3.9.6 BIORETENTION - Visual OTTHYMO

Bioretention areas filter, detain and infiltrate stormwater runoff. Bioretention areas are known for their water quality, quantity and water balance benefits. The LID is designed with an engineered soil layer to store and treat runoff, a storage layer to detain larger volumes of water which then can infiltrate to surrounding native soil. Bioretention areas are designed with an overflow, optional subdrain, an outflow and a native soil infiltration rate. Key features for bioretention designs are shown in the diagram below.

Parameter Name	Description	Default Value
	Surface Area Ponding
DEPTH-AREA CURVE	Depth area curve for surface ponding area, depth is defined from the bottom of the ponding layer	–
	Mulch Layer
DEPTH	Depth of mulch layer (mm)	0.3
POROSITY	Fraction of soil that is made up of spaces (pores) between particles	0.4
	Engineered Soil Layer
SOIL MOISTURE	Initial soil moisture content of the engineered soil layer (fraction)	0.3
INFILTRATION	Rate with which water moves through porous material (m/hour)	0.5
POROSITY	Fraction of soil that is made up of spaces (pores) between particles	0.467
	Storage Layer
DEPTH	Depth of the storage layer (m)	1
POROSITY	Fraction of storage layer that is made up of spaces (pores) between particles	0.4

3.9.5 RAIN GARDEN

3.9.7 ENHANCED SWALES