Scouring during high flow events has been hypothesized as a natural control of periphyton biomass, and designed pulsed flows have been suggested as management tools in regulated rivers. We created experimental, low-flow microhabitats to evaluate variability of scouring of algal biomass during a pulsed flow experiment in the Jackson River (Covington, VA), a regulated, nutrient-enriched river that experiences high algal biomass in late summer/fall.  During the pulsed flow experiment, discharge from Gathright Dam was increased from ~5 to ~31 m³/s and maintained at this discharge for ~16 hrs.  Prior to the pulse, randomly selected substrates were placed in areas of high velocity and behind artificially-created, low velocity refuges.  Algae samples were collected from substrates on each of 2 days prior to and following the pulsed flow (n=10/treatment/day).  Changes in chlorophyll a were analyzed using a Before-After/Control-Impact design ANOVA, treating substrates in flow refugia as controls, and high-velocity substrates as the impact.  Preliminary results suggest a reduction of algal material in the high velocity areas relative to flow refuges.  This study will increase statistical power in determining pulsed flow effects, and contribute to the development of a dam operation program for optimizing health in the Jackson River.