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- Title
Spatial characterization of roughness elements in high-gradient channels of the Fraser Experimental Forest, Colorado, USA.
- Authors
Yochum, Steven E.; Bledsoe, Brian P.; Wohl, Ellen; David, Gabrielle C. L.
- Abstract
We collected high-resolution LiDAR-based spatial and reach-average flow resistance data at a range of flows in headwater stream channels of the Fraser Experimental Forest, Colorado, USA. Using these data, we implemented a random field approach for assessing the variability of detrended bed elevations and flow depths for both the entire channel width and the thalweg-centered 50% of the channel width (to exclude bank effects). The spatial characteristics of these channels, due to bedforms, large clasts and instream wood, were compared with Darcy-Weisbach f and stream type through the use of the first four probability density function moments (mean, variance, skewness, kurtosis). The standard deviation of the bed elevations ( σz) combined with depth ( h), as relative bedform submergence ( h/σz), was well correlated with f (R2 = 0.81) for the 50% of channel width. The explained variance decreased substantially (R2 = 0.69) when accounting for the entire width, indicating lesser contribution of channel edges to flow resistance. The flow depth skew also explained a substantial amount of the variance in f (R2 = 0.78). A spectrum of channel types is evident in depth plots of skew versus kurtosis, with channel types ranging from plane bed, transitional, step pool/cascade, to cascade. These results varied when bank effects were included or excluded, although definitive patterns were observed for both analyses. Random field analyses may be valuable for developing tools for predicting flow resistance, as well as for quantifying the spectrum of morphologic change in high-gradient channel types, from plane bed through cascade.
- Subjects
FRASER Experimental Forest (Colo.); SURFACE roughness; RIVER channels; CLASTIC rocks; DARCY-Weisbach equation; PROBABILITY density function
- Publication
Water Resources Research, 2014, Vol 50, Issue 7, p6015
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1002/2014WR015587