Sediment loading rates from impervious surfaces studied by STEP were between 0.3 - 0.6 m³/ha/yr <ref>Goncalves, C., & Van Seters, T. (2012). Characterization of Particle Size Distributions of Runoff from High Impervious Urban Catchments in the Greater Toronto Area. Retrieved from https://sustainabletechnologies.ca/app/uploads/2013/03/PSD-2012-final.pdf</ref>. In Brisbane a value of 0.6 m³/ha/yr is the default value used to size small forebays <ref>Lal, R. (Ed.). (2006). “Particle Shape Effects” in “Particle Packing.” In Encyclopedia of Soil Science (p. 1248). New York: Taylor and Francis.</ref>.
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Sediment loading rates from impervious surfaces studied by STEP were between 0.3 - 0.6 m³/ha/yr <ref>Goncalves, C., & Van Seters, T. (2012). Characterization of Particle Size Distributions of Runoff from High Impervious Urban Catchments in the Greater Toronto Area. Retrieved from https://sustainabletechnologies.ca/app/uploads/2013/03/PSD-2012-final.pdf</ref>. In Brisbane a value of 0.6 m³/ha/yr is the default value used to size small forebays <refname = HW>Healthy Waterways Ltd. (2014). Bioretention Technical Design Guidelines. Retrieved from https://hlw.org.au/u/lib/mob/20150715140823_de4e60ebc5526e263/wbd_2014_bioretentiontdg_mq_online.pdf</ref>.
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2. The area of the forebay (''A<sub>f</sub>'') designed for 80 % capture efficiency (i.e. R = 0.8) may be estimated as:
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2. The area of the forebay (''A<sub>f</sub>'') designed for 80 % capture efficiency (i.e. R = 0.8) may be estimated</refname = HW> as: