Spatially averaged velocity distributions, turbulence characteristics, and stream bed roughness elevations were collected in two streams with rough-bed substrate. Variogram analysis of substrate roughness height yielded characteristic length scales of the stream bed over which bed elevations were correlated from 0. 14 to 0. 41 m. Temporally and spatially averaged (double-averaged) vertical velocity profiles followed a composite distribution consisting of a linear distribution below the roughness crest height and a power or wake law above the crest. Our double-averaged velocity data demonstrated the applicability of both the wake law and power law to open-channel flow for which a low ratio of flow depth to roughness height does not support the development of the universal logarithmic velocity law. A power-law scaling relationship among spatially averaged Glossosoma density, stream bed roughness characteristics, and double-averaged fluid flow conditions was developed. The density of Glossosoma scaled directly with substrate crest elevation, normalized spatial fluctuation of longitudinal velocity in the proximity of the bed, and inversely with the standard deviation of the crest elevation. The proposed dimensionless scaling relationship explains 84 % of the Glossosoma variability.
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Acknowledgements This work was supported by the National Science Foundation under grant IGERT: Nonequilibrium Dynamics Across Space and Time: A Common Approach for Engineers, Earth Scientists, and Ecologists (Grant Number DGE-0504195), as well as the National Center for Earth-surface Dynamics (NCED), a Science and Technology Center funded by the office of Integrative Activities of the National Science Foundation (under Agreement Number EAR-0120914). We thank the University of California Natural Reserve System and the Steel family for providing access to streams in the Angelo Coast Range Reserve, and the Belwin
- Dimensional analysis
- Ecological hydrodynamics