InfoSWMM

#LID Defaults from the EPA SWC


#LID Defaults from the EPA SWC

The following defaults are from the EPA Stormwater Calculator

https://www.epa.gov/water-research/national-stormwater-calculator

A few of these parameters such as the capture ratio are not parameters in InfoSWMM Sustain

There are some additional points to keep in mind when applying LID controls to a site:

1. The area devoted to Disconnection, Rain Gardens, and Infiltration Basins is assumed to come from the site’s collective amount of pervious land cover while the area occupied by Green Roofs, Street Planters and Porous Pavement comes from the site’s store of impervious area.

2. Underdrains (slotted pipes placed in the gravel beds of Street Planter and Porous Pavement areas to prevent the unit from flooding) are not provided for. However since underdrains are typically oversized and placed at the top of the unit’s gravel bed, the effect on the amount of excess runoff flow bypassed by the unit is the same whether it flows out of the underdrain or simply runs off of a flooded surface.

3. The amount of void space in the soil, gravel, and pavement used in the LID controls are listed in Table 4 below. They typically have a narrow range of acceptable values and results are not terribly sensitive to variations within this range.

Table 3. Editable LID parameters.

LID Type Parameter Default Value
Disconnection Capture Ratio 100 %
Rain Harvesting Cistern Size 100 gal
Cistern Emptying Rate 50 gal/day
Number of Cisterns 4 per 1,000 sq ft
Rain Gardens Capture Ratio 5 %
Ponding Depth 6 inches
Soil Media Thickness 12 inches
Soil Media Conductivity 10 inches/hour
Green Roofs Soil Media Thickness 4 inches
Soil Media Conductivity 10 inches/hour
Street Planters Capture Ratio 6 %
Ponding Depth 6 inches
Soil Media Thickness 18 inches
Soil Media Conductivity 10 inches/hour
Gravel Bed Thickness 12 inches
Infiltration Basins Capture Ratio 5 %
Basin Depth 6 inches
Porous Pavement Capture Ratio 100 %
Pavement Thickness 4 inches
Gravel Bed Thickness 18 inches

Table 4. Void space values of LID media.

Property LID Controls Default Value
Soil Media Porosity Rain Gardens, Green Roofs and Street Planters 45 %
Gravel Bed Void Ratio Street Planters and Porous Pavement 75 %
Pavement Void Ratio Porous Pavement 12 %

Categories: InfoSWMM

Tagged as:

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s