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Little Topashaw Creek - Dye Study
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Slug injection of rhodamine dye at southern end of study reach

Advection of dye cloud retarded by debris structures

Dye concentration versus time measured at points marked with sun symbols on map

Map of study reach showing dye injection points as red arrows and sample collection points as sun symbols 
Effects of debris structures on flow were examined by running slug-injection tracer dye experiments on April 18, 2001. Two simultaneous experiments were conducted: one within the study reach, and one in the reach immediately downstream. The downstream reach had similar morphology, but no large woody debris structures had been added. Natural debris formations were present, but the overall debris density for the downstream reach was only about 5% of that for the reach with large woody debris structures.

Average flow-through velocity for the study reach was 0.17 m/s, while the unmodified downstream reach had an average velocity of 0.29 m/s. Ninety percent of the flow in the study reach had a velocity less than 0.22 m/s which compares with 0.36 m/s for the downstream reach.