Changes

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 name ="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>.  

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 name ="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>.  

2. The area of the forebay (''A_f'') designed for 80 % capture efficiency (i.e. R = 0.8) may be estimated<ref name="HW"/> as:

2. a) To size a forebay for (''A_f'') 80 % capture efficiency of particles ≥ 1 mm may be estimated<ref name="HW"/> as:

:<math>A_{f}=120\times Q</math>

:<math>A_{f}=120\times Q</math>

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3. Check that the forebay depth (''d_f'', m) ≤ 0.3 m:

2. b) To size a forebay for a maximum depth (''d_f'', m), where d_f must ≤0.3 m and between 0.1 - 0.2 m is recommended:

: <math>d_{f}=\frac{V_{f}}{A_{f}}</math>

: <math>A_{f}=\frac{V_{f}}{d_{f}}</math>

 

===Example calculation===

===Example calculation===