ABSTRACT
Submerged groynes (low-profile linear rock structures, also called stream barbs) were installed in a reach of Sawmill Creek in Ottawa, Canada in order to mitigate outer bank erosion in two consecutive bends. The presence of these structures has had an effect on channel bathymetry and thusly on flow structure in the area. Changes in both the flow field and bathymetry have been recorded over five years (including two years prior to implementation of the groynes) using an Acoustic Doppler Current Profiler (ADCP), and a total station, respectively. Additionally, three-dimensional flow field data were collected using Acoustic Doppler Velocimeters (ADV) near the apex of the first bend. Measurements were collected prior to implementation of the groynes as well as at the end of the study term in order to compare the long term effects on flow structure and turbulence in the area. Over the study period, it was observed that the thalweg shifted toward the center of the channel (away from the outer bank) along with the higher velocity flows. This change in flow, as well as the change in apparent turbulence at the bend apex, can be attributed to the presence of the submerged groynes.
