In this North Carolina study, stream flow from three small, nonurban watersheds was compared with bioretention outflow from four cells in the same region. Results indicate that bioretention cells behave comparably to watersheds in natural or nonurban conditions with respect to both flow rates and flow volumes.
DeBusk, Kathy M., William F. Hunt, and Daniel E. Line. (2010). Bioretention outflow: Does it mimic nonurban watershed shallow interflow?. Journal of Hydrologic Engineering, 16(3), 274-279.