River channel stability and the implications for fish habitat

The purpose of this project was to investigate various aspects of river channel stability as they relate to fish habitat. Two headwater creeks of the Credit River system, Black and Silver Creeks, and their confluent stream, the West Credit River in Southern Ontario were used in the study. Thirty-five cross-sections were established and revisited during four flow regimes, summer base flow, fall secondary peak flow, spring melt-high flow and post-spring high flow. Measurements of width, depth and temperature were taken at these times. Water samples were taken for determination of suspended sediment concentration. Channel stability was investigated in relation to three major factors: stability of the fluid, stability of the bed, and stability of the banks. Fluid stability measurements involved measuring fluid speeds vertically and laterally through each cross-section under the four flow regimes. Individual experiments at the confluence area were conducted because of some of the earlier results from other sections of creek. Information on the rates of change of discharge were determined from secondary data provided by the Water Survey of Canada. Bed stability was measured by looking at bed material particle size distribution, cross-sectional channel profiles and control reach topographical surveys which included particle marking and tracking. Bedload transport rates at the confluence area were determined under varying flow conditions. Bank stability was investigated by the use of a piece of equipment developed for this thesis, the River Bank Profiler. Volumetric changes to banks consisting of cohesive as well as cohesionless material are presented for comparative purposes. As changes in river channel stability can have a direct impact on resident fish, investigation of the biological literature was used as a framework for the geomorphological work. It became apparent that there is a direct application of fluvial geomorphology in that biologists are stating a direct need for more geomorphological work in the area of fish habitats. A conceptual framework showing the relationship between properties of fluid, bed and bank stability and the degree of interconnectedness is presented to aid both the geomorphologist and the biologist when looking at aspects of fish habitat from a geomorphological perspective