Plewe, Bethany L. 2007. Comparison of Qualitative and Quantitative Measurement of Cobble Embeddedness in Puget Sound Streams. M.S.
Read the full thesis here. (5.54 MB pdf)
The condition of stream substrate, both in rural and urban areas, is extremely important to the survival of salmonids. As fine sediment levels in stream substrate increase, water flow and dissolved oxygen levels decrease thus threatening the survival of salmonids and other aquatic life such as benthic macroinvertebrates. There are many methods for analyzing stream or river habitat conditions that have been developed by federal, state, and private agencies, especially streambed conditions such as cobble embeddedness. Currently there are many methods employed that claim to qualitatively or quantitatively determine cobble embeddedness. This study examined the most prevalent methods employed by government and non-government agencies to analyze fine sediment levels in streambed riffles (i.e., Wolman pebble count, Burns-Skille-King hoop method, Platts/Bain visual estimation, and McNeil core sampler). In addition this study modified and tested a new quantitative method to relate to embeddedness (i.e., a dynamic sediment penetrometer). The Burns-Skille-King (BSK) hoop method, which measures cobble embeddedness directly, was not strongly correlated (r < 0.35) with any of the other methods with the exception of the weighted average BSK calculation. The penetrometer was better correlated to most of the methods (r > 0.40). The McNeil core sampler had the highest correlation (r) values with all of the methods. Through the statistical comparison of these methods using Spearman correlations, it was concluded that the best methods to use for gauging the level of cobble embeddedness or fine sediment percentages are the Platts/Bain visual and McNeil core sampler methods. The Platts/Bain visual method is the most economical because it consumes the least amount of time, which is a deciding factor for selecting methods in many projects.