Volume 2-05, Chapter 3 - City of Wichita

Section 3.2.9 - Bioretention Areas
3.2.9.1 General Description
Bioretention areas (also referred to as bioretention filters or rain gardens) are structural
stormwater controls that capture and temporarily store the WQ v using soils and vegetation in
shallow basins or landscaped areas to remove pollutants from stormwater runoff.
Bioretention areas are engineered facilities in which runoff is conveyed as sheet flow to the
“treatment area” which consists of a grass buffer strip, ponding area, organic or mulch layer,
planting soil, and vegetation. An optional sand or aggregate bed can also be included in the
design to provide aeration and drainage of the planting soil. The filtered runoff is typically
collected and returned to the conveyance system after detention, though it may infiltrate.
Because bioretention areas remove pollutants using filtration, they are applicable primarly to
impervious areas without high levels of fine particulates (clay/silt soils) in the runoff and should
only be considered for sites where the sediment load is relatively low.
There are numerous design applications, both on- and off-line, for bioretention areas. These
include use on single-family residential lots (rain gardens), as off-line facilities adjacent to
parking lots, along highway and road drainage swales, within larger landscaped pervious
areas, and as landscaped islands in impervious or high-density environments. Figure 3-33
and Figure 3-34 illustrate examples of bioretention facilities.
Residential Rain Garden
Landscaped Island
Newly Constructed Bioretention Area
Newly Planted Bioretention Area
Figure 3-33 Bioretention Area Examples
Page 3 - 112
Volume 2, Technical Guidance