4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Using WinSLAMM to Evaluate LID Practices
This workshop will start with a prepared WinSLAMM model file and add Low Impact
Development (LID) Practices to it. The two LID Practices that will be modeled are 1) Wet
Detention Pond with Water Reuse and 2) Biofiltration.
The project area is a 23.67 acre Industrial Development. Figures of the Development Source
Areas and LID practices can be found at the end of this document.
A No Management Condition Model file has been created for you. It is named “LID Example No
Management Condition.mdb”. The parameter files used for this example will be the same used
for the previous example and are listed below. The Pollutants to be analyzed are also the same
and are listed below.
Current File Data:
Site Description: “Calgary, AB LID Example, No Management Condition”
Seed: -42
Rain File: CO Denver Stapelton AP 4899.ran
Rain Start Date: 01/01/55
Rain End Date: 12/31/55
Winter Season Date Range: December 1st – March 31st
Pollutant Probability Distribution File: Central.ppdx
Runoff Coefficient File: v10 Central.rsv
Particulate Solids Concentration File: Central.pscx
Street Delivery Files:
Residential LU:
Central street Res and Other Urban.std
Industrial LU:
Central street Com Inst Indust.std
Institutional LU:
Central street Com Inst Indust.std
Other Urban LU:
Central street Res and Other Urban.std
Commercial LU:
Central street Com Inst Indust.std
Freeways:
Central Freeway.std
Pollutants:
Total Suspended Solids and Total Phosphorus will be analyzed in this workshop.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
LID Practices:
Approximately half of the site, which is facing away the street, will be routed to the Wet
Detention Pond, and the other half will be routed to the Biofiltration devices. The single
Industrial Land Use was split into two Industrial Land Use areas to represent the two drainage
areas. A table showing the Source Areas within the two drainage areas is shown below.
Project Source Areas
Source Area
Area
(acres)
Description
Directly connected?
Other needed
information
Away from Street
Roof
3.34
Paved Parking
6.95
Driveway
0.45
Sidewalk
0.14
Small Landscaped 1
0.66
Subtotal
Towards Street
11.54
Roof
2.51
Paved Parking
4.39
Driveway
1.81
Sidewalk 1
0.26
Sidewalk 2
0.26
Small Landscaped 1
2.90
Subtotal
Total
12.13
23.67
Flat Roof
Directly connected or draining
to a directly connected area
Directly connected or draining
to a directly connected area
Directly connected or draining
to a directly connected area
Directly connected or draining
to a directly connected area
Clayey soil; Medium or
High Density, No Alleys
Flat Roof
Directly connected or draining
to a directly connected area
Directly connected or draining
to a directly connected area
Directly connected or draining
to a directly connected area
Directly connected or draining
to a directly connected area
Draining to a Pervious Area
Clayey soil; Medium or
High Density, No Alleys
Clayey soil; Medium or
High Density, No Alleys
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Open the No Management Condition Model File.
Save the model file with a new name to represent the addition of the LID practices. Change the
site description.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Insert the Biofilter Icon downstream of the “Towards Street” Industrial Land Use and Insert the
Wet Detention Pond Icon downstream of the “Away from Street” Industrial Land Use.
To insert the Control Device Icon, either right click on the “Away from Street” Land Use Icon and
select “Disconnect” and right click on the “Towards Street” Land Use Icon and select
“Disconnect”.
Or, right-click on the Junction Icon and select “Disconnect”. If you select “Disconnect” at the
Junction Icon, it will disconnect all Icons attached to it.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
The Land Uses are now disconnected from the network.
If you elected to disconnect the Junction, then the Outfall Icon would also be disconnected from
the Junction Icon. If this is the case, you must re-connect them before you run the model.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Next, add the LID Practices. Click on the Wet Detention Pond Icon (WP) then click on the white
map space. Click on the Biofilter Icon (BF) then click on the white map space.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Then add junctions. Click on the Junction Icon, and then click on the white map space. A
junction is needed between every Land Use, Control Device, and Outfall.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Connect the network together by dragging the tail of each Icon to the Junction. Rearrange the
network as needed by dragging the Junctions or Icons.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Wet Detention Pond with Water Reuse
The Stage-Area data for the pond is shown below. There is a 5-foot deep, 0.22 acre permanent
pool. There is two feet of storage above the permanent pool. The pond side slopes are 4:1.
In the model, all stages are relative. The bottom stage and area of the pond is always zero.
Start the actual bottom stage of the pond at 0.01 feet.
Stage
(ft)
0.01
1.00
2.00
3.00
4.00
5.00
6.00
7.00
Area
(ac)
0.05
0.08
0.11
0.14
0.18
0.22
0.26
0.30
The Initial Stage is 5 feet. The Initial Stage indicates how full the pond is at the beginning of the
model run. It is usually equivalent to the permanent pool depth, but does not have to be.
The Cumulative Volume is for informational purposes only. Select the “Recalculate Cumulative
Volume” button whenever areas or stages are changes, or after you’ve entered the data for the
first time.
The outlet structures include:
• 6-inch pipe at the top of the permanent pool (Stage 5),
• 10-ft wide Emergency Spillway 6 inches below the top of the pond (Stage 6.5) and,
• Irrigation of 0.05 ac-ft per day from May 1st through September 30th.
The Wet Detention Pond form with the entered data is shown on the next page.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
The 0.22-acre permanent pool will be constructed in a landscaped area. Therefore, this is a
change of a source area from landscaped area to water.
To change the source area data, click on the “Away from Street” Land Use label. The Source
Area Grid for that land use will appear. Subtract 0.22 acres from the “Small Landscaped 1”
source area and add it to the “Water Body Area” source area.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Biofiltration
There are 20 Biofiltration Practices. For purposes of this workshop, we will enter the data for a
typical Biofiltration practice and model 20 of them.
The typical Biofiltration practice is 15-ft by 190-ft with a 5 foot buffer. There is 1-foot of gravel,
covered by 3-feet of engineered soil, with ¾-foot open area storage on top.
The engineered soil is 80% sand, 10% peat, and 10% compost.
The outlet structures include:
• Infiltration into the native soil,
• 6-inch underdrain, 6-inches from the bottom of the gravel
• 3-ft vertical standpipe, with the top 6-inches from the top of the practice
• 5-ft wide Emergency Spillway ¼-foot from the top of the practice
• Evapotranspiration (in/day)
Jan
0
Feb
0
Mar
0
Apr
0.07
May
0.17
Jun
0.23
Jul
0.37
Aug
0.35
Sep
0.26
Oct
0.12
Nov
0
Each Biofiltration Practice will be planted with 50% grasses, 25% prairie plants, and 25%
shrubs.
The Biofiltration form with the entered data is shown on the next page.
The Engineered Soil Media data form is shown on the subsequent page.
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Dec
0
4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Use the Detailed Media Characteristics form to calculate values describing the engineered soil
properties for Evapotranspiration.
The values calculated in the Media Data form will appear once an Engineered Media Depth is
entered and/or Evapotranspiration is selected as an outlet.
If some, or all, of the values are known, they can be entered in the “User-Defined Soil Type”
row. After the values have been determined, check the appropriate box(es) at the bottom of the
form to apply them to the program.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
Running the File:
Save the File and run it.
The practices are reducing the runoff volume by 59 percent and the Total Suspended Solids by
76 percent.
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4c – Using WinSLAMM to Evaluate LID Practices – Hands-on Workshop
The Control Practices tabs can be reviewed to determine the reduction each practice is
achieving.
Increasing Total Suspended Solids Reduction
If time, modify the control practices to achieve an 80 percent reduction of Total Suspended
Solids. The practice footprint cannot be increased; therefore, other characteristics will need to
be modified.
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Legend
Drainage Area
LID Model Example
Project Area
Ü
Legend
LID Model Example
Project Area
Drainage Area
Source Areas
Driveway
Landscape
Parking
Roof
Sidewalk
150
75
0
150 Feet
Ü
Legend
Drainage Areas
Biofilters
LID Model Example
Project Area
Wet Detention Pond
150
75
0
150 Feet