, Lands and Natural Resource Operations personnel. Boat and driver support was supplied by John Summers. |
