Investigating Ice-Impacted Fluvial Processes in a Small Riffle-Pool Sequence in Southern Ontario
Understanding fluvial processes impacted by ice is essential to supporting channel design and stream corridor work in cold region rivers. Challenges with winter fieldwork limit field studies of fluvial processes in ice-covered riffle-pool sequences. Field and modelling approaches were used to investigate the impacts of ice cover on velocity and shear stress in a small, shallow riffle-pool sequence in Southern Ontario, Canada. Changes in flow direction, maximum velocity depth and magnitude were evaluated and shown to vary between smooth and rough cross-sections. Shear stress under ice was influenced by maximum velocity depth and magnitude within the riffle and pool. Fieldwork and modelling both demonstrated changes in shear stress distribution throughout the riffle-pool. Cross sections with higher roughness demonstrated increases in shear stress under ice, while cross-sections with lower roughness exhibited overall decreases in shear stress. Modelling paired with field data provided detailed shear stress magnitude and distribution estimates under ice.