Characterizing deposited sediment for stream habitat assessment

Abstract

Numerous techniques are used to measure deposited sediment and quantify substrate quality in streams. We evaluated the relationship between land disturbance and stream habitat by comparing 25 commonly used deposited sediment parameters to watershed, riparian, and local‐scale drivers. We also tested whether land use regressions were improved by accounting for geomorphic setting (measures of slope and channel incision) and how visual versus measurement‐based estimations of percent fines and embeddedness were related to each other and to percent agriculture. Of the 16 metrics significantly related to watershed agriculture, subsurface percent fines was the best indicator of land use. Subsurface fines were more strongly related to both watershed and riparian percent agriculture than surface sediment metrics. The second best‐performing parameter was the visual assessment of percent fines <2 mm. Surface particle counts also performed moderately well. Sediment percentiles (d50, d84) and stability indices were among the weakest indicators of watershed land use. All measures of local percent agriculture were poor predictors of deposited sediment parameters. Mean slope within the entire stream network was nearly as good of a predictor of deposited sediment as watershed percent agriculture. This suggests that we may improve our ability to predict deposited sediment by considering land use within the appropriate geomorphic context.