ABSTRACT
Fish baffle installation in HDPE slip lined road culverts is a popular method to reduce flows and promote fish passage. Though beneficial for fish, the insertion of baffles in culverts is known to reduce the hydraulic capacity of slip lined culverts causing increased water levels upstream and potentially the overtopping of the road. Previous studies have suggested that fish maneuver more easily through spoiler baffles than other more traditional baffle types (e.g., weir, slotted weir). Little is known concerning the extents to which spoiler baffles affect discharge capacity. To respond to this need, specific configurations of spoiler baffles were investigated in detail to determine how spacing/size (and inline vs staggered) configurations affect energy losses. Fine-scale spatial and temporal characterisation of the flow field around both inline and staggered baffles configurations was also performed using an acoustic Doppler velocimeter. Results reveal that hydraulic roughness decreases near linearly with increasing baffle spacing for all baffle configurations, reflective of isolated roughness flow. Baffle height was determined to be the dominant geometric parameter affecting roughness. The fine scale flow structure results indicate much similarity between inline and staggered baffles. Both configurations of baffles offer low refuges near the channel invert, yet the near wake of the baffles is characterized by high turbulence.
