10.2.5 Bioretention

A bioretention facility is a small-scale stormwater management practice that promotes infiltration of storm water to reduce its volume, improve its quality, and increase groundwater recharge. Bioretention systems contain four completely-mixed layers, including a layer of high permeability soil filtration media, covered by an optional thin layer of mulch, storage layer and native soil layer, and evapotranspiration, overflow, outflow, exfiltration to native soils and underdrain discharge would be accounted (see the figure below). The water balance equation for each layer is given as follows.

SCHEMATIC DIAGRAM OF A BIORETENTION FACILITY AND ITS HYDRAULIC PATTERN