Flow Characteristics in Small Northern Streams and Nature-like Fishpasses

Abstract

Increasingly, human activities for the societal development and quality of life can alter, disrupt or destroy aquatic habitat with varying degrees. The rising awareness and concern regarding such type of human activities on stream and riverine ecosystem have resulted in a movement towards habitat compensation to achieve no net loss in productive capacity of fish habitat. As part of a fish habitat compensation project, this thesis investigated detailed flow characteristics in small northern streams and in rock-ramp type nature-like fishpasses through field, laboratory, and numerical studies. The principal motivation for this study is to advance our understanding of flow characteristics in a rock-ramp fishpass to retrofit small streams for fish habitat connectivity and compensation. First, the flow characteristics of a headwater stream as a fish migration corridor and the hydraulic characteristics of several headwater streams in the Northwest Territories of Canada were investigated. The analysis of stream hydrological or hydraulic flow characteristics demonstrated that some sections of the study stream for certain durations of the study period appeared to naturally provide suitable habitat for select stages of YOY (young-of-the-year) Arctic grayling, while other sections would require certain modifications and additional outlet flow arrangements. The study of hydraulic characteristics explored the nature of at-a-station hydraulic geometry and flow resistance in an unstudied geographic region of the Northwest Territories of Canada for the future habitat assessment and predictions. Next, detailed mean and turbulence flow characteristics generated by a staggered arrangement of boulders in a rock-ramp nature-like fishpass were investigated experimentally. The results showed that this type of fishpass can produce adequate water depth and favorable flow velocity, turbulent intensity, and turbulent kinetic energy for suitable fish passage. Some general correlations were developed for predicting the mean and turbulence flow parameters in a rock-ramp fishpass as a function of normalized discharge and streamwise distance. Moreover, a flow resistance analysis based on basic concepts for wake-interference flow regime in this fishpass has resulted in a general equation for the average velocity. Finally, a three-dimensional Computational Fluid Dynamics (CFD) solver was used to investigate the flow characteristics in a rock-ramp nature-like fishpass under different flow conditions and geometric variables. The model was validated with experimental data and a good agreement was achieved. The findings emanating from this numerical study optimized the design of rock-ramp fishpasses.