ABSTRACT
The spatial and temporal flow field characteristics of a gravel-bed river supporting a robust rainbow trout (Onchorhynchus mykiss) and brown trout (Salmo trutta) fishery were studied in high resolution in attempts to hydraulically quantify the selection preferences and incubation characteristics of redds. Measurements were obtained at both the riffle-and redd-scale post-spawning, in addition to pre- and post-bed mobilization flow events. A Pulse Coherent Acoustic Doppler Profiler (PCADP) was adapted for use in the lotic environment where between 4000 to 5000 three-dimensional velocity measurements could be obtained on a daily basis at the riffle scale. Bed material samples were obtained and scour chains installed to characterise the bed mobility, critical shear, and macro-erosion of each riffle studied. At the riffle-scale, seasonal variability in the mean and variance of commonly used hydrodynamic parameters (velocity, flow depth, Reynolds number, bed roughness, turbulent kinetic energy per unit area) were often explicitly related to changes in sampling discharge and channel structure.
